Selective action of uncoating ATPase towards clathrin-coated vesicles from brain

Clathrin-coated vesicles from brain are primarily involved in synaptic vesicle recycling and are substrates for the constitutively expressed heat shock cognate hsc70 protein (uncoating ATPase). To investigate the regulation of clathrin coat turnover in other tissues the activity of hsc70 towards coated vesicles from other sources was examined. Concentrations of hsc70 which caused near-complete removal of clathrin from brain coated vesicles effected only partial uncoating of vesicles prepared from other tissues. The selective action of hsc70 could not be accounted for by tissue or species specificities of hsc70, but rather reflected differences in coat structure. Selective action was associated with two differences in the hsc70-dependent ATPase cycle. Firstly, uncoating of brain, but not placental vesicles, could occur under circumstances where ATP hydrolysis was prevented. Secondly, only brain coated vesicles could support multiple rounds of hsc70-dependent ATP hydrolysis. Implications of these findings for the mechanism of hsc70-dependent vesicle uncoating in non-neuronal cells and the organisation of the endocytic pathway in the axon are discussed.