Central Regulation of the Peripheral Visual System

描述（由申请人提供）：每天，我们视网膜中的光敏细胞，我们的光感受器，脱落和更新一部分光敏膜。然而，这个过程发生的原因尚不完全清楚；到目前为止，它在所有被研究的动物中都是普遍存在的。它对正常的视觉功能至关重要。事实上，视网膜变性发生在无法脱落光敏膜的突变大鼠身上。在大多数动物中，光敏膜的脱落是由生物钟（昼夜节律）调节的，并由生物钟和/或光触发。然而，对于生物钟和光如何相互作用来触发和调节光敏膜的日常脱落和更新，人们知之甚少。马蹄蟹（鲎）的侧眼长期以来一直是研究光敏膜脱落的重要系统。Limulus提供了一个相对独特的优势，到目前为止，没有证据表明眼睛里有生物钟；相反，昼夜节律是由大脑的中央时钟沿着从大脑到眼睛的视神经的神经纤维传递给眼睛的。因此，在这个系统中，光和昼夜节律对光感受器结构和功能的影响可以很容易地通过切断视神经来解耦。在目前资助的提案（EY13196-01）中，开发了光和生物钟在调节每日瞬态光敏膜脱落中的相互作用模型并进行了药理学测试。这个竞争性的延续应用程序建议通过以下两个具体目标继续评估模型。

DESCRIPTION (provided by applicant): Everyday, the light-sensitive cells in our retinas, our photoreceptors, shed and renew a portion of their light-sensitive membrane. Why this process occurs is not completely understood, however; it is ubiquitous to all animals studied to date. It is essential for proper visual function. In fact, retinal degeneration occurs in mutant rats unable to shed their photosensitive membrane. In most animals, shedding of the photosensitive membrane is regulated by a biological clock (circadian rhythm) and triggered by that clock and/or by light. Relatively little is known, however, about how the biological clock and light interact to trigger and regulate daily shedding and renewal of photosensitive membrane. The lateral eye of the horseshoe crab (Limulus) has long served as an important system for the study of light-sensitive membrane shedding. Limulus provides the relatively unique advantage that, to date, there is no evidence of a biological clock in the eye; instead, circadian rhythms are communicated to the eye from a central clock in the brain along nerve fibers that run from the brain to the eye in the optic nerve. As a result, the effects of light and circadian rhythms on photoreceptor structure and function can be decoupled easily in this system by severing the optic nerve. In the currently funded proposal (EY13196-01), a model for the interaction of light and the biological clock in the regulation of daily transient photosensitive membrane shedding was developed and tested pharmacologically. This competing continuation application proposes to continue to evaluate the model through the following two specific aims. 1. Investigate whether protein synthesis is stimulated by long-term cAMP-dependent protein kinase activation during efferent priming of Limulus photoreceptors for transient rhabdom shedding. Protein synthesis inhibition, immunohistochemistry/immunoblotting (for CREB activity), and two-dimensional gel electrophoresis will be used to determine whether circadian priming of the lateral eye for transient shedding requires the synthesis of a new protein(s). If protein synthesis is required for the brain to prime the eye for transient shedding, the novel protein (or peptides from that protein) will be microsequenced (outsourced) for putative identification. 2. Identify the target substrate(s) for protein kinase C in the signaling cascade that triggers transient rhabdom shedding in response to light following circadian efferent priming. Immunohistochemical assays for serine and threonine phosphorylation will be used in conjunction with pharmacological activators and inhibitors of protein kinase C (PKC) and cAMP-dependent protein kinase to isolate the PKC substrate(s) that initiate transient shedding.