Regulation of cellular response to energy stress by RNF128 via modulation of AMPK activation

Abstract AMP-activated protein kinase (AMPK) is a highly conserved central regulator of metabolic processes, maintaining energy homeostasis under metabolic stress. Identifying new regulators of AMPK is critical to understanding its response to energy stress. This study reports the identification of RING finger protein 128 (RNF128), an AMPK-binding E3 ligase that physically and functionally interacts with AMPK. RNF128 facilitates the polyubiquitination and phosphorylation of AMPK, thereby modulating its activation in response to glucose deprivation. Overexpression of RNF128 enhanced cell death under energy stress conditions, whereas loss of RNF128 expression attenuated stress-induced cell death. RNF128 also regulated reactive oxygen species production and influenced the expression of glycolysis-related genes during glucose deprivation. In vivo, RNF128 deficiency reduced AMPK phosphorylation and alleviated fasting-induced liver injury, whereas adeno-associated virus serotype 8-mediated overexpression of RNF128 increased AMPK phosphorylation and exacerbated liver injury. In conclusion, this study demonstrates that RNF128 functions as an E3 ligase that promotes AMPK polyubiquitination and activation under energy stress, revealing a previously unrecognized role for RNF128.