Novel Target for Ciliary Epithelium Transport Regulation

描述（由申请人提供）：一旦检测到高眼压，预防和治疗青光眼的一种方法是通过降低眼内液的分泌速度来降低净眼压。然而，目前的药物治疗有一些缺点，最好是有一个在控制眼内液体分泌方面具有更独特作用的靶点。这项试点研究拨款申请旨在测试一个新的假设，即磷酸化蛋白（phospholemann），一种被多种蛋白激酶磷酸化的小膜蛋白，可能是这样一个目标。我们发现，在眼睛的前段，磷脂蛋白在睫状上皮的非色素层特异表达，并与Na，K-A TPase共定位，后者是一种主动转运酶，为液体分泌提供动力。在脑室的类似的分泌器官，脉络膜丛中，磷脂蛋白与Na， k - atp酶复合物有关。Phospholemman是另外两种蛋白的同源物，这两种蛋白已被证明与肾脏中的Na， k - atp酶相关联并调节。我们将验证这样的假设，即磷脂蛋白与睫状上皮内的Na， k - atp酶结合，并被参与眼内液分泌调节的蛋白酶磷酸化。我们将用两种不同的突变小鼠品系来评估磷脂蛋白在青光眼中的作用。在一种菌株DBA/2J中，青光眼的进行性症状是由于流出通道阻塞而发展的，类似于人类青光眼。我们将评估磷脂蛋白和Na， k - atp酶本身的代偿性和病理变化。另一种菌株是磷蛋白的敲除。我们将调查睫状体、视网膜和视神经，寻找眼内液体分泌调节不足造成损伤的证据。磷脂蛋白及其同源物可能是Na， k - atp酶的调节因子的想法是相当新的，作为信号转导的中介，磷脂蛋白可能整合了多种信号通路的激活。如果成功，这项工作有望为理解眼内液分泌的调节和药理控制提供一个新的范例。

DESCRIPTION (provided by applicant): Once high intraocular pressure is detected, one way that glaucoma can be prevented and treated is by reducing the rate of secretion of intraocular fluid in an effort to reduce net intraocular pressure. Current drug therapies have some shortcomings, however, and it would be preferable to have a target that has a more unique role in the control of intraocular fluid secretion. This pilot research grant application proposes to test the new hypothesis that phospholemann, a small membrane protein that is phosphorylated by multiple protein kinases, could be such a target. We show that in the anterior segment of the eye, phospholemann is expressed specifically in the non-pigmented layer of the ciliary epithelium and co-localizes with Na,K-A TPase, the active transport enzyme that provides the driving force for fluid secretion. In the similar secretory organ of the brain ventricles, the choroid plexus, phospholemann is associated in a complex with the Na,K-ATPase. Phospholemman is a homolog of two other proteins that have been shown to associate with and modulate Na,K-ATPase in the kidney. We will test the hypothesis that phospholemann binds to Na,K-ATPase in ciliary epithelium, and that it is phosphorylated by protein inases that are implicated in the regulation of intraocular fluid secretion. Two different strains of mutant mice will be used to evaluate phospholemann's role in glaucoma. In one strain, DBA/2J, progressive symptoms of glaucoma develop because of blockage of the outflow pathway, mimicking human glaucomas. We will assess compensatory and pathological changes in phospholemman and in the Na,K-ATPase itself. The other strain is a knockout of phospholemann. We will investigate the ciliary body, retina, and optic nerve for evidence of damage from a deficiency in the regulation of intraocular fluid secretion. The idea that phospholemann and its homologs may be regulators of Na,K-ATPase is quite new, and as an intermediate of signal transduction, phospholemman may integrate the activation of multiple signaling pathways. If successful the work promises to lead to a new paradigm for understanding the regulation and pharmacological control of intraocular fluid secretion.