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  • Synaptotagmin I increase the probability of vesicle fusion at low (Ca2+) in pituitary cells
    Kreft, Marko ...
    Synaptotagmin (Syt I), a low-affinity Ca2+ -binding protein, is thought to serve as the Ca2+ sensor in the release of neurotransmitter. However, functional studies on the calyx of Held synapse ... revealed that the rapid release of neurotransmitter requires only approximately micromolar šCa2+đ, suggesting that Syt I may play a more complex role in determining the high-affinity Ca2+ dependence of exocytosis. Here we tested this hypothesis bystudying pituitary cells, which possess high- and low-affinity Ca2+ -dependent exocytic pathways and express Syt I. Using patch-clamp capacitance measurements to monitor secretion and the acute antisense deletion of Syt I from differentiated cells, we have shown that the rapid and the most Ca2+ sensitive pathway of exocytosis in rat melanotrophs requires Syt I. Furthermore, stimulation of the Ca2+ -dependent exocytosis by cytosol dialysiswith solutions containing 1 micro M šCa2+đ was completely abolished inthe absence of Syt I. Similar results were obtained by the preinjection of antibodies against the CAPS (Ca2+ -dependent activator protein for secretion) protein. These results indicate that synaptotagmin I and CAPS proteins increase the probability of vesicle fusion at low cytosolic šCa2+đ.
    Vir: American journal of physiology. cell physiology. - ISSN 0363-6143 (Letn. 284, 2003, str. C547-54)
    Vrsta gradiva - članek, sestavni del
    Leto - 2003
    Jezik - angleški
    COBISS.SI-ID - 15875545

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