title: Yeast 3-phosphoinositide-dependent protein kinase-1 (PDK1) orthologs Pkh1-3 differentially regulate phosphorylation of protein kinase A (PKA) and the protein kinase B (PKB)/S6K ortholog Sch9.
abstract: Pkh1, -2, and -3 are the yeast orthologs of mammalian 3-phosphoinositide-dependent protein kinase-1 (PDK1). Although essential for viability, their functioning remains poorly understood. Sch9, the yeast protein kinase B and/or S6K ortholog, has been identified as one of their targets. We now have shown that in vitro interaction of Pkh1 and Sch9 depends on the hydrophobic PDK1-interacting fragment pocket in Pkh1 and requires the complementary hydrophobic motif in Sch9. We demonstrated that Pkh1 phosphorylates Sch9 both in vitro and in vivo on its PDK1 site and that this phosphorylation is essential for a wild type cell size. In vivo phosphorylation on this site disappeared during nitrogen deprivation and rapidly increased again upon nitrogen resupplementation. In addition, we have shown here for the first time that the PDK1 site in protein kinase A is phosphorylated by Pkh1 in vitro, that this phosphorylation is Pkh-dependent in vivo and occurs during or shortly after synthesis of the protein kinase A catalytic subunits. Mutagenesis of the PDK1 site in Tpk1 abolished binding of the regulatory subunit and cAMP dependence. As opposed to PDK1 site phosphorylation of Sch9, phosphorylation of the PDK1 site in Tpk1 was not regulated by nitrogen availability. These results bring new insight into the control and prevalence of PDK1 site phosphorylation in yeast by Pkh protein kinases.
authors.affiliation: Laboratory of Molecular Cell Biology, Institute of Botany and Microbiology, Katholieke Universiteit Leuven and Department of Molecular Microbiology, VIB, B-3001 Leuven-Heverlee, Flanders, Belgium.
authors.forename: Karin
authors.initials: K
authors.lastname: Voordeckers
authors.forename: Marlies
authors.initials: M
authors.lastname: Kimpe
authors.forename: Steven
authors.initials: S
authors.lastname: Haesendonckx
authors.forename: Wendy
authors.initials: W
authors.lastname: Louwet
authors.forename: Matthias
authors.initials: M
authors.lastname: Versele
authors.forename: Johan M
authors.initials: JM
authors.lastname: Thevelein
mesh_terms: D064413:3-Phosphoinositide-Dependent Protein Kinases; D000818:Animals; D020134:Catalytic Domain; D048429:Cell Size; D017868:Cyclic AMP-Dependent Protein Kinases / Q000737:chemistry; D057927:Hydrophobic and Hydrophilic Interactions; D016296:Mutagenesis; D009584:Nitrogen / Q000494:pharmacology; D010766:Phosphorylation; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000096:biosynthesis / Q000737:chemistry* / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt / Q000737:chemistry*; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017384:Sequence Deletion; D017386:Sequence Homology, Amino Acid
chemical_list: D029701:Saccharomyces cerevisiae Proteins; D064413:3-Phosphoinositide-Dependent Protein Kinases; C118385:PKH1 protein, S cerevisiae; C118386:PKH2 protein, S cerevisiae; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; C530964:SCH9 protein, S cerevisiae; D017868:Cyclic AMP-Dependent Protein Kinases; D009584:Nitrogen