Regulation of retinal rod transducin

摘要。 感觉信号传导依赖于由异源三聚体G- 蛋白质，其传递来自跨膜G- 蛋白偶联受体（GPCR）的第二信使系统的酶。 这些级联中的功能缺陷导致各种神经退行性疾病， 包括视网膜病变此外，GPCR是最重要的目标之一， 治疗性干预，占市场上药物的近50%。尽管 G蛋白普遍分子机制的研究进展 活化，G蛋白β-γ亚基复合物的生物学作用，及其 在从GPCR到G蛋白的信号传递过程中的确切作用仍然令人惊讶 晦涩难懂。由于在一个典型的细胞中存在多种β和γ亚基同种型， 细胞和冗余的G蛋白介导的途径许多基本的 β-γ复合体生物学的问题在 生理条件。因此，这种蛋白质复合物如何发挥功能的主要方面 仍然未经证实。这一提议建立在我们坚实的基础之上， 发现β-γ复合体赋予视网膜视杆细胞感光能力 放大视觉信号并决定这些感觉神经元的整体敏感度 光，以及调节信号失活和光适应。我们的研究 挑战了目前相当狭隘的β-γ复合物作为辅助的观点， G蛋白的亚基，并旨在鉴定该蛋白复合物的生物学作用， 它在从GPCR到G蛋白的信号传递过程中的确切作用，特别是在 该反应的关键激活步骤-G蛋白α上的核苷酸交换 亚单位通过使用生物化学、生理学和分子生物物理学的组合， 方法，并通过采用几个独特的鼠标线，我们希望解开 β-γ复合物在对以下方面至关重要的潜在机制中的作用 视网膜光感受器中的GPCR信号传导和调节。就像β-γ复合体 作为药物设计和治疗干预的新靶点，该提案将 从而更好地了解新疗法如何影响GPCR信号传导。

ABSTRACT. Sensory signaling relies on the prototypical pathway mediated by the heterotrimeric G- proteins, which relays the incoming extracellular signals from the transmembrane G- protein-coupled receptors (GPCRs) to the enzymes of the second messenger system. Functional defects in these cascades lead to a variety of neurodegenerative disorders, which include retinopathies. In addition, GPCRs are among the most important targets of therapeutic intervention, which account for nearly 50% of drugs on the market. Despite recent progress in understanding the universal molecular mechanism of G-protein activation, the biological role of the G-protein beta-gamma subunit complex, and its exact role during signal transfer from a GPCR to a G-protein remain surprisingly obscure. Due to the existence of multiple beta and gamma subunit isoforms in a typical cell and the redundancy of the G-protein-mediated pathways many fundamental questions of beta-gamma complex biology have been very difficult to address under the physiological conditions. Thus, major aspects of how this protein complex functions remain unproven. This proposal builds on our strong groundwork that led to the discovery that the beta-gamma complex confers the ability of retinal rod photoreceptors to amplify visual signals and determines the overall sensitivity of these sensory neurons to light, as well as modulates signal inactivation and light adaptation. Our studies challenge a rather narrow current view of the beta-gamma complex as an auxiliary subunit of the G-protein and aim at identifying the biological role of this protein complex, its exact role during signal transfer from a GPCR to a G-protein, especially during the key activating step of this reaction – nucleotide exchange on the G-protein alpha subunit. By using a combination of biochemical, physiological and molecular biophysical approaches, and by employing several unique mouse lines, we expect to unravel the contribution of the beta-gamma complex in the underlying mechanisms that are critical to GPCR signaling and regulation in retinal photoreceptors. As beta-gamma complex has emerged as a new target of drug design and therapeutic intervention, this proposal will lead to better understanding of how new therapies may affect GPCR signaling.