Effect of the Epac Activator 8-Pcpt-2 '-O-me-camp (8-Pcpt) on the Expression Pattern of Ve-Cadherin (Ve-Cad) & Connexins (cxs) in Human Coronary Artery Endothelial Cells (Hcaecs)

Homocellular junctions between endothelial cells include adherens junctions, formed by cadherins, & gap junctions, formed by Cxs. Dynamic regulation of these junctions is necessary to maintain the endothelial barrier. We examined the effect of Ca2+ & 8‐pCPT, a selective activator of exchange protein directly activated by cAMP (Epac), on the expression pattern of VE‐cad & Cxs in HCAECs. VE‐cad, Cx37, 40 & 43 were identified in HCAECs by immunocytochemistry. VE‐cad was identified in parts of the cell membrane, without overlapping with Cx37, 40 or 43. Application of 8‐pCPT produced more continuous VE‐cad membrane staining that overlapped with Cx37. Disruption of VE‐cad interactions using VE‐cad antibody changed HCAEC morphology from flattened & continuous to small dispersed colonies. Removal of Ca2+ from medium resulted in rounded cells isolated from each other. Following Ca2+ restoration, a normal pattern of VE‐cad membrane staining returned, followed by return of membrane Cx staining. Addition of VE‐cad antibody blocked this recovery. Epac activation promotes localisation of VE‐cad to the membrane & adherens junction formation. Redistribution of VE‐cad has a subsequent effect on Cx localisation. Adherens junction formation in HCAECs therefore precedes & promotes Cx interactions at cell junctions. Funded by the University of Liverpool