RESUMO
Plasma membranes derived from NR-6 cells, a variant line of Swiss mouse 3T3 cells that does not have cell surface receptors for epidermal growth factor (EGF), inhibited EGF-induced stimulation of DNA synthesis by 50% in serum-starved, subconfluent 3T3 cells. Membranes derived from SV3T3 cells were much less effective in inhibiting EGF-induced DNA synthesis. This inhibition on DNA synthesis by NR-6 membranes was not a direct effect of membranes on EGF, nor could it be overcome by high concentrations of EGF. NR-6 membranes were most effective when added 3 h before EGF addition and had little effect when added 2 h or more after EGF. NR-6 membranes also reduced the stimulation of DNA synthesis induced by platelet-derived growth factor or fibroblast growth factor in serum-starved 3T3 cells. These findings indicate that membrane-membrane interactions between nontransformed cells may diminish their ability to proliferate in response to serum polypeptide growth factors.
Assuntos
Ciclo Celular , Membrana Celular/fisiologia , Inibição de Contato , Inibidores do Crescimento , Animais , Células Cultivadas , Fator de Crescimento Epidérmico/farmacologia , Fatores de Crescimento de Fibroblastos/farmacologia , Camundongos , Fator de Crescimento Derivado de Plaquetas/farmacologiaRESUMO
Platelet-derived growth factor does not compete with epidermal growth factor (EGF) for binding to EGF receptors on the murine 3T3 cell surface, but it modulates EGF receptors in two ways: (i) it induces a transient down regulation of EGF receptors and (ii) it inhibits EGF-induced down regulation of EGF receptors. These data suggest a common cellular internalization mechanism for the receptors for both hormones.
Assuntos
Plaquetas/fisiologia , Fator de Crescimento Epidérmico/metabolismo , Substâncias de Crescimento/farmacologia , Peptídeos/metabolismo , Peptídeos/farmacologia , Receptores de Superfície Celular/efeitos dos fármacos , Animais , Ligação Competitiva , Linhagem Celular , Endocitose , Receptores ErbB , Camundongos , Fator de Crescimento Derivado de Plaquetas , Receptores de Superfície Celular/metabolismoRESUMO
Incubation of adherent human breast epithelial HBL100 cells with epidermal growth factor (EGF) decreased [3H]dexamethasone binding by 35% with no effect on affinity. Maximal inhibition was obtained at 3 nM EGF and the 50% effective dose was 0.2 nM EGF. Decreased dexamethasone binding induced by 3 nM EGF was maximal by 5 min of treatment and, in the continuous presence of EGF, persisted at a constant level over 4 days. The action of EGF was antagonized by 12-O-tetradecanoylphorbol-13-acetate, which did not inhibit dexamethasone binding significantly, and by concanavalin A. In homogenates of EGF-treated cells, decreased dexamethasone binding was observed only in the cytosolic fraction. Saturation dexamethasone binding inhibited the growth rate of HBL100 cells by approximately 50%, but concurrent treatment with EGF overcame this inhibition. The effect of EGF on dexamethasone-inhibited cell growth also was antagonized by 12-O-tetradecanoylphorbol-13-acetate.
Assuntos
Fator de Crescimento Epidérmico/farmacologia , Receptores de Glucocorticoides/metabolismo , Mama , Linhagem Celular , Concanavalina A/farmacologia , Citosol/metabolismo , Dexametasona/metabolismo , Dexametasona/farmacologia , Epitélio/metabolismo , Feminino , Humanos , Cinética , Receptores de Glucocorticoides/efeitos dos fármacos , Acetato de Tetradecanoilforbol/farmacologiaRESUMO
Specific progesterone binding by cultured human breast carcinoma T47D, MCF-7, and ZR75-1 cells was decreased 25-40% by epidermal growth factor (EGF), with a 50% effective dose of 0.1 nM EGF. Studies with the soluble and particulate fractions prepared after homogenization of T47D cells grown in glass roller bottles revealed equivalent EGF-induced decreases in progesterone binding to receptors in both fractions. Equilibrium progesterone binding studies with these soluble and particulate fractions revealed that EGF decreased the receptor number, but had no effect on affinity. With cells grown adherent to plastic dishes, EGF treatment induced a greater decrease in binding to receptors recovered in the particulate fraction, than to receptors recovered in the soluble fraction. The decrease in progesterone binding induced by 20 nM EGF was maximal after 2 min of cellular EGF treatment for receptors recovered in the soluble fraction, but was only half-maximal after 15 min for receptors recovered in the particulate fraction. Decreased progesterone binding persisted for at least 8 days in cells cultured with 1 nM EGF. Either insulin or EGF stimulated T47D cell proliferation by two- to threefold with a 50% effective dose of 100 nM for insulin and 0.1 nM for EGF. The progestin, R5020, decreased T47D cell growth by 30% with a 50% effective dose of 1 nM. Either EGF or insulin antagonized the inhibitory effect of R5020 on cell reproduction, but progestins did not antagonize the growth stimulatory response of cells to EGF. Progestins increased the number of EGF receptors within 12 h of their addition to T47D cells, but this response was lost after 6 days. These data show that EGF or progesterone can regulate the receptor number of the other, but for cell reproduction, the effect of EGF is dominant over that of progestins.
Assuntos
Neoplasias da Mama/metabolismo , Fator de Crescimento Epidérmico/farmacologia , Progesterona/metabolismo , Animais , Linhagem Celular , Feminino , Humanos , Insulina/farmacologia , Masculino , Camundongos , Promegestona/metabolismo , Receptores de Progesterona/metabolismo , Células Tumorais CultivadasRESUMO
An understanding of the biochemical basis of membrane function is an important goal of present day biology. In this paper, a biochemical approach to the problem of the specific transport of sugars across the membrane of Escherichia coli is discussed. A new biochemical model for lactose transport system in this organism is presented, in which a specific membrane protein (M protein) plays the role of the sugar carrier. Experiments which have led to the discovery of such a protein, its specific labeling, and partial purification are briefly reviewed.
Assuntos
Membrana Celular/fisiologia , Escherichia coli/metabolismo , Isótopos de Carbono , Glicosídeos/metabolismo , Lactose/metabolismo , Modelos Teóricos , Proteínas/fisiologia , TrítioRESUMO
The loss of epidermal growth factor (EGF) binding activity on cultured murine 3T3 cells exposed to EGF (EGF receptor down regulation) was determined in colchicine treated cells, cytochalasin B treated cells, and untreated cells. Neither colchicine nor cytochalasin B altered the affinity of the receptor for EGF, but colchicine decreased maximal EGF binding activity by 20%. The maximal extent of EGF receptor down regulation was similar in colchicine treated cells and cytochalasin B treated cells, but the rate of receptor down regulation was higher in cytochalasin B treated cells. Cytoplasts produced by subjecting cytochalasin B treated cells adhering to the substratum to centrifugal force responded to EGF with nearly normal down regulation kinetics. The results suggest that the cytoskeleton is not obligatorily involved in EGF-induced EGF receptor down regulation.
Assuntos
Citocalasina B/farmacologia , Fator de Crescimento Epidérmico/metabolismo , Peptídeos/metabolismo , Receptores de Superfície Celular/metabolismo , Animais , Núcleo Celular/fisiologia , Células Cultivadas , Colchicina/farmacologia , Receptores ErbB , Masculino , CamundongosRESUMO
The number of Rorschach achromatic perceptions of 10 male and 10 female hospitalized uni-polar depressed patients were compared with a control group of 10 male and 10 female hospitalized patients who held diagnoses other than depression or mania. The depressed patients gave significantly more achromatic perceptions than the non-depressed group. There was also a significant effect for sex and in interaction. The long held belief, based on clinical observation, that achromatic perceptions distinguish depressed from non-depressed individuals, was supported by this study. However, the intricacies of the results indicate that direct application in clinical work may be premature without further clarifying research.
Assuntos
Percepção de Cores , Depressão/diagnóstico , Teste de Rorschach , Adulto , Diagnóstico Diferencial , Feminino , Humanos , Masculino , Transtornos Mentais/diagnóstico , Fatores SexuaisAssuntos
Proteínas de Bactérias/biossíntese , Transporte Biológico , Glicosídeos/metabolismo , Lipídeos/biossíntese , Membrana Celular/metabolismo , Escherichia coli/metabolismo , Gorduras Insaturadas/metabolismo , Ácidos Graxos/metabolismo , Ácidos Linoleicos/metabolismo , Ácidos Oleicos/metabolismo , TemperaturaAssuntos
Antígenos CD/sangue , Plaquetas/fisiologia , Glicoproteínas de Membrana , Agregação Plaquetária , Glicoproteínas da Membrana de Plaquetas/fisiologia , Animais , Anticorpos Monoclonais/farmacologia , Antígenos CD/análise , Células CHO , Clonagem Molecular , Cricetinae , Citometria de Fluxo , Humanos , Agregação Plaquetária/efeitos dos fármacos , Glicoproteínas da Membrana de Plaquetas/análise , Proteínas Recombinantes/metabolismo , Tetraspanina 29 , TransfecçãoAssuntos
Corpo Humano , Nudismo , Escultura , Valores Sociais , Mulheres , Diversidade Cultural , Feminismo/história , História do Século XX , História do Século XXI , México/etnologia , Nudismo/história , Nudismo/psicologia , Opinião Pública/história , Escultura/educação , Escultura/história , Escultura/psicologia , Mudança Social/história , Valores Sociais/etnologia , Mulheres/educação , Mulheres/história , Mulheres/psicologiaRESUMO
Fifteen anorectic individuals were compared with a group of other psychiatric disorders with respect to the incidence of deviation in cognitive performance on a neuropsychological screening battery. A significant incidence of deviations in cognitive performance was found for the anorectic patients. The results are discussed in terms of possible neuropsychological implications that warrant future investigation.
Assuntos
Anorexia Nervosa/psicologia , Dano Encefálico Crônico/psicologia , Adulto , Transtornos Cognitivos/psicologia , Feminino , Humanos , Masculino , Transtornos Mentais/psicologiaRESUMO
The rate of derepressed synthesis of a membrane protein required for lactose transport (M protein) by Escherichia coli is increased in response to increased gene dosage to the same extent as the rates of synthesis of beta-galactosidase and galactoside acetylase. However, elevated gene dosage does not increase beta-galactoside transport to the same extent that it increases synthesis of M protein and of the soluble proteins of the lac operon. Though the factor or factors other than M protein which limit induction of the transport system at high levels of lac operon expression have not been identified, studies with Escherichia coli mutants blocked in the synthesis of unsaturated fatty acids indicate that unsaturated fatty acids must be supplied during the course of induction of the lac operon to permit synthesis of a functional lactose transport system, but not of beta-galactosidase or galactoside acetylase.
Assuntos
Escherichia coli/metabolismo , Ácidos Graxos/farmacologia , Lactose/metabolismo , Biologia Molecular , Transporte Biológico , Gorduras Insaturadas/farmacologia , ÓperonRESUMO
A mutation affecting unsaturated fatty acid biosynthesis in Escherichia coli has been mapped. This mutation, which is in the fabB locus, lies between the aroC and purF loci.
Assuntos
Mapeamento Cromossômico , Escherichia coli/metabolismo , Ácidos Graxos Essenciais/biossíntese , Genética Microbiana , Cruzamentos Genéticos , Meios de Cultura , Escherichia coli/crescimento & desenvolvimento , Mutação , Recombinação Genética , Transdução GenéticaRESUMO
A Mr = 34,000 protein present in the 100,000 X g supernatant fraction from A431 human epidermoid carcinoma cells is the major radiolabeled phosphate acceptor from [gamma-32P]ATP in a cell-free system requiring epidermal growth factor (EGF) and EGF receptor kinase. This protein is immunoprecipitated by IgG directed against avian Mr = 34,000 cellular substrate for pp60src. Phosphoamino acid analysis of the Mr = 34,000 protein labeled with 32Pi from [gamma-32P]ATP in a cell-free system requiring EGF and EGF receptor kinase yielded radiolabeled phosphotyrosine with no detectable radioactivity in phosphoserine or phosphothreonine.
Assuntos
Carcinoma de Células Escamosas/metabolismo , Fator de Crescimento Epidérmico/metabolismo , Proteínas de Neoplasias/metabolismo , Proteínas Quinases/metabolismo , Receptores de Superfície Celular/metabolismo , Linhagem Celular , Eletroforese em Gel de Poliacrilamida , Receptores ErbB , Humanos , Peso Molecular , Proteínas de Neoplasias/isolamento & purificação , Proteína Oncogênica pp60(v-src) , Fosforilação , Proteínas Virais/metabolismoRESUMO
Epidermal growth factor (EGF)-dependent transfer of radiolabeled phosphate from [gamma-32P]ATP to 160-kDa EGF receptor solubilized from human epidermoid carcinoma A431 cell surface membranes was stimulated up to 3-fold by addition of 3',5'-cAMP and purified cAMP-dependent protein kinase. Phosphorylation of EGF receptors was stimulated to the same extent when cAMP-dependent protein kinase catalytic subunit was substituted for 3',5'-cAMP and cAMP-dependent protein kinase. Phosphoamino acid analysis revealed that the extent of phosphorylation of EGF receptor at tyrosine residues was the same regardless of whether cAMP-dependent protein kinase catalytic subunit was present in or omitted from the system. Increased EGF receptor phosphorylation occurring in response to cAMP-dependent protein kinase catalytic subunit was accounted for by phosphorylation at serine or threonine residues. In samples phosphorylated in the presence of cAMP-dependent protein kinase catalytic subunit, phosphate was present in tyrosine, serine, and threonine in a ratio of 32:60:8. Two-dimensional mapping of radiolabeled phosphopeptides produced from EGF receptors by digestion with trypsin revealed the generation of one additional major phosphoserine-containing peptide when cAMP-dependent protein kinase was present with EGF in the EGF receptor kinase system. Degradation of 160-kDa EGF receptors to a 145-kDa form by purified Ca2+-activated neutral protease produced a 145-kDa fragment with phosphoserine content increased over that present initially in the 160-kDa precursor.
Assuntos
Fator de Crescimento Epidérmico/metabolismo , Proteínas Quinases/metabolismo , Receptores de Superfície Celular/metabolismo , Trifosfato de Adenosina/metabolismo , Carcinoma de Células Escamosas , Linhagem Celular , Eletroforese em Gel de Poliacrilamida , Fator de Crescimento Epidérmico/farmacologia , Receptores ErbB , Humanos , Peso Molecular , Fosfopeptídeos/análise , Fosforilação , Receptores de Superfície Celular/efeitos dos fármacos , Receptores de Superfície Celular/isolamento & purificaçãoRESUMO
When human epidermoid carcinoma A431 cells labeled with 32Pi to steady state specific activity were treated either with epidermal growth factor (EGF) or with active phorbol ester tumor promoters such as 12-O-tetradecanoylphorbol 13-acetate (TPA) or phorbol 12,13-dibutyrate, labeling of 160 kDa EGF receptors isolated by immunoprecipitation with monoclonal anti-EGF receptor IgG was increased 2- to 3-fold. These treatments produced no significant increase in 32Pi labeling of acid-precipitable material present in detergent extracts of the cells. Phosphoamino acid analysis of radiolabeled EGF receptors isolated from these cells revealed several differences: the relative abundance of phosphotyrosine in EGF receptors was increased in cells treated with EGF, but decreased in cells treated with TPA; the overall relative abundance of phosphothreonine in EGF receptors was decreased in cells treated with EGF, but remained constant within the limits of experimental detection in cells treated with TPA. Two-dimensional mapping of the radiolabeled phosphopeptides produced from EGF receptors isolated by immunoprecipitation and treated with trypsin revealed 9 independent labeled regions, 2 of which contained phosphothreonine and were present only in EGF- or TPA-treated cells. These two phosphopeptide regions were more highly labeled in cells treated with TPA than with EGF.
Assuntos
Carcinógenos/farmacologia , Carcinoma de Células Escamosas/metabolismo , Fator de Crescimento Epidérmico/farmacologia , Ésteres de Forbol/farmacologia , Forbóis/farmacologia , Receptores de Superfície Celular/metabolismo , Acetato de Tetradecanoilforbol/farmacologia , Linhagem Celular , Fator de Crescimento Epidérmico/metabolismo , Receptores ErbB , Humanos , Cinética , Fragmentos de Peptídeos/análise , Dibutirato de 12,13-Forbol , Fosforilação , Receptores de Superfície Celular/efeitos dos fármacos , Receptores de Superfície Celular/isolamento & purificaçãoRESUMO
Human breast epithelial HBL100 cells, which bind both epidermal growth factor (EGF) and glucocorticoids, were labelled to steady state specific activity with 32Pi and the glucocorticoid receptor was immunoprecipitated from cell lysates with polyclonal antiserum GR884. Immunoprecipitated receptor was resolved by NaDodSO4-polyacrylamide gel electrophoresis and identified by autoradiography. Immunoprecipitated receptor also was characterized by western blot analysis and affinity labelling with [3H]dexamethasone-21-mesylate. Phosphoamino acid analysis of 32P-glucocorticoid receptor revealed 89% phosphoserine and 11% phosphotyrosine. Treatment of steady state 32Pi-labelled cells with EGF stimulated total and alkali-stable phosphorylation in the 97 kDa receptor band by about 35%. Prior incubation with dexamethasone inhibited EGF stimulated, alkali-stable phosphorylation of the 97 kDa glucocorticoid receptor band.