Light response of retinal ON bipolar cells requires a specific splice variant of Gαo
Light response of retinal ON bipolar cells requires a specific splice variant of Gαo
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DOI：
10.1523/jneurosci.22-12-04878.2002
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发表时间：
2002-06-15
影响因子：
5.3
通讯作者：
Vardi, N
中科院分区：
文献类型：
--
作者：
Dhingra, A;Jiang, MS;Vardi, N
释放到视网膜 ON 双极神经元上的谷氨酸与代谢型受体结合，激活异三聚体 G 蛋白 (Go)，最终关闭非特异性阳离子通道。信号传导需要α亚基(Galpha(o))，但其效应子未知。由于 Galpha(o) 被转录成两个剪接变体（alpha(o1) 和 alpha(o2)），其关键 GTPase 结构域不同，因此阐明该途径的下一步是确定哪个剪接变体携带信号。在这里，我们通过逆转录 PCR 和蛋白质印迹显示视网膜表达两种剪接变体。此外，对一种或另一种剪接变体缺陷的小鼠视网膜进行的原位杂交和免疫染色表明，α(o1) 和 α(o2) 均由 ON 双极细胞表达，但 α(o1) 的含量要丰富得多。最后，对缺乏一种剪接变体或另一种剪接变体的小鼠进行的视网膜电图显示，正b波（ON双极细胞对视杆细胞和视锥细胞输入的反应）需要α（o1）而不是α（o2）。因此，ON双极细胞的光响应可能是由其强表达的剪接变体Galpha(o1)携带的。
Glutamate released onto retinal ON bipolar neurons binds to a metabotropic receptor to activate a heterotrimeric G-protein (Go) that ultimately closes a nonspecific cation channel. Signaling requires the alpha subunit (Galpha(o)), but its effector is unknown. Because Galpha(o) is transcribed into two splice variants (alpha(o1) and alpha(o2)) that differ in the key GTPase domain, the next step in elucidating this pathway was to determine which splice variant carries the signal. Here we show by reverse transcription-PCR and Western blots that retina expresses both splice variants. Furthermore, in situ hybridization and immunostaining on mouse retina deficient in one splice variant or the other show that both alpha(o1) and alpha(o2) are expressed by ON bipolar cells but that alpha(o1) is much more abundant. Finally, electroretinography performed on mice deficient for one splice variant or the other shows that the positive b-wave (response of ON bipolar cells to rod and cone input) requires alpha(o1) but not alpha(o2). Thus, the light response of the ON bipolar cell is probably carried by its strongly expressed splice variant, Galpha(o1).