Department of Neurobiology, Harvard Medical School, Boston, MA 02115, USA.
Department of Neurobiology, Harvard Medical School, Boston, MA 02115, USA.
Neuron. 2022 May 4;110(9):1498-1515.e8. doi: 10.1016/j.neuron.2022.01.026. Epub 2022 Feb 16.
Presynaptic active zones are molecular machines that control neurotransmitter secretion. They form sites for vesicle docking and priming and couple vesicles to Ca entry for release triggering. The complexity of active zone machinery has made it challenging to determine its mechanisms in release. Simultaneous knockout of the active zone proteins RIM and ELKS disrupts active zone assembly, abolishes vesicle docking, and impairs release. We here rebuild docking, priming, and Ca secretion coupling in these mutants without reinstating active zone networks. Re-expression of RIM zinc fingers recruited Munc13 to undocked vesicles and rendered the vesicles release competent. Action potential triggering of release was reconstituted by docking these primed vesicles to Ca channels through attaching RIM zinc fingers to Caβ4-subunits. Our work identifies an 80-kDa β4-Zn protein that bypasses the need for megadalton-sized secretory machines, establishes that fusion competence and docking are mechanistically separable, and defines RIM zinc finger-Munc13 complexes as hubs for active zone function.
突触前活性区是控制神经递质分泌的分子机器。它们形成囊泡 docking 和 priming 的位点，并将囊泡与 Ca 内流偶联，触发释放。活性区机械装置的复杂性使得确定其释放机制具有挑战性。同时敲除活性区蛋白 RIM 和 ELKS 会破坏活性区组装，消除囊泡 docking，并损害释放。我们在这里重建了这些突变体中的 docking、priming 和 Ca 分泌偶联，而没有重新建立活性区网络。重新表达 RIM 锌指招募 Munc13 到未 docking 的囊泡上，并使囊泡具有释放能力。通过将 RIM 锌指附着到 Caβ4-亚基上，将这些 primed 囊泡 dock 到 Ca 通道上，从而重建了动作电位触发的释放。我们的工作确定了一种 80 kDa 的β4-Zn 蛋白，它绕过了需要 megadalton 大小的分泌机器的需求，证明了融合能力和 docking 是机械上可分离的，并将 RIM 锌指-Munc13 复合物定义为活性区功能的枢纽。
