Role of protein kinase C in the regulation of gap junctional communication

Abstract

We have examined the effect of protein kinase (PKC) depletion in SV40-transformed Djungarian hamster fibroblasts (DM15 cells) on the level of gap junction permeability. Cx43 electrophoretic mobility, and cell sensitivity to different uncoupling stimuli. After 24 hr exposure to 12-O-tetradecanoyl-phorbol-13-acetate (TPA), the total PKC activity in DM15 cells was reduced to 20-25% in comparison with intact cells. In PKC-depleted cells the level of dye coupling was 30-40% higher than in the same untreated cultures. Western blot analysis revealed multiple forms of the gap junction protein connexin 43, which correspond to known phosphorylated and dephosphorylated forms of this protein. No decrease in the level of connexin 43 phosphorylation after PKC depletion was observed. TPA (10(-7) g/ml), mezerein (10(-7) g/ml), teleocidin (10(-8) g/ml), Ca-ionophore A23187 (10(-6) g/ml), insecticide 1,1,1-trichloro-2,2-bis-(p-chlorphenyl)-ethane (DDT) (10(-4) g/ml), and nigericin (10(-5) M in hydrolysate lactalbumin solution, pH 6.3) induced a four-to six-fold decrease in the number of recipient cells in the dye-coupling assay. PKC-depleted cells became almost completely resistant to the uncoupling effect of mezerein, teleocidin, and A23187, as well as to new exposure to TPA, and became partially resistant to the effect of DDT. Nigericin inhibited intercellular communication between PKC-depleted cells to the same extent as between control cells. Thus, in the cell system studied, PKC plays a certain role in maintaining the basal level of gap junction permeability and has an important significance as a mediator of the uncoupling effects of such substances as TPA, mezerein, teleocidin, and Ca2+.

Connexin43 in Rat Oocytes: Developmental Modulation of Its Phosphorylation1

“…Along this line, changes in the phosphorylation state of Cx43, in FT2 10 cells that contain a temperature-sensitive mutation in the p34 cdc2 kinase, have also been reported [54]. Phosphorylation of Cx43 mediated by other kinases such as protein kinase C [54][55][56], Cyclic AMP-dependent protein kinase A [17,56,57], mitogenactivated protein kinase [56,57], and tyrosine kinases in transformed cells [58], has previously been reported.…”

High glucose induces alteration of gap junction permeability and phosphorylation of connexin-43 in cultured aortic smooth muscle cells.

“…One mechanism responsible for regulating GJIC activity is the PKC-dependent gating of the channels of gap junctions by phosphorylating connexins posttranslationally (32,34,35). Matesic et al (32) and others (36)(37)(38) have reported that PKC regulates GJIC activity by directly phosphorylating connexins in rat liver epithelial cells or other cells in culture. Gap junction protein connexins are encoded by a gene family; members of this family are differentially expressed in various types of tissue (23,24).…”

Lipopolysaccharide plus hypoxia and reoxygenation synergistically reduce electrical coupling between microvascular endothelial cells by dephosphorylating Connexin40

“…The role of PKC or PKA in gap junctional communication has been studied mainly for Cx43 (Budunova et al, 1994;Richards et al, 2004). Outside of one report addressing the effect of PKA activation on macroscopic gap junctional conductance in communication-deficient HeLa cells transfected with Cx40 (van Rijen et al, 2000), our laboratory has been the first to address the role of these kinases in Cx40 function in endothelial cells subjected to pathophysiological conditions.…”