Neuroscience Discovery Research, Eli Lilly and Company, Indianapolis, Indiana 46285, USA.
J Neurosci. 2011 May 4;31(18):6928-38. doi: 10.1523/JNEUROSCI.6271-10.2011.
Neuronal AMPA receptor complexes comprise a tetramer of GluA pore-forming subunits as well as accessory components, including transmembrane AMPA receptor regulatory proteins (TARPs) and cornichon-2/3 (CNIH-2/3). The mechanisms that control AMPA receptor complex assembly remain unclear. AMPA receptor responses in neurons differ from those in cell lines transfected with GluA plus TARPs γ-8 or γ-7, which show unusual resensitization kinetics and non-native AMPA receptor pharmacologies. Using tandem GluA/TARP constructs to constrain stoichiometry, we show here that these peculiar kinetic and pharmacological signatures occur in channels with four TARP subunits per complex. Reducing the number of TARPs per complex produces AMPA receptors with neuron-like kinetics and pharmacologies, suggesting a neuronal mechanism controls GluA/TARP assembly. Importantly, we find that coexpression of CNIH-2 with GluA/TARP complexes reduces TARP stoichiometry within AMPA receptors. In both rat and mouse hippocampal neurons, CNIH-2 also associates with AMPA receptors on the neuronal surface in a γ-8-dependent manner to dictate receptor pharmacology. In the cerebellum, however, CNIH-2 expressed in Purkinje neurons does not reach the neuronal surface. In concordance, stargazer Purkinje neurons, which express CNIH-2 and γ-7, display AMPA receptor kinetics/pharmacologies that can only be recapitulated recombinantly by a low γ-7/GluA stoichiometry. Together, these data suggest that CNIH-2 modulates neuronal AMPA receptor auxiliary subunit assembly by regulating the number of TARPs within an AMPA receptor complex to modulate receptor gating and pharmacology.
神经元 AMPA 受体复合物由 GluA 孔形成亚基的四聚体以及辅助成分组成，包括跨膜 AMPA 受体调节蛋白 (TARPs) 和角蛋白 2/3 (CNIH-2/3)。控制 AMPA 受体复合物组装的机制尚不清楚。神经元中的 AMPA 受体反应与转染了 GluA 加 TARPs γ-8 或 γ-7 的细胞系中的反应不同，后者表现出异常的再敏化动力学和非天然的 AMPA 受体药理学。使用串联 GluA/TARP 构建体来限制化学计量，我们在这里表明，这些特殊的动力学和药理学特征出现在每个复合物具有四个 TARP 亚基的通道中。减少每个复合物的 TARP 数量会产生具有神经元样动力学和药理学的 AMPA 受体，表明神经元机制控制 GluA/TARP 组装。重要的是，我们发现 CNIH-2 与 GluA/TARP 复合物的共表达会降低 AMPA 受体中的 TARP 化学计量。在大鼠和小鼠海马神经元中，CNIH-2 也以 γ-8 依赖性方式与神经元表面的 AMPA 受体结合，从而决定受体的药理学。然而，在小脑，在浦肯野神经元中表达的 CNIH-2 不会到达神经元表面。一致地，表达 CNIH-2 和 γ-7 的 stargazer 浦肯野神经元显示出的 AMPA 受体动力学/药理学只能通过低 γ-7/GluA 化学计量比重组来重现。这些数据表明，CNIH-2 通过调节 AMPA 受体复合物中 TARPs 的数量来调节受体门控和药理学，从而调节神经元 AMPA 受体辅助亚基的组装。
