ABCMdb

ABCC7 p.Lys95Asp

Predicted by SNAP2:	A: D (75%), C: D (75%), D: D (91%), E: D (85%), F: D (85%), G: D (85%), H: D (53%), I: D (80%), L: D (80%), M: D (75%), N: D (80%), P: D (91%), Q: D (75%), R: N (66%), S: D (63%), T: D (80%), V: D (80%), W: D (91%), Y: D (71%),
Predicted by PROVEAN:	A: N, C: D, D: N, E: N, F: D, G: D, H: N, I: D, L: D, M: N, N: N, P: N, Q: N, R: N, S: N, T: N, V: N, W: D, Y: D,

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[hide] Insight in eukaryotic ABC transporter function by ... FEBS Lett. 2006 Feb 13;580(4):1064-84. Epub 2006 Jan 19. Frelet A, Klein M
Insight in eukaryotic ABC transporter function by mutation analysis.
FEBS Lett. 2006 Feb 13;580(4):1064-84. Epub 2006 Jan 19., 2006-02-13 [PMID:16442101]

Abstract [show]
With regard to structure-function relations of ATP-binding cassette (ABC) transporters several intriguing questions are in the spotlight of active research: Why do functional ABC transporters possess two ATP binding and hydrolysis domains together with two ABC signatures and to what extent are the individual nucleotide-binding domains independent or interacting? Where is the substrate-binding site and how is ATP hydrolysis functionally coupled to the transport process itself? Although much progress has been made in the elucidation of the three-dimensional structures of ABC transporters in the last years by several crystallographic studies including novel models for the nucleotide hydrolysis and translocation catalysis, site-directed mutagenesis as well as the identification of natural mutations is still a major tool to evaluate effects of individual amino acids on the overall function of ABC transporters. Apart from alterations in characteristic sequence such as Walker A, Walker B and the ABC signature other parts of ABC proteins were subject to detailed mutagenesis studies including the substrate-binding site or the regulatory domain of CFTR. In this review, we will give a detailed overview of the mutation analysis reported for selected ABC transporters of the ABCB and ABCC subfamilies, namely HsCFTR/ABCC7, HsSUR/ABCC8,9, HsMRP1/ABCC1, HsMRP2/ABCC2, ScYCF1 and P-glycoprotein (Pgp)/MDR1/ABCB1 and their effects on the function of each protein.

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366 K95D altered the whole cell anion permeability sequence by converting CFTR from a low to a high iodide permeability pore [18]. Login to comment

[hide] ATP hydrolysis-coupled gating of CFTR chloride cha... Biochemistry. 2001 May 15;40(19):5579-86. Zou X, Hwang TC
ATP hydrolysis-coupled gating of CFTR chloride channels: structure and function.
Biochemistry. 2001 May 15;40(19):5579-86., 2001-05-15 [PMID:11341822]

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56 For instance, replacing two positively charged residues with negatively charged residues in the M1 and M2 R-helices of MSD (K95D and K335E) alters the anion selectivity sequence of CFTR (17). Login to comment

[hide] Structure and function of the CFTR chloride channe... Physiol Rev. 1999 Jan;79(1 Suppl):S23-45. Sheppard DN, Welsh MJ
Structure and function of the CFTR chloride channel.
Physiol Rev. 1999 Jan;79(1 Suppl):S23-45., [PMID:9922375]

Abstract [show]
Structure and Function of the CFTR Chloride Channel. Physiol. Rev. 79, Suppl.: S23-S45, 1999. - The cystic fibrosis transmembrane conductance regulator (CFTR) is a unique member of the ABC transporter family that forms a novel Cl- channel. It is located predominantly in the apical membrane of epithelia where it mediates transepithelial salt and liquid movement. Dysfunction of CFTR causes the genetic disease cystic fibrosis. The CFTR is composed of five domains: two membrane-spanning domains (MSDs), two nucleotide-binding domains (NBDs), and a regulatory (R) domain. Here we review the structure and function of this unique channel, with a focus on how the various domains contribute to channel function. The MSDs form the channel pore, phosphorylation of the R domain determines channel activity, and ATP hydrolysis by the NBDs controls channel gating. Current knowledge of CFTR structure and function may help us understand better its mechanism of action, its role in electrolyte transport, its dysfunction in cystic fibrosis, and its relationship to other ABC transporters.

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102 This would suggest that like acidic residues (K95D and K335E) altered the whole cell other Cl0 channels, including ligand-gated Cl0 channels in anion permeability sequence by converting CFTR from a neurons (20) and outwardly rectifying Cl0 channels in low I0 permeability pore (Br0 ' Cl0 ú I0 ) to a high I0 epithelia (55), the CFTR pore has a ''weak field strength`` permeability pore (I0 ú Br0 ú Cl0 ) (4). Login to comment

[hide] CFTR: mechanism of anion conduction. Physiol Rev. 1999 Jan;79(1 Suppl):S47-75. Dawson DC, Smith SS, Mansoura MK
CFTR: mechanism of anion conduction.
Physiol Rev. 1999 Jan;79(1 Suppl):S47-75., [PMID:9922376]

Abstract [show]
CFTR: Mechanism of Anion Conduction. Physiol. Rev. 79, Suppl.: S47-S75, 1999. - The purpose of this review is to collect together the results of recent investigations of anion conductance by the cystic fibrosis transmembrane conductance regulator along with some of the basic background that is a prerequisite for developing some physical picture of the conduction process. The review begins with an introduction to the concepts of permeability and conductance and the Nernst-Planck and rate theory models that are used to interpret these parameters. Some of the physical forces that impinge on anion conductance are considered in the context of permeability selectivity and anion binding to proteins. Probes of the conduction process are considered, particularly permeant anions that bind tightly within the pore and block anion flow. Finally, structure-function studies are reviewed in the context of some predictions for the origin of pore properties.

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431 The substitutions examined were K95D 101) or 1.0-2.0 (59, 145, 146). Login to comment
434 Finkelstein and Cass (55) called attention to the factthe order of 1:10, but two of the substitutions (K95D and K335E) altered the sequence of relative anion permeabilit- that the electrical behavior of planar lipid membranes bathed by iodide-containing solutions may be strongly in-ies by increasing the ratio for iodide, PI/PCl . Login to comment
584 This substitu- K95, to aspartic acid (K95D) increased PI/PCl (6). Login to comment

[hide] CFTR! Am J Physiol. 1992 Aug;263(2 Pt 1):C267-86. Fuller CM, Benos DJ
CFTR!
Am J Physiol. 1992 Aug;263(2 Pt 1):C267-86., [PMID:1381146]

Abstract [show]
Cystic fibrosis (CF) is a fatal genetic disease primarily affecting Caucasians, although cases have been reported from other ethnic groups. CF has a complex etiology, but it is chiefly a disease of electrolyte transport and is characterized by defects in fluid secretion by several epithelia, including the sweat duct, exocrine pancreas, and the pulmonary airways. The link between CF and a defect in cAMP-mediated Cl- transport in secretory epithelia was established in the early 1980s. Since then, numerous electrophysiological studies have focused on the characterization and regulation of individual Cl- channels underlying the macroscopic Cl- currents of secretory epithelia in the airways, sweat ducts, and gut. In this review the results of these studies in the light of current knowledge of the function of the CF gene product, the CF transmembrane conductance regulator (CFTR) protein, will be analyzed. The CFTR protein is a member of a family of ATP-binding proteins that act as unidirectional solute pumps. These proteins are membrane spanning, are found in both prokaryotic and eukaryotic cells, and have two ATP-binding domains. The family includes the p-glycoproteins that are involved with the expression of multidrug resistance in certain tumor cells. The majority of CF chromosomes (70%) have a single codon deletion that translates to a missing phenylalanine residue at position 508 (delta F508) of the protein. Unique for this family of proteins, the CFTR protein possesses an additional highly charged domain (the R domain) containing several consensus polypeptide sequences for kinase phosphorylation. Although CFTR bears structural resemblance to this family of ATP-dependent pumps, overexpression of the protein in a variety of different cell types is associated with the appearence of a cAMP-sensitive Cl- channel. We critically examine current information concerning the structure-function relationships of the CFTR protein obtained from both electrophysiological and biochemical approaches. We also summarize recent evidence suggesting that the CFTR protein may act as a pump and a channel, a hypothesis in keeping with the multifaceted nature of the disease.

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222 Overexpression of CFTR bearing either a K95D mutation in TM1 or a K335D mutation in TM6 in HeLa cells resulted in a shift in ion selectivity of the CAMP- l Amino acid changes corresponding to mutations in the CF gene are given in single letter code, with the changed residue followed by residue position and the substituted amino acid. Login to comment

[hide] Characterization of mutations located in exon 18 o... FEBS Lett. 1998 Oct 16;437(1-2):1-4. Vankeerberghen A, Wei L, Teng H, Jaspers M, Cassiman JJ, Nilius B, Cuppens H
Characterization of mutations located in exon 18 of the CFTR gene.
FEBS Lett. 1998 Oct 16;437(1-2):1-4., [PMID:9804160]

Abstract [show]
In order to get a better insight into the function of amino acid residues located in the second transmembrane domain of the cystic fibrosis transmembrane conductance regulator (CFTR) protein, all exon 18 mutations found in cystic fibrosis (CF) patients were characterized at the protein and at the electrophysiological level. Of the different mutations present in transmembrane helix 12 (M1137V, M1137R, I11139V and deltaM1140), and the intracytoplasmic loop connecting TM12 and NBD2 (D1152H and D1154G), only M1137R interfered with the proper maturation of the protein. Permeability studies performed after injection of the different wild-type and mutant cRNAs in Xenopus laevis oocytes indicated that the mutations did not alter the permeability sequence of the CFTR channels. The whole cell cAMP activated chloride currents, however, were significantly reduced for M1137V, I1139V, D1152H and D1154G and close to zero for deltaM1140, indicating that these mutations interfere with the proper gating of the chloride channels.

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15 The anion selectivity 'lter itself seems to be formed by the transmembrane helices [11], since mutagenesis of lysine 95 to aspartate and of lysine 335 to glutamate changed the anion selectivity of the channel. Login to comment

[hide] Topological model of membrane domain of the cystic... J Mol Graph Model. 1998 Apr;16(2):72-82, 97-8. Gallet X, Festy F, Ducarme P, Brasseur R, Thomas-Soumarmon A
Topological model of membrane domain of the cystic fibrosis transmembrane conductance regulator.
J Mol Graph Model. 1998 Apr;16(2):72-82, 97-8., [PMID:9879057]

Abstract [show]
The cystic fibrosis transmembrane conductance regulator is a cAMP-regulated chloride channel. We used molecular modelling to predict 3-D models for the CFTR membrane domain. Hydropathy and residue conservation in all CFTRs as well as in other proteins suggested that the membrane domain is a 12-helix bundle. If the domain is enclosing a channel for chloride, it could be made of five helices. We propose two structural models in which both lumenal and cytoplasmic entrances to the chloride pore have a ring of positively charged residues. The inner surface of the channel is covered with neutral polar plus one or two charged residues. Helices that are not directly involved in the chloride channel could organise to form a second channel; a dimeric symmetrical structure is proposed. Analysis raised interest for helix 5: this hydrophobic fragment is conserved in all CFTRs and aligns with segments present in several different ion channels and transporters. The existence of an FFXXFFXXF motif is proposed. Helix 5 could be an important domain of CFTRs. The models agree with available data from pathological mutations but does not account for the membrane insertion of a hydrophilic fragment of NBDI.

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232 Mutations associated with mild forms of cystic fibrosis (R117H, R334W, and R347P) implicate three of our inner pore residues in the chloride conductance.50 In other studies, basic amino acids of membrane helices were replaced by acidic residues (K95D, K335E, R347E, and R1030E). Login to comment
236 Mutations associated with mild forms of cystic fibrosis (R117H, R334W, and R347P) implicate three of our inner pore residues in the chloride conductance.50 In other studies, basic amino acids of membrane helices were replaced by acidic residues (K95D, K335E, R347E, and R1030E). Login to comment

[hide] Cystic fibrosis transmembrane conductance regulato... Biophys J. 1998 Mar;74(3):1320-32. Mansoura MK, Smith SS, Choi AD, Richards NW, Strong TV, Drumm ML, Collins FS, Dawson DC
Cystic fibrosis transmembrane conductance regulator (CFTR) anion binding as a probe of the pore.
Biophys J. 1998 Mar;74(3):1320-32., [PMID:9512029]

Abstract [show]
We compared the effects of mutations in transmembrane segments (TMs) TM1, TM5, and TM6 on the conduction and activation properties of the cystic fibrosis transmembrane conductance regulator (CFTR) to determine which functional property was most sensitive to mutations and, thereby, to develop a criterion for measuring the importance of a particular residue or TM for anion conduction or activation. Anion substitution studies provided strong evidence for the binding of permeant anions in the pore. Anion binding was highly sensitive to point mutations in TM5 and TM6. Permeability ratios, in contrast, were relatively unaffected by the same mutations, so that anion binding emerged as the conduction property most sensitive to structural changes in CFTR. The relative insensitivity of permeability ratios to CFTR mutations was in accord with the notion that anion-water interactions are important determinants of permeability selectivity. By the criterion of anion binding, TM5 and TM6 were judged to be likely to contribute to the structure of the anion-selective pore, whereas TM1 was judged to be less important. Mutations in TM5 and TM6 also dramatically reduced the sensitivity of CFTR to activation by 3-isobutyl 1-methyl xanthine (IBMX), as expected if these TMs are intimately involved in the physical process that opens and closes the channel.

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11 Substitution of an aspartic acid for K95 (K95D) in TM1 altered anion selectivity (Anderson et al., 1991), and three cysteine-substituted residues in this TM (G91, K95, and Q98) were identified as being accessible to water-soluble, charged, sulfhydryl-specific reagents (Akabas et al., 1994), but a CFTR construct in which the first 118 amino acids, including those that constitute TM1, were deleted produced channels with conduction properties similar to wild type (Carroll et al., 1995). Login to comment

[hide] Probing the structural and functional domains of t... J Bioenerg Biomembr. 1997 Oct;29(5):453-63. Akabas MH, Cheung M, Guinamard R
Probing the structural and functional domains of the CFTR chloride channel.
J Bioenerg Biomembr. 1997 Oct;29(5):453-63., [PMID:9511930]

Abstract [show]
The cystic fibrosis transmembrane conductance regulator (CFTR) forms an anion-selective channel involved in epithelial chloride transport. Recent studies have provided new insights into the structural determinants of the channel's functional properties, such as anion selectivity, single-channel conductance, and gating. Using the scanning-cysteine-accessibility method we identified 7 residues in the M1 membrane-spanning segment and 11 residues in and flanking the M6 segment that are exposed on the water-accessible surface of the protein; many of these residues may line the ion-conducting pathway. The pattern of the accessible residues suggests that these segments have a largely alpha-helical secondary structure with one face exposed in the channel lumen. Our results suggest that the residues at the cytoplasmic end of the M6 segment loop back into the channel, narrowing the lumen, and thereby forming both the major resistance to ion movement and the charge-selectivity filter.

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140 The mutations K95D and K335E altered the halide permeability sequence, leading to the suggestion that these residues might be involved in anion binding (Anderson et al., 1991b). Login to comment

[hide] Halide permeation in wild-type and mutant cystic f... J Gen Physiol. 1997 Oct;110(4):341-54. Tabcharani JA, Linsdell P, Hanrahan JW
Halide permeation in wild-type and mutant cystic fibrosis transmembrane conductance regulator chloride channels.
J Gen Physiol. 1997 Oct;110(4):341-54., [PMID:9379167]

Abstract [show]
Permeation of cystic fibrosis transmembrane conductance regulator (CFTR) Cl channels by halide ions was studied in stably transfected Chinese hamster ovary cells by using the patch clamp technique. In cell-attached patches with a high Cl pipette solution, the CFTR channel displayed outwardly rectifying currents and had a conductance near the membrane potential of 6.0 pS at 22 degrees C or 8.7 pS at 37 degrees C. The current-voltage relationship became linear when patches were excised into symmetrical, -tris(hydroxymethyl)methyl-2-aminomethane sulfonate (TES)-buffered solutions. Under these conditions, conductance increased from 7.0 pS at 22 degrees C to 10.9 pS at 37 degrees C. The conductance at 22 degrees C was approximately 1.0 pS higher when TES and HEPES were omitted from the solution, suggesting weak, voltage-independent block by pH buffers. The relationship between conductance and Cl activity was hyperbolic and well fitted by a Michaelis-Menten-type function having a of approximately 38 mM and maximum conductance of 10 pS at 22 degrees C. Dilution potentials measured with NaCl gradients indicated high anion selectivity (P/P = 0.003-0.028). Biionic reversal potentials measured immediately after exposure of the cytoplasmic side to various test anions indicated P(1.8) > P(1. 3) > P(1.0) > P(0.17), consistent with a "weak field strength" selectivity site. The same sequence was obtained for external halides, although inward F flow was not observed. Iodide currents were protocol dependent and became blocked after 1-2 min. This coincided with a large shift in the (extrapolated) reversal potential to values indicating a greatly reduced I/Cl permeability ratio (P/P< 0.4). The switch to low I permeability was enhanced at potentials that favored Cl entry into the pore and was not observed in the R347D mutant, which is thought to lack an anion binding site involved in multi-ion pore behavior. Interactions between Cl and I ions may influence I permeation and be responsible for the wide range of P/P ratios that have been reported for the CFTR channel. The low P/P ratio usually reported for CFTR only occurred after entry into an altered permeability state and thus may not be comparable with permeability ratios for other anions, which are obtained in the absence of iodide. We propose that CFTR displays a "weak field strength" anion selectivity sequence.

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277 Halide selectivity in CFTR cannot be attributed exclusively to the region around arg347; however, because high PI/PCl ratios have been reported previously for other pore mutants (K95D and K335E; Anderson et al., 1991), and because R347D retains some preference for Br- over Cl- and selects strongly against F- (our unpublished observations). Login to comment
305 Halide selectivity in CFTR cannot be attributed exclusively to the region around arg347; however, because high PI/PCl ratios have been reported previously for other pore mutants (K95D and K335E; Anderson et al., 1991), and because R347D retains some preference for Br2 over Cl2 and selects strongly against F2 (our unpublished observations). Login to comment

[hide] Locating the anion-selectivity filter of the cysti... J Gen Physiol. 1997 Mar;109(3):289-99. Cheung M, Akabas MH
Locating the anion-selectivity filter of the cystic fibrosis transmembrane conductance regulator (CFTR) chloride channel.
J Gen Physiol. 1997 Mar;109(3):289-99., [PMID:9089437]

Abstract [show]
The cystic fibrosis transmembrane conductance regulator forms an anion-selective channel; the site and mechanism of charge selectivity is unknown. We previously reported that cysteines substituted, one at a time, for Ile331, Leu333, Arg334, Lys335, Phe337, Ser341, Ile344, Arg347, Thr351, Arg352, and Gln353, in and flanking the sixth membrane-spanning segment (M6), reacted with charged, sulfhydryl-specific, methanethiosulfonate (MTS) reagents. We inferred that these residues are on the water-accessible surface of the protein and may line the ion channel. We have now measured the voltage-dependence of the reaction rates of the MTS reagents with the accessible, engineering cysteines. By comparing the reaction rates of negatively and positively charged MTS reagents with these cysteines, we measured the extent of anion selectivity from the extracellular end of the channel to eight of the accessible residues. We show that the major site determining anion vs. cation selectivity is near the cytoplasmic end of the channel; it favors anions by approximately 25-fold and may involve the residues Arg347 and Arg 352. From the voltage dependence of the reaction rates, we calculated the electrical distance to the accessible residues. For the residues from Leu333 to Ser341 the electrical distance is not significantly different than zero; it is significantly different than zero for the residues Thr351 to Gln353. The maximum electrical distance measured was 0.6 suggesting that the channel extends more cytoplasmically and may include residues flanking the cytoplasmic end of the M6 segment. Furthermore, the electrical distance calculations indicate that R352C is closer to the extracellular end of the channel than either of the adjacent residues. We speculate that the cytoplasmic end of the M6 segment may loop back into the channel narrowing the lumen and thereby forming both the major resistance to current flow and the anion-selectivity filter.

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204 Based on the effects of the mutations K95D and K335E on halide selectivity sequences, Anderson et al. (1991b) concluded that Lys95 and Lys335 were determinants of halide selectivity. Login to comment

[hide] Mutations in the putative pore-forming domain of C... FEBS Lett. 1995 Nov 6;374(3):312-6. Hipper A, Mall M, Greger R, Kunzelmann K
Mutations in the putative pore-forming domain of CFTR do not change anion selectivity of the cAMP activated Cl- conductance.
FEBS Lett. 1995 Nov 6;374(3):312-6., [PMID:7589561]

Abstract [show]
Cystic fibrosis transmembrane conductance regulator (CFTR) apparently forms Cl- channels in apical membranes of secretory epithelial cells. A detailed model describes molecular structure and biophysical properties of CFTR and the impact of various mutations as they occur in cystic fibrosis. In the present report mutations were introduced into the putative 6th alpha-helical transmembrane pore forming domain of CFTR. The mutants were subsequently expressed in Xenopus oocytes by injection of the respective cRNAs. Whole cell (wc) conductances could be reversibly activated by IBMX (1 nmol/l) only in oocytes injected with wild-type (wt) or mutant CFTR but not in oocytes injected with water or antisense CFTR. The activated conductance was partially inhibited by (each 100 mumol/l) DIDS (27%) and glibenclamide (77%), but not by 10 mumol/l NPPB. The following mutations were examined: K335E, R347E, R334E, K335H, R347H, R334H. They did not measurably change the wt-CFTR anion permeability (P) and we conductance (G) sequence of: PCl- > PBr- > P1- and GCl- > GBr- > G1-, respectively. Moreover, anomalous mole fraction behavior for the cAMP activated current could not be detected: neither in wt-CFTR nor in R347E-CFTR. Various mutants for which positively charged amino acids were replaced by histidines (K335H, R347H, R334H) did not show pH sensitivity of the IBMX activated wc conductance. We, therefore, cannot confirm previous results. CFTR might have a different molecular structure than previously suggested or it might act as a regulator of ion conductances.

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105 In fact, in a previous study lysine and arginine were replaced by negatively charged amino acids in the first and sixth transmembrane domain (K95D, K335E, R347E), respectively [1]. Login to comment

[hide] The CFTR chloride channel of mammalian heart. Annu Rev Physiol. 1995;57:387-416. Gadsby DC, Nagel G, Hwang TC
The CFTR chloride channel of mammalian heart.
Annu Rev Physiol. 1995;57:387-416., [PMID:7539989]

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18 For example, expression in 3T3 cells of two CFTR mutants, K95D and K335E, in which negatively charged amino acids replaced positively charged lysines in the first (Ml) and sixth (M6) putative transmembrane a-helices (Figure I) yielded Cl- channels with altered anion permeability sequences, 1- > B..- > Cl- instead of the normal Br > CI- > 1- (3). Login to comment

[hide] Amino acid residues lining the chloride channel of... J Biol Chem. 1994 May 27;269(21):14865-8. Akabas MH, Kaufmann C, Cook TA, Archdeacon P
Amino acid residues lining the chloride channel of the cystic fibrosis transmembrane conductance regulator.
J Biol Chem. 1994 May 27;269(21):14865-8., [PMID:7515047]

Abstract [show]
The cystic fibrosis transmembrane conductance regulator forms a chloride channel that is regulated by phosphorylation and intracellular ATP levels. The structure of the channel-forming domains is undetermined. To identify the residues lining this channel we substituted cysteine, one at a time, for 9 consecutive residues (91-99) in the M1 membrane-spanning segment. The cysteine substitution mutants were expressed in Xenopus oocytes. We determined the accessibility of the engineered cysteine to charged, sulfhydryl-specific methanethiosulfonate reagents added extracellularly. We assume that, among residues in membrane-spanning segments, only those lining the channel will be accessible to react with these hydrophilic reagents and that such a reaction would irreversibly alter conduction through the channel. Only the cysteines substituted for Gly-91, Lys-95, and Gln-98 were accessible to the reagents. We conclude that these residues are in the channel lining. The periodicity of these residues is consistent with an alpha-helical secondary structure.

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15 Mutation of Lys-95 to Asp, in M1, and Lys-335 and Arg-347 to Glu, in M6, altered the permeability andlor conductance ratios for halides (6). Login to comment
123 Effects on single-channel properties have been observed with other missense mutations associated with mild disease (11).Mutation of Lys-95 to Asp altered the relative anionper- meability sequence of the channel, although no evidence was presented that Lys-95 actually faced the channel lumen (6). Login to comment

[hide] Chloride channels in the apical membrane of normal... Am J Physiol. 1992 Jul;263(1 Pt 1):L1-14. Anderson MP, Sheppard DN, Berger HA, Welsh MJ
Chloride channels in the apical membrane of normal and cystic fibrosis airway and intestinal epithelia.
Am J Physiol. 1992 Jul;263(1 Pt 1):L1-14., [PMID:1322048]

Abstract [show]
Cl- channels located in the apical membrane of secretory epithelia play a key role in epithelial fluid and electrolyte transport. Dysfunction of one of these channels, cystic fibrosis transmembrane conductance regulator (CFTR), causes the genetic disease cystic fibrosis (CF). We review here the properties and regulation of the different types of Cl- channels that have been reported in airway and intestinal epithelia. We begin by describing the properties of the CFTR Cl- channel and then use those properties as a point of reference. We focused particularly on the evidence that localizes specific types of Cl- channel to the apical membrane. With that background, we assess the biological function of various Cl- channels in airway and intestinal epithelia.

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69 Relative anion permeability of CAMP-regulated channels in apical membrane and in cells expressing wild-type and mutant CFTR PXlPCl- Gx/Gcl- Br- ClI- Br ClI- CAMP 3T3 fibroblasts CFTR 1.11 1.00 0.59 1.26 1.00 0.29 HeLa cells CFTR 1.24 1.00 0.57 1.02 1.00 0.39 K95D 1.25 1.00 1.43 1.39 1.00 0.75 K335E 1.06 1.00 1.37 1.71 1.00 1.43 R347E 1.24 1.00 0.90 1.46 1.00 0.47 Rl030E 1.46 1.00 0.81 1.50 1.00 0.28 Human airway epithelia Apical ND 1.00 0.41 ND 1.00 0.35 T84 epithelia Apical 1.21 1.00 0.56 0.92 1.00 0.47 over cations. Login to comment

[hide] The biochemical defect in cystic fibrosis. J R Soc Med. 1992;85 Suppl 19:2-5. Cuthbert AW
The biochemical defect in cystic fibrosis.
J R Soc Med. 1992;85 Suppl 19:2-5., [PMID:1375960]

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70 Changing lysine 95 to aspartic acid and lysine 335 to glutamic acid alters the selectivity of the chloride conductance fiom chloride>iodide to iodide>chloride When the R-domain was deleted the CFTR chloride conductance was increased in the unstimulated state (ie absence ofcAMP) suggesting that the R-domain is involved in thegatingofthe ion channeL A similar mechanism has beenproposedfor the gating ofpotassium channels. Login to comment

[hide] Cystic fibrosis transmembrane conductance regulato... Neuron. 1992 May;8(5):821-9. Welsh MJ, Anderson MP, Rich DP, Berger HA, Denning GM, Ostedgaard LS, Sheppard DN, Cheng SH, Gregory RJ, Smith AE
Cystic fibrosis transmembrane conductance regulator: a chloride channel with novel regulation.
Neuron. 1992 May;8(5):821-9., [PMID:1375035]

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87 Yet two mutations, K95D and K335E, each altered anion selectivity. Login to comment
89 Thus K95D means that lysine residue 95 was changed to aspartate.) Login to comment