The compartment-specific interactome of VDAC1 reveals its emerging role beyond mitochondria in breast cancer.

Voltage-dependent anion channel 1 (VDAC1) is a multifunctional protein that is primarily localized in the outer mitochondrial membrane, where it regulates metabolite flux and apoptosis. Aberrant expression of VDAC1 has been implicated in tumorigenesis. Moreover, recent reports suggested that VDAC1 is localized at the plasma membrane, but its role in this compartment remains unclear. This study aimed to evaluate the relationships between VDAC1 expression and clinicopathological parameters in breast cancer and to map its interaction networks in the mitochondrial and plasma membrane compartments. VDAC1 mRNA and protein levels were assessed in breast cancer tissues and adjacent nontumorous samples via quantitative real-time PCR and Western blotting, respectively. Subcellular localization was determined after isolation of the mitochondrial and plasma membrane fractions. Co-immunoprecipitation combined with liquid chromatography-tandem mass spectrometry (LC-MS/MS) was employed to identify VDAC1-interacting protein partners in both compartments. The identified proteins were analysed via bioinformatic tools to determine potential biological processes and complexes involving VDAC1. VDAC1 mRNA and protein expression were significantly elevated in breast tumor tissues compared with matched normal tissues. Our results confirmed that VDAC1 was localized not only in the mitochondria but also in the plasma membrane of both breast cancer tissues and cell lines. Proteomic profiling revealed distinct compartment-specific sets of VDAC1 interactors. In mitochondria, VDAC1 was involved mainly in energy metabolism, calcium transport, and apoptotic regulation, whereas in the plasma membrane, it was enriched in ion transport, cell adhesion, and G protein-coupled receptor signalling complexes. This study demonstrated that VDAC1 expression is elevated in breast cancer and is correlated with specific clinical features. The identification of VDAC1 at the plasma membrane and its distinct interaction networks in different subcellular compartments highlight its multifunctional role in cancer biology. These findings provide new insights into the metabolic and signalling pathways involving VDAC1 and motivate future studies of VDAC1 trafficking and regulation.