CYSTIC FIBROSIS TRANSMEMBRANE CONDUCTANCE REGULATOR

囊性纤维化跨膜电导调节器

• 批准号: 7378912
• 负责人: Garry R Cutting
• 金额: $ 0.23万
• 依托单位: JOHNS HOPKINS UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-12-01 至 2006-11-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7378912
• 关键词: CYSTIC; FIBROSIS; TRANSMEMBRANE; CONDUCTANCE; REGULATOR

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.

该子项目是利用 NIH/NCRR 资助的中心拨款提供的资源的众多研究子项目之一。子项目和研究者 (PI) 可能已从另一个 NIH 来源获得主要资金，因此可以在其他 CRISP 条目中出现。列出的机构是中心的机构，不一定是研究者的机构。囊性纤维化 (CF) 是一种常染色体隐性遗传疾病，由囊性纤维化跨膜电导调节器 (CFTR) 突变引起，CFTR 是许多器官系统上皮细胞中的主要氯 (Cl-) 通道。在CF患者中，Cl-跨上皮细胞膜转运的严重减少会导致阻塞性肺病、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 的特定突变造成的，但具有相同突变的患者之间存在极大的变异性，这表明 CFTR 基因型以外的因素可能会导致疾病的严重程度。 通过上游信号事件调节正常 CFTR 功能的基因是 CF 的合理候选修饰因子。 CFTR 的上游调节依赖于 cAMP，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 的磷酸化进行调节。在上皮细胞中，cAMP 水平通过 G 蛋白受到细胞外激动剂的影响偶联跨膜受体。因此，CFTR 活性可能受到激活腺苷酸环化酶并产生 cAMP 的 G 蛋白偶联信号传导过程的影响。我们有兴趣研究该上游激活途径中的基因在调节 CFTR 功能以及疾病严重程度方面的作用。 为此，我们建议研究该通路相关基因发生严重改变的患者的 CFTR 功能。 奥尔布赖特遗传性骨营养不良 (AHO) 患者经证明，β-肾上腺素能刺激后 cAMP 水平降低。在过去的十年中，这已被证明是由于 GNAS1 的突变所致，GNAS1 是编码异源三聚体 G 蛋白 (Gs-alpha) 刺激性 α 亚基的基因。携带 GNAS1 突变的患者具有特征性的身体表型，包括身材矮小、短指、肥胖、圆形面容和皮下骨化。这些患者中的一部分还存在激素抵抗，通常定义为肾脏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具有抵抗力。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 GNAS1 突变的患者在激素抵抗方面可能有不同的表型。我们有一名 AHO 患者的初步数据，该患者鼻上皮和皮肤对 β 激动剂的 CFTR 反应降低。这表明 Gs-alpha 功能改变与 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，我们建议表征 AHO 患者的 CFTR 功能。通过检查上皮组织中的 GNAS1 RNA 水平和 cAMP 水平，我们将定义通过 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。这项研究的结果将明确 cAMP 依赖性通路在 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 患者的激素抵抗机制，因为这将是第一项在体内直接表征 GNAS1 突变对其细胞靶点的影响的研究。家庭成员的结果将有助于 AHO 的基因型-表型相关性，并阐明家族变异造成的功能缺陷。