Shank3 Binds to and Stabilizes the Active Form of Rap1 and HRas GTPases via Its NTD-ANK Tandem with Distinct Mechanisms
Shank3 Binds to and Stabilizes the Active Form of Rap1 and HRas GTPases via Its NTD-ANK Tandem with Distinct Mechanisms
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DOI：
10.1016/j.str.2019.11.018
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发表时间：
2020-03-03
期刊：
影响因子：
5.7
通讯作者：
Zhang, Mingjie
中科院分区：
文献类型：
--
作者：
Cai, Qixu;Hosokawa, Tomohisa;Zhang, Mingjie
Shank1/2/3是兴奋性突触中的主要骨架蛋白，在精神障碍患者中经常发生突变。虽然已知Shank N-末端结构域和Ankyrin重复结构域串联(NTD-ANK)与RAS和Rap1结合，但这些结合在突触中的分子机制和功能意义尚不清楚。在这里，我们证明了Shank3 NTD-ANK特异性地结合到HRAs和Rap1的鸟苷三磷酸(GTP)结合形式。除了由RAS结合结构域介导的两种GTP酶共有的典型结合位点外，Shank3还包含一个由NTD和ANK共同形成的非传统Rap1结合位点。Shank3与GTP负载的Rap1的结合减缓了SynGAP对其GTP的水解。我们进一步证明，Shank3和HRAS/Rap1在兴奋性突触上的相互作用是通过突触激活而促进的。因此，Shank3可能通过直接结合和稳定GTP结合形式的酶来调节RAS家族蛋白的信号。
Shank1/2/3, major scaffold proteins in excitatory synapses, are frequently mutated in patients with psychiatric disorders. Although the Shank N-terminal domain and ankyrin repeats domain tandem (NTD-ANK) is known to bind to Ras and Rap1, the molecular mechanism underlying and functional significance of the bindings in synapses are unknown. Here, we demonstrate that Shank3 NTD-ANK specifically binds to the guanosine triphosphate (GTP)-bound form of HRas and Rap1. In addition to the canonical site mediated by the Ras-association domain and common to both GTPases, Shank3 contains an unconventional Rap1 binding site formed by NTD and ANK together. Binding of Shank3 to the GTP-loaded Rap1 slows down its GTP hydrolysis by SynGAP. We further show that the interactions between Shank3 and HRas/Rap1 at excitatory synapses are promoted by synaptic activation. Thus, Shank3 may be able to modulate signaling of the Ras family proteins via directly binding to and stabilizing the GTP-bound form of the enzymes.