Proteomic approach to the identification of voltage-dependent anion channel protein isoforms in guinea pig brain synaptosomes

Voltage-dependent anion channel (VDAC) proteins are small, abundant, pore-forming proteins belonging to the eukaryotic mitochondrial porins. At least three different VDAC genes have been identified in vertebrates. VDAC proteins are known to play an essential role in cellular metabolism and in the early stages of apoptosis. A proteomic approach, consisting of two-dimensional gel electrophoresis followed by two-dimensional immunoblotting with anti-VDAC and anti-phosphotyrosine antibodies and by matrix-assisted laser desorption/ionization-time of flight mass spectrometry, was exploited to define the expression pattern of VDAC isoforms in guinea pig brain synaptosomes, both in normoxic and hypoxic conditions. In this way a total of five different VDAC isoforms were identified, as both VDAC1 and VDAC2 were detected in more than one electrophoretic spot. Moreover, VDAC isoforms selectively undergo hypoxia-induced tyrosine phosphorylation, suggesting that tyrosine phosphorylation may contribute to the modulation of VDAC protein function/conformation or interaction with other proteins in hypoxic conditions.