title: Characterization of the S. cerevisiae inp51 mutant links phosphatidylinositol 4,5-bisphosphate levels with lipid content, membrane fluidity and cold growth.
abstract: Phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2] and its derivatives diphosphoinositol phosphates (DPIPs) play key signaling and regulatory roles. However, a direct function of these molecules in lipid and membrane homeostasis remains obscure. Here, we have studied the cold tolerance phenotype of yeast cells lacking the Inp51-mediated phosphoinositide-5-phosphatase. Genetic and biochemical approaches showed that increased metabolism of PI(4,5)P2 reduces the activity of the Pho85 kinase by increasing the levels of the DPIP isomer 1-IP7. This effect was key in the cold tolerance phenotype. Indeed, pho85 mutant cells grew better than the wild-type at 15 °C, and lack of this kinase abolished the inp51-mediated cold phenotype. Remarkably, reduced Pho85 function by loss of Inp51 affected the activity of the Pho85-regulated target Pah1, the yeast phosphatidate phosphatase. Cells lacking Inp51 showed reduced Pah1 abundance, derepression of an INO1-lacZ reporter, decreased content of triacylglycerides and elevated levels of phosphatidate, hallmarks of the pah1 mutant. However, the inp51 phenotype was not associated to low Pah1 activity since deletion of PAH1 caused cold sensitivity. In addition, the inp51 mutant exhibited features not shared by pah1, including a 40%-reduction in total lipid content and decreased membrane fluidity. These changes may influence the activity of membrane-anchored and/or associated proteins since deletion of INP51 slows down the transit to the vacuole of the fluorescent dye FM4-64. In conclusion, our work supports a model in which changes in the PI(4,5)P2 pool affect the 1-IP7 levels modulating the activity of Pho85, Pah1 and likely additional Pho85-controlled targets, and regulate lipid composition and membrane properties.
authors.affiliation: Instituto de Agroquímica y Tecnología de los Alimentos, Consejo Superior de Investigaciones Científicas (CSIC), Paterna, Valencia, Spain.
authors.forename: Isaac
authors.initials: I
authors.lastname: Córcoles-Sáez
authors.affiliation: Instituto de la Grasa, Consejo Superior de Investigaciones Científicas (CSIC), Sevilla, Spain.
authors.forename: Maria Luisa
authors.initials: ML
authors.lastname: Hernández
authors.affiliation: Instituto de la Grasa, Consejo Superior de Investigaciones Científicas (CSIC), Sevilla, Spain.
authors.forename: Jose Manuel
authors.initials: JM
authors.lastname: Martínez-Rivas
authors.affiliation: Instituto de Agroquímica y Tecnología de los Alimentos, Consejo Superior de Investigaciones Científicas (CSIC), Paterna, Valencia, Spain.
authors.forename: Jose A
authors.initials: JA
authors.lastname: Prieto
authors.affiliation: Instituto de Agroquímica y Tecnología de los Alimentos, Consejo Superior de Investigaciones Científicas (CSIC), Paterna, Valencia, Spain. Electronic address: randez@iata.csic.es.
authors.forename: Francisca
authors.initials: F
authors.lastname: Randez-Gil
mesh_terms: D000222:Adaptation, Physiological; D001692:Biological Transport; D002462:Cell Membrane / Q000201:enzymology*; D003080:Cold Temperature; D018844:Cyclin-Dependent Kinases / Q000235:genetics / Q000378:metabolism; D005456:Fluorescent Dyes / Q000378:metabolism; D015966:Gene Expression Regulation, Fungal; D005838:Genotype; D008560:Membrane Fluidity; D008563:Membrane Lipids / Q000378:metabolism*; D009154:Mutation; D010641:Phenotype; D010711:Phosphatidate Phosphatase / Q000235:genetics / Q000378:metabolism; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000378:metabolism*; D010744:Phosphoric Monoester Hydrolases / Q000235:genetics / Q000378:metabolism*; D011726:Pyridinium Compounds / Q000378:metabolism; D000644:Quaternary Ammonium Compounds / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D015290:Second Messenger Systems; D013997:Time Factors; D014280:Triglycerides / Q000378:metabolism
chemical_list: C092350:FM 4-64; D005456:Fluorescent Dyes; D008563:Membrane Lipids; D019269:Phosphatidylinositol 4,5-Diphosphate; D011726:Pyridinium Compounds; D000644:Quaternary Ammonium Compounds; D029701:Saccharomyces cerevisiae Proteins; D014280:Triglycerides; D018844:Cyclin-Dependent Kinases; C058605:PHO85 protein, S cerevisiae; C110551:INP51 protein, S cerevisiae; D010744:Phosphoric Monoester Hydrolases; C079831:PAH1 protein, S cerevisiae; D010711:Phosphatidate Phosphatase
keywords: Diphosphoinositol phosphates; IP(7); Inositol phosphates; Pah1; Pho85; Yeast