bims-mikwok 2023-09-10 papers

bims-mikwok

Biomed News

on Mitochondrial quality control

Issue of 2023‒09‒10
eight papers selected by
Gavin McStay, Liverpool John Moores University

Lysosomes mediate the mitochondrial UPR via mTORC1-dependent ATF4 phosphorylation.
Damaged mitochondria recruit the effector NEMO to activate NF-κB signaling.
The Orf9b protein of SARS-CoV-2 modulates mitochondrial protein biogenesis.
CLPX regulates mitochondrial fatty acid β-oxidation in liver cells.
Exploring a new mechanism between lactate and VSMC calcification: PARP1/POLG/UCP2 signaling pathway and imbalance of mitochondrial homeostasis.
Nanomicelle curcumin-induced testicular toxicity: Implications for altered mitochondrial biogenesis and mitophagy following redox imbalance.
Yi Mai granules improve energy supply of endothelial cells in atherosclerosis rat model via miRNA-125a-5p regulating mitochondrial autophagy through Pink1-Mfn2-Parkin pathway.
ROS-mediated mitophagy and necroptosis regulate osteocytes death caused by TCP particles in MLO-Y4 cells.

Cell Discov. 2023 Sep 07. 9(1): 92

Lysosomes mediate the mitochondrial UPR via mTORC1-dependent ATF4 phosphorylation.

Terytty Yang Li, Qi Wang, Arwen W Gao, Xiaoxu Li, Yu Sun, Adrienne Mottis, Minho Shong, Johan Auwerx.

Lysosomes are central platforms for not only the degradation of macromolecules but also the integration of multiple signaling pathways. However, whether and how lysosomes mediate the mitochondrial stress response (MSR) remain largely unknown. Here, we demonstrate that lysosomal acidification via the vacuolar H+-ATPase (v-ATPase) is essential for the transcriptional activation of the mitochondrial unfolded protein response (UPRmt). Mitochondrial stress stimulates v-ATPase-mediated lysosomal activation of the mechanistic target of rapamycin complex 1 (mTORC1), which then directly phosphorylates the MSR transcription factor, activating transcription factor 4 (ATF4). Disruption of mTORC1-dependent ATF4 phosphorylation blocks the UPRmt, but not other similar stress responses, such as the UPRER. Finally, ATF4 phosphorylation downstream of the v-ATPase/mTORC1 signaling is indispensable for sustaining mitochondrial redox homeostasis and protecting cells from ROS-associated cell death upon mitochondrial stress. Thus, v-ATPase/mTORC1-mediated ATF4 phosphorylation via lysosomes links mitochondrial stress to UPRmt activation and mitochondrial function resilience.

DOI: https://doi.org/10.1038/s41421-023-00589-1
Mol Cell. 2023 Sep 07. pii: S1097-2765(23)00641-X. [Epub ahead of print]83(17): 3188-3204.e7

Damaged mitochondria recruit the effector NEMO to activate NF-κB signaling.

Olivia Harding, Elisabeth Holzer, Julia F Riley, Sascha Martens, Erika L F Holzbaur.

  Failure to clear damaged mitochondria via mitophagy disrupts physiological function and may initiate damage signaling via inflammatory cascades, although how these pathways intersect remains unclear. We discovered that nuclear factor kappa B (NF-κB) essential regulator NF-κB effector molecule (NEMO) is recruited to damaged mitochondria in a Parkin-dependent manner in a time course similar to recruitment of the structurally related mitophagy adaptor, optineurin (OPTN). Upon recruitment, NEMO partitions into phase-separated condensates distinct from OPTN but colocalizing with p62/SQSTM1. NEMO recruitment, in turn, recruits the active catalytic inhibitor of kappa B kinase (IKK) component phospho-IKKβ, initiating NF-κB signaling and the upregulation of inflammatory cytokines. Consistent with a potential neuroinflammatory role, NEMO is recruited to mitochondria in primary astrocytes upon oxidative stress. These findings suggest that damaged, ubiquitinated mitochondria serve as an intracellular platform to initiate innate immune signaling, promoting the formation of activated IKK complexes sufficient to activate NF-κB signaling. We propose that mitophagy and NF-κB signaling are initiated as parallel pathways in response to mitochondrial stress.

Keywords:  ALS; NEMO; NF-κB; NF-κB effector molecule; Parkin; Parkinson’s disease; SQSTM1/p62; amyotrophic lateral sclerosis; cell stress; innate immunity; mitophagy; neurodegeneration; neuroinflammation; optineurin nuclear factor kappa B; phase separation; ubiquitin

DOI:  https://doi.org/10.1016/j.molcel.2023.08.005
J Cell Biol. 2023 Oct 02. pii: e202303002. [Epub ahead of print]222(10):

The Orf9b protein of SARS-CoV-2 modulates mitochondrial protein biogenesis.

Svenja Lenhard, Sarah Gerlich, Azkia Khan, Saskia Rödl, Jan-Eric Bökenkamp, Esra Peker, Christine Zarges, Janina Faust, Zuzana Storchova, Markus Räschle, Jan Riemer, Johannes M Herrmann.

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) expresses high amounts of the protein Orf9b to target the mitochondrial outer membrane protein Tom70. Tom70 serves as an import receptor for mitochondrial precursors and, independently of this function, is critical for the cellular antiviral response. Previous studies suggested that Orf9b interferes with Tom70-mediated antiviral signaling, but its implication for mitochondrial biogenesis is unknown. In this study, we expressed Orf9b in human HEK293 cells and observed an Orf9b-mediated depletion of mitochondrial proteins, particularly in respiring cells. To exclude that the observed depletion was caused by the antiviral response, we generated a yeast system in which the function of human Tom70 could be recapitulated. Upon expression of Orf9b in these cells, we again observed a specific decline of a subset of mitochondrial proteins and a general reduction of mitochondrial volume. Thus, the SARS-CoV-2 virus is able to modulate the mitochondrial proteome by a direct effect of Orf9b on mitochondrial Tom70-dependent protein import.

DOI: https://doi.org/10.1083/jcb.202303002
J Biol Chem. 2023 Sep 01. pii: S0021-9258(23)02238-X. [Epub ahead of print] 105210

CLPX regulates mitochondrial fatty acid β-oxidation in liver cells.

Ko Suzuki, Yoshiko Kubota, Kiriko Kaneko, Costantine Chasama Kamata, Kazumichi Furuyama.

  Mitochondrial fatty acid oxidation (β-oxidation) is an essential metabolic process for energy production in eukaryotic cells, but the regulatory mechanisms of this pathway are largely unknown. In the present study, we found that several enzymes involved in β-oxidation are associated with CLPX, the AAA+ unfoldase that is a component of the mitochondrial matrix protease ClpXP. The suppression of CLPX expression increased β-oxidation activity in the HepG2 cell line and in primary human hepatocytes without glucagon treatment. However, the protein levels of enzymes involved in β-oxidation did not significantly increase in CLPX-deleted HepG2 cells (CLPX-KO cells). Coimmunoprecipitation experiments revealed that the protein level in the immunoprecipitates of each antibody changed after the treatment of wild-type cells with glucagon, and a part of these changes was also observed in the comparison of wild-type and CLPX-KO cells without glucagon treatment. Although the exogenous expression of wild-type or ATP-hydrolysis mutant CLPX suppressed β-oxidation activity in CLPX-KO cells, glucagon treatment induced β-oxidation activity only in CLPX-KO cells expressing wild-type CLPX. These results suggest that the dissociation of CLPX from its target proteins is essential for the induction of β-oxidation in HepG2 cells. Moreover, specific phosphorylation of AMP-activated protein kinase (AMPK) and a decrease in the expression of acetyl-CoA carboxylase 2 were observed in CLPX-KO cells, suggesting that CLPX might participate in the regulation of the cytosolic signaling pathway for β-oxidation. The mechanism for AMPK phosphorylation remains elusive; however, our results uncovered the hitherto unknown role of CLPX in mitochondrial β-oxidation in human liver cells.

Keywords:  CLPX; beta-oxidation; glucagon; hepatocyte; mitochondria; protein‒protein interaction

DOI:  https://doi.org/10.1016/j.jbc.2023.105210
Cell Death Dis. 2023 Sep 07. 14(9): 598

Exploring a new mechanism between lactate and VSMC calcification: PARP1/POLG/UCP2 signaling pathway and imbalance of mitochondrial homeostasis.

Yi Zhu, Jia-Li Zhang, Xue-Jiao Yan, Yuan Ji, Fang-Fang Wang.

Lactate leads to the imbalance of mitochondria homeostasis, which then promotes vascular calcification. PARP1 can upregulate osteogenic genes and accelerate vascular calcification. However, the relationship among lactate, PARP1, and mitochondrial homeostasis is unclear. The present study aimed to explore the new molecular mechanism of lactate to promote VSMC calcification by evaluating PARP1 as a breakthrough molecule. A coculture model of VECs and VSMCs was established, and the model revealed that the glycolysis ability and lactate production of VECs were significantly enhanced after incubation in DOM. Osteogenic marker expression, calcium deposition, and apoptosis in VSMCs were decreased after lactate dehydrogenase A knockdown in VECs. Mechanistically, exogenous lactate increased the overall level of PARP and PARylation in VSMCs. PARP1 knockdown inhibited Drp1-mediated mitochondrial fission and partially restored PINK1/Parkin-mediated mitophagy, thereby reducing mitochondrial oxidative stress. Moreover, lactate induced the translocation of PARP1 from the nucleus to the mitochondria, which then combined with POLG and inhibited POLG-mediated mitochondrial DNA synthesis. This process led to the downregulation of mitochondria-encoded genes, disturbance of mitochondrial respiration, and inhibition of oxidative phosphorylation. The knockdown of PARP1 could partially reverse the damage of mitochondrial gene expression and function caused by lactate. Furthermore, UCP2 was upregulated by the PARP1/POLG signal, and UCP2 knockdown inhibited Drp1-mediated mitochondrial fission and partially recovered PINK1/Parkin-mediated mitophagy. Finally, UCP2 knockdown in VSMCs alleviated DOM-caused VSMC calcification in the coculture model. The study results thus suggest that upregulated PARP1 is involved in the mechanism through which lactate accelerates VSMC calcification partly via POLG/UCP2-caused unbalanced mitochondrial homeostasis.

DOI: https://doi.org/10.1038/s41419-023-06113-3
Biomed Pharmacother. 2023 Sep 01. pii: S0753-3322(23)01154-X. [Epub ahead of print]166 115363

Nanomicelle curcumin-induced testicular toxicity: Implications for altered mitochondrial biogenesis and mitophagy following redox imbalance.

Zafer Yönden, Farzaneh Bonyadi, Yavar Yousefi, Amin Daemi, Seyyedeh Touran Hosseini, Sana Moshari.

  The purpose of this study was to examine the effects of nano-micelle curcumin (NMC)-induced redox imbalance on mitochondrial biogenesis and mitophagy. For this purpose, 24 mature male Wistar rats were divided into control and NMC-received groups (7.5, 15, and 30 mg/kg) groups. After 48 days, the Nrf1, Nrf2, and SOD (Cu/Zn) expression levels, as well as GSH/GSSG, NADP+ /NADPH relative balances (elements involved in redox homeostasis) were analyzed. Moreover, to explore the effect of NMC on mitochondrial biogenesis, the expression levels of Mfn1, Mfn2, OPA1, Fis1, and Drp1 were investigated. Finally, the expression levels of Parkin/PARK and PINK (genes involved in mitochondrial quality control), as well as LC3-I/II (mitophagy marker), were analyzed. Observations showed that NMC, dose-dependently, altered GSH/GSSG, NADP+ /NADPH relative balances, suppressed SOD expression and diminished its biochemical level, and repressed Nrf1 and Nrf2 expression levels. Moreover, it could change the Mfn1, Mfn2, OPA1, Fis1, and Drp1 expression pattern and stimulate the Parkin/PARK and PINK as well as LC3-I/II expression levels, dose-dependently. In conclusion, chronic and high-dose NMC is able to suppress the redox capacity by down-regulating the Nrf1 and Nrf2 expression. Finally, at high-dose levels, it is able to trigger mitophagy signaling in the testicles.

Keywords:  Biogenesis; Mitochondria; Mitophagy; Nano-micelle curcumin; Oxidative stress

DOI:  https://doi.org/10.1016/j.biopha.2023.115363
J Ethnopharmacol. 2023 Sep 05. pii: S0378-8741(23)00982-0. [Epub ahead of print] 117114

Yi Mai granules improve energy supply of endothelial cells in atherosclerosis rat model via miRNA-125a-5p regulating mitochondrial autophagy through Pink1-Mfn2-Parkin pathway.

De Zhao Kong, Peng Sun, Yi Lu, Ye Yang, Dong Yu Min, Si Cheng Zheng, Yi Yang, Zhe Zhang, Guan Lin Yang, Jun Wen Jiang.

  ETHNOPHARMACOLOGICAL RELEVANCE: Yi Mai granules (YMG) consists of two classic Chinese medicine formulas used to treat cardiovascular disease for centuries. The Pink1-Mfn2-Parkin pathway, a well-recognized mechanism that mediates mitochondrial autophagy, plays a big part in mitochondrial quality control and the maintenance of heart function. However, the effects of YMG on endothelial dysfunction and mitochondrial autophagy remain unknown.AIM OF THE STUDY: Here, we focused on the therapeutic effects of YMG in improving mitochondrial autophagy and the mechanism of YMG against cardiovascular disease.
MATERIALS AND METHODS: In this study, rats were fed high-fat diet (HFD) for 21 weeks and were given high, medium, and low doses of YMG in stomach. The open field test was used to evaluate the rats' behavior. Atherosclerotic plaques, blood lipids, and cytokine levels were measured. Mitochondrial autophagy changes were observed by Transmission electron microscope (TEM). Human umbilical vein endothelial cells (HUVECs) were injured by angiotensinⅡ(AngⅡ) and were given high, medium, and low doses of YMG medicated serum in cell culture medium. Pink1-Mfn2-Parkin expression and miRNA 125a-5p expression were measured by RT-PCR and Western blot.
RESULTS: We demonstrated that the atherosclerosis model group tended to exhibit reduced vitality behaviors. We proved that the atherosclerosis model group showed obvious atherosclerotic plaques, endothelial cells destruction, and high level of blood lipid and cytokines (including hs-CRP, ET). Mitochondria were reduced, and mitophagy was inhibited in aortic cells of the model group. MiRNA-125a-5p was up-regulated; at the same time, Pink1-Mfn2-Parkin-mediated mitochondrial autophagy was prevented. We also proved that AngⅡinjured HUVEC showed obviously low mRNA levels of Pink1, Mfn2, and Parkin. Interestingly, we found that miRNA-125a-5p was significantly down regulated in Ang II-induced HUVECs. In addition, YMG reversed the low expression of Pink1, Mfn2, and Parkin induced by AngⅡand miRNA-125a-5p mimic.
CONCLUSION: Our finding indicated that Pink1-Mfn2-Parkin-mediated mitochondrial autophagy plays a crucial role in alleviating atherosclerosis. YMG alleviated atherosclerosis by potentially activating mitochondrial autophagy may via miRNA-125a-5p, regulating Pink1-Mfn2-Parkin pathway, and regulating proinflammatory factors, vasoconstriction cytokine, and blood lipids.

Keywords:  Atherosclerosis; Mitochondria autophagy; Pink1-Mfn2-parkin; Yi mai granules (YMG); miRNA125a

DOI:  https://doi.org/10.1016/j.jep.2023.117114
Toxicology. 2023 Sep 05. pii: S0300-483X(23)00214-7. [Epub ahead of print] 153627

ROS-mediated mitophagy and necroptosis regulate osteocytes death caused by TCP particles in MLO-Y4 cells.

Pei Yang, Bingbing Xu, Ruirong Zhu, Tao Zhang, Zihan Wang, Qiao Lin, Ming Yan, Zhangsen Yu, Hongjiao Mao, Yun Zhang.

  Our previous data have revealed TCP particles caused cell death of osteocytes, comprising over 95% of all bone cells, which contribute to periprosthetic osteolysis, joint loosening and implant failure, but its mechanisms are not fully understood. Here, we reported that TCP particles inhibited cell viability of osteocytes MLO-Y4, and caused cell death. TCP particles caused mitochondrial impairment and increased expressions of LC-3 II, Parkin and PINK 1, accompanied by the elevation of autophagy flux and intracellular acidic components, the accumulation of LC-3II, PINK1 and Parkin in damaged mitochondria, and p62 reduction. The increased LC-3II expression and cell death extent were significantly enhanced by the autophagy inhibitor Baf A1, compared with Baf A1 (or TCP particles) alone, indicating that TCP particles increase autophagic flux and lead to cell even death of MLO-Y4 cells, closely associated with mitophagy. Furthermore, TCP particles induced propidium iodide (PI) uptake and the phosphorylation of RIP1, RIP3 and MLKL, thereby increasing necroptosis in MLO-Y4 cells. The pro-necroptotic effect was alleviated by the RIP1 inhibitor Nec-1 or the MLKL inhibitor NSA. Additionally, TCP particles promoted the production of intracellular reactive oxygen species (ROS) and mitochondrial ROS (mtROS), and increased TXNIP expression, but decreased protein levels of TRX1, Nrf2, HO-1 and NQO1, leading to oxidative stress. The ROS scavenger NAC remarkably reversed mitophagy and necroptosis caused by TCP particles, suggesting that ROS is responsible for mitophagy and necroptosis. Collectively, ROS-mediated mitophagy and necroptosis regulate osteocytes death caused by TCP particles in MLO-Y4 cells, which enhances osteoclastogenesis and periprosthetic osteolysis.

Keywords:  TCP particles; mitophagy; necroptosis; osteocytes; reactive oxygen species

DOI:  https://doi.org/10.1016/j.tox.2023.153627