Noncatalytic functions of IPMK are essential for activation of autophagy and liver regeneration

Abstract

Macroautophagy/autophagy plays important roles in health and disease, but mechanisms of its activation are unclear. Recently we established IPMK (inositol polyphosphate multikinase) as a physiological determinant of autophagy independent of its catalytic activity. Two signaling axes, IPMK-AMPK-SIRT1 and IPMK-AMPK-ULK1, appear to mediate the influence of IPMK on autophagy. IPMK enhances autophagy-related transcription by stimulating AMPK-dependent SIRT1 activation, which mediates the deacetylation of histone 4 lysine 16. Furthermore, direct binding of IPMK to ULK and AMPK forms a ternary complex that facilitates AMPK-dependent ULK phosphorylation. Deletion of Ipmk virtually abolishes lipophagy, promotes liver damage and impairs hepatocyte regeneration. Our study establishes the importance of IPMK in regulation of autophagy and as a drug target for autophagy-related diseases.