bims-midtic 2023-08-06 papers

bims-midtic

Biomed News

on Mitochondrial dynamics and trafficking in cells

Issue of 2023–08–06
nineteen papers selected by
Omkar Joshi, Turku Bioscience

Completion of mitochondrial division requires the intermembrane space protein Mdi1/Atg44.
Contact sites between endoplasmic reticulum sheets and mitochondria regulate mitochondrial DNA replication and segregation.
Endoplasmic reticulum-mitochondrial calcium transport contributes to soft extracellular matrix-triggered mitochondrial dynamics and mitophagy in breast carcinoma cells.
Nanoscale details of mitochondrial constriction revealed by cryo-electron tomography.
Ultrastructural analysis of prostate cancer tissue provides insights into androgen-dependent adaptations to membrane contact site establishment.
High-fat diet causes mitochondrial damage and downregulation of mitofusin-2 and optic atrophy-1 in multiple organs.
FBXO7/ntc and USP30 antagonistically set the ubiquitination threshold for basal mitophagy and provide a target for Pink1 phosphorylation in vivo.
Mitochondria dysregulation contributes to secondary neurodegeneration progression post-contusion injury in human 3D in vitro triculture brain tissue model.
Convergent and divergent mechanisms of peroxisomal and mitochondrial division.
Epigenetic modulation of Drp1-mediated mitochondrial fission by inhibition of S-adenosylhomocysteine hydrolase promotes vascular senescence and atherosclerosis.
Phospholipids can regulate complex I assembly independent of their role in maintaining mitochondrial membrane integrity.
Controllable mitochondrial aggregation and fusion by a programmable DNA binder.
Targeting calcium homeostasis and impaired inter-organelle crosstalk as a potential therapeutic approach in Parkinson's disease.
Genome-wide kinase-MAM interactome screening reveals the role of CK2A1 in MAM Ca2+ dynamics linked to DEE66.
Inhibition of mitochondrial fission and protein kinase R improves progesterone in placental stress.
The effects of general anesthetics on mitochondrial structure and function in the developing brain.
The GLI2/CDH6 axis enhances migration, invasion and mitochondrial fission of stomach adenocarcinoma cells.
End-binding protein 1 regulates the metabolic fate of CD4+ T lymphoblasts and Jurkat T cells and the organization of the mitochondrial network.
Differential temporal therapies with pharmacologically targeted mitochondrial fission/fusion protect the brain against acute myocardial ischemia-reperfusion injury in prediabetic rats: The crosstalk between mitochondrial apoptosis and inflammation.

J Cell Biol. 2023 Oct 02. pii: e202303147. [Epub ahead of print]222(10):

Completion of mitochondrial division requires the intermembrane space protein Mdi1/Atg44.

Olivia M Connor, Srujan K Matta, Jonathan R Friedman.

Mitochondria are highly dynamic double membrane-bound organelles that maintain their shape in part through fission and fusion. Mitochondrial fission is performed by a dynamin-related protein, Dnm1 (Drp1 in humans), that constricts and divides the mitochondria in a GTP hydrolysis-dependent manner. However, it is unclear whether factors inside mitochondria help coordinate the process and if Dnm1/Drp1 activity is sufficient to complete the fission of both mitochondrial membranes. Here, we identify an intermembrane space protein required for mitochondrial fission in yeast, which we propose to name Mdi1 (also named Atg44). Loss of Mdi1 causes mitochondrial hyperfusion due to defects in fission, but not the lack of Dnm1 recruitment to mitochondria. Mdi1 is conserved in fungal species, and its homologs contain an amphipathic α-helix, mutations of which disrupt mitochondrial morphology. One model is that Mdi1 distorts mitochondrial membranes to enable Dnm1 to robustly complete fission. Our work reveals that Dnm1 cannot efficiently divide mitochondria without the coordinated function of Mdi1 inside mitochondria.

DOI: https://doi.org/10.1083/jcb.202303147
iScience. 2023 Jul 21. 26(7): 107180

Contact sites between endoplasmic reticulum sheets and mitochondria regulate mitochondrial DNA replication and segregation.

Hema Saranya Ilamathi, Sara Benhammouda, Amel Lounas, Khalid Al-Naemi, Justine Desrochers-Goyette, Matthew A Lines, François J Richard, Jackie Vogel, Marc Germain.

  Mitochondria are multifaceted organelles crucial for cellular homeostasis that contain their own genome. Mitochondrial DNA (mtDNA) replication is a spatially regulated process essential for the maintenance of mitochondrial function, its defect causing mitochondrial diseases. mtDNA replication occurs at endoplasmic reticulum (ER)-mitochondria contact sites and is affected by mitochondrial dynamics: The absence of mitochondrial fusion is associated with mtDNA depletion whereas loss of mitochondrial fission causes the aggregation of mtDNA within abnormal structures termed mitobulbs. Here, we show that contact sites between mitochondria and ER sheets, the ER structure associated with protein synthesis, regulate mtDNA replication and distribution within mitochondrial networks. DRP1 loss or mutation leads to modified ER sheets and alters the interaction between ER sheets and mitochondria, disrupting RRBP1-SYNJ2BP interaction. Importantly, mtDNA distribution and replication were rescued by promoting ER sheets-mitochondria contact sites. Our work identifies the role of ER sheet-mitochondria contact sites in regulating mtDNA replication and distribution.

Keywords:  Biochemistry; Biological sciences; Cell biology

DOI:  https://doi.org/10.1016/j.isci.2023.107180
Acta Biomater. 2023 Aug 02. pii: S1742-7061(23)00452-X. [Epub ahead of print]

Endoplasmic reticulum-mitochondrial calcium transport contributes to soft extracellular matrix-triggered mitochondrial dynamics and mitophagy in breast carcinoma cells.

Yu Chen, Ping Li, Xiangyan Chen, Ran Yan, Yixi Zhang, Meng Wang, Xiang Qin, Shun Li, Chuan Zheng, Fengming You, Tingting Li, Yiyao Liu.

  Although mitochondrial morphology and function are considered to be closely related to matrix stiffness-driven tumor progression, it remains poorly understood how extracellular matrix (ECM) stiffness affects mitochondrial dynamics and mitophagy. Here, we found that soft substrate triggered calcium transport by increasing endoplasmic reticulum (ER) calcium release and mitochondrial (MITO) calcium uptake. ER-MITO calcium transport promoted the recruitment of dynamin-related protein 1 (Drp1) to mitochondria and phosphorylation at the serine 616 site, which induced mitochondrial fragmentation and Parkin/PINK1-mediated mitophagy. Furthermore, in vivo experiments demonstrated that soft ECM enhanced calcium levels in tumor tissue, Drp1 activity was required for soft ECM-induced mitochondrial dynamics impairment, and inhibition of Drp1 activity enhanced soft ECM-induced tumor necrosis. In conclusion, we revealed a new mechanism whereby ER-MITO calcium transport regulated mitochondrial dynamics and mitophagy through Drp1 translocation in response to soft substrates. These findings provide valuable insights into ECM stiffness as a potential target for antitumor therapy. STATEMENT OF SIGNIFICANCE: : Here, we examined the relationship between substrate stiffness and mitochondrial dynamics by using polyacrylamide (PAA) substrates to simulate the stages of breast cancer or BAPN to reduce tumor tissue stiffness. The results elucidated that soft substrate triggered the recruitment of DRP1 and subsequent mitochondrial fission and mitophagy by ER-MITO calcium transport. Furthermore, mitophagy partly attenuated soft ECM-mediated tumor tissue necrosis and contributed to tumor survival in vivo. Our discoveries revealed the molecular mechanisms by which mechanical stimulation regulates mitochondrial dynamics, providing valuable insights into ECM stiffness as a target for anti-tumor approaches, which could be beneficial for both biomechanics research and clinical applications.

Keywords:  ER-MITO calcium transport; Extracellular matrix (ECM) stiffness; Mitochondrial dynamics; Mitophagy

DOI:  https://doi.org/10.1016/j.actbio.2023.07.060
Biophys J. 2023 Aug 01. pii: S0006-3495(23)00481-2. [Epub ahead of print]

Nanoscale details of mitochondrial constriction revealed by cryo-electron tomography.

Shrawan Kumar Mageswaran, Danielle Ann Grotjahn, Xiangrui Zeng, Benjamin Asher Barad, Michaela Medina, My Hanh Hoang, Megan J Dobro, Yi-Wei Chang, Min Xu, Wei Yuan Yang, Grant J Jensen.

Mitochondria adapt to changing cellular environments, stress stimuli, and metabolic demands through dramatic morphological remodeling of their shape, and thus function. Such mitochondrial dynamics is often dependent on cytoskeletal filament interactions. However, the precise organization of these filamentous assemblies remains speculative. Here, we apply cryogenic electron tomography to directly image the nanoscale architecture of the cytoskeletal-membrane interactions involved in mitochondrial dynamics in response to damage. We induced mitochondrial damage via membrane depolarization, a cellular stress associated with mitochondrial fragmentation and mitophagy. We find that, in response to acute membrane depolarization, mammalian mitochondria predominantly organize into tubular morphology that abundantly displays constrictions. We observe long bundles of both unbranched actin and septin filaments enriched at these constrictions. We also observed septin-microtubule interactions at these sites and elsewhere suggesting that these two filaments guide each other in the cytosolic space. Together, our results provide empirical parameters for the architecture of mitochondrial constriction factors to validate/refine existing models and inform the development of new ones.

DOI: https://doi.org/10.1016/j.bpj.2023.07.030
Front Oncol. 2023 ;13 1217741

Ultrastructural analysis of prostate cancer tissue provides insights into androgen-dependent adaptations to membrane contact site establishment.

Lisa M Butler, Emma Evergren.

  Membrane trafficking and organelle contact sites are important for regulating cell metabolism and survival; processes often deregulated in cancer. Prostate cancer is the second leading cause of cancer-related death in men in the developed world. While early-stage disease is curable by surgery or radiotherapy there is an unmet need to identify prognostic biomarkers, markers to treatment response and new therapeutic targets in intermediate-late stage disease. This study explored the morphology of organelles and membrane contact sites in tumor tissue from normal, low and intermediate histological grade groups. The morphology of organelles in secretory prostate epithelial cells; including Golgi apparatus, ER, lysosomes; was similar in prostate tissue samples across a range of Gleason scores. Mitochondrial morphology was not dramatically altered, but the number of membrane contacts with the ER notably increased with disease progression. A three-fold increase of tight mitochondria-ER membrane contact sites was observed in the intermediate Gleason score group compared to normal tissue. To investigate whether these changes were concurrent with an increased androgen signaling in the tissue, we investigated whether an anti-androgen used in the clinic to treat advanced prostate cancer (enzalutamide) could reverse the phenotype. Patient-derived explant tissues with an intermediate Gleason score were cultured ex vivo in the presence or absence of enzalutamide and the number of ER-mitochondria contacts were quantified for each matched pair of tissues. Enzalutamide treated tissue showed a significant reduction in the number and length of mitochondria-ER contact sites, suggesting a novel androgen-dependent regulation of these membrane contact sites. This study provides evidence for the first time that prostate epithelial cells undergo adaptations in membrane contact sites between mitochondria and the ER during prostate cancer progression. These adaptations are androgen-dependent and provide evidence for a novel hormone-regulated mechanism that support establishment and extension of MAMs. Future studies will determine whether these changes are required to maintain pro-proliferative signaling and metabolic changes that support prostate cancer cell viability.

Keywords:  androgen-deprivation; lipophagy; membrane-contact site; mitochondria-associated membrane; patient-derived tumor explant

DOI:  https://doi.org/10.3389/fonc.2023.1217741
J Clin Biochem Nutr. 2023 Jul;73(1): 61-76

High-fat diet causes mitochondrial damage and downregulation of mitofusin-2 and optic atrophy-1 in multiple organs.

Peng Zheng, Wenjing Ma, Yilu Gu, Hengfang Wu, Zhiping Bian, Nannan Liu, Di Yang, Xiangjian Chen.

  High-fat consumption promotes the development of obesity, which is associated with various chronic illnesses. Mitochondria are the energy factories of eukaryotic cells, maintaining self-stability through a fine-tuned quality-control network. In the present study, we evaluated high-fat diet (HFD)-induced changes in mitochondrial ultrastructure and dynamics protein expression in multiple organs. C57BL/6J male mice were fed HFD or normal diet (ND) for 24 weeks. Compared with ND-fed mice, HFD-fed mice exhibited increased body weight, cardiomyocyte enlargement, pulmonary fibrosis, hepatic steatosis, renal and splenic structural abnormalities. The cellular apoptosis of the heart, liver, and kidney increased. Cellular lipid droplet deposition and mitochondrial deformations were observed. The proteins related to mitochondrial biogenesis (TFAM), fission (DRP1), autophagy (LC3 and LC3-II: LC3-I ratio), and mitophagy (PINK1) presented different changes in different organs. The mitochondrial fusion regulators mitofusin-2 (MFN2) and optic atrophy-1 (OPA1) were consistently downregulated in multiple organs, even the spleen. TOMM20 and ATP5A protein were enhanced in the heart, skeletal muscle, and spleen, and attenuated in the kidney. These results indicated that high-fat feeding caused pathological changes in multiple organs, accompanied by mitochondrial ultrastructural damage, and MFN2 and OPA1 downregulation. The mitochondrial fusion proteins may become promising targets and/or markers for treating metabolic disease.

Keywords:  high-fat diet; hyperlipidemia; mitochondria; mitofusin-2; optic atrophy-1

DOI:  https://doi.org/10.3164/jcbn.22-73
PLoS Biol. 2023 Aug 03. 21(8): e3002244

FBXO7/ntc and USP30 antagonistically set the ubiquitination threshold for basal mitophagy and provide a target for Pink1 phosphorylation in vivo.

Alvaro Sanchez-Martinez, Aitor Martinez, Alexander J Whitworth.

Functional analyses of genes linked to heritable forms of Parkinson's disease (PD) have revealed fundamental insights into the biological processes underpinning pathogenic mechanisms. Mutations in PARK15/FBXO7 cause autosomal recessive PD and FBXO7 has been shown to regulate mitochondrial homeostasis. We investigated the extent to which FBXO7 and its Drosophila orthologue, ntc, share functional homology and explored its role in mitophagy in vivo. We show that ntc mutants partially phenocopy Pink1 and parkin mutants and ntc overexpression supresses parkin phenotypes. Furthermore, ntc can modulate basal mitophagy in a Pink1- and parkin-independent manner by promoting the ubiquitination of mitochondrial proteins, a mechanism that is opposed by the deubiquitinase USP30. This basal ubiquitination serves as the substrate for Pink1-mediated phosphorylation that triggers stress-induced mitophagy. We propose that FBXO7/ntc works in equilibrium with USP30 to provide a checkpoint for mitochondrial quality control in basal conditions in vivo and presents a new avenue for therapeutic approaches.

DOI: https://doi.org/10.1371/journal.pbio.3002244
Cell Death Dis. 2023 Aug 03. 14(8): 496

Mitochondria dysregulation contributes to secondary neurodegeneration progression post-contusion injury in human 3D in vitro triculture brain tissue model.

Volha Liaudanskaya, Nicholas J Fiore, Yang Zhang, Yuka Milton, Marilyn F Kelly, Marly Coe, Ariana Barreiro, Victoria K Rose, Matthew R Shapiro, Adam S Mullis, Anna Shevzov-Zebrun, Mathew Blurton-Jones, Michael J Whalen, Aviva J Symes, Irene Georgakoudi, Thomas J F Nieland, David L Kaplan.

Traumatic Brain injury-induced disturbances in mitochondrial fission-and-fusion dynamics have been linked to the onset and propagation of neuroinflammation and neurodegeneration. However, cell-type-specific contributions and crosstalk between neurons, microglia, and astrocytes in mitochondria-driven neurodegeneration after brain injury remain undefined. We developed a human three-dimensional in vitro triculture tissue model of a contusion injury composed of neurons, microglia, and astrocytes and examined the contributions of mitochondrial dysregulation to neuroinflammation and progression of injury-induced neurodegeneration. Pharmacological studies presented here suggest that fragmented mitochondria released by microglia are a key contributor to secondary neuronal damage progression after contusion injury, a pathway that requires astrocyte-microglia crosstalk. Controlling mitochondrial dysfunction thus offers an exciting option for developing therapies for TBI patients.

DOI: https://doi.org/10.1038/s41419-023-05980-0
J Cell Biol. 2023 09 04. pii: e202304076. [Epub ahead of print]222(9):

Convergent and divergent mechanisms of peroxisomal and mitochondrial division.

Suresh Subramani, Nandini Shukla, Jean-Claude Farre.

Organelle division and segregation are important in cellular homeostasis. Peroxisomes (POs) and mitochondria share a core division machinery and mechanism of membrane scission. The division of each organelle is interdependent not only on the other but also on other organelles, reflecting the dynamic communication between subcellular compartments, even as they coordinate the exchange of metabolites and signals. We highlight common and unique mechanisms involved in the fission of these organelles under the premise that much can be gleaned regarding the division of one organelle based on information available for the other.

DOI: https://doi.org/10.1083/jcb.202304076
Redox Biol. 2023 Jul 25. pii: S2213-2317(23)00229-X. [Epub ahead of print]65 102828

Epigenetic modulation of Drp1-mediated mitochondrial fission by inhibition of S-adenosylhomocysteine hydrolase promotes vascular senescence and atherosclerosis.

Yiran You, Xu Chen, Yu Chen, Juan Pang, Qian Chen, Qiannan Liu, Hongliang Xue, Yupeng Zeng, Jinghe Xiao, Jiaxin Mi, Yi Tang, Wenhua Ling.

   AIMS: Vascular senescence, which is closely related to epigenetic regulation, is an early pathological condition in cardiovascular diseases including atherosclerosis. Inhibition of S-adenosylhomocysteine hydrolase (SAHH) and the consequent increase of S-adenosylhomocysteine (SAH), a potent inhibitor of DNA methyltransferase, has been associated with an elevated risk of cardiovascular diseases. This study aimed to investigate whether the inhibition of SAHH accelerates vascular senescence and the development of atherosclerosis.
METHODS AND RESULTS: The case-control study related to vascular aging showed that increased levels of plasma SAH were positively associated with the risk of vascular aging, with an odds ratio (OR) of 3.90 (95% CI, 1.17-13.02). Elevated pulse wave velocity, impaired endothelium-dependent relaxation response, and increased senescence-associated β-galactosidase staining were observed in the artery of SAHH+/- mice at 32 weeks of age. Additionally, elevated expression of p16, p21, and p53, fission morphology of mitochondria, and over-upregulated expression of Drp1 were observed in vascular endothelial cells with SAHH inhibition in vitro and in vivo. Further downregulation of Drp1 using siRNA or its specific inhibitor, mdivi-1, restored the abnormal mitochondrial morphology and rescued the phenotypes of vascular senescence. Furthermore, inhibition of SAHH in APOE-/- mice promoted vascular senescence and atherosclerosis progression, which was attenuated by mdivi-1 treatment. Mechanistically, hypomethylation over the promoter region of DRP1 and downregulation of DNMT1 were demonstrated with SAHH inhibition in HUVECs.
CONCLUSIONS: SAHH inhibition epigenetically upregulates Drp1 expression through repressing DNA methylation in endothelial cells, leading to vascular senescence and atherosclerosis. These results identify SAHH or SAH as a potential therapeutic target for vascular senescence and cardiovascular diseases.

Keywords:  Atherosclerosis; DNA methylation; S-adenosylhomocysteine hydrolase; mitochondrial dynamics; vascular senescence

DOI:  https://doi.org/10.1016/j.redox.2023.102828
Cell Rep. 2023 Jul 29. pii: S2211-1247(23)00857-4. [Epub ahead of print]42(8): 112846

Phospholipids can regulate complex I assembly independent of their role in maintaining mitochondrial membrane integrity.

Anjaneyulu Murari, Shauna-Kay Rhooms, Divya Vimal, Kaniz Fatima Binte Hossain, Sanjay Saini, Maximino Villanueva, Michael Schlame, Edward Owusu-Ansah.

  Several phospholipid (PL) molecules are intertwined with some mitochondrial complex I (CI) subunits in the membrane domain of CI, but their function is unclear. We report that when the Drosophila melanogaster ortholog of the intramitochondrial PL transporter, STARD7, is severely disrupted, assembly of the oxidative phosphorylation (OXPHOS) system is impaired, and the biogenesis of several CI subcomplexes is hampered. However, intriguingly, a restrained knockdown of STARD7 impairs the incorporation of NDUFS5 and NDUFA1 into the proximal part of the CI membrane domain without directly affecting the incorporation of subunits in the distal part of the membrane domain, OXPHOS complexes already assembled, or mitochondrial cristae integrity. Importantly, the restrained knockdown of STARD7 appears to induce a modest amount of cardiolipin remodeling, indicating that there could be some alteration in the composition of the mitochondrial phospholipidome. We conclude that PLs can regulate CI biogenesis independent of their role in maintaining mitochondrial membrane integrity.

Keywords:  CP: Molecular biology; Drosophila; NDUFA1; NDUFS5; OXPHOS; STARD7; complex I; mitochondria; phospholipid

DOI:  https://doi.org/10.1016/j.celrep.2023.112846
Chem Sci. 2023 Aug 02. 14(30): 8084-8094

Controllable mitochondrial aggregation and fusion by a programmable DNA binder.

Longyi Zhu, Yiting Shen, Shengyuan Deng, Ying Wan, Jun Luo, Yan Su, Mingxu You, Chunhai Fan, Kewei Ren.

DNA nanodevices have been feasibly applied for various chemo-biological applications, but their functions as precise regulators of intracellular organelles are still limited. Here, we report a synthetic DNA binder that can artificially induce mitochondrial aggregation and fusion in living cells. The rationally designed DNA binder consists of a long DNA chain, which is grafted with multiple mitochondria-targeting modules. Our results indicated that the DNA binder-induced in situ self-assembly of mitochondria can be used to successfully repair ROS-stressed neuron cells. Meanwhile, this DNA binder design is highly programmable. Customized molecular switches can be easily implanted to further achieve stimuli-triggered mitochondrial aggregation and fusion inside living cells. We believe this new type of DNA regulator system will become a powerful chemo-biological tool for subcellular manipulation and precision therapy.

DOI: https://doi.org/10.1039/d2sc07095b
Life Sci. 2023 Aug 02. pii: S0024-3205(23)00630-6. [Epub ahead of print] 121995

Targeting calcium homeostasis and impaired inter-organelle crosstalk as a potential therapeutic approach in Parkinson's disease.

Satinder Kaur, Abhishek Sehrawat, Sarabjit Singh Mastana, Ramesh Kandimalla, Pushpender Kumar Sharma, Gurjit Kaur Bhatti, Jasvinder Singh Bhatti.

  Parkinson's disease (PD) is a progressive neurodegenerative disorder characterized by the loss of dopaminergic neurons in the substantia nigra pars compacta, leading to motor symptoms such as tremors, rigidity, and bradykinesia. Current therapeutic strategies for PD are limited and mainly involve symptomatic relief, with no available treatment for the underlying causes of the disease. Therefore, there is a need for new therapeutic approaches that target the underlying pathophysiological mechanisms of PD. Calcium homeostasis is an essential process for maintaining proper cellular function and survival, including neuronal cells. Calcium dysregulation is also observed in various organelles, including the endoplasmic reticulum (ER), mitochondria, and lysosomes, resulting in organelle dysfunction and impaired inter-organelle communication. The ER, as the primary calcium reservoir, is responsible for folding proteins and maintaining calcium homeostasis, and its dysregulation can lead to protein misfolding and neurodegeneration. The crosstalk between ER and mitochondrial calcium signaling is disrupted in PD, leading to neuronal dysfunction and death. In addition, a lethal network of calcium cytotoxicity utilizes mitochondria, ER and lysosome to destroy neurons. This review article focused on the complex role of calcium dysregulation and its role in aggravating functioning of organelles in PD so as to provide new insight into therapeutic strategies for treating this disease. Targeting dysfunctional organelles, such as the ER and mitochondria and lysosomes and whole network of calcium dyshomeostasis can restore proper calcium homeostasis and improve neuronal function. Additionally targeting calcium dyshomeostasis that arises from miscommunication between several organelles can be targeted so that therapeutic effects of calcium are realised in whole cellular territory.

Keywords:  Calcium homeostasis; ER-mitochondria calcium signaling; Organelle crosstalk; Parkinson's disease; Therapeutic strategies

DOI:  https://doi.org/10.1016/j.lfs.2023.121995
Proc Natl Acad Sci U S A. 2023 Aug 08. 120(32): e2303402120

Genome-wide kinase-MAM interactome screening reveals the role of CK2A1 in MAM Ca2+ dynamics linked to DEE66.

Truong Thi My Nhung, Nguyen Phuoc Long, Tran Diem Nghi, Yeongjun Suh, Nguyen Hoang Anh, Cheol Woon Jung, Hong Minh Triet, Minkyo Jung, Youngsik Woo, Jinyeong Yoo, Sujin Noh, Soo Jeong Kim, Su Been Lee, Seongoh Park, Gary Thomas, Thomas Simmen, Jiyoung Mun, Hyun-Woo Rhee, Sung Won Kwon, Sang Ki Park.

  The endoplasmic reticulum (ER) and mitochondria form a unique subcellular compartment called mitochondria-associated ER membranes (MAMs). Disruption of MAMs impairs Ca2+ homeostasis, triggering pleiotropic effects in the neuronal system. Genome-wide kinase-MAM interactome screening identifies casein kinase 2 alpha 1 (CK2A1) as a regulator of composition and Ca2+ transport of MAMs. CK2A1-mediated phosphorylation of PACS2 at Ser207/208/213 facilitates MAM localization of the CK2A1-PACS2-PKD2 complex, regulating PKD2-dependent mitochondrial Ca2+ influx. We further reveal that mutations of PACS2 (E209K and E211K) associated with developmental and epileptic encephalopathy-66 (DEE66) impair MAM integrity through the disturbance of PACS2 phosphorylation at Ser207/208/213. This, in turn, causes the reduction of mitochondrial Ca2+ uptake and the dramatic increase of the cytosolic Ca2+ level, thereby, inducing neurotransmitter release at the axon boutons of glutamatergic neurons. In conclusion, our findings suggest a molecular mechanism that MAM alterations induced by pathological PACS2 mutations modulate Ca2+-dependent neurotransmitter release.

Keywords:  calcium; casein kinase 2; developmental and epileptic encephalopathy-66; mitochondria-associated ER membranes

DOI:  https://doi.org/10.1073/pnas.2303402120
J Mol Endocrinol. 2023 Jul 01. pii: JME-23-0059. [Epub ahead of print]

Inhibition of mitochondrial fission and protein kinase R improves progesterone in placental stress.

Umut Kerem KolaÇ.

Placenta synthesizes hormones that play a vital role in adapting maternal physiology and supporting fetal growth. This study aimed to explore the link between progesterone, a key steroid hormone produced by placenta, and mitochondrial fission and protein kinase R through use of chemical inhibition in trophoblasts subjected to endotoxin lipopolysaccharide and double-stranded RNA analog polyinosinic-polycytidylic acid stress. Expressions of protein kinase R, dynamin related protein1, mitochondrial fission protein1 and heat shock protein 60 were determined by applying lipopolysaccharide and polyinosinic-polycytidylic acid to BeWo trophoblast cells. Next, cells were treated with protein kinase R inhibitor 2-aminopurine and mitochondrial division inhibitor1 to examine changes in progesterone levels and expression levels of proteins and mRNAs involved in progesterone biosynthesis. Last, effect of 2-aminopurine on mitochondrial fission was determined by immunoblotting and qPCR. Mitochondrial structural changes were also examined by transmission electron microscopy. Lipopolysaccharide and polyinosinic-polycytidylic acid stimulation induced mitochondrial fission, activated protein kinase R but decreased heat shock protein 60 levels and progesterone synthesis. Chemical inhibition of mitochondrial fission elevated progesterone synthesis and protein and mRNA levels of genes involved in progesterone biosynthesis. Inhibition of protein kinase R with 2-aminopurine prevented lipopolysaccharide and polyinosinic-polycytidylic acid induced mitochondrial fission and increased progesterone biosynthesis. Use of chemical inhibitors to treat placental stress caused by pathogens has potential to stabilize the production of progesterone. The study reveals that inhibiting mitochondrial fragmentation and reducing activity of stress kinase protein kinase R in syncytiotrophoblasts leads to an increase in progesterone synthesis when exposed to lipopolysaccharide and polyinosinic-polycytidylic acid.

DOI: https://doi.org/10.1530/JME-23-0059
Front Neurol. 2023 ;14 1179823

The effects of general anesthetics on mitochondrial structure and function in the developing brain.

Kaley Hogarth, Doorsa Tarazi, Jason T Maynes.

  The use of general anesthetics in modern clinical practice is commonly regarded as safe for healthy individuals, but exposures at the extreme ends of the age spectrum have been linked to chronic cognitive impairments and persistent functional and structural alterations to the nervous system. The accumulation of evidence at both the epidemiological and experimental level prompted the addition of a warning label to inhaled anesthetics by the Food and Drug Administration cautioning their use in children under 3 years of age. Though the mechanism by which anesthetics may induce these detrimental changes remains to be fully elucidated, increasing evidence implicates mitochondria as a potential primary target of anesthetic damage, meditating many of the associated neurotoxic effects. Along with their commonly cited role in energy production via oxidative phosphorylation, mitochondria also play a central role in other critical cellular processes including calcium buffering, cell death pathways, and metabolite synthesis. In addition to meeting their immense energy demands, neurons are particularly dependent on the proper function and spatial organization of mitochondria to mediate specialized functions including neurotransmitter trafficking and release. Mitochondrial dependence is further highlighted in the developing brain, requiring spatiotemporally complex and metabolically expensive processes such as neurogenesis, synaptogenesis, and synaptic pruning, making the consequence of functional alterations potentially impactful. To this end, we explore and summarize the current mechanistic understanding of the effects of anesthetic exposure on mitochondria in the developing nervous system. We will specifically focus on the impact of anesthetic agents on mitochondrial dynamics, apoptosis, bioenergetics, stress pathways, and redox homeostasis. In addition, we will highlight critical knowledge gaps, pertinent challenges, and potential therapeutic targets warranting future exploration to guide mechanistic and outcomes research.

Keywords:  anesthesia; developing brain; mitochondria; mitochondrial dysfunction; neurotoxicity

DOI:  https://doi.org/10.3389/fneur.2023.1179823
Biochem Biophys Res Commun. 2023 Jul 24. pii: S0006-291X(23)00902-6. [Epub ahead of print]676 182-189

The GLI2/CDH6 axis enhances migration, invasion and mitochondrial fission of stomach adenocarcinoma cells.

Guang-Yi Liu, Huan Wang, Rui Ran, Yi-Cheng Wang, Yang Li.

  It has been reported that cadherin 6 (CDH6) upregulation is associated with enhanced epithelial-to-mesenchymal transition (EMT) in several types of solid tumor cells. The current study aimed to explore the effect of CDH6 on the migration and invasion of stomach adenocarcinoma (STAD) cells, the transcription factors involved in CDH6 dysregulation and their effect on mitochondrial fission. Bioinformatics analysis was performed using data extracted from the Genotype-Tissue Expression Project, the Cancer Genome Atlas and Kaplan-Meier plotter. AGS and HGC27 cells were used to establish an in vitro STAD cell model. The results showed that higher CDH6 expression was associated with significantly shorter overall survival in patients with STAD. In addition, CDH6 overexpression promoted wound healing, enhanced the invasion ability of tumor cells and increased mitochondrial fission. Glioma-associated oncogene family zinc finger 2 (GLI2) could bind to the CDH6 promoter and activate its transcription. Fluorescent labeling also showed that GLI2 overexpression promoted mitochondrial fission. However, CDH6 silencing significantly reduced mitochondrial fragmentation. Besides, GLI2 overexpression notably upregulated phosphorylated-focal adhesion kinase and dynamin-related protein 1. However, the above effects were largely abrogated by CDH6 knockdown. In conclusion, the present study suggested that the novel GLI2/CDH6 axis could enhance the migration, invasion and mitochondrial fission of STAD cells.

Keywords:  CDH6; GLI2; Mitochondrial fission; STAD

DOI:  https://doi.org/10.1016/j.bbrc.2023.07.038
Front Immunol. 2023 ;14 1197289

End-binding protein 1 regulates the metabolic fate of CD4+ T lymphoblasts and Jurkat T cells and the organization of the mitochondrial network.

Álvaro Gómez-Morón, Silvia Requena, Clara Pertusa, Marta Lozano-Prieto, Diego Calzada-Fraile, Camila Scagnetti, Inés Sánchez-García, Ana Adela Calero-García, Manuel Izquierdo, Noa B Martín-Cófreces.

  The organization of the mitochondrial network is relevant for the metabolic fate of T cells and their ability to respond to TCR stimulation. This arrangement depends on cytoskeleton dynamics in response to TCR and CD28 activation, which allows the polarization of the mitochondria through their change in shape, and their movement along the microtubules towards the immune synapse. This work focus on the role of End-binding protein 1 (EB1), a protein that regulates tubulin polymerization and has been previously identified as a regulator of intracellular transport of CD3-enriched vesicles. EB1-interferred cells showed defective intracellular organization and metabolic strength in activated T cells, pointing to a relevant connection of the cytoskeleton and metabolism in response to TCR stimulation, which leads to increased AICD. By unifying the organization of the tubulin cytoskeleton and mitochondria during CD4+ T cell activation, this work highlights the importance of this connection for critical cell asymmetry together with metabolic functions such as glycolysis, mitochondria respiration, and cell viability.

Keywords:  EB1; T cell receptor; cell asymmetry; cytoskeleton; glycolysis; mitochondria

DOI:  https://doi.org/10.3389/fimmu.2023.1197289
Eur J Pharmacol. 2023 Aug 01. pii: S0014-2999(23)00451-X. [Epub ahead of print] 175939

Differential temporal therapies with pharmacologically targeted mitochondrial fission/fusion protect the brain against acute myocardial ischemia-reperfusion injury in prediabetic rats: The crosstalk between mitochondrial apoptosis and inflammation.

Chayodom Maneechote, Hiranya Pintana, Sasiwan Kerdphoo, Sornram Janjek, Nipon Chattipakorn, Siriporn C Chattipakorn.

  An imbalance of brain mitochondrial dynamics, increases in brain inflammation and apoptosis, and increasing cognitive dysfunction, have been reported as being associated with prediabetes and myocardial ischemia-reperfusion (IR) injury. Since inhibiting mitochondrial fission with Mdivi-1 or promoting fusion with M1 had cardioprotective effects in myocardial IR injury and obesity, the neuroprotective roles of Mdivi-1 and M1 when administered at different time points of myocardial IR injury in obese prediabetes have never been determined. Ninety-six male Wistar rats were fed with either a normal (ND: n = 8) or a high-fat diet to induce prediabetes (HFD: n = 88) for 12 weeks. At week 13, all rats were subjected to left anterior descending coronary artery ligation for 30 min, followed by reperfusion for 120 min. HFD rats were randomly divided into 10 groups and assigned into either a pre-ischemic group treated with vehicle (HFV), pre-ischemic, during-ischemic, or onset of reperfusion groups treated with either Mdivi-1 (MDV), M1, or combined (COM). Heart function was examined invasively, with the heart being terminated to investigate myocardial infarction. Brains were collected to determine mitochondrial functions, inflammation, apoptosis, and pathological markers. Mdivi-1, M1, and COM treatment at different periods exerted cardioprotection against myocardial IR injury in HFD-fed rats by reducing infarct size and left ventricular dysfunction. All interventions also improved all brain pathologies against myocardial IR injury in prediabetic rats. These findings suggest that differential temporal modulation of mitochondrial dynamics may be appropriate regimens for preventing heart and brain complications after myocardial IR injury in obese prediabetes.

Keywords:  Brain pathology; Mitochondrial dynamics; Myocardial ischemia-reperfusion injury; Obesity; Prediabetes

DOI:  https://doi.org/10.1016/j.ejphar.2023.175939