Energy stress-induced PKCζ S-glutathionylation is essential for LKB1 cytoplasmic translocation and AMPK activation

Energy stress triggers the activation of AMP-activated protein kinase (AMPK) via phosphorylation mediated by liver kinase B1 (LKB1). A pivotal step during this process is the translocation of protein kinase C zeta (PKCζ) to the nucleus, where it facilitates the phosphorylation and subsequent nuclear export of LKB1 to the cytosol. However, the mechanism(s) by which PKCζ translocates to the nucleus remains elusive. Here we demonstrate that energy stress, including glucose starvation or metformin treatment, elevates cellular Reactive Oxygen Species (ROS) that promotes PKCζ nuclear import to promote LKB1 cytoplasmic translocation and subsequent AMPK activation both in vitro and in vivo. Mechanistically, we show that energy stress-induced ROS promotes the S-glutathionylation of PKCζ at Cys48, and enhances the interaction of PKCζ with karyopherin subunit alpha 2 (KPNA2), a key nuclear transport protein, thereby facilitating PKCζ nuclear translocation and the phosphorylation of LKB1 at Ser428, consequently leading to LKB1 cytoplasmic translocation and activation of AMPK. Importantly, the reduction of ROS significantly augments the high-fat diet-induced lipid accumulation in mouse liver and reduces the hypoglycemic efficacy of metformin in an AMPK-dependent manner. Together, these results establish a critical role of energy stress-induced PKCζ S-glutathionylation in LKB1 cytoplasmic translocation, highlighting the activation of the ROS-PKCζ-KPNA2-LKB1 axis as a vital mechanism for AMPK activation in response to energy stress.

AMPK; LKB1; PKCζ; ROS; S-glutathionylation; energy stress.