51
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Travis S, Carson M, Ries D, Welsh M. Interaction of nucleotides with membrane-associated cystic fibrosis transmembrane conductance regulator. J Biol Chem 1993. [DOI: 10.1016/s0021-9258(18)82259-1] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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52
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Venglarik CJ, Singh AK, Wang R, Bridges RJ. Trinitrophenyl-ATP blocks colonic Cl- channels in planar phospholipid bilayers. Evidence for two nucleotide binding sites. J Gen Physiol 1993; 101:545-69. [PMID: 8389396 PMCID: PMC2216774 DOI: 10.1085/jgp.101.4.545] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Outwardly rectifying 30-50-pS Cl- channels mediate cell volume regulation and transepithelial transport. Several recent reports indicate that rectifying Cl- channels are blocked after addition of ATP to the extracellular bath (Alton, E. W. F. W., S. D. Manning, P. J. Schlatter, D. M. Geddes, and A. J. Williams. 1991. Journal of Physiology. 443:137-159; Paulmichl, M., Y. Li, K. Wickman, M. Ackerman, E. Peralta, and D. Clapham. 1992. Nature. 356:238-241). Therefore, we decided to conduct a more detailed study of the ATP binding site using a higher affinity probe. We tested the ATP derivative, 2',3',O-(2,4,6-trinitrocyclohexadienylidene) adenosine 5'-triphosphate (TNP-ATP), which has a high affinity for certain nucleotide binding sites. Here we report that TNP-ATP blocked colonic Cl- channels when added to either bath and that blockade was consistent with the closed-open-blocked kinetic model. The TNP-ATP concentration required for a 50% decrease in open probability was 0.27 microM from the extracellular (cis) side and 20 microM from the cytoplasmic (trans) side. Comparison of the off rate constants revealed that TNP-ATP remained bound 28 times longer when added to the extracellular side compared with the cytoplasmic side. We performed competition studies to determine if TNP-ATP binds to the same sites as ATP. Addition of ATP to the same bath containing TNP-ATP reduced channel amplitude and increased the time the channel spent in the open and fast-blocked states (i.e., burst duration). This is the result expected if TNP-ATP and ATP compete for block, presumably by binding to common sites. In contrast, addition of ATP to the bath opposite to the side containing TNP-ATP reduced amplitude but did not alter burst duration. This is the result expected if opposite-sided TNP-ATP and ATP bind to different sites. In summary, we have identified an ATP derivative that has a nearly 10-fold higher affinity for reconstituted rectifying colonic Cl- channels than any previously reported blocker (Singh, A. K., G. B. Afink, C. J. Venglarik, R. Wang, and R. J. Bridges. 1991. American Journal of Physiology. 260 [Cell Physiology. 30]:C51-C63). Thus, TNP-ATP should be useful in future studies of ion channel nucleotide binding sites and possibly in preliminary steps of ion channel protein purification. In addition, we have obtained good evidence that there are at least two nucleotide binding sites located on opposite sides of the colonic Cl- channel and that occupancy of either site produces a blocked state.
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Affiliation(s)
- C J Venglarik
- Department of Physiology and Biophysics, University of Alabama, Birmingham
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53
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Thomas PJ, Pedersen PL. Effects of the delta F508 mutation on the structure, function, and folding of the first nucleotide-binding domain of CFTR. J Bioenerg Biomembr 1993; 25:11-9. [PMID: 7680027 DOI: 10.1007/bf00768063] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The fatal autosomal recessive disease cystic fibrosis (CF) is caused by mutations in the gene which encodes the cystic fibrosis transmembrane conductance regulator (CFTR). Many of these disease-causing mutations, including the deletion of F508 (delta F508) which accounts for approximately 70% of the disease alleles, occur in one of the two consensus nucleotide binding sequences. Peptide studies have directly demonstrated that the N-terminal nucleotide binding sequences bind adenine nucleotides. Structurally, circular dichroism spectropolarimetry indicates that this region of CFTR assumes a beta-stranded structure in solution. The delta F508 mutation causes a diminution in the amount of beta-stranded structure and a concomitant increase in the amount of random coil structure present, indicating that either the mutant peptide has a different native structure or that the conformational equilibrium is shifted toward a more disordered form. Furthermore, the mutant peptide is more sensitive to denaturation, indicating that delta F508 is a stability, or protein-folding mutant. Here we review these results and discuss their implications for interpreting the behavior of delta F508 in situ and for the rational design of new CF drugs.
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Affiliation(s)
- P J Thomas
- Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
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54
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Quinton PM, Reddy MM. Control of CFTR chloride conductance by ATP levels through non-hydrolytic binding. Nature 1992; 360:79-81. [PMID: 1279436 DOI: 10.1038/360079a0] [Citation(s) in RCA: 143] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Site-specific mutation and membrane reconstitution experiments provide compelling evidence that the product of the gene which is at fault in the disease cystic fibrosis, termed the cystic fibrosis transmembrane conductance regulator (CFTR), is a small-conductance chloride channel activated by phosphorylation. As transport of chloride ions is passive, the predicted presence of two nucleotide-binding domains in CFTR seems as puzzling as a report that ATP hydrolysis is essential to activate the channel. We now find that in the sweat duct, which expresses high levels of CFTR and has a very high Cl- conductance, intracellular concentrations of ATP must be about normal (5 mM) for activation of this conductance, apparently by a non-hydrolytic, perhaps allosteric, mechanism. This passive dependence on ATP should mean that even a modest depletion of cell energy levels will significantly lower the energy demands of electrolyte transport by decreasing chloride conductance. We believe this direct coupling between cellular ATP levels and chloride channel activity is an adaptive mechanism to protect the tissue from damage resulting from excessive energy depletion.
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Affiliation(s)
- P M Quinton
- Division of Biomedical Sciences, University of California, Riverside 92521
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55
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Thomas PJ, Ko YH, Pedersen PL. Altered protein folding may be the molecular basis of most cases of cystic fibrosis. FEBS Lett 1992; 312:7-9. [PMID: 1385213 DOI: 10.1016/0014-5793(92)81399-7] [Citation(s) in RCA: 57] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Experiments have demonstrated that the cystic fibrosis transmembrane conductance regulator protein (CFTR), containing the most common cystic fibrosis (CF)-causing mutation (delta F508), reaches the plasma membrane in reduced amounts. Studies of a peptide model of CFTR indicate that the delta F508 mutated region is more sensitive to denaturating conditions. This paper proposes that altered protein folding accounts for these findings, and, thus, most cases of CF. Significantly, the hypothesis makes specific predictions about the effect of stabilizing conditions on mutant CFTR, and, further, suggests a new class of pharmaceuticals that may prove effective in the treatment of this important genetic disease.
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Affiliation(s)
- P J Thomas
- Department of Biological Chemistry, Johns Hopkins University, School of Medicine, Baltimore, MD 21205
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56
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Thomas P, Garboczi D, Pedersen P. Mutational analysis of the consensus nucleotide binding sequences in the rat liver mitochondrial ATP synthase beta-subunit. J Biol Chem 1992. [DOI: 10.1016/s0021-9258(19)88706-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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57
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Anderson MP, Welsh MJ. Regulation by ATP and ADP of CFTR chloride channels that contain mutant nucleotide-binding domains. Science 1992; 257:1701-4. [PMID: 1382316 DOI: 10.1126/science.1382316] [Citation(s) in RCA: 183] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Regulation of the cystic fibrosis transmembrane conductance regulator (CFTR) chloride channel is unusual in that phosphorylated channels require cytosolic adenosine triphosphate (ATP) to open. The CFTR contains two regions predicted to be nucleotide-binding domains (NBDs); site-directed mutations in each NBD have now been shown to alter the relation between ATP concentration and channel activity, which indicates that ATP stimulates the channel by direct interaction with both NBDs. The two NBDs are not, however, functionally equivalent: adenosine diphosphate (ADP) competitively inhibited the channel by interacting with NBD2 but not by interacting with NBD1. Four cystic fibrosis-associated mutations in the NBDs reduced absolute chloride channel activity, and one mutation also decreased the potency with which ATP stimulates channel activity. Dysfunction of ATP-dependent stimulation through the NBDs may be the basis for defective CFTR chloride channel activity in some cystic fibrosis patients.
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Affiliation(s)
- M P Anderson
- Howard Hughes Medical Institute, Department of Internal Medicine, University of Iowa College of Medicine, Iowa City 52242
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58
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Montrose-Rafizadeh C, Blackmon D, Hamosh A, Oliva M, Hawkins A, Curristin S, Griffin C, Yang V, Guggino W, Cutting G. Regulation of cystic fibrosis transmembrane conductance regulator (CFTR) gene transcription and alternative RNA splicing in a model of developing intestinal epithelium. J Biol Chem 1992. [DOI: 10.1016/s0021-9258(18)41774-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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59
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Affiliation(s)
- A O'Rawe
- Nuffield Department of Child Health, Queen's University of Belfast
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60
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Affiliation(s)
- C R Marino
- Department of Medicine, Yale University School of Medicine, New Haven, Connecticut
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61
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Picciotto M, Cohn J, Bertuzzi G, Greengard P, Nairn A. Phosphorylation of the cystic fibrosis transmembrane conductance regulator. J Biol Chem 1992. [DOI: 10.1016/s0021-9258(18)42339-3] [Citation(s) in RCA: 245] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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62
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Arispe N, Rojas E, Hartman J, Sorscher EJ, Pollard HB. Intrinsic anion channel activity of the recombinant first nucleotide binding fold domain of the cystic fibrosis transmembrane regulator protein. Proc Natl Acad Sci U S A 1992; 89:1539-43. [PMID: 1371876 PMCID: PMC48487 DOI: 10.1073/pnas.89.5.1539] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
The first nucleotide binding fold (NBF-1) from the cystic fibrosis transmembrane regulator (CFTR) has been expressed in bacteria and found to bind ATP and to express anion channel activity when reconstituted onto a planar lipid bilayer. This evidence suggests that the NBF forms the anion-selective portion of the CFTR channel. We also found that the recombinant NBF-1 anion channel is blocked by ATP (1 mM), under which condition it appears to have a minimal conductance of approximately 9 pS and an ohmic current-voltage relationship. We further found that the recombinant NBF-1 bearing the delta F508 mutation has nearly identical anion channel activity to that of the wild-type protein but can be distinguished from wild type under bianionic conditions with chloride and gluconate. We conclude from these data that the anion channel activity of the recombinant NBF-1 could represent all or part of the anion conductance mechanism of CFTR and that the role of the ATP binding by the NBF could be to modulate this anion channel activity.
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Affiliation(s)
- N Arispe
- Laboratory of Cell Biology and Genetics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892
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63
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Hartman J, Huang Z, Rado T, Peng S, Jilling T, Muccio D, Sorscher E. Recombinant synthesis, purification, and nucleotide binding characteristics of the first nucleotide binding domain of the cystic fibrosis gene product. J Biol Chem 1992. [DOI: 10.1016/s0021-9258(19)50446-x] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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64
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Thomas P, Shenbagamurthi P, Sondek J, Hullihen J, Pedersen P. The cystic fibrosis transmembrane conductance regulator. Effects of the most common cystic fibrosis-causing mutation on the secondary structure and stability of a synthetic peptide. J Biol Chem 1992. [DOI: 10.1016/s0021-9258(18)42610-5] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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65
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Shimabuku A, Nishimoto T, Ueda K, Komano T. P-glycoprotein. ATP hydrolysis by the N-terminal nucleotide-binding domain. J Biol Chem 1992. [DOI: 10.1016/s0021-9258(18)42834-7] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
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66
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Anderson MP, Berger HA, Rich DP, Gregory RJ, Smith AE, Welsh MJ. Nucleoside triphosphates are required to open the CFTR chloride channel. Cell 1991; 67:775-84. [PMID: 1718606 DOI: 10.1016/0092-8674(91)90072-7] [Citation(s) in RCA: 399] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The CFTR Cl- channel contains two predicted nucleotide-binding domains (NBD1 and NBD2); therefore, we examined the effect of ATP on channel activity. Once phosphorylated by cAMP-dependent protein kinase (PKA), channels required cytosolic ATP to open. Activation occurred by a PKA-independent mechanism. ATP gamma S substituted for ATP in PKA phosphorylation, but it did not open the channel. Several hydrolyzable nucleotides (ATP greater than GTP greater than ITP approximately UTP greater than CTP) reversibly activated phosphorylated channels, but nonhydrolyzable analogs and Mg(2+)-free ATP did not. Studies of CFTR mutants indicated that ATP controls channel activity independent of the R domain and suggested that hydrolysis of ATP by NBD1 may be sufficient for channel opening. The finding that nucleoside triphosphates regulate CFTR begins to explain why CF-associated mutations in the NBDs block Cl- channel function.
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Affiliation(s)
- M P Anderson
- Howard Hughes Medical Institute, Department of Internal Medicine, University of Iowa College of Medicine, Iowa City 52242
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67
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Chastre E, Di Gioia Y, Barbry P, Simon-Bouy B, Mornet E, Fanen P, Champigny G, Emami S, Gespach C. Functional insertion of the SV40 large T oncogene in cystic fibrosis intestinal epithelium. Characterization of CFI-3 cells. J Biol Chem 1991. [DOI: 10.1016/s0021-9258(18)54846-8] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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68
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Bianchet M, Ysern X, Hullihen J, Pedersen P, Amzel L. Mitochondrial ATP synthase. Quaternary structure of the F1 moiety at 3.6 A determined by x-ray diffraction analysis. J Biol Chem 1991. [DOI: 10.1016/s0021-9258(18)54840-7] [Citation(s) in RCA: 107] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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69
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Identification and localization of a dogfish homolog of human cystic fibrosis transmembrane conductance regulator. J Biol Chem 1991. [DOI: 10.1016/s0021-9258(18)54631-7] [Citation(s) in RCA: 61] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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70
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Gibson AL, Wagner LM, Collins FS, Oxender DL. A bacterial system for investigating transport effects of cystic fibrosis--associated mutations. Science 1991; 254:109-11. [PMID: 1718037 DOI: 10.1126/science.1718037] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
LIV-I, a high-affinity system that transports neutral, branched-chain amino acids into Escherichia coli, has two components, LivG and LivF, that are homologous to the cystic fibrosis (CF) transmembrane conductance regulator (CFTR). CF-associated mutations of human CFTR were introduced into corresponding regions of LivG, and their effects on leucine transport could be grouped into three classes. Mutations were found that (i) abolished LIV-I--directed transport, (ii) retained about a quarter of wild-type activity at the Michaelis-Menten constant (KM), and (iii) had minimal activity at the KM. A mutation equivalent to a benign polymorphism had no effect on transport. The correlation of these mutational phenotypes in LivG and CFTR suggests that the LIV-I prokaryotic transporter is functionally similar to the CF protein and that this similarity can be exploited to clarify the properties of the nucleotide-binding fold in this superfamily of proteins.
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Affiliation(s)
- A L Gibson
- Department of Biological Chemistry, University of Michigan, Ann Arbor 48109
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71
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Shyamala V, Baichwal V, Beall E, Ames G. Structure-function analysis of the histidine permease and comparison with cystic fibrosis mutations. J Biol Chem 1991. [DOI: 10.1016/s0021-9258(18)55121-8] [Citation(s) in RCA: 144] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
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72
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Maturation and function of cystic fibrosis transmembrane conductance regulator variants bearing mutations in putative nucleotide-binding domains 1 and 2. Mol Cell Biol 1991. [PMID: 1712898 DOI: 10.1128/mcb.11.8.3886] [Citation(s) in RCA: 164] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
One feature of the mutations thus far found to be associated with the disease cystic fibrosis (CF) is that many of them are clustered within the first nucleotide-binding domain (NBD) of the CF transmembrane conductance regulator (CFTR). We sought to discover the molecular basis for this clustering by introducing into the two NBDs of CFTR mutations either mimicking amino acid changes associated with CF or altering residues within highly conserved motifs. Synthesis and maturation of the mutant CFTR were studied by transient expression in COS cells. The ability of the altered proteins to generate cyclic AMP-stimulated anion efflux was assessed by using 6-methoxy-N-(sulfopropyl) quinolinium (SPQ) fluorescence measurements in HeLa cells expressing mutated plasmids. The results show that (i) all CF-associated mutants, with one exception, lack functional activity as measured in the SPQ assay, (ii) mutations in NBD1 are more sensitive to the effects of the same amino acid change than are the corresponding mutations in NBD2, (iii) cells transfected with plasmids bearing CF-associated mutations commonly but not exclusively lack mature CFTR, (iv) NBD mutants lacking mature CFTR fail to activate Cl- channels, and (v) the glycosylation of CFTR, per se, is not required for CFTR function. We reason that the structure of NBD1 itself or of the surrounding domains renders it particularly sensitive to mutational changes. As a result, most NBD1 mutants, but only a few NBD2 mutants, fail to mature or lack functional activity. These findings are consistent with the observed uneven distribution of CFTR missense mutations between NBD1 and NBD2 of CF patients.
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73
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Gregory RJ, Rich DP, Cheng SH, Souza DW, Paul S, Manavalan P, Anderson MP, Welsh MJ, Smith AE. Maturation and function of cystic fibrosis transmembrane conductance regulator variants bearing mutations in putative nucleotide-binding domains 1 and 2. Mol Cell Biol 1991; 11:3886-93. [PMID: 1712898 PMCID: PMC361177 DOI: 10.1128/mcb.11.8.3886-3893.1991] [Citation(s) in RCA: 60] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
One feature of the mutations thus far found to be associated with the disease cystic fibrosis (CF) is that many of them are clustered within the first nucleotide-binding domain (NBD) of the CF transmembrane conductance regulator (CFTR). We sought to discover the molecular basis for this clustering by introducing into the two NBDs of CFTR mutations either mimicking amino acid changes associated with CF or altering residues within highly conserved motifs. Synthesis and maturation of the mutant CFTR were studied by transient expression in COS cells. The ability of the altered proteins to generate cyclic AMP-stimulated anion efflux was assessed by using 6-methoxy-N-(sulfopropyl) quinolinium (SPQ) fluorescence measurements in HeLa cells expressing mutated plasmids. The results show that (i) all CF-associated mutants, with one exception, lack functional activity as measured in the SPQ assay, (ii) mutations in NBD1 are more sensitive to the effects of the same amino acid change than are the corresponding mutations in NBD2, (iii) cells transfected with plasmids bearing CF-associated mutations commonly but not exclusively lack mature CFTR, (iv) NBD mutants lacking mature CFTR fail to activate Cl- channels, and (v) the glycosylation of CFTR, per se, is not required for CFTR function. We reason that the structure of NBD1 itself or of the surrounding domains renders it particularly sensitive to mutational changes. As a result, most NBD1 mutants, but only a few NBD2 mutants, fail to mature or lack functional activity. These findings are consistent with the observed uneven distribution of CFTR missense mutations between NBD1 and NBD2 of CF patients.
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Affiliation(s)
- R J Gregory
- Genzyme Corporation, Framingham, Massachusetts 01701
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74
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Abstract
The concurrent developments in electrophysiology studies and the identification of the cystic fibrosis transmembrane conductance regulator (CFTR) gene has provided a unique opportunity to probe the basic cellular defect underlying cystic fibrosis. Various properties of the CFTR protein have been deduced from its primary sequence, the variety of mutations in patients and genotype-phenotype correlations, as well as the results of more recent DNA transfection studies. The most exciting observation is the fact that CFTR acts like a cAMP-regulated Cl- channel.
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Affiliation(s)
- L C Tsui
- Hospital for Sick Children, University of Toronto, Ontario, Canada
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75
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Tsui LC, Buchwald M. Biochemical and molecular genetics of cystic fibrosis. ADVANCES IN HUMAN GENETICS 1991; 20:153-266, 311-2. [PMID: 1724873 DOI: 10.1007/978-1-4684-5958-6_4] [Citation(s) in RCA: 57] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Affiliation(s)
- L C Tsui
- Department of Genetics, Hospital for Sick Children, Toronto, Ontario, Canada
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