G protein‐independent neuromodulatory action of adenosine on metabotropic glutamate signalling in mouse cerebellar Purkinje cells
G protein‐independent neuromodulatory action of adenosine on metabotropic glutamate signalling in mouse cerebellar Purkinje cells
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DOI：
10.1113/jphysiol.2007.129866
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发表时间：
2007-06
期刊：
影响因子：
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通讯作者：
T. Tabata;D. Kawakami;K. Hashimoto;Hidetoshi Kassai;Takayuki Yoshida;Y. Hashimotodani;B. Fredholm;Y. Sekino;A. Aiba;M. Kano
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文献类型：
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作者：
T. Tabata;D. Kawakami;K. Hashimoto;Hidetoshi Kassai;Takayuki Yoshida;Y. Hashimotodani;B. Fredholm;Y. Sekino;A. Aiba;M. Kano
腺苷受体（AR）是G蛋白偶联受体（GPCR），介导腺苷的神经调节作用，影响中枢神经系统（CNS）中的情感、认知、运动和其他功能。先前的研究表明，在异源系统中AR和代谢型谷氨酸受体（mGluRs）之间形成复合物，并且在几个中枢神经元中AR和mGluRs密切共定位。在这里，我们探讨了Gi/o蛋白偶联的A1亚型AR（A1 R）和小脑浦肯野细胞中天然存在的1型mGluR（mGluR 1）之间密切功能相互作用的可能性。使用穿孔膜片钳技术，我们发现A1 R的合成和内源性激动剂均诱导mGluR 1耦合内向电流的持续抑制。A1 R激动剂也抑制mGluR 1偶联的细胞内Ca 2+动员（通过荧光测定法监测）。A1 R确实介导了这种抑郁，因为A1 R的基因缺失消除了它。令人惊讶的是，A1 R激动剂诱导的抑郁在Gi/o蛋白阻断后仍然存在。这种抑制似乎既不涉及Gi/o和Gs蛋白α亚基下游的cAMP-蛋白激酶A级联反应，也不涉及细胞质Ca 2+，后者被认为是由Gi/o蛋白β-γ亚基复合物调节的。此外，A1 R似乎不影响介导mGluR 1偶联反应的Gq蛋白。这些研究结果表明，A1 R调制mGluR 1信号的主要G蛋白的帮助下。在这方面，这里显示的A1 R介导的mGluR 1信号转导抑制与迄今为止描述的A1 R介导的神经元反应明显不同。这些发现表明腺苷在中枢神经元中的一种新的神经调节作用。
Adenosine receptors (ARs) are G protein‐coupled receptors (GPCRs) mediating the neuromodulatory actions of adenosine that influence emotional, cognitive, motor, and other functions in the central nervous system (CNS). Previous studies show complex formation between ARs and metabotropic glutamate receptors (mGluRs) in heterologous systems and close colocalization of ARs and mGluRs in several central neurons. Here we explored the possibility of intimate functional interplay between Gi/o protein‐coupled A1‐subtype AR (A1R) and type‐1 mGluR (mGluR1) naturally occurring in cerebellar Purkinje cells. Using a perforated‐patch voltage‐clamp technique, we found that both synthetic and endogenous agonists for A1R induced continuous depression of a mGluR1‐coupled inward current. A1R agonists also depressed mGluR1‐coupled intracellular Ca2+ mobilization monitored by fluorometry. A1R indeed mediated this depression because genetic depletion of A1R abolished it. Surprisingly, A1R agonist‐induced depression persisted after blockade of Gi/o protein. The depression appeared to involve neither the cAMP‐protein kinase A cascade downstream of the alpha subunits of Gi/o and Gs proteins, nor cytoplasmic Ca2+ that is suggested to be regulated by the beta‐gamma subunit complex of Gi/o protein. Moreover, A1R did not appear to affect Gq protein which mediates the mGluR1‐coupled responses. These findings suggest that A1R modulates mGluR1 signalling without the aid of the major G proteins. In this respect, the A1R‐mediated depression of mGluR1 signalling shown here is clearly distinguished from the A1R‐mediated neuronal responses described so far. These findings demonstrate a novel neuromodulatory action of adenosine in central neurons.