Studies of insulin secretory responses and of arachidonic acid incorporation into phospholipids of stably transfected insulinoma cells that overexpress group VIA phospholipase A(2) (iPLA(2)beta) indicate a signaling rather than a housekeeping role for iPLA(2)beta

Citation
Zm. Ma et al., Studies of insulin secretory responses and of arachidonic acid incorporation into phospholipids of stably transfected insulinoma cells that overexpress group VIA phospholipase A(2) (iPLA(2)beta) indicate a signaling rather than a housekeeping role for iPLA(2)beta, J BIOL CHEM, 276(16), 2001, pp. 13198-13208
Citations number
105
Language
INGLESE
art.tipo
Review
Categorie Soggetti
Biochemistry & Biophysics
Journal title
JOURNAL OF BIOLOGICAL CHEMISTRY
ISSN journal
0021-9258 → ACNP
Volume
276
Issue
16
Year of publication
2001
Pages
13198 - 13208
Database
ISI
SICI code
0021-9258(20010420)276:16<13198:SOISRA>2.0.ZU;2-C
Abstract
A cytosolic 84-kDa group VLA phospholipase A(2) (iPLA(2)beta) that does not require Ca2+ for catalysis has been cloned from several sources, including rat and human pancreatic islet beta -cells and murine P388D1 cells. Many p otential iPLA(2)beta functions have been proposed, including a signaling ro le in beta -cell insulin secretion and a role in generating lysophosphatidy lcholine accepters for arachidonic acid incorporation into P388D1 cell phos phatidylcholine (PC). Proposals for iPLA(2)beta function rest in part on ef fects of inhibiting iPLA(2)beta activity with a bromoenol lactone (BEL) sui cide substrate, but EEL also inhibits phosphatidate phosphohydrolase-1 and a group VIB phospholipase A(2). Manipulation of iPLA(2)beta expression by m olecular biologic means is an alternative approach to study iPLA(2)beta fun ctions, and we have used a retroviral construct containing iPLA(2)beta cDNA to prepare two INS-1 insulinoma cell clonal lines that stably overexpress iPLA(2)beta. Compared with parental INS-I cells or cells transfected with e mpty vector, both iPLA(2)beta -overexpressing lines exhibit amplified insul in secretory responses to glucose and cAMP-elevating agents, and EEL substa ntially attenuates stimulated secretion. Electrospray ionization mass spect rometric analyses of arachidonic acid incorporation into INS-1 cell PC indi cate that neither overexpression nor inhibition of iPLA(2)beta affects the rate or extent of this process in INS-1 cells. Immunocytofluorescence studi es with antibodies directed against iPLA(2)beta indicate that cAMP-elevatin g agents increase perinuclear fluorescence in INS-1 cells, suggesting that iPLA(2)beta associates with nuclei. These studies are more consistent with a signaling than with a housekeeping role for iPLA(2)beta in insulinsecreti ng 13-cells.