EPITHELIAL P2X PURINERGIC RECEPTOR CHANNELS

囊性纤维化（CF）气道上皮具有许多缺陷，包括氯（Cl-）和液体转运的损失、粘膜纤毛清除的损失、顶端自分泌和旁分泌ATP信号传导的损失以及Na+转运的增加。 外源性核苷酸激动剂恢复细胞外APT信号传导并刺激囊性纤维化（CF）气道上皮细胞中的Cl-和液体转运。 因此，已提出雾化核苷酸激动剂疗法来治疗CF气道。 为了了解核苷酸激动剂如何调节CF和非CF气道上皮功能，需要对质膜嘌呤能受体有全面的了解。 我们实验室的初步数据显示，一类新的嘌呤能受体，P2 X受体通道（P2 XRs），由气道上皮细胞表达。 P2 XR表达和功能的细胞和分子生理学尚未在上皮中研究。 P2 XR是配体门控通道，其在细胞外结构域中结合ATP并在质膜中形成内在钙（Ca 2+）可渗透的非选择性阳离子通道。ATP门控P2 XRs可能通过介导细胞外钙库的钙内流或触发钙依赖性蛋白激酶信号传导来影响上皮细胞功能。 因此，我们将测试的中心假设：P2 X嘌呤受体通道表达的气道上皮细胞和ATP门控的Ca 2+内流通道的功能，以调节Cl-，Na+，和液体运输通过气道上皮细胞。 因为我们的初步数据表明，在CF和非CF气道上皮中，P2 XR表达相似，并且因为P2 XR激动剂在体外和体内刺激CF和非CF小鼠和人气道上皮的Cl-分泌，P2 XR的激活可以提供一种新的途径，通过该途径恢复正常的Cl-、Na+和流体通过CF气道的转运，并改善CF肺的粘膜纤毛清除。

Cystic fibrosis (CF) airway epithelia have many defects including a loss in chloride (Cl-) and fluid transport, a loss in mucociliary clearance, a loss in apical autocrine and paracrine ATP signaling, and a gain in Na+ transport. Exogenous nucleotide agonists restore extracellular APT signaling and stimulate Cl- and fluid transport in cystic fibrosis (CF) airway epithelia. As such, aerosolized nucleotide agonist therapy has been proposed to treat CF airways. To understand how nucleotide agonists regulate CF and non-CF airway epithelial function, a complete understanding of plasma membrane purinergic receptors is required. Preliminary data from our laboratory reveal that a new class of purinergic receptor, the P2X receptor channels (P2XRs), are expressed by airway epithelia. The cellular and molecular physiology of P2XR expression and function has not been studied in epithelia. P2XRs are ligand-gated channels that bind ATP in an extracellular domain and form intrinsic calcium (Ca2+)- permeable, non-selective cation channels in the plasma membrane. ATP-gated P2XRs may affect epithelial cell function by mediating influx of Ca2+ from extracellular stores or by triggering Ca2+- dependent protein kinase signaling. Therefore, we will test the central hypothesis that: P2X purinergic receptor channels are expressed by airway epithelia and function as ATP-gated Ca2+ influx channels to regulate Cl-, Na+, and fluid transport across airway epithelia. Because little is known about P2XRs in airway epithelia, we anticipate that new and exciting results will be found. Because our preliminary data demonstrate that P2XR expression is similar in CF versus non-CF airway epithelia and beacuase P2XR agonists stimulate Cl- secretion across both CF and non-CF mouse and human airway epithelium in vitro and in vivo, activation of P2XRs may provide a novel approach with which to restore normal Cl-, Na+, and fluid transport across CF airways and improve mucociliary clearance from CF lungs.