Yamamoto Yasunori, Mochida Sumiko, Kurooka Takao, Sakisaka Toshiaki
Division of Membrane Dynamics, Department of Physiology and Cell Biology, Kobe University Graduate School of Medicine, Kobe 650-0017, Japan.
J Biol Chem. 2009 May 1;284(18):12480-90. doi: 10.1074/jbc.M807182200. Epub 2009 Mar 3.
Neurotransmitter release from presynaptic nerve terminals is regulated by SNARE complex-mediated synaptic vesicle fusion. Tomosyn, a negative regulator of neurotransmitter release, which is composed of N-terminal WD40 repeats, a tail domain, and a C-terminal VAMP-like domain, is known to inhibit SNARE complex formation by sequestering target SNAREs (t-SNAREs) upon interaction of its C-terminal VAMP-like domain with t-SNAREs. However, it remains unclear how the inhibitory activity of tomosyn is regulated. Here we show that the tail domain functions as a regulator of the inhibitory activity of tomosyn through intramolecular interactions. The binding of the tail domain to the C-terminal VAMP-like domain interfered with the interaction of the C-terminal VAMP-like domain with t-SNAREs, and thereby repressed the inhibitory activity of tomosyn on the SNARE complex formation. The repressed inhibitory activity of tomosyn was restored by the binding of the tail domain to the N-terminal WD40 repeats. These results indicate that the probable conformational change of tomosyn mediated by the intramolecular interactions of the tail domain controls its inhibitory activity on the SNARE complex formation, leading to a regulated inhibition of neurotransmitter release.
神经递质从突触前神经末梢的释放受SNARE复合体介导的突触小泡融合调控。Tomosyn是神经递质释放的负调控因子，由N端WD40重复序列、一个尾部结构域和一个C端VAMP样结构域组成，已知其C端VAMP样结构域与靶标SNARE（t-SNARE）相互作用时，通过隔离t-SNARE来抑制SNARE复合体的形成。然而，尚不清楚Tomosyn的抑制活性是如何被调控的。在此我们表明，尾部结构域通过分子内相互作用作为Tomosyn抑制活性的调控因子。尾部结构域与C端VAMP样结构域的结合干扰了C端VAMP样结构域与t-SNARE的相互作用，从而抑制了Tomosyn对SNARE复合体形成的抑制活性。尾部结构域与N端WD40重复序列的结合恢复了Tomosyn被抑制的抑制活性。这些结果表明，由尾部结构域的分子内相互作用介导的Tomosyn可能的构象变化控制其对SNARE复合体形成的抑制活性，从而导致对神经递质释放的调控性抑制。
