Phospholipase C beta 2 in vascular smooth muscle

Receptor-mediated inositol 1,4,5-trisphosphate formation in most tissue is dependent on a variety of phospholipase C isoforms. To determine which phospholipase C isoforms were present in vascular smooth muscle compared to brain, liver, and spleen, we extracted proteins from these tissues and separated and identified the phospholipase C isoforms by immunoblotting. Aliquots of rat tail artery were examined by this procedure, together with aliquots of rat liver, spleen, cerebral cortex, hippocampus, cerebellum, aorta, and mesenteric artery. Phospholipase C gamma 1 was shown to be present in all of these tissues, while phospholipase C beta 1 was shown to be limited to fractions from brain. Phospholipase C delta 1 was detected in rat tail artery, mesenteric artery, aorta, and brain. Phospholipase C beta 2 was found in rat tail artery, liver, and brain. This is the first report of phospholipase C beta 2 in tissues other than HL60 cells. Since G proteins activate IP3 production via stimulation of phospholipase C beta isoforms in many tissues, and agonist-stimulated IP3 production in smooth muscle requires G protein activation, phospholipase C beta 2 may be required for agonist-stimulated force production in vascular smooth muscle.