Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
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Previous studies from this laboratory with a 67-amino acid synthetic peptide (P-67) demonstrated directly that the first predicted nucleotide binding fold of the cystic fibrosis transmembrane conductance regulator (CFTR) binds ATP (Thomas, P.J, Shenbagamurthi, P., Ysern, S., and Pedersen, P.L. (1991) Science 251, 555-557). Although mutational analysis within the predicted second nucleotide binding fold indicates that this domain may be functionally important also, direct evidence for nucleotide binding is lacking. Here, we report the design, chemical synthesis, and purification of a 51-amino acid segment (P-51) of the second predicted nucleotide binding fold of CFTR and demonstrate that this peptide binds ATP. P-51 consists of amino acid residues from glutamic acid 1228 through threonine 1278 and contains a motif, GX4GKS, very similar or identical to that found in many nucleotide-binding proteins. The freshly dissolved peptide moves predominantly as a single species upon molecular sieve chromatography and readily binds ATP without eliciting its hydrolysis. P-51 also readily binds the fluorescent ATP analogs TNP-ATP (2'(3')-0-(2,4,6-trinitrophenyl)-adenosine-5'-triphosphate) and TNP-ADP but exhibits much less capacity to bind TNP-AMP. ATP displaces TNP-ATP with a Kd (ATP) of 0.46 mM. In the presence of the denaturant urea, P-51 loses most of its binding capacity indicating that structure is important for binding. Consistent with this conclusion, circular dichroism spectroscopy revealed that P-51 has significant secondary structure. Elements of such structure calculated from deconvolution of the circular dichroism spectra compare favorably with those predicted from the program of Chou, P.Y., and Fasman, G.D. (1977) J. Mol. Biol. 115, 135-175. These experiments provide the first direct evidence that the second predicted nucleotide binding fold of CFTR binds ATP and define a 51-amino acid segment within the approximately 150-amino acid fold critical for this function. They also indicate that the beta and gamma phosphate groups of ATP may be important for binding and that the 51-amino acid region studied is not sufficient to catalyze ATP hydrolysis. Finally, as seven different mutations within P-51 are known to cause cystic fibrosis, these studies will be important in future efforts to understand the molecular basis of the disease.
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PMID:The cystic fibrosis transmembrane conductance regulator. Nucleotide binding to a synthetic peptide segment from the second predicted nucleotide binding fold. 751 74

To gain insights into the regulation of the mouse and rat cystic fibrosis transmembrane conductance regulator (CFTR) genes, we cloned and sequenced their respective upstream promoter regions. DNA sequence analysis from either side of exon 1 revealed a complete divergence from the human DNA sequence except for three DNA motifs which consist of a 34 bp stretch and two intron specific elements. Highlights of both the rat and mouse promoter sequences include an extensive purine rich stretch, a Y-box motif and putative Sp1, AP1 sites. Transfection of mouse promoter deletional constructs into expressing and non-expressing CFTR murine cell lines revealed that the Pu.Py stretch and the Y-box act, respectively, as negative and positive elements of basal transcription that confer no apparent tissue specificity.
Hum Mol Genet 1994 Jul
PMID:Analysis of the mouse and rat CFTR promoter regions. 752 24

The absence of pathologic changes in newborn cystic fibrosis (CF) lung suggests that the fetal CF lung is inflated with a normal volume of liquid and that Cl- is secreted through paths other than the cystic fibrosis transmembrane conductance regulator (CFTR)-associated Cl- channel. We studied liquid content of distal lung and transepithelial electrical potential difference (PD) of cultured cystic tracheal explants from 16 to 19 day gestation fetal mice of CFTR (+/-)(heterozygous) females that were mated with CFTR (-/-) "knockout" males. Distal lung water content was not affected by fetal genotype. Basal PDs were not different (CFTR (+/-), 8.6 mV, and CFTR (-/-), 9.1 mV), and PDs of both groups were inhibited by intraluminal injection of amiloride (10(-4) M) (-25%) and after addition of bumetanide (10(-4) M) to the bath (-40%). Terbutaline (3 x 10(-5) M) induced a similar increase in PD (about 65%) in both groups. Intraluminal injection of ionomycin (2 x 10(-5) and 5 x 10(-6) M) raised PD in both groups (CFTR (+/-) by 32 and 27% and CFTR (-/-) by 41 and 11%). All of the increase in PD induced by terbutaline and ionomycin was inhibited by bumetanide. The PD response to terbutaline was not attenuated by pretreatment with ionomycin or the Ca2+ chelator BAPTA (10(-4) M). Ionomycin or ATP, but not terbutaline, increased intracellular Ca2+ concentration of isolated cultured tracheal epithelial cells.(ABSTRACT TRUNCATED AT 250 WORDS)
Am J Respir Cell Mol Biol 1995 Sep
PMID:Cl- secretion by trachea of CFTR (+/-) and (-/-) fetal mouse. 754 95

To assess the feasibility of protein replacement as a potential therapy for cystic fibrosis, we have evaluated the ability of influenza hemagglutinin (HA) to mediate the delivery of purified cystic fibrosis transmembrane conductance regulator (CFTR) to recipient cells in vitro. CFTR was purified from both CHO cells and Sf9 cells and reconstituted into two different types of vesicular delivery vehicles. In one, CFTR and HA were co-reconstituted into the same lipid vesicle. After binding to the cell surface, delivery of CFTR to the recipient cell was achieved by a transient, low-pH activation of the fusion activity of HA. A second delivery strategy used HA virosomes together with purified CFTR that had been reconstituted into vesicles containing gangliosides, a receptor for HA. After binding of the HA virosomes and CFTR-containing vesicles to the recipient cells, delivery to the plasma membrane again was achieved by a transient pH drop. Delivery of functional CFTR was assessed using the SPQ fluorescence assay. Functional CFTR was detected in a fraction (> 20%) of the recipient cells using this assay. Quantitative binding and fusion assays using radiolabeled virosomes and lipid vesicles showed that on the order of 1,000 of the added CFTR-containing vesicles bound to each C127 cell under the conditions of our delivery protocols. However, only a fraction of these vesicles fused and delivered CFTR to the cell plasma membrane. The two delivery strategies were found to be approximately equivalent in their ability to deliver active CFTR, and there were no significant differences between deliveries using purified CFTR from either cell source. These feasibility studies suggest that purified CFTR can be delivered to a recipient cell in a functional form and therefore represent a significant step in establishing the concept of protein replacement as a therapy for cystic fibrosis.
Am J Respir Cell Mol Biol 1995 Sep
PMID:Delivery of purified, functional CFTR to epithelial cells in vitro using influenza hemagglutinin. 754 96

Chloride channel activity of cystic fibrosis transmembrane conductance regulator (CFTR) requires activation of protein kinase A (PKA) by 3'-5'-cyclic adenosine monophosphate (cAMP). The level of cAMP is controlled by the balance between cAMP synthesis and hydrolysis by adenylate cyclase and phosphodiesterases (PDEs), respectively. CFTR channel activity appears to be most sensitive to the activity of type III cyclic nucleotide PDEs in Calu-3 and 16HBE cells, both derived from airway epithelium and expressing wild-type CFTR. Type III PDEs can be identified by their sensitivity to specific inhibitors such as milrinone and amrinone. In Calu-3 cells, specific inhibition of type III PDEs increased chloride efflux up to 13.7-fold, whereas neither rolipram nor Ro20-1724 (type IV PDE inhibitors) nor 3-isobutyl-1-methylxanthine (IBMX, a nonspecific PDE inhibitor) elicited significant increases. None of these compounds had an appreciable effect on total cellular cAMP levels, yet the effects of milrinone and amrinone on chloride efflux were blocked by treatment of cells with Rp-cAMPS, a cAMP analog that inhibits PKA at the site of cAMP binding. Similarly, H-8, an inhibitor of PKA, reduced milrinone-stimulated chloride efflux, indicating that efflux is mediated through the cAMP/PKA pathway. Whole-cell patch clamp analysis revealed that milrinone generated chloride conductances with properties consistent with those of CFTR. Milrinone elicited chloride currents in a dose-dependent manner and induced CFTR activity in the absence of adenylate cyclase agonists. These data suggest that type III PDEs are specifically involved in CFTR activation in airway epithelial cells and that PDE regulation of CFTR may involve subcellular compartments of cAMP.
Am J Respir Cell Mol Biol 1995 Dec
PMID:CFTR-mediated chloride permeability is regulated by type III phosphodiesterases in airway epithelial cells. 757 3

The cystic fibrosis transmembrane conductance regulator (CFTR) transports Cl- in the apical membrane of secretory epithelial cells. Normal lung development is critically dependent on active Cl- secretion by developing airway epithelia. In this study, the polymerase chain reaction (PCR) was used to detect CFTR mRNA expression in rabbit lung at different stages of development. Using nested amplification in exons 7 and 11, a 494-bp fragment was isolated from cDNA prepared from lungs obtained at gestational days 22 (pseudoglandular) and 29 (terminal sac). Nucleotide sequencing verified the identification of rabbit CFTR sequences. At day 22 of gestation, CFTR was detected in fetal liver, kidney, heart, intestine, and brain. CFTR could not be amplified from adult rabbit brain. CFTR protein was detected using a polyclonal antibody raised in chickens against a synthetic peptide from the R domain conjugated to thyroglobulin. Rabbit CFTR migrated as a 165-kD protein on 5% sodium dodecyl sulfate polyacrylamide gels when detected either by chicken anti-R IgG or a previously characterized rabbit anti-R antibody. In frozen sections of fetal rabbit lung at day 22 of gestation, CFTR was localized to the membrane regions of primitive tubular epithelial cells and absent from surrounding connective tissue. At day 29, CFTR was concentrated in the apical region of bronchiolar epithelial cells and absent from alveoli and vessels. These results suggest that CFTR gene expression begins very early in lung development and, with differentiation of the airways, becomes confined to differentiated bronchiolar epithelium, the presumed site for cAMP-mediated Cl- secretion.
Am J Respir Cell Mol Biol 1993 Feb
PMID:Cystic fibrosis gene and protein expression during fetal lung development. 767 68

The identification of the cystic fibrosis transmembrane conductance regulator (CFTR) gene has led to the identification of more than 225 presumed disease-causing mutations at the locus. The diagnosis of cystic fibrosis or the carrier state by direct DNA analysis is hindered by this large number. A practical assay must be able to detect enough mutations to achieve clinically significant sensitivity. The use of allele-specific oligonucleotide probes is the most promising of the available methods. However, to date this has generally involved tedious probe-by-probe hybridizations, due to variations in the oligonucleotides' denaturation temperatures caused by differences in their G-C base-pair content. We have developed a rapid, cost-effective assay that simultaneously detects 12 CFTR mutations after multiplex polymerase-chain-reaction amplification of genomic DNA. The test may be readily extended to detect additional mutations at minimal increase in the cost per test or the turnaround time. We improve specificity and avoid the need for individual hybridizations by the use of tetramethylammonium chloride to virtually eliminate the effects of G-C differences. Coupled with non-invasive sample-collection methods, this is an immediately practical assay for cystic fibrosis. More generally, it will serve as a model for the development of diagnostic tests in other genetic disorders involving complex mutation analysis.
Hum Mol Genet 1993 Feb
PMID:Efficient 12-mutation testing in the CFTR gene: a general model for complex mutation analysis. 768 36

The cystic fibrosis transmembrane conductance regulator (CFTR) gene encodes a cAMP-activated chloride (Cl-) channel, and expression of the full length gene in vitro is sufficient to correct the Cl- conductance defect that is characteristic of cystic fibrosis (CF) epithelial cells. Alternatively spliced forms of CFTR mRNA have been identified in several tissues from normal individuals. One of the alternative transcripts, often present at high levels, results in the in-frame deletion of exon 9. Translation of this transcript would result in a CFTR protein missing the amino terminal portion of the first nucleotide binding fold (NBF). To evaluate the possible function of this form of CFTR, a cDNA representing this transcript (CFTR delta 9) was transduced into CFPAC cells, which are derived from a CF patient. CFTR delta 9 RNA was expressed in the transduced cell lines, but only immature, incompletely glycosylated protein was detectable by Western blot analysis. No increase in cAMP-activated anion permeability was detectable by 125I efflux assay or by means of the halide sensitive dye 6-methoxy-N-(3-sulfopropyl) quinolinium (SPQ). In a second assay system, in vitro synthesized mRNA representing CFTR delta D9 was injected into Xenopus oocytes, but expression of this alternatively spliced form of CFTR was not associated with the appearance of Cl- conductance. These results suggest that the protein produced by the CFTR delta 9 transcript is not properly processed and is not capable of generating Cl- conductance in response to cAMP. Whether this alternative transcript has some other function or represents 'noise' in the mRNA splicing mechanism remains unresolved.
Hum Mol Genet 1993 Mar
PMID:Expression of an abundant alternatively spliced form of the cystic fibrosis transmembrane conductance regulator (CFTR) gene is not associated with a cAMP-activated chloride conductance. 768 41

Single sperm typing provides an accurate method to order tightly linked loci by single cell DNA high resolution segregation analysis. We have used similar methods to type individual sperm from a known delta F508 cystic fibrosis heterozygote to determine the frequency of the mutation within his germ cell population, and to test possible explanations for the reported sex ratio distortion of the cystic fibrosis (CF) mutation to male offspring. Using a nested polymerase chain reaction we have been able to amplify a single locus sequence, cystic fibrosis transmembrane conductance regulator (CFTR), from a single target sperm haploid genome to detectable amounts without the use of radioactivity. The same sperm from a single male delta F508 carrier were simultaneously typed for the presence of the sex chromosomes to verify the ratio of X- to Y-bearing sperm and to determine the association, if any, between sex and delta F508 in male gametes. We have demonstrated that there is a significant difference in the proportions of 'normal' and 'delta F508' sperm (X2 = 7.36, p < 0.01), although when the same sperm are sexed the difference between delta F508/X and delta F508/Y sperm is not significant (X2 = 1.71, p = 0.192). Single sperm typing can address questions about segregation distortion in man, and it is unlikely that sex ratio distortion for CF carriers is due to events which occur pre-fertilisation. As these data are from one individual only, they should be confirmed for other male carriers, including those with different CF mutations.
Hum Mol Genet 1993 Apr
PMID:Segregation of delta F508 and normal CFTR alleles in human sperm. 768 44

In order to characterize the non-delta F508 mutations that account for 36% of cystic fibrosis (CF) chromosomes in Southern France in a sample of 137 patients, we have systematically screened the entire coding region and adjacent sequences of the cystic fibrosis transmembrane conductance regulator (CFTR) gene by the single strand conformation polymorphism (SSCP) technique followed by direct sequencing of the mutant DNAs. We identified 13 novel mutations (9 reported in this paper) and 4 novel rare nucleotide sequence variations. Forty different mutations including delta F508, located in 15 exons, account for only 91.2% of mutants in a population originating from Southern France, in contrast with a recent report on the Celtic population of Brittany demonstrating that 90% of mutations can be detected with only three mutations. We present a very large spectrum of different CF mutations identified in a small geographical area.
Hum Mol Genet 1993 Aug
PMID:Analysis of the 27 exons and flanking regions of the cystic fibrosis gene: 40 different mutations account for 91.2% of the mutant alleles in southern France. 769 44


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