EPITHELIAL P2X PURINERGIC RECEPTOR CHANNELS

囊性纤维化（CF）气道上皮有许多缺陷，包括氯离子（Cl-）和液体运输的丧失，粘膜纤毛清除的丧失，顶端自分泌和旁分泌ATP信号的丧失，以及Na+运输的增加。外源性核苷酸激动剂恢复细胞外APT信号并刺激囊性纤维化（CF）气道上皮中的Cl-和液体运输。因此，已提出雾化核苷酸激动剂治疗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，需要完全了解质膜嘌呤能受体。我们实验室的初步数据显示，一类新的嘌呤能受体P2X受体通道（P2XRs）在气道上皮中表达。P2XR在上皮细胞中的表达和功能的细胞和分子生理学尚未研究。P2XRs是配体门控通道，在细胞外区域结合ATP，并在质膜上形成内在钙（Ca2+）可渗透的非选择性阳离子通道。atp门控的P2XRs可能通过介导细胞外储存的Ca2+内流或触发Ca2+依赖性蛋白激酶信号传导来影响上皮细胞功能。因此，我们将验证中心假设：P2X嘌呤能受体通道在气道上皮中表达，并作为atp门控的Ca2+内流通道发挥功能，调节Cl-、Na+和液体在气道上皮中的运输。由于对气道上皮中的P2XRs知之甚少，我们期待新的令人兴奋的结果将被发现。由于我们的初步数据表明，P2XR在CF和非CF气道上皮中的表达相似，并且由于P2XR激动剂在体外和体内刺激CF和非CF小鼠和人气道上皮中的Cl-分泌，激活P2XR可能提供一种新的方法，可以恢复CF气道中正常的Cl-、Na+和液体运输，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.