151
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Smith AE. Get past the current cost focus and concentrate on outcomes. MODERN HEALTHCARE 1993; 23:32. [PMID: 10124745] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/11/2023]
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152
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Sheppard DN, Rich DP, Ostedgaard LS, Gregory RJ, Smith AE, Welsh MJ. Mutations in CFTR associated with mild-disease-form Cl- channels with altered pore properties. Nature 1993; 362:160-4. [PMID: 7680769 DOI: 10.1038/362160a0] [Citation(s) in RCA: 350] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The cystic fibrosis transmembrane conductance regulator (CFTR) is a phosphorylation-regulated Cl- channel located in the apical membrane of epithelia. Although cystic fibrosis (CF) is caused by mutations in a single gene encoding CFTR, the disease has a variable clinical phenotype. The most common mutation associated with cystic fibrosis, deletion of a phenylalanine at position 508 (frequency, 67%), is associated with severe disease. But some missense mutations, for example ones in which arginine is replaced by histidine at residue at 117 (R117H; 0.8%), tryptophan at 334 (0.4%), or proline at 347 (0.5%), are associated with milder disease. These missense mutations affect basic residues located at the external end of the second (M2) and in the sixth (M6) putative membrane-spanning sequences. Here we report that, when expressed in heterologous epithelial cells, all three mutants were correctly processed and generated cyclic AMP-regulated apical Cl- currents. Although the macroscopic current properties were normal, the amount of current was reduced. Patch-clamp analysis revealed that all three mutants had reduced single-channel conductances. In addition, R117H showed altered sensitivity to external pH and had altered single-channel kinetics. These results explain the quantitative decrease in macroscopic Cl- current, and suggest that R117, R334 and R347 contribute to the pore of the CFTR Cl- channel. Our results also suggest why R117H, R334W and R347P produce less severe clinical disease and have implications for our understanding of cystic fibrosis.
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153
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Younas M, Fuquay JW, Smith AE, Moore AB. Estrous and endocrine responses of lactating Holsteins to forced ventilation during summer. J Dairy Sci 1993; 76:430-6. [PMID: 8445097 DOI: 10.3168/jds.s0022-0302(93)77363-4] [Citation(s) in RCA: 50] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Fourteen lactating and cycling Holsteins in each of two summers were assigned randomly to pens in a free-stall barn either with or without overhead fans to study the effect of fan cooling on certain endocrine and behavioral responses during the estrous cycle. After an adjustment period of 8 d in the first summer and 21 d in the second summer, jugular cannulas were inserted, and 25 mg of PGF2 alpha were injected. After injection, blood samples were collected frequently for 84 h in the first summer and 88 h in the second summer, followed by collection three times weekly for 3 wk thereafter each summer. Rectal temperatures were lower in the group cooled by fans than in the control group each summer. Luteal progesterone secretion tended to be greater in the fan group each summer; area under the luteal phase curve was significantly higher than for controls during the second summer. There was tendency for more preovulatory surges of LH and higher estrous responses rates in the fan group during the second summer. Thus, fan cooling of lactating dairy cows for several weeks before anticipated breeding provides potential for more efficient reproductive performance during the summer.
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154
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Josefsson TW, Smith AE. Local-field Effects in the High-q-vector Dielectric Response of Si. ACTA ACUST UNITED AC 1993. [DOI: 10.1071/ph930635] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
The influence of microscopic or local fields on the full frequency- and wavevector-dependent dielectric loss function of Si has been calculated, based on accurate empirical pseudopotential calculations of the electronic structure. It is shown that local-field effects, dramatically significant at optical (q ~ 0) wavevectors, diminish with increasing magnitude of q to negligible proportions as q approaches the Brillouin zone boundary. In addition it is shown that the calculated volume-plasmon dispersion relation is improved in comparison with experimental results by the inclusion of local-field effects.
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155
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Smith AE, Kassab JY, Rowland Payne CM, Beer WE. Bimodality in age of onset of psoriasis, in both patients and their relatives. Dermatology 1993; 186:181-6. [PMID: 8453143 DOI: 10.1159/000247341] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
The ages at onset of 245 female and 211 male psoriasis (Ps) patients were recorded. The distribution of age of onset in both sexes is bimodal, with separation at the age of 40 years into an early-onset group and a late-onset group. These distributions were normal (Gaussian) with equal variances. These data are compatible with the hypothesis that there are two genotypes for Ps. Further evidence for this hypothesis is provided by the relationship between age of onset and number of affected relatives. The latter, corrected for age at time of study, demonstrates a mixture of two negative binomial distributions, also with likely separation at the age of 40 years. The age distribution of Ps patients reflects the bimodality of age of onset, but with larger means and variances.
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156
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Holben WE, Schroeter BM, Calabrese VG, Olsen RH, Kukor JK, Biederbeck VO, Smith AE, Tiedje JM. Gene probe analysis of soil microbial populations selected by amendment with 2,4-dichlorophenoxyacetic acid. Appl Environ Microbiol 1992; 58:3941-8. [PMID: 1476437 PMCID: PMC183208 DOI: 10.1128/aem.58.12.3941-3948.1992] [Citation(s) in RCA: 91] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Soils with a history of 2,4-dichlorophenoxyacetic acid (2,4-D) treatment at field application rates and control soils with no prior exposure to 2,4-D were amended with 2,4-D in the laboratory. Before and during these treatments, the populations of 2,4-D-degrading bacteria were monitored by most-probable-number (MPN) enumeration and hybridization analyses, using probes for the tfd genes of plasmid pJP4, which encode enzymes for 2,4-D degradation. Data obtained by these alternate methods were compared. Several months after the most recent field application of 2,4-D (approximately 1 ppm), soils with a 42-year history of 2,4-D treatment did not have significantly higher numbers of 2,4-D-degrading organisms than did control soils with no prior history of treatment. In response to laboratory amendments with 2,4-D, both the previously treated soils and those with no prior history of exposure exhibited a dramatic increase in the number of 2,4-D-metabolizing organisms. The MPN data indicate a 4- to 5-log population increase after one amendment with 250 ppm of 2,4-D and ultimately a 6- to 7-log increase after four additional amendments, each with 400 ppm of 2,4-D. Similarly, when total bacterial DNA from the soil microbial community of these samples was analyzed by using a probe for the tfdA gene (2,4-D monoxygenase) or the tfdB gene (2,4-dichlorophenol hydroxylase) a dramatic increase in the level of hybridization was observed in both soils.(ABSTRACT TRUNCATED AT 250 WORDS)
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157
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Smith AE, Smith PE. Reimbursement for clinical nutrition services: a 10-year experience. JOURNAL OF THE AMERICAN DIETETIC ASSOCIATION 1992; 92:1385-8. [PMID: 1430726] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Charges for nutrition products and services grew more than 800% between 1980 and 1990 at Children's Memorial Medical Center, Chicago, Ill. Three factors contributed to the growth in charges: distinguishing special services from those included in the bed charge, requiring rigorous documentation of services ordered and provided, and building administrative support for the program. Of the charges, 91% were related to nutrition support. The hospital converted 99% of the charges to private payers into actual revenue. The charge program provides the structure, discipline, and data to demonstrate the value of nutrition services for improving patient outcomes and may help sustain financial support even if the health care industry continues to move away from direct payment for services. Charging for nutrition products and services is a useful way for dietitians to document and be compensated for the value of their services in a hospital setting.
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158
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Whitsett JA, Dey CR, Stripp BR, Wikenheiser KA, Clark JC, Wert SE, Gregory RJ, Smith AE, Cohn JA, Wilson JM. Human cystic fibrosis transmembrane conductance regulator directed to respiratory epithelial cells of transgenic mice. Nat Genet 1992; 2:13-20. [PMID: 1284640 DOI: 10.1038/ng0992-13] [Citation(s) in RCA: 65] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Human cystic fibrosis transmembrane conductance regulator (CFTR) was expressed in transgenic mice under the control of transcriptional elements derived from the human surfactant protein C (SP-C) gene. The hCFTR mRNA was expressed in lungs and testes: in the lung, we found hCFTR mRNA in bronchiolar and alveolar epithelial cells, and CFTR protein in respiratory epithelial cells. While the level of expression of hCFTR mRNA varied, hCFTR mRNA and protein were detected in pulmonary epithelial cells of several lines. Lung weight, morphology, somatic growth and reproductive capacity were not altered by expression hCFTR in lung and testes of the transgenics. Our findings suggest that hCFTR can be safely transferred to lung epithelial cells for CF therapy.
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159
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Mant R, Asherson P, Gill M, McGuffin P, Owen M, Wert SE, Gregory RJ, Smith AE, Cohn JA, Wilson JM. Schizophrenia scepticism. Nat Genet 1992; 2:12. [PMID: 1303244 DOI: 10.1038/ng0992-12] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
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160
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Denning GM, Anderson MP, Amara JF, Marshall J, Smith AE, Welsh MJ. Processing of mutant cystic fibrosis transmembrane conductance regulator is temperature-sensitive. Nature 1992; 358:761-4. [PMID: 1380673 DOI: 10.1038/358761a0] [Citation(s) in RCA: 965] [Impact Index Per Article: 30.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Cystic fibrosis transmembrane conductance regulator (CFTR) is a plasma membrane Cl- channel regulated by cyclic AMP-dependent phosphorylation and by intracellular ATP. Mutations in CFTR cause cystic fibrosis partly through loss of cAMP-regulated Cl- permeability from the plasma membrane of affected epithelia. The most common mutation in cystic fibrosis is deletion of phenylalanine at residue 508 (CFTR delta F508) (ref. 10). Studies on the biosynthesis and localization of CFTR delta F508 indicate that the mutant protein is not processed correctly and, as a result, is not delivered to the plasma membrane. These conclusions are consistent with earlier functional studies which failed to detect cAMP-stimulated Cl- channels in cells expressing CFTR delta F508 (refs 16, 17). Chloride channel activity was detected, however, when CFTR delta F508 was expressed in Xenopus oocytes, Vero cells and Sf9 insect cells. Because oocytes and Sf9 cells are typically maintained at lower temperatures than mammalian cells, and because processing of nascent proteins can be sensitive to temperature, we tested the effect of temperature on the processing of CFTR delta F508. Here we show that the processing of CFTR delta F508 reverts towards that of wild-type as the incubation temperature is reduced. When the processing defect is corrected, cAMP-regulated Cl- channels appear in the plasma membrane. These results reconcile previous contradictory observations and suggest that the mutant most commonly associated with cystic fibrosis is temperature-sensitive.
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161
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Morris HL, Smith AE, Van Demark DR, Maves MD. Communication status following laryngectomy: the Iowa experience 1984-1987. Ann Otol Rhinol Laryngol 1992; 101:503-10. [PMID: 1610068 DOI: 10.1177/000348949210100611] [Citation(s) in RCA: 28] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Data regarding treatment and outcome for a consecutive series of 73 total laryngectomy patients were collected from clinical records with a follow-up period of 30 to 78 months postoperatively. Notable findings were that 27% were women; 75% reported hoarseness or a voice change as an early symptom; and 22% reported combined heavy use of both cigarettes and alcohol. Of the 73 patients, 38 (52%) died during the follow-up period; 18 of the 38 died within 1 year postoperatively. Thirty-nine (53%) of the 73 had received a surgical tracheoesophageal fistula (TEF) for voice restoration, as either a primary or a secondary procedure. Of the 39, 75% were using the TEF at last examination, with no failures attributed to sphincter spasm. Of the total group, the primary communication modality was reported to be use of a TEF by 44% and use of an electrolarynx by 50%. Limitations of the study and directions for future investigations are discussed.
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162
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Tilly BC, Winter MC, Ostedgaard LS, O'Riordan C, Smith AE, Welsh MJ. Cyclic AMP-dependent protein kinase activation of cystic fibrosis transmembrane conductance regulator chloride channels in planar lipid bilayers. J Biol Chem 1992; 267:9470-3. [PMID: 1374403] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Membrane vesicles, prepared from mouse NIH-3T3 fibroblasts and Chinese hamster ovary cells expressing high levels of cystic fibrosis transmembrane conductance regulator (CFTR), were fused with Mueller-Rudin planar lipid bilayers. Upon addition of the catalytic subunit of cAMP-dependent protein kinase and ATP, low conductance Cl(-)-selective ion channels were observed in 10 of 16 experiments. The channels had a linear current-voltage relationship and a unitary conductance of approximately 6.5 pS. The channels were more permeable to Cl- than to I- and showed no appreciable time-dependent voltage activation. In contrast, addition of cAMP-dependent protein kinase and ATP to lipid bilayers fused with vesicles prepared from mock transfected (n = 14) cells failed to activate Cl- channels. These data support the conclusion that CFTR is a Cl- channel. They indicate that it can be reconstituted in a planar lipid bilayer and that the biophysical and regulatory properties are very similar to those observed in the native cell membrane. These data also argue against the requirement for loosely associated factors for regulation or function of the channel.
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163
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Abstract
In 1979 formaldehyde was projected into the toxicological limelight when Kerns and his group from the American Chemical Industry Institute of Toxicology (CIIT) released preliminary results of an inhalation study on male and female rats. Those animals exposed to 14.3 p.p.m. for 8 h/day and 5 days/week for up to 2 years showed the development of squamous cell carcinomas in a high proportion (55 per cent) of the animals. Rats similarly exposed to 5.6 p.p.m. were slightly affected with 0.85 per cent producing tumours. The next 10 years became a frenzy of activity by toxicologists, epidemiologists and industry groups, all striving to answer the question: 'Is formaldehyde a human carcinogen?'. This paper will attempt to examine the extent to which the question has been answered. It will consider how the industry responded to the initial shock finding and review the subsequent accumulation of animal and human data. It will also address the regulatory position and compare the steps taken in different countries to control the risk, and again consider how industry has responded to such regulatory forces. This review will necessarily only be able to cover the main issues and major conclusions as the extent of the subject is enormous. There are, however, a number of comprehensive texts on the subject should more information be required.
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164
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Amara JF, Cheng SH, Smith AE. Intracellular protein trafficking defects in human disease. Trends Cell Biol 1992; 2:145-9. [PMID: 14731969 DOI: 10.1016/0962-8924(92)90101-r] [Citation(s) in RCA: 75] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Secretory proteins and integral membrane proteins travel through the secretory pathway to a variety of destinations. Their targets are often specified by signals in the amino acid sequence or signals added post-translationally. The KDEL sequence that retains soluble proteins in the endoplasmic reticulum and the mannose 6-phosphate group of lysosomal enzymes are well-characterized examples of targeting signals; other signals are less well understood. Given the complexity and importance of the intracellular trafficking pathways, it is perhaps not surprising that mutations that affect the trafficking of proteins are associated with some human genetic diseases.
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165
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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; 8:821-9. [PMID: 1375035 DOI: 10.1016/0896-6273(92)90196-k] [Citation(s) in RCA: 177] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
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166
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Denning GM, Ostedgaard LS, Cheng SH, Smith AE, Welsh MJ. Localization of cystic fibrosis transmembrane conductance regulator in chloride secretory epithelia. J Clin Invest 1992; 89:339-49. [PMID: 1370301 PMCID: PMC442854 DOI: 10.1172/jci115582] [Citation(s) in RCA: 189] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Cystic fibrosis is caused by mutations in the gene coding for the cystic fibrosis transmembrane conductance regulator (CFTR). To further our understanding of CFTR's function and regulation, we used confocal immunofluorescence microscopy to localize CFTR in cells stained with monoclonal antibodies against different regions of the protein: the R (regulatory) domain (M13-1), the COOH terminus (M1-4), and a predicted extracellular domain (M6-4). All three antibodies immunoprecipitated a 155-170-kD polypeptide from cells expressing CFTR. Each antibody stained HeLa and 3T3 cells expressing recombinant CFTR, but not cells lacking endogenous CFTR: HeLa, NIH-3T3, and endothelial cells. For localization studies, we used epithelial cell lines that express endogenous CFTR and have a cAMP-activated apical Cl- permeability: T84, CaCo2, and HT29 clone 19A. Our results demonstrate that CFTR is an apical membrane protein in these epithelial cells because (a) staining for CFTR resembled staining for several apical membrane markers, but differed from staining for basolateral membrane proteins; (b) thin sections of cell monolayers show staining at the apical membrane; and (c) M6-4, an extracellular domain antibody, stained the apical surface of nonpermeabilized cells. Our results do not exclude the possibility that CFTR is also located beneath the apical membrane. Increasing intracellular cAMP levels did not change the apical membrane staining pattern for CFTR. Moreover, insertion of channels by vesicle fusion with the apical membrane was not required for cAMP-mediated increases in apical membrane Cl- conductance. These results indicate that CFTR is located in the apical plasma membrane of Cl(-)-secreting epithelia, a result consistent with the conclusion that Cl TR is an apical membrane chloride channel.
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167
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Espino PC, Chou WY, Smith AE, Cheng SH. The amino-terminal half of pp59c-fyn contains sequences necessary for formation of a 75 kDa form and also repressive elements absent in pp60c-src. Oncogene 1992; 7:317-22. [PMID: 1372400] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/25/2023]
Abstract
Members of the src family of tyrosine kinases are composed of amino acid sequences which can be divided into three regions: the unique amino-terminal 80 residues; the next 180 residues of conserved but non-catalytic sequence; and the catalytic carboxy-terminal half of the molecule. To characterize the elements that regulate the catalytic and transforming activities of two members of this family, pp59c-fyn and pp60c-src, we generated six chimeric proteins by interchanging the three regions of the 531F mutant of pp59c-fyn and of the 527F mutant of pp60c-src. Our data indicate that substituting all or part of the amino-terminal 263 residues of pp59c-fyn for those of 527F inhibited the kinase and transforming activities of 527F. Conversely, substituting the amino-terminal half of pp60c-src for that of 531F resulted in an increase in the transforming potential of 531F. These results suggest that the amino-terminal half of pp59c-fyn contains elements which act to suppress the catalytic and transforming activities of the enzyme and that these suppressive elements are either absent or inactive in pp60c-src. These differences argue that the src family of tyrosine kinases are regulated differently in the cell. In vitro translation of some of the chimeras in rabbit reticulocyte lysates generated a 75 kDa protein in addition to the expected 59 kDa product. This 75 kDa species is analogous to the p75 protein previously detected in wild-type pp59c-fyn translation products. Interestingly, formation of p75 required the presence of DNA sequences encoding the unique amino-terminal residues of pp59c-fyn.
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168
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Beer WE, Smith AE, Kassab JY, Smith PH, Rowland Payne CM. Concomitance of psoriasis and atopic dermatitis. Dermatology 1992; 184:265-70. [PMID: 1482441 DOI: 10.1159/000247564] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
There is a widespread belief that psoriasis (Ps) and atopic dermatitis (AD) are clinically mutually exclusive. A prospective study was undertaken to record the concurrent and/or consecutive coincidence of the two conditions and any shared clinical features. Patients attending a dermatology clinic were systematically examined for the presence of Ps and/or AD. Nine hundred and eighty-three patients were studied--428 with Ps, 224 with AD, 45 with both Ps and AD, and 286 controls. Of AD patients 16.7% had Ps, and 9.5% of Ps patients had AD. In consecutive occurrences, Ps generally followed AD. The ratio of concurrent to consecutive incidences was 3:1. The two diseases are shown not to be mutually exclusive and may coexist in the same individual.
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169
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DiTullio P, Cheng SH, Marshall J, Gregory RJ, Ebert KM, Meade HM, Smith AE. Production of cystic fibrosis transmembrane conductance regulator in the milk of transgenic mice. BIO/TECHNOLOGY (NATURE PUBLISHING COMPANY) 1992; 10:74-7. [PMID: 1375475 DOI: 10.1038/nbt0192-74] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Here we describe the production of cystic fibrosis transmembrane conductance regulator (CFTR), the product of the gene associated with cystic fibrosis, in the milk of transgenic mice. Mammary specific expression was achieved by placing the CFTR cDNA under the control of the goat beta-casein gene promoter. By fractionation, CFTR was shown to be associated with the membranes that envelop milk fat globules as they are discharged from the apical surface of the mammary epithelia. Since milk fat globules may comprise up to 10% of whole milk, this represents a novel, inexpensive and efficient approach to produce CFTR and possibly other membrane-associated proteins. The availability of large quantities of CFTR could have important implications for the development of new therapies for cystic fibrosis.
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170
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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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171
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Berger HA, Anderson MP, Gregory RJ, Thompson S, Howard PW, Maurer RA, Mulligan R, Smith AE, Welsh MJ. Identification and regulation of the cystic fibrosis transmembrane conductance regulator-generated chloride channel. J Clin Invest 1991; 88:1422-31. [PMID: 1717515 PMCID: PMC295615 DOI: 10.1172/jci115450] [Citation(s) in RCA: 181] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Cystic fibrosis transmembrane conductance regulator (CFTR) generates cAMP-regulated Cl- channels; mutations in CFTR cause defective Cl- channel function in cystic fibrosis epithelia. We used the patch-clamp technique to determine the single channel properties of Cl- channels in cell expressing recombinant CFTR. In cell-attached patches, an increase in cellular cAMP reversibly activated low conductance Cl- channels. cAMP-dependent regulation is due to phosphorylation, because the catalytic subunit of cAMP-dependent protein kinase plus ATP reversibly activated the channel in excised, cell-free patches of membrane. In symmetrical Cl- solutions, the channel had a channel conductance of 10.4 +/- 0.2 (n = 7) pS and a linear current-voltage relation. The channel was more permeable to Cl- than to I- and showed no appreciable time-dependent voltage effects. These biophysical properties are consistent with macroscopic studies of Cl- channels in single cells expressing CFTR and in the apical membrane of secretory epithelia. Identification of the single channel characteristics of CFTR-generated channels allows further studies of their regulation and the mechanism of ion permeation.
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172
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Cheng SH, Rich DP, Marshall J, Gregory RJ, Welsh MJ, Smith AE. Phosphorylation of the R domain by cAMP-dependent protein kinase regulates the CFTR chloride channel. Cell 1991; 66:1027-36. [PMID: 1716180 DOI: 10.1016/0092-8674(91)90446-6] [Citation(s) in RCA: 493] [Impact Index Per Article: 14.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
CFTR, the protein associated with cystic fibrosis, is phosphorylated on serine residues in response to cAMP agonists. Serines 660, 737, 795, and 813 were identified as in vivo targets for phosphorylation by protein kinase A. The SPQ fluorescence assay revealed that mutagenesis of any one of these sites did not affect Cl- channel activity. Indeed, concomitant mutagenesis of three of the four sites still resulted in cAMP-responsive Cl- channel activity. However, mutagenesis of all four sites abolished the response. One interpretation of these results is that the CFTR Cl- channel is blocked by the R domain and that phosphorylation on serines by protein kinase A electrostatically repels the domain, allowing passage of Cl-. The four phosphorylation events appear to be degenerate: no one site is essential for channel activity, and, at least in the case of serine 660, phosphorylation at one site alone is sufficient for regulation of Cl- channel activity.
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173
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Marshall J, Smith AE, Cheng SH. Monoclonal antibody specific for BK virus large-T antigen allows discrimination among the different papovaviral large-T antigens. Oncogene 1991; 6:1673-6. [PMID: 1656370] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The human papovaviruses BK virus (BKV) and JC virus (JCV) both encode a large-tumor (T) antigen which are highly homologous to each other as well as to simian virus 40 (SV40) large-T antigen. This high conservation of amino acid sequence has resulted in overlapping antigenicity such that immunological differentiation of the large-T antigens from the three different viruses has been difficult. Here we describe the generation and characterization of a new monoclonal antibody (BK-T.1) which is specific for BKV large-T antigen and which does not cross-react with the other papovaviral T antigens. We show that when BK-T.1 is used in conjunction with preexisting monoclonal antibodies against SV40 large-T antigen, it is possible to identify the origin of papovavirus T antigens.
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174
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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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Anderson MP, Gregory RJ, Thompson S, Souza DW, Paul S, Mulligan RC, Smith AE, Welsh MJ. Demonstration that CFTR is a chloride channel by alteration of its anion selectivity. Science 1991; 253:202-5. [PMID: 1712984 DOI: 10.1126/science.1712984] [Citation(s) in RCA: 808] [Impact Index Per Article: 24.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Expression of the cystic fibrosis transmembrane conductance regulator (CFTR) generates adenosine 3',5'-monophosphate (cAMP)-regulated chloride channels, indicating that CFTR is either a chloride channel or a chloride channel regulator. To distinguish between these possibilities, basic amino acids in the putative transmembrane domains were mutated. The sequence of anion selectivity of cAMP-regulated channels in cells containing either endogenous or recombinant CFTR was bromide greater than chloride greater than iodide greater than fluoride. Mutation of the lysines at positions 95 or 335 to acidic amino acids converted the selectivity sequence to iodide greater than bromide greater than chloride greater than fluoride. These data indicate that CFTR is a cAMP-regulated chloride channel and that lysines 95 and 335 determine anion selectivity.
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