Claudin-18 and pathologic alveolar epithelial permeability

描述（由申请人提供）：这是一份针对Michael LaFemina（医学博士）的指导临床科学家研究职业发展奖（K 08）的申请，Michael LaFemina是加州大学旧金山弗朗西斯科医学系肺部和重症监护部的讲师。LaFemina博士正在确立自己作为急性肺损伤相关肺泡上皮生物学领域的年轻研究者的地位。具体而言，本申请集中于肺泡上皮屏障破坏在急性肺损伤发病机制中的作用1。尽管需要严格控制肺泡上皮细胞的屏障功能2，但对肺紧密连接的性质知之甚少。紧密连接蛋白是一个跨膜蛋白家族，对于紧密连接的形成是必要的和足够的3。Claudin-18，唯一的 肺特异性紧密连接蛋白4是1型肺细胞中表达最高的紧密连接蛋白5，提示肺特异性功能。初步数据表明：（1）claudin-18缺陷小鼠肺泡白蛋白渗透性增加，在原代肺泡上皮细胞中特异性敲低claudin-18可诱导高渗透性;（2）claudin-18缺失小鼠在出生后发生肺损伤，进行性纤维化，转化生长因子-？(TGF?)活化;和（3）炎症诱导与增加的渗透性相关的密蛋白-18的特异性损失。基于该初步数据，本申请的总体目标是阐明紧密连接蛋白-18的功能并确定该紧密连接蛋白在急性肺损伤发病机制中的作用。目的1将通过研究新型claudin-18缺陷小鼠的肺液体平衡和claudin-18缺陷的原代肺泡上皮细胞的屏障功能来验证claudin-18是一种独特的细胞旁屏障的假设。目的2将确定在claudin-18缺乏的情况下肺损伤的机制，并将调查屏障功能障碍，肺损伤和TGF-？activation.目的3将通过在离体灌注的人肺制剂中的研究来确定claudin-18在急性肺损伤的临床相关模型中的作用。LaFemina博士在此期间的职业发展将围绕这些目标进行组织，并由正式的导师和课程指导。LaFemina博士组建了一个由UCSF高级研究人员组成的多学科团队来指导他：Dean Sheppard，医学博士，医学教授，整合素介导的TGF-β激活专家; James Frank，医学博士，医学副教授，急性肺损伤和紧密连接生物学基本机制专家; Michael Matthay，医学博士，医学和麻醉教授，急性肺损伤基础和临床科学专家研究员。LaFemina博士的研究计划集中在新的蛋白质claudin-18上，加上他的结构化训练计划，将使他能够完成他的任务。 长期目标成为一名独立资助的医生科学家，通过研究肺泡上皮生物学的基本机制来改善患者的健康。肺中空气和血液之间的屏障破坏可导致呼吸衰竭和死亡。紧密连接是调节这种屏障的蛋白质复合物。这项研究将探讨的作用， 紧密连接蛋白claudin-18在肺损伤中的作用，并将确定该蛋白是否是潜在的治疗靶点。

DESCRIPTION (provided by applicant): This is an application for a Mentored Clinical Scientist Research Career Development Award (K08) for Michael LaFemina, MD, an Instructor in the Department of Medicine, Division of Pulmonary and Critical Care, at the University of California, San Francisco. Dr. LaFemina is establishing himself as a young investigator in the field of alveolar epithelial biology relating to acute lung injury. Specifically, this application s focused on the role of alveolar epithelial barrier disruption in the pathogenesis of acute lung injury1. Despite the requirement to strictly control barrier function in the alveolar epithelium2, ittle is known about the nature of tight junctions in the lung. Claudins are a family of transmembrane proteins that are both necessary and sufficient for tight junction formation3. Claudin-18, the only lung-specific tight junction protein4, is the most highly expressed claudin in type 1 pneumocytes5, suggesting a lung-specific function. Preliminary data indicate that (1) mice deficient in claudin-18 have increased alveolar permeability to albumin and the specific knockdown of claudin-18 in primary alveolar epithelial cells induces hyperpermeability; (2) claudin-18 null mice develop lung injury in the postnatal period, progressive fibrosis, and transforming growth factor-? (TGF?) activation; and (3) inflammation induces a specific loss of claudin-18 associated with increased permeability. Based on this preliminary data, the overall objective of this application is to elucidate the function of claudin-18 and to determine the role f this tight junction protein in the pathogenesis of acute lung injury. Aim 1 will test the hypothesi that claudin-18 is a unique paracellular barrier to macromolecules though studies of lung fluid balance in a novel claudin-18 deficient mouse and barrier function in primary alveolar epithelial cells deficient in claudin-18. Aim 2 will determine the mechanism of lung injury in the setting of claudin-18 deficiency and will investigate the link between barrier dysfunction, lung injury, and TGF-? activation. Aim 3 will determine the role of claudin-18 in clinically relevant models of acute lung injury through studies in ex vivo perfused human lung preparations. Dr. LaFemina's career development during this award will be organized around these aims and guided by formal mentorship and coursework. Dr. LaFemina has assembled a multidisciplinary team of UCSF senior investigators to mentor him: Dean Sheppard, MD, Professor of Medicine and an expert in integrin mediated activation of TGF-?; James Frank, MD, Associate Professor of Medicine and an expert in basic mechanisms of acute lung injury and tight junction biology; and Michael Matthay, MD, Professor of Medicine and Anesthesia and expert investigator in the basic and clinical science of acute lung injury. Dr. LaFemina's research proposal focusing on the novel protein claudin-18 coupled with his structured training plan will allow him to accomplish his long term goal career goal of becoming an independently funded physician scientist improving patient health through the study of basic mechanisms of alveolar epithelial biology. Disruption of the barrier between air and blood in the lung can lead to respiratory failure and death. Tight junctions are protein complexes that regulate this barrier. This study will investigate the role of the tight junction protein claudin-18 in lung injury and will determine whether this protein is a potential therapeutic target.