Yeast VDAC2 has Pore Forming Activity: Functional Consequences

Abstract

The pore-forming proteins Voltage Dependent Anion Channel (VDAC) on the mitochondrial outer membrane (MOM) mediate the metabolic exchanges between cytosol and mitochondria. The pore has been characterized in eukaryotes spanning from insects [1,2] to mammals [3]. In S. cerevisiae, the por1 gene encodes for the main porin yVDAC1, with electrophysiological features similar to the human homologous [4]. yVDAC1 regulates yeast viability in non-fermentable conditions since the genetic inactivation of por1 (Δpor1 strain) reduces dramatically the yeast growth on glycerol [4]. In yeast genome a por1 paralog, por2, was found, but the putative porin yVDAC2 was definitely less characterized than VDAC1, despite 50% of sequence identity. Many evidences have questioned the ability of yVDAC2 to act as a pore on the MOM. E.g., the por2 inactivation does not affect yeast growth on glycerol; furthermore, no pore-forming activity of yVDAC2 was noticed so far in electrophysiological systems. Nevertheless, if overexpressed, yVDAC2 can functionally complement the absence of yVDAC1 in Δpor1 [4]. This was recently confirmed by our work, showing that por2 overexpression, a consequence of human SOD1 expression, completely restores Δpor1 yeast growth on glycerol, as well as the mitochondrial functionality [5]. In this work, we have characterized the electrophysiology of recombinant yVDAC2 and its features in model cell. The influence of the cysteine oxidation was investigated following recent achievements in other eukaryotic VDAC isoforms [6-7].1. De Pinto V et al, Biochim Biophys Acta (1989) 987:1-72.Aiello et al, J Biol Chem (2004) 279:25364-733. Menzel VA et al, Biosc Rep (2009) 29:351-624. Blachly-Dyson E et al, Mol Cell Biol (1997) 17:5727-38.5. Magri A et al, Biochim Biophys Acta (2016) 1857:789-98.6. Reina S et al, Oncotarget (2016) 7:2249-687. De Pinto V et al, Biochim Biophys Acta (2016) 987:1-7