Studies of Insulin Secretory Responses and of Arachidonic Acid Incorporation into Phospholipids of Stably Transfected Insulinoma Cells That Overexpress Group VIA Phospholipase A2 (iPLA2β) Indicate a Signaling Rather Than a Housekeeping Role for iPLA2β

Zhongmin Ma, Sasanka Ramanadham, Mary Wohltmann, Alan Bohrer, Fong Fu Hsu, John Turk

Research output: Contribution to journalArticlepeer-review

75 Scopus citations

Abstract

A cytosolic 84-kDa group VIA phospholipase A2 (iPLA 2β) that does not require Ca2+ for catalysis has been cloned from several sources, including rat and human pancreatic islet β-cells and murine P388D1 cells. Many potential iPLA2β functions have been proposed, including a signaling role in β-cell insulin secretion and a role in generating lysophosphatidylcholine acceptors for arachidonic acid incorporation into P388D1 cell phosphatidylcholine (PC). Proposals for iPLA2β function rest in part on effects of inhibiting iPLA2β activity with a bromoenol lactone (BEL) suicide substrate, but BEL also inhibits phosphatidate phosphohydrolase-1 and a group VIB phospholipase A2. Manipulation of iPLA2β expression by molecular biologic means is an alternative approach to study iPLA2β functions, and we have used a retroviral construct containing iPLA2β cDNA to prepare two INS-1 insulinoma cell clonal lines that stably overexpress iPLA2β. Compared with parental INS-1 cells or cells transfected with empty vector, both iPLA 2β-overexpressing lines exhibit amplified insulin secretory responses to glucose and cAMP-elevating agents, and BEL substantially attenuates stimulated secretion. Electrospray ionization mass spectrometric analyses of arachidonic acid incorporation into INS-1 cell PC indicate that neither overexpression nor inhibition of iPLA2β affects the rate or extent of this process in INS-1 cells. Immunocytofluorescence studies with antibodies directed against iPLA2β indicate that cAMP-elevating agents increase perinuclear fluorescence in INS-1 cells, suggesting that iPLA2β associates with nuclei. These studies are more consistent with a signaling than with a housekeeping role for iPLA 2β in insulin-secreting β-cells.

Original languageEnglish
Pages (from-to)13198-13208
Number of pages11
JournalJournal of Biological Chemistry
Volume276
Issue number16
DOIs
StatePublished - Apr 20 2001

Fingerprint Dive into the research topics of 'Studies of Insulin Secretory Responses and of Arachidonic Acid Incorporation into Phospholipids of Stably Transfected Insulinoma Cells That Overexpress Group VIA Phospholipase A<sub>2</sub> (iPLA<sub>2</sub>β) Indicate a Signaling Rather Than a Housekeeping Role for iPLA<sub>2</sub>β'. Together they form a unique fingerprint.

Cite this