bims-mitpro 2023-08-06 papers

Issue of 2023–08–06
six papers selected by
Andreas Kohler, University of Graz

Nature. 2023 Aug 01.

Central role of Tim17 in mitochondrial presequence protein translocation.

Laura F Fielden, Jakob D Busch, Sandra G Merkt, Iniyan Ganesan, Conny Steiert, Hanna B Hasselblatt, Jon V Busto, Christophe Wirth, Nicole Zufall, Sibylle Jungbluth, Katja Noll, Julia M Dung, Ludmila Butenko, Karina von der Malsburg, Hans-Georg Koch, Carola Hunte, Martin van der Laan, Nils Wiedemann.

The presequence translocase of the mitochondrial inner membrane (TIM23) represents the major route for the import of nuclear-encoded proteins into mitochondria1,2. About 60% of more than 1,000 different mitochondrial proteins are synthesised with amino-terminal targeting signals, termed presequences, which form positively charged amphiphilic α-helices3,4. TIM23 sorts the presequence proteins into the inner membrane or matrix. Various views including regulatory and coupling functions have been reported on the essential TIM23 subunit Tim175-7. We mapped the interaction of Tim17 with matrix-targeted and inner membrane-sorted preproteins during translocation in the native membrane environment. We show that Tim17 contains conserved negative charges close to the intermembrane space side of the bilayer, which are essential to initiate presequence protein translocation along a distinct transmembrane cavity of Tim17 for both classes of preproteins. The amphiphilic character of mitochondrial presequences directly matches this Tim17-dependent translocation mechanism. This mechanism permits direct lateral release of transmembrane segments of inner membrane-sorted precursors into the inner membrane.

DOI: https://doi.org/10.1038/s41586-023-06477-8

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

Mol Neurobiol. 2023 Aug 01.

Linking Heat Shock Protein 70 and Parkin in Parkinson's Disease.

Zhongting Zhao, Zheng Li, Fangning Du, Yixin Wang, Yue Wu, Kah-Leong Lim, Lin Li, Naidi Yang, Changmin Yu, Chengwu Zhang.

Parkinson's disease (PD) is a neurodegenerative disease that affects millions of elderly people worldwide and is characterized by the progressive loss of dopaminergic neurons in the substantia nigra pars compacta (SNpc). The precise mechanisms underlying the pathogenesis of PD are still not fully understood, but it is well accepted that the misfolding, aggregation, and abnormal degradation of proteins are the key causative factors of PD. Heat shock protein 70 (Hsp70) is a molecular chaperone that participates in the degradation of misfolded and aggregated proteins in living cells and organisms. Parkin, an E3 ubiquitin ligase, participates in the degradation of proteins via the proteasome pathway. Recent studies have indicated that both Hsp70 and Parkin play pivotal roles in PD pathogenesis. In this review, we focus on discussing how dysregulation of Hsp70 and Parkin leads to PD pathogenesis, the interaction between Hsp70 and Parkin in the context of PD and their therapeutic applications in PD.

Keywords: Heat shock protein 70; Parkin; Parkinson’s disease; Protein aggregation

DOI: https://doi.org/10.1007/s12035-023-03481-x

Cardiovasc Res. 2023 Jul 31. pii: cvad124. [Epub ahead of print]

FAM210A regulates mitochondrial translation and maintains cardiac mitochondrial homeostasis.

Jiangbin Wu, Kadiam C Venkata Subbaiah, Omar Hedaya, Si Chen, Joshua Munger, Wai Hong Wilson Tang, Chen Yan, Peng Yao.

AIMS: Mitochondria play a vital role in cellular metabolism and energetics and support normal cardiac function. Disrupted mitochondrial function and homeostasis cause a variety of heart diseases. Fam210a (family with sequence similarity 210 member A), a novel mitochondrial gene, is identified as a hub gene in mouse cardiac remodeling by multi-omics studies. Human FAM210A mutations are associated with sarcopenia. However, the physiological role and molecular function of FAM210A remain elusive in the heart. We aim to determine the biological role and molecular mechanism of FAM210A in regulating mitochondrial function and cardiac health in vivo.
METHODS AND RESULTS: Tamoxifen-induced αMHCMCM-driven conditional knockout of Fam210a in the mouse cardiomyocytes induced progressive dilated cardiomyopathy and heart failure, ultimately causing mortality. Fam210a deficient cardiomyocytes exhibit severe mitochondrial morphological disruption and functional decline accompanied by myofilament disarray at the late stage of cardiomyopathy. Furthermore, we observed increased mitochondrial reactive oxygen species production, disturbed mitochondrial membrane potential, and reduced respiratory activity in cardiomyocytes at the early stage before contractile dysfunction and heart failure. Multi-omics analyses indicate that FAM210A deficiency persistently activates integrated stress response (ISR), resulting in transcriptomic, translatomic, proteomic, and metabolomic reprogramming, ultimately leading to pathogenic progression of heart failure. Mechanistically, mitochondrial polysome profiling analysis shows that FAM210A loss of function compromises mitochondrial mRNA translation and leads to reduced mitochondrial encoded proteins, followed by disrupted proteostasis. We observed decreased FAM210A protein expression in human ischemic heart failure and mouse myocardial infarction tissue samples. To further corroborate FAM210A function in the heart, AAV9-mediated overexpression of FAM210A promotes mitochondrial-encoded protein expression, improves cardiac mitochondrial function, and partially rescues murine hearts from cardiac remodeling and damage in ischemia-induced heart failure.
CONCLUSION: These results suggest that FAM210A is a mitochondrial translation regulator to maintain mitochondrial homeostasis and normal cardiomyocyte contractile function. This study also offers a new therapeutic target for treating ischemic heart disease.

Keywords: FAM210A; cardiomyopathy; heart failure; integrated stress response; mRNA translation; metabolism; mitochondria; myocardial infarction

DOI: https://doi.org/10.1093/cvr/cvad124

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

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