Cysteine string protein (CSP) Alpha, DNAJC5 alpha

May have an important role in presynaptic function. May be involved in calcium-dependent neurotransmitter release at nerve endings. The amino terminus of CSP contains the J domain, a consensus sequence found on a DnaJ like protein which is a member of the heatshock protein family. Since heat shock proteins serve as chaperones that participate in protein folding and protein complex formation, CSP is believed to perform similar functions in the assembly of synaptic vesicle proteins which are essential to membrane trafficking. Evidence for a role of CSP in presynaptic neurotransmitter release has come from genetic and physiological study in which the Drosophila CSP null mutant fails to elicit synaptic potential upon high frequency stimulation. CSP null mutants have a lethal phenotype and for the small percentage of mutant flies that survive, they become paralyzed and die at elevated temperature.