Regulation of transport mechanisms in lens cells

描述(申请人提供)：我们假设晶状体上皮能够感知并响应整个细胞结构的变化，并相应地调整Na，K-ATPase的活性。为了正常发挥功能，维持离子平衡，建立膜电位和调节水分含量，所有细胞都需要Na，K-ATPase提供的活性Na-K转运。然而，晶状体几乎完全由纤维细胞组成，这些细胞几乎没有或很少有Na，K-ATPase活性。晶状体离子和水的动态平衡是由上皮单分子层外围相对较少的细胞以某种方式设法使Na，K-ATPase活性与整个细胞结构的需要相匹配而实现的。我们在上一个资助期的研究表明，TRPV4通道能够触发Na，K-ATPase活性的增加，有效地使Na，K-ATPase机械敏感。这使上皮细胞能够检测到晶状体远端区域离子失衡引起的肿胀并做出反应。目标1是对传感器机理的研究。我们建议用实验来解释机械敏感的TRPV4离子通道是如何检测肿胀并导致上皮细胞释放嘌呤能激动剂ATP的。ATP引起一种刺激Na，K-ATPase的反应。目标2是对反应机制的研究。我们建议用实验来解释受体、蛋白激酶和调节蛋白Fxyd6如何相互作用来增加Na，K-ATPase的活性。透镜的透明度取决于离子和水的动态平衡。这些透镜研究将有助于解释动态平衡是如何实现的。对人类福祉的意义在于，当内环境不稳定时，就会发生白内障。

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.