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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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152
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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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153
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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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154
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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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155
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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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156
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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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157
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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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158
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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: 397] [Impact Index Per Article: 12.0] [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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159
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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: 180] [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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160
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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: 487] [Impact Index Per Article: 14.8] [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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161
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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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162
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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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163
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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: 803] [Impact Index Per Article: 24.3] [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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164
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Rich DP, Gregory RJ, Anderson MP, Manavalan P, Smith AE, Welsh MJ. Effect of deleting the R domain on CFTR-generated chloride channels. Science 1991; 253:205-7. [PMID: 1712985 DOI: 10.1126/science.1712985] [Citation(s) in RCA: 190] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The cystic fibrosis transmembrane conductance regulator (CFTR), which forms adenosine 3',5'-monophosphate (cAMP)-regulated chloride channels, is defective in patients with cystic fibrosis. This protein contains two putative nucleotide binding domains (NBD1 and NBD2) and an R domain. CFTR in which the R domain was deleted (CFTR delta R) conducted chloride independently of the presence of cAMP. However, sites within CFTR other than those deleted also respond to cAMP, because the chloride current of CFTR delta R increased further in response to cAMP stimulation. In addition, deletion of the R domain suppressed the inactivating effect of a mutation in NBD2 (but not NBD1), a result which suggests that NBD2 interacts with the channel through the R domain.
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165
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Gyapong GJ, Jarvis NS, Watson DL, Bennett SJ, Freer M, Fulton BR, Murgatroyd JT, Hunt R, Rae WD, Smith AE. Near-symmetric breakup of 25Mg. PHYSICAL REVIEW. C, NUCLEAR PHYSICS 1991; 44:520-522. [PMID: 9967426 DOI: 10.1103/physrevc.44.520] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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166
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Smith AE, Lindner HJ. pi-SCF-molecular mechanics PIMM: formulation, parameters, applications. J Comput Aided Mol Des 1991; 5:235-62. [PMID: 1919619 DOI: 10.1007/bf00124341] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
A pi-SCF/Molecular Mechanics method (PIMM) for the calculation of heats of formation, molecular geometries and charge density distributions of organic molecules is described. The method combines a pi-SCF molecular orbital calculation and the sigma-charge evaluation procedure PEOE of Marsilli and Gasteiger with molecular mechanics. The formulas and parameters used are given. A series of results for small molecules is presented and compared with experimental data.
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167
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Scheidtmann KH, Buck M, Schneider J, Kalderon D, Fanning E, Smith AE. Biochemical characterization of phosphorylation site mutants of simian virus 40 large T antigen: evidence for interaction between amino- and carboxy-terminal domains. J Virol 1991; 65:1479-90. [PMID: 1847465 PMCID: PMC239928 DOI: 10.1128/jvi.65.3.1479-1490.1991] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
The simian virus 40 large T antigen is phosphorylated at eight or more sites that are clustered in an amino-terminal region and a carboxy-terminal region of the protein. Mutants carrying exchanges at these phosphorylation sites have been generated in vitro by bisulfite or oligonucleotide-directed mutagenesis and analyzed for their phosphorylation patterns. Two-dimensional phosphopeptide analyses of the mutant large T antigens confirmed most of the previously identified phosphorylation sites, namely, serine residues 106, 112, 123, 639, 677, and 679 and threonine residues 124 and 701. In addition, serine residue 120 was identified as a new site, whereas serines residues 111 and 676 were excluded. Interestingly, several of the mutants exhibited secondary effects in that a mutation in the amino-terminal region affected phosphorylation at distant and even carboxy-terminal sites and vice versa. Thus, the amino- and carboxy-terminal domains appear to be in close proximity in the three-dimensional structure of large T antigen. The possible consequences of the above findings and the role of phosphorylation are discussed.
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168
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Anderson MP, Rich DP, Gregory RJ, Smith AE, Welsh MJ. Generation of cAMP-activated chloride currents by expression of CFTR. Science 1991; 251:679-82. [PMID: 1704151 DOI: 10.1126/science.1704151] [Citation(s) in RCA: 418] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) cause cystic fibrosis. In order to evaluate its function, CFTR was expressed in HeLa, Chinese hamster ovary (CHO), and NIH 3T3 fibroblast cells, and anion permeability was assessed with a fluorescence microscopic assay and the whole-cell patch-clamp technique. Adenosine 3',5'-monophosphate (cAMP) increased anion permeability and chloride currents in cells expressing CFTR, but not in cells expressing a mutant CFTR (delta F508) or in nontransfected cells. The simplest interpretation of these observations is that CFTR is itself a cAMP-activated chloride channel. The alternative interpretation, that CFTR directly or indirectly regulates chloride channels, requires that these cells have endogenous cryptic, chloride channels that are stimulated by cAMP only in the presence of CFTR.
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169
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Cheng SH, Gregory RJ, Marshall J, Paul S, Souza DW, White GA, O'Riordan CR, Smith AE. Defective intracellular transport and processing of CFTR is the molecular basis of most cystic fibrosis. Cell 1990; 63:827-34. [PMID: 1699669 DOI: 10.1016/0092-8674(90)90148-8] [Citation(s) in RCA: 1325] [Impact Index Per Article: 39.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The gene associated with cystic fibrosis (CF) encodes a membrane-associated, N-linked glycoprotein called CFTR. Mutations were introduced into CFTR at residues known to be altered in CF chromosomes and in residues believed to play a role in its function. Examination of the various mutant proteins in COS-7 cells indicated that mature, fully glycosylated CFTR was absent from cells containing delta F508, delta 1507, K464M, F508R, and S5491 cDNA plasmids. Instead, an incompletely glycosylated version of the protein was detected. We propose that the mutant versions of CFTR are recognized as abnormal and remain incompletely processed in the endoplasmic reticulum where they are subsequently degraded. Since mutations with this phenotype represent at least 70% of known CF chromosomes, we argue that the molecular basis of most cystic fibrosis is the absence of mature CFTR at the correct cellular location.
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170
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Cheng SH, Espino PC, Marshall J, Harvey R, Smith AE. Stoichiometry of cellular and viral components in the polyomavirus middle-T antigen-tyrosine kinase complex. Mol Cell Biol 1990; 10:5569-74. [PMID: 1697932 PMCID: PMC361277 DOI: 10.1128/mcb.10.10.5569-5574.1990] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Our results indicate that only one type of tyrosine kinase is present within each middle-T antigen-tyrosine kinase complex, suggesting that middle-T antigen forms separate complexes with different tyrosine kinases. Furthermore, we determined that there is only one molecule of middle-T antigen within any one of these complexes. We interpret this to mean that in any given cell, polyomavirus transformation involves, at least in part, the simultaneous deregulation of a number of separate pathways controlling cellular proliferation. Finally, we also demonstrate that the separate middle-T:pp60c-src and middle-T:pp59c-fyn complexes are each able to interact with the same cellular p81/85-kDa phosphoprotein, a possible component of the phosphatidylinositol kinase.
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171
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Rich DP, Anderson MP, Gregory RJ, Cheng SH, Paul S, Jefferson DM, McCann JD, Klinger KW, Smith AE, Welsh MJ. Expression of cystic fibrosis transmembrane conductance regulator corrects defective chloride channel regulation in cystic fibrosis airway epithelial cells. Nature 1990; 347:358-63. [PMID: 1699126 DOI: 10.1038/347358a0] [Citation(s) in RCA: 455] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The cystic fibrosis transmembrane conductance regulator (CFTR) was expressed in cultured cystic fibrosis airway epithelial cells and Cl- channel activation assessed in single cells using a fluorescence microscopic assay and the patch-clamp technique. Expression of CFTR, but not of a mutant form of CFTR (delta F508), corrected the Cl- channel defect. Correction of the phenotypic defect demonstrates a causal relationship between mutations in the CFTR gene and defective Cl- transport which is the hallmark of the disease.
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172
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Gregory RJ, Cheng SH, Rich DP, Marshall J, Paul S, Hehir K, Ostedgaard L, Klinger KW, Welsh MJ, Smith AE. Expression and characterization of the cystic fibrosis transmembrane conductance regulator. Nature 1990; 347:382-6. [PMID: 1699127 DOI: 10.1038/347382a0] [Citation(s) in RCA: 281] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Cystic fibrosis (CF) is a common lethal genetic disease that manifests itself in airway and other epithelial cells as defective chloride ion absorption and secretion, resulting at least in part from a defect in a cyclic AMP-regulated, outwardly-rectifying Cl- channel in the apical surface. The gene responsible for CF has been identified and predicted to encode a membrane protein termed the CF transmembrane conductance regulator (CFTR). Identification of a cryptic bacterial promoter within the CFTR coding sequence led us to construct a complementary DNA in a low-copy-number plasmid, thereby avoiding the deleterious effects of CFTR expression on Escherischia coli. We have used this cDNA to express CFTR in vitro and in vivo. Here we demonstrate that CFTR is a membrane-associated glycoprotein that can be phosporylated in vitro by cAMP-dependent protein kinase. Polyclonal and monoclonal antibodies directed against distinct domains of the protein immunoprecipitated recombinant CFTR as well as the endogenous CFTR in nonrecombinant T84 cells. Partial proteolysis fingerprinting showed that the recombinant and non-recombinant proteins are indistinguishable. These data, which establish several characteristics of the protein responsible for CF, will now enable CFTR function to be studied and will provide a basis for diagnosis and therapy.
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173
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Thompson DL, Kalderon D, Smith AE, Tevethia MJ. Dissociation of Rb-binding and anchorage-independent growth from immortalization and tumorigenicity using SV40 mutants producing N-terminally truncated large T antigens. Virology 1990; 178:15-34. [PMID: 2167547 DOI: 10.1016/0042-6822(90)90375-2] [Citation(s) in RCA: 86] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The large T antigen of SV40 is both necessary and sufficient for conversion of primary mouse cells to cells with fully transformed phenotype. In this investigation, the influence of the N-terminal portion of T antigen on individual transformed cell characteristics was probed by using mutants bearing deletions in the 5'T antigen coding sequence. Specifically, DNA constructs expected to produce T antigens missing the first 109, 127, 150, or 176 amino acids or internal amino acid segments between 117 and 250 were tested for the ability to immortalize C57Bl/6 mouse embryo fibroblasts. The transformed cell properties displayed by clonally derived cell lines were then examined. The results indicated that neither the first 127 amino acids nor amino acids 127-250 of T antigen were necessary for efficient immortalization of primary cells or for their tumorigenicity. Functions mapped within these regions, including binding of the retinoblastoma susceptibility gene product (Rb) and transactivation of heterologous promoters, therefore, were not required to confer either of these growth properties. In addition the results showed that anchorage-independent growth was separable genetically from tumorigenicity and that removal of amino acids within the first 250 residues of T antigen compromised other transformed cell growth properties.
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174
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Abstract
Forty-three children born in the Nottingham area in 1981 and weighing less than 1501g who had received treatment in the neonatal intensive care unit were followed up on entry to primary school at the age of five years. All were apparently normal, with no observable handicap or need for special educational provision. Their results on the McCarthy Scales of Children's Abilities were compared with those of closely matched classmates and significant differences were found between the two groups on all six scales, most markedly on the General Cognitive Index.
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175
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Smith AE. The immorality of the United States tobacco industry. THE JOURNAL OF THE FLORIDA MEDICAL ASSOCIATION 1990; 77:445-6. [PMID: 2345355] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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