Caccin Paola, Scorzeto Michele, Damiano Nunzio, Marin Oriano, Megighian Aram, Montecucco Cesare
Dipartimento di Scienze Biomediche, Università di Padova, Via Ugo Bassi 58/B, 35131 Padova, Italy.
CRIBI Biotechnology Centre, Via Ugo Bassi 58/B, 35131 Padova, Italy.
FEBS Open Bio. 2015 Apr 30;5:388-96. doi: 10.1016/j.fob.2015.04.013. eCollection 2015.
Synaptotagmin is a synaptic vesicle membrane protein which changes conformation upon Ca(2+) binding and triggers the fast neuroexocytosis that takes place at synapses. We have synthesized a series of peptides corresponding to the sequence of the cytosolic juxtamembrane domain of synaptotagmin, which is highly conserved among different isoforms and animal species, with or without either a hexyl hydrophobic chain or the hexyl group plus a fluorescein moiety. We show that these peptides inhibit neurotransmitter release, that they localize on the presynaptic membrane of the motor axon terminal at the neuromuscular junction and that they bind monophosphoinositides in a Ca(2+)-independent manner. Based on these findings, we propose that the juxtamembrane cytosolic domain of synaptotagmin binds the cytosolic layer of the presynaptic membrane at rest. This binding brings synaptic vesicles and plasma membrane in a very close apposition, favouring the formation of hemifusion intermediates that enable rapid vesicle fusion.
突触结合蛋白是一种突触小泡膜蛋白，它在结合Ca(2+)后会改变构象，并触发在突触处发生的快速神经递质释放。我们合成了一系列与突触结合蛋白胞质近膜结构域序列相对应的肽，该结构域在不同的亚型和动物物种中高度保守，带有或不带有己基疏水链或己基加荧光素部分。我们发现这些肽抑制神经递质释放，它们定位于神经肌肉接头处运动轴突终末的突触前膜，并且它们以不依赖Ca(2+)的方式结合单磷酸肌醇。基于这些发现，我们提出突触结合蛋白的近膜胞质结构域在静息时与突触前膜的胞质层结合。这种结合使突触小泡和质膜非常紧密地并列，有利于形成半融合中间体，从而实现快速的小泡融合。
