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ADP regulates SNF1, the Saccharomyces cerevisiae homolog of AMP-activated protein kinase.

ABSTRACT: The SNF1 protein kinase complex plays an essential role in regulating gene expression in response to the level of extracellular glucose in budding yeast. SNF1 shares structural and functional similarities with mammalian AMP-activated protein kinase. Both kinases are activated by phosphorylation on a threonine residue within the activation loop segment of the catalytic subunit. Here we show that ADP is the long-sought metabolite that activates SNF1 in response to glucose limitation by protecting the enzyme against dephosphorylation by Glc7, its physiologically relevant protein phosphatase. We also show that the regulatory subunit of SNF1 has two ADP binding sites. The tighter site binds AMP, ADP, and ATP competitively with NADH, whereas the weaker site does not bind NADH, but is responsible for mediating the protective effect of ADP on dephosphorylation. Mutagenesis experiments suggest that the general mechanism by which ADP protects against dephosphorylation is strongly conserved between SNF1 and AMPK.

SUBMITTER: Mayer FV

PROVIDER: S-EPMC3241989 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Mammalian AMP-activated protein kinase has only a partial functional redundancy with Snf1 in Saccharomyces cerevisiae

Project description:Snf1/AMPK functions as a heterotrimeric complex, consisting of a regulatory subunit that is senses the energy status, a catalytic subunit with the canonical kinase domain and a scaffolding subunit to secure the complex together. The high degree of conservation in the sequence, structure and function of yeast Snf1 and mammalian AMPK, it is only logical to investigate the extent of conservation in the downstream effects that are controlled by these kinases.

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The AMP-activated protein kinase Snf1 regulates transcription factor binding, RNA polymerase II activity, and mRNA stability of glucose-repressed genes in Saccharomyces cerevisiae.

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Project description:The AMP-activated protein kinase (AMPK) is a major stress sensor of mammalian cells. AMPK's homolog in the yeast Saccharomyces cerevisiae, the SNF1 protein kinase, is a central regulator of carbon metabolism that inhibits the Snf3/Rgt2-Rgt1 glucose sensing pathway and activates genes involved in respiration. We present evidence that glucose induces modification of the Snf1 catalytic subunt of SNF1 with the small ubiquitin-like modifier protein SUMO, catalyzed by the SUMO (E3) ligase Mms21. Our results suggest that SUMOylation of Snf1 inhibits its function in two ways: by interaction of SUMO attached to lysine 549 with a SUMO-interacting sequence motif located near the active site of Snf1, and by targeting Snf1 for destruction via the Slx5-Slx8 (SUMO-directed) ubiquitin ligase. These findings reveal another way SNF1 function is regulated in response to carbon source.

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| S-EPMC4525183 | biostudies-literature

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