Guanylate cyclase-G, expressed in the Grueneberg ganglion olfactory subsystem, is activated by bicarbonate
Guanylate cyclase-G, expressed in the Grueneberg ganglion olfactory subsystem, is activated by bicarbonate
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DOI：
10.1042/bj20100617
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发表时间：
2010-12-01
影响因子：
4.1
通讯作者：
Yang, Ruey-Bing
中科院分区：
文献类型：
--
作者：
Chao, Ying-Chi;Cheng, Chien-Jui;Yang, Ruey-Bing
鸟苷酸环化酶G（Guanylate cyclase，GC）是最近发现的GC受体家族成员。然而，其在哺乳动物嗅觉系统中的活性和蛋白表达的调控仍不清楚。在本研究中，我们使用GC-G特异性抗体来验证GC-G蛋白在Grueneberg神经节神经元中表达，Grueneberg神经节神经元是一种新认识的嗅觉子系统，共表达其他cGMP信号传导组分，如cGMP调节的PDE 2A（磷酸二酯酶2A）和cGMP门控离子通道CNGA 3（环核苷酸门控阳离子通道α-3）。进一步的分子和生物化学分析表明，异源表达的GC-G蛋白，特别是C-末端环化酶结构域，直接刺激碳酸氢盐在体内细胞cGMP积累测定在人胚肾-293 T细胞和体外GC测定与纯化的重组蛋白含有GC结构域。此外，在NG 108神经元细胞中GC-G的过度表达导致细胞cGMP水平的CO2依赖性增加，这可以通过用乙酰唑胺（一种碳酸酐酶抑制剂）治疗来阻断，这意味着CO2的刺激作用需要其转化为碳酸氢盐。总之，我们的数据证明了GC-G的一种新的CO2/碳酸氢盐依赖性激活机制，并表明GC-G可能参与各种CO2/碳酸氢盐调节的生物过程，如Grueneberg神经节神经元的化学感受功能。
GC (guanylate cyclase)-G is the most recently identified member of the receptor GC family. However, the regulation of its activity and protein expression in the mammalian olfactory system remains unclear. In the present study, we used a GC-G-specific antibody to validate that the GC-G protein is expressed in Grueneberg ganglion neurons, a newly recognized olfactory subsystem co-expressing other cGMP signalling components such as the cGMP-regulated PDE2A (phosphodiesterase 2A) and the cGMP-gated ion channel CNGA3 (cyclic nucleotide-gated cation channel alpha-3). Further molecular and biochemical analyses showed that heterologously expressed GC-G protein, specifically the C-terminal cyclase domain, was directly stimulated by bicarbonate in both in vivo cellular cGMP accumulation assays in human embryonic kidney-293T cells and in vitro GC assays with a purified recombinant protein containing the GC domain. In addition, overexpression of GC-G in NG108 neuronal cells resulted in a CO2-dependent increase in cellular cGMP level that could be blocked by treatment with acetazolamide, an inhibitor of carbonic anhydrases, which implies that the stimulatory effect of CO2 requires its conversion to bicarbonate. Together, our data demonstrate a novel CO2/bicarbonate-dependent activation mechanism for GC-G and suggest that GC-G may be involved in a wide variety of CO2/bicarbonate-regulated biological processes such as the chemosensory function in Grueneberg ganglion neurons.