Novel translocation responses of cytosolic phospholipase A2α fluorescent proteins

• Published in: Biochimica et biophysica acta 2008-08, Vol.1783 (8), p.1544-1550
• Main Authors: Wooten, Rhonda E., Willingham, Mark C., Daniel, Larry W., Leslie, Christina C., Rogers, LeAnn C., Sergeant, Susan, O'Flaherty, Joseph T.
• Format: Article
• Language: English
• ISSN: 0167-4889; 0006-3002
• DOI: 10.1016/j.bbamcr.2008.03.008

Cytosolic phospholipase A 2 (cPLA 2 )α responds to the rise in cytosolic Ca 2+ ([Ca 2+ ] i ) attending cell stimulation by moving to intracellular membranes, releasing arachidonic acid (AA) from these membranes, and thereby initiating the synthesis of various lipid mediators. Under some conditions, however, cPLA 2 α translocation occurs without any corresponding changes in [Ca 2+ ] i . The signal for such responses has not been identified. Using confocal microscopy to track fluorescent proteins fused to cPLA 2 α or cPLA 2 α’s C2 domain, we find that AA mimics Ca 2+ ionophores in stimulating cPLA 2 α translocations to the perinuclear ER and to a novel site, the lipid body. Unlike the ionophores, AA acted independently of [Ca 2+ ] i rises and did not translocate the proteins to the Golgi. AA’s action did not involve its metabolism to eicosanoids or acylation into cellular lipids. Receptor agonists also stimulated translocations targeting lipid bodies. We propose that AA is a signal for Ca 2+ -independent cPLA 2 α translocation and that lipid bodies are common targets of cPLA 2 α and contributors to stimulus-induced lipid mediator synthesis.