Phenylarsine Oxide and H₂O₂ Plus Vanadate Induce Reverse Translocation of Phorbol-Ester-Activated PKCβII

Abstract

The intracellular localization of protein kinase C (PKC) is important for the regulation of its biological activity. Recently, it was reported that, whereas phorbol esters such as PMA induce prolonged translocation of PKC to the plasma membrane, with physiological stimuli, the translocation of PKC is transient and followed by rapid return to the cytoplasm. In addition, this membrane dissociation of PKC was shown to require both the kinase activity of PKC and the phosphorylation of its carboxyl terminus autophosphorylation sites. However, the detailed molecular mechanism of PKC reverse translocation remains obscure. We demonstrated that in porcine polymorphonuclear leucocytes (PMNs), phenylarsine oxide (PAO), a putative protein tyrosine phosphatase (PTPase) inhibitor, induced reverse translocation of PMA-stimulated PKCβII. Hydrogen peroxide (H₂O₂) in combination with vanadate, both of which are PTPase inhibitors, also induced reverse translocation of PKCβII. H₂O₂ or vanadate alone had little effect on PMA-induced PKCβII translocation. Furthermore, genistein and ethanol, which are inhibitors of tyrosine kinase and phospholipase D, respectively, prevented the PKCβII reverse translocation induced by the PTPase inhibitors. These results indicate, for the first time, that the tyrosine phosphorylation/phospholipase D pathway may be involved in the process of membrane dissociation of PKC.