cGMP and Photoreceptor Function

磷酸二酯酶（PDE）对环鸟苷酸（cGMP）水平的调节是视网膜感光细胞视觉转导途径的核心。 虽然导致PDE激活的初始事件已被广泛研究，但我们对在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结构域中的突变可导致人的色素性视网膜炎和先天性静止性夜盲症。 此外，PDE的抑制性γ亚基的破坏导致动物模型中的视网膜变性。这项研究的总体目标是确定PDE全酶内的调节机制，以及了解其他PDE相互作用蛋白如何调节视觉转导过程中PDE激活的程度和寿命。本研究的具体目的是：（1）明确PDE在激活和失活过程中的不同构象状态，并阐明GAF调节结构域和抑制性γ亚基在这些变构转换中的作用。(2)识别和表征已知的（例如，δ，GARP2）和与PDE形成信号复合物的新蛋白质，并确定它们对光感受器恢复和适应的调节意义。由于PDE活性的精确调节对于光感受器中的信号转导和代谢至关重要，PDE结构、功能或调节的任何缺陷都可能产生严重后果，包括视力损害、视网膜变性和失明。增加对PDE调节的理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变性。

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.