Studies of phospholipid metabolism, proliferation, and secretion of stablytransfected insulinoma cells that overexpress group VIA phospholipase A(2)

Citation
Zm. Ma et al., Studies of phospholipid metabolism, proliferation, and secretion of stablytransfected insulinoma cells that overexpress group VIA phospholipase A(2), LIPIDS, 36(7), 2001, pp. 689-700
Citations number
95
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Agricultural Chemistry","Biochemistry & Biophysics
Journal title
LIPIDS
ISSN journal
0024-4201 → ACNP
Volume
36
Issue
7
Year of publication
2001
Pages
689 - 700
Database
ISI
SICI code
0024-4201(200107)36:7<689:SOPMPA>2.0.ZU;2-#
Abstract
A cytosolic 84 kDa Croup VIA phospholipase A(2) (iPLA(2)beta) that does not require Call for catalysis was cloned from Chinese hamster ovary (CHO) cel ls, murine P388D1 cells, pancreatic islet beta -cells, and other sources, P roposed iPLA(2)beta functions include participation in phosphatidylcholine (PC) homeostasis by degrading excess PC generated in CHO cells that overexp ress CTP:phosphocholine cytidylyltransferase (CT), which catalyzes the rate -limiting step in PC biosynthesis; participation in biosynthesis of arachid onate-containing PC species in P388D1 cells by generating lysophosphatidylc holine (LPC) acceptors for arachidonate incorporation; and participation in signaling events in insulin secretion from islet beta -cells. To further e xamine iPLA(2)beta functions in beta -cells, we prepared stably transfected INS-I insulinoma cell lines that overexpress iPLA(2)beta activity eightfol d compared to parental INS-1 cells or to INS-1 cells transfected with an em pty retroviral vector that did not contain iPLA(2)beta cDNA. The iPLA(2)bet a -overexpressing cells exhibit a twofold increase in CT activity compared to parental cells but little change in rates of [H-3]choline incorporation into or disappearance from PC. Electrospray ionization (ESI) tandem mass sp ectrometric measurements indicate that iPLA(2)beta -overexpressing cells ha ve 1.5-fold higher LPC levels than parental INS-1 cells but do not exhibit increased rates of [H-3]arachidonate incorporation into phospholipids, and incorporation is unaffected by a bromoenol lactone (BEL) suicide substrate inhibitor of iPLA(2)beta. The rate of appearance of arachidonate-containing phosphatidylethanolamine species visualized by ESI mass spectrometry is al so similar in iPLA(2)beta -overexpressing and parental INS-1 cells incubate d with supplemental arachidonic acid, and this process is unaffected by BEL . Compared to parental INS-1 cells, iPLA(2)beta -overexpressing cells proli ferate more rapidly and exhibit amplified insulin secretory responses to a protein kinase C-activating phorbol ester, glucose, and a cAMP analog. Thes e findings suggest that iPLA(2)beta plays a signaling role in beta -cells t hat differs from housekeeping functions in PC biosynthesis and degradation in P388D1 and CHO cells.