scholarly journals MICU1 regulates mitochondrial cristae structure and function independent of the mitochondrial calcium uniporter channel

2019 ◽  
Author(s):  
Dhanendra Tomar ◽  
Manfred Thomas ◽  
Joanne F. Garbincius ◽  
Devin W. Kolmetzky ◽  
Oniel Salik ◽  
...  
Keyword(s):  
Mitochondrial Membrane ◽  
Mitochondrial Protein ◽  
Coiled Coil ◽  
Membrane Dynamics ◽  
Size Exclusion ◽  
Mitochondrial Calcium ◽  
Cellular Functions ◽  
Inner Mitochondrial Membrane ◽  
Cytochrome C Release ◽  
And Function

AbstractMICU1 is an EF-hand-containing mitochondrial protein that is essential for gating of the mitochondrial Ca2+ uniporter channel (mtCU) and is reported to interact directly with the pore-forming subunit, MCU and scaffold EMRE. However, using size-exclusion proteomics, we found that MICU1 exists in mitochondrial complexes lacking MCU. This suggests that MICU1 may have additional cellular functions independent of regulating mitochondrial Ca2+ uptake. To discern mtCU-independent MICU1 functions, we employed a proteomic discovery approach using BioID2-mediated proximity-based (<10nm) biotinylation and subsequent LC-MS detection. The expression of a MICU1-BioID2 fusion protein in MICU1-/- and MCU-/- cells allowed the identification of total vs. mtCU-independent MICU1 interactors. Bioinformatics identified the Mitochondrial Contact Site and Cristae Organizing System (MICOS) components MIC60 (encoded by the IMMT gene) and Coiled-coil-helix-coiled-coil helix domain containing 2 (CHCHD2) as novel MICU1 interactors, independent of the mtCU. We demonstrate that MICU1 is essential for proper proteomic organization of the MICOS complex and that MICU1 ablation results in altered cristae organization and mitochondrial ultrastructure. We hypothesize that MICU1 serves as a MICOS calcium sensor, since perturbing MICU1 is sufficient to modulate cytochrome c release independent of mitochondrial Ca2+ uptake across the inner mitochondrial membrane (IMM). Here, we provide the first experimental evidence suggesting that MICU1 regulates cellular functions independent of mitochondrial calcium uptake and may serve as a critical mediator of Ca2+-dependent signaling to modulate mitochondrial membrane dynamics and cristae organization.

Abstract 15070: Micu1 Regulates Mitochondrial Cristae Structure and Function Independent of the Mitochondrial Calcium Uniporter Channel

Circulation ◽  
2020 ◽  
Vol 142 (Suppl_3) ◽  
Author(s):  
Dhanendra Tomar ◽  
Manfred Thomas ◽  
Joanne Garbincius ◽  
Devin Kolmetzky ◽  
Oniel Salik ◽  
...  
Keyword(s):  
Mitochondrial Membrane ◽  
Coiled Coil ◽  
Structure And Function ◽  
Membrane Dynamics ◽  
Size Exclusion ◽  
Null Mouse ◽  
Intermembrane Space ◽  
Inner Mitochondrial Membrane ◽  
Cytochrome C Release ◽  
And Function

Background: MICU1 is an EF-hand domain containing Ca 2+ -sensor regulating the mitochondrial Ca 2+ uniporter channel and mitochondrial Ca 2+ uptake. MICU1-null mouse and fly models display perinatal lethality with disorganized mitochondrial architecture. Interestingly, these phenotypes are distinct from other mtCU loss-of-function models ( MCU, MICU2, EMRE, MCUR1 ) and thus are likely not explained solely by changes in matrix Ca 2+ content. Using size-exclusion proteomics and co-immunofluorescence, we found that MICU1 localizes to mitochondrial complexes lacking MCU. These observations suggest that MICU1 may have additional cellular functions independent of the MCU. Methods: Biotin-based proximity labeling and proteomics, protein biochemistry, live-cell Ca 2+ imaging, electron microscopy, confocal and super-resolution imaging were utilized to identify and validate MICU1 novel functions. Results: The expression of a MICU1-BioID2 fusion protein in MCU +/+ and MCU -/- cells allowed the identification of the total vs. MCU-independent MICU1 interactome. LC-MS analysis of purified biotinylated proteins identified the mitochondrial contact site and cristae organizing system (MICOS) components Mitofilin (MIC60) and Coiled-coil-helix-coiled-coil helix domain containing 2 (CHCHD2) as MCU independent novel MICU1 interactors. We demonstrate that MICU1 is essential for proper organization of the MICOS complex and that MICU1 ablation results in altered cristae organization, mitochondrial ultrastructure, mitochondrial membrane dynamics, membrane potential, and cell death signaling. We hypothesize that MICU1 is a MICOS Ca 2+ - sensor since perturbing MICU1 is sufficient to modulate cytochrome c release independent of Ca 2+ uptake across the inner mitochondrial membrane. Conclusions: Here, we provide the first experimental evidence of an intermembrane space Ca 2+ - sensor regulating mitochondrial membrane dynamics, independent of changes in matrix Ca 2+ content. This study provides a novel paradigm to understand Ca 2+ -dependent regulation of mitochondrial structure and function and may help explain the mitochondrial remodeling reported to occur in numerous disease states.

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.

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 The mycotoxin phomoxanthone A disturbs the form and function of the inner mitochondrial membrane

2018 ◽  
Vol 9 (3) ◽  
Author(s):  
Philip Böhler ◽  
Fabian Stuhldreier ◽  
Ruchika Anand ◽  
Arun Kumar Kondadi ◽  
David Schlütermann ◽  
...  
Keyword(s):  
Mitochondrial Membrane ◽  
Inner Mitochondrial Membrane ◽  
Form And Function ◽  
And Function

scholarly journals A Calcium Guard in the Outer Membrane: Is VDAC a Regulated Gatekeeper of Mitochondrial Calcium Uptake?

2021 ◽  
Vol 22 (2) ◽  
pp. 946
Author(s):  
Paulina Sander ◽  
Thomas Gudermann ◽  
Johann Schredelseker
Keyword(s):  
Mitochondrial Membrane ◽  
Calcium Release ◽  
Physiological Role ◽  
Mitochondrial Calcium ◽  
Inner Mitochondrial Membrane ◽  
New Era ◽  
Voltage Dependent ◽  
Common Opinion ◽  
Long Time ◽  
The Individual

Already in the early 1960s, researchers noted the potential of mitochondria to take up large amounts of Ca2+. However, the physiological role and the molecular identity of the mitochondrial Ca2+ uptake mechanisms remained elusive for a long time. The identification of the individual components of the mitochondrial calcium uniporter complex (MCUC) in the inner mitochondrial membrane in 2011 started a new era of research on mitochondrial Ca2+ uptake. Today, many studies investigate mitochondrial Ca2+ uptake with a strong focus on function, regulation, and localization of the MCUC. However, on its way into mitochondria Ca2+ has to pass two membranes, and the first barrier before even reaching the MCUC is the outer mitochondrial membrane (OMM). The common opinion is that the OMM is freely permeable to Ca2+. This idea is supported by the presence of a high density of voltage-dependent anion channels (VDACs) in the OMM, forming large Ca2+ permeable pores. However, several reports challenge this idea and describe VDAC as a regulated Ca2+ channel. In line with this idea is the notion that its Ca2+ selectivity depends on the open state of the channel, and its gating behavior can be modified by interaction with partner proteins, metabolites, or small synthetic molecules. Furthermore, mitochondrial Ca2+ uptake is controlled by the localization of VDAC through scaffolding proteins, which anchor VDAC to ER/SR calcium release channels. This review will discuss the possibility that VDAC serves as a physiological regulator of mitochondrial Ca2+ uptake in the OMM.

scholarly journals Small mitochondrial protein NERCLIN regulates cardiolipin homeostasis and mitochondrial ultrastructure

2021 ◽  
Author(s):  
Svetlana Konovalova ◽  
Rubén Torregrosa-Muñumer ◽  
Pooja Manjunath ◽  
Sundar Baral ◽  
Xiaonan Liu ◽  
...  
Keyword(s):  
Lipid Analysis ◽  
Mitochondrial Dynamics ◽  
Mitochondrial Protein ◽  
Membrane Lipid ◽  
Negative Regulator ◽  
Mitochondrial Ultrastructure ◽  
Inner Mitochondrial Membrane ◽  
The Matrix ◽  
And Function ◽  
Regulatory Functions

ABSTRACTCardiolipin (CL) is an essential phospholipid for mitochondrial structure and function. Here we present a small mitochondrial protein, NERCLIN, as a negative regulator of CL homeostasis and mitochondrial ultrastructure. Primate-specific NERCLIN is expressed ubiquitously from GRPEL2 locus on a tightly regulated low level, but induced by heat stress. NERCLIN overexpression severely disrupts mitochondrial cristae structure and induces mitochondrial fragmentation. Proximity labeling suggested interactions of NERCLIN with CL synthesis and prohibitin complexes on the matrix side of the inner mitochondrial membrane. Lipid analysis indicated that NERCLIN regulates mitochondrial CL content. The regulation may occur directly through interaction with PTPMT1, a proximal partner on the CL synthesis pathway, as its product phosphatidylglycerol was also reduced by NERCLIN. We propose that NERCLIN contributes to stress-induced adaptation of mitochondrial dynamics and turnover by regulating the mitochondrial CL content. Our findings add NERCLIN to the group of recently identified small mitochondrial proteins with important regulatory functions.

scholarly journals Preservation of Mitochondrial Structure and Function after Bid- or Bax-Mediated Cytochrome c Release

2000 ◽  
Vol 150 (5) ◽  
pp. 1027-1036 ◽  
Author(s):  
Oliver von Ahsen ◽  
Christian Renken ◽  
Guy Perkins ◽  
Ruth M. Kluck ◽  
Ella Bossy-Wetzel ◽  
...  
Keyword(s):  
Cytochrome C ◽  
Protein Import ◽  
Mitochondrial Protein ◽  
Intermembrane Space ◽  
Caspase Activation ◽  
Cytochrome C Release ◽  
Mitochondrial Protein Import ◽  
Inner Membrane ◽  
And Function

Proapoptotic members of the Bcl-2 protein family, including Bid and Bax, can activate apoptosis by directly interacting with mitochondria to cause cytochrome c translocation from the intermembrane space into the cytoplasm, thereby triggering Apaf-1–mediated caspase activation. Under some circumstances, when caspase activation is blocked, cells can recover from cytochrome c translocation; this suggests that apoptotic mitochondria may not always suffer catastrophic damage arising from the process of cytochrome c release. We now show that recombinant Bid and Bax cause complete cytochrome c loss from isolated mitochondria in vitro, but preserve the ultrastructure and protein import function of mitochondria, which depend on inner membrane polarization. We also demonstrate that, if caspases are inhibited, mitochondrial protein import function is retained in UV-irradiated or staurosporine-treated cells, despite the complete translocation of cytochrome c. Thus, Bid and Bax act only on the outer membrane, and lesions in the inner membrane occurring during apoptosis are shown to be secondary caspase-dependent events.

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