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1.
Microorganisms ; 11(2)2023 Jan 28.
Artigo em Inglês | MEDLINE | ID: mdl-36838290

RESUMO

Efficient hand hygiene is essential for preventing the transmission of microorganisms. Alcohol-based hand rub (ABHR) is a recommended method. We compared health personnel (skilled nurse students) with random adults to study the effect of an ABHR procedure. A water-based hand rub (WBHR) procedure, using running tap water and a hand-drying machine, was also investigated. The study included 27 nurse students and 26 random adults. Hands were contaminated with Escherichia coli, and concentrations of colony forming units (CFU/mL) were determined before and after ABHR or WBHR. Concentrations after ABHR were 1537 CFU/mL (nurse students) and 13,508 CFU/mL (random adults) (p < 0.001). One-third of participants reported skin irritation from daily ABHR. Concentrations after WBHR were 41 CFU/mL (nurse students) and 115 CFU/mL (random adults) (p < 0.011). The majority of participants (88.5%) preferred the WBHR method. Results from 50 air samples from filtered air from the hand dryer outlet showed no CFU in 47 samples. A significant difference between the two groups was shown for the ABHR method, indicating that training skills are important for efficient hand hygiene. Surprisingly, the WBHR method seemed to have a significant effect in largely removing transient bacteria from hands.

2.
J Occup Environ Hyg ; 17(10): 495-503, 2020 10.
Artigo em Inglês | MEDLINE | ID: mdl-32776824

RESUMO

The Internet of Things (IoT) explores new perspectives and possible improvements in risk assessment practices and shows potential to measure long-term and real-time occupational exposure. This may be of value when monitoring gases with short-term maximum levels and for time-weighted average (TWA) concentrations used in standard measuring practices. A functional embedded system was designed using low-cost carbon monoxide (CO) electrochemical sensors and long-range-wide-area-network radio communication technology (LoRaWAN) was used to enable internet connectivity. This system was utilized to monitor gas levels continuously in the working atmosphere of an incineration plant over a 2-month period. The results show that stable and long-term continuous data transfer was enabled by LoRaWAN, which proved useful for detecting rapid changes in gas levels. However, it was observed that raw data from the low-cost sensors did not meet the NIOSH accuracy criteria of ± 25% of the estimated true concentration based on field data from a co-located gas detector that met the NIOSH accuracy criteria. The new IoT technologies and CO sensor networks shows potential for remote monitoring of exposure in order to: (1) detect rapid changes in CO and other possible hazardous airborne gases; and (2) show the dynamic range of real-time data that may be hazardous for workers in the sampled areas. While the IoT low-cost sensors appear to be useful as a sentinel for monitoring hazardous atmospheres containing CO, the more useful finding may be showing real-time changes and the dynamic range of exposures, thus shedding light on the transient and toxic nature of airborne hazards. More importantly, the low-cost CO sensors are not a clear substitute for the more costly real-time gas detectors that perform within the NIOSH accuracy criteria.


Assuntos
Monóxido de Carbono/análise , Monitoramento Ambiental/métodos , Internet das Coisas , Exposição Ocupacional/análise , Poluentes Atmosféricos/análise , Monitoramento Ambiental/instrumentação , Incineração , Medição de Risco/métodos
3.
Cancer Genomics Proteomics ; 15(6): 437-446, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-30343277

RESUMO

BACKGROUND: Although methylation of the O6-methylguanine-DNA methyltransferase (MGMT) gene promoter predicts response to temozolomide in patients with glioblastoma, no consensus exists as to which assay is best for its detection. MATERIALS AND METHODS: Methylation of MGMT promoter was examined by methylation-specific polymerase chain reaction (MSP), quantitative real-time MSP, methylation-sensitive high-resolution melting analysis, and two commercial pyrosequencing (PSQ) kits. Survival was compared among 48 patients with glioblastoma according to assay results. RESULTS: Only PSQ and MSP significantly separated patients who benefited from temozolomide, with PSQ being the superior method. For PSQ analysis, the cut-off value that best correlated with prognostic outcome was 7% methylation of MGMT. Median survival in patients with MGMT promoter methylation above this cut-off value was 7.8 months longer compared to those with less than 7% methylation. Two-year overall survival for the two groups was 42% and 7.4%, respectively. CONCLUSION: PSQ is the method of choice for MGMT promoter methylation analysis in routine clinical practice.


Assuntos
Metilação de DNA , Metilases de Modificação do DNA , Enzimas Reparadoras do DNA , DNA de Neoplasias , Glioblastoma , Reação em Cadeia da Polimerase , Regiões Promotoras Genéticas , Kit de Reagentes para Diagnóstico , Análise de Sequência de DNA , Proteínas Supressoras de Tumor , Metilases de Modificação do DNA/genética , Metilases de Modificação do DNA/metabolismo , Enzimas Reparadoras do DNA/genética , Enzimas Reparadoras do DNA/metabolismo , DNA de Neoplasias/genética , DNA de Neoplasias/metabolismo , Feminino , Glioblastoma/genética , Glioblastoma/metabolismo , Glioblastoma/mortalidade , Glioblastoma/patologia , Humanos , Masculino , Valor Preditivo dos Testes , Proteínas Supressoras de Tumor/genética , Proteínas Supressoras de Tumor/metabolismo
4.
Cancer Genomics Proteomics ; 15(5): 379-385, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-30194078

RESUMO

BACKGROUND: Methylation of the O6-methylguanine-DNA methyltransferase (MGMT) gene promoter is a well-established predictor of response to the DNA-alkylating agent temozolomide in patients with glioblastoma. MATERIALS AND METHODS: Pyrosequencing analysis was used to determine the MGMT promoter methylation status in 61 meningiomas, to clarify whether it might have a predictive role. RESULTS: Only two tumors (3%) had a mean methylation frequency higher than the cut-off value of 10% for the four CpG sites examined. CONCLUSION: The methylation of the MGMT promoter is uncommon, or occurs at a low frequency in meningiomas. There is no convincing rationale to test such tumors for their MGMT methylation status in a clinical setting.


Assuntos
Metilação de DNA/genética , Metilases de Modificação do DNA/genética , Enzimas Reparadoras do DNA/genética , Meningioma/genética , Proteínas Supressoras de Tumor/genética , Adulto , Idoso , Feminino , Sequenciamento de Nucleotídeos em Larga Escala , Humanos , Masculino , Meningioma/patologia , Pessoa de Meia-Idade , Regiões Promotoras Genéticas/genética , Análise de Sequência de DNA
5.
Oncol Rep ; 36(5): 2653-2662, 2016 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-27667266

RESUMO

Fusion transcripts arising from the combination of exons residing on neighboring genes on the same chromosome may give rise to chimeric or novel proteins. Such read-through transcripts have been detected in different cancers where they may be of pathogenetic interest. In this study, we describe for the first time the expression of a read-through transcript in insulinomas, a functioning neuroendocrine pancreatic neoplasm. The read-through transcript INS-IGF2, composed of exons from the two genes proinsulin precursor (INS) and insulin­like growth factor 2 (IGF2), both mapping to chromosomal subband 11p15.5, was highly expressed in the two insulinomas analyzed. More precisely, version 2 of the INS-IGF2 transcript was expressed, indicating possible expression of the chimeric INS-IGF2 protein. We further identified a novel splice variant of the INS-IGF2 read-through transcript in one of the insulinomas, composed of exon 1 of INS3 and exons of IGF2. In the same tumor, we found high expression of INS3 and the presence of the A allele at SNP rs689. SNP rs689 has been previously described to regulate splicing of the INS transcript, indicating that this regulatory mechanism also affects splicing of INS-IGF2. The identification of the INS-IGF2 read-through transcript specifically in tumor tissue but not in normal pancreatic tissue suggests that high expression of INS-IGF2 could be neoplasia­specific. These results may have potential clinical applications given that the read-through transcript could be used as a biomarker in insulinoma patients.


Assuntos
Fator de Crescimento Insulin-Like II/genética , Insulina/genética , Insulinoma/genética , Isoformas de Proteínas/genética , Adulto , Alelos , Cromossomos Humanos Par 11/genética , Éxons/genética , Feminino , Regulação Neoplásica da Expressão Gênica , Humanos , Fator de Crescimento Insulin-Like II/biossíntese , Insulinoma/patologia , Masculino , Pâncreas/patologia , Polimorfismo de Nucleotídeo Único , Splicing de RNA/genética , Ativação Transcricional/genética
6.
Genes Chromosomes Cancer ; 55(11): 834-46, 2016 11.
Artigo em Inglês | MEDLINE | ID: mdl-27219024

RESUMO

Recent cytogenetic and molecular investigations have improved our understanding of endometrial stromal tumors, including sarcomas (ESS), and helped redefine their classification into more pathogenetically meaningful categories. Because much more can be gained through such studies, we add information on another 22 ESS examined by karyotyping, PCR analysis, expression array analysis, and transcriptome sequencing. In spite of the known preference for certain pathogenetic pathways, we found considerable genetic heterogeneity in high-grade (HG) as well as in low-grade (LG) ESS. Not all HG tumors showed a YWHAE-NUTM chimeric transcript and as many as six LGESS showed no hitherto known ESS-related fusions. Among the transcripts identified by transcriptome sequencing and verified by Sanger sequencing, new variants of ZC3H7-BCOR and its reciprocal BCOR-ZC3H7 were identified as was involvement of the CREBBP and MLLT4 genes (both well known leukemia-related genes) in two new fusions. FISH analysis identified a known EPC1-PHF1 fusion which led to the identification of a new variant at the molecular level. The fact that around 70 genes were found differentially expressed, by microarray analysis, when comparing LGESS showing ESS-related fusions with LGESS without such transcripts, underscores the biochemical importance of the observed genetic heterogeneity and hints that new subgroups/entities in LGESS still remain undiscovered. © 2016 The Authors. Genes, Chromosomes & Cancer Published by Wiley Periodicals, Inc.


Assuntos
Citogenética , Heterogeneidade Genética , Sarcoma do Estroma Endometrial/patologia , Transcriptoma/genética , Feminino , Regulação Neoplásica da Expressão Gênica , Humanos , Hibridização in Situ Fluorescente , Cariotipagem , Gradação de Tumores , Sarcoma do Estroma Endometrial/classificação , Sarcoma do Estroma Endometrial/genética
7.
PLoS One ; 8(2): e56671, 2013.
Artigo em Inglês | MEDLINE | ID: mdl-23409196

RESUMO

Dietary DNA is degraded into shorter DNA-fragments and single nucleosides in the gastrointestinal tract. Dietary DNA is mainly taken up as single nucleosides and bases, but even dietary DNA-fragments of up to a few hundred bp are able to cross the intestinal barrier and enter the blood stream. The molecular mechanisms behind transport of DNA-fragments across the intestine and the effects of this transport on the organism are currently unknown. Here we investigate the transport of DNA-fragments across the intestinal barrier, focusing on transport mechanisms and rates. The human intestinal epithelial cell line CaCo-2 was used as a model. As DNA material a PCR-fragment of 633 bp was used and quantitative real time PCR was used as detection method. DNA-fragments were found to be transported across polarized CaCo-2 cells in the apical to basolateral direction (AB). After 90 min the difference in directionality AB vs. BA was >10(3) fold. Even undegraded DNA-fragments of 633 bp could be detected in the basolateral receiver compartment at this time point. Transport of DNA-fragments was sensitive to low temperature and inhibition of endosomal acidification. DNA-transport across CaCo-2 cells was not competed out with oligodeoxynucleotides, fucoidan, heparin, heparan sulphate and dextrane sulphate, while linearized plasmid DNA, on the other hand, reduced transcytosis of DNA-fragments by a factor of approximately 2. Our findings therefore suggest that vesicular transport is mediating transcytosis of dietary DNA-fragments across intestinal cells and that DNA binding proteins are involved in this process. If we extrapolate our findings to in vivo conditions it could be hypothesized that this transport mechanism has a function in the immune system.


Assuntos
DNA/química , DNA/metabolismo , Transcitose , Vesículas Transportadoras/metabolismo , Adsorção , Células CACO-2 , Humanos , Fatores de Tempo
8.
Traffic ; 12(4): 507-20, 2011 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-21226813

RESUMO

The roles of EGF receptor (EGFR) kinase activity and ubiquitination in EGFR endocytosis have been controversial. The adaptor protein and ubiquitin ligase Cbl has reportedly been required. Consistently, we now report that siRNA-mediated knock-down of c-Cbl and Cbl-b significantly slowed clathrin-dependent internalization of activated wild-type (wt) EGFR by inhibiting recruitment of the EGFR to clathrin-coated pits. However, a chimeric protein consisting of wt-EGFR, a C-terminal linker and four linearly connected ubiquitins was found to interact with Eps15 and epsin 1 and to be constitutively endocytosed in a clathrin-dependent manner. Interestingly, endocytosis of this fusion protein did not require binding of EGF. Nor was kinase activity required, and the fusion protein was endocytosed in the presence of an EGFR kinase inhibitor, which efficiently counteracted tyrosine phosphorylation. This demonstrates that ubiquitination over-rides the requirement for kinase activity in recruitment of the EGFR to clathrin-coated pits.


Assuntos
Clatrina/metabolismo , Receptores ErbB/metabolismo , Proteínas Recombinantes de Fusão/metabolismo , Proteínas Adaptadoras de Transporte Vesicular/metabolismo , Células Cultivadas , Invaginações Revestidas da Membrana Celular/metabolismo , Endocitose/fisiologia , Endossomos/metabolismo , Fator de Crescimento Epidérmico/metabolismo , Receptores ErbB/genética , Técnicas de Inativação de Genes , Células HeLa , Humanos , Fosforilação , Ligação Proteica , Proteínas Proto-Oncogênicas c-cbl/genética , Proteínas Proto-Oncogênicas c-cbl/metabolismo , RNA Interferente Pequeno/administração & dosagem , RNA Interferente Pequeno/genética , Proteínas Recombinantes de Fusão/genética , Ubiquitinação , Ubiquitinas/genética , Ubiquitinas/metabolismo
9.
J Agric Food Chem ; 58(10): 6370-5, 2010 May 26.
Artigo em Inglês | MEDLINE | ID: mdl-20429587

RESUMO

A range of damaged nucleosides, also found in digested dietary DNA, appear to be taken up by cells and incorporated into the cells' own DNA. Most incorporated damaged nucleosides will be repaired by cellular DNA repair systems. However, a small fraction of these will escape repair and thus ultimately create mutations. Over the long human lifespan this could be a mechanism that contributes to disease, cancer, and aging. This study analyzed damaged nucleosides derived from dietary DNA in a commercially successful fungus-based novel food, Quorn, and in two fungus-based food items with a history of safe use, button mushroom ( Agaricus bisporus ) and dried powdered brewers yeast ( Saccharomyces cerevisiae ). By using liquid chromatography combined with tandem mass spectrometry more than 90 putative DNA adducts were measured, showing that foods do contain a range of different DNA damages.


Assuntos
Dano ao DNA , Análise de Alimentos , Nucleosídeos/efeitos adversos , Nucleosídeos/análise , Agaricus/química , Animais , Cromatografia Líquida , DNA/isolamento & purificação , Adutos de DNA/análise , DNA Fúngico/análise , Humanos , Saccharomyces cerevisiae/química , Espectrometria de Massas em Tandem
10.
Br J Nutr ; 103(1): 3-15, 2010 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-19706208

RESUMO

A 20-d zebrafish (Danio rerio) feeding trial, in which a near doubling of fish weight was achieved, was conducted with GM feed ingredients to evaluate feed intake, growth, stress response and uptake of dietary DNA. A partial aim of the study was to assess zebrafish as a model organism in GM safety assessments. Roundup Ready soya (RRS), YieldGard Bt maize (MON810) and their non-modified, maternal, near-isogenic lines were used in a 2 x 2 factorial design. Soya variety and maize variety were the main factors, both with two levels; non-GM and GM. Compared with fish fed non-GM maize, those fed GM maize exhibited significantly better growth, had lower mRNA transcription levels of superoxide dismutase (SOD)-1 and a tendency (non-significant) towards lower transcription of heat shock protein 70 in liver. Sex of the fish and soya variety had significant interaction effects on total RNA yield from the whole liver and transcription of SOD-1, suggesting that some diet component affecting males and females differently was present in different levels in the GM and the non-GM soya used in the present study. Dietary DNA sequences were detected in all of the organs analysed, but not all of the samples. Soya and maize rubisco (non-transgenic, multicopy genes) were most frequently detected, while MON810 transgenic DNA fragments were detected in some samples and RRS fragments were not detected. In conclusion, zebrafish shows promise as a model for this application.


Assuntos
Ração Animal/normas , DNA de Plantas/genética , DNA de Plantas/metabolismo , Peixe-Zebra/fisiologia , Criação de Animais Domésticos , Animais , Sequência de Bases , Primers do DNA , DNA de Plantas/análise , Desoxirribonucleases , Feminino , Masculino , Modelos Biológicos , Resíduos de Praguicidas/análise , RNA de Plantas/análise , RNA de Plantas/genética , Caracteres Sexuais , Glycine max , Zea mays , Peixe-Zebra/crescimento & desenvolvimento
11.
APMIS ; 117(7): 507-17, 2009 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-19594491

RESUMO

Human exposure to environmental microbes occurs regularly. Microbial compounds may interact with each other to affect cellular responses. We hypothesized that interactions between microbial compounds could modulate inflammatory cytokine responses in vitro. We investigated monocyte production of the pro-inflammatory cytokine tumour necrosis factor-alpha (TNF-alpha) and the regulatory cytokine interleukin-10 (IL-10) after combined exposure to the fungal cell wall polysaccharide mannan and to the beta-glucan laminarin, the mycotoxin citrinin and bacterial lipopolysaccharide (LPS). Interactions between the cell wall microbial compounds were estimated statistically in a general linear mixed model. We found that LPS (100 ng/ml) and the used beta-glucan (up to 1000 microg/ml) significantly interacted with each other to reduce TNF-alpha production. Mannan (up to 100 microg/ml) did not interact with the beta-glucan, but interacted with LPS. IL-10 production was induced by LPS only. The mycotoxin citrinin did not induce cytokine production, but was toxic to the cells in a dose- and time-dependent manner. However, non-toxic doses of citrinin reduced LPS-induced IL-10 production while LPS-induced TNF-alpha production was not similarly reduced by citrinin. In conclusion, interactions between microbial compounds can modulate cellular inflammatory cytokine production and experimental investigations of one compound at a time could give misleading conclusions about these combined effects.


Assuntos
Citrinina/imunologia , Lipopolissacarídeos/imunologia , Mananas/imunologia , Monócitos/imunologia , Polissacarídeos/imunologia , Fator de Necrose Tumoral alfa/biossíntese , Sobrevivência Celular , Parede Celular/imunologia , Citrinina/farmacologia , Ensaio de Imunoadsorção Enzimática , Glucanos , Humanos , Sistema Imunitário/efeitos dos fármacos , Interleucina-10/biossíntese , Interleucina-10/imunologia , Modelos Lineares , Lipopolissacarídeos/farmacologia , Mananas/farmacologia , Monócitos/efeitos dos fármacos , Polissacarídeos/farmacologia , Fator de Necrose Tumoral alfa/imunologia
12.
Exp Cell Res ; 314(6): 1292-300, 2008 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-18262180

RESUMO

The protein tyrosine kinase Ack1 has been linked to cancer when over-expressed. Ack1 has also been suggested to function in clathrin-mediated endocytosis and in down-regulation of the epidermal growth factor (EGF) receptor (EGFR). We have studied the intracellular localization of over-expressed Ack1 and found that Ack1 co-localizes with the EGFR upon EGF-induced endocytosis in cells with moderate over-expression of Ack. This co-localization is mainly observed in early endosomes. Furthermore, we found that over-expression of Ack1 retained the EGFR at the limiting membrane of early endosomes, inhibiting sorting to inner vesicles of multivesicular bodies. Down-regulation of Ack1 in HeLa cells resulted in reduced rate of (125)I-EGF internalization, whereas internalization of (125)I-transferrin was not affected. In cells where Ack1 had been knocked down by siRNA, recycling of internalized (125)I-EGF was increased, while degradation of (125)I-EGF was inhibited. Together, these data suggest that Ack1 is involved in an early step of EGFR desensitization.


Assuntos
Regulação para Baixo , Receptores ErbB/metabolismo , Proteínas Tirosina Quinases/metabolismo , Compartimento Celular , Clatrina/metabolismo , Clatrina/ultraestrutura , Endocitose , Endossomos/metabolismo , Endossomos/ultraestrutura , Fator de Crescimento Epidérmico/metabolismo , Células HeLa , Humanos , Radioisótopos do Iodo , Proteínas de Membrana/metabolismo , Transporte Proteico , Proteínas Tirosina Quinases/deficiência , Proteínas Tirosina Quinases/ultraestrutura , RNA Interferente Pequeno/metabolismo , Proteínas de Transporte Vesicular/metabolismo
13.
J Lipid Res ; 48(7): 1628-36, 2007 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-17452746

RESUMO

Sterol-regulatory element binding proteins (SREBPs) control the expression of genes involved in fatty acid and cholesterol biosynthesis. Using microarrays, we observed that mature SREBP-1 also induced the expression of genes unrelated to lipid metabolism, such as heme oxygenase 1 (HMOX1), plasma glutathione peroxidase, the phosphatidylinositol-3 kinase regulatory subunit p55 gamma, synaptic vesicle glycoprotein 2A, and COTE1. The expression of these genes was repressed upon addition of sterols, which block endogenous SREBP cleavage, and was induced by the statin drug mevinolin. Stimulation of fibroblasts with platelet-derived growth factor, which activates SREBP-1, had a similar effect. Fasted mice that were refed with a high-carbohydrate diet presented an increased expression of HMOX1 and p55 gamma in the liver. Overall, the transcriptional signature of SREBP-1 in fibroblasts stimulated by growth factors was very similar to that described in liver cells. We analyzed the HMOX1 promoter and found one SREBP binding site of the E-box type, which was required for regulation by SREBP-1a and SREBP-1c but was insensitive to SREBP-2. In conclusion, our data suggest that SREBP-1 regulates the expression of stress response and signaling genes, which could contribute to the metabolic response to insulin and growth factors in various tissues.


Assuntos
Regulação Enzimológica da Expressão Gênica , Heme Oxigenase-1/biossíntese , Fosfatidilinositol 3-Quinases/biossíntese , Proteína de Ligação a Elemento Regulador de Esterol 1/fisiologia , Animais , Linhagem Celular Tumoral , Fibroblastos/metabolismo , Humanos , Hidroxicolesteróis/farmacologia , Lovastatina/farmacologia , Masculino , Camundongos , Fator de Crescimento Derivado de Plaquetas/farmacologia , Regiões Promotoras Genéticas/fisiologia
14.
Traffic ; 7(11): 1518-27, 2006 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-16984407

RESUMO

Caveolae-dependent endocytosis has recently been proposed in the uptake of EGF receptor (EGFR) at high concentrations of ligand. Consistently, upon incubation of HEp2 and HeLa cells with methyl-beta-cyclodextrin, we observed a small inhibitory effect on endocytosis of ligated EGFR in HEp2 cells. However, immunoelectron microscopy showed the same relative amount of bound EGF localizing to caveolae on incubation with high and low concentrations of EGF, not supporting rapid recruitment of EGFR to caveolae. Live-cell microscopy furthermore demonstrated that incubating HEp2 cells with high concentrations of EGF did not increase the mobility of caveolae. By RNA-interference-mediated knockdown of clathrin heavy chain in HEp2 and HeLa cells, we found that endocytosis of EGFR was efficiently inhibited both at high and low concentrations of EGF. Our results show that caveolae are not involved in endocytosis of EGF-bound EGFR to any significant degree and that high concentrations of EGF do not further mobilize caveolae.


Assuntos
Cavéolas/fisiologia , Endocitose/fisiologia , Fator de Crescimento Epidérmico/farmacologia , Receptores ErbB/metabolismo , Cavéolas/efeitos dos fármacos , Caveolina 1/genética , Caveolina 1/metabolismo , Linhagem Celular Tumoral , Membrana Celular/efeitos dos fármacos , Membrana Celular/metabolismo , Toxina da Cólera/metabolismo , Cadeias Pesadas de Clatrina/genética , Cadeias Pesadas de Clatrina/metabolismo , Vesículas Revestidas por Clatrina/efeitos dos fármacos , Vesículas Revestidas por Clatrina/fisiologia , Invaginações Revestidas da Membrana Celular/metabolismo , Endocitose/efeitos dos fármacos , Fator de Crescimento Epidérmico/metabolismo , Recuperação de Fluorescência Após Fotodegradação , Células HeLa , Humanos , Nistatina/farmacologia , Ligação Proteica/efeitos dos fármacos , RNA Interferente Pequeno/genética , Transferrina/metabolismo , beta-Ciclodextrinas/farmacologia
15.
Mol Cell Biol ; 26(2): 389-401, 2006 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-16382132

RESUMO

In HeLa cells depleted of adaptor protein 2 complex (AP2) by small interfering RNA (siRNA) to the mu2 or alpha subunit or by transient overexpression of an AP2 sequestering mutant of Eps15, endocytosis of the transferrin receptor (TfR) was strongly inhibited. However, epidermal growth factor (EGF)-induced endocytosis of the EGF receptor (EGFR) was inhibited only in cells where the alpha subunit had been knocked down. By immunoelectron microscopy, we found that in AP2-depleted cells, the number of clathrin-coated pits was strongly reduced. When such cells were incubated with EGF, new coated pits were formed. These contained EGF, EGFR, clathrin, and Grb2 but not the TfR. The induced coated pits contained the alpha subunit, but labeling density was reduced compared to control cells. Induction of clathrin-coated pits required EGFR kinase activity. Overexpression of Grb2 with inactivating point mutations in N- or C-terminal SH3 domains or in both SH3 domains inhibited EGF-induced formation of coated pits efficiently, even though Grb2 SH3 mutations did not block activation of mitogen-activated protein kinase (MAPK) or phosphatidylinositol 3-kinase (PI3K). Our data demonstrate that EGFR-induced signaling and Grb2 are essential for formation of clathrin-coated pits accommodating the EGFR, while activation of MAPK and PI3K is not required.


Assuntos
Vesículas Revestidas por Clatrina/metabolismo , Receptores ErbB/metabolismo , Proteína Adaptadora GRB2/metabolismo , Fator de Transcrição AP-2/metabolismo , Clatrina/metabolismo , Vesículas Revestidas por Clatrina/ultraestrutura , Endocitose , Ativação Enzimática , Fator de Crescimento Epidérmico/metabolismo , Receptores ErbB/agonistas , Proteína Adaptadora GRB2/genética , Células HeLa , Humanos , Sistema de Sinalização das MAP Quinases/fisiologia , Microscopia Imunoeletrônica , Fosfatidilinositol 3-Quinases/metabolismo , Mutação Puntual , Subunidades Proteicas/genética , Subunidades Proteicas/metabolismo , RNA Interferente Pequeno/genética , Receptores da Transferrina/metabolismo , Transdução de Sinais , Fator de Transcrição AP-2/genética , Domínios de Homologia de src
16.
Mol Biol Cell ; 16(12): 5832-42, 2005 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-16207817

RESUMO

By constructing stably transfected cells harboring the same amount of epidermal growth factor (EGF) receptor (EGFR), but with increasing overexpression of ErbB2, we have demonstrated that ErbB2 efficiently inhibits internalization of ligand-bound EGFR. Apparently, ErbB2 inhibits internalization of EGF-bound EGFR by constitutively driving EGFR-ErbB2 hetero/oligomerization. We have demonstrated that ErbB2 does not inhibit phosphorylation or ubiquitination of the EGFR. Our data further indicate that the endocytosis deficiency of ErbB2 and of EGFR-ErbB2 heterodimers/oligomers cannot be explained by anchoring of ErbB2 to PDZ-containing proteins such as Erbin. Instead, we demonstrate that in contrast to EGFR homodimers, which are capable of inducing new clathrin-coated pits in serum-starved cells upon incubation with EGF, clathrin-coated pits are not induced upon activation of EGFR-ErbB2 heterodimers/oligomers.


Assuntos
Membrana Celular/fisiologia , Vesículas Revestidas por Clatrina/fisiologia , Endotélio Vascular/fisiologia , Fator de Crescimento Epidérmico/farmacologia , Receptores ErbB/fisiologia , Receptor ErbB-2/fisiologia , Animais , Aorta , Membrana Celular/efeitos dos fármacos , Vesículas Revestidas por Clatrina/efeitos dos fármacos , Vesículas Revestidas por Clatrina/ultraestrutura , Endotélio Vascular/citologia , Endotélio Vascular/efeitos dos fármacos , Fator de Crescimento Epidérmico/antagonistas & inibidores , Receptores ErbB/metabolismo , Humanos , Microscopia Confocal , Suínos
17.
J Cell Biol ; 156(5): 843-54, 2002 Mar 04.
Artigo em Inglês | MEDLINE | ID: mdl-11864992

RESUMO

EGF, but not TGF alpha, efficiently induces degradation of the EGF receptor (EGFR). We show that EGFR was initially polyubiquitinated to the same extent upon incubation with EGF and TGF alpha, whereas the ubiquitination was more sustained by incubation with EGF than with TGF alpha. Consistently, the ubiquitin ligase c-Cbl was recruited to the plasma membrane upon activation of the EGFR with EGF and TGF alpha, but localized to endosomes only upon activation with EGF. EGF remains bound to the EGFR upon endocytosis, whereas TGF alpha dissociates from the EGFR. Therefore, the sustained polyubiquitination is explained by EGF securing the kinase activity of endocytosed EGFR. Overexpression of the dominant negative N-Cbl inhibited ubiquitination of the EGFR and degradation of EGF and EGFR. This demonstrates that EGF-induced ubiquitination of the EGFR as such is important for lysosomal sorting. Both lysosomal and proteasomal inhibitors blocked degradation of EGF and EGFR, and proteasomal inhibitors inhibited translocation of activated EGFR from the outer limiting membrane to inner membranes of multivesicular bodies (MVBs). Therefore, lysosomal sorting of kinase active EGFR is regulated by proteasomal activity. Immuno-EM showed the localization of intact EGFR on internal membranes of MVBs. This demonstrates that the EGFR as such is not the proteasomal target.


Assuntos
Acetilcisteína/análogos & derivados , Cisteína Endopeptidases/metabolismo , Vesículas Citoplasmáticas/metabolismo , Fator de Crescimento Epidérmico/farmacologia , Receptores ErbB/metabolismo , Membranas Intracelulares/metabolismo , Complexos Multienzimáticos/metabolismo , Transporte Proteico/fisiologia , Ubiquitina-Proteína Ligases , Ubiquitinas/metabolismo , Acetilcisteína/farmacologia , Cloreto de Amônio/farmacologia , Animais , Membrana Celular/metabolismo , Membrana Celular/ultraestrutura , Cisteína Endopeptidases/efeitos dos fármacos , Cisteína Endopeptidases/ultraestrutura , Inibidores de Cisteína Proteinase/farmacologia , Vesículas Citoplasmáticas/ultraestrutura , Endocitose/efeitos dos fármacos , Endocitose/fisiologia , Endopeptidases/metabolismo , Receptores ErbB/efeitos dos fármacos , Receptores ErbB/ultraestrutura , Humanos , Imuno-Histoquímica , Membranas Intracelulares/ultraestrutura , Leupeptinas/farmacologia , Microscopia Confocal , Microscopia Eletrônica , Complexos Multienzimáticos/efeitos dos fármacos , Complexos Multienzimáticos/ultraestrutura , Inibidores de Proteases/farmacologia , Complexo de Endopeptidases do Proteassoma , Proteínas Proto-Oncogênicas/metabolismo , Proteínas Proto-Oncogênicas/farmacologia , Proteínas Proto-Oncogênicas c-cbl , Fator de Crescimento Transformador alfa/metabolismo
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