HGF/c-Met regulates p22 phox subunit of the NADPH oxidase complex in primary mouse hepatocytes by transcriptional and post-translational mechanisms

It is well-known that signaling mediated by the hepatocyte growth factor (HGF) and its receptor c-Met in the liver is involved in the control of cellular redox status and oxidative stress, particularly through its ability to induce hepatoprotective gene expression by activating survival pathways in hepatocytes. It has been reported that HGF can regulate the expression of some members of the NADPH oxidase family in liver cells, particularly the catalytic subunits and p22 . In the present work we were focused to characterize the mechanism of regulation of p22 by HGF and its receptor c-Met in primary mouse hepatocytes as a key determinant for cellular redox regulation. Primary mouse hepatocytes were treated with HGF (50 ng/mL) at different times. cyba expression (gene encoding p22 ) or protein content were addressed by real time RT-PCR, Western blot or immunofluorescence. Protein interactions were explored by immunoprecipitation and FRET analysis. Our results provided mechanistic information supporting the transcriptional repression of cyba induced by HGF in a mechanism dependent of NF-κB activity. We identified a post-translational regulation mechanism directed by p22 degradation by proteasome 26S, and a second mechanism mediated by p22 sequestration by c-Met in plasma membrane. Our data clearly show that HGF/c-Met exerts regulation of the NADPH oxidase by a wide-range of molecular mechanisms. NADPH oxidase-derived reactive oxygen species regulated by HGF/c-Met represents one of the main mechanisms of signal transduction elicited by this growth factor.