Role of folliculin (FLCN) in lung cell survival

描述(申请人提供)：囊性空隙扩大和自发性气胸是Birt-Hogg-Dube(BHD)综合征的主要病理表现。虽然这种疾病的病因尚不清楚，但BHD中的肺囊肿与肿瘤抑制基因毛囊蛋白(Flcn)的常染色体显性突变失活有关。Flcn是一种在所有物种中普遍表达的同源性很高的蛋白，缺乏明显的功能结构域，通过接头蛋白FNIP1/2与5‘-AMP激活的蛋白激酶(AMPK)结合。然而，对毛囊蛋白(Flcn)在肺细胞存活中的作用知之甚少。我们的体外和体内研究表明，Flcn是肺细胞存活所必需的，它通过作用于 5‘-AMP激活的蛋白激酶(AMPK)-结节性硬化症复合体2(TSC2)-雷帕霉素复合体2的哺乳动物靶标(MTORC2)信号通路。为了填补目前对空域扩大的理解的空白，我们将这一提议的范围限制在一个可测试的中心假设，即肺细胞生存所需的Flcn。为了验证我们的假设，在目标1中，我们将使用Pi的实验室产生的新的转基因FLCNf/f：SP-C-CRE小鼠来确定在体内肺上皮细胞存活是否需要FLCN。在表达SP-C的肺上皮细胞中定向条件性诱导缺失Flcn，将使我们能够识别特定的肺上皮细胞类型，受Flcn缺失的影响，促进肺泡空间扩大。在目标2中，我们将研究FLCN是否是维持上皮细胞形态和新陈代谢所必需的。在目标3中，我们将确定Flcn在调节Akt和AMPK激酶活性中的作用，以及AMPK的药理激活是否会通过定向诱导缺失Flcn来挽救FLCNf/f：SP-C-CRE小鼠的肺上皮细胞存活。这些研究将确定Flcn在肺细胞存活中的作用，为深入了解肺上皮细胞-细胞接触、肌动蛋白细胞骨架和新陈代谢的分子机制提供深入了解。这些研究还将利用我们独特的新型FLCNf/f：SP-C-Cre转基因小鼠建立Flcn丢失和囊腔扩大之间的机制联系，并为治疗BHD的新治疗方法确定潜在的分子靶点(S)。 公共卫生相关性：这些研究将确定Flcn在肺细胞生存中的作用，并将为了解肺上皮细胞相互作用、肌动蛋白细胞骨架和受Flcn调控的代谢的细胞和分子机制提供见解。虽然我们目前的具体目标集中在Flcn丢失，因为它与BHD综合征有关，但我们的长期目标是为其他肺部疾病的肺细胞存活和囊性间隙扩大的机制提供见解，并为新的治疗方法确定潜在的分子靶点(S)。

DESCRIPTION (provided by applicant): Cystic airspace enlargement and spontaneous pneumothorax are major pathological manifestations Birt-Hogg- Dube (BHD) syndrome. Although the etiology of this disease is not known, lung cysts in BHD are linked to autosomal dominant mutational inactivation of tumor suppressor gene folliculin (FLCN). FLCN, a 64-kDa ubiquitously expressed protein with high homology throughout species that lacks apparent functional domain, through adaptor proteins FNIP1/2, binds the 5'-AMP-activated protein kinase (AMPK). Little, however, is known about a role of folliculin (FLCN) in lung cell survival. Our in vitro and in vivo studies demonstrate that FLCN is required for lung cell survival by acting within 5'-AMP-activated protein kinase (AMPK) - tuberous sclerosis complex 2 (TSC2) - mammalian target of rapamycin complex 2 (mTORC2) signaling pathway. To fill a gap in the current understanding of airspace enlargement, we have restricted the scope of this proposal to one testable, central hypothesis that FLCN is required for lung cell survival. To test our hypothesis, in Aim 1, we will determine whether FLCN is required for lung epithelial cell survival in vivo using new transgenic FLCNf/f:SP-C- Cre mice generated in PI's lab. Targeted conditional inducible deletion of FLCN in SP-C-expressing lung epithelial cells will allow us to identify the specific lung epithelial cell type affected by FLCN loss that promotes alveolar space enlargement. In Aim 2 we will examine whether FLCN is required for maintenance of epithelial cell morphology and metabolism. In Aim 3, we will determine FLCN role in regulating activities of Akt and AMPK kinases, and whether pharmacological activation of AMPK will rescue lung epithelial cell survival with targeted inducible deletion of FLCN in FLCNf/f:SP-C-Cre mice. These studies will identify the role of FLCN in lung cell survival, provide insights into the cellular an molecular mechanism of lung epithelial cell-cell contacts, actin cytoskeleton, and metabolism regulated by FLCN. These studies will also establish a mechanistic link between loss of FLCN and cystic airspace enlargement by using our unique novel FLCNf/f:SP- C-Cre transgenic mice and identify potential molecular target(s) for novel therapeutic approaches to treat BHD. PUBLIC HEALTH RELEVANCE: These studies will identify the role of FLCN in lung cell survival, and will provide insights into the cellular and molecular mechanism of lung epithelial cell interactions, actin cytoskeleton, and metabolism regulated by FLCN. Although our immediate specific aims focus on FLCN loss as it relates to BHD syndrome, our long term goals are to provide insights into mechanisms of lung cell survival and cystic airspace enlargement in other pulmonary diseases and to identify potential molecular target(s) for novel therapeutic approaches.