Regulation of transport mechanisms in lens cells

描述（由申请人提供）：我们假设晶状体上皮能够感知和响应整个细胞结构的变化，并相应地调节Na， k - atp酶的活性。为了维持正常功能、维持离子稳态、建立膜电位和调节水分含量，所有细胞都需要Na， k - atp酶提供的Na- k转运。然而，晶状体几乎完全由纤维细胞组成，这些纤维细胞很少或没有Na， k - atp酶活性。晶状体离子和水分的平衡是通过上皮单层周围相对较少的细胞来实现的，这些细胞以某种方式使Na， k - atp酶活性与整个细胞结构的需要相匹配。我们在上一个资助期的研究表明，TRPV4通道能够触发Na， k - atp酶活性的增加，有效地使Na， k - atp酶具有机械敏感性。这使得上皮细胞能够检测并对晶状体远处区域离子不平衡引起的肿胀做出反应。目的1是对传感器机制的研究。我们提出实验来解释机械敏感的TRPV4离子通道如何检测肿胀并导致上皮释放嘌呤能激动剂ATP。ATP引起刺激Na - k -ATP酶的反应。目的2是对反应机制的研究。我们提出实验来解释受体，蛋白激酶和调节蛋白Fxyd6如何相互作用以增加Na，K- atp酶活性。透镜的透明度取决于离子和水的平衡。这些透镜研究将有助于解释体内平衡是如何实现的。当体内平衡失败时，白内障的发生对人类的福祉具有重要意义。

DESCRIPTION (provided by applicant): We hypothesize that the lens epithelium is able to sense and respond to changes in the entire cellular structure and adjust Na,K-ATPase activity accordingly. To function normally, maintain ion homeostasis, establish a membrane potential and regulate water content, all cells require active Na-K transport provided by Na,K-ATPase. The lens, however, is made up almost entirely of fiber cells that have little or no Na,K-ATPase activity. Lens ion and water homeostasis is made possible by a relatively few cells at the periphery of epithelium monolayer that somehow manage to match Na,K-ATPase activity to the needs of the entire cellular structure. Our studies in the last funding period indicate TRPV4 channels are able to trigger an increase of Na,K-ATPase activity, effectively making the Na,K-ATPase mechanosensitive. This enables the epithelium to detect and respond to swelling caused by ion imbalance in distant regions of the lens. Aim 1 is a study of the sensor mechanism. We propose experiments to explain how mechanosensitive TRPV4 ion channels detect swelling and cause the epithelium to emit a purinergic agonist, ATP. The ATP causes a response that stimulates Na,K-ATPase. Aim 2 is a study of the response mechanism. We propose experiments to explain how receptors, protein kinases and the regulatory protein Fxyd6 interact to increase Na,K- ATPase activity. Lens transparency depends on ion and water homeostasis. These lens studies will help explain how homeostasis is achieved. The significance to human well- being is the occurrence of cataract when homeostasis fails.