Role of Angiotensin II Type 1A Receptor Phosphorylation, Phospholipase D, and Extracellular Calcium in Isoform-specific Protein Kinase C Membrane Translocation Responses

Abstract

The angiotensin II type 1A receptor (AT(1A)R) plays an important role in cardiovascular function and as such represents a primary target for therapeutic intervention. The AT(1A)R is coupled via G(q) to the activation of phospholipase C, the hydrolysis of phosphoinositides, release of calcium from intracellular stores, and the activation of protein kinase C (PKC). We show here that PKCbetaI and PKCbetaII exhibit different membrane translocation patterns in response to AT(1A)R agonist activation. Whereas PKCbetaII translocation to the membrane is transient, PKCbetaI displays additional translocation responses: persistent membrane localization and oscillations between the membrane and cytosol following agonist removal. The initial translocation of PKCbetaI requires the release of calcium from intracellular stores and the activation of phospholipase C, but persistent membrane localization is dependent upon extracellular calcium influx. The mutation of any of the three PKC phosphorylation consensus sites (Ser-331, Ser-338, and Ser-348) localized within the AT(1A)R C-tail significantly increases the probability that persistent increases in diacylglycerol levels and PKCbetaI translocation responses will be observed. The persistent increase in AT(1A)R-mediated diacylglycerol formation is mediated by the activation of phospholipase D. Although the persistent PKCbetaI membrane translocation response is absolutely dependent upon the PKC activity-dependent recruitment of an extracellular calcium current, it does not require the activation of phospholipase D. Taken together, we show that the patterning of AT(1A)R second messenger response patterns is regulated by heterologous desensitization and PKC isoform substrate specificity.