Differential activation of PKC-delta and -zeta by alpha 1-adrenergic stimulation in human airway epithelial cells

Abstract

Phorbol ester and alpha 1-adrenergic stimulation of Na-Cl-K cotransport in human tracheal epithelial cells was investigated by determining the expression of protein kinase C (PKC) isotypes and their activation by phorbol 12-myristate 13-acetate (PMA) and methoxamine, an alpha 1-adrenergic agonist. PKC-alpha, -beta II, -delta, -epsilon, and -zeta were expressed in confluent cell cultures. PKC-beta I, -gamma, and -eta were not detected. PKC-alpha and -zeta were localized to the cytosol, and PKC-beta II and -delta were distributed approximately evenly between cytosolic and particulate fractions. Treatment with PMA for 30 min increased PKC activity in subcellular fractions and induced a redistribution of PKC-beta II and -delta to a particulate fraction. PMA treatment for 18 h reduced PKC activity to levels found in untreated cells and reduced, but did not deplete, PKC isotype mass. Methoxamine transiently increased PKC activity, with maximal levels at 40 s, and caused a shift in PKC-delta and -zeta mass to a particulate fraction. Methoxamine selectively induced a sustained increase in PKC-zeta activity but only a transient increase in PKC-delta. These results suggest that PKC-delta and -zeta mediate hormonal activation of Na-Cl-K cotransport.