Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.7.11.1 (protein kinase)
81,284 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The human colonic epithelial cell line HT29, and its clonal derivatives HT29-18 and HT-29-18-C1, differentiate in vitro. Differential screening of a subtraction cDNA library enriched for sequences unique to HT29-18-C1, a highly differentiated subclone of HT29-18, resulted in the isolation of a differentiation-dependent cDNA clone, A4. A full-length clone encoding A4 was obtained and sequenced to its entirety. It is 945 bp in length and contains an open reading frame (ORF) of 456 bp. The amino acid sequence deduced from the ORF reveals a polypeptide of 152 amino acids with a predicted molecular mass of 17,000 Da, a size confirmed by coupled in vitro transcription and translation directed by the full-length A4 cDNA. This polypeptide contains four potential membrane-spanning domains and consensus sequences for N-linked glycosylation as well as phosphorylation sites for protein kinase C and casein kinase II. Comparison of A4 to published DNA and protein sequences revealed no significant homology. Genomic Southern blot analysis suggests that the gene is present in a single copy within the human genome and is conserved in the rat. Northern blot analysis of RNA obtained from various rat tissues shows that the expression of the A4 gene is tissue-selective and is enriched in colonic mucosa. In situ hybridization using human intestinal tissues indicates that the expression of A4 follows a gradient along the crypt-to-villus axis with the most abundant message occurring in the lower half of the crypt. Furthermore, nuclear run-on assays suggest that the induction of the A4 gene during differentiation of HT29-18 is regulated at a transcriptional level. A clone was isolated from a human genomic library and found to contain all five exons of A4. S1 nuclease analysis localized the start site of transcription to an adenosine residue 91 nucleotides upstream from the ATG translation initiation codon. Examination of the immediate sequence 5' to the mRNA start site reveals no TATA box and multiple known enhancer sequences. A4 is also noted to share certain features with the gene encoding the cystic fibrosis transmembrane conductance regulator protein. They include a similar vertical distribution of expression along the intestinal epithelium, enhanced transcription upon differentiation of HT29-18, and multiple shared putative regulatory sequences in the promoter regions. Further characterization of the mechanisms regulating expression of the A4 gene could contribute to the understanding of mammalian intestinal differentiation.
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PMID:Isolation and characterization of a differentiation-dependent gene in the human colonic cell line HT29-18. 847 Aug 95

The effect of several opiate compounds on I- efflux was investigated in cultured cell lines. I- efflux was evoked by two distinct stimuli, namely cell swelling and elevation of cellular cAMP levels by prostaglandin E2. Cells expressing the multidrug resistance P-glycoprotein were found to have increased I- efflux in response to hypo-osmotic challenge. This increased I- efflux in P-glycoprotein containing cells was reduced to levels found in parental cells by the opiates morphine, pentazocine and naloxone. Addition of prostaglandin E2 to T84 cells resulted in elevated cellular cAMP levels and a significant I- efflux. This cAMP stimulated efflux was also inhibited by several opiates. None of the opiates was able to alter cAMP levels or protein kinase A mediated phosphorylation of immunoprecipitated cystic fibrosis transmembrane conductance regulator (CFTR) Cl- channel in T84 cells. The ability of opiates to alter ion conductances is discussed in relation to the anti-diarrheal effects of these compounds.
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PMID:Opiates inhibit ion conductances elicited by cell swelling and cAMP in cultured cells. 856 69

We demonstrate that in immortalized normal human tracheal epithelial cells (NT-1 and 56FHTE8o-) 14C-labeled glycoconjugate secretion may be regulated independently by agonists of the protein kinase A (PKA) and protein kinase C (PKC) signaling pathways. In contrast, in immortalized cystic fibrosis (CF) human tracheal epithelial cells (CFT-1 and CFT-2), regulation is defective for agonists specific for the PKA but not for the PKC pathway. To characterize the involvement of the cystic fibrosis transmembrane conductance regulator (CFTR) in regulated glycoconjugate secretion, we examined the effect of adenovirus-mediated gene transfer of CFTR to CF and control cells. Forty-eight hours after infection, at a multiplicity of infection of 50 plaque-forming units per cell, high levels of CFTR mRNA were detected by reverse transcription-polymerase chain reaction, and de novo synthesis of CFTR protein was demonstrated by immunoblotting. Gene transfer to CF cells restored defective adenosine 3',5'-cyclic monophosphate (cAMP)-dependent secretion not only of chloride but also of glycoconjugates. Taken together, these results argue for a role for CFTR in cAMP-mediated glycoconjugate secretion.
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PMID:CFTR gene transfer corrects defective glycoconjugate secretion in human CF epithelial tracheal cells. 857 48

A clone encoding a 5TH7 receptor, XM2, has been isolated from Xenopus laevis. The mRNA encoding XM2 is expressed in brain, liver, muscle, kidney, intestine and skin, but not in heart or lung. Co-expression of XM2 and the cystic fibrosis transmembrane conductance regulator (CFTR) in Xenopus oocytes demonstrated coupling of the receptor and the channel via the protein kinase A pathway. A rank order of potency was obtained for serotonergic agonists of 5-hydroxytryptamine (5HT) > or = 5-methoxytryptamine (5MeOxyT) > or = alpha-methyl-5-hydroxytryptamine (alpha Me5HT) > 8-OH-DPAT, and for serotonergic antagonists of ritanserin > NAN190 > mesulergine not equal to pindolol. Thus, XM2 encodes a 5HT receptor with sequence homology to mammalian 5HT7 receptors, a similar intracellular signal transduction and receptor pharmacology, but a broader distribution in peripheral tissues.
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PMID:Cloning and expression of a 5HT7 receptor from Xenopus laevis. 858 94

Cystic fibrosis is caused by defects in a chloride-transporting protein termed cystic fibrosis transmembrane conductance regulator (CFTR). This study presents an innovative procedure to evaluate expression of functional CFTR. The technique uses the potential-sensitive probe bis-(1,3-diethylthiobarbituric acid) trimethine oxonol or DiSBAC2(3), by single-cell fluorescence imaging. The DiSBAC2(3) method was first validated on the mouse mammary tumor cell line C127, stably expressing wild-type CFTR. Activation of protein kinase A by the cAMP-permeable analogue 8-Br-cAMP induced cell membrane depolarization consistent with expression of wild-type CFTR. The DiSBAC2(3) method is quick, simple, and reproducible, and does not require invasive cell loading procedures. The system was then applied to the cell model of the human lung tumor cell line A549, in which exogenous CFTR was expressed by infecting with the replication-deficient recombinant adenovirus AdCFTR. DiSBAC2(3) was able to detect the fraction of cells in which the expression of CFTR protein was confirmed by immunocytochemistry. The DiSBAC2(3) probe was also used in human nasal respiratory cells cultured in vitro, in which it efficiently discriminated between endogenous CFTR in normal and CF cells. Functional evaluation of CFTR function by the described method can be a useful tool to detect the expression of the CF gene transferred by adenoviral vectors for use in gene therapy trials.
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PMID:Use of a membrane potential-sensitive probe to assess biological expression of the cystic fibrosis transmembrane conductance regulator. 859 Jul 31

The cystic fibrosis transmembrane conductance regulator (CFTR) is a chloride ion channel regulated by protein kinase A and adenosine triphosphate (ATP). Loss of CFTR-mediated chloride ion conductance from the apical plasma membrane of epithelial cells is a primary physiological lesion in cystic fibrosis. CFTR has also been suggested to function an an ATP channel, although the size of the ATP anion is much larger than the estimated size of the CFTR pore. ATP was not conducted through CFTR in intact organs, polarized human lung cell lines, stably transfected mammalian cell lines, or planar lipid bilayers reconstituted with CFTR protein. These findings suggest that ATP permeation through the CFTR is unlikely to contribute to the normal function of CFTR or to the pathogenesis of cystic fibrosis.
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PMID:Failure of the cystic fibrosis transmembrane conductance regulator to conduct ATP. 859 59

Experiments were designed to test if immunopurified outwardly rectified chloride channels (ORCCs) and the cystic fibrosis transmembrane conductance regulator (CFTR) incorporated into planar lipid bilayers are regulated by G-proteins. pertussis toxin (PTX) (100 ng/ml) + NAD (1 mM) + ATP (1 mM) treatment of ORCC and CFTR in bilayers resulted in a 2-fold increase in single channel open probability (Po) of ORCC but not of CFTR. Neither PTX, NAD, nor ATP alone affected the biophysical properties of either channel. Further, PTX conferred a linearity to the ORCC current-voltage curve, with a slope conductance of 80 +/- 3 picosiemens (pS) in the +/- 100 mV range of holding potentials. PKA-mediated phosphorylation of these PTX + NAD-treated channels further increased the Po of the linear 80-pS channels from 0.66 +/- 0.05 to >0.9, and revealed the presence of a small (16 +/- 2 pS) linear channel in the membrane. PTX treatment of a CFTR-immunodepleted protein preparation incorporated into bilayer membranes resulted in a similar increase in the Po of the larger conductance channel and restored PKA-sensitivity that was lost after CFTR immunodepletion. The addition of guanosine 5'-3-O-(thio)triphosphate (100 mum) to the cytoplasmic bathing solutions decreased the activity of the ORCC and increased its rectification at both negative and positive voltages. ADP-ribosylation of immunopurified material revealed the presence of a 41-kDa protein. These results demonstrate copurification of a channel-associated G-protein that is involved in the regulation of ORCC function.
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PMID:G-protein regulation of outwardly rectified epithelial chloride channels incorporated into planar bilayer membranes. 861 45

The cystic fibrosis transmembrane conductance regulator (CFTR) constitutes a linear conductance chloride channel, which is regulated by cAMP-dependent protein kinase phosphorylation at multiple sites located in the intracellular regulatory (R) domain. Studies in a lipid bilayer system, reported here, provide evidence for the control of CFTR chloride channel by its R domain. The exogenous R domain protein (encoded by exon 13 plus 85 base pairs of exon 14) interacted specifically with the CFTR molecule and inhibited the chloride conductance in a phosphorylation-dependent manner. Only the unphosphorylated R domain protein blocked the CFTR channel. Such functional interaction suggests that the putative gating particle of the CFTR chloride channel resides in the R domain.
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PMID:Phosphorylation-dependent block of cystic fibrosis transmembrane conductance regulator chloride channel by exogenous R domain protein. 863 56

The apical membrane of intestinal epithelial cells harbors a unique isozyme of cGMP-dependent protein kinase (cGK type II) which acts as a key regulator of ion transport systems, including the cystic fibrosis transmembrane conductance regulator (CFTR)-chloride channel. To explore the mechanism of cGK II membrane-anchoring, recombinant cGK II was expressed stably in HEK 293 cells or transiently in COS-1 cells. In both cell lines, cGK II was found predominantly in the particulate fraction. Immunoprecipitation of solubilized cGK II did not reveal any other tightly associated proteins, suggesting a membrane binding motif within cGK II itself. The primary structure of cGK II is devoid of hydrophobic transmembrane domains; cGK II does, however, contain a penultimate glycine, a potential acceptor for a myristoyl moiety. Metabolic labeling showed that cGK II was indeed able to incorporate [3H]myristate. Moreover, incubation of cGK II-expressing 293 cells with the myristoylation inhibitor 2-hydroxymyristic acid (1 mM) significantly increased the proportion of cGK II in the cytosol from 10 +/- 5 to 35 +/- 4%. Furthermore, a nonmyristoylated cGK II Gly2 --> Ala mutant was localized predominantly in the cytosol after transient expression in COS-1 cells. The absence of the myristoyl group did not affect the specific enzyme activity or the Ka for cGMP and only slightly enhanced the thermal stability of cGK II. These results indicate that N-terminal myristoylation fulfills a crucial role in directing cGK II to the membrane.
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PMID:N-terminal myristoylation is required for membrane localization of cGMP-dependent protein kinase type II. 863 33

Recombinant human cystic fibrosis transmembrane conductance regulator (CFTR) has been produced in a Saccharomyces cerevisiae expression system used previously to produce transport ATPases with high yields. The arrangement of the bases in the region immediately upstream from the ATG start codon of the CFTR is extremely important for high expression levels. The maximal CFTR expression level is about 5-10% of that in Sf9 insect cells as judged by comparison of immunoblots. Upon sucrose gradient centrifugation, the majority of the CFTR is found in a light vesicle fraction separated from the yeast plasma membrane in a heavier fraction. It thus appears that most of expressed CFTR is not directed to the plasma membrane in this system. CFTR expressed in yeast has the same mobility (ca. 140 kDa) as recombinant CFTR produced in Sf9 cells in a high resolution SDS-PAGE gel before and after N-glycosidase F treatment, suggesting that it is not glycosylated. The channel function of the expressed CFTR was measured by an isotope flux assay in isolated yeast membrane vesicles and single channel recording following reconstitution into planar lipid bilayers. In the isotope flux assay, protein kinase A (PKA) increased the rate of 125I- uptake by about 30% in membrane vesicles containing the CFTR, but not in control membranes. The single channel recordings showed that a PKA-activated small conductance anion channel (8 pS) with a linear I-V relationship was present in the CFTR membranes, but not in control membranes. These results show that the human CFTR has been expressed in functional form in yeast. With the reasonably high yield and the ability to grow massive quantities of yeast at low cost, this CFTR expression system may provide a valuable new source of starting material for purification of large quantities of the CFTR for biochemical studies.
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PMID:Functional expression of the cystic fibrosis transmembrane conductance regulator in yeast. 865 9


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