Intracellular calcium signals regulating cytosolic phospholipase A2 translocation to internal membranes

Increased intracellular Ca2+ concentrations ([Ca2+](i)) promote cytosolic phospholipase A(2) (cPLA(2)) translocation to intracellular membranes. The specific membranes to which cPLA(2) translocates and the [Ca2+](i) signals required were investigated. Plasmids of EGFP fused to full-length cPLA(2) (EGFP-FL) or to the cPLA(2) C2 domain (EGFP-C2) were used in C2+/EGFP imaging experiments of cells treated with [Ca2+](i)-mobilizing agonists. EGFP-FL, and -C2 translocated to Golgi in response, to sustained [Ca2+](i) greater than similar to 100-125 nM and to Golgi,. ER, and perinuclear membranes (PNM) at [Ca2+](i) greater than similar to 210-280 nm. In response to short duration [Ca2+](i) transients, EGFP-C2 translocated to Golgi, ER, and PNM, but EGFP-FL translocation was restricted to Golgi. However, EGFP-FL translocated to Golgi, ER, and PNM in response to long, duration transients. In response to declining, [Ca2+](i), EGFP-C2 readily dissociated from Golgi, but EGFP FL dissociation was delayed. Agonist-induced arachidonic acid release was proportional to the [Ca2+](i) and to the extent of cPLA(2) translocation. In summary, we, find that the differential translocation of cPLA(2) to Golgi or to ER and PNM is a function of [Ca2+](i) amplitude and duration., These results suggest that the cPLA(2), C2 domain regulates differential, Ca2+-dependent membrane targeting and that the catalytic domain regulates both the rate of translocation and enzyme residence.