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| Protein Name | VDAC2 |
| Gene | [VDAC2](/genes/vdac2) |
| UniProt | P45880 |
| PDB | 7SPP |
| Mass | 31.6 kDa (294 amino acids) |
| Family | Porin/VDAC family (eukaryotic) |
| Diseases | [Alzheimer's Disease](/diseases/alzheimers), [Parkinson's Disease](/diseases/parkinsons-disease), [ALS](/diseases/als) |
| Localization | Mitochondrial outer membrane |
VDAC2 (Voltage-Dependent Anion Channel 2) is a beta-barrel pore protein in the mitochondrial outer membrane (MOM) that serves as the principal gateway for metabolite exchange between the cytoplasm and mitochondria. VDAC2 conducts ATP, ADP, NADH, pyruvate, and other metabolites essential for oxidative phosphorylation. Uniquely among VDAC isoforms, VDAC2 has a critical anti-apoptotic function — it directly sequesters the pro-apoptotic effector BAK, preventing premature mitochondrial outer membrane permeabilization (MOMP) and cell death.
In neurodegeneration, VDAC2 dysfunction leads to bioenergetic failure, calcium dysregulation, and aberrant apoptosis activation — all central features of neuronal death in Alzheimer's, Parkinson's, and ALS.
VDAC2 forms a 19-stranded antiparallel beta-barrel in the MOM:
- Beta-barrel (19 strands): Forms the transmembrane pore with an internal diameter of ~2.5-3.0 nm (open state)
- N-terminal alpha-helix (residues 1-25): Located inside the barrel, acts as a voltage sensor and pore constriction element
- Unique N-terminal extension: VDAC2 has an 11-residue extension (compared to VDAC1) containing additional cysteine residues that mediate BAK interaction
- Cysteine residues: VDAC2 has 9 cysteines (vs. 2 in VDAC1), several exposed on the cytoplasmic face for BAK binding and redox regulation
- Open state (low voltage, ±10 mV): Large anion-selective pore (~4 nS conductance) allowing ATP, ADP, Pi, and other metabolites
- Closed/subconducting states (high voltage, >30 mV): Reduced pore (~2 nS), cation-selective, restricts metabolite flux but permits small cations including Ca2+
- The N-terminal helix swings out of the barrel upon voltage gating, altering selectivity
The unique anti-apoptotic function depends on VDAC2's cysteine-rich cytoplasmic face:
- Cysteines C47, C76, C103, C210, C227 form disulfide bridges with BAK cysteine residues
- This interaction keeps BAK in a monomeric, inactive conformation embedded in the MOM
- Disruption of VDAC2-BAK interaction (by BH3-only proteins like BID, BIM) releases BAK for oligomerization
VDAC2 is a critical node in cellular energy metabolism:
- ATP/ADP exchange: Exports matrix ATP to the cytoplasm; imports cytoplasmic ADP for oxidative phosphorylation
- NADH transport: Carries reducing equivalents across the MOM
- Metabolite channeling: Forms supercomplexes with hexokinase-II (at the MOM surface) and ANT (in the inner membrane) for efficient energy transfer
- Calcium transport: Mediates mitochondrial Ca2+ uptake at MAMs (mitochondria-associated ER membranes) via the VDAC2-GRP75-IP3R complex
VDAC2 is unique among VDAC isoforms in its anti-apoptotic role:
- Under healthy conditions, VDAC2 sequesters BAK in the MOM in an inactive monomer
- Apoptotic stimuli activate BH3-only proteins (BID, BIM, PUMA)
- BH3-only proteins displace BAK from VDAC2
- Free BAK oligomerizes with BAX to form MOMP pores
- Cytochrome c release through MOMP pores activates apoptosome → caspase-9 → caspase-3
- VDAC2 knockout mice are embryonic lethal; conditional knockouts show enhanced apoptotic sensitivity
VDAC2 participates in PINK1/Parkin-mediated mitophagy:
- PINK1 accumulates on the MOM of depolarized mitochondria
- PINK1 phosphorylates VDAC1 (and likely VDAC2) at specific sites
- Phosphorylated VDACs are ubiquitinated by Parkin (K27-linked and K48-linked chains)
- Ubiquitinated VDACs recruit p62/SQSTM1 and optineurin for autophagic clearance
- This pathway selectively eliminates damaged mitochondria to maintain organelle quality
VDAC2 is implicated in mitochondrial dysfunction in AD:
- Amyloid-beta peptides directly interact with VDAC channels, partially blocking the pore and reducing metabolite conductance
- Phosphorylated tau binds the cytoplasmic face of VDACs, further impairing mitochondrial bioenergetics
- Disruption of the VDAC2-GRP75-IP3R complex at MAMs leads to calcium dysregulation, an early AD feature
- Increased VDAC2 expression in vulnerable AD neurons may represent a compensatory response to bioenergetic stress
- VDAC closure by amyloid-beta triggers the mitochondrial permeability transition, releasing pro-apoptotic factors
In PD, VDAC2 intersects with multiple pathogenic pathways:
- PINK1/Parkin-dependent VDAC ubiquitination is required for mitophagy of damaged mitochondria
- Loss of PINK1/Parkin function (familial PD) impairs VDAC-dependent mitophagy signaling
- Alpha-synuclein oligomers interact with VDAC channels, disrupting metabolite transport
- Dopaminergic neurons are uniquely vulnerable because of high mitochondrial oxidative burden from dopamine metabolism
- Complex I inhibitors (MPTP, rotenone) impair VDAC2's protective BAK sequestration
- Misfolded mutant SOD1 directly binds VDAC1 on the MOM, inhibiting conductance
- TDP-43 mitochondrial localization affects VDAC-dependent import pathways
- Motor neurons have extraordinary bioenergetic demands due to long axons, making VDAC dysfunction especially deleterious
- VDAC-mediated calcium influx at motor neuron synaptic terminals may contribute to excitotoxic vulnerability
Key protein-protein interactions:
- BAK — Anti-apoptotic sequestration via cysteine bridges
- BAX — Indirect interaction (BAK oligomerization partner after VDAC2 release)
- Hexokinase-II — Metabolite channeling, VDAC closure prevents HK-II detachment
- GRP75/Mortalin — MAM tethering complex (VDAC2-GRP75-IP3R)
- ANT (adenine nucleotide translocator) — MOM-MIM supercomplex for ATP/ADP exchange
- PINK1 — Phosphorylation for mitophagy signaling
- Parkin — Ubiquitination for mitophagy
- Cyclophilin D (PPIF) — mPTP modulation