Novel translocation responses of cytosolic phospholipase A2alpha fluorescent proteins.
Cytosolic phospholipase A2 (cPLA2)alpha responds to the rise in cytosolic Ca2+ ([Ca2+]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, cPLA2alpha translocation occurs without any corresponding changes in [Ca2+]i. The signal for such responses has not been identified. Using confocal microscopy to track fluorescent proteins fused to cPLA2alpha or cPLA2alpha's C2 domain, we find that AA mimics Ca2+ ionophores in stimulating cPLA(2)alpha translocations to the perinuclear ER and to a novel site, the lipid body. Unlike the ionophores, AA acted independently of [Ca2+](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 Ca2+-independent cPLA2alpha translocation and that lipid bodies are common targets of cPLA2alpha and contributors to stimulus-induced lipid mediator synthesis.
Wooten
Rhonda E
RE
Department of Internal Medicine, Section on Infectious Diseases, Wake Forest University Health Sciences, Medical Center Boulevard, Winston-Salem, NC 27157, USA.
Willingham
Mark C
MC
Daniel
Larry W
LW
Leslie
Christina C
CC
Rogers
LeAnn C
LC
Sergeant
Susan
S
O'Flaherty
Joseph T
JT
D002118:Calcium / Q000378:metabolism; D002460:Cell Line; D005456:Fluorescent Dyes / Q000032:analysis*; D006056:Golgi Apparatus / Q000201:enzymology; D054513:Group IV Phospholipases A2 / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008055:Lipids / Q000032:analysis; D008164:Luminescent Proteins / Q000032:analysis* / Q000235:genetics; D018613:Microscopy, Confocal; D015388:Organelles / Q000737:chemistry / Q000201:enzymology; D021381:Protein Transport
D005456:Fluorescent Dyes; D008055:Lipids; D008164:Luminescent Proteins; D054513:Group IV Phospholipases A2; D002118:Calcium