scholarly journals A lower affinity to cytosolic proteins reveals VDAC3 isoform-specific role in mitochondrial biology

2020 ◽  
Vol 152 (2) ◽  
Author(s):  
María Queralt-Martín ◽  
Lucie Bergdoll ◽  
Oscar Teijido ◽  
Nabill Munshi ◽  
Daniel Jacobs ◽  
...  
Keyword(s):  
Sequence Similarity ◽  
Anion Channel ◽  
Mitochondrial Outer Membrane ◽  
Voltage Dependent Anion Channel ◽  
High Sequence Similarity ◽  
Major Pathway ◽  
Cytosolic Proteins ◽  
Functional Roles ◽  
Cysteine Scanning Mutagenesis ◽  
Specific Regulation

Voltage-dependent anion channel (VDAC) is the major pathway for the transport of ions and metabolites across the mitochondrial outer membrane. Among the three known mammalian VDAC isoforms, VDAC3 is the least characterized, but unique functional roles have been proposed in cellular and animal models. Yet, a high-sequence similarity between VDAC1 and VDAC3 is indicative of a similar pore-forming structure. Here, we conclusively show that VDAC3 forms stable, highly conductive voltage-gated channels that, much like VDAC1, are weakly anion selective and facilitate metabolite exchange, but exhibit unique properties when interacting with the cytosolic proteins α-synuclein and tubulin. These two proteins are known to be potent regulators of VDAC1 and induce similar characteristic blockages (on the millisecond time scale) of VDAC3, but with 10- to 100-fold reduced on-rates and altered α-synuclein blocking times, indicative of an isoform-specific function. Through cysteine scanning mutagenesis, we found that VDAC3’s cysteine residues regulate its interaction with α-synuclein, demonstrating VDAC3-unique functional properties and further highlighting a general molecular mechanism for VDAC isoform-specific regulation of mitochondrial bioenergetics.

scholarly journals The Open State Selectivity of the Bean Seed VDAC Depends on Stigmasterol and Ion Concentration

2021 ◽  
Vol 22 (6) ◽  
pp. 3034
Author(s):  
Hayet Saidani ◽  
Marc Léonetti ◽  
Hanna Kmita ◽  
Fabrice Homblé
Keyword(s):  
Physiological Role ◽  
Anion Channel ◽  
Physiological Effect ◽  
Ion Concentration ◽  
Mitochondrial Outer Membrane ◽  
Voltage Dependent Anion Channel ◽  
Major Pathway ◽  
Voltage Dependent ◽  
State Selectivity

The voltage-dependent anion channel (VDAC) is the major pathway for metabolites and ions transport through the mitochondrial outer membrane. It can regulate the flow of solutes by switching to a low conductance state correlated with a selectivity reversal, or by a selectivity inversion of its open state. The later one was observed in non-plant VDACs and is poorly characterized. We aim at investigating the selectivity inversion of the open state using plant VDAC purified from Phaseolus coccineus (PcVDAC) to evaluate its physiological role. Our main findings are: (1) The VDAC selectivity inversion of the open state occurs in PcVDAC, (2) Ion concentration and stigmasterol affect the occurrence of the open state selectivity inversion and stigmasterol appears to interact directly with PcVDAC. Interestingly, electrophysiological data concerning the selectivity inversion of the PcVDAC open state suggests that the phenomenon probably does not have a significant physiological effect in vivo.

scholarly journals Identification of two voltage-dependent anion channel-like protein sequences conserved in Kinetoplastida

2012 ◽  
Vol 8 (3) ◽  
pp. 446-449 ◽  
Author(s):  
Nadine Flinner ◽  
Enrico Schleiff ◽  
Oliver Mirus
Keyword(s):  
Outer Membrane ◽  
Trypanosoma Brucei ◽  
Protein Sequences ◽  
Anion Channel ◽  
Mitochondrial Outer Membrane ◽  
Voltage Dependent Anion Channel ◽  
Voltage Dependent

The eukaryotic porin superfamily consists of two families, voltage-dependent anion channel (VDAC) and Tom40, which are both located in the mitochondrial outer membrane. In Trypanosoma brucei , only a single member of the VDAC family has been described. We report the detection of two additional eukaryotic porin-like sequences in T. brucei . By bioinformatic means, we classify both as putative VDAC isoforms.

scholarly journals Motifs of VDAC2 required for mitochondrial Bak import and tBid-induced apoptosis

2015 ◽  
Vol 112 (41) ◽  
pp. E5590-E5599 ◽  
Author(s):  
Shamim Naghdi ◽  
Péter Várnai ◽  
György Hajnóczky
Keyword(s):  
Sequence Similarity ◽  
Anion Channel ◽  
Loss Of Function ◽  
Voltage Dependent Anion Channel ◽  
Fundamental Function ◽  
Cytoplasmic Surface ◽  
Voltage Dependent ◽  
Critical Residues ◽  
Induced Apoptosis ◽  
Relevant Domain

Voltage-dependent anion channel (VDAC) proteins are major components of the outer mitochondrial membrane. VDAC has three isoforms with >70% sequence similarity and redundant roles in metabolite and ion transport. However, only Vdac2−/− (V2−/−) mice are embryonic lethal, indicating a unique and fundamental function of VDAC2 (V2). Recently, a specific V2 requirement was demonstrated for mitochondrial Bak import and truncated Bid (tBid)-induced apoptosis. To determine the relevant domain(s) of V2 involved, VDAC1 (V1) and V2 chimeric constructs were created and used to rescue V2−/− fibroblasts. Surprisingly, the commonly cited V2-specific N-terminal extension and cysteines were found to be dispensable for Bak import and high tBid sensitivity. In gain-of-function studies, V2 (123–179) was the minimal sequence sufficient to render V1 competent to support Bak insertion. Furthermore, in loss-of-function experiments, T168 and D170 were identified as critical residues. These motifs are conserved in zebrafish V2 (zfV2) that also rescued V2-deficient fibroblasts. Because high-resolution structures of zfV2 and mammalian V1 have become available, we could superimpose these structures and recognized that the critical V2-specific residues help to create a distinctive open “pocket” on the cytoplasmic surface that could facilitate Bak recruitment.

scholarly journals Structure of the human voltage-dependent anion channel

2008 ◽  
Vol 105 (40) ◽  
pp. 15370-15375 ◽  
Author(s):  
Monika Bayrhuber ◽  
Thomas Meins ◽  
Michael Habeck ◽  
Stefan Becker ◽  
Karin Giller ◽  
...  
Keyword(s):  
Metabolic Flux ◽  
3D Structure ◽  
Anion Channel ◽  
Bioinformatic Analysis ◽  
Mitochondrial Outer Membrane ◽  
Voltage Dependent Anion Channel ◽  
X Ray Crystallography ◽  
Voltage Dependent ◽  
Α Helix ◽  
Induced Apoptosis

The voltage-dependent anion channel (VDAC), also known as mitochondrial porin, is the most abundant protein in the mitochondrial outer membrane (MOM). VDAC is the channel known to guide the metabolic flux across the MOM and plays a key role in mitochondrially induced apoptosis. Here, we present the 3D structure of human VDAC1, which was solved conjointly by NMR spectroscopy and x-ray crystallography. Human VDAC1 (hVDAC1) adopts a β-barrel architecture composed of 19 β-strands with an α-helix located horizontally midway within the pore. Bioinformatic analysis indicates that this channel architecture is common to all VDAC proteins and is adopted by the general import pore TOM40 of mammals, which is also located in the MOM.

Moving Ca2+ from the endoplasmic reticulum to mitochondria: is spatial intimacy enough?

2006 ◽  
Vol 34 (3) ◽  
pp. 351-355 ◽  
Author(s):  
G.A. Rutter
Keyword(s):  
Endoplasmic Reticulum ◽  
Outer Membrane Proteins ◽  
Anion Channel ◽  
Mitochondrial Outer Membrane ◽  
Interconnected Network ◽  
Voltage Dependent Anion Channel ◽  
Permeabilized Cells ◽  
Inositol 1,4,5 Trisphosphate ◽  
Voltage Dependent ◽  
Trisphosphate Receptor

A number of studies in recent years have demonstrated that the ER (endoplasmic reticulum) makes intimate contacts with mitochondria, the latter organelles existing both as individual organelles and occasionally as a more extensive interconnected network. Demonstrations that mitochondria take up Ca2+ more avidly upon its mobilization from the ER than when delivered to permeabilized cells as a buffered solution also indicate that a shielded conduit for Ca2+ may exist between the two organelle types, perhaps comprising the inositol 1,4,5-trisphosphate receptor and mitochondrial outer membrane proteins including the VDAC (voltage-dependent anion channel). Although the existence of such intracellular ER–mitochondria ‘synapses’, or of an ER–mitochondria Ca2+ ‘translocon’, is an exciting idea, more definitive experiments are needed to test this possibility.

scholarly journals VDAC oligomers form mitochondrial pores to release mtDNA fragments and promote lupus-like disease

Science ◽  
2019 ◽  
Vol 366 (6472) ◽  
pp. 1531-1536 ◽  
Author(s):  
Jeonghan Kim ◽  
Rajeev Gupta ◽  
Luz P. Blanco ◽  
Shutong Yang ◽  
Anna Shteinfer-Kuzmine ◽  
...  
Keyword(s):  
Outer Membrane ◽  
Lupus Erythematosus ◽  
Anion Channel ◽  
Live Cells ◽  
Mitochondrial Outer Membrane ◽  
Voltage Dependent Anion Channel ◽  
Mitochondrial Outer Membrane Permeabilization ◽  
Extracellular Traps ◽  
Voltage Dependent ◽  
Positively Charged

Mitochondrial stress releases mitochondrial DNA (mtDNA) into the cytosol, thereby triggering the type Ι interferon (IFN) response. Mitochondrial outer membrane permeabilization, which is required for mtDNA release, has been extensively studied in apoptotic cells, but little is known about its role in live cells. We found that oxidatively stressed mitochondria release short mtDNA fragments via pores formed by the voltage-dependent anion channel (VDAC) oligomers in the mitochondrial outer membrane. Furthermore, the positively charged residues in the N-terminal domain of VDAC1 interact with mtDNA, promoting VDAC1 oligomerization. The VDAC oligomerization inhibitor VBIT-4 decreases mtDNA release, IFN signaling, neutrophil extracellular traps, and disease severity in a mouse model of systemic lupus erythematosus. Thus, inhibiting VDAC oligomerization is a potential therapeutic approach for diseases associated with mtDNA release.

Functional roles of α 1 -, α 2 -, β 1 -, β 2 -tubulin in vegetative growth, microtubule assembly and sexual reproduction of Fusarium graminearum .

2021 ◽  
Author(s):  
Yuanye Zhu ◽  
Yuanshuai Zhang ◽  
Yabing Duan ◽  
Dongya Shi ◽  
Yi ping Hou ◽  
...  
Keyword(s):  
Sexual Reproduction ◽  
Fusarium Graminearum ◽  
Vegetative Growth ◽  
Microtubule Assembly ◽  
Mitochondrial Outer Membrane ◽  
Deletion Mutants ◽  
Voltage Dependent Anion Channel ◽  
Microtubule Cytoskeleton ◽  
Functional Roles ◽  
Β Tubulin

The plant pathogen Fusarium graminearum contains two α-tubulin (α 1 and α 2 ) isotypes and two β-tubulin isotypes (β 1 and β 2 ). The functional roles of these tubulins in microtubule assembly are not clear. Previous studies showed that α 1 - and β 2 -tubulin deletion mutants showed severe growth defects and hypersensitivity to carbendazim, which have not been well explained. Here, we investigated the interaction between α- and β-tubulin of F. graminearum . Co-localization experiments demonstrated that β 1 - and β 2 -tubulin are co-localized. Co-immunoprecipitation experiment suggested that β 1 -tubulin binds to both α 1 - and α 2 -tubulin and β 2 -tubulin can also bind to α 1 - or α 2 -tubulin. Interestingly, deletion of α 1 -tubulin increased the interaction between β 2 -tubulin and α 2 -tubulin. Microtubule observation assays showed that deletion of α 1 -tubulin completely disrupted β 1 -tubulin-containing microtubules and significantly decreased β 2 -tubulin-containing microtubules. Deletion of α 2 -, β 1 - or β 2 -tubulin respectively had no obvious effect on the microtubule cytoskeleton. However, microtubules in α 1 - and β 2 -tubulin deletion mutants were easily depolymerized in the presence of carbendazim. The sexual reproduction assay indicates that α 1 - and β 1 -tubulin deletion mutants could not produce asci and ascospores. These results implied that α 1 -tubulin may be essential for the microtubule cytoskeleton. However, our Δα 1 -2×α 2 mutant (α 1 -tubulin deletion mutant containing two copies of α 2 -tubulin) exhibited a normal microtubule network, growth and sexual reproduction. Interestingly, the Δα 1 -2×α 2 mutant was still hypersensitive to carbendazim. In addition, both β 1 -tubulin and β 2 -tubulin were found to bind the mitochondrial outer membrane voltage-dependent anion channel (VDAC), indicating they could regulate the function of VDAC. Importance: In this study, we found that F. graminearum contains four different α-/β-tubulin heterodimers (α 1 -β 1 , α 1 -β 2 , α 2 -β 1 and α 2 -β 2 ) and they assemble together into a single microtubule. Moreover, α 1 -, α 2 -tubulins are functionally interchangeable in microtubule assembly, vegetative growth and sexual reproduction. These results provide more insights into functional roles of different tubulins of F. graminearum which could be helpful for purification of tubulin heterodimers and developing new tubulin-binding agents.

Abstract 5420: Dephosphorylation of the Cardiac Mitochondrial Voltage-Dependent Anion Channel Prevents Inhibition by Hexokinase

Circulation ◽  
2008 ◽  
Vol 118 (suppl_18) ◽  
Author(s):  
Qunli Cheng ◽  
Zeljko J Bosnjak ◽  
Wai-Meng Kwok
Keyword(s):  
Mitochondrial Membrane ◽  
Mitochondrial Permeability Transition ◽  
Adenine Nucleotide ◽  
Standard Procedure ◽  
Anion Channel ◽  
Mitochondrial Outer Membrane ◽  
Cyclophilin D ◽  
Voltage Dependent Anion Channel ◽  
Voltage Dependent ◽  
The Mean

The mitochondrial permeability transition pore (mPTP) has been implicated as the end effector in ischemic and pharmacological preconditioning. Though the molecular composition of the mPTP is thought to consist of cyclophilin D located in the mitochondrial matrix, adenine nucleotide translocase on the inner mitochondrial membrane, and the voltage-dependent anion channel (VDAC) on the outer mitochondrial membrane, recent studies have raised the possibility that VDAC may be a regulatory, rather than a major, component of mPTP. Nevertheless, VDAC is likely to be a critical component of the preconditioning signaling pathway since it is the main conduit for metabolite diffusion across the mitochondrial outer membrane. Yet, the direct measurements of cardiac VDAC activity and modulation have been limited. In the present study, we purified VDAC from rat hearts using standard procedure and investigated its modulation by phosphatase and hexokinase. VDAC was incorporated into planar lipid bilayer for measurements of channel activities. The channel exhibited the reported voltage-dependent gating. Several conductance states were identified, with the most prevalent between 1.5 to 2 nS in 0.5 M NaCl. Koenig’s polyanion, a VDAC blocker, triggered channel flickering and decreased the mean current by 78±6%. In the presence of phosphatase (1 unit/ml), the mean conductance significantly increased from 1.81±0.03 to 3.68±0.61 nS (n=9; mean±SEM). However, the addition of a recombinant hexokinase (5 units/ml; GenWay Biotech) had no significant effect on the phosphatase-enhanced VDAC current (n=4). In contrast, recombinant hexokinase alone significantly decreased the mean conductance from 1.75±0.05 to 0.79±0.19 nS (n=4). The addition of phosphatase reversed the inhibitory effect of hexokinase and further enhanced VDAC activity, increasing the mean conductance to 2.69±0.19 nS (n=4). Our results suggest that the dephosphorylation of VDAC prevents the inhibitory effects of hexokinase. Furthermore, VDAC activity suppressed by hexokinase can be reversed by dephosphorylation of the channel. In conclusion, we have reported on a novel observation at the functional level that basal phosphorylation of the cardiac VDAC may be required for its modulation by hexokinase.

scholarly journals In self-defence: hexokinase promotes voltage-dependent anion channel closure and prevents mitochondria-mediated apoptotic cell death

2004 ◽  
Vol 377 (2) ◽  
pp. 347-355 ◽  
Author(s):  
Heftsi AZOULAY-ZOHAR ◽  
Adrian ISRAELSON ◽  
Salah ABU-HAMAD ◽  
Varda SHOSHAN-BARMATZ
Keyword(s):  
Cell Death ◽  
Cell Survival ◽  
Molecular Mechanisms ◽  
Apoptotic Cell ◽  
Direct Interaction ◽  
Anion Channel ◽  
Mitochondrial Outer Membrane ◽  
Voltage Dependent Anion Channel ◽  
Metabolic Intermediate ◽  
Voltage Dependent

In tumour cells, elevated levels of mitochondria-bound isoforms of hexokinase (HK-I and HK-II) result in the evasion of apoptosis, thereby allowing the cells to continue proliferating. The molecular mechanisms by which bound HK promotes cell survival are not yet fully understood. Our studies relying on the purified mitochondrial outer membrane protein VDAC (voltage-dependent anion channel), isolated mitochondria or cells in culture suggested that the anti-apoptotic activity of HK-I occurs via modulation of the mitochondrial phase of apoptosis. In the present paper, a direct interaction of HK-I with bilayer-reconstituted purified VDAC, inducing channel closure, is demonstrated for the first time. Moreover, HK-I prevented the Ca2+-dependent opening of the mitochondrial PTP (permeability transition pore) and release of the pro-apoptotic protein cytochrome c. The effects of HK-I on VDAC activity and PTP opening were prevented by the HK reaction product glucose 6-phosphate, a metabolic intermediate in most biosynthetic pathways. Furthermore, glucose 6-phosphate re-opened both the VDAC and the PTP closed by HK-I. The HK-I-mediated effects on VDAC and PTP were not observed using either yeast HK or HK-I lacking the N-terminal hydrophobic peptide responsible for binding to mitochondria, or in the presence of an antibody specific for the N-terminus of HK-I. Finally, HK-I overexpression in leukaemia-derived U-937 or vascular smooth muscle cells protected against staurosporine-induced apoptosis, with a decrease of up to 70% in cell death. These results offer insight into the mechanisms by which bound HK promotes tumour cell survival, and suggests that its overexpression not only ensures supplies of energy and phosphometabolites, but also reflects an anti-apoptotic defence mechanism.

scholarly journals Functions of BCL-XLat the Interface between Cell Death and Metabolism

2013 ◽  
Vol 2013 ◽  
pp. 1-10 ◽  
Author(s):  
Judith Michels ◽  
Oliver Kepp ◽  
Laura Senovilla ◽  
Delphine Lissa ◽  
Maria Castedo ◽  
...  
Keyword(s):  
Cell Death ◽  
Mitochondrial Permeability Transition ◽  
Atp Synthesis ◽  
Anion Channel ◽  
Permeability Transition ◽  
Short Review ◽  
Mitochondrial Outer Membrane ◽  
Voltage Dependent Anion Channel ◽  
Regulated Necrosis ◽  
Voltage Dependent

The BCL-2 homolog BCL-XL, one of the two protein products ofBCL2L1, has originally been characterized for its prominent prosurvival functions. Similar to BCL-2, BCL-XLbinds to its multidomain proapoptotic counterparts BAX and BAK, hence preventing the formation of lethal pores in the mitochondrial outer membrane, as well as to multiple BH3-only proteins, thus interrupting apical proapoptotic signals. In addition, BCL-XLhas been suggested to exert cytoprotective functions by sequestering a cytosolic pool of the pro-apoptotic transcription factor p53 and by binding to the voltage-dependent anion channel 1 (VDAC1), thereby inhibiting the so-called mitochondrial permeability transition (MPT). Thus, BCL-XLappears to play a prominent role in the regulation of multiple distinct types of cell death, including apoptosis and regulated necrosis. More recently, great attention has been given to the cell death-unrelated functions of BCL-2-like proteins. In particular, BCL-XLhas been shown to modulate a number of pathophysiological processes, including—but not limited to—mitochondrial ATP synthesis, protein acetylation, autophagy and mitosis. In this short review article, we will discuss the functions of BCL-XLat the interface between cell death and metabolism.

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