CFTR (Cystic Fibrosis Transmembrane conductance Regulator) is a chloride channel that plays a critical role in mediating epithelial chloride secretion and absorption. Being a member of the ABC (ATP Binding Cassette) transporter superfamily, CFTR possesses two nucleotide binding domains (NBD1 and NBD2) characterized by the canonical Walker A and B motifs for ATP binding/hydrolysis, and the signature sequence whose function remains unknown. The functional importance of the signature sequence is attested by the fact that many disease-associated mutations are found in the signature sequence of either NBD1 (e.g., G551D) or NBD2 (e.g., G1349D). Interestingly, while the G551D mutation is associated with severe form CF, the G1349D mutation causes mild form disease, indicating that these two signature sequences play distinct roles in controlling CFTR function. Since the ABC transporter superfamily encompasses members that play a variety of physiological roles such as transport of cholesterol, drug resistance in cancers, cardiac membrane excitability and insulin secretion, understanding how CFTR works at a molecular level will have a broad impact on both basic sciences and clinical medicine. Recent solution of X-ray crystal structure of CFTR's N-terminal nucleotide binding domain (NBD1) has opened the door for detailed studies of the role of signature sequences in controlling CFTR function. The current proposal will employ a combination of electrophysiolgical, molecular biological and structural biological techniques to address how mutations in the signature sequences cause CFTR dysfunction (Aim 1). Since defects of these mutations are likely to be amended by small-molecule, pharmacological reagents, we will investigate the mechanism by which some of the known compounds work on CFTR (Aim 2). Once succeeded, we will launch structure- based drug design to discover new compounds with high potency and efficacy. A clear understanding of the molecular mechanisms of CFTR dysfunction caused by mutations and the physical/chemical mechanism of drug actions on CFTR will aid in design of therapeutical reagents for the treatment of CF and other CFTR-associated diseases.

Public Health Relevance

Cystic fibrosis, the most common fatal genetic disease in the US, is caused by mutations of the CFTR protein. The goal of the application is to understand how disease-associated mutations cause dysfunction of CFTR and how small-molecule compounds restore the function of mutant CFTR.

National Institute of Health (NIH)
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Research Project (R01)
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Cellular and Molecular Biology of the Kidney Study Section (CMBK)
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Mckeon, Catherine T
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University of Missouri-Columbia
Schools of Medicine
United States
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Hwang, Tzyh-Chang; Yeh, Jiunn-Tyng; Zhang, Jingyao et al. (2018) Structural mechanisms of CFTR function and dysfunction. J Gen Physiol 150:539-570
Zhang, Jingyao; Hwang, Tzyh-Chang (2017) Electrostatic tuning of the pre- and post-hydrolytic open states in CFTR. J Gen Physiol 149:355-372
Yeh, Han-I; Sohma, Yoshiro; Conrath, Katja et al. (2017) A common mechanism for CFTR potentiators. J Gen Physiol 149:1105-1118
Jih, Kang-Yang; Lin, Wen-Ying; Sohma, Yoshiro et al. (2017) CFTR potentiators: from bench to bedside. Curr Opin Pharmacol 34:98-104
Gao, Xiaolong; Hwang, Tzyh-Chang (2016) Spatial positioning of CFTR's pore-lining residues affirms an asymmetrical contribution of transmembrane segments to the anion permeation pathway. J Gen Physiol 147:407-22
Yu, Ying-Chun; Sohma, Yoshiro; Hwang, Tzyh-Chang (2016) On the mechanism of gating defects caused by the R117H mutation in cystic fibrosis transmembrane conductance regulator. J Physiol 594:3227-44
Lin, Wen-Ying; Sohma, Yoshiro; Hwang, Tzyh-Chang (2016) Synergistic Potentiation of Cystic Fibrosis Transmembrane Conductance Regulator Gating by Two Chemically Distinct Potentiators, Ivacaftor (VX-770) and 5-Nitro-2-(3-Phenylpropylamino) Benzoate. Mol Pharmacol 90:275-85
Yeh, Han-I; Yeh, Jiunn-Tyng; Hwang, Tzyh-Chang (2015) Modulation of CFTR gating by permeant ions. J Gen Physiol 145:47-60
Zhang, Jingyao; Hwang, Tzyh-Chang (2015) The Fifth Transmembrane Segment of Cystic Fibrosis Transmembrane Conductance Regulator Contributes to Its Anion Permeation Pathway. Biochemistry 54:3839-50
Gao, Xiaolong; Hwang, Tzyh-Chang (2015) Localizing a gate in CFTR. Proc Natl Acad Sci U S A 112:2461-6

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