Cysteine strings, calcium channels and synaptic transmission.

Multidisciplinary studies have led to the discovery and characterization of cysteine string proteins (csps) in both Drosophila and Torpedo. Phenotypic analysis of csp mutants in Drosophila demonstrates a crucial role for csp in synaptic transmission. Expression studies of Torpedo csp (Tcsp) in Xenopus oocytes suggests that the protein has some role in the function of presynaptic Ca2+ channels. However, biochemical purification of Tcsp indicates that is associated with synaptic vesicles rather than with the plasma membrane of presynaptic terminals where Ca2+ channels reside. These results suggest a model in which csps serve as a link by which docked synaptic vesicles could modulate the activity of presynaptic Ca2+ channels.