IN-SITU REGULATION OF CELL-CELL COMMUNICATION BY THE CAMP-DEPENDENT PROTEIN-KINASE AND PROTEIN-KINASE-C

The effects of cAMP-dependent protein kinase A and protein kinase C on cell-cell communication have been examined in primary ovarian granulo sa cells microinjected with purified components of these two regulator y cascades. These cells possess connexin43 (alpha 1)-type gap junction s, and are well-coupled electrotonically and as judged by the cell-to- cell transfer of fluorescent dye. Within 2-3 min after injection of th e protein kinase A inhibitor (PKI) communication was sharply reduced o r ceased, but resumed in about 3 min with the injection of the protein kinase A catalytic subunit. A similar resumption also occurred in PKI -injected cells after exposure to follicle stimulating hormone. Microi njection of the protein kinase C inhibitor protein caused a transient cessation of communication that spontaneously returned within 15-20 mi n. Treatment of cells with activators of protein kinase C, TPA or OAG for 60 min caused a significant reduction in communication that could be restored within 2-5 min by the subsequent injection of either the p rotein kinase C inhibitor or the protein kinase A catalytic subunit. W ith a longer exposure to either protein kinase C activator communicati on could not be restored and this appeared to be related to the absenc e of aggregates of connexin43 in membrane as detected immunologically. In cells injected with alkaline phosphatase communication stopped but returned either spontaneously within 20 min or within 2-3 min of inje cting the cell with either the protein kinase A catalytic subunit or w ith protein kinase C. When untreated cells were injected with protein kinase C communication diminished or ceased within 5 min. Collectively these results demonstrate that cell-cell communication is regulated b y both protein kinase A and C, but in a complex interrelated manner, q uite likely by multiple phosphorylation of proteins within or regulati ng connexin-43 containing gap junctions. (Mel Cell Biochem 127/128: 29 3-307, 1993)