Phospholipase A2 and signal transduction.

Phospholipases A2 (PLA2) comprise a family of enzymes that hydrolyze the acyl bond at the sn-2 position of phospholipids to generate free fatty acids and lysophospholipids. Different forms of PLA2 are involved in digestion, inflammation, and intercellular and intracellular signal transduction. The sn-2 position of phospholipids in mammalian cells is enriched in arachidonic acid, the precursor of eicosanoids, which have diverse physiologic and pathophysiologic effects on the kidney and other organs. Thus, the regulation of PLA2 activity has important implications for kidney function. PLA2 regulation involves: calcium, pH, protein kinases, GTP-binding proteins, inhibitory and activating proteins, metabolic product inhibition, and transcriptional control. The various roles of arachidonic acid and cyclooxygenase, lipoxygenase, and cytochrome P450 mono-oxygenase products of arachidonic acid metabolism, as intracellular messengers, in the regulation of membrane channel activities, intracellular enzyme activities, cellular calcium homeostasis, mitogenesis, differentiation, cytokine and early response gene expression are discussed.