CYSTIC FIBROSIS TRANSMEMBRANE CONDUCTANCE REGULATOR

这个子项目是许多研究子项目中的一个 由NIH/NCRR资助的中心赠款提供的资源。子项目及 研究者（PI）可能从另一个NIH来源获得了主要资金， 因此可以在其他CRISP条目中表示。所列机构为 研究中心，而研究中心不一定是研究者的研究机构。 囊性纤维化（CF）是一种常染色体隐性遗传疾病，由囊性纤维化跨膜传导调节因子（CFTR）突变引起，CFTR是许多器官系统上皮细胞中的主要氯离子（Cl-）通道。 在CF患者中，Cl-跨上皮细胞膜转运的严重减少导致阻塞性肺病、慢性鼻窦炎、胰腺功能不全、肠梗阻和男性不育。 虽然基因型-表型相关性表明临床表现的一些变异性是由于CFTR中的特定突变，但具有相同突变的患者中存在极端变异性，表明CFTR基因型以外的因素可能导致疾病严重程度。 通过上游信号事件调节正常CFTR功能的基因是CF的合理候选修饰剂。 CFTR的上游调控是cAMP依赖性的，最近的研究表明CFTR介导的Cl-转运通过环AMP（cAMP）依赖性蛋白激酶A的磷酸化来调节。 在上皮细胞中，cAMP水平通过G蛋白偶联的跨膜受体受到细胞外激动剂的影响。 因此，CFTR活性可受到G蛋白偶联的信号传导过程的影响，所述信号传导过程激活腺苷酸环化酶并产生cAMP。 我们感兴趣的是研究基因在上游激活途径中调节CFTR功能的作用，进而影响疾病的严重程度。 为此，我们建议研究CFTR功能的患者与严重改变的基因参与这一途径。 患有奥尔布赖特遗传性骨营养不良（AHO）的患者已被证明响应于β-肾上腺素能刺激而具有降低的cAMP水平。 在过去的十年中，这已被证明是由于GNAS 1的突变，该基因编码异源三聚体G蛋白（Gs-alpha）的刺激性α亚基。 具有GNAS 1突变的患者具有特征性的身体表型，包括身材矮小、短指（趾）畸形、肥胖、圆形面容和皮下骨化。 这些患者的一个子集也有激素抵抗，经典定义为肾对甲状旁腺激素的反应降低，但许多患者也被证明对通过GS-α发出信号的其他激素有抵抗。这种激素抵抗的确切机制尚不清楚，因为同一家族中携带相同GNAS 1突变的患者在激素抵抗方面可能具有不同的表型。 我们有一名AHO患者的初步数据，该患者的CFTR对鼻上皮和皮肤中的β受体激动剂的反应降低。 这表明GS-α功能改变和CFTR功能降低之间存在联系。 为了更好地了解cAMP依赖性通路在调节CFTR功能中的作用，我们建议对AHO患者的CFTR功能进行表征。 通过检查上皮组织中的GNAS 1 RNA水平和cAMP水平，我们将确定通过cAMP依赖性途径的预期通量水平。 然后将在这些相同的组织中评估CFTR功能。 这项研究的结果将确定cAMP依赖性途径在CFTR功能中的作用，这可能会指导CF患者未来的治疗选择。 它还可能解决AHO患者激素抵抗的机制，因为这将是第一项直接在体内表征GNAS 1突变对其细胞靶点之一的影响的研究。 来自家族成员的结果将有助于AHO的基因型-表型相关性，并澄清来自家族变异的功能缺陷。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Cystic Fibrosis is (CF) is an autosomal recessive disorder caused by mutations in the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR), the primary chloride (Cl-) channel in epithelial cells of numerous organ systems. In CF patients, a severe reduction in Cl- transport across epithelial cell membranes results in obstructive pulmonary disease, chronic sinusitis, pancreatic insufficiency, intestinal obstruction, and male infertility. While genotype-phenotype correlations have shown that some of the variablility in clinical presentation is due to specific mutations in CFTR, extreme variability exists among patients with identical mutations suggesting factors other than CFTR genotype may contribute to disease severity. Genes regulating normal CFTR function via upstream signaling events are rational candidate modifiers of CF. Upstream regulation of CFTR is cAMP dependent, and recent studies have shown CFTR mediated Cl- transport is modulated through phosphorylation by cyclic AMP (cAMP)-dependent protein kinase A. In epithelial cells cAMP levels are influenced by extra-cellular agonists via G-protein coupled transmembrane receptors. Thus, CFTR activity can be affected by G-protein coupled signaling processes that activate adenylyl cyclase and which generate cAMP. We are interested in investigating the role of genes in this upstream activation pathway in modulating the function of CFTR, and in turn disease severity. To this end, we propose to study CFTR function in patients with severe alterations in genes involved in this pathway. Patients with Albright's Hereditary Osteodystrophy (AHO) have been shown to have decreased cAMP levels in response to beta-adrenergic stimulation. Over the last decade this has been shown to be due to mutations in GNAS1, the gene that encodes the stimulatory alpha subunit of heterotrimeric G proteins (Gs-alpha). Patients with mutations in GNAS1 have a characteristic physical phenotype including short stature, brachydactyly, obesity, rounded facies, and subcutaneous ossifications. A subset of these patients also have hormone resistance, classically defined as decreased renal response to parathyroid hormone, but many patients have also been documented to have resistance to other hormones that signal via Gs-alpha. The exact mechanism for this hormone resistance is unclear, as patients within the same family and carrying the same mutation in GNAS1 can have variable phenotypes with regard to hormone resistance. We have preliminary data on one patient with AHO who has a decreased CFTR response to beta-agonists in the nasal epithelia and the skin. This suggests a link between altered Gs-alpha function and decreased CFTR function. To better understand the role of the cAMP-dependent pathway in modulating CFTR function, we propose to characterize CFTR function in patients with AHO. By examining GNAS1 RNA levels and cAMP levels in epithelial tissues, we will define the expected level of flux through the cAMP dependent pathway. CFTR function will then be assessed in these same tissues. The results of this study will define the role of the cAMP-dependent pathway in CFTR function, which may guide future therapeutic options for patients with CF. It may also address the mechanism of hormone resistance in AHO patients since it will be the first study directly characterizing, in vivo, the effects of GNAS1 mutation on one of its cellular targets. Results from family members will aid in genotype-phenotype correlations in AHO and clarify functional defects from familial variation.