Role of folliculin (FLCN) in lung cell survival

描述（申请人提供）：囊腔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卵泡素（FLCN）的常染色体显性突变失活有关。FLCN是一种64-kDa的广泛表达的蛋白，在整个物种中具有高度同源性，缺乏表观功能结构域，通过衔接蛋白FNIP 1/2结合5'-AMP-活化蛋白激酶（AMPK）。然而，很少有人知道卵泡素（FLCN）在肺细胞存活中的作用。我们的体外和体内研究表明，FLCN是肺细胞存活所必需的， 5'-AMP-活化蛋白激酶（AMPK）-结节性硬化症复合物2（TSC 2）-雷帕霉素复合物2（mTORC 2）哺乳动物靶标信号通路。为了填补当前对空域扩大的理解中的空白，我们将该提案的范围限制在一个可测试的核心假设上，即FLCN是肺细胞生存所必需的。为了验证我们的假设，在目标1中，我们将使用PI实验室中产生的新的转基因FLCNf/f：SP-C-Cre小鼠来确定FLCN是否是肺上皮细胞体内存活所必需的。在表达SP-C的肺上皮细胞中有针对性的FLCN条件诱导缺失将使我们能够鉴定受FLCN损失影响的特定肺上皮细胞类型，FLCN损失促进肺泡腔扩大。在目标2中，我们将研究FLCN是否需要维持上皮细胞的形态和代谢。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，以及在FLCNf/f：SP-C-Cre小鼠中，AMPK的药理学激活是否会通过FLCN的靶向诱导缺失来拯救肺上皮细胞存活。这些研究将确定FLCN在肺细胞存活中的作用，提供对肺上皮细胞-细胞接触、肌动蛋白细胞骨架和FLCN调节的代谢的细胞和分子机制的见解。这些研究还将通过使用我们独特的新型FLCNf/f：SP-C-Cre转基因小鼠建立FLCN损失和囊腔扩大之间的机制联系，并鉴定用于治疗BHD的新型治疗方法的潜在分子靶标。

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.