DIFFERENTIAL ACTIVATION OF PKC-DELTA AND PKC-ZETA BY ALPHA(1)-ADRENERGIC STIMULATION IN HUMAN AIRWAY EPITHELIAL-CELLS

Phorbol ester and alpha(1)-adrenergic stimulation of Na-Cl-K cotranspo rt 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(1), -gamma, and - eta were not detected. PKC-alpha and -zeta were localized to the cytos ol, 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 red istribution of PKC-beta(II) and -delta to a particulate fraction. PMA treatment for 18 h reduced PKC activity to levels found in untreated c ells and reduced, but did not deplete, PKC isotype mass. Methoxamine t ransiently increased PKC activity, with maximal levels at 40 s, and ca used a shift in PKC-delta and -zeta mass to a particulate fraction. Me thoxamine selectively induced a sustained increase in PKC-zeta activit y but only a transient increase in PKC-delta. These results suggest th at PKC-delta and -zeta mediate hormonal activation of Na-Cl-K cotransp ort.