Molecular Pathophysiology of Cystic Fibrosis

描述（由申请人提供）：囊性纤维化（CF）是美国最常见的致命遗传性疾病，由CFTR（囊性纤维化跨膜传导调节因子）基因的功能丧失突变引起。作为ABC （ATP Binding Cassette）转运体超家族的成员，CFTR拥有两个核苷酸结合结构域（NBD1和NBD2），其特征是典型的Walker a和B基序，用于ATP结合/水解，以及一个特征序列（即LSGGQ），该序列在ATP结合时形成首尾相连的NBD二聚体中起关键作用。CFTR的独特之处在于，CFTR不是一个活性转运体，而是一个真正的离子通道，它利用ATP驱动其门控转变的构象变化。我们过去的研究为CFTR的门控机制提供了新的见解。流行的模型认为，每个NBD/TMD复合物作为ABC转运体的刚体同步运动，这与ATP水解与门控循环严格耦合的普遍观点相反，我们的数据支持了一个令人振奋的替代观点，即这两个结构域各自具有自主性，但却在能量上耦合。这一新的机制从机制上解释了fda批准的CF治疗药物VX-770 （Ivacaftor）是如何利用tmd和nbd之间明显不完美的耦合起作用的。我们最近对CFTR离子渗透途径的生物物理研究也为我们提出一些基本问题奠定了坚实的基础，例如（目标1）：孔是由什么组成的？CFTR的登机口在哪里？CFTR如何选择阴离子和阳离子？我们对疾病相关的G551D突变中出现的门控缺陷的机制研究不仅挑战了一家大型制药公司的数据，我们的结果也表明一个有趣的和可测试的假设这个签名的glycine-to-aspartate突变序列转换catalysis-competent ATP结合位点抑制网站(目标2)。[我们相信一个清晰的理解的雌性生殖道功能的分子细节和vx - 770等药物如何影响雌性生殖道功能的不同方面(目标3)在治疗试剂的设计将帮助治疗CF,分泌性腹泻,和其他CFTR-associated疾病。)

DESCRIPTION (provided by applicant): Cystic fibrosis (CF), the most common fatal genetic disease in the US, results from loss- of-function mutations in the CFTR (Cystic Fibrosis Transmembrane conductance Regulator) gene. As a member of the ABC (ATP Binding Cassette) transporter superfamily, CFTR harbors two nucleotide binding domains (NBD1 and NBD2) characterized by the canonical Walker A and B motifs for ATP binding/hydrolysis, and a signature sequence (i.e., LSGGQ) that plays a critical role for the formation of a head-to- tail NBD dimer upon ATP binding. CFTR is unique in that, instead of being an active transporter, CFTR is a bona fide ion channel, which utilizes ATP to drive conformational changes in its gating transitions. Our studies in the past have provided novel insights into the gating mechanism of CFTR. Contrary to the prevailing view that ATP hydrolysis is strictly coupled to the gating cycle, an idea supported by the popular model depicting that each NBD/TMD complex moves synchronously as a rigid body for ABC transporters, our data support a provocative alternative that these two domains assume autonomy on its own but are coupled energetically. [This novel mechanism turns out to explain mechanistically how an FDA-approved drug for CF treatment, VX-770 (Ivacaftor), works by exploiting this apparently imperfect coupling between TMDs and NBDs.] Our recent biophysical studies of CFTR's ion permeation pathway also establish a solid foundation for us to ask fundamental questions such as (Aim 1): What make up the pore? Where is the gate of CFTR? How does CFTR select anions versus cations? Our mechanistic studies of the gating defects manifested in the disease-associated G551D mutation not only challenge data from a major pharmaceutical company, our results also suggest an intriguing and testable hypothesis that this glycine-to-aspartate mutation in the signature sequence converts the catalysis-competent ATP binding site to an inhibitory site (Aim 2). [We believe a clear understanding of the CFTR function to a molecular detail and of how drugs such as VX-770 affect different aspects of CFTR function (Aim 3) will aid in the design of therapeutic reagents for the treatment of CF, secretory diarrhea, and other CFTR-associated diseases.]