Molecular Pathophysiology of Cystic Fibrosis

描述（由申请人提供）：囊性纤维化（CF）是美国最常见的致死性遗传疾病，由CFTR（囊性纤维化跨膜传导调节因子）基因的功能缺失突变引起。作为ABC（ATP结合盒）转运蛋白超家族的成员，CFTR具有两个核苷酸结合结构域（NBD 1和NBD 2），其特征在于用于ATP结合/水解的典型步行者A和B基序，以及特征序列（即，LSGGQ），其在ATP结合后形成头-尾NBD二聚体中起关键作用。CFTR的独特之处在于，CFTR不是一种主动转运蛋白，而是一种真正的离子通道，它利用ATP来驱动其门控转换中的构象变化。我们过去的研究为CFTR的门控机制提供了新的见解。相反，普遍认为ATP水解严格耦合到门控循环，一个流行的模型，描绘每个NBD/TMD复杂的移动同步作为一个刚性的ABC转运体的想法支持，我们的数据支持一个挑衅性的替代方案，这两个域承担自主权，但耦合大力。[This一种新的机制从机械上解释了FDA批准的CF治疗药物VX-770（依伐卡托）如何通过利用TMD和NBD之间这种明显不完美的偶联来发挥作用。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基本问题奠定了坚实的基础，例如（目标1）：什么构成了孔？CFTR的大门在哪里？CFTR如何选择阴离子和阳离子？我们对疾病相关G551 D突变中表现出的门控缺陷的机制研究不仅挑战了来自一家大型制药公司的数据，我们的结果还提出了一个有趣且可检验的假设，即签名序列中的甘氨酸-天冬氨酸突变将催化活性ATP结合位点转化为抑制位点（Aim 2）。[We相信清楚地了解CFTR功能的分子细节以及VX-770等药物如何影响CFTR功能的不同方面（目的3）将有助于设计用于治疗CF、分泌性腹泻和其他CFTR相关疾病的治疗试剂。

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.]