title: Roles of acidic phospholipids and nucleotides in regulating membrane binding and activity of a calcium-independent phospholipase A2 isoform.
abstract: Phospholipase A(2) activity plays key roles in generating lipid second messengers and regulates membrane topology through the generation of asymmetric lysophospholipids. In particular, the Group VIA phospholipase A(2) (GVIA-iPLA(2)) subfamily of enzymes functions independently of calcium within the cytoplasm of cells and has been implicated in numerous cellular processes, including proliferation, apoptosis, and membrane transport steps. However, mechanisms underlying the spatial and temporal regulation of these enzymes have remained mostly unexplored. Here, we examine the subset of Caenorhabditis elegans lipases that harbor a consensus motif common to members of the GVIA-iPLA(2) subfamily. Based on sequence homology, we identify IPLA-1 as the closest C. elegans homolog of human GVIA-iPLA(2) enzymes and use a combination of liposome interaction studies to demonstrate a role for acidic phospholipids in regulating GVIA-iPLA(2) function. Our studies indicate that IPLA-1 binds directly to multiple acidic phospholipids, including phosphatidylserine, phosphatidylglycerol, cardiolipin, phosphatidic acid, and phosphorylated derivatives of phosphatidylinositol. Moreover, the presence of these acidic lipids dramatically elevates the specific activity of IPLA-1 in vitro. We also found that the addition of ATP and ADP promote oligomerization of IPLA-1, which probably underlies the stimulatory effect of nucleotides on its activity. We propose that membrane composition and the presence of nucleotides play key roles in recruiting and modulating GVIA-iPLA(2) activity in cells.
authors.affiliation: Department of Biomolecular Chemistry, University of Wisconsin-Madison Medical School, Madison, Wisconsin 53706, USA.
authors.forename: Kylee
authors.initials: K
authors.lastname: Morrison
authors.forename: Kristen
authors.initials: K
authors.lastname: Witte
authors.forename: Jonathan R
authors.initials: JR
authors.lastname: Mayers
authors.forename: Amber L
authors.initials: AL
authors.lastname: Schuh
authors.forename: Anjon
authors.initials: A
authors.lastname: Audhya
mesh_terms: D000818:Animals; D017173:Caenorhabditis elegans; D002151:Calorimetry / Q000379:methods; D002462:Cell Membrane / Q000378:metabolism; D019281:Dimerization; D004926:Escherichia coli / Q000378:metabolism; D005786:Gene Expression Regulation; D016678:Genome; D054522:Group VI Phospholipases A2 / Q000378:metabolism; D006801:Humans; D050356:Lipid Metabolism; D008081:Liposomes / Q000737:chemistry / Q000378:metabolism; D009154:Mutation; D009711:Nucleotides / Q000737:chemistry*; D010740:Phospholipases / Q000378:metabolism; D054512:Phospholipases A2, Calcium-Independent / Q000737:chemistry / Q000378:metabolism*; D010743:Phospholipids / Q000737:chemistry* / Q000378:metabolism; D011485:Protein Binding
chemical_list: D008081:Liposomes; D009711:Nucleotides; D010743:Phospholipids; D010740:Phospholipases; D054522:Group VI Phospholipases A2; D054512:Phospholipases A2, Calcium-Independent