Jeffrey Brett G, Morgans Catherine W, Puthussery Theresa, Wensel Theodore G, Burke Neal S, Brown R Lane, Duvoisin Robert M
Oregon National Primate Research Center, Oregon Health & Science University, Beaverton, Oregon 97006, USA.
Vis Neurosci. 2010 Mar;27(1-2):9-17. doi: 10.1017/S0952523809990319. Epub 2010 Jan 26.
The rate-limiting step in the recovery of the photoreceptor light response is the hydrolysis of GTP by transducin, a reaction that is accelerated by the RGS9-Gbeta5 complex, and its membrane anchor, R9AP. Similar complexes, including RGS7, RGS11, and Gbeta5, are found in retinal ON-bipolar cell dendrites. Here, we present evidence that R9AP is also expressed in the dendritic tips of ON-bipolar cells. Immunofluorescent staining for R9AP revealed a punctate pattern of labeling in the outer plexiform layer, where it colocalized with mGluR6. In photoreceptors, R9AP is required for proteolytic stability of the entire regulator of G protein signaling complex, and we found that genetic deletion of R9AP also results in a marked reduction in the levels of RGS11 and Gbeta5 in the bipolar cell dendrites; the level of RGS7 was unaffected, suggesting the presence of another interaction partner to stabilize RGS7. To determine the effect of R9AP deletion on the response kinetics of ON-bipolar cells, we compared the electroretinogram (ERG) between wild-type and R9AP-deficient mice. The ERG b-wave, reflecting ON-bipolar cell activity, was delayed and larger in the R9AP-deficient mice. Our data indicate that R9AP is required for stable expression of RGS11-Gbeta5 in ON-bipolar cell dendrites. Furthermore, they suggest that the RGS11-Gbeta5-R9AP complex accelerates the initial ON-bipolar cell response to light.
光感受器光反应恢复过程中的限速步骤是转导素对GTP的水解，RGS9 - Gβ5复合体及其膜锚定蛋白R9AP可加速这一反应。在视网膜ON - 双极细胞树突中也发现了类似的复合体，包括RGS7、RGS11和Gβ5。在此，我们提供证据表明R9AP也在ON - 双极细胞的树突尖端表达。对R9AP的免疫荧光染色显示在外网状层有斑点状标记模式，它与代谢型谷氨酸受体6（mGluR6）共定位。在光感受器中，R9AP是整个G蛋白信号调节复合体蛋白水解稳定性所必需的，并且我们发现R9AP的基因缺失也导致双极细胞树突中RGS11和Gβ5水平显著降低；RGS7的水平未受影响，这表明存在另一个相互作用伙伴来稳定RGS7。为了确定R9AP缺失对ON - 双极细胞反应动力学的影响，我们比较了野生型和R9AP缺陷型小鼠的视网膜电图（ERG）。反映ON - 双极细胞活性的ERG b波在R9AP缺陷型小鼠中延迟且幅度更大。我们的数据表明R9AP是ON - 双极细胞树突中RGS11 - Gβ5稳定表达所必需的。此外，这些数据表明RGS11 - Gβ5 - R9AP复合体加速了ON - 双极细胞对光的初始反应。
