Electrical Remodeling of Connexin43 Gap‐Junction Protein Expression

Abstract

Backgrounds Altered gap-junction mediated intercellular communication and myocardial distribution of these channels have been implicated in mechanisms involved electrical conduction and synchronization of repolarization. We tested the hypothesis that electrical field stimulation can result in structural remodeling of gap junction channels and their myocardial spatial distribution. The effect of focal electrical pacing was assessed by quantifying the phosphorylation state of connexin43 (Cx43) protein. Methods Isolated adult-male rat hearts (n=12) were used. A microelectrode was positioned in the endocardial apical region of right ventricle. Electrical pacing stimulus (@300 bpm, 1.5V, 5msec) was maintained for 3-hrs. Immunoblotting and immunohistochemistry (Serine specific [Ser368] anti-Cx43 labeling) was used to assess the phosphorylation state of Cx43 and map its regional distribution. Results Myocardial tissue immunofluorescence of the region encompassing the stimulating electrode showed a consistent increase in dephosphorylation of Cx43 compared to remote regions. In control hearts (n=6), Cx43 was predominantly localized in a phosphorylated state. Western blotting analysis revealed that dephosphorylated form of Cx43 was notably greater (1.5 fold + −0.33) in the paced hearts. (p=0.059) Conclusions Cx43 expression and phosphorylation state was shown to be site-specific. Dephosphorylation was attributed to the electrical field-induced alteration. The apparent involvement of Ser368 in the gating of Cx43 suggests a mechanistic function in the gap-junctional intercellular communication.