ABSTRACT

Experiments performed by internally perfusing coupled crayfish lateral axons have yielded results which are relevant to the understanding of the regulatory cellular mechanisms of junctional communication. These results propose that control of junctional channels is performed by two mechanisms: one that controls channel closure and that depends on direct binding of calcium to the junctional proteins, and another mechanism that determines the availability of the binding sites for calcium, involving protein phosphorylation. The chapter proposes that closed junctional channels, on binding calcium (Ca++) activated calmodulin, split into hemichannels that disperse in the membrane surrounding the junction. It suggests that gap junction channels are sensitive to Ca++, and that protein phosphorylation determines the degree of sensitivity. The hypothesis can be successfully applied towards interpreting many results reported in the literature, and further suggests that junctional regulation involves the interplay of various enzymatic systems.