Perinuclear localization of cytosolic phospholipase A(2)alpha is important but not obligatory for coupling with cyclooxygenases.

In response to Ca(2+) signaling, cytosolic phospholipase A(2)alpha (cPLA(2)alpha) translocates from the cytosol to the perinuclear membrane, where downstream eicosanoid-synthetic enzymes, such as cyclooxygenase (COX), are localized. Although the spatiotemporal perinuclear colocalization of cPLA(2)alpha and COXs has been proposed to be critical for their functional coupling leading to prostanoid production, definitive evidence for this paradigm has remained elusive. To circumstantiate this issue, we took advantage of a chimeric cPLA(2)alpha mutant harboring the C2 domain of protein kinase Calpha, which translocates to the plasma membrane following cell activation. Transfection analyses of the native or chimeric cPLA(2)alpha in combination with COX-1 or COX-2 revealed that, even though the arachidonate-releasing capacities of native and mutant cPLA(2)alpha were comparable, prostaglandin production by mutant cPLA(2)alpha was markedly impaired as compared with that by native cPLA(2)alpha. We thus conclude that the perinuclear localization of cPLA(2)alpha is preferential, even if not obligatory, for efficient coupling with COXs.