AMPA型离子型谷氨酸受体(AMPAR)是各种神经过程的核心,包括记忆和学习。它们组装成GluA1,GluA2,GluA3和GluA4亚基的同源或异源四聚体,每个由N端结构域(NTD)组成,配体结合域,跨膜结构域,和C末端结构域。虽然AMPAR门控主要由配体结合结构域层中的重新配置控制,我们的研究重点是NTD,这也影响了门控,然而,潜在的机制仍然是神秘的。在这次调查中,我们采用分子动力学模拟来评估GluA1,GluA2和NTD突变体GluA2-H229N和GluA1-N222H中的NTD界面强度。我们的发现表明,GluA1的NTD界面明显弱于GluA2。GluA2的NTD界面可以通过NTD二聚体-二聚体界面中的单点突变而减弱,即H229N,这使得GluA2更像GluA1。电生理学记录表明,该突变也导致从脱敏恢复较慢。此外,我们观察到,降低pH会诱导更多的张开NTD状态,并增强GluA2的脱敏作用。我们假设H229是造成这种pH敏感性的原因;然而,GluA2-H229N也受pH的影响,这意味着H229不是唯一负责任的,质子在AMPAR的多个域中发挥作用。总之,我们的工作揭示了NTD界面强度和AMPAR脱敏之间的变构联系。
AMPA-type ionotropic glutamate receptors (AMPARs) are central to various neurological processes, including memory and learning. They assemble as homo- or heterotetramers of
GluA1, GluA2, GluA3, and GluA4 subunits, each consisting of an N-terminal domain (NTD), a ligand-binding domain, a transmembrane domain, and a C-terminal domain. While AMPAR gating is primarily controlled by reconfiguration in the ligand-binding domain layer, our study focuses on the NTDs, which also influence gating, yet the underlying mechanism remains enigmatic. In this investigation, we employ molecular dynamics simulations to evaluate the NTD interface strength in
GluA1, GluA2, and NTD mutants GluA2-H229N and
GluA1-N222H. Our findings reveal that
GluA1 has a significantly weaker NTD interface than GluA2. The NTD interface of GluA2 can be weakened by a single point mutation in the NTD dimer-of-dimer interface, namely H229N, which renders GluA2 more
GluA1-like. Electrophysiology recordings demonstrate that this mutation also leads to slower recovery from desensitization. Moreover, we observe that lowering the pH induces more splayed NTD states and enhances desensitization in GluA2. We hypothesized that H229 was responsible for this pH sensitivity; however, GluA2-H229N was also affected by pH, meaning that H229 is not solely responsible and that protons exert their effect across multiple domains of the AMPAR. In summary, our work unveils an allosteric connection between the NTD interface strength and AMPAR desensitization.