The Biology of the ABCA3 Lipid Transporter in Health and Disease

 描述（由申请人提供）：ABCA 3作为脂质和磷脂转运蛋白发挥作用，对板层体的生物发生至关重要。继我们在肺泡II型（AT 2）细胞中发现ABCA 3后，大量令人信服的报告强调了其对肺部健康和疾病的重要性，这些报告将ABCA 3的突变与各种肺部疾病联系起来，包括新生儿中的致命表面活性剂缺乏症和大龄儿童和成人的慢性间质性肺病（ILD）。基于我们先前对ABCA 3基本细胞生物学的研究，该项目将使用综合和还原方法来定义与人类遗传性肺部疾病相关的ABCA 3蛋白的两种不同类型的突变亚型的AT 2细胞表达对肺的细胞和器官型后果的机制和途径。我们已经确定了几个ABCA 3突变，在体外表现出功能（转运）或运输缺陷，后者诱导ER应激和细胞毒性。此外，我们已经开发了一种新的转基因敲入（KI）小鼠模型，表达最常见的临床变异ABCA 3（ABCA 3 E292 V），发展年龄依赖性肺实质重塑。我们的初步数据表明，这种功能性ABCA 3突变体破坏细胞的大自噬，通过溶酶体依赖性和ER应激非依赖性途径产生细胞毒性。我们的工作模型提出，ILD相关的ABCA 3突变激发了一组类别特异性的、不同的改变的AT 2细胞反应，然后驱动异常的肺损伤/重塑。该项目包含三个主题相互关联的具体目标，解决对肺细胞生物学至关重要的新兴主题： 蛋白质质量控制、细胞器稳态和细胞保护。具体目标1将表征体内转运缺陷ABCA 3E 292 V突变体表达引起的AT 2细胞功能障碍的潜在机制。具体目标2将研究ABCA 3E 292 V肺对外源性“第二次打击”的脆弱性，并确定伴随的ER应激在促进和增强异常肺重塑中的作用。Specific Aim 3将利用我们最近开发的第二种新型ILD KI小鼠模型，该模型携带表面活性蛋白C（SP-C）基因SP-CI 73 T的最常见ILD相关突变，我们最近发现该突变也会严重破坏细胞质量控制，包括自噬。使用这种新的双基因模型，我们将评估SP-CI 73 T共表达在调节ABCA 3E 292 V突变相关病理中的后果。利用AT 2细胞中的罕见基因突变作为模型的拟议研究的结果不仅将增强我们对家族性ILD病理生理学基础的分子机制的了解，而且还将更广泛地促进对AT 2细胞功能障碍诱导的异常肺重塑的意义的更好理解，并为散发性肺纤维化的靶向治疗的未来开发提供策略。

 DESCRIPTION (provided by applicant): ABCA3 functions as a lipid and phospholipid transporter and is critical for the biogenesis of lamellar bodies. Following our discovery of ABCA3 in alveolar type II (AT2) cells, its importance to lung health and disease has been highlighted by an abundance of compelling reports linking mutations in ABCA3 to various lung disorders, including fatal surfactant deficiency in newborns and chronic interstitial lung disease (ILD) in older children and adults. Building upon our prior work characterizing the basic cell biology of ABCA3, this project will use both integrative and reductionist approaches to define mechanisms and pathways underlying the cellular and organotypic consequences for the lung from the expression by AT2 cells of two distinct classes of mutant isoforms of ABCA3 proteins associated with inherited lung disorders in humans. We have identified several ABCA3 mutations that in vitro exhibit either functional (transporter) or trafficking defects with the later inducing ER stress and cytotoxicity. Furthermore, we have developed a novel transgenic knock-in (KI) mouse model expressing the most common clinical variant of ABCA3 (ABCA3E292V) that develops age dependent parenchymal lung remodeling. Our preliminary data demonstrate that this functional ABCA3 mutant disrupts cellular macroautophagy, producing cytotoxicity by lysosome-dependent and ER stress-independent pathways. Our working model proposes that ILD-associated ABCA3 mutations elicits a class-specific, distinct set of altered AT2 cell responses which then drives abnormal lung injury/remodeling. This project contains three thematically interrelated specific aims that address emerging themes critical to lung cell biology: protein quality control, organelle homeostasis, and cytoprotection. Specific Aim 1 will characterize the mechanisms underlying AT2 cell dysfunction from expression of the transport-deficient ABCA3E292V mutant in vivo. Specific Aim 2 will study the vulnerability of the ABCA3E292V lung to exogenous "2nd hits", and determine the role of concomitant ER stress in promoting and enhancing abnormal lung remodeling. Specific Aim 3 will utilize a second novel KI mouse model of ILD we recently developed bearing the most common ILD-associated mutation of the surfactant protein C (SP-C) gene, SP-CI73T, which we have recently shown to also profoundly disrupt cellular quality control including autophagy. Using this novel bi-genic model, we will then assess the consequences of SP-CI73T co-expression in modulating ABCA3E292V mutation associated pathology. Results from the proposed studies utilizing rare gene mutations in AT2 cells as models will not only enhance our knowledge of the molecular mechanisms underlying the pathophysiology of familial ILD, but also more broadly promote a better understanding of the significance of AT2 cell dysfunction-induced aberrant lung remodeling and provide strategies for future development of targeted therapies for sporadic lung fibrosis.