title: Glucose-induced posttranslational activation of protein phosphatases PP2A and PP1 in yeast.
abstract: The protein phosphatases PP2A and PP1 are major regulators of a variety of cellular processes in yeast and other eukaryotes. Here, we reveal that both enzymes are direct targets of glucose sensing. Addition of glucose to glucose-deprived yeast cells triggered rapid posttranslational activation of both PP2A and PP1. Glucose activation of PP2A is controlled by regulatory subunits Rts1, Cdc55, Rrd1 and Rrd2. It is associated with rapid carboxymethylation of the catalytic subunits, which is necessary but not sufficient for activation. Glucose activation of PP1 was fully dependent on regulatory subunits Reg1 and Shp1. Absence of Gac1, Glc8, Reg2 or Red1 partially reduced activation while Pig1 and Pig2 inhibited activation. Full activation of PP2A and PP1 was also dependent on subunits classically considered to belong to the other phosphatase. PP2A activation was dependent on PP1 subunits Reg1 and Shp1 while PP1 activation was dependent on PP2A subunit Rts1. Rts1 interacted with both Pph21 and Glc7 under different conditions and these interactions were Reg1 dependent. Reg1-Glc7 interaction is responsible for PP1 involvement in the main glucose repression pathway and we show that deletion of Shp1 also causes strong derepression of the invertase gene SUC2. Deletion of the PP2A subunits Pph21 and Pph22, Rrd1 and Rrd2, specifically enhanced the derepression level of SUC2, indicating that PP2A counteracts SUC2 derepression. Interestingly, the effect of the regulatory subunit Rts1 was consistent with its role as a subunit of both PP2A and PP1, affecting derepression and repression of SUC2, respectively. We also show that abolished phosphatase activation, except by reg1Δ, does not completely block Snf1 dephosphorylation after addition of glucose. Finally, we show that glucose activation of the cAMP-PKA (protein kinase A) pathway is required for glucose activation of both PP2A and PP1. Our results provide novel insight into the complex regulatory role of these two major protein phosphatases in glucose regulation.
authors.affiliation: Laboratory of Molecular Cell Biology, Institute of Botany and Microbiology, KULeuven, Belgium.
authors.forename: Dries
authors.initials: D
authors.lastname: Castermans
authors.forename: Ils
authors.initials: I
authors.lastname: Somers
authors.forename: Johan
authors.initials: J
authors.lastname: Kriel
authors.forename: Wendy
authors.initials: W
authors.lastname: Louwet
authors.forename: Stefaan
authors.initials: S
authors.lastname: Wera
authors.forename: Matthias
authors.initials: M
authors.lastname: Versele
authors.forename: Veerle
authors.initials: V
authors.lastname: Janssens
authors.forename: Johan M
authors.initials: JM
authors.lastname: Thevelein
mesh_terms: D020134:Catalytic Domain; D000242:Cyclic AMP / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D004789:Enzyme Activation; D005947:Glucose / Q000494:pharmacology*; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism; D010766:Phosphorylation; D054645:Protein Phosphatase 1 / Q000378:metabolism*; D054648:Protein Phosphatase 2 / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000187:drug effects / Q000201:enzymology*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D043324:beta-Fructofuranosidase / Q000235:genetics / Q000378:metabolism
chemical_list: D047908:Intracellular Signaling Peptides and Proteins; C106691:SHP1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D000242:Cyclic AMP; C071570:SNF1-related protein kinases; D017346:Protein Serine-Threonine Kinases; D017868:Cyclic AMP-Dependent Protein Kinases; C092048:GLC7 protein, S cerevisiae; C483105:PPH21 protein, S cerevisiae; D054645:Protein Phosphatase 1; D054648:Protein Phosphatase 2; C070829:REG1 protein, S cerevisiae; C468437:SUC2 protein, S cerevisiae; D043324:beta-Fructofuranosidase; D005947:Glucose