title: Conserved residues in the N terminus of lipin-1 are required for binding to protein phosphatase-1c, nuclear translocation, and phosphatidate phosphatase activity.
abstract: Lipin-1 is a phosphatidate phosphatase in glycerolipid biosynthesis and signal transduction. It also serves as a transcriptional co-regulator to control lipid metabolism and adipogenesis. These functions are controlled partly by its subcellular distribution. Hyperphosphorylated lipin-1 remains sequestered in the cytosol, whereas hypophosphorylated lipin-1 translocates to the endoplasmic reticulum and nucleus. The serine/threonine protein phosphatase-1 catalytic subunit (PP-1c) is a major protein dephosphorylation enzyme. Its activity is controlled by interactions with different regulatory proteins, many of which contain conserved RVXF binding motifs. We found that lipin-1 binds to PP-1cγ through a similar HVRF binding motif. This interaction depends on Mg(2+) or Mn(2+) and is competitively inhibited by (R/H)VXF-containing peptides. Mutating the HVRF motif in the highly conserved N terminus of lipin-1 greatly decreases PP-1cγ interaction. Moreover, mutations of other residues in the N terminus of lipin-1 also modulate PP-1cγ binding. PP-1cγ binds poorly to a phosphomimetic mutant of lipin-1 and binds well to the non-phosphorylatable lipin-1 mutant. This indicates that lipin-1 is dephosphorylated before PP-1cγ binds to its HVRF motif. Importantly, mutating the HVRF motif also abrogates the nuclear translocation and phosphatidate phosphatase activity of lipin-1. In conclusion, we provide novel evidence of the importance of the lipin-1 N-terminal domain for its catalytic activity, nuclear localization, and binding to PP-1cγ.
authors.affiliation: Signal Transduction Research Group, Department of Biochemistry, University of Alberta, Edmonton, Alberta T6G 2S2, Canada.
authors.forename: Bernard P C
authors.initials: BPC
authors.lastname: Kok
authors.affiliation: Signal Transduction Research Group, Department of Biochemistry, University of Alberta, Edmonton, Alberta T6G 2S2, Canada.
authors.forename: Tamara D
authors.initials: TD
authors.lastname: Skene-Arnold
authors.affiliation: Signal Transduction Research Group, Department of Biochemistry, University of Alberta, Edmonton, Alberta T6G 2S2, Canada.
authors.forename: Ji
authors.initials: J
authors.lastname: Ling
authors.affiliation: Signal Transduction Research Group, Department of Biochemistry, University of Alberta, Edmonton, Alberta T6G 2S2, Canada.
authors.forename: Matthew G K
authors.initials: MGK
authors.lastname: Benesch
authors.affiliation: Signal Transduction Research Group, Department of Biochemistry, University of Alberta, Edmonton, Alberta T6G 2S2, Canada.
authors.forename: Jay
authors.initials: J
authors.lastname: Dewald
authors.affiliation: Department of Pharmacology, University of Virginia School of Medicine, Charlottesvillle, Virginia 22908.
authors.forename: Thurl E
authors.initials: TE
authors.lastname: Harris
authors.affiliation: Signal Transduction Research Group, Department of Biochemistry, University of Alberta, Edmonton, Alberta T6G 2S2, Canada.
authors.forename: Charles F B
authors.initials: CFB
authors.lastname: Holmes
authors.affiliation: Signal Transduction Research Group, Department of Biochemistry, University of Alberta, Edmonton, Alberta T6G 2S2, Canada. Electronic address: david.brindley@ualberta.ca.
authors.forename: David N
authors.initials: DN
authors.lastname: Brindley
mesh_terms: D021581:Active Transport, Cell Nucleus; D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D017124:Conserved Sequence; D005786:Gene Expression Regulation; D005822:Genetic Vectors; D057809:HEK293 Cells; D006801:Humans; D050356:Lipid Metabolism; D051379:Mice; D008969:Molecular Sequence Data; D010711:Phosphatidate Phosphatase / Q000378:metabolism*; D010766:Phosphorylation; D011485:Protein Binding; D054645:Protein Phosphatase 1 / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid
chemical_list: D054645:Protein Phosphatase 1; C485999:LPIN1 protein, human; D010711:Phosphatidate Phosphatase
keywords: Lipin; Nuclear Translocation; Phosphatidate; Protein Phosphatase; Protein Phosphorylation; Transcription Regulation; Yeast Metabolism