Translocation of synapsin I in response to depolarization of isolated nerve terminals.

AUTOR(ES)

Sihra, T S

RESUMO

Depolarization of isolated nerve terminals (synaptosomes) has been shown to stimulate neurotransmitter release and to increase the phosphorylation state of a number of proteins, including synapsin I, in a Ca2+-dependent manner. Synapsin I, a prominent nerve terminal phosphoprotein, interacts with the cytoplasmic surface of small synaptic vesicles and with cytoskeletal elements in a phosphorylation-dependent manner. In the present study we have found that depolarization of synaptosomes resulted in a rapid (2-5 sec) translocation of synapsin I from the particulate to the cytosolic (soluble) fraction. This translocation of synapsin I correlated with its phosphorylation state and was dependent on the presence of Ca2+ in the incubation medium. The stoichiometry of phosphorylation of soluble synapsin I was considerably higher than that of synapsin I in the particulate fraction, under both basal and depolarizing conditions. These data are consistent with the hypothesis that, in situ, the phosphorylation of synapsin I promotes its translocation from synaptic vesicles/cytoskeleton to the cytosol. This phosphorylation/translocation may be instrumental in regulating the release of neurotransmitter.

Documentos Relacionados

• Membrane depolarization and carbamoylcholine stimulate phosphatidylinositol turnover in intact nerve terminals.
• Localization of cholecystokinin-like immunoreactivity in isolated nerve terminals.
• Phosphorylation and associated translocation of the 87-kDa protein, a major protein kinase C substrate, in isolated nerve terminals.
• Vasoactive intestinal polypeptide in brain: localization in and release from isolated nerve terminals.
• Calcium sensing receptor: molecular cloning in rat and localization to nerve terminals.