cGMP and Photoreceptor Function

在视网膜光感受器细胞中，磷酸二酯酶(PDE)对环磷酸鸟苷(CGMP)水平的调节是视觉转导通路的中心环节。虽然导致PDE激活的初始事件已被广泛研究，但我们对暗适应状态恢复期间或在光或漂白适应期间调节PDE活性的途径知之甚少。此外，已知PDE催化亚基的催化和调节域的突变可导致人类的视网膜色素变性和先天性静止性夜盲。此外，在动物模型中，PDE抑制伽马亚单位的破坏会导致视网膜退化。这项研究的总体目标是确定存在于PDE全酶中的调节机制，以及了解其他PDE相互作用蛋白如何在视觉转导过程中调节PDE激活的程度和寿命。这一建议的具体目的是：(1)确定PDE在激活和失活过程中的不同构象状态，并阐明调节性GAF结构域和抑制性伽马亚基在这些变构转变中的作用。(2)鉴定和鉴定与PDE形成信号复合体的已知蛋白质(如Delta、GARP2)和新蛋白质，并确定它们对光感受器恢复和适应的调节意义。由于PDE活性的精确调节对光感受器中的信号转导和新陈代谢至关重要，因此PDE结构、功能或调节的任何缺陷都可能导致严重的后果，包括视力损害、视网膜退化和失明。增加对PDE调节的了解将有助于设计有效的治疗方法来干预某些形式的视网膜退化。

Regulation or cyclic GMP (cGMP) levels by phosphodiesterase (PDE) is central to the visual transduction pathway in retinal photoreceptor cells. While the initial events leading to PDE activation have been extensively studied, we know much less about the pathways that regulate PDE activity during the recovery of the dark-adapted state or during light or bleaching adaptation. Furthermore, it is known that mutations in the catalytic and regulatory domains of the PDE catalytic subunits can result in retinitis pigmentosa and congenital stationary night-blindness in humans. Furthermore, disruptions of the inhibitory gamma subunit of PDE lead to retinal degeneration in animal models. The overall objective of the research is to define the regulatory mechanisms residing within the PDE holoenzyme, as well as to understand how other PDE-interacting proteins modulate the extent and lifetime of PDE activation during visual transduction. The specific aims of this p proposal are: (1) To define the distinct conformational states of PDE during its activation and inactivation, and to elucidate the role of the regulatory GAF domains and the inhibitory gamma subunit in these allosteric transitions. (2) To identify and characterize known (e.g., delta, GARP2) and novel proteins that form a signaling complex with PDE, and to determine their regulatory significance for photoreceptor recovery and adaptation. Because precise regulation of PDE activity is critical to signal transduction and metabolism in photoreceptors, any defect in PDE structure, function, or regulation can have serious consequences, including visual impairment, retinal degeneration, and blindness. Increased understanding of the regulation of PDE will aid in designing effective therapies to intervene in certain forms of retinal degeneration.