title: Control of phospholipid synthesis by phosphorylation of the yeast lipin Pah1p/Smp2p Mg2+-dependent phosphatidate phosphatase.
abstract: Phosphorylation of the conserved lipin Pah1p/Smp2p in Saccharomyces cerevisiae was previously shown to control transcription of phospholipid biosynthetic genes and nuclear structure by regulating the amount of membrane present at the nuclear envelope (Santos-Rosa, H., Leung, J., Grimsey, N., Peak-Chew, S., and Siniossoglou, S. (2005) EMBO J. 24, 1931-1941). A recent report identified Pah1p as a Mg2+-dependent phosphatidate (PA) phosphatase that regulates de novo lipid synthesis (Han G.-S., Wu, W. I., and Carman, G. M. (2006) J. Biol. Chem. 281, 9210-9218). In this work we use a combination of mass spectrometry and systematic mutagenesis to identify seven Ser/Thr-Pro motifs within Pah1p that are phosphorylated in vivo. We show that phosphorylation on these sites is required for the efficient transcriptional derepression of key enzymes involved in phospholipid biosynthesis. The phosphorylation-deficient Pah1p exhibits higher PA phosphatase-specific activity than the wild-type Pah1p, indicating that phosphorylation of Pah1p controls PA production. Opi1p is a transcriptional repressor of phospholipid biosynthetic genes, responding to PA levels. Genetic analysis suggests that Pah1p regulates transcription of these genes through both Opi1p-dependent and -independent mechanisms. We also provide evidence that derepression of phospholipid biosynthetic genes is not sufficient to induce the nuclear membrane expansion shown in the pah1delta cells.
authors.affiliation: Cambridge Institute for Medical Research, University of Cambridge, Wellcome Trust/MRC Building, Hills Road, CB2 2XY Cambridge, United Kingdom.
authors.forename: Laura
authors.initials: L
authors.lastname: O'Hara
authors.forename: Gil-Soo
authors.initials: GS
authors.lastname: Han
authors.forename: Sew
authors.initials: S
authors.lastname: Peak-Chew
authors.forename: Neil
authors.initials: N
authors.lastname: Grimsey
authors.forename: George M
authors.initials: GM
authors.lastname: Carman
authors.forename: Symeon
authors.initials: S
authors.lastname: Siniossoglou
mesh_terms: D002462:Cell Membrane / Q000201:enzymology; D002846:Chromatography, Affinity; D002853:Chromatography, Liquid; D003600:Cytosol / Q000201:enzymology; D015966:Gene Expression Regulation, Fungal; D050155:Lipogenesis; D008274:Magnesium / Q000494:pharmacology; D016297:Mutagenesis, Site-Directed; D009685:Nuclear Envelope / Q000378:metabolism; D009930:Organic Chemicals / Q000378:metabolism; D010711:Phosphatidate Phosphatase / Q000235:genetics / Q000378:metabolism*; D010743:Phospholipids / Q000378:metabolism; D010766:Phosphorylation; D010957:Plasmids / Q000378:metabolism; D012331:RNA, Fungal / Q000235:genetics / Q000378:metabolism; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D014158:Transcription, Genetic
chemical_list: C096105:OPI1 protein, S cerevisiae; D009930:Organic Chemicals; D010743:Phospholipids; D012331:RNA, Fungal; D012097:Repressor Proteins; D029701:Saccharomyces cerevisiae Proteins; C088310:lipine; C079831:PAH1 protein, S cerevisiae; D010711:Phosphatidate Phosphatase; D008274:Magnesium