ABCMdb

PMID: 25512598

Yeh HI, Yeh JT, Hwang TC
Modulation of CFTR gating by permeant ions.
J Gen Physiol. 2015 Jan;145(1):47-60. doi: 10.1085/jgp.201411272. Epub 2014 Dec 15., [PubMed]

Sentences

No. Mutations Sentence Comment

20 ABCC7 p.Gly551Asp These include effects on single-channel kinetics of WT CFTR, deceleration of the nonhydrolytic closing rate, and potentiation of the Po of the disease-associated mutant G551D. Login to comment 25 ABCC7 p.Gly551Asp The Journal of General Physiology on December 4, 2015 jgp.rupress.org Downloaded from Published December 15, 2014 http://jgp.rupress.org/content/suppl/2015/03/23/jgp.201411272.DC1.html Supplemental Material can be found at: disease-associated mutation, G551D. Login to comment 90 ABCC7 p.Gly551Asp To test the hypothesis that NO3 &#e032; and VX-770 may interact, we examined quantitatively the effects of these two reagents in the same patch (hence the same number of channels) containing &#e044;NBD2- or G551D-CFTR (Fig. 8). Login to comment 124 ABCC7 p.Glu1371Ser The lengthening of the relaxation time constant by NO3 &#e032; was also seen with a hydrolysis-deficient mutant, E1371S-CFTR (n = 5). Login to comment 163 ABCC7 p.Asp1370Asn To this end, we introduced the D1370N mutation into the &#e044;R background and characterized gating kinetics in the presence of NO3 &#e032; or Cl&#e032; (Fig. 5 C). Login to comment 166 ABCC7 p.Asp1370Asn ABCC7 p.Asp1370Asn Comparing the single-channel kinetic parameters of D1370N-CFTR further confirms that the effect of NO3 &#e032; on both the Figure 5.ߓ Effects of NO3 &#e032; on single-channel kinetics of &#e044;R-CFTR and D1370N/&#e044;R-CFTR. Login to comment 171 ABCC7 p.Asp1370Asn (C) NO3 &#e032; increases the Po of a hydrolysis-deficient mutant CFTR (D1370N). Login to comment 172 ABCC7 p.Asp1370Asn (D) Microscopic kinetic parameters for D1370N/ &#e044;R-CFTR in the presence of bath Cl&#e032; or NO3 &#e032; . Login to comment 183 ABCC7 p.Gly551Asp Thus, the G551D-CFTR offers another opportunity to test the idea that NO3 &#e032; can affect CFTR gating independently of NBD dimerization without resorting to a more drastic manipulation of CFTR by deleting its entire NBD2. Login to comment 185 ABCC7 p.Gly551Asp NO3 &#e032; indeed increases the Po of G551D channels by approximately fourfold (Po(N)/Po(C) = 3.75 &#b1; 0.86; n = 5). Login to comment 186 ABCC7 p.Gly551Asp Moreover, kinetically, NO3 &#e032; also boosts the Po of G551D-CFTR by increasing the opening rate and decreasing the closing rate (see legend to Fig. 6). Login to comment 187 ABCC7 p.Gly551Asp ABCC7 p.Gly551Asp This result with the G551D mutant not only corroborates data with the &#e044;NBD2-CFTR but also reveals an intriguing similarity between NO3 &#e032; and a well-studied CFTR potentiator, VX-770 (Van Goor et al., 2009; Eckford et al., 2012; Jih and Hwang, 2013; Kopeikin et al., 2014), which is now used to treat cystic fibrosis patients carrying the G551D mutation. Login to comment 188 ABCC7 p.Gly551Asp In addition to a potentiation of the G551D-CFTR as well as &#e044;NBD2-CFTR channels (see Fig. 8 below), NO3 &#e032; and VX-770 share several qualitative similarities in their effects on CFTR gating. Login to comment 203 ABCC7 p.Gly551Asp Besides &#e044;NBD2-CFTR, our latest studies (Lin et al., 2014) also indicate that the pathogenic mutation G551D Figure 6.ߓ NO3 &#e032; enhances the activity of CFTR mutants with defective gating. Login to comment 209 ABCC7 p.Gly551Asp (C) Potentiation of G551D-CFTR gating by NO3 &#e032; . Login to comment 230 ABCC7 p.Gly551Asp The error bars represent the SEM of the mean. Figure 8.ߓ NO3 &#e032; and VX-770 potentiate &#e044;NBD2- and G551D-CFTR in an independent manner. Login to comment 237 ABCC7 p.Gly551Asp (B) Independent potentiation of G551D-CFTR by NO3 &#e032; and VX-770. Login to comment 238 ABCC7 p.Gly551Asp The current trace in the inset illustrates the results of G551D-CFTR channels under the same experimental protocol shown in A. Login to comment 246 ABCC7 p.Gly551Asp Similar experimental protocols were executed for G551D-CFTR (Fig. 8 B). Login to comment 247 ABCC7 p.Gly551Asp It is interesting to note that for both &#e044;NBD2- and G551D-CFTR, the fold increase of the Po by VX-770 is practically the same, regardless of whether the bath anion is Cl&#e032; or NO3 &#e032; . Login to comment 258 ABCC7 p.Gly551Asp However, because of the extremely low Po, the &#e044;NBD2- and G551D-CFTR constructs can serve as a convenient tool. Login to comment 272 ABCC7 p.Arg352Cys Lately, by studying single-channel gating events of a CFTR mutant, R352C/Q, which exhibits unequivocal hydrolysis-dependent transitions of two distinct open states, Jih et al. (2012a) proposed an energetic coupling model featuring a more relaxed relationship between ATP hydrolysis in NBDs and opening/closing of the gate in CFTR`s TMDs. Login to comment 273 ABCC7 p.Gly551Asp Although one cannot exclude the possibility that the new coupling mechanism has a more limited applicability, this gating model explicitly incorporates gating transitions occurring in the absence of ATP into the overall gating scheme, hence allowing interpretations of kinetic data obtained from studies on CFTR mutants with defective ATP-dependent gating such as G551D- and &#e044;NBD2-CFTR (Jih and Hwang, 2012; Lin et al., 2014). Login to comment 278 ABCC7 p.Gly551Asp Perhaps most interestingly, in mutant channels with defective NBDs (i.e., G551D- and &#e044;NBD2-CFTR), nitrate and VX-770 seem to only differ quantitatively, but not qualitatively (Fig. 8). Login to comment 318 ABCC7 p.Gly551Asp Because our intention is to elaborate the experimental results shown in Fig. 8 with &#e044;NBD2- and G551D-CFTR, in this simplified scheme, a closed state (left) and an open state (right) are portrayed as in equilibrium. Login to comment 373 ABCC7 p.Gly551Asp The remarkable success in the clinical application of VX-770 for cystic fibrosis patients carrying the G551D mutation not only has benefited a subset of the overall patient population, but the fact that VX-770 rectifies the gating defect seen in the most common disease-associated mutation &#e044;F508 (Kopeikin et al., 2014) also sets the stage for its role in the therapeutics of a majority of cystic fibrosis patients. Login to comment