Distinct domains of complexin I differentially regulate neurotransmitter release |
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Authors: | Xue Mingshan Reim Kerstin Chen Xiaocheng Chao Hsiao-Tuan Deng Hui Rizo Josep Brose Nils Rosenmund Christian |
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Institution: | Department of Neuroscience, Baylor College of Medicine, Houston, Texas 77030, USA. |
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Abstract: | Complexins constitute a family of four synaptic high-affinity SNARE complex-binding proteins. They positively regulate a late, post-priming step in Ca2+-triggered synchronous neurotransmitter release, but the underlying molecular mechanisms are unclear. We show here that SNARE complex binding of complexin I (CplxI) via its central alpha-helix is necessary but, unexpectedly, not sufficient for its key function in promoting neurotransmitter release. An accessory alpha-helix on the N-terminal side of the SNARE complex-binding region has an inhibitory effect on fast synaptic exocytosis, whereas sequences N-terminally adjacent to this helix facilitate Ca2+-triggered release even in the absence of the Ca2+ sensor synaptotagmin-1. Our results indicate that distinct functional domains of CplxI differentially regulate synaptic exocytosis and that, through the interplay between these domains, CplxI carries out a crucial role in fine-tuning Ca2+-triggered fast neurotransmitter release. |
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