Redox Regulation of TRPML1 Channel Activity and Lysosome Trafficking in Podocytes

Recent studies have indicated that redox signaling is importantly involved in the control of exosome secretion from a variety of cells. However, the mechanism by which reactive oxygen species (ROS) regulates exosome release remains unknown. In the present study, we hypothesized that ROS attenuate TRPML1 channel-mediated Ca2+ release in podocytes through inhibition of acid ceramidase (AC) and thereby reduce lysosome trafficking, leading to prolongation of MVB fate to promote exosome secretion. Using GCaMP3 Ca2+ imaging technique, it was found that ML-SA1-induced Ca2+ release from lysosomes in podocytes was almost completely blocked by H2O2. However, sphingosine as an AC product of ceramide hydrolysis increased TRPML1 channel-mediated Ca2+ release from lysosome of podocytes, which was not prevented by pre-treatment with H2O2. Given the fact that Hcy induces NADPH oxidase-derived ROS production in podocytes, we tested whether Hcy-induced endogenous ROS production inhibits TRPML1 channel activity in these cel...