Identification and Characterization of a G Protein-binding Cluster in α7 Nicotinic Acetylcholine Receptors
Identification and Characterization of a G Protein-binding Cluster in α7 Nicotinic Acetylcholine Receptors
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DOI：
10.1074/jbc.m115.647040
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发表时间：
2015-08-14
影响因子：
4.8
通讯作者：
Kabbani, Nadine
中科院分区：
文献类型：
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作者：
King, Justin R.;Nordman, Jacob C.;Kabbani, Nadine
α 7烟碱乙酰胆碱受体（nAChR）在突触传递和炎症中起重要作用。在对配体的反应中，该受体通道打开以将阳离子传导到细胞中，但迅速脱敏。在最近的研究中，我们表明α 7 nAChR结合信号蛋白，如异源三聚体GTP结合蛋白（G蛋白）。在这里，我们证明了α 7 nAChR与G蛋白的直接偶联能够实现下游钙信号传导反应，该反应可以持续超过通道激活的预期时间过程。这一过程依赖于受体M3-M4环中的G蛋白结合簇（GPBC）。α 7 nAChR（α 7（345- 348 A））中GPBC的突变消除了与G α（q）以及G β γ的相互作用，同时对受体合成、细胞表面运输或α-银环蛇毒素结合没有影响。然而，α 7（345- 348 A）的表达确实显著减弱了α 7 nAChR诱导的G α（q）钙信号传导反应，如在α 7选择性激动剂胆碱存在下PLC-β活化和IP 3R介导的钙储存释放的减少所证明的。总之，这些数据为nAChRs中存在GPBC以促进细胞内信号传导提供了新的证据。
alpha 7 nicotinic acetylcholine receptors (nAChRs) play an important role in synaptic transmission and inflammation. In response to ligands, this receptor channel opens to conduct cations into the cell but desensitizes rapidly. In recent studies we show that alpha 7 nAChRs bind signaling proteins such as heterotrimeric GTP-binding proteins (G proteins). Here, we demonstrate that direct coupling of alpha 7 nAChRs to G proteins enables a downstream calcium signaling response that can persist beyond the expected time course of channel activation. This process depends on a G protein-binding cluster (GPBC) in the M3-M4 loop of the receptor. A mutation of the GPBC in the alpha 7 nAChR (alpha 7(345-348A)) abolishes interaction with G alpha(q) as well as G beta gamma while having no effect on receptor synthesis, cell-surface trafficking, or alpha-bungarotoxin binding. Expression of alpha 7(345-348A), however, did significantly attenuate the alpha 7 nAChR-induced G alpha(q) calcium signaling response as evidenced by a decrease in PLC-beta activation and IP3R-mediated calcium store release in the presence of the alpha 7 selective agonist choline. Taken together, the data provides new evidence for the existence of a GPBC in nAChRs serving to promote intracellular signaling.