0111: Contribution of Cx43 and Cx40 in regulating the gap junction channel make-up and electrical properties

Abstract

Gap junction channels (GJC) provide the direct electrical and chemical cell-to-cell communication. Their electrical properties are considered as a key factor for regulating the impulse propagation through the cardiac network, which ensures the coordinated atrial and ventricular contractions. GJC are made of connexins that display distinct specific expression patterns in the different cardiac tissues. Atrial myocytes co-express connexin 43 (Cx43), Cx40 and traces of Cx45 with varying expression levels and ratio in the healthy and diseased heart. The aim of this study is to investigate the distinct contribution of Cx40 and Cx43 in the GJC make-up and electrical properties. Rat Liver Epithelial (RLE) cells that express Cx43 and stably transfected to co-express Cx40 at accurate Cx43:Cx40 ratios of 0.5, 1 and 2, are used. Dual voltage clamp recordings on cell pairs are performed to determine the electrical properties of GJC at each ratio. Compared to single Cx43 expression, we observed that the electrical coupling decreases at low induction of Cx40 (Cx43:Cx40 =2), but increases at lower Cx43:Cx40 ratios. Interestingly, the voltage dependence and the kinetics of deactivation of GJC are lowered and slower, respectively: the higher the induction of Cx40, the stronger the effects. Preliminary experiments that investigate the kinetics of recovery from deactivation show that Cx40 induction slower or accelerate the recovery in function of the level of induction and the Vj amplitude. Single channel recordings are under investigation to correlate the electrical properties to the GJC make-up. These results suggest a distinct contribution of Cx43 and Cx40 in the GJC make-up and function, which depends on the Cx43:Cx40 ratio. These findings will improve our understanding on the gap junction channels make-up by Cx43 and Cx40, and how this is translated into specific conduction velocities of the cardiac impulse propagation in the healthy and diseased heart.