Inhibiting lysine 353 oxidation of GRP78 by a hypochlorous probe targeting endoplasmic reticulum promotes autophagy in cancer cells

The level of hypochlorous acid (HOCl) in cancer cells is higher than that in non-cancer cells. HOCl is an essential signal for the regulation of cell fate and works mainly through the protein post-translational modifications in cancer cells. However, the mechanism of HOCl regulating autophagy has not been clarified. Here we reported that a HOCl probe named ZBM-H targeted endoplasmic reticulum and induced an intact autophagy flux in lung cancer cells. Furthermore, ZBM-H promoted the binding of GRP78 to AMPK and increased the phosphorylation of AMPK in a dose- and time-dependent manner. GRP78 knockdown inhibited ZBM-H-induced AMPK phosphorylation and ZBM-H-stimulated autophagy. In addition, mass spectrometry combined with point mutation experiments revealed that ZBM-H increased GRP78 activity by inhibiting HOCl-induced lysine 353 oxidation of GRP78. Following ZBM-H treatment in vitro and in vivo, cell growth was significantly inhibited while apoptosis was induced. Nevertheless, exogenous HOCl partially reversed ZBM-H-inhibited cell growth and ZBM-H-induced GRP78 activation. In brief, we found that an endoplasmic reticulum-targeted HOCl probe named ZBM-H, acting through attenuating HOCl-induced GRP78 oxidation, inhibited tumor cell survival by promoting autophagy and apoptosis. Overall, these data demonstrated a novel mechanism of hypochlorous acid regulating autophagy by promoting the oxidation modification of GRP78.