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膜锚定亚基特异性调节光感受器神经元中的 RGS9·Gβ5 GAP 复合物。

Membrane anchoring subunits specify selective regulation of RGS9·Gbeta5 GAP complex in photoreceptor neurons.

机构信息

Department of Pharmacology, University of Minnesota, Minneapolis, Minnesota 55455, USA.

出版信息

J Neurosci. 2010 Oct 13;30(41):13784-93. doi: 10.1523/JNEUROSCI.1191-10.2010.

Abstract

The RGS9·Gβ5 complex is the key regulator of neuronal G-protein signaling and shows remarkable selectivity of subunit composition. In retinal photoreceptors, RGS9·Gβ5 is bound to the membrane anchor R9AP and the complex regulates visual signaling. In the basal ganglia neurons, RGS9·Gβ5 is instead associated with a homologous protein, R7BP, and regulates reward circuit. Switching this selective subunit composition of the complex in rod photoreceptors allowed us to study the molecular underpinning of signaling specificity in diverse G-protein pathways. We have found that both membrane anchoring subunits play a conserved role in regulating protein levels of RGS9·Gβ5 and enhancing the ability of RGS·Gβ5 complexes to stimulate GTPase activity of G proteins. However, notable differences exist in the subcellular targeting of alternatively configured complexes. Unlike R9AP, which relies on passive targeting mechanisms for the delivery to the outer segments of the photoreceptors, R7BP is excluded from this location and is instead specifically targeted to the plasma membrane. R7BP-containing complexes could be rerouted to the outer segments, where they are capable of regulating the phototransduction cascade by the active targeting signals derived from rhodopsin. These findings illustrate the diversity of the G-protein signaling regulation by RGS·Gβ5 complexes achieved by differential recruitment of the membrane anchors.

摘要

RGS9·Gβ5 复合物是神经元 G 蛋白信号转导的关键调节剂,表现出显著的亚基组成选择性。在视网膜光感受器中,RGS9·Gβ5 与膜锚定蛋白 R9AP 结合,该复合物调节视觉信号转导。在基底神经节神经元中,RGS9·Gβ5 则与同源蛋白 R7BP 相关联,调节奖励回路。在杆状光感受器中改变该复合物的选择性亚基组成,使我们能够研究不同 G 蛋白途径中信号转导特异性的分子基础。我们发现,两种膜锚定亚基在调节 RGS9·Gβ5 的蛋白水平和增强 RGS·Gβ5 复合物刺激 G 蛋白 GTPase 活性的能力方面发挥着保守作用。然而,不同构象的复合物在亚细胞定位上存在显著差异。与依赖于被动靶向机制将 R9AP 递送至光感受器外节的机制不同,R7BP 被排除在外,而是被特异性地靶向至质膜。含有 R7BP 的复合物可以被重新定向到外节,在那里它们能够通过源自视蛋白的主动靶向信号调节光转导级联。这些发现说明了 RGS·Gβ5 复合物通过膜锚的差异募集来实现 G 蛋白信号转导调节的多样性。

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