A paradigm shift: AMPK negatively regulates ULK1 activity.

In glucose-starved cells, macroautophagy (hereafter referred to as autophagy) is considered to serve as an energy-generating process contributing to cell survival. AMPK (adenosine monophosphate-activated protein kinase) is the primary cellular energy sensor that is activated during glucose starvation. According to the current paradigm in the field, AMPK promotes autophagy in response to energy deprivation by binding and phosphorylating ULK1 (UNC-51 like kinase 1), the protein kinase responsible for autophagy initiation. However, conflicting findings have been reported casting doubts about the current established model. In our recent study, we have thoroughly reevaluated the role of AMPK in autophagy. Contrary to the current paradigm, our study revealed that AMPK functions as a negative regulator of ULK1 activity. The study has elucidated the underlying mechanism and demonstrated the significance of the negative role in controlling autophagy and maintaining cellular resilience during energy depletion. AMPK: adenosine monophosphate-activated protein kinase; ULK1: UNC-51 like kinase 1; MTORC1: mechanistic target of rapamycin complex 1; ATG14: autophagy-related protein 14; PIK3C3: phosphatidylinositol 3-kinase catalytic subunit type 3; ATP: adenosine triphosphate; VPS34: vacuolar protein sorting 34; BECN1: Beclin 1; AMPKα: AMPK catalytic subunit α; LKB1: liver kinase B1; PIK3R4: phosphatidylinositol 3-kinase regulatory subunit 4.