title: Differential roles for cytosolic and microsomal Ca2+-independent phospholipase A2 in cell growth and maintenance of phospholipids.
abstract: Physiological roles of microsomal (iPLA(2)gamma) and cytosolic (iPLA(2)beta)Ca(2+)-independent phospholipase A(2) were determined in two different epithelial cell models. R- and S-enantiomers of the iPLA(2) inhibitor bromoenol lactone (BEL) were isolated and shown to selectively inhibit iPLA(2gamma) and iPLA(2beta), respectively. The effect of these enantiomers on cell growth was assessed in human embryonic kidney 293 and Caki-1 cells using 3-(4-dimethylthiazolyl-2)-2,5-diphenyltetrazolium bromide (MTT). S-BEL (0-5.0 microM) decreased MTT staining 35% after 24 h compared with control cells, whereas treatment with either R-BEL or R/S-BEL induced 15% decreases. Neither R-BEL nor S-BEL induced cell death as determined by annexin V and propidium iodide staining. Transfection of cells with iPLA(2)beta siRNA reduced MTT staining approximately 35%, whereas transfection of cells with iPLA(2)gamma siRNA only decreased MTT staining 10 to 15% compared with control cells. The effect of iPLA(2)beta and iPLA(2)gamma siRNA on cell number and protein was also determined, and iPLA(2)beta siRNA decreased cell number and protein 25% compared with control cells. In contrast, iPLA(2)gamma siRNA decreased cell number, but not cellular protein, compared with control cells. Selective inhibition of iPLA(2)beta, but not iPLA(2)gamma, decreased several arachidonic acid-containing phospholipids, including 16:1-20:4, 16:0-20:4, 18:1-20:4, and 18:0-20:4 phosphatidylcholine, showing that the ability of iPLA(2)beta inhibitors to decrease cell growth correlates with their ability to decrease arachidonic acid-containing phospholipids. These data show that iPLA(2)beta inhibition results in greater decreases in cell growth and proliferation than iPLA(2)gamma, identifies specific phospholipids whose expressions are differentially regulated by iPLA(2)beta and iPLA(2)gamma, and suggests novel roles for iPLA(2)beta in cell growth.
authors.affiliation: Department of Pharmaceutical and Biomedical Sciences, University of Georgia, Athens, GA 30602, USA.
authors.forename: Geraldine
authors.initials: G
authors.lastname: Saavedra
authors.forename: Wenliang
authors.initials: W
authors.lastname: Zhang
authors.forename: Brianna
authors.initials: B
authors.lastname: Peterson
authors.forename: B S
authors.initials: BS
authors.lastname: Cummings
mesh_terms: D049109:Cell Proliferation; D002478:Cells, Cultured; D003600:Cytosol / Q000201:enzymology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D008861:Microsomes / Q000201:enzymology*; D010741:Phospholipases A / Q000037:antagonists & inhibitors / Q000502:physiology*; D054467:Phospholipases A2; D010743:Phospholipids / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000494:pharmacology
chemical_list: D004791:Enzyme Inhibitors; D010743:Phospholipids; D034741:RNA, Small Interfering; D010741:Phospholipases A; D054467:Phospholipases A2