Paudyal Nabina, Das Anindita, Carrillo Elisa, Berka Vladimir, Jayaraman Vasanthi
Center for Membrane Biology, Department of Biochemistry and Molecular Biology, University of Texas Health Science Center at Houston, Houston, Texas, USA.
MD Anderson Cancer Center UTHealth Graduate School of Biomedical Sciences, University of Texas Health Science Center at Houston, Houston, Texas, USA.
Proteins. 2025 Jan;93(1):134-144. doi: 10.1002/prot.26565. Epub 2023 Aug 1.
Kainate receptors are a subtype of ionotropic glutamate receptors that form transmembrane channels upon binding glutamate. Here, we have investigated the mechanism of partial agonism in heteromeric GluK2/K5 receptors, where the GluK2 and GluK5 subunits have distinct agonist binding profiles. Using single-molecule Förster resonance energy transfer, we found that at the bi-lobed agonist-binding domain, the partial agonist AMPA-bound receptor occupied intermediate cleft closure conformational states at the GluK2 cleft, compared to the more open cleft conformations in apo form and more closed cleft conformations in the full agonist glutamate-bound form. In contrast, there is no significant difference in cleft closure states at the GluK5 agonist-binding domain between the partial agonist AMPA- and full agonist glutamate-bound states. Additionally, unlike the glutamate-bound state, the dimer interface at the agonist-binding domain is not decoupled in the AMPA-bound state. Our findings suggest that partial agonism observed with AMPA binding is mediated primarily due to differences in the GluK2 subunit, highlighting the distinct contributions of the subunits towards activation.
海人藻酸受体是离子型谷氨酸受体的一种亚型，在结合谷氨酸后形成跨膜通道。在此，我们研究了异源三聚体GluK2/K5受体中部分激动作用的机制，其中GluK2和GluK5亚基具有不同的激动剂结合谱。使用单分子Förster共振能量转移技术，我们发现，在双叶激动剂结合结构域，与空载形式中更开放的裂隙构象以及完全激动剂谷氨酸结合形式中更闭合的裂隙构象相比，部分激动剂AMPA结合的受体在GluK2裂隙处占据中间的裂隙闭合构象状态。相比之下，在部分激动剂AMPA结合状态和完全激动剂谷氨酸结合状态之间，GluK5激动剂结合结构域的裂隙闭合状态没有显著差异。此外，与谷氨酸结合状态不同，在AMPA结合状态下激动剂结合结构域的二聚体界面没有解耦。我们的研究结果表明，AMPA结合时观察到的部分激动作用主要是由GluK2亚基的差异介导的，突出了各亚基对激活的不同贡献。
