Nonequilibrium Gating of CFTR on an Equilibrium Theme

Jih, Kang Yang; Hwang, Tzyh Chang

doi:10.1152/physiol.00026.2012

Cited by 33 publications

(55 citation statements)

References 84 publications

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“…A modified gating model of CFTR. This gating scheme modified from Jih and Hwang (2012) incorporates the mechanism for ATPdependent inhibition of G551D gating in our previous study (Lin et al, 2014) as well as data in the current report. Two states, O 0 and C 0AD , with NBD-dimerized but a vacant ATP binding site 2, are added to accommodate the mechanism of NPPB in G551D and to explain the biphasic current decay after ATP washout in G551D in previous study (Lin et al, 2014 Supplemental Fig.…”

Section: Discussionmentioning

confidence: 93%

“…A CFTR gating model (Fig. 1A) depicting energetic coupling between dimerization of CFTR's two NBDs and gate opening/closing in the TMDs was recently proposed (Jih and Hwang, 2012). In theory, mutations that disrupt any critical steps in this gating process may lead to CFTR dysfunction and hence cause CF.…”

Section: Introductionmentioning

confidence: 99%

“…This strategy is important because, however encouraging, the VX-770-rectified P o of G551D channels is still less than 10% of that of wild-type (WT) CFTR (Jih and Hwang, 2013;but compare Van Goor et al, 2009). In addition, VX-770 diminishes the effects of cyclopropanecarbonyl]-amino]-3-methylpyridin-2-yl]benzoic acid) (Cholon et al, 2014; (Jih and Hwang, 2012) for WT-CFTR gating illustrating the relationship between opening/closing of the gate (three vertical transitions), ATP binding/unbinding (two horizontal transitions on the left), NBD dimerization/dissociation (two horizontal transitions on the right), and ATP hydrolysis and dissociation of hydrolytic products (oblique transitions below). The yellow trapezoids represent CFTR's two TMDs, which craft a gated pore.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Synergistic Potentiation of Cystic Fibrosis Transmembrane Conductance Regulator Gating by Two Chemically Distinct Potentiators, Ivacaftor (VX-770) and 5-Nitro-2-(3-Phenylpropylamino) Benzoate

2016

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Cystic fibrosis (CF) is caused by loss-of-function mutations of the cystic fibrosis transmembrane conductance regulator (CFTR) gene encoding a phosphorylation-activated but ATPgated chloride channel. Previous studies suggested that VX-770 [ivacaftor, N-(2,4-di-tert-butyl-5-hydroxyphenyl)-4-oxo-1,4-dihydroquinoline-3-carboxamide], a CFTR potentiator now used in clinics, increases the open probability of CFTR by shifting the gating conformational changes to favor the open channel configuration. Recently the chloride channel blocker and CFTR potentiator 5-nitro-2-(3-phenylpropylamino) benzoate (NPPB) has been reported to enhance CFTR activity by a mechanism that exploits the ATP hydrolysis-driven, nonequilibrium gating mechanism unique to CFTR. Surprisingly however, NPPB increased the activity of nonhydrolytic G551D-CFTR, the third most common disease-associated mutation. Here, we further investigated the mechanism of NPPB's effects on CFTR gating by assessing its interaction with well-studied VX-770. Interestingly, once G551D-CFTR was maximally potentiated by VX-770, NPPB further increased its activity. However, quantitative analysis of this drug-drug interaction suggests that this pharmacologic synergism is not due to independent actions of NPPB and VX-770 on CFTR gating; instead, our data support a dependent mechanism involving two distinct binding sites. This latter idea is further supported by the observation that the locked-open time of a hydrolysis-deficient mutant K1250A was shortened by NPPB but prolonged by VX-770. In addition, the effectiveness of NPPB, but not of VX-770, was greatly diminished in a mutant whose second nucleotide-binding domain was completely removed. Interpreting these results under the framework of current understanding of CFTR gating not only reveals insights into the mechanism of action for different CFTR potentiators but also brings us one step forward to a more complete schematic for CFTR gating.

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Section: Discussionmentioning

confidence: 93%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Synergistic Potentiation of Cystic Fibrosis Transmembrane Conductance Regulator Gating by Two Chemically Distinct Potentiators, Ivacaftor (VX-770) and 5-Nitro-2-(3-Phenylpropylamino) Benzoate

2016

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“…Like many other members of this superfamily, CFTR possesses two transmembrane domains (TMD1 and TMD2), each of which comprises six transmembrane segments (TMs). At the end of each TMD lies a nucleotide binding domain (NBD1 and NBD2, respectively), which plays a critical role in controlling channel gating via ATP-induced NBD dimerization and hydrolysis-triggered separation of the dimer (12,13). In addition, a regulatory domain (R domain), linking two TMD/NBD complexes, harbors multiple consensus sites for protein kinase A (PKA)-dependent phosphorylation (14).…”

Section: As [Au(cn) 2 ]mentioning

confidence: 99%

Localizing a gate in CFTR

Gao

Hwang

2015

Proc. Natl. Acad. Sci. U.S.A.

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Experimental and computational studies have painted a picture of the chloride permeation pathway in cystic fibrosis transmembrane conductance regulator (CFTR) as a short narrow tunnel flanked by wider inner and outer vestibules. Although these studies also identified a number of transmembrane segments (TMs) as porelining, the exact location of CFTR's gate(s) remains unknown. Here, using a channel-permeant probe, [Au (CN − when the open probability is markedly reduced by introducing a second mutation, G1349D. As [Au(CN) 2 ]− and chloride ions share the same permeation pathway, these results imply a gate is situated between amino acid residues 337 and 344 along TM6, encompassing the very segment that may also serve as the selectivity filter for CFTR. The unique position of a gate in the middle of the ion translocation pathway diverges from those seen in ATP-binding cassette (ABC) transporters and thus distinguishes CFTR from other members of the ABC transporter family.cystic fibrosis | gating | ABC transporters | anion channels

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“…CF is characterized by abnormal transport of chloride and sodium ions across multiple epithelia, leading to thick and viscous secretions (Morgan et al 2013). CFTR belongs to a large group of membrane ATPases, the ATP binding cassette (ABC) transporter family, but it is unique within this large family of proteins in acting as an ion channel that mediates passive anion movement across the membrane (Gadsby et al 2006;Jih and Hwang 2012;Sheppard and Welsh 1999).…”

Section: Introductionmentioning

confidence: 99%

Conformational changes opening and closing the CFTR chloride channel: Insights from cysteine scanning mutagenesis

Hiani

Linsdell

2014

Biochem. Cell Biol.

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Cystic fibrosis, the most common lethal genetic disease affecting young people in North America, is caused by failure of the chloride ion channel known as CFTR (cystic fibrosis transmembrane conductance regulator). CFTR belongs to the large family of ATP-binding cassette (ABC) membrane transporters. In CFTR, ATP-driven events at the nucleotide-binding domains (NBDs) open and close a gate that controls chloride permeation. However, the conformational changes concomitant with opening and closing of the CFTR gate are unknown. Diverse techniques including substituted cysteine accessibility method, disulfide cross-linking, and patch-clamp recording have been used to explore CFTR channel structure. Here, we consider the architecture of both the open and the closed CFTR channel. We review how CFTR channel structure changes between the closed and the open channel conformations and portray the relative function of both cytoplasmic and vestigial gates during the gating cycle. Understanding how the CFTR channel gates chloride permeation is central for understanding how CFTR defects lead to CF. Such knowledge opens the door for novel ways to maximize CFTR channel activity in a CF setting.

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Nonequilibrium Gating of CFTR on an Equilibrium Theme

Cited by 33 publications

References 84 publications

Synergistic Potentiation of Cystic Fibrosis Transmembrane Conductance Regulator Gating by Two Chemically Distinct Potentiators, Ivacaftor (VX-770) and 5-Nitro-2-(3-Phenylpropylamino) Benzoate

Synergistic Potentiation of Cystic Fibrosis Transmembrane Conductance Regulator Gating by Two Chemically Distinct Potentiators, Ivacaftor (VX-770) and 5-Nitro-2-(3-Phenylpropylamino) Benzoate

Localizing a gate in CFTR

Conformational changes opening and closing the CFTR chloride channel: Insights from cysteine scanning mutagenesis

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