Platelet-derived growth factor-induced disruption of gap junctional communication and phosphorylation of connexin43 involves protein kinase C and mitogen-activated protein kinase

• Published in: Journal of cellular physiology Vol. 176; no. 2; pp. 332 - 341
• Main Authors: Hossain, Mohammad Z., Ao, Peng, Boynton, Alton L.
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc., A Wiley Company 01.08.1998
• Subjects: Animals; Calcium-Calmodulin-Dependent Protein Kinases - metabolism; Carcinogens - pharmacology; Cell Communication - drug effects; Cell Communication - physiology; Connexin 43 - metabolism; Enzyme Inhibitors - pharmacology; Epithelial Cells - chemistry; Epithelial Cells - drug effects; Epithelial Cells - enzymology; Gap Junctions - drug effects; Gap Junctions - physiology; Liver - cytology; Naphthalenes - pharmacology; Phosphorylation; Platelet-Derived Growth Factor - pharmacology; Protein Kinase C - antagonists & inhibitors; Protein Kinase C - metabolism; Rats; Tetradecanoylphorbol Acetate - pharmacology
• ISSN: 0021-9541; 1097-4652
• DOI: 10.1002/(SICI)1097-4652(199808)176:2<332::AID-JCP11>3.0.CO;2-5

Previously we showed a rapid and transient inhibition of gap junctional communication (GJC) by platelet‐derived growth factor (PDGF) in T51B rat liver epithelial cells expressing wild‐type platelet‐derived growth factor β receptors (PDGFrβ). This action of PDGF correlated with the hyperphosphorylation of the gap junction protein connexin43 (Cx43) and required PDGFrβ tyrosine kinase activity, suggesting the participation of protein kinases and phosphatases many of which are activated by PDGF treatment. In the present study, two such kinases, namely protein kinase C (PKC) and mitogen‐activated protein kinase (MAPK), are investigated for their possible involvement in PDGF‐induced closure of junctional channels and Cx43‐phosphorylation. Down‐regulation of PKC‐isoforms by 12‐O‐tetradecanoylphorbol‐13‐acetate or pretreatment with the PKC inhibitor calphostin C, completely blocked PDGF action on GJC and Cx43. Activation of MAPK correlated with PDGF‐induced Cx43 phosphorylation, and prevention of MAPK activation by PD98059 eliminated the PDGF effects. Interestingly, elimination of GJC recovery by cycloheximide was associated with a sustained activated‐MAPK level. Based on these results we postulate that the activation of PKC and MAPK are required in PDGF‐mediated Cx43 phosphorylation and junctional closure. J. Cell. Physiol. 176:332–341, 1998. © 1998 Wiley‐Liss, Inc.