Review
VDAC, a multi-functional mitochondrial protein regulating cell life and death

https://doi.org/10.1016/j.mam.2010.03.002Get rights and content

Abstract

Research over the past decade has extended the prevailing view of the mitochondrion to include functions well beyond the generation of cellular energy. It is now recognized that mitochondria play a crucial role in cell signaling events, inter-organellar communication, aging, cell proliferation, diseases and cell death. Thus, mitochondria play a central role in the regulation of apoptosis (programmed cell death) and serve as the venue for cellular decisions leading to cell life or death. One of the mitochondrial proteins controlling cell life and death is the voltage-dependent anion channel (VDAC), also known as mitochondrial porin. VDAC, located in the mitochondrial outer membrane, functions as gatekeeper for the entry and exit of mitochondrial metabolites, thereby controlling cross-talk between mitochondria and the rest of the cell. VDAC is also a key player in mitochondria-mediated apoptosis. Thus, in addition to regulating the metabolic and energetic functions of mitochondria, VDAC appears to be a convergence point for a variety of cell survival and cell death signals mediated by its association with various ligands and proteins. In this article, we review what is known about the VDAC channel in terms of its structure, relevance to ATP rationing, Ca2+ homeostasis, protection against oxidative stress, regulation of apoptosis, involvement in several diseases and its role in the action of different drugs. In light of our recent findings and the recently solved NMR- and crystallography-based 3D structures of VDAC1, the focus of this review will be on the central role of VDAC in cell life and death, addressing VDAC function in the regulation of mitochondria-mediated apoptosis with an emphasis on structure–function relations. Understanding structure–function relationships of VDAC is critical for deciphering how this channel can perform such a variety of functions, all important for cell life and death. This review also provides insight into the potential of VDAC1 as a rational target for new therapeutics.

Section snippets

Historical overview

In 2008, the structure of VDAC was determined almost simultaneously by three different groups, using different techniques (Bayrhuber et al., 2008, Hiller et al., 2008, Ujwal et al., 2008). The importance of this achievement can be best appreciated if one considers that only one other structure of an integral mitochondrial membrane protein responsible for metabolite transport, i.e. the adenine nucleotide translocase (ANT) carrier (Pebay-Peyroula et al., 2003), has been solved to date. The

VDAC purification: a common pattern

Soon after the discovery of a channel-forming component in mitochondria of Paramecium aurelia (Schein et al., 1976) and the finding that the outer mitochondrial membrane of a variety of cells contained the newly-defined voltage-dependent anion-selective channel (Colombini, 1979), researchers labored towards isolating the protein, with the aim of characterizing its functional and structural features.

The purification protocols developed to isolate VDAC from various tissues encountered an apparent

Methods employed for the study of VDAC channel activity

As for any membrane protein responsible for an exchange of solutes across a membrane, the functional properties of VDAC have been examined in reconstituted systems based on artificially prepared phospholipid bilayers. Two main membrane systems have been used to study the pore-forming activity of VDACs, i.e. vesicles or planar lipid bilayers (PLB). The former, historically used to detect the passage of labeled molecules, is less often employed, given the advantage of the smaller amount of active

The three-dimensional structure of hVDAC1

In 2008, the three-dimensional structure of isoform 1 of VDAC was determined at atomic resolution by three independent technical approaches (Bayrhuber et al., 2008, Hiller et al., 2008, Ujwal et al., 2008). The structure of human VDAC1 (hVDAC1) was solved in parallel by nuclear magnetic resonance spectroscopy (NMR) (Hiller et al., 2008) and by a novel approach combining nuclear magnetic resonance spectroscopy and X-ray crystallography (Bayrhuber et al., 2008). The three-dimensional structure of

VDAC genes

As detailed in Section 2.4, the evolution of VDAC sequences indicates that an ancestor gene lays at the origin of the various VDAC genes seen in most groups of organisms. Paralogs have appeared several times in the different lineages as a result of clearly different events. In Drosophilae, for example, segmental duplication has led to the highly divergent forms described in (Oliva et al., 2002). In S. cerevisiae, the two genes possibly are remnants of a genome duplication process (Kellis et

VDAC1 in the plasma membrane

The extra-mitochondrial localization of porin was shown for the first time by Thinnes and co-workers (Kayser et al., 1989, Thinnes et al., 1989; for reviews, see Bathori et al., 2000; De Pinto et al., 2010b), who fortuitously co-purified porin together with human transplantation antigens. Intrigued by this protein, they sequenced it by Edman degradation (Kayser et al., 1989) and called it porin 31HL. Later, they produced monoclonal antibodies against the N-terminal end of the protein (Babel et

VDAC silencing, overexpression and cell life and death

In recent years, RNA interference (RNAi) has been proven to be a powerful and specific approach for targeted RNA-dependent gene silencing and is rapidly become a central tool in the study of cell function in a wide range of biomedical applications (Gunsalus and Piano, 2005, Morita and Yoshida, 2002, Pushparaj et al., 2008). The mechanism of action of RNAi relies on the endogenous machinery responsible for post-transcriptional gene silencing regulation by micro-RNAs (miRNA) (Chekulaeva and

Mitochondria-mediated apoptosis

Cells can undergo death by several modes. One such route involves programmed cell death, or apoptosis. Apoptotic cell death occurs during many physiological conditions, such as during embryonic or immune system development, or in response to infection, DNA damage or disease (Danial and Korsmeyer, 2004, Elmore, 2007, Green, 2003, Hickman, 2002, Johnstone et al., 2002, Olson and Kornbluth, 2001, Tatton and Olanow, 1999). In apoptosis, a cascade of caspases, cysteine protease enzymes capable of

VDAC-associated proteins

VDAC1 localization in the OMM makes it not only a major gate for molecules that need to access and/or exit the IMS but also makes VDAC a functional anchor point for molecules that interact with the mitochondria. VDAC1, moreover, plays an important role in the coordination of communication between the mitochondria and the rest of the cell. A substantial aspect of this management involves the transient formation of complexes with other proteins (Vyssokikh et al., 2004). It has been suggested that

VDAC regulation by non-protein modulators

In addition to Ca2+ being proposed to modulate VDAC activity, various other reagents were shown to interact with VDAC and modify its channel activity by increasing the probability of VDAC closure. Moreover, it was demonstrated that VDAC closure by various reagents resulted in the inhibition of PTP opening, Cyto c release and apoptotic cell death. As most of these reagents have been previously discussed (for review, see Shoshan-Barmatz et al., 2006, Shoshan-Barmatz et al., 2008a, Shoshan-Barmatz

Mitochondria, ROS and oxidative stress

In aerobic organisms, oxygen is essential for efficient energy production but paradoxically, produces chronic toxic stress in cells. Diverse protective systems must, therefore, exist to enable adaptation to oxidative environments. Oxidative stress (OS) results when production of ROS exceeds the capacity of mitochondrial and cellular anti-oxidant defenses to remove these toxic species. Unbalanced oxidation/reduction of macromolecular cell components is involved in the pathogenesis of

VDAC phosphorylation, its function in apoptosis and modulation by associated proteins

Protein phosphorylation is a major post-translation modification regulatory system, modulating protein stability, enzymatic activity, sub-cellular localization, the ability to interact with binding partners, and more (Cohen, 2002). A cohort of protein kinases have been detected in mitochondria, e.g. protein kinase A (PKA) (Schwoch et al., 1990), different isoforms of protein kinase C (PKC) (Majumder et al., 2000), and components of the MAPK signaling pathway (Yuryev et al., 2000), glycogen

VDAC and human diseases

There is a substantial amount of evidence relating mitochondrial apoptosis to human disease (Mattson, 2000, Olson and Kornbluth, 2001). Mitochondria-mediated apoptosis plays a crucial role in the pathophysiology of several diseases, such as heart attack, stroke, cancer, mitochondrial enchephalomyopathies, and aging, as well as in neurodegenerative disorders, such as Parkinson’s disease, Alzheimer’s disease and amyotrophic lateral sclerosis (ALS, also known as Lou Gehrig’s disease) (Alexander et

VDAC and reagent toxicity

As presented above, mitochondria play a central role in the execution of apoptosis, with VDAC being a critical component in this pathway. As such, VDAC can be considered as a prime target for therapeutic agents designed to modulate apoptosis (Granville and Gottlieb, 2003). Indeed, several studies have demonstrated VDACs as the pharmacologic target of novel molecules inducing cancer cell death (Table 2). The cancer-selectivity of VDAC-dependent cytotoxic agents could be related to the higher

Concluding remarks

We have witnessed a significant accumulation of knowledge regarding the function of VDAC in recent years. Following the identification of VDAC as the OMM channel, much has been learned about the protein’s structure–function relationships, the biochemical and molecular basis of its activation and inactivation, and the manner by which VDAC activity is modulated within the cell. Biochemical and molecular approaches have revealed a remarkable diversity of regulatory mechanisms controlling VDAC

Acknowledgments

This research was supported by grants from the Israel Science Foundation, the Israel Cancer Association and the Chief Scientist’s Office, Ministry of Health, Government of Israel to VSB, and from the Max Planck Society to M.Z. who is also supported by a Heisenberg fellowship (ZW 71/2-1, 3-1). The support from Phil and Sima Needleman to VSB and of University of Catania (PRA 2006–2008), FIRB RBRN07BMCT, PRIN MIUR 2008SW44CS_004 to VDP are highly acknowledged.

We thank Abu-Hamad and Keshet

References (617)

  • A. Antignani et al.

    How do Bax and Bak lead to permeabilization of the outer mitochondrial membrane?

    Curr. Opin. Cell. Biol.

    (2006)
  • B. Antonsson et al.

    Bax is present as a high molecular weight oligomer/complex in the mitochondrial membrane of apoptotic cells

    J. Biol. Chem.

    (2001)
  • M. Arai et al.

    Mitochondrial phospholipid hydroperoxide glutathione peroxidase plays a major role in preventing oxidative injury to cells

    J. Biol. Chem.

    (1999)
  • K.K. Arora et al.

    Functional significance of mitochondrial bound hexokinase in tumor cell metabolism. Evidence for preferential phosphorylation of glucose by intramitochondrially generated ATP

    J. Biol. Chem.

    (1988)
  • L. Arzoine et al.

    Voltage-dependent anion channel 1-based peptides interact with hexokinase to prevent its anti-apoptotic activity

    J. Biol. Chem.

    (2009)
  • J.H. Bae et al.

    Ruthenium red, inhibitor of mitochondrial Ca2+ uniporter, inhibits curcumin-induced apoptosis via the prevention of intracellular Ca2+ depletion and cytochrome c release

    Biochem. Biophys. Res. Commun.

    (2003)
  • M.I. Bahamonde et al.

    Plasma membrane voltage-dependent anion channel mediates antiestrogen-activated maxi Cl- currents in C1300 neuroblastoma cells

    J. Biol. Chem.

    (2003)
  • M. Baijal et al.

    Residues putatively involved in binding of ATP and glucose 6-phosphate to a mammalian hexokinase: site-directed mutation at analogous positions in the N- and C-terminal halves of the type I isozyme

    Arch. Biochem. Biophys.

    (1995)
  • M.A. Baker et al.

    VDAC1 is a transplasma membrane NADH-ferricyanide reductase

    J. Biol. Chem.

    (2004)
  • J. Banerjee et al.

    Bax increases the pore size of rat brain mitochondrial voltage-dependent anion channel in the presence of tBid

    Biochem. Biophys. Res. Commun.

    (2004)
  • S.C. Barber et al.

    Oxidative stress in ALS: a mechanism of neurodegeneration and a therapeutic target

    Biochim. Biophys. Acta

    (2006)
  • G. Bathori et al.

    Porin is present in the plasma membrane where it is concentrated in caveolae and caveolae-related domains

    J. Biol. Chem.

    (1999)
  • G. Bathori et al.

    Ca2+-dependent control of the permeability properties of the mitochondrial outer membrane and voltage-dependent anion-selective channel (VDAC)

    J. Biol. Chem.

    (2006)
  • R. Benz

    Permeation of hydrophilic solutes through mitochondrial outer membranes: review on mitochondrial porins

    Biochim. Biophys. Acta

    (1994)
  • R. Benz et al.

    Electrical capacity of black lipid films and of lipid bilayers made from monolayers

    Biochim. Biophys. Acta

    (1975)
  • R. Benz et al.

    Ionic selectivity of pores formed by the matrix protein (porin) of Escherichia coli

    Biochim. Biophys. Acta

    (1979)
  • R. Benz et al.

    Inhibition of adenine nucleotide transport through the mitochondrial porin by a synthetic polyanion

    FEBS Lett.

    (1988)
  • R. Benz et al.

    The cationically selective state of the mitochondrial outer membrane pore: a study with intact mitochondria and reconstituted mitochondrial porin

    Biochim. Biophys. Acta

    (1990)
  • A.K. Bera et al.

    Mitochondrial VDAC can be phosphorylated by cyclic AMP-dependent protein kinase

    Biochem. Biophys. Res. Commun.

    (1995)
  • F. Bernier-Valentin et al.

    Interaction of tubulin with rat liver mitochondria

    J. Biol. Chem.

    (1982)
  • G. Beutner et al.

    Complexes between porin, hexokinase, mitochondrial creatine kinase and adenylate translocator display properties of the permeability transition pore. Implication for regulation of permeability transition by the kinases

    Biochim. Biophys. Acta

    (1998)
  • F. Bisaccia et al.

    Specific elution from hydroxylapatite of the mitochondrial phosphate carrier by cardiolipin

    Biochim. Biophys. Acta

    (1984)
  • E. Blachly-Dyson et al.

    Cloning and functional expression in yeast of two human isoforms of the outer mitochondrial membrane channel, the voltage-dependent anion channel

    J. Biol. Chem.

    (1993)
  • A.L. Blatz et al.

    Single voltage-dependent chloride-selective channels of large conductance in cultured rat muscle

    Biophys. J.

    (1983)
  • V. Borutaite et al.

    Nitric oxide donors, nitrosothiols and mitochondrial respiration inhibitors induce caspase activation by different mechanisms

    FEBS Lett.

    (2000)
  • P. Boya et al.

    Mitochondrion-targeted apoptosis regulators of viral origin

    Biochem. Biophys. Res. Commun.

    (2003)
  • P. Boya et al.

    Viral proteins targeting mitochondria: controlling cell death

    Biochim. Biophys. Acta

    (2004)
  • D. Brdiczka

    Contact sites between mitochondrial envelope membranes. Structure and function in energy- and protein-transfer

    Biochim. Biophys. Acta

    (1991)
  • P.S. Brookes et al.

    Concentration-dependent effects of nitric oxide on mitochondrial permeability transition and cytochrome c release

    J. Biol. Chem.

    (2000)
  • G.C. Brown

    Regulation of mitochondrial respiration by nitric oxide inhibition of cytochrome c oxidase

    Biochim. Biophys. Acta

    (2001)
  • G.C. Brown et al.

    Nitric oxide inhibition of mitochondrial respiration and its role in cell death

    Free Radic. Biol. Med.

    (2002)
  • J.M. Bryson et al.

    Increased hexokinase activity, of either ectopic or endogenous origin, protects renal epithelial cells against acute oxidant-induced cell death

    J. Biol. Chem.

    (2002)
  • C. Cande et al.

    Apoptosis-inducing factor (AIF): a novel caspase-independent death effector released from mitochondria

    Biochimie

    (2002)
  • L. Canevari et al.

    Effect of postischaemic hypothermia on the mitochondrial damage induced by ischaemia and reperfusion in the gerbil

    Brain Res.

    (1999)
  • J.H. Charuk et al.

    Interaction of ruthenium red with Ca2(+)-binding proteins

    Anal. Biochem.

    (1990)
  • M. Chekulaeva et al.

    Mechanisms of miRNA-mediated post-transcriptional regulation in animal cells

    Curr. Opin. Cell. Biol.

    (2009)
  • J.E. Chipuk et al.

    How do BCL-2 proteins induce mitochondrial outer membrane permeabilization?

    Trends Cell. Biol.

    (2008)
  • M. Abdelrahim et al.

    RNAi and cancer: implications and applications

    J. RNAi Gene Silencing

    (2006)
  • S. Abu-Hamad et al.

    The expression level of the voltage-dependent anion channel controls life and death of the cell

    Proc. Natl. Acad. Sci. USA

    (2006)
  • S. Abu-Hamad et al.

    The VDAC1 N-terminus is essential both for apoptosis and the protective effect of anti-apoptotic proteins

    J. Cell. Sci.

    (2009)
  • Cited by (575)

    View all citing articles on Scopus
    View full text