title: A phosphorylation-regulated amphipathic helix controls the membrane translocation and function of the yeast phosphatidate phosphatase.
abstract: Regulation of membrane lipid composition is crucial for many aspects of cell growth and development. Lipins, a novel family of phosphatidate (PA) phosphatases that generate diacylglycerol (DAG) from PA, are emerging as essential regulators of fat metabolism, adipogenesis, and organelle biogenesis. The mechanisms that govern lipin translocation onto membranes are largely unknown. Here we show that recruitment of the yeast lipin (Pah1p) is regulated by PA levels onto the nuclear/endoplasmic reticulum (ER) membrane. Recruitment requires the transmembrane protein phosphatase complex Nem1p-Spo7p. Once dephosphorylated, Pah1p can bind to the nuclear/ER membrane independently of Nem1p-Spo7p via a short amino-terminal amphipathic helix. Dephosphorylation enhances the activity of Pah1p, both in vitro and in vivo, but only in the presence of a functional helix. The helix is required for both phospholipid and triacylglycerol biosynthesis. Our data suggest that dephosphorylation of Pah1p by the Nem1p-Spo7p complex enables the amphipathic helix to anchor Pah1p onto the nuclear/ER membrane allowing the production of DAG for lipid biosynthesis.
authors.affiliation: Cambridge Institute for Medical Research, University of Cambridge Wellcome Trust/Medical Research Council Building, Hills Road, Cambridge CB2 0XY, United Kingdom.
authors.forename: Eleftherios
authors.initials: E
authors.lastname: Karanasios
authors.forename: Gil-Soo
authors.initials: GS
authors.lastname: Han
authors.forename: Zhi
authors.initials: Z
authors.lastname: Xu
authors.forename: George M
authors.initials: GM
authors.lastname: Carman
authors.forename: Symeon
authors.initials: S
authors.lastname: Siniossoglou
mesh_terms: D019295:Computational Biology; D004075:Diglycerides / Q000378:metabolism; D005453:Fluorescence; D007091:Image Processing, Computer-Assisted; D007425:Intracellular Membranes / Q000378:metabolism*; D007700:Kinetics; D008563:Membrane Lipids / Q000096:biosynthesis*; D008565:Membrane Proteins / Q000378:metabolism; D008823:Micelles; D009687:Nuclear Proteins / Q000378:metabolism; D010711:Phosphatidate Phosphatase / Q000378:metabolism*; D010712:Phosphatidic Acids / Q000378:metabolism*; D010766:Phosphorylation; D017433:Protein Structure, Secondary; D012441:Saccharomyces cerevisiae / Q000201:enzymology*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*
chemical_list: D004075:Diglycerides; D008563:Membrane Lipids; D008565:Membrane Proteins; D008823:Micelles; C502372:Nem1 protein, S cerevisiae; D009687:Nuclear Proteins; D010712:Phosphatidic Acids; C116365:SPO7 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; C079831:PAH1 protein, S cerevisiae; D010711:Phosphatidate Phosphatase