SNF1/AMPK controls its own localization by phosphorylating its activating kinase Sak1

SNF1/AMPK is a key metabolic regulator in yeast, orchestrating cellular responses to glucose depletion. Its activation relies on phosphorylation of the α subunit by the upstream kinases Sak1, Tos3, and Elm1, with Sak1 as the primary regulator. Interestingly, ten Snf1-dependent phosphosites on Sak1 have been reported. Here, we explored Snf1 nuclear/cytoplasmic dynamics upon glucose depletion by using single-cell live imaging. Snf1 nuclear entry peaks rapidly after glucose depletion in a Sak1-dependent manner, before gradually decreasing over time. In the sak1 ^10Ala mutant, which cannot be phosphorylated by Snf1, Snf1 exhibits a higher nuclear entry compared to WT, predominantly in S/G2/M cells. Remarkably, this finding correlates with increased phosphorylation of the nuclear Snf1 reporter ACC1-3xGFP-NLS and results in better adaptation to glucose scarcity. Our findings highlight that Snf1 is able to regulate its own subcellular localization, which is critical for fine tuning its activity and downstream signaling during metabolic stress.