Phosphorylation shifts unitary conductance and modifies voltage dependent kinetics of human connexin43 gap junction channels

when applied to cells of differenttissues (e.g., 3). These different effects may be attribut­able to the different complements of gap junctionproteins expressed by the different cell types, to tissue­specific as distinct from connexin-specificeffects, ormayrepresent effects on distinct synthetic or processingstages in the expression pathway (4). To evaluate theeffects ofphosphorylating and dephosphorylating treat­ments on gating properties (voltage dependence andunitary conductance) of gap junctions formed of aknown connexin, we transfected a communication­deficient cell line (SKHep1) with cDNA encoding hu­man connexin43 (hCx43;5). Furthermore, we comparedthe gating properties of the wild type channels withthose truncated so as to remove the phosphorylationsites (6). These studies indicate that unitary conduc­tance and voltage dependent kinetics (but not equilib­rium) properties ofthe human connexin43 gap junctionchannel are affected by phosphorylation, and that thepresence ofthe carboxyl terminal phosphorylation sitesis not required for functional expression of junctionalchannels.