共查询到20条相似文献,搜索用时 0 毫秒
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Saverio Francesco Retta Georgia Cassar Monica D'Amato Riccardo Alessandro Maurizio Pellegrino Simona Degani Giacomo De Leo Lorenzo Silengo Guido Tarone 《Molecular biology of the cell》2001,12(10):3126-3138
There is increasing evidence that a fine-tuned integrin cross talk can generate a high degree of specificity in cell adhesion, suggesting that spatially and temporally coordinated expression and activation of integrins are more important for regulated cell adhesive functions than the intrinsic specificity of individual receptors. However, little is known concerning the molecular mechanisms of integrin cross talk. With the use of beta(1)-null GD25 cells ectopically expressing the beta(1)A integrin subunit, we provide evidence for the existence of a cross talk between beta(1) and alpha(V) integrins that affects the ratio of alpha(V)beta(3) and alpha(V)beta(5) integrin cell surface levels. In particular, we demonstrate that a down-regulation of alpha(V)beta(3) and an up-regulation of alpha(V)beta(5) occur as a consequence of beta(1)A expression. Moreover, with the use of GD25 cells expressing the integrin isoforms beta(1)B and beta(1)D, as well as two beta(1) cytoplasmic domain deletion mutants lacking either the entire cytoplasmic domain (beta(1)TR) or only its "variable" region (beta(1)COM), we show that the effects of beta(1) over alpha(V) integrins take place irrespective of the type of beta(1) isoform, but require the presence of the "common" region of the beta(1) cytoplasmic domain. In an attempt to establish the regulatory mechanism(s) whereby beta(1) integrins exert their trans-acting functions, we have found that the down-regulation of alpha(V)beta(3) is due to a decreased beta(3) subunit mRNA stability, whereas the up-regulation of alpha(V)beta(5) is mainly due to translational or posttranslational events. These findings provide the first evidence for an integrin cross talk based on the regulation of mRNA stability. 相似文献
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Ayako Miki Satomi Inaba Takahiro Maruno Yuji Kobayashi 《Bioscience, biotechnology, and biochemistry》2017,81(5):951-957
Endo-1,3-β-glucanase from Cellulosimicrobium cellulans DK-1 has a carbohydrate-binding module (CBM-DK) at the C-terminal side of a catalytic domain. Out of the imperfect tandem α-, β-, and γ-repeats in CBM-DK, the α-repeat primarily contributes to β-glucan binding. This unique feature is derived from Trp273 in α-repeat, whose corresponding residues in β- and γ-repeats are Asp314 and Gly358, respectively. In this study, we generated Trp-switched mutants, W273A/D314W, D270A/W273A/D314W, W273A/G358W, and D270A/W273A/G358W, and analyzed their binding abilities toward laminarioligosaccharides and laminarin. While the binding affinities of D270A/W273A and W273A mutants were either lost or much lower than that of the wild-type, those of Trp-switched mutants recovered, indicating that a Trp introduction in β- or γ-repeat can substitute the α-repeat by primarily contributing to β-glucan binding. Thus, we have successfully engineered a CBM-DK that binds to laminarin by a mechanism different from that of the wild-type, but with similar affinity. 相似文献
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Takao Sakai Qinghong Zhang Reinhard Fssler Deane F. Mosher 《The Journal of cell biology》1998,141(2):527-538
β1A integrin subunits with point mutations of the cytoplasmic domain were expressed in fibroblasts derived from β1-null stem cells. β1A in which one or both of the tyrosines of the two NPXY motifs (Y783, Y795) were changed to phenylalanines formed active α5β1 and α6β1 integrins that mediated cell adhesion and supported assembly of fibronectin. Mutation of the proline in either motif (P781, P793) to an alanine or of a threonine in the inter-motif sequence (T788) to a proline resulted in poorly expressed, inactive β1A. Y783,795F cells developed numerous fine focal contacts and exhibited motility on a surface. When compared with cells expressing wild-type β1A or β1A with the D759A activating mutation of a conserved membrane–proximal aspartate, Y783,795F cells had impaired ability to transverse filters in chemotaxis assays. Analysis of cells expressing β1A with single Tyr to Phe substitutions indicated that both Y783 and Y795 are important for directed migration. Actin-containing microfilaments of Y783,795F cells were shorter and more peripheral than microfilaments of cells expressing wild-type β1A. These results indicate that change of the phenol side chains in the NPXY motifs to phenyl groups (which cannot be phosphorylated) has major effects on the organization of focal contacts and cytoskeleton and on directed cell motility. 相似文献
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Candida wickerhamii NRRL Y-2563 expressed β-glucosidase activity (3 to 8 U/ml) constitutively when grown aerobically in complex medium containing either glycerol, succinate, xylose, galactose, or cellobiose as the carbon source. The addition of a high concentration of glucose (>75 g/liter) repressed β-glucosidase expression (<0.3 U/ml); however, this yeast did produce β-glucosidase when the initial glucose concentration was ≤50 g/liter. When grown aerobically in medium containing glucose plus the above-listed carbon sources, diauxic utilization of the carbon source was observed and the expression of β-glucosidase was glucose repressed. Surprisingly, glucose repression did not occur when the cells were grown anaerobically. When grown anaerobically in medium containing 100 g of glucose per liter, C. wickerhamii produced 6 to 9 U of enzyme per ml and did not demonstrate diauxic utilization of glucose-cellobiose mixtures. To our knowledge, this is the first report of apparent derepression of a glucose-repressed enzyme by anaerobiosis. 相似文献
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Feiya Li Sambra D. Redick Harold P. Erickson Vincent T. Moy 《Biophysical journal》2003,84(2):1252-1262
The interaction of the α5β1 integrin and its ligand, fibronectin (FN), plays a crucial role in the adhesion of cells to the extracellular matrix. An important intrinsic property of the α5β1/FN interaction is the dynamic response of the complex to a pulling force. We have carried out atomic force microscopy measurements of the interaction between α5β1 and a fibronectin fragment derived from the seventh through tenth type III repeats of FN (i.e., FN7-10) containing both the arg-gly-asp (RGD) sequence and the synergy site. Direct force measurements obtained from an experimental system consisting of an α5β1 expressing K562 cell attached to the atomic force microscopy cantilever and FN7-10 adsorbed on a substrate were used to determine the dynamic response of the α5β1/FN7-10 complex to a pulling force. The experiments were carried out over a three-orders-of-magnitude change in loading rate and under conditions that allowed for detection of individual α5β1/FN7-10 interactions. The dynamic rupture force of the α5β1/FN7-10 complex revealed two regimes of loading: a fast loading regime (>10,000 pN/s) and a slow loading regime (<10,000 pN/s) that characterize the inner and outer activation barriers of the complex, respectively. Activation by TS2/16 antibody increased both the frequency of adhesion and elevated the rupture force of the α5β1/wild type FN7-10 complex to higher values in the slow loading regime. In experiments carried out with a FN7-10 RGD deleted mutant, the force measurements revealed that both inner and outer activation barriers were suppressed by the mutation. Mutations to the synergy site of FN, however, suppressed only the outer barrier activation of the complex. For both the RGD and synergy deletions, the frequency of adhesion was less than that of the wild type FN7-10, but was increased by integrin activation. The rupture force of these mutants was only slightly less than that of the wild type, and was not increased by activation. These results suggest that integrin activation involved a cooperative interaction with both the RGD and synergy sites. 相似文献
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John Geigert Saul L. Neidleman Te-Ning E. Liu Susanne K. DeWitt Barbara M. Panschar Demetrios J. Dalietos Eric R. Siegel 《Applied microbiology》1983,45(3):1148-1149
The relative activity of Flavobacterium whole cells on the enzymatic synthesis of epoxides from α,β-chlorohydrins, -bromohydrins, and -iodohydrins is described. 相似文献
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Integrin Cross Talk: Activation of Lymphocyte Function-associated Antigen-1 on Human T Cells Alters α4β1- and α5β1-mediated Function
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A regulated order of adhesion events directs leukocytes from the vascular compartment into injured tissues in response to inflammatory stimuli. We show that on human T cells, the interaction of the β2 integrin leucocyte function–associated antigen-1 (LFA-1) with its ligand intercellular adhesion molecule-1 (ICAM-1) will decrease adhesion mediated by α4β1 and, to a lesser extent, α5β1. Similar inhibition is also seen when T cells are exposed to mAb 24, which stabilizes LFA-1 in an active state after triggering integrin function through divalent cation Mg2+, PdBu, or T cell receptor/ CD3 complex (TCR/CD3) cross-linking. Such cross talk decreases α4β1 integrin–mediated binding of T cells to fibronectin and vascular cell adhesion molecule-1 (VCAM-1). In contrast, ligand occupancy or prolonged activation of β1 integrin has no effect on LFA-1 adhesion to ICAM-1. We also show that T cell migration across fibronectin, unlike adhesion, is mediated solely by α5β1, and is increased when the α4β1-mediated component of fibronectin adhesion is decreased either by cross talk or the use of α4-blocking mAb. The ability of mAb 24 Fab′ fragments to induce cross talk without cross-linking LFA-1 suggests signal transduction through the active integrin. These data provide the first direct evidence for cross talk between LFA-1 and β1 integrins on T cells. Together, these findings imply that activation of LFA-1 on the extravasating T cell will decrease the binding to VCAM-1 while enhancing the subsequent migration on fibronectin. This sequence of events provides a further level of complexity to the coordination of T cell integrins, whose sequential but overlapping roles are essential for transmigration. 相似文献
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Differential induction of innate memory in porcine monocytes by β-glucan or bacillus Calmette-Guerin
Innate immunomodulation via induction of innate memory is one mechanism to alter the host’s innate immune response to reduce or prevent disease. Microbial products modulate innate responses with immediate and lasting effects. Innate memory is characterized by enhanced (training) or depressed (tolerance) innate immune responses, including pro-inflammatory cytokine production, to secondary exposure following a priming event. To investigate the ability of β-glucans and bacillus Calmette-Guerin to induce innate training or tolerance in pig cells, porcine monocytes were cultured with priming agonist (β-glucans or bacillus Calmette-Guerin) then re-stimulated 5 d later with a heterologous microbial agonist to determine induction of innate memory. Priming with β-glucan from Saccharomyces cerevisiae depressed IL-1β and TNF-α cytokine responses to re-stimulation with LPS, indicative of a tolerized state. However, bacillus Calmette-Guerin priming induced a trained state in porcine monocytes, as LPS re-stimulation enhanced IL-1β and TNF-α gene expression and protein production. We present the first evidence of innate memory in pig monocytes, with bacillus Calmette-Guerin (training) or Saccharomyces cerevisiae β-glucan (tolerance). Induction of a trained or tolerized state in vitro is a first step to identify agonists to alter the innate immune system at the animal level with the intent of enhancing disease resistance. 相似文献
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The α5β1 Integrin Mediates Elimination of Amyloid-β Peptide and Protects Against Apoptosis
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Michelle L. Matter Zhuohua Zhang Christer Nordstedt Erkki Ruoslahti 《The Journal of cell biology》1998,141(4):1019-1030
The amyloid-β peptide (Aβ) can mediate cell attachment by binding to β1 integrins through an arg-his-asp sequence. We show here that the α5β1 integrin, a fibronectin receptor, is an efficient binder of Aβ, and mediates cell attachment to nonfibrillar Aβ. Cells engineered to express α5β1 internalized and degraded more added Aβ1-40 than did α5β1-negative control cells. Deposition of an insoluble Aβ1-40 matrix around the α5β1-expressing cells was reduced, and the cells showed less apoptosis than the control cells. Thus, the α5β1 integrin may protect against Aβ deposition and toxicity, which is a course of Alzheimer's disease lesions. 相似文献
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Affinity Modulation of Platelet Integrin αIIbβ3 by β3-Endonexin, a Selective Binding Partner of the β3 Integrin Cytoplasmic Tail
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Hirokazu Kashiwagi Martin A. Schwartz Martin Eigenthaler K.A. Davis Mark H. Ginsberg Sanford J. Shattil 《The Journal of cell biology》1997,137(6):1433-1443
Platelet agonists increase the affinity state of integrin αIIbβ3, a prerequisite for fibrinogen binding and platelet aggregation. This process may be triggered by a regulatory molecule(s) that binds to the integrin cytoplasmic tails, causing a structural change in the receptor. β3-Endonexin is a novel 111–amino acid protein that binds selectively to the β3 tail. Since β3-endonexin is present in platelets, we asked whether it can affect αIIbβ3 function. When β3-endonexin was fused to green fluorescent protein (GFP) and transfected into CHO cells, it was found in both the cytoplasm and the nucleus and could be detected on Western blots of cell lysates. PAC1, a fibrinogen-mimetic mAb, was used to monitor αIIbβ3 affinity state in transfected cells by flow cytometry. Cells transfected with GFP and αIIbβ3 bound little or no PAC1. However, those transfected with GFP/β3-endonexin and αIIbβ3 bound PAC1 specifically in an energy-dependent fashion, and they underwent fibrinogen-dependent aggregation. GFP/β3-endonexin did not affect levels of surface expression of αIIbβ3 nor did it modulate the affinity of an αIIbβ3 mutant that is defective in binding to β3-endonexin. Affinity modulation of αIIbβ3 by GFP/β3-endonexin was inhibited by coexpression of either a monomeric β3 cytoplasmic tail chimera or an activated form of H-Ras. These results demonstrate that β3-endonexin can modulate the affinity state of αIIbβ3 in a manner that is structurally specific and subject to metabolic regulation. By analogy, the adhesive function of platelets may be regulated by such protein–protein interactions at the level of the cytoplasmic tails of αIIbβ3. 相似文献
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Yoshinari Yamazaki Yumiko Hayashi Masatoshi Arita Tadaharu Hieda Yoichi Mikami 《Applied microbiology》1988,54(10):2354-2360
α-Ionone, α-methylionone, and α-isomethylionone were converted by Aspergillus niger JTS 191. The individual bioconversion products from α-ionone were isolated and identified by spectrometry and organic synthesis. The major products were cis-3-hydroxy-α-ionone, trans-3-hydroxy-α-ionone, and 3-oxo-α-ionone. 2,3-Dehydro-α-ionone, 3,4-dehydro-β-ionone, and 1-(6,6-dimethyl-2-methylene-3-cyclohexenyl)-buten-3-one were also identified. Analogous bioconversion products from α-methylionone and α-isomethylionone were also identified. From results of gas-liquid chromatographic analysis during the fermentation, we propose a metabolic pathway for α-ionones and elucidation of stereochemical features of the bioconversion. 相似文献
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The crowdedness of living cells, hundreds of milligrams per milliliter of macromolecules, may affect protein folding, function, and misfolding. Still, such processes are most often studied in dilute solutions in vitro. To assess consequences of the in vivo milieu, we here investigated the effects of macromolecular crowding on the amyloid fiber formation reaction of α-synuclein, the amyloidogenic protein in Parkinson’s disease. For this, we performed spectroscopic experiments probing individual steps of the reaction as a function of the macromolecular crowding agent Ficoll70, which is an inert sucrose-based polymer that provides excluded-volume effects. The experiments were performed at neutral pH at quiescent conditions to avoid artifacts due to shaking and glass beads (typical conditions for α-synuclein), using amyloid fiber seeds to initiate reactions. We find that both primary nucleation and fiber elongation steps during α-synuclein amyloid formation are accelerated by the presence of 140 and 280 mg/mL Ficoll70. Moreover, in the presence of Ficoll70 at neutral pH, secondary nucleation appears favored, resulting in faster overall α-synuclein amyloid formation. In contrast, sucrose, a small-molecule osmolyte and building block of Ficoll70, slowed down α-synuclein amyloid formation. The ability of cell environments to modulate reaction kinetics to a large extent, such as severalfold faster individual steps in α-synuclein amyloid formation, is an important consideration for biochemical reactions in living systems. 相似文献
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Complement fragment iC3b serves as a major opsonin for facilitating phagocytosis via its interaction with complement receptors CR3 and CR4, also known by their leukocyte integrin family names, αMβ2 and αXβ2, respectively. Although there is general agreement that iC3b binds to the αM and αX I-domains of the respective β2-integrins, much less is known regarding the regions of iC3b contributing to the αX I-domain binding. In this study, using recombinant αX I-domain, as well as recombinant fragments of iC3b as candidate binding partners, we have identified two distinct binding moieties of iC3b for the αX I-domain. They are the C3 convertase-generated N-terminal segment of the C3b α’-chain (α’NT) and the factor I cleavage-generated N-terminal segment in the CUBf region of α-chain. Additionally, we have found that the CUBf segment is a novel binding moiety of iC3b for the αM I-domain. The CUBf segment shows about a 2-fold higher binding activity than the α’NT for αX I-domain. We also have shown the involvement of crucial acidic residues on the iC3b side of the interface and basic residues on the I-domain side. 相似文献
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Chondroadherin (the 36-kD protein) is a leucine-rich, cartilage matrix protein known to mediate adhesion of isolated chondrocytes. In the present study we investigated cell surface proteins involved in the interaction of cells with chondroadherin in cell adhesion and by affinity purification. Adhesion of bovine articular chondrocytes to chondroadherin-coated dishes was dependent on Mg2+ or Mn2+ but not Ca2+. Adhesion was partially inhibited by an antibody recognizing β1 integrin subunit. Chondroadherin-binding proteins from chondrocyte lysates were affinity purified on chondroadherin-Sepharose. The β1 integrin antibody immunoprecipitated two proteins with molecular mass ~110 and 140 kD (nonreduced) from the EDTA-eluted material. These results indicate that a β1 integrin on chondrocytes interacts with chondroadherin. To identify the α integrin subunit(s) involved in interaction of cells with the protein, we affinity purified chondroadherin-binding membrane proteins from human fibroblasts. Immunoprecipitation of the EDTA-eluted material from the affinity column identified α2β1 as a chondroadherin-binding integrin. These results are in agreement with cell adhesion experiments where antibodies against the integrin subunit α2 partially inhibited adhesion of human fibroblast and human chondrocytes to chondroadherin. Since α2β1 also is a receptor for collagen type II, we tested the ability of different antibodies against the α2 subunit to inhibit adhesion of T47D cells to collagen type II and chondroadherin. The results suggested that adhesion to collagen type II and chondroadherin involves similar or nearby sites on the α2β1 integrin. Although α2β1 is a receptor for both collagen type II and chondroadherin, only adhesion of cells to collagen type II was found to mediate spreading. 相似文献
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