Engineered connexin40 variants increased docking and function of heterotypic connexin40/connexin43 gap junction channels

Gap junction (GJ) channels provide low resistance passage for rapid action potential propagation in the heart. Both connexin40 (Cx40) and Cx43 are abundantly expressed in and frequently co-localized between atrial myocytes, possibly forming heterotypic GJ channels. However, conflicting results have been obtained on the functional status of heterotypic Cx40/Cx43 GJs. Here we provide experimental evidence that the docking and formation of heterotypic Cx40/Cx43 GJs can be substantially increased by properly designed Cx40 variants where the extracellular domains (E1 and E2) have been modified. Specifically, Cx40 D55N and P193Q; substantially increased the probability to form GJ plaque-like structures at the cell-cell interfaces with Cx43. More importantly the coupling conductance (Gj) of D55N/Cx43 and P193Q/Cx43 GJ channels are significantly increased from the Gj of Cx40/Cx43. Our homology models indicate the electrostatic interactions and surface structures at the docking interface are key factors preventing Cx40 from docking to Cx43. Improving heterotypic Gj of these atrial connexins may be potentially useful in improving the coupling and synchronization of atrial myocardium