title: Heterotrimer-independent regulation of activation-loop phosphorylation of Snf1 protein kinase involves two protein phosphatases.
abstract: The SNF1/AMP-activated protein kinases are αβγ-heterotrimers that sense and regulate energy status in eukaryotes. They are activated by phosphorylation of the catalytic Snf1/α subunit, and the Snf4/γ regulatory subunit regulates phosphorylation through adenine nucleotide binding. In Saccharomyces cerevisiae, the Snf1 subunit is phosphorylated on the activation-loop Thr-210 in response to glucose limitation. To assess the requirement of the heterotrimer for regulated Thr-210 phosphorylation, we examined Snf1 and a truncated Snf1 kinase domain (residues 1-309) that has partial Snf1 function. Snf1(1-309) does not interact with the β and Snf4/γ regulatory subunits, and its activity was independent of them in vivo. Phosphorylation of both Snf1 and Snf1(1-309) increased in response to glucose limitation in wild-type cells and in cells lacking β- and Snf4/γ-subunits. These results indicate that glucose regulation of activation-loop phosphorylation can occur by mechanism(s) that function independently of the regulatory subunits. We further show that the Reg1-Glc7 protein phosphatase 1 and Sit4 type 2A-like phosphatase are largely responsible for dephosphorylation of Thr-210 of Snf1(1-309). Together, these findings suggest that these two phosphatases mediate heterotrimer-independent regulation of Thr-210 phosphorylation.
authors.affiliation: Department of Genetics and Development, Columbia University, New York, NY 10032, USA.
authors.forename: Amparo
authors.initials: A
authors.lastname: Ruiz
authors.forename: Yang
authors.initials: Y
authors.lastname: Liu
authors.forename: Xinjing
authors.initials: X
authors.lastname: Xu
authors.forename: Marian
authors.initials: M
authors.lastname: Carlson
mesh_terms: D055372:AMP-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D005947:Glucose / Q000494:pharmacology; D015151:Immunoblotting; D008954:Models, Biological; D009154:Mutation; D010766:Phosphorylation / Q000187:drug effects; D055503:Protein Multimerization; D054645:Protein Phosphatase 1 / Q000235:genetics / Q000378:metabolism*; D054648:Protein Phosphatase 2 / Q000235:genetics / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D021122:Protein Subunits / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D013912:Threonine / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
chemical_list: D021122:Protein Subunits; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; D013912:Threonine; C071570:SNF1-related protein kinases; D017346:Protein Serine-Threonine Kinases; C078651:SNF4 protein, S cerevisiae; D055372:AMP-Activated Protein Kinases; C092048:GLC7 protein, S cerevisiae; D054645:Protein Phosphatase 1; D054648:Protein Phosphatase 2; C070829:REG1 protein, S cerevisiae; C104343:SIT4 protein, S cerevisiae; D005947:Glucose