Regulation of lung alveolar epithelial protein transport

简介(申请者提供)：我们的长期目标是 阐明与大分子相关的调控机制和途径 通过肺泡上皮运输。蛋白质转运的初步研究 在原代培养的细胞单层中，表现出表型和 肺泡I型上皮细胞的形态特征， 发现有关肺泡上皮蛋白运输的重要信息，在 一些血清蛋白(如白蛋白(Alb)和免疫球蛋白G(IgG))是 通过可饱和过程吸收的速度大于 被动扩散机制，而二聚体免疫球蛋白A(DIGA)是 通过聚合免疫球蛋白受体分泌到肺泡液中 (PIgR)介导的过程。我们最近还发现一种糖皮质激素 类似物地塞米松减少免疫球蛋白在肺泡的净吸收 上皮细胞，暗示可能调节肺泡上皮运输。 血清蛋白质由可溶性(例如，体液)因素决定。作为的逻辑扩展 对这三种关键蛋白(即白蛋白、免疫球蛋白、 Diga)跨肺泡上皮，转运机制的调节 调查过了。我们的中心假设包括：1)这三种关键蛋白质 主要利用可调节的穿透肺泡上皮屏障 囊泡运输，II)Alb和Diga的内吞作用主要是 由聚集在小窝蛋白涂层结构中的同源受体介导 (即小窝)和网囊被膜的坑，而免疫球蛋白是 由液相内吞作用内化(即，在 细胞表面由于非最佳流体pH)，以及iii)这些蛋白质的运输 在肺泡上皮细胞中有不同的调节。为了测试这些 假设，我们将研究以下四个具体目标：一)差异化 特定蛋白的肺泡上皮转运特性，II) 特定蛋白质结合/内化的特征，III) 特定蛋白跨肺泡上皮运输的调节，以及 IV)蛋白跨受损肺泡上皮运输的调节。我们会 利用原代培养的肺泡上皮细胞单层作为体外培养材料 提供差别化监管相关机制信息的模型 肺泡上皮运输的这三个关键蛋白。规管 肺泡上皮细胞表达这些关键蛋白的同源受体将 在适当的情况下接受调查。从这些研究中获得的结果将 帮助阐明易位的特定机制(和相关途径) 跨肺泡上皮的蛋白质及其同源受体的作用 关于健康和健康人肺泡上皮蛋白运输的关键蛋白 疾病。

DESCRIPTION (provided by applicant): Our long-term goal has been the elucidation of regulatory mechanisms and pathways associated with macromolecule transport across alveolar epithelium. Preliminary studies on protein transport across primary cultured cell monolayers, which exhibit phenotypic and morphological traits of in vivo alveolar epithelial Type I (ATl) cells, uncovered important information on alveolar epithelial protein transport, in that some serum proteins (e.g., albumin (Alb) and immunoglobulins G (IgG)) are absorbed via saturable processes at rates greater than those predicted by passive diffusional mechanisms, whereas dimeric immunoglobulin A (dIgA) is secreted into alveolar fluid via a polymeric immunoglobulin receptor (pIgR)-mediated process. We also found very recently that a glucocorticoid analog, dexamethasone, decreases net absorption of IgG across alveolar epithelium, implicating possible regulation of alveolar epithelial transport of serum proteins by soluble (e.g., humoral) factors. As a logical extension of these functional transport studies on these three key proteins (i.e., Alb, IgG, dIgA) across alveolar epithelium, regulation of transport mechanisms will be investigated. Our central hypotheses include i) that these three key proteins traverse the alveolar epithelial barrier predominantly utilizing regulable vesicular transport, ii) that endocytosis of Alb and dIgA is predominantly mediated by their cognate receptors clustered in caveolin-coated structures (i.e., caveolae) and clathrincoated pits, respectively, while IgG is internalized by fluid-phase endocytosis (i.e., without binding receptors at the cell surface due to non-optimal fluid pH), and iii) transport of these proteins is regulated differentially in alveolar epithelium. In order to test these hypotheses, we will study the following four Specific Aims: i) differential properties of transalveolar epithelial transport of specific proteins, ii) characterization of binding / internalization of specific proteins, iii) regulation of trafficking of specific proteins across alveolar epithelium, and iv) regulation of protein transport across injured alveolar epithelium. We will utilize primary cultured alveolar epithelial cell monolayers as an in vitro model to provide pertinent mechanistic information on differential regulation of alveolar epithelial transport of these three key proteins. Regulation of alveolar epithelial expression of cognate receptors for these key proteins will be investigated where appropriate. Results obtained from these studies will help elucidate specific mechanisms (and associated pathways) for translocation of proteins across lung alveolar epithelium and roles of the cognate receptors for the key proteins in alveolar epithelial protein transport in health and disease.