The synaptotagmin juxtamembrane domain is involved in neuroexocytosis

Paola Caccin; Michele Scorzeto; Nunzio Damiano; Oriano Marin; Aram Megighian; Cesare Montecucco

doi:10.1016/j.fob.2015.04.013

Fig. 8

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A possible role of the synaptotagmin juxtamembrane segment in synaptic vesicle–plasma membrane interaction and hemifusion. (A) synaptic vesicle (SV) near the presynaptic membrane (PM) before fusion; green segments represent the three polybasic sequences in synaptotagmin, localized in the juxtamembrane segment and in the two C2 domains capable of anionic phospholipid binding; (B) interaction of the juxtamembrane segment of synaptotagmin residing on a hemifused SV with anionic lipids of the cytosolic surface of the PM (preferentially mono-phosphorylated phosphoinositides, orange) could favor the close apposition of the two membranes with hemifusion. AZ: active zone. (C) The rise of calcium (light blue dots) consequent to the opening of calcium channels nearby (not shown) will then cause the C2 domains conformational change allowing their interaction with PIP2 (red) and the complete membrane fusion. (D) Sequence of the three polybasic peptide segment in mouse and human synaptotagmin 1.