Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
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Recent studies suggest that the cystic fibrosis (CF) transmembrane conductance regulator (CFTR) protein modulates epithelial reduced glutathione (GSH) transport and when defective creates an antioxidant imbalance. To test whether the CFTR protein modulates lung antioxidant defenses in vivo, epithelial lining fluid (ELF) and lung tissue from CFTR knockout (CFTR-KO) and wild-type (WT) mice were compared for GSH content and the activities of glutathione reductase, glutathione peroxidase, and gamma-glutamyltransferase. In the CFTR-KO mice, the ELF concentration of GSH was decreased (51%) compared with that in WT mice. The concentration of GSH in the lung tissue of CFTR-KO mice, however, was not significantly different from that in WT mice. The activities of glutathione reductase and glutathione peroxidase in the lung tissue of CFTR-KO mice were significantly increased compared with those in WT mice (48 and 28%, respectively). Tissue lipid and DNA oxidation were evaluated by measurement of thiobarbituric acid-reactive substances and 8-hydroxy-2'-deoxyguanosine, respectively. The levels of thiobarbituric acid-reactive substances and 8-hydroxy-2'-deoxyguanosine in the lung tissue of CFTR-KO mice were significantly increased compared with those in WT mice. These data support our hypothesis that a mutation in the CFTR gene can affect the antioxidant defenses in the lung and may contribute to the exaggerated inflammatory response observed in CF.
Am J Physiol Lung Cell Mol Physiol 2001 Jul
PMID:Antioxidant imbalance in the lungs of cystic fibrosis transmembrane conductance regulator protein mutant mice. 1140 42

This study was designed to test the in vivo efficacy of the chemical chaperone trimethylamine oxide (TMAO) in correcting the Cl- transport defect in a mouse model of cystic fibrosis (CF). Rectal potential difference (RPD) measurements were done in matched wild-type and DeltaF508 CF mice. Mice were treated by subcutaneous injections of TMAO. Wild-type mice demonstrated a forskolin-stimulated, Cl--dependent hyperpolarization of -6.4 +/- 0.8 mV (n = 11), which was significantly increased to -13.1 +/- 1.4 mV after treatment with TMAO. DeltaF508 CF mice showed no significant responses to forskolin. Treatment with TMAO recovered a forskolin-activated RPD in DeltaF508 CF mice (-1.1 +/- 0.2 mV; n = 17) but not in CFTR null mice. The effects of TMAO were dose dependent, resulting in a slope of -0.4 +/- 0.1 mV x g(-1) x kg(-1) in DeltaF508 CF mice. The forskolin-stimulated RPD in TMAO-treated DeltaF508 CF mice was partially blocked by glibenclamide and further stimulated by apigenin. The total response to forskolin plus apigenin was -2.5 +/- 0.45 mV (n = 6 mice), corresponding to 39% of the response evoked by forskolin only in wild-type mice.
Am J Physiol Lung Cell Mol Physiol 2001 Jul
PMID:Partial restoration of defective chloride conductance in DeltaF508 CF mice by trimethylamine oxide. 1140 43

Poly-l-lysine, with 40% of its amino groups substituted with lactose, is an effective vector to transfer the CFTR gene into CF airway epithelial cells and correct the chloride channel dysfunction. The intracellular fate of the lactosylated poly-l-lysine/cDNA complex was studied using confocal microscopy. In the presence of chloroquine the complex remained intact during internalization, intracellular transport, and, most importantly, transport into the nucleus. When cells were transfected in the presence of agents that enhance transfection efficiency such as E5CA peptide, a fusogenic peptide, or glycerol a similar fate of the lactosylated poly-l-lysine/cDNA complex was seen. However, when these agents were omitted from the transfection medium, the complex remained in the perinuclear region. Uncomplexed lactosylated poly-l-lysine reached the nucleus efficiently. In contrast mannosylated poly-l-lysine or unsubstituted poly-l-lysine complexed to plasmid did not. Therefore the nuclear accumulation of the complex may be attributed to the substitution of poly-l-lysine with lactose. It is hypothesized that the lactose residues provide for nuclear localization by means of targeting a potential lectin-like protein with galactose/lactose specificity. This mechanism may be responsible for the nuclear internalization of the complex.
Mol Ther 2001 Jun
PMID:Nuclear translocation of lactosylated poly-L-lysine/cDNA complex in cystic fibrosis airway epithelial cells. 1140 96

We have developed an expression cassette for cystic fibrosis (CF) gene therapy using control elements from the human cytokeratin 18 gene (KRT18, also known as K18). KRT18 is naturally expressed in a spatial pattern similar to that of CFTR, the gene mutated in CF. We delivered a KRT18-driven lacZ plasmid complexed with cationic liposomes intravenously to mice and examined expression in various tissues. We found expression in nasal and bronchial epithelium, airway submucosal glands, gall bladder, and kidneys. Expression was low in pancreas and gut, and absent from liver and alveolar lung. This is consistent with the expression pattern reported for a K18lacZ transgenic mouse. Following delivery of a cytomegalovirus (CMV) major immediate-early promoter/enhancer-driven lacZ plasmid, we found expression in bronchi, submucosal glands, alveolar cells, liver, and kidney. We did not detect expression in nose, pancreas, gall bladder, or gut. Using fluorescently labeled plasmid delivered by means of liposomes, we identified the liver, alveolar lung, and kidneys as the major plasmid deposition sites. Our data demonstrate that a KRT18-driven expression vector delivered systemically can target gene expression to CF-affected tissues, despite an uneven distribution of plasmid DNA. A KRT18-based vector may be a useful alternative to viral promoter-based vectors in clinical gene therapy trials to treat CF.
Mol Ther 2001 Jul
PMID:Targeting transgene expression for cystic fibrosis gene therapy. 1147 7

Defective cystic fibrosis (CF) transmembrane conductance regulator (CFTR)-mediated Cl(-) transport across the apical membrane of airway epithelial cells is implicated in the pathophysiology of CF lungs. A strategy to compensate for this loss is to augment Cl(-) transport through alternative pathways. We report here that partial correction of this defect could be attained through the incorporation of artificial anion channels into the CF cells. Introduction of GL-172, a synthetic analog of squalamine, into CFT1 cells increased cell membrane halide permeability. Furthermore, when a Cl(-) gradient was generated across polarized monolayers of primary human airway or Fischer rat thyroid cells in an Ussing chamber, addition of GL-172 caused an increase in the equivalent short-circuit current. The magnitude of this change in short-circuit current was ~30% of that attained when CFTR was maximally stimulated with cAMP agonists. Patch-clamp studies showed that addition of GL-172 to CFT1 cells also increased whole cell Cl(-) currents. These currents displayed a linear current-voltage relationship and no time dependence. Additionally, administration of GL-172 to the nasal epithelium of transgenic CF mice induced a hyperpolarization response to perfusion with a low-Cl(-) solution, indicating restoration of Cl(-) secretion. Together, these results demonstrate that in CF airway epithelial cells, administration of GL-172 is capable of partially correcting the defective Cl(-) secretion.
Am J Physiol Lung Cell Mol Physiol 2001 Nov
PMID:Partial correction of defective Cl(-) secretion in cystic fibrosis epithelial cells by an analog of squalamine. 1159 8

Genzyme is developing therapies to replace the defective forms of the cystic fibrosis (CF) transmembrane conductance regulator (CFTR) protein in CF patients. The company is developing a gene therapy, as well as a recombinant production of CFTR for protein replacement therapy. Both approaches have been granted orphan drug status by the FDA [156348]. The results of several clinical trials were discussed at the first annual meeting of the American Society of Gene Therapy in May 1998. A single dose nasal administration was well tolerated by volunteers, but had disappointing efficacy. In a study completed at the Royal Brompton Hospital, London, a single dose aerosol application of GL-67:DOPE was administered to eight patients, while another eight received GL-67:DOPE plus pCF1-CFTR. In the second group, a moderate increase in the potential difference in the lung was observed, with a slight trend towards bacterial adherence normalization in the airway cells. Seven of the patients in the second group, and three patients who received lipid alone, developed, flu-like symptoms within 24 h. A trial at the University of Alabama, using the same formulation, showed that flu-like symptoms developed in six of eight patients by day two, and in all patients by day seven [290120]. In 1995, the company began a clinical safety trial involving delivery of a normal CF gene to the patient's lungs via an adenovirus vector. The administration involves the inhalation of an aerosol containing the vector or, separately, delivery to one lobe of the patient's lung via a bronchoscope [191678]. To evaluate additional delivery methods for the gene, Genzyme has an exclusive research agreement for the use of Vical's cytofectins as non-viral delivery vectors for CFTR. Also under investigation are delivery systems for the nasal epithelium using liposomes or lipid-DNA complexes. These protocols are being developed in collaboration with the National Heart & Lung Institute, London, and an undisclosed partner [162590], [177633]. Following in vitro screenings by the company, two T-shaped molecules were identified (GL-67 and GL-53), the gene transfer activities of which could be enhanced by dioleoyl-PE (DOPE). A recently-completed clinical trial in 16 CF patients demonstrated that the GL-67:DOPE:DMPE-PEG5000-pCF1-CFTR compound accumulated in the lung with minimal toxicity and resulted in a 25% correction of CF symptoms [268093]. Genzyme has also developed recombinant cell lines that synthesize CFTR and has used transgenic expression techniques to breed mice, rabbits and goats which secrete the protein in their milk. Protein replacement therapy is currently in preclinical investigation and research efforts have been reduced infavor of the gene therapeutic approach [177633].
Curr Opin Mol Ther 1999 Apr
PMID:Technology evaluation: cystic fibrosis therapy, Genzyme. 1171 52

cDNA fragments of both the alpha- and beta-subunits of the Na, K-ATPase and a cDNA fragment of the secretory form of Na-K-Cl cotransporter from the European dogfish (Scyliorhinus canicula) were amplified and cloned using degenerate primers in RT-PCR. These clones were used along with a sCFTR cDNA from the related dogfish shark, Squalus acanthias to characterise the expression of mRNAs for these ion transporters in the dogfish rectal gland subsequent to an acute feeding episode. Following a single feeding event where starved dogfish were fed squid portions (20 g squid/kg fish), there was a delayed and transient 40-fold increase in the activity of Na, K-ATPase in crude rectal gland homogenates. Increases in enzyme activity were apparent 3 h after the feeding event and peaked at 9 h before returning to control values within 24 h. These increases in activity were accompanied by small and transient decreases in plasma sodium and chloride concentrations lasting up to 3 days. Significant increases in the expression of mRNAs for alpha- and beta-subunits of the Na, K-ATPase, the Na-K-Cl cotransporter and CFTR chloride channel were detected but not until 1-2 days after the feeding event. It is concluded that the transient increase in Na, K-ATPase activity is not attributable to increases in the abundance of alpha- and beta-subunit mRNAs but must be associated with some, as yet unknown, post-transcriptional activation mechanism.
Comp Biochem Physiol B Biochem Mol Biol 2002 Feb
PMID:The effects of dietary sodium loading on the activity and expression of Na, K-ATPase in the rectal gland of the European dogfish (Scyliorhinus canicula). 1181 40

The majority of cystic fibrosis patients produce a mutant form of CFTR (DeltaF508) which has been shown to be mislocalized in both humans and mice. G480C, another clinically 'severe' mutation, has also been demonstrated to be defective in its intracellular processing, but when allowed to traffic in Xenopus oocytes showed similar channel characteristics to that of wild-type CFTR. We have replicated the G480C mutation in the murine Cftr gene using the 'hit and run' double recombination procedure. As expected, the G480C cystic fibrosis mouse model expresses the G480C mutant transcript at a level comparable to that of wild-type CFTR: The homozygous mutant mice were fertile, had normal survival, weight, tooth colour and no evidence of caecal blockage, despite mild goblet cell hypertrophy in the intestine. Analysis of the mutant protein revealed that the majority of G480C CFTR was abnormally processed and no G480C CFTR-specific immunostaining in the apical membranes of intestinal cells was detected. The bioelectric phenotype of these mice revealed organ-specific electrophysiological effects. In contrast to DeltaF508 'hit and run' homozygotes, the classic defect of forskolin-induced chloride ion transport is not replicated in the caecum, but the response to low chloride in the nose is clearly defective in the G480C mutant animals. The mild phenotype of these G480C mutant animals combined with the defective chloride transport in the nose uniquely provides a valuable resource to test novel pharmacological agents aimed at improving trafficking and correcting the electrophysiological defect in the respiratory tract.
Hum Mol Genet 2002 Feb 01
PMID:The severe G480C cystic fibrosis mutation, when replicated in the mouse, demonstrates mistrafficking, normal survival and organ-specific bioelectrics. 1182 43

Evidence is discussed that apical CFTR Cl- channels of mitochondria-rich (MR) cells of Bufo bufo skin conduct beta-adrenergic receptor-activated Cl- currents. Ussing chambers studies revealed the following selectivity sequence of the receptor activated conductance, Cl- > Br- > NO3- > I-. With ion selective microelectrode-techniques, it was shown that receptor-coupled Cl- channels are not located in principal cells. A small conductance (7-10 pS) CFTR-like Cl- channel is located in the apical plasma membrane of MR cells. Short life times of sealed patches prevented detailed study of its selectivity to other halide ions and its molecular regulation. With monoclonal hCFTR-antibodies, selective expression in MR cells of the targeted antigens could be demonstrated. A transcript of CFTR was amplified in the skin, and a bbCFTR cDNA clone was generated from toad skin mRNA that exhibits 89% amino acid identity with the human homologue. The frequency of obtaining channels in patch clamp studies was too low for accounting quantitatively for the macroscopic conductance. Since MR cells were isolated by trypsin, and a putative extracellular loop of the deduced bbCFTR protein contains a target peptide bond for trypsin, enzyme treatment may have destroyed apical CFTR molecules.
Comp Biochem Physiol A Mol Integr Physiol 2001 Oct
PMID:Expression of cystic fibrosis transmembrane conductance regulator in the skin of the toad, Bufo bufo and possible role for Cl- transport across the heterocellular epithelium. 1191 65

Guanylyl cyclase C (GC-C) was found to function as the principal receptor for heat-stable enterotoxins (STa), major causative factors in E. coli-induced secretory diarrhea. GC-C is enriched in intestinal epithelium, but was also detected in other epithelial tissues. The enzyme belongs to the family of receptor guanylyl cyclases, and consists of an extracellular receptor domain, a single transmembrane domain, a kinase homology domain, and a catalytic domain. GC-C is modified by N-linked glycosylation and, at least in the small intestine, by proteolysis, resulting in a STa receptor that is coupled non-covalently to the intracellular domain. So far two endogenous ligands of mammalian GC-C have been identified i.e. the small cysteine-rich peptides guanylin and uroguanylin. The guanylins are released in an auto- or paracrine fashion into the intestinal lumen but may also function as endocrine hormones in gut-kidney communication and as regulators of ion transport in extra-intestinal epithelia. They are thought to activate GC-C by inducing a conformational change in the extracellular portion of the homotrimeric GC-C complex, which allows two of the three intracellular catalytic domains to dimerize and form two active catalytic clefts. In the intestine, activation of GC-C results in a dual action: stimulation of Cl and HCO3 secretion, through the opening of apical CFTR Cl channels; and inhibition of Na absorption, through blockade of an apical Na/H exchanger. The principal effector of the GC-C effect on ion transport is cGMP dependent protein kinase type II, which together with GC-C and the ion transporters, may form a supramolecular complex at the apical border of epithelial cells.
Mol Cell Biochem 2002 Jan
PMID:Structure and function of the heat-stable enterotoxin receptor/guanylyl cyclase C. 1195 98


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