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Results for “Integrin alphaVbeta3”

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At least 415 records · Page 23Linked to original sources

PubMed2006

LRP and alphavbeta3 mediate tPA activation of smooth muscle cells.

Tissue-type plasminogen activator (tPA) regulates vascular contractility through the low-density lipoprotein-related receptor (LRP), and this effect is inhibited by plasminogen activator inhibitor type 1 (PAI-1). We now report that tPA-mediated vasocontraction also requires the integrin alphavbeta3. tPA-induced contraction of rat aortic rings is inhibited by the Arg-Gly-Asp (RGD) peptide and by monoclonal anti-alphavbeta3 antibody. tPA induces the formation of a complex between LRP and alphavbeta3 in vascular smooth muscle cells. The three proteins are internalized within 10 min, causing the cells to become refractory to the readdition of tPA. LRP and alphavbeta3 return to the cell surface by 90 min, restoring cell responsiveness to tPA. PAI-1 and the PAI-1-derived hexapeptide EEIIMD abolish the vasocontractile activity of tPA and inhibit the tPA-mediated interaction between LRP and alphavbeta3. tPA induces calcium mobilization from intracellular stores in vascular smooth muscle cells, and this effect is inhibited by PAI-1, RGD, and antibodies to both LRP and alphavbeta3. These data indicate that tPA-mediated vasocontraction involves the coordinated interaction of LRP with alphavbeta3. Delineating the mechanism underlying these interactions and the nature of the signals transduced may provide new tools to regulate vascular tone and other consequences of tPA-mediated signaling.

Animals↗

PubMed2005

Non peptidic alphavbeta3 antagonists: recent developments.

The alphavbeta3 receptor, which are members of the group of the cellular adhesion molecules (CAM), are heterodimeric transmembrane glycoprotein receptors involved in processes such as cell-cell and cell-matrix adhesion, cell migration and signaling. Integrin alphavbeta3 receptor is expressed on almost all cells originating from the mesenchyme and seem to mediate several biological processes, including adhesion of osteoblasts to the bone matrix, migration of vascular smooth muscle cells, and angiogenesis. Many efforts were done in the last 10 years to individuate inhibitors for alphavbeta3 receptors, due to their involvement in important pathophysiological functions. In fact, selective alphavbeta3 antagonists offer new therapeutic opportunities for the treatment of several human pathologies like osteoporosis, restenosis and diseases involving neovascularization such as rheumatoid arthritis, tumor induced angiogenesis and metastasis. Purpose of this account is to summarize the recent developments in the field of non-peptidic alphavbetav antagonists.

Drug Design↗

PubMed2006

The involvement of osteopontin and its receptors in multiple myeloma cell survival, migration and invasion in the murine 5T33MM model.

Multiple myeloma (MM) is a malignancy characterised by the accumulation of monoclonal plasma cells in the bone marrow. Different reports indicate the expression of CD44 variant isoforms (CD44v) by MM cells. Osteopontin (OPN), which is expressed by MM cells, is known to be a ligand for CD44v6. In this study, we investigated the role of OPN with emphasis on a functional correlation between OPN and CD44v in the 5T33MM model. Our group reported the expression of CD44v by 5T33MM cells. Using this model, we have demonstrated the secretion of OPN by 5T33MM cells. OPN affected 5T33MM cell survival by increasing proliferation and inhibiting apoptosis. OPN also stimulated 5T33MM cell migration, transendothelial migration and matrix metalloproteinase-9 activity. We confirmed the proliferative and migratory effects of OPN on human MM cells. By applying inhibiting anti-CD44v6 antibodies, we found that OPN stimulated cell proliferation by engaging this isoform. Anti-CD44v antibodies and RGD peptides both inhibited cell migration, suggesting an involvement of both, CD44v isoforms and integrins. In conclusion, OPN may act as a mediator of MM cell survival by engaging CD44v. The protein is further involved in migration and invasion of MM cells through the activation of either alphavbeta3 integrin or CD44v isoforms.

Animals↗

PubMed2005

Anti-migratory and anti-angiogenic effect of p16: a novel localization at membrane ruffles and lamellipodia in endothelial cells.

Recent evidence has established different functions for the tumor suppressor protein, p16(INK4A) aside from controlling the cell cycle. Here we report that cdk4/6 inhibition blocked both human umbilical vein endothelial cells (HUVEC) spreading on a vitronectin matrix and HUVEC migration on vitronectin. p16 can also act as an anti-angiogenic molecule in vitro since HUVEC and HMEC cells transfected with Ad-p16 or treated with Antennapedia p16 peptides are unable to differentiate on a Matrigel matrix. Both, p16, cyclin D1, cdk4 and cdk6 were immuno-colocalized with Ezrin, Rac, Vinculin, alphav-integrin, and FAK proteins in the ruffles and lamellipodia of migratory cells. Our results indicate that p16 is a key component of a new cytoplasmic pathway controlling angiogenesis of endothelial cells via the alphavbeta3-integrin-mediated migration.

Cell Membrane↗

PubMed2006

Evidence of angiogenesis in bronchial biopsies of smokers with and without airway obstruction.

The involvement of bronchial vasculature in the airway remodelling occurring in symptomatic smokers with normal lung function and with chronic obstructive pulmonary disease (COPD) has been poorly investigated. An immunohistochemical study was performed on bronchial biopsies taken from 8 non-smokers and 18 smokers divided, according to global health initiative on obstructive lung diseases (GOLD) classification of COPD, into two groups, GOLD 0 and GOLD 2, each of 9 subjects. The number of vessels and the percentage of vascular area in the lamina propria were evaluated by mAb anti-collagen IV. Cellular expression of VEGF and vascular expression of alphavbeta3 integrin were evaluated by the specific monoclonal antibodies. An image processing and analysis system was used to quantify the immunohistochemical data. The number of vessels, the vascular area, the cellular expression of VEGF, the number and percentage of alphavbeta3 positive vessels were significantly higher in GOLD 0 and in GOLD 2 smokers than in non-smokers. The comparison between GOLD 0 and GOLD 2 smokers did show a weak but significantly lower number of vessels in GOLD 2, while the vascular area and the percentage of alphavbeta3 positive vessels did not differ between the two groups. A higher cellular VEGF expression was detected in the GOLD 2 than in the GOLD 0 group. Angiogenesis of bronchial vessels is a component of the airway remodelling occurring in symptomatic smokers with normal lung function and with COPD, it seems independent by the development of airway obstruction and not related to its severity.

Biopsy↗

PubMed1999

Surface densities of ephrin-B1 determine EphB1-coupled activation of cell attachment through alphavbeta3 and alpha5beta1 integrins.

Receptors of the Eph family and their ligands (ephrins) mediate developmental vascular assembly and direct axonal guidance. Migrating cell processes identify appropriate targets within migratory fields based on topographically displayed ephrin gradients. Here, EphB1 regulated cell attachment by discriminating the density at which ephrin-B1 was displayed on a reconstituted surface. EphB1-ephrin-B1 engagement did not promote cell attachment through mechanical tethering, but did activate integrin-mediated attachment. In endothelial cells, attachment to RGD peptides or fibrinogen was mediated through alphavbeta3 integrin. EphB1 transfection conferred ephrin-B1-responsive activation of alpha5beta1 integrin-mediated cell attachment in human embryonic kidney cells. Activation-competent but signaling-defective EphB1 point mutants failed to stimulate ephrin-B1 dependent attachment. These findings lead us to propose that EphB1 functions as a 'ligand density sensor' to signal integrin-mediated cell-matrix attachment.

Cell Adhesion↗

PubMed2004

beta1-Integrins mediate enhancement of airway smooth muscle proliferation by collagen and fibronectin.

Airway smooth muscle (ASM) accumulation and enrichment of the extracellular matrix (ECM) with type I collagen and fibronectin are major pathologic features of airway remodeling in asthma. These ECM components confer enhanced ASM proliferation in vitro, but a requirement for specific integrin ECM receptors has not been examined. Here, we examined the mitogen platelet-derived growth factor (PDGF)-BB on beta1-integrin expression on human ASM cells cultured on these ECM substrates and defined the involvement of specific integrins in cell attachment and proliferation using integrin-neutralizing antibodies. PDGF-BB-dependent proliferation was enhanced two- to threefold by monomeric type I collagen or fibronectin and to a lesser extent by vitronectin; other interstitial ECM components (fibrillar type I and III collagen and tenascin-C) had no effect. Except for increased alpha3 expression induced by PDGF-BB and monomeric type I collagen or fibronectin, alpha1, alpha2, alpha4, alpha5, alphav, and alphavbeta3 integrins were unchanged compared with unstimulated cells on plastic. Blocking antibodies revealed alpha2beta1- and alphavbeta3-mediated attachment to monomeric type I collagen, whereas attachment to fibronectin required alpha5beta1. In contrast, enhancement of PDGF-BB-dependent proliferation by either monomeric type I collagen or fibronectin required alpha2beta1, alpha4beta1, and alpha5beta1 integrins. These data suggest multiple beta1-integrins regulate enhanced ASM proliferative responses.

Adult↗

PubMed2006

Inhibition of angiogenesis by interleukin-4 gene therapy in rat adjuvant-induced arthritis.

OBJECTIVE: Interleukin-4 (IL-4) can modulate neovascularization. In this study, we used a gene therapy approach to investigate the role of IL-4 in angiogenesis in rat adjuvant-induced arthritis (AIA), a model for rheumatoid arthritis. METHODS: Rats received an adenovirus producing IL-4 (AxCAIL-4), a control virus without insert, or control vehicle (phosphate buffered saline) intraarticularly before arthritis onset. At peak onset of arthritis, rats were killed. Vascularization was determined in the synovial tissue, and correlations with inflammation were assessed. Ankle homogenates were used in angiogenesis assays in vitro and in vivo, and protein levels of cytokines and growth factors were assessed by enzyme-linked immunosorbent assay. Synovial tissue expression of alphav integrins was determined by immunohistochemistry. RESULTS: IL-4 induced a reduction in synovial tissue vessel density, which was paralleled by a decrease in inflammation. AxCAIL-4 joint homogenates significantly (P < 0.05) inhibited both endothelial cell (EC) migration and tube formation in vitro. Similarly, AxCAIL-4 inhibited capillary sprouting in the rat aortic ring assay, and vessel growth in the in vivo Matrigel plug assay. The angiostatic effect occurred despite high levels of vascular endothelial growth factor (VEGF), and was associated with down-regulation of the proangiogenic cytokines IL-18, CXCL16, and CXCL5 and up-regulation of the angiogenesis inhibitor endostatin. Of interest, AxCAIL-4 also resulted in decreased EC expression of the alphav and beta3 integrin chains. CONCLUSION: In rat AIA, IL-4 reduces synovial tissue vascularization via angiostatic effects, mediates inhibition of angiogenesis via an association with altered pro- and antiangiogenic cytokines, and may inhibit VEGF-mediated angiogenesis and exert its angiostatic role in part via alphavbeta3 integrin. This knowledge of the specific angiostatic effects of IL-4 may help optimize target-oriented treatment of inflammatory arthritis.

Adjuvants, Immunologic↗

PubMed1998

Granulocyte macrophage-colony stimulating factor reciprocally regulates alphav-associated integrins on murine osteoclast precursors.

The integrins alphavbeta3 and alphavbeta3 are expressed reciprocally during murine osteoclastogenesis in vitro. Specifically, immature osteoclast precursors, in the form of bone marrow macrophages, contain exclusively alphavbeta5, surface expression of which declines with commitment to the osteoclast phenotype, while levels of alphavbeta3 increase concomitantly. The distinct functional significance of alphavbeta5 is underscored by the integrin's capacity, unlike alphavbeta3, to mediate both attachment and spreading on ligand, of marrow macrophages, suggesting alphavbeta3 negotiates initial recognition, by osteoclast precursors, of bone matrix. Northern analysis demonstrates changes in the two beta-subunits, and not alphav, are responsible for these alterations. Treatment of early precursors with granulocyte-macrophage colony stimulating factor (GM-CSF) leads to alterations in beta3 and beta5 mRNA and alphavbeta5 and alphavbeta3, paralleling those occurring during osteoclastogenesis. Nuclear run-on and message stability studies demonstrate that while GM-CSF treatment of precursors alters beta5 transcriptionally, the changes in beta3 arise from prolonged mRNA t1/2. Similar to GM-CSF treatment, the rate of beta5 transcription falls during authentic osteoclastogenesis. In contrast to cytokine-induced alphavbeta3, however, that attending osteoclastogenesis reflects accelerated transcription of the beta3-subunit. Thus, while GM-CSF may participate in modulation of alphavbeta5 during osteoclast differentiation, signals other than those derived from the cytokine must regulate expression of alphavbeta3.

Animals↗

PubMed2004

Design, synthesis, and biochemical evaluation of novel alpha V beta 3 integrin ligands.

Studies on integrin alphaVbeta3 have implicated this receptor in a number of pathologies. In this article we describe some of our initial efforts to design small molecules alphaVbeta3 ligands incorporating an indole core template and an oxyguanidine as basic ending. Synthesis, biochemical activity and pharmacological properties are analyzed.

Drug Design↗

PubMed2002

TGFbeta1 -mediated epithelial to mesenchymal transition is accompanied by invasion in the SiHa cell line.

It has recently been suggested by several investigators that the epithelial-mesenchymal transition-inducing capacity of TGFbetas contributes to invasive transition of tumors at later stages of carcinogenesis. In the present study, we examined the possibility of TGFbeta1-stimulated epithelial-mesenchymal transition in SiHa cell line, detailed molecular events in the process, and its possible contribution to the invasive transition of tumors. TGFbeta1-induced epithelial-mesenchymal transition of SiHa cells was based on morphological and biochemical criteria; actin stress fiber formation, focal translocalization of integrin alphav, talin, and vinculin, fibronectin-based matrix assembly at the cell periphery, and translocalization and down-regulation of E-cadherin. TGFbeta1 also stimulated surface expression of integrin alphavbeta3 and FAK activation. Focal translocalization of integrin alphav preceded actin reorganization and fibronectin matrix assembly, and functional blocking of the integrin suppressed actin stress fiber formation. Furthermore, induction of actin reorganization and fibronectin matrix assembly by TGFbeta1 were shown to be mutually independent events. These changes were irreversible because 5 minutes pulse exposure to TGFbeta1 was sufficient to stimulate progress of actin reorganization and fibronectin matrix assembly. In further studies with raft culture, TGFbeta1 was found to stimulate invasion of SiHa cells into a type I collagen gel matrix. In conclusion, TGFbeta1 stimulated epithelial-mesenchymal transition of SiHa cells, indicating a positive role in the invasive transition of tumors.

Actins↗

PubMed2003

Physiological levels of tumstatin, a fragment of collagen IV alpha3 chain, are generated by MMP-9 proteolysis and suppress angiogenesis via alphaV beta3 integrin.

We demonstrate a physiological role for tumstatin, a cleavage fragment of the alpha3 chain of type IV collagen (Col IValpha3), which is present in the circulation. Mice with a genetic deletion of Col IValpha3 show accelerated tumor growth associated with enhanced pathological angiogenesis, while angiogenesis associated with development and tissue repair are unaffected. Supplementing Col IValpha3-deficient mice with recombinant tumstatin to a normal physiological concentration abolishes the increased rate of tumor growth. The suppressive effects of tumstatin require alphaVbeta3 integrin expressed on pathological, but not on physiological, angiogenic blood vessels. Mice deficient in matrix metalloproteinase-9, which cleaves tumstatin efficiently from Col IValpha3, have decreased circulating tumstatin and accelerated growth of tumor. These results indicate that MMP-generated fragments of basement membrane collagen can have endogenous function as integrin-mediated suppressors of pathologic angiogenesis and tumor growth.

Animals↗

PubMed2003

Cytochalasin D disruption of actin filaments in 3T3 cells produces an anti-apoptotic response by activating gelatinase A extracellularly and initiating intracellular survival signals.

Disruption of actin filaments affects multiple cell functions including motility, signal transduction and cell division, ultimately culminating in cell death. Although this is the usual sequence of events, we have made the interesting observation that disruption of actin filaments by the potent toxin cytochalasin D (Cyto D) causes one cell type, mouse mesangial cells (MMC), to undergo apoptosis, while in another cell type (NIH 3T3), it has the opposite effect, resulting in production of survival signals. The purpose of this study was to investigate the molecular basis for these observed differences. In the present communication, we demonstrate that exposure to Cyto D induces the pro-apoptotic pathways, p38 and stress-activated protein kinase (SAPK)/jun amino-terminal kinase (JNK), in both cell types. However, in 3T3, but not MMC, the extracellular signal regulated kinase (ERK) 1/2 pathway is protected from inhibition following treatment with Cyto D-leading to phosphorylation of Bclxi/Bcl 2-associated death promoter (BAD). Inhibition of Cyto D-induced secretion and activation of gelatinase A in 3T3 cells reverses the production of survival signals by Cyto-D. To investigate this effect further we employed CS-1 cells, a well-characterized melanoma cell line that lacks integrin beta3, and also does not secrete gelatinase A. Co-transfection of CS-1 cells with integrin beta3 and a gelatinase A transgene, which enables the cells to secrete constituitively active gelatinase A, enhances CS-1 cell survival signals. Together, our findings suggest that extracellularly activated gelatinase A, through interaction with integrin alphaVbeta3, elicits survival signals mediated through ERK 1/2 that override activation of p38 and SAPK/JNK stress pathways.

3T3 Cells↗

PubMed2004

Novel RGD-like molecules based on the tyrosine template: design, synthesis, and biological evaluation on isolated integrins alphaVbeta3/alphaIIbbeta3 and in cellular adhesion tests.

RGD (Arg-Gly-Asp) peptidomimetics have been designed for covalent anchorage on biomaterials. The tyrosine template was thus equipped with (i) a basic side chain of various flexibility, (ii) an acidic side chain, which incorporated the XPS fluorine tag, and (iii) a spacer-arm terminated by a primary amine for surface grafting. The most active compounds showed IC50 values in the nanomolar range versus isolated human integrins alphaVbeta3 and alphaIIbbeta3. Preincubation of CaCo2 cells with soluble peptidomimetics (2 and 19a) prevented cellular adhesion on culture plates coated with vitronectin. On the other hand, peptidomimetics (19a and 19b) immobilized on a poly(ethylene)terephthalate membrane (PET) promoted CaCo2 cells adhesion. A modeling study at the ab initio level in MINI-1' basis allowed to compare the various synthetic ligands of integrins and to propose novel pharmacophore structures.

Biomimetic Materials↗

PubMed2005

NO-dependent osteoclast motility: reliance on cGMP-dependent protein kinase I and VASP.

The osteoclast degrades bone in cycles; between cycles, the cell is motile. Resorption occurs by acid transport into an extracellular compartment defined by an alphavbeta3 integrin ring. NO has been implicated in the regulation of bone turnover due to stretch or via estrogen signals, but a specific mechanism linking NO to osteoclastic activity has not been described. NO stimulates osteoclast motility, and at high concentrations NO causes detachment and terminates resorption. Here we demonstrate that NO regulates attachment through the cGMP-dependent protein kinase I (PKG I) via phosphorylation of the intermediate protein VASP. VASP colocalized with the alphavbeta3 ring in stationary cells, but alternating bands of VASP and alphavbeta3 occurred when motility was induced by NO donors or cGMP. Redistribution of VASP correlated with its phosphorylation. Dependency of NO-induced motility on PKG I and on VASP was shown by siRNA knockdown of each protein. VASP knockdown also altered distribution of alphavbeta3 at the attachment site. We conclude that PKG I and VASP are essential for reorganization of attachment and cytoplasmic proteins in motility induced by NO or by cGMP.

Cell Adhesion Molecules↗

PubMed2005

Three-dimensional EM structure of the ectodomain of integrin {alpha}V{beta}3 in a complex with fibronectin.

Integrins are alphabeta heterodimeric cell surface receptors that mediate transmembrane signaling by binding extracellular and cytoplasmic ligands. The ectodomain of integrin alphaVbeta3 crystallizes in a bent, genuflexed conformation considered to be inactive (unable to bind physiological ligands in solution) unless it is fully extended by activating stimuli. We generated a stable, soluble complex of the Mn(2+)-bound alphaVbeta3 ectodomain with a fragment of fibronectin (FN) containing type III domains 7 to 10 and the EDB domain (FN7-EDB-10). Transmission electron microscopy and single particle image analysis were used to determine the three-dimensional structure of this complex. Most alphaVbeta3 particles, whether unliganded or FN-bound, displayed compact, triangular shapes. A difference map comparing ligand-free and FN-bound alphaVbeta3 revealed density that could accommodate the RGD-containing FN10 in proximity to the ligand-binding site of beta3, with FN9 just adjacent to the synergy site binding region of alphaV. We conclude that the ectodomain of alphaVbeta3 manifests a bent conformation that is capable of stably binding a physiological ligand in solution.

Binding Sites↗

PubMed2000

Integrins and signaling in osteoclast function.

Integrins are heterodimeric adhesion receptors that mediate cell-matrix and cell-cell interactions. Osteoclasts highly express the alphavbeta3 integrin, which binds to a variety of extracellular matrix proteins including vitronectin, osteopontin and bone sialoprotein. RGD-containing peptides, RGD-mimetics and alphavbeta3 blocking antibodies inhibit bone resorption in vitro and in vivo, suggesting that this integrin plays an important role in osteoclast function. RGD-containing peptides were shown to raise cytosolic calcium in osteoclasts. Furthermore, several signaling and adaptor molecules were found to be involved in alphavbeta3 integrin-dependent signaling pathways, including phosphatidylinositol 3-kinase, c-Src, PYK2 and p130(cas). In addition, cytoskeletal molecules such as paxillin, vinculin, gelsolin and F-actin are recruited to adhesion contacts upon integrin activation. Many of these molecules signaling and cytoskeletal localize to the sealing zone of actively resorbing osteoclasts, suggesting that they play a role in linking the adhesion of osteoclasts to the bone matrix with the cytoskeletal organization and the polarization and activation of these cells for bone resorption.

Animals↗

PubMed2005

Extracellular matrix regulates endothelial functions through interaction of VEGFR-3 and integrin alpha5beta1.

Endothelium extracellular matrix (ECM) interactions can provide distinct spatial and molecular signals which control cellular proliferation, migration, and differentiation. Here, we investigated the role of fibronectin (FN), a major ECM protein, on the functions of lymphatic endothelial cells (LEC). We observed that FN, the ligand for integrin alpha5beta1, selectively promoted the growth of LEC as compared with vitronectin (VN) in the presence of the ligand for vascular endothelial growth factor receptor 3 [VEGFR-3 (VEGF-C156S)]. Upon investigating the mechanisms whereby ECM components regulate VEGFR-3 signaling, we found that FN transactivated VEGFR-3 and significantly enhanced the phosphorylation of VEGFR-3 induced by VEGF-C156S as compared to VN. An enhanced association of the integrin subunit alpha5 or beta1 with VEGFR-3, after stimulation with VEGF-C156S, was observed by co-immunoprecipitation. While blockade of integrin alpha5beta1 inhibited the VEGF-C156S-induced phosphorylation of VEGFR-3, no similar effect was obtained by blocking integrin alphavbeta3. FN also protected the endothelial cells from serum deprivation-induced apoptosis. Moreover, while the specific PI3 kinase inhibitor, LY294002, abolished this FN-mediated cell survival, the MAPK kinase inhibitor, PD98059, had no significant effect. Furthermore, a dominant-negative mutant of VEGFR-3 (G857R) reduced VEGF-C156S or FN-mediated cell survival, as well as the activities of PI3 kinase/Akt. Our results indicate that integrin alpha5beta1 participates in the activation of both VEGFR-3 and its downstream PI3 kinase/Akt signaling pathway, which is essential for FN-mediated lymphatic endothelial cell survival and proliferation.

Apoptosis↗