Pil1p and Lsp1p negatively regulate the 3-phosphoinositide-dependent protein kinase-like kinase Pkh1p and downstream signaling pathways Pkc1p and Ypk1p.
The Saccharomyces cerevisiae homologs, Pkh1/2p, of the mammalian 3-phosphoinositide-dependent protein kinase 1 (PDK1) regulate the Pkc1-MAP kinase cascade and the partially parallel Ypk1/2p pathway(s) that control growth and cell integrity. Mammalian PDK1 is regulated by 3-phosphoinositides, whereas Pkh1/2p are regulated by sphingolipid long-chain bases (LCBs). Recently Pkh1/2p were found to complex with two related proteins, Pil1p (Ygr086) and Lsp1p (Ypl004). Because these two proteins are not related to any known protein we sought to characterize their functions. We show that Pkh1p phosphorylates both proteins in vitro in a reaction that is only weakly regulated by LCBs. In contrast, LCBs inhibit phosphorylation of Pil1p by Pkh2p, whereas LCBs stimulate phosphorylation of Lsp1p by Pkh2p. We find that Pil1p and Lsp1p down-regulate resistance to heat stress and, specifically, that they down-regulate the activity of the Pkc1p-MAP and Ypk1p pathways during heat stress. Pil1p and Lsp1p are thus the first proteins identified as regulators of Pkh1/2p. An unexpected finding was that the level of Ypk1p is greatly reduced in pkc1Delta cells, indicating that Pkc1p controls the level of Ypk1p. Homologs of Pil1p and Lsp1p are widespread in nature, and our results suggest that they may be negative regulators of PDK-like protein kinases and their downstream cellular pathways that control cell growth and survival.
Zhang
Xiping
X
Department of Molecular and Cellular Biochemistry and the Lucille P Markey Cancer Center, University of Kentucky College of Medicine, Lexington, Kentucky 40536, USA.
Lester
Robert L
RL
Dickson
Robert C
RC
D064413:3-Phosphoinositide-Dependent Protein Kinases; D000469:Alkaline Phosphatase / Q000378:metabolism; D002455:Cell Division; D002470:Cell Survival; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation; D005656:Fungal Proteins / Q000378:metabolism*; D017353:Gene Deletion; D015966:Gene Expression Regulation, Fungal; D038362:Glycogen Synthase Kinase 3; D006358:Hot Temperature; D015151:Immunoblotting; D050356:Lipid Metabolism; D020928:Mitogen-Activated Protein Kinases; D008954:Models, Biological; D010750:Phosphoproteins / Q000502:physiology*; D010766:Phosphorylation; D010957:Plasmids / Q000378:metabolism; D011233:Precipitin Tests; D011493:Protein Kinase C / Q000378:metabolism*; D011494:Protein Kinases / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000201:enzymology*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism* / Q000502:physiology*; D015398:Signal Transduction; D013696:Temperature; D013997:Time Factors
D005656:Fungal Proteins; C487328:LSP1 protein, S cerevisiae; C487327:PIL1 protein, S cerevisiae; D010750:Phosphoproteins; D029701:Saccharomyces cerevisiae Proteins; D011494:Protein Kinases; C097993:Pkc1 protein, Trichoderma reesei; D011505:Protein-Tyrosine Kinases; D064413:3-Phosphoinositide-Dependent Protein Kinases; C118385:PKH1 protein, S cerevisiae; D017346:Protein Serine-Threonine Kinases; D011493:Protein Kinase C; D020928:Mitogen-Activated Protein Kinases; C072724:SLT2 protein, S cerevisiae; D038362:Glycogen Synthase Kinase 3; C068124:MCK1 protein, S cerevisiae; D000469:Alkaline Phosphatase