title: Lipin 2 binds phosphatidic acid by the electrostatic hydrogen bond switch mechanism independent of phosphorylation.
abstract: Lipin 2 is a phosphatidic acid phosphatase (PAP) responsible for the penultimate step of triglyceride synthesis and dephosphorylation of phosphatidic acid (PA) to generate diacylglycerol. The lipin family of PA phosphatases is composed of lipins 1-3, which are members of the conserved haloacid dehalogenase superfamily. Although genetic alteration of LPIN2 in humans is known to cause Majeed syndrome, little is known about the biochemical regulation of its PAP activity. Here, in an attempt to gain a better general understanding of the biochemical nature of lipin 2, we have performed kinetic and phosphorylation analyses. We provide evidence that lipin 2, like lipin 1, binds PA via the electrostatic hydrogen bond switch mechanism but has a lower rate of catalysis. Like lipin 1, lipin 2 is highly phosphorylated, and we identified 15 phosphosites. However, unlike lipin 1, the phosphorylation of lipin 2 is not induced by insulin signaling nor is it sensitive to inhibition of the mammalian target of rapamycin. Importantly, phosphorylation of lipin 2 does not negatively regulate either membrane binding or PAP activity. This suggests that lipin 2 functions as a constitutively active PA phosphatase in stark contrast to the high degree of phosphorylation-mediated regulation of lipin 1. This knowledge of lipin 2 regulation is important for a deeper understanding of how the lipin family functions with respect to lipid synthesis and, more generally, as an example of how the membrane environment around PA can influence its effector proteins.
authors.affiliation: From the Department of Pharmacology, University of Virginia, Charlottesville, Virginia 22908.
authors.forename: James M
authors.initials: JM
authors.lastname: Eaton
authors.affiliation: From the Department of Pharmacology, University of Virginia, Charlottesville, Virginia 22908.
authors.forename: Sankeerth
authors.initials: S
authors.lastname: Takkellapati
authors.affiliation: the Department of Genome Sciences, University of Washington, Seattle, Washington 98105.
authors.forename: Robert T
authors.initials: RT
authors.lastname: Lawrence
authors.affiliation: From the Department of Pharmacology, University of Virginia, Charlottesville, Virginia 22908.
authors.forename: Kelley E
authors.initials: KE
authors.lastname: McQueeney
authors.affiliation: From the Department of Pharmacology, University of Virginia, Charlottesville, Virginia 22908.
authors.forename: Salome
authors.initials: S
authors.lastname: Boroda
authors.affiliation: From the Department of Pharmacology, University of Virginia, Charlottesville, Virginia 22908.
authors.forename: Garrett R
authors.initials: GR
authors.lastname: Mullins
authors.affiliation: From the Department of Pharmacology, University of Virginia, Charlottesville, Virginia 22908.
authors.forename: Samantha G
authors.initials: SG
authors.lastname: Sherwood
authors.affiliation: the Department of Medicine, Washington University School of Medicine, St. Louis, Missouri 63110, and.
authors.forename: Brian N
authors.initials: BN
authors.lastname: Finck
authors.affiliation: the Department of Genome Sciences, University of Washington, Seattle, Washington 98105.
authors.forename: Judit
authors.initials: J
authors.lastname: Villén
authors.affiliation: From the Department of Pharmacology, University of Virginia, Charlottesville, Virginia 22908, teh3c@virginia.edu.
authors.forename: Thurl E
authors.initials: TE
authors.lastname: Harris
mesh_terms: D020816:Amino Acid Motifs; D000818:Animals; D006801:Humans; D006860:Hydrogen Bonding; D007328:Insulin / Q000378:metabolism; D007700:Kinetics; D051379:Mice; D010711:Phosphatidate Phosphatase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D010712:Phosphatidic Acids / Q000378:metabolism*; D010766:Phosphorylation; D011485:Protein Binding; D015398:Signal Transduction; D055672:Static Electricity
chemical_list: D007328:Insulin; D010712:Phosphatidic Acids; D010711:Phosphatidate Phosphatase; C540254:Lipin 2 protein, mouse
keywords: Diacylglycerol; Enzyme Kinetics; Lipin 2; Phosphatidic Acid; Phosphatidic Acid Phosphatase; Phosphatidylethanolamine; Phosphorylation; Polybasic Domain; lpin2; mTOR