scholarly journals OMA1 mediates local and global stress responses against protein misfolding in CHCHD10 mitochondrial myopathy

2021 ◽  
Author(s):  
Mario K. Shammas ◽  
Xiaoping Huang ◽  
Beverly P. Wu ◽  
Insung Song ◽  
Nicholas Randolph ◽  
...  
Keyword(s):  
Stress Response ◽  
Stress Responses ◽  
Protein Misfolding ◽  
Mitochondrial Membrane ◽  
Mitochondrial Protein ◽  
Inner Mitochondrial Membrane ◽  
Disease Etiology ◽  
Transport Chain ◽  
Global Stress

Mitochondrial stress triggers a response in the cell's mitochondria and nucleus, but how these stress responses are coordinated in vivo is poorly understood. Here, we characterize a family with myopathy caused by a dominant p.G58R mutation in the mitochondrial protein CHCHD10. To understand the disease etiology, we developed a novel knock-in mouse model and found that mutant CHCHD10 aggregates in affected tissues, applying a toxic protein stress to the inner mitochondrial membrane. Unexpectedly, survival of CHCHD10 knock-in mice depended on a protective stress response mediated by OMA1. The OMA1 stress response acted both locally within mitochondria, inhibiting mitochondrial fusion, and signaled outside the mitochondria, activating the integrated stress response. We additionally identified an isoform switch in the terminal complex of the electron transport chain as a novel component of this response. Our results demonstrate that OMA1 is essential for neonatal survival conditionally in the setting of inner mitochondrial membrane stress, coordinating local and global stress responses to reshape the mitochondrial network and proteome.

scholarly journals Cytoplasmic type 80S ribosomes associated with yeast mitochondria. IV. Attachment of ribosomes to the outer membrane of isolated mitochondria.

1975 ◽  
Vol 65 (1) ◽  
pp. 1-14 ◽  
Author(s):  
R E Kellems ◽  
V F Allison ◽  
R A Butow
Keyword(s):  
Outer Membrane ◽  
Mitochondrial Membrane ◽  
Close Association ◽  
Mitochondrial Protein ◽  
Inner Mitochondrial Membrane ◽  
Direct Function ◽  
Cytoplasmic Type ◽  
Cytoplasmic Ribosomes ◽  
Binding To Mitochondria

Growing yeast spheroplasts were shown to have, on the average, four times the number of cytoplasmic ribosomes in contact with the outer mitochondrial membrane compared to starved spheroplasts. Ribosomes in contact with mitochondria in the growing spheroplast preparation, like free cytoplasmic ribosomes, exist primarily as polysome structures. In the starved spheroplast preparation, both mitochondria-bound and free cytoplasmic ribosomes exist primarily as monosomes. Mitochondria isolated from growing spheroplasts in a medium containing lmM Mg++ have cytoplasmic ribosomes bound directly to the outer membrane. These ribosomes can be quantitatively removed by washing the mitochondria with 2 mM EDTA. Mitochondria from starved spheroplasts are capable of accepting either free cytoplasmic polysomes or cytoplasmic polysomes extracted from mitochondria. However, the extent of polysome binding to mitochondria was shown to be a direct function of the Mg++ concentration; a smaller percentage of the input polysomes bind as the Mg++ concentration is lowered. At 1 mM Mg++, neither free cytoplasmic nor mitochondria-bound polysomes bind to mitochondria. Nevertheless, when growing spheroplasts are broken and mitochondria isolated in medium containing 1 mM Mg++, the mitochondria are seen to have cytoplasmic ribosomes firmly attached to the outer membrane. This result, in addition to our earlier data (Kellems, R. E., and R. A. Butow. 1974. J. Biol. Chem. 249:3304-3310), support the view that cytoplasmic ribosomes attached to the outer membrane of purified mitochondria were attached in vivo. In preparations of mitochondria isolated from growing spheroplasts, ribosomes appear to be found to specific regions of the outer membrane, namely those regions which are in close association or in contact with the inner mitochondrial membrane. This is particularly evident with mitochondria in a condensed configuration. This finding suggests a mechanism whereby cytoplasmically synthesized mitochondrial protein could be transferred by a process of vectorial translation across both membranes of the organelle.

Vitamin E prevents hypobaric hypoxia-induced mitochondrial dysfunction in skeletal muscle

2007 ◽  
Vol 113 (12) ◽  
pp. 459-466 ◽  
Author(s):  
José Magalhães ◽  
Rita Ferreira ◽  
Maria J. Neuparth ◽  
Paulo J. Oliveira ◽  
Franklim Marques ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Vitamin E ◽  
Mitochondrial Dysfunction ◽  
Hypobaric Hypoxia ◽  
Mitochondrial Membrane ◽  
Mitochondrial Protein ◽  
Membrane Integrity ◽  
Outer Mitochondrial Membrane ◽  
Hypoxia Exposure

In the present study, the effect of vitamin E (α-tocopherol) on mice skeletal muscle mitochondrial dysfunction and oxidative damage induced by an in vivo acute and severe hypobaric hypoxic insult (48 h at a barometric pressure equivalent to 8500 m) has been investigated. Male mice (n=24) were randomly divided into the following four groups (n=6): control (C), hypoxia (H), vitamin E (VE; 60 mg/kg of body weight intraperitoneally, three times/week for 3 weeks) and hypoxia+VE (HVE). A significant increase in mitochondrial protein CGs (carbonyl groups) was found in the H group compared with the C group. Confirming previous observations from our group, hypoxia induced mitochondrial dysfunction, as identified by altered respiratory parameters. Hypoxia exposure increased Bax content and decreased the Bcl-2/Bax ratio, whereas Bcl-2 remained unchanged. Inner and outer mitochondrial membrane integrity were significantly affected by hypoxia exposure; however, vitamin E treatment attenuated the effect of hypoxia on mitochondrial oxidative phosphorylation and on the levels of CGs. Vitamin E supplementation also prevented the Bax and Bcl-2/Bax ratio impairments caused by hypoxia, as well as the decrease in inner and outer mitochondrial membrane integrity. In conclusion, the results suggest that vitamin E prevents the loss of mitochondrial integrity and function, as well as the increase in Bax content, which suggests that mitochondria are involved in increased cell death induced by severe hypobaric hypoxia in mice skeletal muscle.

scholarly journals mtCLIC/CLIC4, an Organellular Chloride Channel Protein, Is Increased by DNA Damage and Participates in the Apoptotic Response to p53

2002 ◽  
Vol 22 (11) ◽  
pp. 3610-3620 ◽  
Author(s):  
Ester Fernández-Salas ◽  
Kwang S. Suh ◽  
Vladislav V. Speransky ◽  
Wendy L. Bowers ◽  
Joshua M. Levy ◽  
...  
Keyword(s):  
Dna Damage ◽  
Chloride Channel ◽  
Chloride Channels ◽  
Mitochondrial Membrane ◽  
Cellular Response ◽  
Mitochondrial Protein ◽  
Inner Mitochondrial Membrane ◽  
Necrosis Factor Alpha ◽  
Channel Protein ◽  
Factor Alpha

ABSTRACT mtCLIC/CLIC4 (referred to here as mtCLIC) is a p53- and tumor necrosis factor alpha-regulated cytoplasmic and mitochondrial protein that belongs to the CLIC family of intracellular chloride channels. mtCLIC associates with the inner mitochondrial membrane. Dual regulation of mtCLIC by two stress response pathways suggested that this chloride channel protein might contribute to the cellular response to cytotoxic stimuli. DNA damage or overexpression of p53 upregulates mtCLIC and induces apoptosis. Overexpression of mtCLIC by transient transfection reduces mitochondrial membrane potential, releases cytochrome c into the cytoplasm, activates caspases, and induces apoptosis. mtCLIC is additive with Bax in inducing apoptosis without a physical association of the two proteins. Antisense mtCLIC prevents the increase in mtCLIC levels and reduces apoptosis induced by p53 but not apoptosis induced by Bax, suggesting that the two proapoptotic proteins function through independent pathways. Our studies indicate that mtCLIC, like Bax, Noxa, p53AIP1, and PUMA, participates in a stress-induced death pathway converging on mitochondria and should be considered a target for cancer therapy through genetic or pharmacologic approaches.

Dynamic organization of the mitochondrial protein import machinery

2016 ◽  
Vol 397 (11) ◽  
pp. 1097-1114 ◽  
Author(s):  
Sebastian P. Straub ◽  
Sebastian B. Stiller ◽  
Nils Wiedemann ◽  
Nikolaus Pfanner
Keyword(s):  
Mitochondrial Membrane ◽  
Protein Import ◽  
Mitochondrial Protein ◽  
Membrane Dynamics ◽  
Intermembrane Space ◽  
Mitochondrial Protein Import ◽  
Precursor Proteins ◽  
Dynamic Cooperation

Abstract Mitochondria contain elaborate machineries for the import of precursor proteins from the cytosol. The translocase of the outer mitochondrial membrane (TOM) performs the initial import of precursor proteins and transfers the precursors to downstream translocases, including the presequence translocase and the carrier translocase of the inner membrane, the mitochondrial import and assembly machinery of the intermembrane space, and the sorting and assembly machinery of the outer membrane. Although the protein translocases can function as separate entities in vitro, recent studies revealed a close and dynamic cooperation of the protein import machineries to facilitate efficient transfer of precursor proteins in vivo. In addition, protein translocases were found to transiently interact with distinct machineries that function in the respiratory chain or in the maintenance of mitochondrial membrane architecture. Mitochondrial protein import is embedded in a regulatory network that ensures protein biogenesis, membrane dynamics, bioenergetic activity and quality control.

scholarly journals Translational induction of ATF4 during integrated stress response requires noncanonical initiation factors eIF2D and DENR

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Deepika Vasudevan ◽  
Sarah D. Neuman ◽  
Amy Yang ◽  
Lea Lough ◽  
Brian Brown ◽  
...  
Keyword(s):  
Stress Response ◽  
Er Stress ◽  
Stress Responses ◽  
Rna Binding ◽  
Open Reading Frames ◽  
Binding Motif ◽  
Integrated Stress Response ◽  
Developmental Defects ◽  
Initiation Factors

Abstract The Integrated Stress Response (ISR) helps metazoan cells adapt to cellular stress by limiting the availability of initiator methionyl-tRNA for translation. Such limiting conditions paradoxically stimulate the translation of ATF4 mRNA through a regulatory 5′ leader sequence with multiple upstream Open Reading Frames (uORFs), thereby activating stress-responsive gene expression. Here, we report the identification of two critical regulators of such ATF4 induction, the noncanonical initiation factors eIF2D and DENR. Loss of eIF2D and DENR in Drosophila results in increased vulnerability to amino acid deprivation, susceptibility to retinal degeneration caused by endoplasmic reticulum (ER) stress, and developmental defects similar to ATF4 mutants. eIF2D requires its RNA-binding motif for regulation of 5′ leader-mediated ATF4 translation. Consistently, eIF2D and DENR deficient human cells show impaired ATF4 protein induction in response to ER stress. Altogether, our findings indicate that eIF2D and DENR are critical mediators of ATF4 translational induction and stress responses in vivo.

scholarly journals The CpxQ sRNA Negatively Regulates Skp To Prevent Mistargeting of β-Barrel Outer Membrane Proteins into the Cytoplasmic Membrane

mBio ◽  
2016 ◽  
Vol 7 (2) ◽  
Author(s):  
Marcin Grabowicz ◽  
Daria Koren ◽  
Thomas J. Silhavy
Keyword(s):  
Stress Response ◽  
Membrane Proteins ◽  
Outer Membrane ◽  
Protein Misfolding ◽  
Outer Membrane Proteins ◽  
Inner Membrane ◽  
Bam Complex ◽  
Envelope Stress ◽  
Periplasmic Chaperone

ABSTRACT The promoter most strongly induced upon activation of the Cpx two-component envelope stress response is the cpxP promoter. The 3′ untranscribed region (UTR) of the cpxP transcript is shown to produce a small RNA (sRNA), CpxQ. We investigated the role of CpxQ in combating envelope stress. Remarkably, the two effectors specified by the transcript are deployed to combat distinct stresses in different cellular compartments. CpxP acts in both a regulatory negative-feedback loop and as an effector that combats periplasmic protein misfolding. We find that CpxQ combats toxicity at the inner membrane (IM) by downregulating the synthesis of the periplasmic chaperone Skp. Our data indicate that this regulation prevents Skp from inserting β-barrel outer membrane proteins (OMPs) into the IM, a lethal event that likely collapses the proton motive force. Our findings suggest that Skp can fold and directly insert OMPs into a lipid bilayer in vivo without the aid of the Bam complex. IMPORTANCE Skp is a well-characterized periplasmic chaperone that binds unfolded OMPs. Surprisingly, we find that Skp can catalyze the folding and mistargeting of OMPs into the inner membrane without the aid of the other cellular proteins that normally assemble OMPs. Several OMPs function as diffusion pores. Accordingly, their mistargeting is lethal because it depolarizes the inner membrane. We show that the most highly expressed transcript of the Cpx stress response produces an sRNA from the 3′ UTR, CpxQ, which combats this potential toxicity by downregulating Skp production. Defects in OMP assembly trigger the σ E response to upregulate factors, including Skp, that promote OMP folding. The Cpx response downregulates σ E . Our findings reveal that this heretofore puzzling hierarchy exists to protect the inner membrane.

scholarly journals OM-MSCs Alleviate the Golgi Apparatus Stress Response following Cerebral Ischemia/Reperfusion Injury via the PEDF-PI3K/Akt/mTOR Signaling Pathway

2021 ◽  
Vol 2021 ◽  
pp. 1-19
Author(s):  
Jialin He ◽  
Jianyang Liu ◽  
Yan Huang ◽  
Xiangqi Tang ◽  
Han Xiao ◽  
...  
Keyword(s):  
Ischemic Stroke ◽  
Stress Response ◽  
Cerebral Ischemia ◽  
Stress Responses ◽  
Ischemia Reperfusion Injury ◽  
Ischemia Reperfusion ◽  
Cerebral Ischemia Reperfusion ◽  
Cerebral Ischemia Reperfusion Injury

The mechanism of Golgi apparatus (GA) stress responses mediated by GOLPH3 has been widely studied in ischemic stroke, and the neuroprotection effect of olfactory mucosa mesenchymal stem cells (OM-MSCs) against cerebral ischemia/reperfusion injury (IRI) has been preliminarily presented. However, the exact role of OM-MSCs in the GA stress response following cerebral IRI remains to be elucidated. In the present study, we used an oxygen-glucose deprivation/reoxygenation (OGD/R) model and reversible middle cerebral artery occlusion (MCAO) model to simulate cerebral IRI in vitro and in vivo. Our results showed that the level of GOLPH3 protein, reactive oxygen species (ROS), and Ca2+ was upregulated, SPCA1 level was downregulated, and GA fragmentation was increased in ischemic stroke models, and OM-MSC treatment clearly ameliorated these GA stress responses in vitro and in vivo. Subsequently, the knockdown of PEDF in OM-MSCs using PEDF-specific siRNA further demonstrated that secretion of PEDF in OM-MSCs protected OGD/R-treated N2a cells and MCAO rats from GA stress response. Additionally, rescue experiment using specific pathway inhibitors suggested that OM-MSCs could promote the phosphorylation of the PI3K/Akt/mTOR pathway, thereby mitigating OGD/R-induced GA stress response and excessive autophagy. In conclusion, OM-MSCs minimized the GA stress response following cerebral IRI, at least partially, through the PEDF-PI3K/Akt/mTOR pathway.

scholarly journals Transmembrane BAX Inhibitor-1 Motif Containing Protein 5 (TMBIM5) Sustains Mitochondrial Structure, Shape, and Function by Impacting the Mitochondrial Protein Synthesis Machinery

Cells ◽  
2020 ◽  
Vol 9 (10) ◽  
pp. 2147
Author(s):  
Bruno Seitaj ◽  
Felicia Maull ◽  
Li Zhang ◽  
Verena Wüllner ◽  
Christina Wolf ◽  
...  
Keyword(s):  
Cell Death ◽  
Protein Synthesis ◽  
Mitochondrial Membrane ◽  
Mitochondrial Protein ◽  
Mitochondrial Protein Synthesis ◽  
Inner Mitochondrial Membrane ◽  
Mitochondrial Structure ◽  
Protein Synthesis Machinery ◽  
Atp Generation ◽  
And Function

The Transmembrane Bax Inhibitor-1 motif (TMBIM)-containing protein family is evolutionarily conserved and has been implicated in cell death susceptibility. The only member with a mitochondrial localization is TMBIM5 (also known as GHITM or MICS1), which affects cristae organization and associates with the Parkinson’s disease-associated protein CHCHD2 in the inner mitochondrial membrane. We here used CRISPR-Cas9-mediated knockout HAP1 cells to shed further light on the function of TMBIM5 in physiology and cell death susceptibility. We found that compared to wild type, TMBIM5-knockout cells were smaller and had a slower proliferation rate. In these cells, mitochondria were more fragmented with a vacuolar cristae structure. In addition, the mitochondrial membrane potential was reduced and respiration was attenuated, leading to a reduced mitochondrial ATP generation. TMBIM5 did not associate with Mic10 and Mic60, which are proteins of the mitochondrial contact site and cristae organizing system (MICOS), nor did TMBIM5 knockout affect their expression levels. TMBIM5-knockout cells were more sensitive to apoptosis elicited by staurosporine and BH3 mimetic inhibitors of Bcl-2 and Bcl-XL. An unbiased proteomic comparison identified a dramatic downregulation of proteins involved in the mitochondrial protein synthesis machinery in TMBIM5-knockout cells. We conclude that TMBIM5 is important to maintain the mitochondrial structure and function possibly through the control of mitochondrial biogenesis.

Mitochondrial ion circuits

2010 ◽  
Vol 47 ◽  
pp. 25-35 ◽  
Author(s):  
David G. Nicholls
Keyword(s):  
Electron Transport Chain ◽  
Mitochondrial Membrane ◽  
Primary Energy ◽  
Proton Leak ◽  
Primary Proton ◽  
Inner Mitochondrial Membrane ◽  
Intact Cells ◽  
Transport Chain ◽  
Proton Current ◽  
Circuit Techniques

Proton circuits across the inner mitochondrial membrane link the primary energy generators, namely the complexes of the electron transport chain, to multiple energy utilizing processes, including the ATP synthase, inherent proton leak pathways, metabolite transport and linked circuits of sodium and calcium. These mitochondrial circuits can be monitored in both isolated preparations and intact cells and, for the primary proton circuit techniques, exist to follow both the proton current and proton electrochemical potential components of the circuit in parallel experiments, providing a quantitative means of assessing mitochondrial function and, equally importantly, dysfunction.

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