Alternative splicing of RGS8 gene determines inhibitory function of receptor type-specific Gq signaling
Alternative splicing of RGS8 gene determines inhibitory function of receptor type-specific Gq signaling
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RGS8 基因的选择性剪接决定受体类型特异性 Gq 信号传导的抑制功能
DOI：
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发表时间：
2002
影响因子：
11.1
通讯作者：
Y. Kubo
中科院分区：
文献类型：
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作者：
O. Saitoh;Yoshimichi Murata;M. Odagiri;M. Itoh;H. Itoh;T. Misaka;Y. Kubo
G蛋白信号（RGS）蛋白调控因子调节异三聚体G蛋白信号。RGS8是一种180 aa的脑特异性RGS蛋白。在这里，我们发现了RGS8的一个短同工异构体RGS8S，它是通过选择性剪接产生的。RGS8S cDNA编码的N端为7aa，而不是RGS8的氨基酸1-9和RGS8的10-180。RGS8和RGS8S在转染细胞中的亚细胞分布无显著差异。RGS8S加速了非洲爪蟾卵母细胞中Gi/o介导的G蛋白内纠偏K+通道的开启和关闭，但其效率不如RGS8。接下来，我们研究了RGS8和RGS8S对gq介导的信号传导的影响。RGS8降低了m1毒蕈碱受体或P物质受体激活后的反应幅度，但没有显著抑制m3毒蕈碱受体的信号传导。相反，RGS8S对这两种gq偶联受体的抑制作用要小得多。通过对抑制效果和蛋白表达水平的定量分析，我们证实了抑制效果的差异是由RGS8和RGS8S的质性差异和蛋白表达水平的定量差异引起的。我们也证实了抑制的受体类型特异性不是由受体表达水平的差异引起的。综上所述，我们发现RGS8 N端的9aa以受体类型特异性的方式参与抑制gq偶联信号的功能，并且RGS8S对gq偶联反应的调节功能尤其减弱。
The regulators of G protein signaling (RGS) proteins modulate heterotrimeric G protein signaling. RGS8 is a brain-specific RGS protein of 180 aa. Here we identified a short isoform of RGS8, RGS8S, that arises by alternative splicing. RGS8S cDNA encodes a N terminus of 7 aa instead of amino acids 1–9 of RGS8 and 10–180 of RGS8. The subcellular distribution of RGS8 and RGS8S did not differ significantly in transfected cells. RGS8S accelerated, not as efficiently as RGS8, the turning on and off of Gi/o-mediated modulation of G protein-gated inwardly rectifying K+ channels in Xenopus oocytes. We next examined the effects of RGS8 and RGS8S on Gq-mediated signaling. RGS8 decreased the amplitude of the response upon activation of m1 muscarinic or substance P receptors, but did not remarkably inhibit signaling from m3 muscarinic receptors. In contrast, RGS8S showed much less inhibition of the response of either of these Gq-coupled receptors. By quantitative analysis of the inhibitory effect and the protein expression level, we confirmed that the difference of inhibitory effect is caused by both the qualitative difference between RGS8 and RGS8S and the quantitative difference of the protein expression level. We also confirmed that the receptor-type specificity of inhibition is not caused by the difference of the expression level of the receptors. In summary, we showed that 9 aa in the N terminus of RGS8 contribute to the function to inhibit Gq-coupled signaling in a receptor type-specific manner and that the regulatory function of RGS8S is especially diminished on Gq-coupled responses.