bims-auttor 2023-12-31 papers

bims-auttor

Biomed News

on Autophagy and mTOR

Issue of 2023‒12‒31
33 papers selected by
Viktor Korolchuk, Newcastle University

New insight of the pathogenesis in osteoarthritis: the intricate interplay of ferroptosis and autophagy mediated by mitophagy/chaperone-mediated autophagy.
Lysophagy protects against propagation of α-synuclein aggregation through ruptured lysosomal vesicles.
PI3KCIIα-Dependent Autophagy Program Protects From Endothelial Dysfunction and Atherosclerosis in Response to Low Shear Stress in Mice.
Cholesterol Trafficking, Lysosomal Function and Atherosclerosis.
mTORC1 regulates the metabolic switch of postnatal cardiomyocytes during regeneration.
The role of mitochondrial dynamics in disease.
Regulatory mechanisms of autophagy-related ncRNAs in bone metabolic diseases.
A mitophagy sensor PPTC7 controls BNIP3 and NIX degradation to regulate mitochondrial mass.
The SLC38A9-mTOR axis is involved in autophagy in the juvenile yellow catfish (Pelteobagrus fulvidraco) under ammonia stress.
LOXL3 Inhibits Autophagy of Chondrocytes by Activating Rheb in Osteoarthritis.
Epigenetic targeting of autophagy for cancer: DNA and RNA methylation.
UBE3C tunes autophagy via ATG4B ubiquitination.
Ezrin inhibition alleviates oxidative stress and pyroptosis via regulating TRPML1-calcineurin axis mediated enhancement of autophagy in spinal cord injury.
Control of nuclear envelope dynamics during acute ER stress by LINC complexes disassembly and selective, asymmetric autophagy of the outer nuclear membrane.
The UFM1 system: Working principles, cellular functions, and pathophysiology.
CIRBP Increases the Synthesis and Secretion of Steroid Hormones by Activating Autophagy in Yak Granule Cells.
GNL3L promotes autophagy via regulating AMPK signaling in esophageal cancer cells.
Dynamic proximity interaction profiling suggests that YPEL2 is involved in cellular stress surveillance.
TRPML1 as a potential therapeutic target for triple-negative breast cancer: a review.
Starvation-induced autophagy modulates spermatogenesis and sperm quality in Nile tilapia.
PP2A inhibitor SET promotes mTORC1 and Bmi1 signaling through Akt activation and maintains the colony-formation ability of cancer cells.
Genome-wide and targeted CRISPR screens identify RNF213 as a mediator of interferon gamma-dependent pathogen restriction in human cells.
Inhibition of USP30 Promotes Mitophagy by Regulating Ubiquitination of MFN2 by Parkin to Attenuate Early Brain Injury After SAH.
Small G-Protein Rheb gates mTOR signaling to regulate morphine tolerance in mice.
Prohibitin 2: A key regulator of cell function.
The Chaperone Protein Cct5 is Essential for Hematopoietic Stem Cell Maintenance.
Temperature-Dependent Relationship of Autophagy and Apoptotic Signaling During Cold-Water Immersion in Young and Older Males.
Mitophagy Decreases in the Peripheral Vestibular System of Aged C57BL/6J Mice.
Long and Short-Term Effect of mTOR Regulation on Cerebral Organoid Growth and Differentiations.
Autophagy-modulating biomembrane nanostructures: A robust anticancer weapon by modulating the inner and outer cancer environment.
Lysosomal sialidase NEU1, its intracellular properties, deficiency, and use as a therapeutic agent.
Betaine attenuates age-related suppression in autophagy via Mettl21c/p97/VCP axis to delay muscle loss.
Solute carrier family 35 member A2 regulates mitophagy through the PI3K/AKT/mTOR axis, promoting the proliferation, migration, and invasion of osteosarcoma cells.

Front Cell Dev Biol. 2023 ;11 1297024

New insight of the pathogenesis in osteoarthritis: the intricate interplay of ferroptosis and autophagy mediated by mitophagy/chaperone-mediated autophagy.

Fangyu An, Jie Zhang, Peng Gao, Zhipan Xiao, Weirong Chang, Jiayi Song, Yujie Wang, Haizhen Ma, Rui Zhang, Zhendong Chen, Chunlu Yan.

  Ferroptosis, characterized by iron accumulation and lipid peroxidation, is a form of iron-driven cell death. Mitophagy is a type of selective autophagy, where degradation of damaged mitochondria is the key mechanism for maintaining mitochondrial homeostasis. Additionally, Chaperone-mediated autophagy (CMA) is a biological process that transports individual cytoplasmic proteins to lysosomes for degradation through companion molecules such as heat shock proteins. Research has demonstrated the involvement of ferroptosis, mitophagy, and CMA in the pathological progression of Osteoarthritis (OA). Furthermore, research has indicated a significant correlation between alterations in the expression of reactive oxygen species (ROS), adenosine monophosphate (AMP)-activated protein kinase (AMPK), and hypoxia-inducible factors (HIFs) and the occurrence of OA, particularly in relation to ferroptosis and mitophagy. In light of these findings, our study aims to assess the regulatory functions of ferroptosis and mitophagy/CMA in the pathogenesis of OA. Additionally, we propose a mechanism of crosstalk between ferroptosis and mitophagy, while also examining potential pharmacological interventions for targeted therapy in OA. Ultimately, our research endeavors to offer novel insights and directions for the prevention and treatment of OA.

Keywords:  adenosine monophosphate (AMP)-activated protein kinase (AMPK); chaperone-mediated autophagy; ferroptosis; hypoxia-inducible factors; mitophagy; osteoarthritis; reactive oxygen species

DOI:  https://doi.org/10.3389/fcell.2023.1297024
Proc Natl Acad Sci U S A. 2024 Jan 02. 121(1): e2312306120

Lysophagy protects against propagation of α-synuclein aggregation through ruptured lysosomal vesicles.

Keita Kakuda, Kensuke Ikenaka, Akiko Kuma, Junko Doi, César Aguirre, Nan Wang, Takahiro Ajiki, Chi-Jing Choong, Yasuyoshi Kimura, Shaymaa Mohamed Mohamed Badawy, Takayuki Shima, Shuhei Nakamura, Kousuke Baba, Seiichi Nagano, Yoshitaka Nagai, Tamotsu Yoshimori, Hideki Mochizuki.

  The neuron-to-neuron propagation of misfolded α-synuclein (αSyn) aggregates is thought to be key to the pathogenesis of synucleinopathies. Recent studies have shown that extracellular αSyn aggregates taken up by the endosomal-lysosomal system can rupture the lysosomal vesicular membrane; however, it remains unclear whether lysosomal rupture leads to the transmission of αSyn aggregation. Here, we applied cell-based αSyn propagation models to show that ruptured lysosomes are the pathway through which exogenous αSyn aggregates transmit aggregation, and furthermore, this process was prevented by lysophagy, i.e., selective autophagy of damaged lysosomes. αSyn aggregates accumulated predominantly in lysosomes, causing their rupture, and seeded the aggregation of endogenous αSyn, initially around damaged lysosomes. Exogenous αSyn aggregates induced the accumulation of LC3 on lysosomes. This LC3 accumulation was not observed in cells in which a key regulator of autophagy, RB1CC1/FIP200, was knocked out and was confirmed as lysophagy by transmission electron microscopy. Importantly, RB1CC1/FIP200-deficient cells treated with αSyn aggregates had increased numbers of ruptured lysosomes and enhanced propagation of αSyn aggregation. Furthermore, various types of lysosomal damage induced using lysosomotropic reagents, depletion of lysosomal enzymes, or more toxic species of αSyn fibrils also exacerbated the propagation of αSyn aggregation, and impaired lysophagy and lysosomal membrane damage synergistically enhanced propagation. These results indicate that lysophagy prevents exogenous αSyn aggregates from escaping the endosomal-lysosomal system and transmitting aggregation to endogenous cytosolic αSyn via ruptured lysosomal vesicles. Our findings suggest that the progression and severity of synucleinopathies are associated with damage to lysosomal membranes and impaired lysophagy.

Keywords:  lysophagy; lysosomal vesicle rupture; synucleinopathy; α-synuclein

DOI:  https://doi.org/10.1073/pnas.2312306120
Arterioscler Thromb Vasc Biol. 2023 Dec 28.

PI3KCIIα-Dependent Autophagy Program Protects From Endothelial Dysfunction and Atherosclerosis in Response to Low Shear Stress in Mice.

Mouin Nasr, Alexis Fay, Adrien Lupieri, Nicole Malet, Anne Darmon, Rana Zahreddine, Audrey Swiader, Amandine Wahart, Julien Viaud, Anne Nègre-Salvayre, Emilio Hirsch, Daniel Monteyne, David Perez-Morgà, Nicolas Dupont, Patrice Codogno, Damien Ramel, Etienne Morel, Muriel Laffargue, Stephanie Gayral.

BACKGROUND: The ability to respond to mechanical forces is a basic requirement for maintaining endothelial cell (ECs) homeostasis, which is continuously subjected to low shear stress (LSS) and high shear stress (HSS). In arteries, LSS and HSS have a differential impact on EC autophagy processes. However, it is still unclear whether LSS and HSS differently tune unique autophagic machinery or trigger specific autophagic responses in ECs.METHODS: Using fluid flow system to generate forces on EC and multiscale imaging analyses on ApoE-/- mice whole arteries, we studied the cellular and molecular mechanism involved in autophagic response to LSS or HSS on the endothelium.
RESULTS: We found that LSS and HSS trigger autophagy activation by mobilizing specific autophagic signaling modules. Indeed, LSS-induced autophagy in endothelium was independent of the class III PI3K (phosphoinositide 3-kinase) VPS34 (vacuolar sorting protein 34) but controlled by the α isoform of class II PI3K (phosphoinositide 3-kinase class II α [PI3KCIIα]). Accordingly, reduced PI3KCIIα expression in ApoE-/- mice (ApoE-/-PI3KCIIα+/-) led to EC dysfunctions associated with increased plaque deposition in the LSS regions. Mechanistically, we revealed that PI3KCIIα inhibits mTORC1 (mammalian target of rapamycin complex 1) activation and that rapamycin treatment in ApoE-/-PI3KCIIα+/- mice specifically rescue autophagy in arterial LSS regions. Finally, we demonstrated that absence of PI3KCIIα led to decreased endothelial primary cilium biogenesis in response to LSS and that ablation of primary cilium mimics PI3KCIIα-decreased expression in EC dysfunction, suggesting that this organelle could be the mechanosensor linking PI3KCIIα and EC homeostasis.
CONCLUSIONS: Our data reveal that mechanical forces variability within the arterial system determines EC autophagic response and supports a central role of PI3KCIIα/mTORC1 axis to prevent EC dysfunction in LSS regions.

DOI: https://doi.org/10.1161/ATVBAHA.123.319978
Am J Physiol Cell Physiol. 2023 Dec 25.

Cholesterol Trafficking, Lysosomal Function and Atherosclerosis.

Alaa Skeyni, Alain Pradignac, Rachel L Matz, Jerome Terrand, Phillippe Boucher.

  Despite years of study and major research advances over the past 50 years, atherosclerotic diseases continue to rank as the leading global cause of death. Accumulation of cholesterol within the vascular wall remained the main problem and represented one of the early steps in the development of atherosclerotic lesions. There is a complex relationship between vesicular cholesterol transport and atherosclerosis, and abnormalities in cholesterol trafficking can contribute to the development and progression of the lesions. The dysregulation of vesicular cholesterol transport and lysosomal function fosters the buildup of cholesterol within various intracytoplasmic compartments, including lysosomes and lipid droplets. This, in turn, promotes the hallmark formation of foam cells, a defining feature of early atherosclerosis. Multiple cellular processes, encompassing endocytosis, exocytosis, intracellular trafficking, and autophagy, play crucial roles in influencing foam cell formation and atherosclerotic plaque stability. In this review, we will highlight recent advances in the understanding of the intricate mechanisms of vesicular cholesterol transport and its relationship with atherosclerosis, and will discuss the importance of understanding these mechanisms in developing strategies to prevent or treat this prevalent cardiovascular disease.

Keywords:  Lysosome; autophagy; interorganellar communications; mTORC1; metabolism

DOI:  https://doi.org/10.1152/ajpcell.00415.2023
J Mol Cell Cardiol. 2023 Dec 22. pii: S0022-2828(23)00198-0. [Epub ahead of print]187 15-25

mTORC1 regulates the metabolic switch of postnatal cardiomyocytes during regeneration.

Wyatt G Paltzer, Timothy J Aballo, Jiyoung Bae, Corey G K Flynn, Kayla N Wanless, Katharine A Hubert, Dakota J Nuttall, Cassidy Perry, Raya Nahlawi, Ying Ge, Ahmed I Mahmoud.

  The metabolic switch from glycolysis to fatty acid oxidation in postnatal cardiomyocytes contributes to the loss of the cardiac regenerative potential of the mammalian heart. However, the mechanisms that regulate this metabolic switch remain unclear. The protein kinase complex mechanistic target of rapamycin complex 1 (mTORC1) is a central signaling hub that regulates cellular metabolism and protein synthesis, yet its role during mammalian heart regeneration and postnatal metabolic maturation is undefined. Here, we use immunoblotting, rapamycin treatment, myocardial infarction, and global proteomics to define the role of mTORC1 in postnatal heart development and regeneration. Our results demonstrate that the activity of mTORC1 is dynamically regulated between the regenerating and the non-regenerating hearts. Acute inhibition of mTORC1 by rapamycin or everolimus reduces cardiomyocyte proliferation and inhibits neonatal heart regeneration following injury. Our quantitative proteomic analysis demonstrates that transient inhibition of mTORC1 during neonatal heart injury did not reduce protein synthesis, but rather shifts the cardiac proteome of the neonatal injured heart from glycolysis towards fatty acid oxidation. This indicates that mTORC1 inhibition following injury accelerates the postnatal metabolic switch, which promotes metabolic maturation and impedes cardiomyocyte proliferation and heart regeneration. Taken together, our results define an important role for mTORC1 in regulating postnatal cardiac metabolism and may represent a novel target to modulate cardiac metabolism and promote heart regeneration.

Keywords:  Cardiomyocyte proliferation; Heart regeneration; Mechanistic target of rapamycin complex 1; Metabolism; Proteomics

DOI:  https://doi.org/10.1016/j.yjmcc.2023.12.004
MedComm (2020). 2023 Dec;4(6): e462

The role of mitochondrial dynamics in disease.

Yujuan Wang, Xinyan Dai, Hui Li, Huiling Jiang, Junfu Zhou, Shiying Zhang, Jiacheng Guo, Lidu Shen, Huantao Yang, Jie Lin, Hengxiu Yan.

  Mitochondria are multifaceted and dynamic organelles regulating various important cellular processes from signal transduction to determining cell fate. As dynamic properties of mitochondria, fusion and fission accompanied with mitophagy, undergo constant changes in number and morphology to sustain mitochondrial homeostasis in response to cell context changes. Thus, the dysregulation of mitochondrial dynamics and mitophagy is unsurprisingly related with various diseases, but the unclear underlying mechanism hinders their clinical application. In this review, we summarize the recent developments in the molecular mechanism of mitochondrial dynamics and mitophagy, particularly the different roles of key components in mitochondrial dynamics in different context. We also summarize the roles of mitochondrial dynamics and target treatment in diseases related to the cardiovascular system, nervous system, respiratory system, and tumor cell metabolism demanding high-energy. In these diseases, it is common that excessive mitochondrial fission is dominant and accompanied by impaired fusion and mitophagy. But there have been many conflicting findings about them recently, which are specifically highlighted in this view. We look forward that these findings will help broaden our understanding of the roles of the mitochondrial dynamics in diseases and will be beneficial to the discovery of novel selective therapeutic targets.

Keywords:  context; disease; mitochondrial dynamics; mitophagy; target treatment

DOI:  https://doi.org/10.1002/mco2.462
Front Pharmacol. 2023 ;14 1178310

Regulatory mechanisms of autophagy-related ncRNAs in bone metabolic diseases.

Binghan Yan, Zhichao Li, Hui Su, Haipeng Xue, Daodi Qiu, Zhanwang Xu, Guoqing Tan.

  Bone metabolic diseases have been tormented and are plaguing people worldwide due to the lack of effective and thorough medical interventions and the poor understanding of their pathogenesis. Non-coding RNAs (ncRNAs) are heterogeneous transcripts that cannot encode the proteins but can affect the expressions of other genes. Autophagy is a fundamental mechanism for keeping cell viability, recycling cellular contents through the lysosomal pathway, and maintaining the homeostasis of the intracellular environment. There is growing evidence that ncRNAs, autophagy, and crosstalk between ncRNAs and autophagy play complex roles in progression of metabolic bone disease. This review investigated the complex mechanisms by which ncRNAs, mainly micro RNAs (miRNAs), long noncoding RNAs (lncRNAs), and circular RNAs (circRNAs), regulate autophagic pathway to assist in treating bone metabolism disorders. It aimed at identifying the autophagy role in bone metabolism disorders and understanding the role, potential, and challenges of crosstalk between ncRNAs and autophagy for bone metabolism disorders treatment.

Keywords:  autophagy; bone metabolism; ncRNAs; osteoarthritis; osteoporosis; rheumatoid arthritis

DOI:  https://doi.org/10.3389/fphar.2023.1178310
Mol Cell. 2023 Dec 21. pii: S1097-2765(23)01014-6. [Epub ahead of print]

A mitophagy sensor PPTC7 controls BNIP3 and NIX degradation to regulate mitochondrial mass.

Yuqiu Sun, Yu Cao, Huayun Wan, Adalet Memetimin, Yang Cao, Lin Li, Chongyang Wu, Meng Wang, She Chen, Qi Li, Yan Ma, Mengqiu Dong, Hui Jiang.

  Mitophagy mediated by BNIP3 and NIX critically regulates mitochondrial mass. Cellular BNIP3 and NIX levels are tightly controlled by SCFFBXL4-mediated ubiquitination to prevent excessive mitochondrial loss and lethal disease. Here, we report that knockout of PPTC7, a mitochondrial matrix protein, hyperactivates BNIP3-/NIX-mediated mitophagy and causes perinatal lethality that is rescued by NIX knockout in mice. Biochemically, the PPTC7 precursor is trapped by BNIP3 and NIX to the mitochondrial outer membrane, where PPTC7 scaffolds assembly of a substrate-PPTC7-SCFFBXL4 holocomplex to degrade BNIP3 and NIX, forming a homeostatic regulatory loop. PPTC7 possesses an unusually weak mitochondrial targeting sequence to facilitate its outer membrane retention and mitophagy control. Starvation upregulates PPPTC7 expression in mouse liver to repress mitophagy, which critically maintains hepatic mitochondrial mass, bioenergetics, and gluconeogenesis. Collectively, PPTC7 functions as a mitophagy sensor that integrates homeostatic and physiological signals to dynamically control BNIP3 and NIX degradation, thereby maintaining mitochondrial mass and cellular homeostasis.

Keywords:  Cullin; FBXL4; PPTC7; metabolism; mitochondrial mass; mitophagy receptors BNIP3 and NIX; ubiquitin

DOI:  https://doi.org/10.1016/j.molcel.2023.11.038
Environ Pollut. 2023 Dec 22. pii: S0269-7491(23)02213-3. [Epub ahead of print]343 123211

The SLC38A9-mTOR axis is involved in autophagy in the juvenile yellow catfish (Pelteobagrus fulvidraco) under ammonia stress.

Xue Li, Shidong Wang, Muzi Zhang, Ming Li.

  The primary objective of this study was to examine the effect of acute ammonia stress on hepatic physiological alterations in yellow catfish by performing a comprehensive analysis of the metabolome and transcriptome. The present study showed that ammonia stress led to liver metabolic disruption, functional incapacitation, and oxidative damage. Transcriptomic and metabolomic analyses revealed transcriptional and metabolic differences in the liver of yellow catfish under control and high ammonia stress conditions. After 96 h of acute exposure to ammonia, the mRNA levels of 596 liver genes were upregulated, whereas those of 603 genes were downregulated. Enrichment analysis of the differentially expressed genes identified multiple signalling pathways associated with autophagy, including the endocytosis, autophagy-animal, and mammalian target of rapamycin signalling pathways. A total of 186 upregulated and 117 downregulated metabolites, primarily associated with amino acid biosynthesis pathways, were identified. Multi-omics integration revealed the solute carrier family 38 member 9 (SLC38A9)-mammalian target of rapamycin axis as a signalling nexus for amino acid-mediated modulation of autophagy flux, and q-PCR was used to assess the expression of autophagy-related genes (LC3a and sqstm1), revealing an initial inhibition followed by the restoration of autophagic flux during ammonia stress. Subsequent utilisation of arginine as a specific SLC38A9 activator during ammonia stress demonstrated that augmented SLC38A9 expression hindered autophagy, exacerbated ammonia toxicity, and caused a physiological decline (total cholesterol, total triglyceride, acid phosphatase, alkaline phosphatase, aspartate aminotransferase, and alanine aminotransferase levels were significantly increased), oxidative stress, and apoptosis. Autophagy activation may be an adaptive mechanism to resist ammonia stress.

Keywords:  Amino acids; Ammonia stress; Ammonia tolerance; Autophagy; SLC38A9; mTOR

DOI:  https://doi.org/10.1016/j.envpol.2023.123211
Curr Med Sci. 2023 Dec;43(6): 1195-1200

LOXL3 Inhibits Autophagy of Chondrocytes by Activating Rheb in Osteoarthritis.

Guang-Ping Zheng, Chen Liu, Liang Zhang, Qiang Zhong, Yun Zhang, Zhong-Ming Huang.

  OBJECTIVE: This study aimed to investigate the potential mechanisms by which lysyl oxidase like 3 (LOXL3) affects the autophagy in chondrocytes in osteoarthritis (OA), specifically through the activation of mammalian target of rapamycin complex 1 (mTORC1).METHODS: To establish an OA model, rats underwent anterior cruciate ligament transection (ACLT). Chondrocytes were isolated from cartilage tissues and cultured. Western blotting was performed to assess the expression of LOXL3, Rheb, phosphorylation of p70S6K (p-p70S6K, a downstream marker of mTORC1), and autophagy markers. The autophagy of chondrocytes was observed using an immunofluorescence assay.
RESULTS: The expression levels of both LOXL3 and Rheb proteins were upregulated in chondrocytes isolated from the OA model cartilage, in comparison to those from the normal cartilage. The silencing of LOXL3 resulted in a decrease in the protein levels of Rheb and p-p70S6K, as well as an increase in the expression of autophagy-related proteins. Additionally, the effect of LOXL3 could be reversed through the silencing of Rheb. The results of the immunofluorescence assay confirmed the impact of LOXL3 and Rheb on chondrocyte autophagy.
CONCLUSION: LOXL3 inhibits chondrocyte autophagy by activating the Rheb and mTORC1 signaling pathways.

Keywords:  LOXL3; Rheb; autophagy; chondrocyte; mTORC1; osteoarthritis

DOI:  https://doi.org/10.1007/s11596-023-2820-8
Front Oncol. 2023 ;13 1290330

Epigenetic targeting of autophagy for cancer: DNA and RNA methylation.

Luobin Lin, Yuntao Zhao, Qinzhou Zheng, Jiayang Zhang, Huaqin Li, Wenmei Wu.

  Autophagy, a crucial cellular mechanism responsible for degradation and recycling of intracellular components, is modulated by an intricate network of molecular signals. Its paradoxical involvement in oncogenesis, acting as both a tumor suppressor and promoter, has been underscored in recent studies. Central to this regulatory network are the epigenetic modifications of DNA and RNA methylation, notably the presence of N6-methyldeoxyadenosine (6mA) in genomic DNA and N6-methyladenosine (m6A) in eukaryotic mRNA. The 6mA modification in genomic DNA adds an extra dimension of epigenetic regulation, potentially impacting the transcriptional dynamics of genes linked to autophagy and, especially, cancer. Conversely, m6A modification, governed by methyltransferases and demethylases, influences mRNA stability, processing, and translation, affecting genes central to autophagic pathways. As we delve deeper into the complexities of autophagy regulation, the importance of these methylation modifications grows more evident. The interplay of 6mA, m6A, and autophagy points to a layered regulatory mechanism, illuminating cellular reactions to a range of conditions. This review delves into the nexus between DNA 6mA and RNA m6A methylation and their influence on autophagy in cancer contexts. By closely examining these epigenetic markers, we underscore their promise as therapeutic avenues, suggesting novel approaches for cancer intervention through autophagy modulation.

Keywords:  6mA methylation; autophagy; cancers; m6A methylation; therapy

DOI:  https://doi.org/10.3389/fonc.2023.1290330
Autophagy. 2023 Dec 26.

UBE3C tunes autophagy via ATG4B ubiquitination.

Chaonan Sun, Yuxin Chen, Qianqian Gu, Yuanyuan Fu, Yao Wang, Cui Liu, Huazhong Xie, Yong Liao, Zhihua Zheng, Peiqing Liu, Min Li.

  ATG4B is a core protein and essential for cleaving precursor MAP1LC3/LC3 or deconjugating lipidated LC3-II to drive the formation of autophagosomes. The protein stability and activity of ATG4B regulated by post-translational modification (ubiquitination) will directly affect macroautophagy/autophagy. However, the mechanism involved in ATG4B ubiquitination is largely unclear. In this study, a new E3 ligase of ATG4B, UBE3C, was identified by mass spectra. UBE3C mainly assembles K33-branched ubiquitin chains on ATG4B at Lys119 without causing ATG4B degradation. In addition, the increased ubiquitination of ATG4B caused by UBE3C overexpression inhibits autophagy flux in both normal and starvation conditions, which might be due to the reduced activity of ATG4B and ATG4B-LC3 interaction. This reduction could be reversed once the lysine 119 of ATG4B was mutated to arginine. More important, under starvation conditions the interaction between ATG4B and UBE3C apparently decreased followed by the removal of the K33-branched ubiquitin chain of ATG4B. Thus, starvation-induced autophagy could be partially suppressed by an increased ubiquitination level of ATG4B. In conclusion, our research reveals a novel modification mode of ATG4B in which UBE3C can fine tune ATG4B activity by specific ubiquitination regulating autophagy without causing ATG4B degradation.

Keywords:  ATG4B; UBE3C; autophagy; ubiquitination

DOI:  https://doi.org/10.1080/15548627.2023.2299514
Free Radic Biol Med. 2023 Dec 22. pii: S0891-5849(23)01176-0. [Epub ahead of print]

Ezrin inhibition alleviates oxidative stress and pyroptosis via regulating TRPML1-calcineurin axis mediated enhancement of autophagy in spinal cord injury.

Junsheng Lou, Mengran Jin, Conghui Zhou, Yunpeng Fan, Libin Ni, Yiting Mao, Honghao Shen, Jiafeng Li, Haojie Zhang, Chunyan Fu, Xingjia Mao, Yingying Chen, Jinjie Zhong, Kailiang Zhou, Linlin Wang, Junsong Wu.

  Spinal cord injury (SCI) presents profound ramifications for patients, leading to diminished motor and sensory capabilities distal to the lesion site. Once SCI occurs, it not only causes great physical and psychological problems for patients but also imposes a heavy economic burden. Ezrin is involved in various cellular processes, including signal transduction, cell death, inflammation, chemotherapy resistance and the stress response. However, whether Ezrin regulates functional repair after SCI and its underlying mechanism has not been elucidated. Here, our results showed that there is a marked augmentation of Ezrin levels within neurons and Ezrin inhibition markedly diminished glial scarring and bolstered functional recuperation after SCI. RNA sequencing indicated the potential involvement of pyroptosis, oxidative stress and autophagy in the enhancement of functional recovery upon reduced Ezrin expression. Moreover, the inhibition of Ezrin expression curtailed pyroptosis and oxidative stress by amplifying autophagy. Our studies further demonstrated that Ezrin inhibition promoted autophagy by increasing TFEB activity via the Akt-TRPML1-calcineurin pathway. Finally, we concluded that inhibiting Ezrin expression alleviates pyroptosis and oxidative stress by enhancing TFEB-driven autophagy, thereby promoting functional recovery after SCI, which may be a promising therapeutic target for SCI treatment.

Keywords:  Autophagy; Ezrin; Oxidative stress; Pyroptosis; Spinal cord injury; TFEB

DOI:  https://doi.org/10.1016/j.freeradbiomed.2023.12.020
Autophagy. 2023 Dec 28.

Control of nuclear envelope dynamics during acute ER stress by LINC complexes disassembly and selective, asymmetric autophagy of the outer nuclear membrane.

Marika K Kucińska, Maurizio Molinari.

  The endoplasmic reticulum (ER) extends to the outer (ONM) and the inner (INM) nuclear membrane forming the nuclear envelope (NE) that delimits the nucleoplasm containing the cell genome. Unfolded protein responses (UPRs) and reticulophagy responses increase or reduce ER size and activities, respectively. If dynamic changes of the ER are transmitted to the contiguous NE was not known. In our recent publication, we report on the transmission of stress-induced ER expansion to the NE, which requires disassembly of the Linker of Nucleoskeleton and Cytoskeleton (LINC) complexes deputed to ensure a physical connection between the cytoplasmic cytoskeleton and the nuclear lamina and to maintain the width between INM and ONM within 50 nm. LINC complexes disassembly relies on reduction of the disulfide bond that covalently links SUN proteins in the INM and KASH proteins (SYNE/NESPRIN proteins in mammals) in the ONM by the ONM-resident reductase TMX4. Upon stress resolution, the physiological shape of the NE is re-established by SEC62-driven ONM-phagy, where ONM-derived vesicles are directly captured by RAB7- and LAMP1-positive endolysosomes in processes that proceed via asymmetric microautophagy of the NE.

Keywords:  ER-phagy; ONM-phagy

DOI:  https://doi.org/10.1080/15548627.2023.2299123
Mol Cell. 2023 Dec 20. pii: S1097-2765(23)00979-6. [Epub ahead of print]

The UFM1 system: Working principles, cellular functions, and pathophysiology.

Masaaki Komatsu, Toshifumi Inada, Nobuo N Noda.

  Ubiquitin-fold modifier 1 (UFM1) is a ubiquitin-like protein covalently conjugated with intracellular proteins through UFMylation, a process similar to ubiquitylation. Growing lines of evidence regarding not only the structural basis of the components essential for UFMylation but also their biological properties shed light on crucial roles of the UFM1 system in the endoplasmic reticulum (ER), such as ER-phagy and ribosome-associated quality control at the ER, although there are some functions unrelated to the ER. Mouse genetics studies also revealed the indispensable roles of this system in hematopoiesis, liver development, neurogenesis, and chondrogenesis. Of critical importance, mutations of genes encoding core components of the UFM1 system in humans cause hereditary developmental epileptic encephalopathy and Schohat-type osteochondrodysplasia of the epiphysis. Here, we provide a multidisciplinary review of our current understanding of the mechanisms and cellular functions of the UFM1 system as well as its pathophysiological roles, and discuss issues that require resolution.

Keywords:  ER-RQC; ER-phagy; autophagy; endoplasmic reticulum; ribosome-associated quality control; the UFM1 system; ubiquitin-like conjugation system

DOI:  https://doi.org/10.1016/j.molcel.2023.11.034
J Steroid Biochem Mol Biol. 2023 Dec 22. pii: S0960-0760(23)00205-4. [Epub ahead of print] 106449

CIRBP Increases the Synthesis and Secretion of Steroid Hormones by Activating Autophagy in Yak Granule Cells.

Rui Zhang, Yangyang Pan, Meng Wang, Jinglei Wang, TongXiang Zhang, Ling Zhao, Ruihua Xu, Yaying Wang, Xiaohong Han, Xiaolin Ye, Yan Cui, Sijiu Yu.

  As a regulatory protein that upregulates transcription in response to various stresses, cold-induced RNA-binding protein (CIRBP) is involved in a variety of physiological pathological processes in cells. However, little is known about the role of CIRBP in regulating autophagy and the synthesis and secretion of ovarian steroid hormones (estradiol E2 and progesterone P4). This study aimed to explore whether the synthetic secretion of ovarian steroid hormones is related to CIRBP-regulated autophagy. We detected the differential expression of CIRBP, LC3, E2 and P4 in YGCs cultured at mild low temperature (32 °C) for 6 and 12h. CIRBP, LC3, E2 and P4 expression was increased in response to low temperature in YGCs. In order to illustrate that the changes in secretion of E2/P4 and autophagy might be caused by CIRBP induced by low temperature, we overexpressed CIRBP in YGCs cultured in vitro to detect its effects on autophagy and steroid hormone synthesis and secretion. We found that overexpression of CIRBP can induce autophagy of YGCs and enhance the synthesis and secretion of E2 and P4, suggesting that mild hypothermia may activate autophagy by inducing the expression of CIRBP and enhance the synthesis and secretion of E2 and P4. To further explore the relationship between CIRBP regulated autophagy and steroid hormone synthesis and secretion, we verified it by regulating autophagy. The results showed that Inhibition of autophagy significantly reversed CIRBP overexpression-enhanced autophagy and synthetic secretion of E2, P4 in YGCs, while activated autophagy showed similar results to overexpression of CIRBP. In conclusion, our data suggest that autophagy is involved in the synthesis and secretion of YGCs E2 and P4 and is associated with overexpression of CIRBP.

Keywords:  CIRBP; autophagy; granule cells; ovarian steroid hormones

DOI:  https://doi.org/10.1016/j.jsbmb.2023.106449
Med Oncol. 2023 Dec 26. 41(1): 29

GNL3L promotes autophagy via regulating AMPK signaling in esophageal cancer cells.

Weiting He, Fengyao Sun, Wen Li, Ruihang Du, Siyuan Yan, Changqing Liu.

  Guanine nucleotide-binding protein-like 3-like (GNL3L), a conserved GTP-binding nucleolar protein, participates in regulating cell proliferation, and associates with tumorigenesis and poor prognosis in several kind of cancers. However, the role of GNL3L in modulating autophagy remains unclear. Here, we verified that GNL3L was higher expressed in esophageal cancer (ESCA) biopsies than that in the corresponding normal biopsies by a human ESCA tissue array. Utilizing immunoblotting and real-time PCR assays, we analyzed the expression of GNL3L in several ESCA cell lines, and it was highly expressed in KYSE410 cells and rarely expressed in KYSE150 cells, respectively. GNL3L overexpression promoted cell viability and cell proliferation in KYSE150 cells. On the contrary, silencing of GNL3L resulted in opposite phenotypes in KYSE410 cells. Furthermore, GNL3L level correlated with autophagic flux and influenced the levels of autophagy core proteins. Meanwhile, GNL3L also affected the AMPK signaling pathway, which is a pivotal signaling pathway for autophagy regulation. In the GNL3L-silenced cells, the AMPK agonist AICAR partly rescued the autophagic flux. Inversely, both pharmacologically and genetically deprivation of AMPK attenuated the autophagic flux induced by GNL3L overexpression. Moreover, AMPK activity alteration influenced the effect of GNL3L in regulating cell proliferation. Collectively, these findings suggest that GNL3L positively regulates cell proliferation and autophagy in ESCA cells via regulating the AMPK signaling, making itself a promising therapeutic target for ESCA.

Keywords:  AMPK signaling; Autophagy; Esophageal cancer; GNL3L; Proliferation

DOI:  https://doi.org/10.1007/s12032-023-02270-9
Protein Sci. 2023 Dec 25. e4859

Dynamic proximity interaction profiling suggests that YPEL2 is involved in cellular stress surveillance.

Gizem Turan, Çağla Ece Olgun, Hazal Ayten, Pelin Toker, Annageldi Ashyralyyev, Büşra Savaş, Ezgi Karaca, Mesut Muyan.

  YPEL2 is a member of the evolutionarily conserved YPEL family involved in cellular proliferation, mobility, differentiation, senescence, and death. However, the mechanism by which YPEL2, or YPEL proteins, mediates its effects is largely unknown. Proteins perform their functions in a network of proteins whose identities, amounts, and compositions change spatiotemporally in a lineage-specific manner in response to internal and external stimuli. Here, we explored interaction partners of YPEL2 by using dynamic TurboID-coupled mass spectrometry analyses to infer a function for the protein. Our results using inducible transgene expressions in COS7 cells indicate that proximity interaction partners of YPEL2 are mainly involved in RNA and mRNA metabolic processes, ribonucleoprotein complex biogenesis, regulation of gene silencing by miRNA, and cellular responses to stress. We showed that YPEL2 interacts with the RNA-binding protein ELAVL1 and the selective autophagy receptor SQSTM1. We also found that YPEL2 localizes stress granules in response to sodium arsenite, an oxidative stress inducer, which suggests that YPEL2 participates in stress granule-related processes. Establishing a point of departure in the delineation of structural/functional features of YPEL2, our results suggest that YPEL2 may be involved in stress surveillance mechanisms. This article is protected by copyright. All rights reserved.

Keywords:  ELAVL1; Proximity Interactions; SQSTM1; TurboID; YPEL2

DOI:  https://doi.org/10.1002/pro.4859
Front Oncol. 2023 ;13 1326023

TRPML1 as a potential therapeutic target for triple-negative breast cancer: a review.

Ying Pan, Qiancheng Zhao, Haitao He, Yubo Qi, Yujie Bai, Jia Zhao, Yiming Yang.

  Triple-negative breast cancer (TNBC) is the most refractory subtype of breast cancer, and effective treatments are urgently needed owing to its poor prognosis. Surgery, radiotherapy, and chemotherapy, alone or in combination, are the leading choices for TNBC therapy. Although promising approaches and procedures have emerged, several challenges, such as off-target effects, drug resistance, and severe side effects, remain to be addressed. Recently, transient receptor potential channel mucolipin 1 (TRPML1) has attracted the attention of researchers because its expression has been implicated in numerous diseases, including cancer. TRPML1 regulates biological events and signaling pathways, including autophagic flux, exocytosis, ionic homeostasis, and lysosomal biogenesis, all contributing to tumorigenesis and cancer progression. TRPML1 also functions as a building block for cancer cell growth, mitogenic signaling, priming tissues for metastasis, and activation of transcriptional programs, processes involved in several malignant tumors. This review provides an overview of breast cancer epidemiology and diagnostic techniques and then discusses the existing therapeutics. Additionally, we elaborate on the development of, and associated challenges to, TNBC diagnostics and treatment and the feasibility of TRPML1 as a therapeutic target for TNBC.

Keywords:  TRPML1; autophagy; cancer treatment; therapeutic target; triple-negative breast cancer

DOI:  https://doi.org/10.3389/fonc.2023.1326023
Theriogenology. 2023 Dec 12. pii: S0093-691X(23)00473-9. [Epub ahead of print]216 42-52

Starvation-induced autophagy modulates spermatogenesis and sperm quality in Nile tilapia.

Camila Ferreira Sales, Ana Paula Barbosa Pinheiro, Yves Moreira Ribeiro, Davidson Peruci Moreira, Ronald Kennedy Luz, Rafael Magno Costa Melo, Elizete Rizzo.

  Spermatogenesis is a finely regulated process that involves the interaction of several cellular mechanisms to ensure the proper development and maturation of germ cells. This study assessed autophagy contribution and its relation to apoptosis in fish spermatogenesis during starvation. To that end, Nile tilapia males were subjected to 0 (control), 7, 14, 21, and 28 days of starvation to induce autophagy. Testes samples were obtained for analyses of spermatogenesis by histology, electron microscopy, immunohistochemistry, and western blotting. Sperm quality was assessed using a computer-assisted sperm analysis (CASA) system. Data indicated a significant reduction in gonadosomatic index, seminiferous tubule area, and spermatozoa proportion in fish subject to starvation compared to the control group. Immunoblotting revealed a reduction of Bcl2 and Beclin 1 associated with increased Bax and Caspase-3, mainly after 21 and 28 days of starvation. LC3 and P62 indicated reduced autophagic flux in these starvation times. Immunolabeling for autophagic and apoptotic proteins occurred in all development stages of the germ cells, but protein expression varied throughout starvation. Beclin 1 and Cathepsin D decreased while Bax and Caspase-3 increased in spermatocytes, spermatids, and spermatozoa after 21 and 28 days. Autophagic and lysosomal proteins colocalization indicated the fusion of autophagosomes with lysosomes and lysosomal degradation in spermatogenic cells. The CASA system indicated reduced sperm motility and velocity in animals subjected to 21 and 28 days of starvation. Altogether, the data support autophagy acting at different spermatogenesis stages in Nile tilapia, with decreased autophagy and increased apoptosis after 21 and 28 days of starvation, which results in a decrease in the spermatozoa number and sperm quality.

Keywords:  Autophagosome; Bax; Beclin-1; Caspase-3; LC3; Sperm motility

DOI:  https://doi.org/10.1016/j.theriogenology.2023.11.030
J Biol Chem. 2023 Dec 21. pii: S0021-9258(23)02612-1. [Epub ahead of print] 105584

PP2A inhibitor SET promotes mTORC1 and Bmi1 signaling through Akt activation and maintains the colony-formation ability of cancer cells.

Naoki Kohyanagi, Nao Kitamura, Shunta Ikeda, Shusaku Shibutani, Koichi Sato, Takashi Ohama.

  Protein phosphatase 2A (PP2A) is an essential tumor suppressor, and its activity is suppressed in cancer cells by endogenous PP2A inhibitory proteins such as SE translocation (SET). SET/PP2A axis plays a pivotal role in the colony-formation ability of cancer cells, and the stabilization of c-Myc and E2F1 proteins are involved in this. However, in osteosarcoma cell line HOS, SET knock-down (KD) suppresses the colony-formation ability without affecting c-Myc and E2F1. This study aimed to elucidate the molecular mechanism by which SET enhances the colony-forming ability of HOS cells and to determine whether it is generalized to other cancer cells. Transcriptome analysis revealed that SET KD suppressed mTORC1 signaling. SET KD inhibited Akt phosphorylation, an upstream kinase for mTORC1. PP2A inhibitor blocked SET KD-mediated decrease in phosphorylation of Akt and a mTORC1 substrate p70S6K. A constitutively active form of Akt restored decreased colony-formation ability by SET KD, indicating the SET/PP2A/Akt/mTORC1 axis. Moreover, enrichment analysis clarified that polycomb group protein Bmi-1 is affected by SET KD. SET KD decreased Bmi-1 protein by Akt inhibition but not by mTORC1 inhibition, and exogenous Bmi-1 expression rescued the decrease in colony formation by SET KD. Four out of eight cancer cell lines showed decreased Bmi-1 by SET KD. Analysis of the difference between these cell lines revealed that Myc activity plays a pivotal role in SET KD-mediated Bmi-1 degradation. Our data added new insights into the molecular mechanism of the SET-regulated colony-forming ability, in which Akt-mediated activation of mTORC1/p70S6K and Bmi-1 signaling.

Keywords:  Akt/PKB; Bmi-1; SET; cancer biology; mammalian target of rapamycin (mTOR); polycomb; protein phosphatase 2A (PP2A)

DOI:  https://doi.org/10.1016/j.jbc.2023.105584
Proc Natl Acad Sci U S A. 2024 Jan 02. 121(1): e2315865120

Genome-wide and targeted CRISPR screens identify RNF213 as a mediator of interferon gamma-dependent pathogen restriction in human cells.

Sumit K Matta, Hinissan P Kohio, Pallavi Chandra, Adam Brown, John G Doench, Jennifer A Philips, Siyuan Ding, L David Sibley.

  To define cellular immunity to the intracellular pathogen Toxoplasma gondii, we performed a genome-wide CRISPR loss-of-function screen to identify genes important for (interferon gamma) IFN-γ-dependent growth restriction. We revealed a role for the tumor suppressor NF2/Merlin for maximum induction of Interferon Stimulated Genes (ISG), which are positively regulated by the transcription factor IRF-1. We then performed an ISG-targeted CRISPR screen that identified the host E3 ubiquitin ligase RNF213 as necessary for IFN-γ-mediated control of T. gondii in multiple human cell types. RNF213 was also important for control of bacterial (Mycobacterium tuberculosis) and viral (Vesicular Stomatitis Virus) pathogens in human cells. RNF213-mediated ubiquitination of the parasitophorous vacuole membrane (PVM) led to growth restriction of T. gondii in response to IFN-γ. Moreover, overexpression of RNF213 in naive cells also impaired growth of T. gondii. Surprisingly, growth inhibition did not require the autophagy protein ATG5, indicating that RNF213 initiates restriction independent of a previously described noncanonical autophagy pathway. Mutational analysis revealed that the ATPase domain of RNF213 was required for its recruitment to the PVM, while loss of a critical histidine in the RZ finger domain resulted in partial reduction of recruitment to the PVM and complete loss of ubiquitination. Both RNF213 mutants lost the ability to restrict growth of T. gondii, indicating that both recruitment and ubiquitination are required. Collectively, our findings establish RNF213 as a critical component of cell-autonomous immunity that is both necessary and sufficient for control of intracellular pathogens in human cells.

Keywords:  CRISPR/Cas9; STAT1 signaling; anti-viral; genome-wide screen; interferon

DOI:  https://doi.org/10.1073/pnas.2315865120
Transl Stroke Res. 2023 Dec 26.

Inhibition of USP30 Promotes Mitophagy by Regulating Ubiquitination of MFN2 by Parkin to Attenuate Early Brain Injury After SAH.

Yang Liu, Chenbei Yao, Bin Sheng, Simin Zhi, Xiangxin Chen, Pengfei Ding, Jiatong Zhang, Zhennan Tao, Wei Li, Zong Zhuang, Jiannan Mao, Zheng Peng, Huiying Yan, Wei Jin.

  Subarachnoid hemorrhage (SAH) is a type of stroke with a high disability and mortality rate. Apoptosis caused by massive damage to mitochondria in neuron cells and inflammatory responses caused by high extracellular ATP lead to poor outcomes. USP30 is a deubiquitinating enzyme that inhibits mitophagy, resulting in a failure to remove damaged mitochondria in a timely manner after SAH; nevertheless, the pathway through which USP30 inhibits mitophagy is unknown. This study evaluated the neuroprotective role and possible molecular basis by which inhibiting USP30 to attenuate SAH-induced EBI by promoting neuronal mitophagy. We used an in vitro model of hemoglobin exposure and an in vivo model of intravascular perforation. Increased expression of USP30 was found after SAH in vivo and in vitro, and USP30 inhibition expression in SAH mice treated with MF094 resulted in significant improvement of neurological injury and inflammatory response and mediated good outcomes, suggesting a neuroprotective effect of USP30 inhibition. In cultured neurons, inhibition of USP30 promoted ubiquitination modification of mitochondrial fusion protein 2 (MFN2) by E3 ubiquitin ligase (Parkin), separating damaged mitochondria from the healthy mitochondrial network and prompting mitophagy, causing early clearance of damaged intracellular mitochondria, and reducing the onset of apoptosis. The high extracellular ATP environment was meliorated, reversing the conversion of microglia to a pro-inflammatory phenotype and reducing inflammatory injury. USP30 inhibition had no autophagy-promoting effect on structurally and functionally sound mitochondria and did not inhibit normal intracellular ATP production. The findings suggest that USP30 inhibition has a neuroprotective effect after SAH by promoting early mitophagy after SAH to clear damaged mitochondria.

Keywords:  MF094; Mitochondrial fusion protein 2 (MFN2); Mitophagy; Subarachnoid hemorrhage (SAH); Ubiquitin-specific protease 30 (USP30); Ubiquitination

DOI:  https://doi.org/10.1007/s12975-023-01228-3
Anesthesiology. 2023 Dec 26.

Small G-Protein Rheb gates mTOR signaling to regulate morphine tolerance in mice.

Wenying Wang, Xiaqing Ma, Wenjie Du, Raozhou Lin, Zhongping Li, Wei Jiang, Lu-Yang Wang, Paul F Worley, Tao Xu.

BACKGROUND: Analgesic tolerance due to long-term use of morphine remains a challenge for pain management. Morphine acts on μ-opioid receptors and downstream of the phosphatidylinositol-3-kinase signaling pathway to activate the mammalian target of rapamycin (mTOR) pathway. Rheb is an important regulator of growth and cell-cycle progression in the central nervous system owing to its critical role in the activation of mTOR. We hypothesized that signaling via the GTP-binding protein Rheb in the dorsal horn of the spinal cord is involved in morphine-induced tolerance.METHODS: Male and female wild-type C57BL/6J mice or transgenic mice (6-8 weeks old) were injected intrathecally with saline or morphine twice daily at 12-h intervals for five consecutive days to establish a tolerance model. Analgesia was assessed 60 min later using the tail-flick assay. After five days, the spine was harvested for western blot or immunofluorescence analysis.
RESULTS: Chronic morphine administration resulted in the upregulation of spinal Rheb by 4.27±0.195 fold (P=0.0036, n=6), in turn activating mTOR by targeting rapamycin complex 1 (mTORC1). Genetic overexpression of Rheb impaired morphine analgesia, resulting in a tail-flick latency of 4.65±1.10 s (P<0.0001, n=7) in Rheb KI mice compared to 10 s in control mice (10±0 s). Additionally, Rheb overexpression in spinal excitatory neurons led to mTORC1 signaling overactivation. Genetic knockout of Rheb or inhibition of mTORC1 signaling by rapamycin potentiated morphine-induced tolerance (MPE: 52.60±9.56% in the morphine + rapamycin group vs 16.60±8.54% in the morphine group, P<0.0001). Moreover, activation of endogenous adenosine 5'-monophosphate-activated protein kinase inhibited Rheb upregulation and retarded the development of morphine-dependent tolerance (MPE: 39.51±7.40% in morphine + metformin group vs 15.58±5.79% in morphine group, P<0.0001).
CONCLUSION: This study suggests spinal Rheb as a key molecular factor for regulating mTOR signaling.

DOI: https://doi.org/10.1097/ALN.0000000000004885
Life Sci. 2023 Dec 22. pii: S0024-3205(23)01006-8. [Epub ahead of print] 122371

Prohibitin 2: A key regulator of cell function.

Bingjie Zhang, Wentao Li, Jiaying Cao, Yanhong Zhou, Xia Yuan.

  The PHB2 gene is located on chromosome 12p13 and encodes prohibitin 2, a highly conserved protein of 37 kDa. PHB2 is a dimer with antiparallel coils, possessing a unique negatively charged region crucial for its mitochondrial molecular chaperone functions. Thus, PHB2 plays a significant role in cell life activities such as mitosis, mitochondrial autophagy, signal transduction, and cell death. This review discusses how PHB2 inhibits transcription factors or nuclear receptors to maintain normal cell functions; how PHB2 in the cytoplasm or membrane ensures normal cell mitosis and regulates cell differentiation; how PHB2 affects mitochondrial structure, function, and cell apoptosis through mitochondrial intimal integrity and mitochondrial autophagy; how PHB2 affects mitochondrial stress and inhibits cell apoptosis by regulating cytochrome c migration and other pathways; how PHB2 affects cell growth, proliferation, and metastasis through a mitochondrial independent mechanism; and how PHB2 could be applied in disease treatment. We provide a theoretical basis and an innovative perspective for a comprehensive understanding of the role and mechanism of PHB2 in cell function regulation.

Keywords:  Cell physiology; Drug targeting; Mitophagy; PHB2; Signal transduction

DOI:  https://doi.org/10.1016/j.lfs.2023.122371
Stem Cell Rev Rep. 2023 Dec 28.

The Chaperone Protein Cct5 is Essential for Hematopoietic Stem Cell Maintenance.

Linxi Li, Jie Huang, Suping Zhang, Chunxu Yao, Yandan Chen, Haitao Wang, Bin Guo.

  Proper proteostasis is indispensable for the long-term maintenance of hematopoietic stem and progenitor cells (HSPCs). The TRiC/CCT (chaperonin-containing TCP-1) complex, a key constituent of cellular machinery facilitating accurate protein folding, has remained enigmatic in its specific function within HSPCs. Here we show that conditional knockout (KO) of Cct5 significantly impairs the maintenance of murine HSPCs. Primary and secondary transplantation experiments unequivocally demonstrate the incapacity of Cct5 KO HSPCs to reconstitute both myeloid and lymphoid lineage cells in recipient mice, highlighting the pivotal role of the TRiC/CCT complex in governing these cellular lineages. Furthermore, leveraging an integrated approach that merges a Protein-Protein Interaction (PPI) database with RNA sequencing (RNA-seq) data of HSPCs, our analysis reveals intricate interactions between Cct5 and vital transcription factors crucial for HSC homeostasis. Notably, Cct5 engages with MYC, PIAS1, TP53, ESR1, HOXA1, and JUN, intricately regulating the transcriptional landscape governing autophagy, myeloid differentiation, and cytoskeleton organization within HSPCs. Our study unveils the profound significance of TRiC/CCT complex-mediated proteostasis in orchestrating the maintenance and functionality of HSPCs.

Keywords:  Autophagy; Chaperonin; Hematopoietic Stem Cell; Maintenance; Proteostasis

DOI:  https://doi.org/10.1007/s12015-023-10670-7
Adv Biol (Weinh). 2023 Dec 27. e2300560

Temperature-Dependent Relationship of Autophagy and Apoptotic Signaling During Cold-Water Immersion in Young and Older Males.

Kelli E King, James J McCormick, Glen P Kenny.

  Autophagy is a crucial cytoprotective mechanism preventing the accumulation of cellular damage, especially during external stimuli such as cold exposure. Older adults poorly tolerate cold exposure and age-related impairments in autophagy may contribute to the associated reductions in cold tolerance. The purpose of this investigation is to evaluate the effect of different intensities of in vivo cold-water immersion and in vitro cold exposure on autophagic and apoptotic signaling in young and older males. Peripheral blood mononuclear cells (PBMCs) are isolated at baseline, end-cold exposure, and after 3 h of thermoneutral recovery. Additionally, PBMCs are treated with rapamycin and bafilomycin prior to in vitro cold exposure equivalent to in vivo core temperatures (35-37 °C). Proteins associated with autophagy, apoptosis, the heat shock response, and inflammation are analyzed via Western blotting. Moderate cold stress (0.5 °C decrease in core temperature) increased autophagic and heat shock protein activity while high cold stress (1.0 °C decrease in core temperature) augmented apoptosis in young males. In older males, minimal autophagic activation during both cold-water exposures are associated with increased apoptotic and inflammatory proteins. Although in vitro cold exposure confirmed age-related dysfunction in autophagy, rapamycin-induced stimulation of autophagic proteins underlie the potential to reverse age-related vulnerability to cold exposure.

Keywords:  aging; apoptosis; cold; heat shock proteins; macroautophagy

DOI:  https://doi.org/10.1002/adbi.202300560
In Vivo. 2024 Jan-Feb;38(1):38(1): 196-204

Mitophagy Decreases in the Peripheral Vestibular System of Aged C57BL/6J Mice.

Sung Il Cho, Eu-Ri Jo, Suhyun Lee.

  BACKGROUND/AIM: Mitophagy is a cardinal process for maintaining healthy and functional mitochondria. A decline in mitophagy has been associated with age-related pathologies. We aimed to investigate mitophagy changes in age-related balance problems using an animal model.MATERIALS AND METHODS: C57BL/6J mice were divided into young (1 month old) and aged (12 months old) groups. Balance performance, mitochondrial DNA integrity, ATP content, mitophagic process, and mitophagy-related genes and proteins were investigated in both groups.
RESULTS: Balance and motor performance were reduced in the aged group. Mitochondrial DNA integrity and ATP content, and mRNA levels of PINK1, Parkin, BNIP3, AMBRA1, MUL1, NIX, Bcl2-L-13, Atg3, Atg5, Atg12, and Atg13 in the vestibule were significantly lower in aged mice compared with those in young mice. The protein levels of PINK1, Parkin, BNIP3, LC3B, and OXPHOS subunits were significantly decreased in the aged vestibule. Mitophagosome and mitophagolysosome counts and the immunohistochemical expression of Parkin and BNIP3 were also decreased in the saccule, utricle, and crista ampullaris in the aged group.
CONCLUSION: A general decrease in mitophagy with aging might be attributed to a decrease in cellular function in the aged vestibule during the development of age-related balance problems.

Keywords:  Mitophagy; aging; mice; vestibular system

DOI:  https://doi.org/10.21873/invivo.13426
Tissue Eng Regen Med. 2023 Dec 28.

Long and Short-Term Effect of mTOR Regulation on Cerebral Organoid Growth and Differentiations.

Sung Bum Park, Byungho Lim, Ki Young Kim, Byumseok Koh.

  BACKGROUND: The mammalian target of rapamycin (mTOR) signaling is critical for the maintenance and differentiation of neurogenesis, and conceivably for many other brain developmental processes. However, in vivo studies of mTOR functions in the brain are often hampered due to the essential role of the associated signaling in brain development.METHODS: We monitored the long- and short-term effects of mTOR signaling regulation on cerebral organoids growth, differentiation and function using an mTOR inhibitor (everolimus) and an mTOR activator (MHY1485).
RESULTS: Short-term treatment with MHY1485 induced faster organoid growth and differentiation, while long-term treatment induced the maturation of cerebral organoids.
CONCLUSION: These data suggest that the optimal activity of mTOR is crucial in maintaining normal brain development, and its role is not confined to the early neurogenic phase of brain development.

Keywords:  Cerebral organoids; Differentiation; Growth; mTOR regulation

DOI:  https://doi.org/10.1007/s13770-023-00611-3
J Control Release. 2023 Dec 22. pii: S0168-3659(23)00816-7. [Epub ahead of print]

Autophagy-modulating biomembrane nanostructures: A robust anticancer weapon by modulating the inner and outer cancer environment.

Xinyi Zhang, Mengya Zhang, Hengqing Cui, Tinglin Zhang, Lili Wu, Can Xu, Chuan Yin, Jie Gao.

  Recently, biomembrane nanostructures, such as liposomes, cell membrane-coated nanostructures, and exosomes, have demonstrated promising anticancer therapeutic effects. These nanostructures possess remarkable biocompatibility, multifunctionality, and low toxicity. However, their therapeutic efficacy is impeded by chemoresistance and radiotherapy resistance, which are closely associated with autophagy. Modulating autophagy could enhance the therapeutic sensitivity and effectiveness of these biomembrane nanostructures by influencing the immune system and the cancer microenvironment. For instance, autophagy can regulate the immunogenic cell death of cancer cells, antigen presentation of dendritic cells, and macrophage polarization, thereby activating the inflammatory response in the cancer microenvironment. Furthermore, combining autophagy-regulating drugs or genes with biomembrane nanostructures can exploit the targeting and long-term circulation properties of these nanostructures, leading to increased drug accumulation in cancer cells. This review explores the role of autophagy in carcinogenesis, cancer progression, metastasis, cancer immune responses, and resistance to treatment. Additionally, it highlights recent research advancements in the synergistic anticancer effects achieved through autophagy regulation by biomembrane nanostructures. The review also discusses the prospects and challenges associated with the future clinical translation of these innovative treatment strategies. In summary, these findings provide valuable insights into autophagy, autophagy-modulating biomembrane-based nanostructures, and the underlying molecular mechanisms, thereby facilitating the development of promising cancer therapeutics.

Keywords:  Autophagy; Biomembrane-based nanostructures; Immunotherapy; cancer environment; cancer therapy

DOI:  https://doi.org/10.1016/j.jconrel.2023.12.032
Glycoconj J. 2023 Dec 26.

Lysosomal sialidase NEU1, its intracellular properties, deficiency, and use as a therapeutic agent.

Kohji Itoh, Jun Tsukimoto.

  Neuraminidase 1 (NEU1) is a lysosomal sialidase that cleaves terminal α-linked sialic acid residues from sialylglycans. NEU1 is biosynthesized in the rough endoplasmic reticulum (RER) lumen as an N-glycosylated protein to associate with its protective protein/cathepsin A (CTSA) and then form a lysosomal multienzyme complex (LMC) also containing β-galactosidase 1 (GLB1). Unlike other mammalian sialidases, including NEU2 to NEU4, NEU1 transport to lysosomes requires association of NEU1 with CTSA, binding of the CTSA carrying terminal mannose 6-phosphate (M6P)-type N-glycan with M6P receptor (M6PR), and intralysosomal NEU1 activation at acidic pH. In contrast, overexpression of the single NEU1 gene in mammalian cells causes intracellular NEU1 protein crystallization in the RER due to self-aggregation when intracellular CTSA is reduced to a relatively low level. Sialidosis (SiD) and galactosialidosis (GS) are autosomal recessive lysosomal storage diseases caused by the gene mutations of NEU1 and CTSA, respectively. These incurable diseases associate with the NEU1 deficiency, excessive accumulation of sialylglycans in neurovisceral organs, and systemic manifestations. We established a novel GS model mouse carrying homozygotic Ctsa IVS6 + 1 g/a mutation causing partial exon 6 skipping with simultaneous deficiency of Ctsa and Neu1. Symptoms developed in the GS mice like those in juvenile/adult GS patients, such as myoclonic seizures, suppressed behavior, gargoyle-like face, edema, proctoptosis due to Neu1 deficiency, and sialylglycan accumulation associated with neurovisceral inflammation. We developed a modified NEU1 (modNEU1), which does not form protein crystals but is transported to lysosomes by co-expressed CTSA. In vivo gene therapy for GS and SiD utilizing a single adeno-associated virus (AAV) carrying modNEU1 and CTSA genes under dual promoter control will be created.

Keywords:  Galactosialidosis; Gene therapy; Lysosomal storage disorder; Neu1/Ctsa-deficient mouse; Protein crystallization; Sialidase; Sialidosis; Sialylglycans

DOI:  https://doi.org/10.1007/s10719-023-10135-6
J Nutr Biochem. 2023 Dec 24. pii: S0955-2863(23)00288-7. [Epub ahead of print] 109555

Betaine attenuates age-related suppression in autophagy via Mettl21c/p97/VCP axis to delay muscle loss.

Si Chen, Jiedong Chen, Chen Wang, Tongtong He, Zhijun Yang, Wenge Huang, Xiaolin Luo, Huilian Zhu.

  Age-related impairment of autophagy accelerates muscle loss and lead to sarcopenia. Betaine can delay muscle loss as a dietary methyl donor via increasing S-adenosyl-L-methionine (SAM, a crucial metabolite for autophagy regulation) in methionion cycle. However, whether betaine can regulate autophagy level to attenuate degeneration in aging muscle remains unclear. Herein, male C57BL/6J young mice (YOU, 2-month-old), old mice (OLD, 15-month-old), and 2%-betaine-treated old mice (BET, 15-month-old) were employed and raised for 12 weeks. All mice underwent body composition examination and grip strength test before being sacrificed. Betaine alleviated age-related decline in muscle mass and strength. Meanwhile, betaine preserved the expression autophagy markers (Atg5, Atg7, LC3-II, and Beclin1) both at transcriptional and translational level during the aging process. RNA-sequencing results generated from mice gastrocnemius muscle found Mettl21c, a SAM-dependent autophagy-regulating methyltransferase, was significantly higher expressed in BET and YOU group. Results were further validated by qPCR and Western bloting. In vitro, C2C12 cells with or without Mettl21c RNA interference were treated different concentration of betaine (0mM, 10mM) under methionine-starved condition. Compared with control group, betaine upregulated autophagy markers expression and autophagy flux. By increasing the SAM level, betaine facilitated trimethylation of p97 (Mettl21c downstream effector) into valosin-containing protein (VCP). Increased VCP promoted autophagic turnover of cellular components, ATP production, and cell differentiation. Knock-down of Metthl21c dismissed improvements mentioned above. Collectively, betaine could enhance aged skeletal muscle autophagy level via Mettl21c/p97/VCP axis to delay muscle loss.

Keywords:  Mettl21c; age-related muscle loss; autophagy; betaine

DOI:  https://doi.org/10.1016/j.jnutbio.2023.109555
Gene. 2023 Dec 25. pii: S0378-1119(23)00951-4. [Epub ahead of print] 148110

Solute carrier family 35 member A2 regulates mitophagy through the PI3K/AKT/mTOR axis, promoting the proliferation, migration, and invasion of osteosarcoma cells.

Xiaohui Luo, Jiongfeng Zhang, Chong Guo, Ning Jiang, Feifei Zhang, Quahui Jiao, Kai Xu, Jun Yang, Gaoyang Qu, Xiao-Bin Lv, Zhiping Zhang.

  The treatment of osteosarcoma patients exhibits individual variability, underscoring the critical importance of targeted therapy. Although (Solute carrier family 35 member A2) SLC35A2's role in the progression of various cancers has been extensively investigated, its specific implications in osteosarcoma remain unexplored. Leveraging data from the (The Cancer Genome Atlas) TCGA and (Genotype-Tissue Expression) GTEx databases, we have discerned that SLC35A2 is notably upregulated in osteosarcoma and correlates with the prognosis of osteosarcoma patients. Consequently, it becomes imperative to delve into the role of SLC35A2 in the context of osteosarcoma. Our research substantiates that SLC35A2 exerts a notable influence on mitochondrial autophagy in osteosarcoma, thereby exerting cascading effects on the proliferation, migration, invasion, and apoptosis of osteosarcoma cells. Mechanistically, SLC35A2 orchestrates mitochondrial autophagy via the PI3K/AKT/mTOR signaling pathway. Moreover, we have conducted rigorous animal experiments to further corroborate the repercussions of SLC35A2 on osteosarcoma growth. In summation, our study elucidates that SLC35A2's modulation of mitochondrial autophagy through the PI3K/AKT/mTOR signaling pathway constitutes a pivotal factor in the malignant progression of osteosarcoma, unveiling promising therapeutic targets for patients grappling with this condition.

Keywords:  Mitophagy; Osteosarcoma; PI3K/SKT/mTOR; SLC35A2

DOI:  https://doi.org/10.1016/j.gene.2023.148110