Abstract
Cytosolic phospholipase A(2)gamma (cPLA(2)gamma) is a member of the group IV family of intracellular phospholipase A(2) enzymes, but unlike the well-studied cPLA(2)alpha, it is constitutively bound to membrane and is calcium independent. cPLA(2)gamma contains a C-terminal CaaX sequence and is radiolabeled by mevalonic acid when expressed in cPLA(2)alpha-deficient immortalized lung fibroblasts (IMLF(-/-)). The radiolabel associated with cPLA(2)gamma was identified as the farnesyl group. The protein farnesyltransferase inhibitor BMS-214662 prevented the incorporation of [(3)H]mevalonic acid into cPLA(2)gamma and partially suppressed serum-stimulated arachidonic acid release from IMLF(-/-) and undifferentiated human skeletal muscle (SkMc) cells overexpressing cPLA(2)gamma, but not from cells overexpressing cPLA(2)alpha. However, BMS-214662 did not alter the amount of cPLA(2)gamma associated with membrane. These results were consistent in COS cells expressing the C538S cPLA(2)gamma prenylation mutant. cPLA(2)gamma also contains a classic myristoylation site and several potential palmitoylation sites and was found to be acylated with oleic and palmitic acids but not myristoylated. Immunofluorescence microscopy revealed that cPLA(2)gamma is associated with mitochondria in IMLF(-/-), SkMc cells, and COS cells.
Highlights
Cytosolic phospholipase A2␥ is a member of the group IV family of intracellular phospholipase A2 enzymes, but unlike the well-studied cytosolic phospholipase A2 (cPLA2)␣, it is constitutively bound to membrane and is calcium independent. cytosolic phospholipase A2s (cPLA2s)␥ contains a C-terminal CaaX sequence and is radiolabeled by mevalonic acid when expressed in cPLA2␣-deficient immortalized lung fibroblasts (IMLF؊/؊)
CPLA2␥ is farnesylated in mammalian cells IMLFϪ/Ϫ infected with Ad-cPLA2␥ were grown in the presence of [3H]mevalonic acid followed by immunoprecipitation of cPLA2␥
The results of this study demonstrate that cPLA2␥ is farnesylated in mammalian cells and document that prenylation plays a role in cPLA2␥-induced fatty acid hydrolysis
Summary
Cytosolic phospholipase A2␥ (cPLA2␥) is a member of the group IV family of intracellular phospholipase A2 enzymes, but unlike the well-studied cPLA2␣, it is constitutively bound to membrane and is calcium independent. cPLA2␥ contains a C-terminal CaaX sequence and is radiolabeled by mevalonic acid when expressed in cPLA2␣-deficient immortalized lung fibroblasts (IMLF؊/؊). Cytosolic phospholipase A2␥ (cPLA2␥) is a member of the group IV family of intracellular phospholipase A2 enzymes, but unlike the well-studied cPLA2␣, it is constitutively bound to membrane and is calcium independent. Phospholipases A2 (PLA2s) hydrolyze the sn-2 ester bond of membrane phospholipids and function in the production of lipid mediators, phospholipid acyl-chain remodeling, dietary lipid breakdown, and host defense. Convention divides this family into three main types based on their subcellular localizations and structural differences: the secreted PLA2s, the intracellular group IV cytosolic phospholipase A2s (cPLA2s), and the group VI cal-.
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