Live cell interactome of the human voltage dependent anion channel 3 (VDAC3) revealed in HeLa cells by affinity purification tag technique

In higher eukaryotes three different VDAC genes encode three homologous proteins which do not show the same activity. VDAC1 and VDAC2 isoforms have been characterized while VDAC3 isoform is still elusive. To explore VDAC3 protein interactions, we have established a stable cell line expressing a fluorescent and dual-tagged construct. This clone expresses a stable amount of VDAC3. Live cell imaging shows that fluorescent VDAC3 localizes in the mitochondria. Proteins interacting with VDAC3 have been separated by tandem-affinity purification and 2-D gel electrophoresis and identified by mass spectrometry. In the list of putative interacting proteins, there are cytosolic, mitochondrial, cytoskeletal and ER proteins. Coherent pathways like cell redox homeostasis, response to stress, formation/rearrangement of disulfide bonds, response to unfolded proteins or protein folding have been found to be related to clusters of proteins identified in this experiment. The list of associated proteins has been validated by immunoprecipitation experiments utilizing specific antibodies. Likely biological and pathological processes have been analyzed. Cytosolic proteins associated with VDAC3 include tubulins and cytoskeletal proteins, stress sensors, chaperones and proteasome components, redox-mediating enzymes such as protein disulphide isomerase. The overall picture points to a role for VDAC3 as mediator for the organization of protein complexes and regulator of the traffic of misfolded or non-folded proteins evoked from different stimuli.