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1.
Lectins that interact with mannose (concanavalin A), galactose (ricin, abrin), or N-acetylglucosamine (wheat germ agglutinin) block 125I-labeled EGF binding to the surface of cultured human fibroblasts at 37° or 5°. Lectins specific for fucose or N-acetylgalactosamine, soybean agglutinin or gorse lectin, respectively, do not interfere with growth factor binding. The inhibition of 125I-labeled EGF binding by concanavalin A at 37° or 5° could be reversed rapidly by the addition of α-methyl mannoside. The results suggest that the fibroblast membrane receptor for EGF is, or is closely associated with, a glycoprotein or glycolipid that contains mannose, galactose and N-acetylglucosamine residues. 相似文献
2.
Tatsuomi Yasaka Takeshi Kambara 《Biochimica et Biophysica Acta (BBA)/General Subjects》1979,585(2):229-239
The effects of tetravalent concanavalin A and its succinylated derivative on the intracellular production of superoxide anion (O2?) and its release into cell exterior of peritoneal macrophages were observed. Both tetravalent concanavalin A and its succinylated derivative induced marked enhancement of intracellular reduction of nitroblue tetrazolium, which could be inhibited by α-methyl-D-glucoside. The extent of activation of nitroblue tetrazolium reduction induced by both types of the lectin paralleled the activation ratio of oxygen consumption.There was littele difference in the extent of intracellular O2? production induced by two types of the lectin. Nitroblue tetrazolium reduction was not affected significantly by pretreatment with colchicine, rotenone or malonate, inhibitors of the cytoskeletal system and of the electron transport system. In contrast, tetravalent concanavalin A induced a higher rate of superoxide release than did succinylated divalent concanavalin A, which lacks the cross-linking activity of surface glycoproteins.These results indicate that superoxide production following oxygen consumption and superoxide release into cell exterior are controlled independently by a separate membrane mechanism and that superoxide production system is not essentially dependent on the involvement of the cytoskeletal system. 相似文献
3.
Robert A. Robinson Mary E. Volkenant Robert J. Ryan Harold L. Moses 《Journal of cellular physiology》1981,109(3):517-524
Previous studies have shown that the nontransformed AKR-2B mouse embryo derived cell line may growth arrest by two separate mechanisms in the G1 phase of the cell cycle-growth factor deficiency arrest (G0) and low molecular weight nutrient deficiency arrest. An examination of epidermal growth factor (EGF) receptors under the different resting or growth conditions has shown that rapidly growing cells or cells arrested due to growth factor deficiency have the expected amount of 125I-EGF binding with approximately 105 receptors per cell being present in G0 arrested cells. In contrast, cells arrested due to nutrient deficiency show a reduction in 125I-EGF binding to 10--20% of that observed under the other conditions. This effect appears to be due to decreased receptor number and not to a change in the affinity of the receptor. Stimulation of DNA synthesis by nutrient replenishment causes a tenfold increase in EGF binding 20 hours later, with some increase in binding being detectable as early as six hours. The increase in binding is inhibited by cycloheximide and actinomycin D. This suggests that new mRNA synthesis as well as increased protein synthesis is required for the increase in EGF binding. 相似文献
4.
The PC12 cell line displays cell surface receptors for both nerve growth factor (NGF) and epidermal growth factor (EGF). It has been previously shown that the lectin wheat germ agglutinin (WGA) alters the properties of NGF receptors on these cells. We now report that preincubations with either WGA or concanavalin A (Con A) decrease the binding of 125I-EGF to PC12 cells by greater than 50%. The inhibition of binding occurred at 37°C and 4°C and could be blocked or reversed by the addition of sugars which bind specifically to WGA or Con A. Scatchard analysis revealed that these lectins decreased binding primarily by lowering the affinity of the receptor and to a lesser extent by decreasing receptor number. Succinylalion of Con A (sCon A) produced a derivative that was less effective than the native lectin in decreasing EGF binding; however, addition of an antibody against Con A restored the ability of sCon A to decrease binding. Similar to results obtained with 125I-NGF binding, WGA but not Con A was found to increase, by scveralfold; the proportion of 125I-EGF binding that is resistant to solubilization by Triton X-100 detergent. A potential association of the EGF receptor with cytoskeletal elements is discussed which could account for such results. 相似文献
5.
The effects of epidermal growth factor (EGF) were studied in rat pituitary tumor cells, GH3, grown in serum-supplemented and serum-free chemically defined media. EGF (1 nM) increased the cell number to 132% of the control cultured in the defined medium during a 6-day incubation period, while it decreased the cell number to 60% of the control in the serum-supplemented medium. EGF altered the morphology of the cells grown in the defined medium more markedly to an elongated conformation than that of cells grown in the serum-supplemented medium. EGF also stimulated prolactin (PRL) production by culture in the presence or absence of serum. The effects of the cell density of GH3 on the action of EGF were shown to appear in two ways. The mitogenic influence of EGF was more effective on, and more responsive to, high-density cells, whereas the stimulatory action on PRL production was less effective on high-density cells. However, the inhibitory effects on cellular growth appeared independently of cell densities. The results obtained with 125I-EGF binding experiments indicated that the number of binding sites, affinity, and internalization of EGF receptors were similar in either serum-supplemented or serum-free culture. At low cell density, the number of available 125I-EGF binding sites per cell was larger than at high cell density. These results suggested that there was no apparent correlation between EGF binding and its differing effects on the growth of GH3 cultured in the serum-supplemented and the defined medium. 相似文献
6.
Summary The hybrid GH cell strain, 928-9b, isolated from PRL+ (prolactin [PRL] producing) GH4Cl and PRL (PRL non-producing) FIBGH12CI cells, has specific TRH (thyroliberin) receptors, yet does not respond to this peptide hormone. Unlike the parent strain, GH4Cl, TRH does not stimulate synthesis or release of PRL in the hybrid strain. In contrast, treatment of 928-9b cells with another peptide, EGF (epidermal growth factor), stimulates both release and synthesis of PRL. The number of EGF receptors in the hybrid strain (2.5 × 103/cell) and the affinity of these receptors for ligand (2.2 nM) are comparable to that of the parent strain, GH4C1. The EGF dose response curve is also essentially the same for parent and hybrid cells for the enhancement of PRL production. A 3-8-fold enhancement of PRL production is observed and 1/2 maximal enhancement occurs at approximately 5 × 1011 M EGF for both strains. TRH does not have any potentiating effect on EGF-induced stimulation of PRL release or PRL synthesis in the hybrid strain. Although EGF and TRH have similar biological effects in responsive GH cells, binding of one hormone to its receptors does not modulate the binding of the heterologous hormone. These findings demonstrate that more than one effect of TRH is defective in 928-9b cells even though EGF responses are intact. This suggests that 1) TRH-stimulated PRL release and TRH-stimulated PRL production have a common intermediate step, and 2) TRH and EGF have a different mechanism of action in GH cells. 相似文献
7.
The addition of the glucocorticoid analog dexamethasone (DX) to serum-free cultures of human fibroblasts caused a twofold enhancement of the mitogenic response to epidermal growth factor (EGF), although DX by itself was not mitogenic. A basis for this effect was suggested by studies showing that DX also increased the cellular binding of 125I-EGF. DX increased the ability of the cells to bind 125I-EGF only at low physiological concentrations of this polypeptide. Thus, data from 125I-EGF binding to cells incubated without DX produced a linear Scatchard plot, whereas the data from 125I-EGF binding to DX-treated cells led to an upwardly curvilinear Scatchard plot. Measurements of 125I-EGF association with the cell surface and cytoplasm indicated that this binding change involved an alteration of cell surface EGF receptors. The binding change appeared not to involve negatively cooperative interactions between EGF receptors, nor a change in the number of receptors. The binding alteration could be explained by a model in which DX converted 25–30% of the cell surface EGF receptors to a form having a fourfold increased affinity. 相似文献
8.
The ability of insulin and epidermal growth factor (EGF) to restore cell surface function in cells damaged by serum deprivation has been examined. Both insulin (10?7 M) and EGF (10?8 M), when added for 2 h, resulted in reattachment of cells to the culture dish; with insulin, attachment was associated with increased amino acid uptake. Both hormones caused an increase in sialic acid and in free sulfhydryl groups associated with the cell membrane. The mobility of concanavalin A (Con A) on the upper cell surface was increased by EGF, and to a lesser extent by insulin. The effects of insulin and EGF on adhesion appear to be regulated by specific receptors for these hormones. 相似文献
9.
Lowering of extracellular Ca2+ levels will reversibly arrest the growth of human fibroblasts (WI38). Simian virus40(SV40)-transformed WI38 cells do not exhibit this Ca2+-dependent arrest. One possibility for this difference in Ca2+ requirement is that extracellular or surface membrane-bound Ca2+ may be required for growth factor receptor-mediated endocytosis and this Ca2+ requirement may differ in normal versus transformed cells. In this study we have evaluated the role of Ca2+ in the binding, internalization, and degradation of epidermal growth factor (EGF) in the WI38 and SV40 WI38 cell. The binding of [125I]EGF to the cell surface is not significantly altered by lowering of Ca2+ to 10?5-M levels in either the normal or transformed cell. At this Ca2+ level, growth of the normal cell is inhibited. The subsequent internalization of EGF is reduced nearly threefold in the normal cell but not in the transformed cell following Ca2+ deprivation. Degradation of the EGF-receptor complex is also sensitive to Ca2+. A twofold reduction in the rate of release of acid-soluble 125I occurs in the normal but not the transformed cell under conditions of lowered medium Ca2+. In contrast, 2-chloro-10-3-aminopropyl phenothiazine (CP), an inhibitor of the Ca2+-dependent regulator protein calmodulin, causes an inhibition of [125I]EGF internalization and degradation in both the normal and transformed WI38 cell, and a marked inhibition of [125I]EGF binding to the cell surface receptor of the transformed cell but not the normal cell. 相似文献
10.
Archana S. Wagle Varsha Patki Shefali J. Desai Rita Mulherkar 《Journal of biosciences》1997,22(5):537-543
Enhancing factor (EF), a mouse intestinal phospholipase A2 (PLA2), has been isolated and characterized. EF increases the binding of epidermal growth factor (EGF) to A431 cells almost two-fold
by interacting with EGF. EF binds to a 100 kDa cell surface receptor and brings about an increase in the binding of EGF. In
the present study we demonstrate that EF is a heparin binding protein and at the time of iodination of EF, the heparin binding
site of EF has to be protected. Heparin inhibits the enhancing activity of EF as well as the binding of labelled EF to A431
cells. Inhibition of binding of EF to cells by heparin indicates that heparin binding region forms at least part of the receptor
binding domain. These data suggest that the receptor for EF on the cell surface could be a heparin sulphate proteoglycan. 相似文献
11.
Michiko Saito Ikuko Ueno Kohji Egawa 《Biochimica et Biophysica Acta (BBA)/General Subjects》1982,717(2):301-304
Binding of 125I-labelled epidermal growth factor (EGF) to C3H/2K cells and the effect of a tumor promotor, 12-O-tetradecanoyl phorbol-13-acetate (TPA) and of a tumor promotor antagonist, retinoic acid, on the binding was studied. Scatchard plot analysis of the binding showed the presence of two type of binding sites with different affinity to EGF. Treatment of the cells with retinoic acid for 1 h resulted in elevation of the affinity of both sites without changing their number per cell. Prolonged exposure to retinoic acid abrogated this elevation of the affinity and caused cycloheximide-sensitive increase of the number of the binding sites of both types. TPA inhibited binding of EGF to the cells by abolishing the binding to the high affinity sites, whereas retinoic acid, in the presence of TPA, enhanced it by increasing the number of the low affinity sites. 相似文献
12.
The interaction of the epidermal growth factor (EGF) with its receptor (EGFR) is known to be complex, and the common over-expression of EGF receptor family members in a multitude of tumors makes it important to decipher this interaction and the following signaling pathways. We have investigated the affinity and kinetics of 125I-EGF binding to EGFR in four human tumor cell lines, each using four culturing conditions, in real time by use of LigandTracer®.Highly repeatable and precise measurements show that the overall apparent affinity of the 125I-EGF – EGFR interaction is greatly dependent on cell line at normal culturing conditions, ranging from KD≈200 pM on SKBR3 cells to KD≈8 nM on A431 cells. The 125I-EGF – EGFR binding curves (irrespective of cell line) have strong signs of multiple simultaneous interactions. Furthermore, for the cell lines A431 and SKOV3, gefitinib treatment increases the 125I-EGF - EGFR affinity, in particular when the cells are starved. The 125I-EGF - EGFR interaction on cell line U343 is sensitive to starvation while as on SKBR3 it is insensitive to gefitinib and starvation.The intriguing pattern of the binding characteristics proves that the cellular context is important when deciphering how EGF interacts with EGFR. From a general perspective, care is advisable when generalizing ligand-receptor interaction results across multiple cell-lines. 相似文献
13.
Ted Gansler Wei-Chao Hsu T. Stokes Gramling Katherine A. Robinson Maria G. Buse Ned Blocker Linda Roy Sadie Green A. Julian Garvin Donald A. Sens 《In vitro cellular & developmental biology. Plant》1990,26(3):285-290
Summary Insulinlike growth factors (IGF) and epidermal growth factor (EGF) are produced in renal tissue, as are specific receptors
for these hormones. To evaluate the significance of these observations to regulation of renal tubular cell proliferation,
we have examined the interaction of IGF and EGF with cultured human proximal tubular epithelial cells (HPT). HPT cells showed
specific binding of IGF-1, insulin, and EGF. IGF-1 binding was inhibited by antibody to the type 1 IGF receptor (α-IR3). Insulin
receptors and type 1 IGF receptors were identified by bifunctional cross-linking. IGF-1, insulin, and EGF stimulated [3H]thymidine incorporation by 77, 73, and 87%, respectively. Haft maximal stimulation by IGF-1, insulin, and EGF was produced
with 4×10−9
M, 2.5×10−8
M, and 8×10−10
M concentrations of these hormones. α-IR3 inhibited stimulation of thymidine incorporation by IGF-1 and insulin but had no
effect in EGF-stimulated thymidine incorporation. EGF and high concentrations of insulin both stimulated cell proliferation
by 83 and 79%, respectively. These data are consistent with regulation of tubular epithelial proliferation by IGF-1, insulin,
and EGF and suggest that the mitogenic activity of both insulin and IGF-1 is mediated by the type 1 IGF receptor.
Supported by grants CA37887 and DK32889 from the National Institutes of Health, Bethesda, MD, and by a Medical University
of South Carolina institutional grant. 相似文献
14.
Rita Pellegrini Filippo Centis Stefania Martignone Antonio Mastroianni Elda Tagliabue Emanuela Tosi Sylvie Ménard Maria I. Colnaghi 《Cancer immunology, immunotherapy : CII》1991,34(1):37-42
Summary In this work a new monoclonal antibody (mAb), designated MGR1, which recognizes the epidermal growth factor receptor (EGF-R) binding site, is described. The main characteristic of this mAb is its ability to discriminate between cells that express normal levels of EGF-R from cells with overexpression, the detectability threshold by immunocytochemical tests being 5 × 104 receptors/cell of 10 µm diameter. MGR1 was found to inhibit EGF binding on the relevant target cells, and vice versa its binding was inhibited by EGF, which indicated that MGR1 recognizes the EGF receptor binding site. MGR1 exerted an inhibitory effect on both the in vitro and in vivo growth of cells with EGF-R overexpression, but had no effect on cells with a normal expression of the receptor. Tumour growth inhibition in athymic mice was also obtained on already implanted tumours. MGR1 therefore seems to be an adequate reagent for the development of immunotherapeutical approaches suitable for the treatment of tumours with EGF-R overexpression. 相似文献
15.
Yu-Chih Liang Shoei-Yn Lin-shiau Chieh-Fu Chen Jen-Kun Lin 《Journal of cellular biochemistry》1997,67(1):55-65
Tea polyphenols are known to inhibit a wide variety of enzymatic activities associated with cell proliferation and tumor progression. The molecular mechanisms of antiproliferation are remained to be elucidated. In this study, we investigated the effects of the major tea polyphenol (−)-epigallocatechin gallate (EGCG) on the proliferation of human epidermoid carcinoma cell line, A431. Using a [3H]thymidine incorporation assay, EGCG could significantly inhibit the DNA synthesis of A431 cells. In vitro assay, EGCG strongly inhibited the protein tyrosine kinase (PTK) activities of EGF-R, PDGF-R, and FGF-R, and exhibited an IC50 value of 0.5–1 μg/ml. But EGCG scarcely inhibited the protein kinase activities of pp60v-src, PKC, and PKA (IC50 > 10 μg/ml). In an in vivo assay, EGCG could reduce the autophosphorylation level of EGF-R by EGF. Phosphoamino acid analysis of the EGF-R revealed that EGCG inhibited the EGF-stimulated increase in phosphotyrosine level in A431 cells. In addition, we showed that EGCG blocked EGF binding to its receptor. The results of further studies suggested that the inhibition of proliferation and suppression of the EGF signaling by EGCG might mainly mediate dose-dependent blocking of ligand binding to its receptor, and subsequently through inhibition of EGF-R kinase activity. J. Cell. Biochem. 67:55–65, 1997. © 1997 Wiley-Liss, Inc. 相似文献
16.
The influence of epidermal growth factor (EGF) on the Ca2+ requirement of normal (NP-2s) and neoplastic human epithelial (PC-3) cells was studied using a clonal growth assay. The interaction of Ca2+ and EGF was investigated by kinetic analysis of dose-response experiments in which the Ca2+ or EGF concentration necessary for half-maximal growth, Km were determined. The normal epithelial cells required 80 times more calcium than did the cancer cells. In the presence of EGF, the Ca2+ requirement of both cell types was virtually identical. EGF did not affect the growth rate of the cancer line. The interaction between Ca2+and EGF was found to be unidirectional since EGF reduced the KmCa2+ 120-fold, whereas Ca2+ had no effect on the EGF dose-response. 相似文献
17.
The concanavalin A receptor from human erythrocyte membranes has been isolated by affinity chromatography using the mild, readily-dialyzable detergent dodecyltrimethylammonium bromide. The purified protein has been reincorporated into large unilamellar phospholipid vesicles using a detergent dialysis technique. The mean diameter of these vesicles increases as the lipid: protein ratio decreases. Binding of succinyl-concanavalin A to these vesicles was quantitated using 125I-labelled lectin in a filtration assay. The concanavalin A receptor in lipid bilayer vesicles provides specific high affinity binding sites for succinyl-concanavalin A with an association constant of 2.13·106 M?1. Scatchard plots indicate positive cooperativity of binding at very low lectin concentrations, a characteristic also seen in concanavalin A binding to intact human erythrocytes. The presence of bovine serum albumin has little effect on lectin binding and is not required for expression of cooperativity. Concanavalin A effectively competes with succinyl-concanavalin A for binding to the vesicles with an association constant of 4.83·106 M?1. Receptor-bearing vesicles are readily agglutinated by concanavalin A but not by its succinylated derivative. The kinetics of vesicle agglutination are biphasic, with an initial rapid phase followed by a pseudo-first order process. We suggest that studies on reassembled receptor proteins in lipid bilayers can provide valuable insight into receptor involvement in transmembrane signalling events and the factors involved in cell membrane behaviour and cell agglutination. 相似文献
18.
We have investigated the stimulation of fluid phase endocytosis by epidermal growth factor (EGF) in normal human fibroblasts using 125I-labeled polyvinylpyrrolidone (125I-PVP) as a fluid phase marker. We found that EGF initially induced a thereefold increase in the rate of 125I-PVP uptake. This initial burst of fluid uptake terminated within 10 min. Thereafter, the rate of fluie uptake in EGF-treated cells was approximately 40% higher than in control cells. To identify the cellular site of EGF action in stimulating fluid phase endocytosis, we examined the kinetics of the induction of this response as well as the kinetics of cell surface binding and internalization of 125I-EGF. Although there was no detectable lag between binding of EGF to the cell surface and its internalization, the kinetics of the two processes were quite different. Significantly, the kinetics of induction of 125I-PVP uptake matched the kinetics of binding of 125I-EGF to its cell surface receptors, indicating that the signal for the increase in fluid phase endocytosis is generated at the cell surface. To determine if EGF-stimulated fluid phase endocytosis was related to EGF-stimulated endocytosis of its own receptor, we compared the EGF dose dependency and time course of the two processes. Although the stimulated endocytosis of the EGF receptor was not saturable with respect to the concentration of EGF used, the stimulation of fluid phase endocytosis was half maximal at an EGF concentration of 1 ng/ml and saturated at a concentration of 5 ng/ml. Also, the stimulation of fluid phase endocytosis was sevenfold greater initially after adding EGF than after a 30-min continuous incubation with the hormone, whereas the enhanced clearance of the EGF receptor did not change during this time period. We conclude that the EGF-stimulated increase in fluid phase endocytosis is not directly coupled to EGF-stimulated endocytosis of its own receptor but instead to a separate signal generated at the cell surface. 相似文献
19.
Laurie Kinder Sorge Russell Hilf 《Biochimica et Biophysica Acta (BBA)/General Subjects》1981,676(2):187-198
To investigate the effects of concanavalin A on insulin binding to R323AC mammary carcinomas, initial experiments were performed to characterize binding of concanavalin A. Concanavalin A binding was found to be specific and saturable. Equilibrium binding experiments demonstrated that addition of low concentration of concanavalin A enhanced the binding of [3H]concanavalin A, suggestive of positively cooperative interactions. Binding of concanavalin A was responsive to hormonal alterations; tumor cells from diabetic rats showed enhanced binding of concanavalin A and insulin compared to cells from intact rats and administration of insulin to diabetic rats returned concanavalin A and insulin binding to levels seen in controls. Incubation of tumor cells with concanavalin A prior to addition of 125I-labelled insulin resulted in a reduction of insulin-binding capacity; succinyl-concanavalin A did not affect binding of insulin. The percent inhibition of insulin binding by concanavalin A was highest at the lower insulin concentrations, providing a linearized Scatchard plot that yielded a calculated Kd value comparable to the low-affinity portion of the curvilinear Scatchard plot for insulin binding. The dissociation rate of bound insulin depended on receptor occupancy. Addition of concanavalin A after insulin binding reached equilibrium resulted in increased insulin binding hormone concentrations, decreased rates of dissociation of insulin and a loss of the correlation between receptor occupancy and dissociation rates. Concanavalin A alone demonstrated an insulin-like effect on glucose transport, which in these tumor cells represents a decrease in transport of 3-O-methylglucose. These suggest that binding of both concanavalin A and insulin to cells from this hormonally responsive neoplasm is under insulin regulation and demonstrates similar characteristics to those reported for a variety of normal cells. Furthermore, the interaction between concanavalin A and the cell membranes affects the affinity of the insulin receptor for insulin and appears to decrease the observed negative cooperativity. 相似文献
20.
《Biochimica et Biophysica Acta (BBA)/Molecular Cell Research》1997,1355(2):114-120
Right side-out plasma membrane vesicles isolated from HeLa cells exhibited an NADH oxidase activity at their external surfaces that was inhibited by the antitumor sulfonylurea, N-(4-methylphenylsulfonyl)-N′-(4-chlorophenyl)urea (LY181984). Intact HeLa cells (fresh or frozen) also exhibited an NADH oxidase activity at the external cell surface. The inhibition of this activity by LY181984 was enhanced by the addition of epidermal growth factor (EGF). The order of addition was critical. It was necessary that the LY181984 be followed by the EGF. If the EGF was administered first, the response to LY181984 was unaffected by EGF. Binding of [3H]LY181984 to HeLa cells also was enhanced by EGF. Growth experiments with HeLa cells revealed a similar pattern of response to EGF. The EC50 of growth inhibition of LY181984 was about 100 μM. However, if the LY181984 was followed by addition of 10 nM EGF, the EC50 for LY181984 was reduced to about 30 nM which now approximated the previously determined Kd of [3H]LY181984 binding of 30 nM and the EC50 of 30 nM for inhibition of NADH oxidase activity by LY181984 by isolated vesicles of plasma membranes. The tumor-inactive sulfonylurea N-(methylphenylsulfonyl-N′-(phenyl)urea (LY181985) was ineffective in the inhibition of NADH oxidation and of growth with HeLa cells either in the presence or absence of EGF. 相似文献