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At least 469 records · Page 26Linked to original sources
PubMed1999

Expression of cell adhesion molecules in murine placentas and a placental cell line.

Integrins and vascular cell adhesion molecule-1 (VCAM-1) are required for normal placental development. In this study, integrin subunits alpha4, alphav, beta1, and beta3, and VCAM-1 were investigated for expression in uteroplacental units (gestation day [g.d.] 6 and 8) and placentas (g.d. 10, 12, 14, 16, and 18) of Swiss-Webster mice. All subunits and VCAM-1 mRNA (identified by reverse transcriptase polymerase chain reaction [RT-PCR]) and protein (detected by immunofluorescence) were present in all tissues throughout gestation. VCAM-1 was expressed strongly in the ectoplacental cone and trophoblast giant cells, alpha4 was expressed strongly by trophoblast giant cells and moderately by spongiotrophoblast and labyrinthine trophoblast, and alphav was expressed more strongly in the spongiotrophoblast than in the labyrinthine zone. The beta1 was more strongly expressed in the labyrinthine than the spongiotrophoblast zone, while beta3 and VCAM-1 were essentially equal in the two zones. Trophoblast-like SM9-1 cells were positive for all of the adhesion molecules when tested by RT-PCR and immunocytochemistry. Adhesion molecule expression in SM9-1 cells was consistent with expression in the labyrinthine zone. Collectively, the results of this study demonstrate that murine placentas contain mRNA and protein for alpha4, alphav, beta1, beta3, and VCAM-1, and that expression is cell-specific. These results and the identification of an adhesion molecule-expressing trophoblastic cell line should facilitate future studies on the function of adhesion molecules in placental development.

Animals↗
PubMed1999

Ultrastructure and immunohistochemical identification of the extracellular matrix of the chinchilla cochlea.

The molecular composition and three-dimensional organization of the extracellular matrix (ECM) was studied by immunofluorescent microscopy, transmission and scanning electron microscopy in three connective tissue structures of the cochlea: the spiral limbus, basilar membrane and spiral ligament. Type II collagen, fibronectin, tenascin, chondroitin sulfate proteoglycans, alphav and beta1 integrins were immunolocalized in the ECM of these connective tissue structures. Electron micrographs showed a continuum of cross-striated collagen fibrils having a similar diameter and axial periodicity that spread from the spiral limbus via the basilar membrane and into the spiral ligament. Some of collagen fibrils were aggregated laterally into bundles. Bundle images, and their digital Fourier transformations, showed a major 67-nm axial D-repeat characteristic for collagen fibrils. Transmission electron microscopy showed numerous proteoglycans associated with the collagen fibrils. The spiral limbus, basilar membrane and spiral ligament demonstrated regional differences in molecular composition and structural organization of their ECM. The glycoproteins fibronectin, tenascin and alphav integrin were immunolocalized mainly in the basilar membrane. Collagen fibrils of the spiral limbus and spiral ligament did not appear to be strongly oriented. However, most of the collagen fibrils in the basilar membrane were arranged into radially directed bundles. Collagen fibrils in the basilar membrane were also surrounded by a homogeneous matrix, which was immunoreactive to fibronectin and tenascin antibodies. A more complete understanding of the composition and structural organization of the ECM in these connective tissue structures in the cochlea provides a foundation upon which micromechanical models of cochlear function can be constructed.

Animals↗
PubMed2003

Medulloblastoma cell invasion is inhibited by green tea (-)epigallocatechin-3-gallate.

Epigallocatechin-3-gallate (EGCG), the major green tea polyphenol, can reach the brain following oral intake and could thus act as an anti-tumoral agent targeting several key steps of brain cancer cells invasive activity. Because integrin-mediated extracellular matrix recognition is crucial during the cell adhesion processes involved in carcinogenesis, we have investigated the effects of EGCG on different cellular integrins of the pediatric brain tumor-derived medulloblastoma cell line DAOY. Using flow cytometry, we report the levels of expression of several cell surface integrins in DAOY. These include high expression of alpha2, alpha3, and beta1 integrins, as well as alphav and beta3 integrins. Moreover, we provide evidence that EGCG can antagonize DAOY cell migration specifically on collagen by increasing cell adhesive ability through specific gene and protein upregulation of the beta1 integrin subunit. Our results suggest that this naturally occurring green tea polyphenol may thus be used as a nutraceutical therapeutic agent in targeting the invasive character of medulloblastomas.

Apoptosis↗
PubMed2006

Nano-fibrous scaffolding promotes osteoblast differentiation and biomineralization.

Nano-fibrous poly(L-lactic acid) (PLLA) scaffolds with interconnected pores were developed under the hypothesis that nano-fibrous scaffolding would mimic a morphological function of collagen fibrils to create a more favorable microenvironment for cells versus solid-walled scaffolds. In this study, an in vitro system was used to examine biological properties of the nano-fibrous scaffolds compared with those of solid-walled scaffolds for their potential use in bone tissue engineering. Biomineralization was enhanced substantially on the nano-fibrous scaffolds compared to solid-walled scaffolds, and this was confirmed by von Kossa staining, measurement of calcium contents, and transmission electron microscopy. In support of this finding, osteoblasts cultured on the nano-fibrous scaffolds exhibited higher alkaline phosphatase activity and an earlier and enhanced expression of the osteoblast phenotype versus solid-walled scaffolds. Most notable were the increases in runx2 protein and in bone sialoprotein mRNA in cells cultured on nano-fibrous scaffolds versus solid-walled scaffolds. At the day 1 of culture, alpha2 and beta1 integrins as well as alphav and beta3 integrins were highly expressed on the surface of cells seeded on nano-fibrous scaffolds, and linked to this were higher levels of phospho-Paxillin and phospho-FAK in cell lysates. In contrast, cells seeded on solid-walled scaffolds expressed significantly lower levels of these integrins, phospho-Paxillin, and phospho-FAK. To further examine the role of nano-fibrous architecture, we inhibited the formation of collagen fibrils by adding 3,4-dehydroproline to cultures and then assayed cells for expression of alpha2 integrin. Cells seeded on nano-fibrous scaffolds sustained expression of alpha2 integrin in the presence of dehydroproline, while suppression of alpha2 integrin was evident in cells seeded on solid-walled scaffolds. These results provide initial evidence that synthetic nano fibers may exhibit certain properties that are comparable to natural collagen fibers, and thus, the nano-fibrous architecture may serve as a superior scaffolding versus solid-walled architecture for promoting osteoblast differentiation and biomineralization.

Animals↗
PubMed2006

Collagen XVII promotes integrin-mediated squamous cell carcinoma transmigration--a novel role for alphaIIb integrin and tirofiban.

The expression of collagen XVII (BP180), a transmembrane hemidesmosomal component, is upregulated in invasive areas of epithelial tumors. The collagenous ectodomain of collagen XVII is cleaved from the plasma membrane of keratinocytes and malignant epithelial cells. The released ectodomain is predicted to regulate cell detachment, differentiation, and motility. We report that the cell adhesion domain of collagen XVII, Col15, is able to chemotactically attract invasive HSC-3 SCC cells but not keratinocytes. Analysis of integrin expression revealed that HSC-3 cells, unlike keratinocytes, express alphaIIb integrin, a platelet-specific fibrinogen receptor. We show that this novel chemotactic function is mediated by the known Col15-binding integrins alpha5beta1 and alphav and the platelet integrin alphaIIb. Moreover, we report that tirofiban, a FDA-proved alphaIIb integrin-blocking drug widely used for the therapy of acute coronary ischaemic syndrome and the prevention of thrombotic complications, inhibits the Col15 chemotaxis of HSC-3 carcinoma cells. Together, these data demonstrate a novel interaction between collagen XVII and alphaIIb integrin and also suggest a possibility to use tirofiban to inhibit the invasion and progression of alphaIIb expressing SCC tumors.

Adult↗
PubMed2004

Jararhagin, a snake venom metalloproteinase-disintegrin, stimulates epithelial cell migration in an in vitro restitution model.

The snake venom metalloproteinase-disintegrin jararhagin (JG) has no chemotactic activity but stimulates the migration of neutrophils in vivo through a mechanism still unclear. In this study we investigated the effects of jararhagin on epithelial cell adhesion and migration in vitro. F-actin arrangement and the distribution of laminin, fibronectin, several integrins and phosphorylated Focal Adhesion Kinase (FAK) were studied using rhodamine-phalloidin and immunofluorescence. Maximum stimulation of migration (about 100%) was obtained with 5 microg/ml JG, with about 38% inhibition of cellular adhesion. In migratory cells the toxin stimulated the formation of filopodia, lamellipodia and stress fibers. The pericellular fibronectin matrix was lost in migrating cells, while laminin was less affected. The toxin stimulated FAK phosphorylation and the recruitment of alphav-containing integrins to focal contacts, whereas integrins containing the alpha2 subunit were reduced in these junctions. Inactivation of the toxin with 1,10 phenanthroline showed that the catalytic activity is important for the effect of jararhagin on cell migration, FAK phosphorylation and for the recruitment of alphav, but not as much for the anti-adhesive effect. In conclusion, jararhagin stimulates the migration of epithelial cells in vitro through a mechanism that involves its proteolytic activity, qualitative changes in cellular adhesion and the formation of actin-rich cellular processes.

Actins↗
PubMed1999

Keratinocyte growth factor (KGF) promotes keratinocyte cell attachment and migration on collagen and fibronectin.

Keratinocyte growth factor (KGF) induction of keratinocyte attachment and migration on provisional and basement membrane proteins was examined. KGF-treated keratinocytes showed increased attachment to collagen types I and IV and fibronectin, but, not to laminin-1, vitronectin, or tenascin. This increase was time- and dose-dependent. Increase in attachment occurred with 2 10 microg/ml of ECM proteins. This KGF-stimulated cell attachment was beta1 integrin-dependent but was not associated with stimulation of the cell surface expression nor affinity (activity) of the collagen integrin receptor (alpha2beta1) nor the fibronectin integrin receptors (alpha5beta1 or alphav). At the basal layer of KGF-treated cells significant accumulation of beta1 integrins was found at the leading edges, and actin stress fibers colocalized with beta1. KGF also induced migratory phenotype and stimulated keratinocyte migration on both fibronectin and collagen types I and IV but not on laminin-1, vitronectin nor tenascin. The results suggest that in addition to its proliferation promoting activity. KGF is able to modulate keratinocyte adhesion and migration on collagen and fibronectin. Our data suggest that KGF induced integrin avidity (clustering), a signaling event, which is not dependent on the alteration of cell surface integrin numbers.

Antigens, CD↗
PubMed2005

Ligand-mimetic anti-alphaIIb beta3 antibody PAC-1 inhibits tyrosine signaling, proliferation and lung colonization of melanoma cells.

Beta3 integrin expression is the hallmark of melanoma and may serve as a potential therapeutic target. While alphav beta3 integrin expression seems to be constitutive in melanoma, ectopic expression of platelet-alphaIIb beta3 is dependent on progression. B16a murine melanoma is a suitable model for studies on alphaIIb beta3 treatment strategies since alphav beta3 is not expressed in this cell line. Here we have used a ligand-mimetic anti-alphaIIb beta3 monoclonal antibody, PAC-1, to test the biological consequences of alphaIIb beta3 modulation in melanoma cells. We have previously reported that in B16a cells FAK is constitutively active and tyrosine-phosphorylated. Upon PAC-1 binding to the surface alphaIIb beta3, which is in the active conformation, FAK became dephosphorylated through a process of PKC-dependent phosphatase activation. Furthermore, PAC-1 binding to B16a cells induced a significant decrease in phosphotyrosine-positive melanoma cells within 30 min. Treatment of B16a cells in vitro with PAC-1 significantly inhibited proliferation by decreasing the mitotic index but not affecting apoptotic rate. Incubation of B16a cells with PAC-1 decreased their lung colonization potential, suggesting a profound alteration in their biological behavior under the effect of this antibody. These preclinical data suggest that the ectopic expression of alphaIIb beta3 in melanoma cells can be exploited as a novel target of antibody therapy of melanoma.

Animals↗
PubMed2004

The role of fibroblasts in the modulation of integrin-dependent interactions between the gastric cell line HGT-1 and fibronectin.

Fibronectin plays an important role in gastric cancer progression. However, little is known about the microenvironmental factors modulating integrin-dependent interactions between gastric cancer cells and fibronectin. We therefore studied the regulation by fibroblasts of the integrin-dependent adhesion and migration of the gastric cancer cell line HGT-1 onto fibronectin. We first determined, by immunofluorescence, immunoblotting and flow cytometry, that HGT-1 cells expressed alpha3, alpha5, alpha6, alphaV and beta1 integrin chains, and the alphaVbeta3 and alphaVbeta5 dimers. We verified that HGT-1 cells xenografted to the immunosuppressed newborn rat retained the integrin repertoire detected in vitro and were able to induce the formation of tumors rich in fibronectin. By using an in vitro assay in the presence of neutralizing antibodies, we verified that HGT-1 adhesion and migration onto fibronectin involved beta1, alphaV and alpha5 integrin chains; we verified, by using an in situ adhesion test to rat gastric wall frozen sections, that in situ HGT-1 adhesion to fibronectin was integrin dependent. In coculture experiments, we showed that organ-specific fibroblasts from stomach, lung and dermis were able to induce, in a site-specific manner, the expression of beta1, alpha5 and alphaV integrin chains in HGT-1 cells, their integrin-dependent adhesion and migration on fibronectin and their capacity to secrete oncofetal fibronectin. In conclusion, our results show the capacity for tissue-derived fibroblasts to modulate the integrin-dependent interactions between the gastric cell line HGT-1 and fibronectin. They strongly suggest that, in gastric cancer, stromal fibroblasts contribute to promote fibronectin-mediated local invasion by tumor cells.

Animals↗
PubMed2005

Visinin-like protein-1 is a potent inhibitor of cell adhesion and migration in squamous carcinoma cells.

Tumor cell invasion is a highly integrated and complex process comprising several biologically distinct functions such as cell adhesion, motility, proteolysis, etc. Visinin-like protein-1 (VILIP-1), a member of the neuronal EF-hand calcium-sensor protein family, plays a role in regulating tumor cell invasiveness of mouse squamous cell carcinoma (SCC). VILIP-1 enhances cyclic adenosine monophosphate levels through PKA induction. However, the mechanism by which VILIP-1 reduces cell invasiveness is not well understood. In this study, we show that VILIP-1 decreased cell adhesion and migration/invasiveness of highly invasive mouse SCC cells. Forced expression of VILIP-1 reduced cell adhesion to fibronectin in parallel to downregulating alphav and alpha5 integrin subunit levels. VILIP-1 overexpression also led to decreased migration ability. Conversely, short hairpin RNA-mediated VILIP-1 knock-down of SCC cells' characterized by little or no invasiveness, correlated with increased adhesion to fibronectin and enhanced expression of alphav and alpha5 integrin subunits together with increased cell migration. Function-blocking assays with inhibitory anti-alpha5 and anti-alphav integrin antibodies showed that both subunits contributed to cell adhesion, migration, and invasiveness of highly invasive SCC cell lines. These results point to a critical role of VILIP-1 in regulating cell adhesion and migration by downregulation of fibronectin receptor expression. Decreased or absent VILIP-1 expression in SCC cell subpopulations may lead to a more advanced malignant phenotype characterized by changes in adhesive ability and increased cell motility, suggestive of a tumor suppressor function.

Animals↗
PubMed1998

Osteopontin stimulates a subpopulation of quiescent human prostate epithelial cells with high proliferative potential to divide in vitro.

BACKGROUND: Osteopontin (OPN) is a secreted extracellular matrix (ECM) protein found in bone, as well as associated with epithelial cells. The main objective of these studies was to test in vitro the hypothesis that interaction with OPN stimulates proliferation of a quiescent subpopulation of prostate epithelial cells with high proliferative potential. METHODS: To simulate conditions that restrict proliferation and inhibit terminal differentiation of basal cells in vivo, control cultures grew on substrate coated with collagen (CO) or fibronectin (FN), in medium containing low levels of growth factors. RESULTS: Under growth-restricting conditions, most prostate epithelial cells with high proliferative potential, seeded in control secondary cultures, were quiescent within the time frame of the studies, as indicated by the small number of large colonies in these cultures. Growing prostate epithelial cells (PR) under the same growth-restricting conditions, but on substrate coated with OPN instead of CO or FN, stimulated proliferation of a subpopulation of single cells with high proliferative ability as indicated by: 1) dose-dependent increase in the percentage of single cells incorporating bromodeoxyuridine, i.e., proliferating PR; and 2) subsequent dose-dependent increase in the percentage of large colonies. The OPN effect was not merely due to preferential attachment to OPN, because PR attachment to OPN, CO, or FN was identical. PR attachment to OPN was inhibited in the presence of GRGDTP or an antibody against the integrin subunit alphav, but not in the presence of an RGES peptide or a nonspecific IgG. CONCLUSIONS: Integrin-mediated OPN/PR interaction stimulates proliferation of a quiescent subpopulation of prostate epithelial cells with high proliferative potential, possibly stem cells.

Cell Adhesion↗
PubMed2004

Alphavbeta integrins play an essential role in BMP-2 induction of osteoblast differentiation.

UNLABELLED: Both integrins and BMP-2 exert similar effects on osteoblasts. We examined the relationship between the alphav-containing integrins (alphavbeta) and BMP-2 in osteoblast function. BMP-2 stimulates alphavbeta expression. BMP-2 receptors co-localize/overlap with alphavbeta integrins, and the intact function of alphavbeta is essential in BMP-2 activity. INTRODUCTION: Bone morphogenetic protein (BMP)-2 not only induces osteoblast differentiation and bone matrix mineralization, but also stimulates osteoblast migration on and adhesion to bone matrix proteins. The alphavbeta- and beta1- (alphabeta1) containing integrins mediate osteoblast interaction with many bone matrix proteins and play important roles in osteoblast adhesion, migration, and differentiation. Because alphavbeta integrins and BMP-2 share common effects on osteoblasts, we analyzed their relationship in osteoblast function. MATERIALS AND METHODS: The effects of BMP-2 on integrin expression were determined by surface labeling/immunoprecipitation and cell adhesion to matrix proteins. Confocal analysis of the immunostained cells and co-immunoprecipitation of cell extracts were used to study the spatial relationship between integrins and BMP-2 receptors. A function-blocking anti-alphavbeta integrin antibody (L230) was employed to investigate the roles of alphavbeta integrins in BMP-2 function. RESULTS: Human osteoblasts (HOBs) express alphabeta1, alphavbeta3, alphavbeta5, alphavbeta6, and alphavbeta8 integrins at focal adhesion sites. BMP-2 increases the levels of these integrins on osteoblast surface and enhances HOB adhesion to osteopontin and vitronectin. Immunoprecipitation and immunostaining analyses show that BMP-2 receptors co-localize or overlap with alphavbeta and alphabeta1 integrins. Incubation of HOBs with L230 abolishes the antiproliferative effect of BMP-2 and reduces the capacity of BMP-2 to stimulate alkaline phosphatase activity and the expression of osteocalcin, osteopontin, and bone sialoprotein. Furthermore, L230 prevents BMP-2 induction of matrix mineralization. Although BMP-2 retains its receptor-binding capability in the presence of L230, BMP-2 stimulation of Smad signaling is abolished by L230. CONCLUSION: BMP-2 upregulates the expression of alphavbeta integrins, and these integrins, in turn, play a critical role in BMP-2 function in osteoblasts.

Alkaline Phosphatase↗
PubMed2004

Osteopontin regulates multiple functions contributing to human colon cancer development and progression.

Osteopontin (OPN) is a secreted phosphoglycoprotein known to interact with a number of integrin receptors. While increased OPN expression has been reported in a number of human cancers, and its cognate receptors (alphav-beta3, alphav-beta5, and alphav-beta1 integrins and CD44) have been identified, its role in colon cancer development and progression has not been extensively studied. We previously identified, using a combination of gene expression and tissue microarrays, that increased OPN expression is concordant with tumor stage. The current study examined the functional role of OPN in colon cancer progression and metastatic potential. The principal findings of this study were that both endogenous OPN expression (via stable transfection) as well as exogenous OPN (added to culture medium) enhanced the motility and invasive capacity of human colon cancer cells in vitro. OPN appeared to regulate motility though interaction with CD44. OPN expression also reduced intercellular (homotypic) adhesion, an important characteristic of metastatic cancer cells. Stable transfection of four poorly tumorigenic human colon cancer cell lines with OPN also resulted in enhanced tumorigenicity in vivo with increased proliferation and increased CD31 positive microvessel counts, concordant with the degree of OPN expression. Collectively, these results suggest that OPN may affect multiple functional components contributing to human colon cancer progression and solidifies its role in this process.

Animals↗
PubMed2002

Role of integrin alphaVbeta3 in the production of recombinant adenoviruses in HEK-293 cells.

Adenoviral infection is initiated by attachment of adenoviral fiber proteins to the CAR protein and subsequent internalization aided by alphaV -containing integrins, eg alphaVbeta3 and alphaVbeta5. To further understand the process of infection and assembly of recombinant adenoviral (rAd) vectors, we examined rAd production in HEK-293 cells and one of its subclones, clone D, isolated from the parental cells for high viral production. By flow cytometry, surface expression of integrin alphaVbeta3 by clone D cells was two-fold higher than by HEK-293 cells. However, clone D cells did not demonstrate greater translational efficiency or number of viral genome DNA copies shortly after rAd infection. Treating cells with inhibitors of integrin alphaVbeta3 reduced rAd production and transfecting HEK-293 cells with integrin alphaVbeta3 cDNAs increased rAd production. Subjecting cells to a sudden reduction in serum (10% to 0.1% FCS) for 5 days, clone D cells maintained 80% viability compared with 40% for HEK-293 cells. Further indication of survival signaling involvement was provided by Western blot analysis demonstrating p38 and p44/42 MAPKs were constitutively phosphorylated in HEK-293 cells. However, for clone D cells, p38 MAPK was phosphorylated only after rAd infection. The role of survival signaling mediated by integrin alphaVbeta3 in rAd production will be discussed.

ATPases Associated with Diverse Cellular Activitie↗
PubMed1998

Expression of the human integrin beta6 subunit in alveolar type II cells and bronchiolar epithelial cells reverses lung inflammation in beta6 knockout mice.

Inactivation of the integrin beta6 subunit gene in mice resulted in an unexpected phenotype-functionally significant inflammation of the skin and lungs. These findings suggested a role for ligation of the alphav beta6 integrin on epithelial cells in downregulating epithelial inflammation. However, the results of gene inactivation could have been due to inactivation of adjacent genes and provided no information about the role of this integrin in specific populations of epithelial cells. In the current study, we used transgenic mice constitutively expressing the human beta6 subunit in alveolar type II cells and bronchiolar epithelial cells to examine directly the significance of alphav beta6 in these cells. Expression of this transgene largely inhibited the increases in airspace lymphocytes and macrophages and the lymphocyte and macrophage activation caused by inactivation of the beta6 subunit gene, and reduced the peribronchial and perivascular accumulations of lymphocytes. In the genetically mixed mice used for this study, we identified airway eosinophilia as an additional effect of beta6 inactivation. This effect was also partially inhibited by limited expression of the human transgene. These results definitively identify a role for distal lung epithelial alphav beta6 in downregulating pulmonary inflammation and suggest that interventions augmenting beta6 expression or function in these cells could influence the course of inflammatory lung diseases.

Animals↗
PubMed2005

Functional effects of transforming growth factor beta on adhesive properties of porcine trophectoderm.

In pigs, expression and amounts of biologically active TGFbetas at the conceptus-maternal interface increase significantly as conceptuses elongate and begin the implantation process. Before their activation, secreted TGFbetas are noncovalently associated with their respective, isoform-specific latency-associated peptides (LAPs), which contain the Arg-Gly-Asp (RGD) amino acid sequence that serves as a ligand for numerous integrins. Objectives of this study were to determine whether TGFbeta1 increases production of fibronectin by porcine trophectoderm, whether porcine trophectoderm adheres specifically to fibronectin and LAP, and whether functional interactions between porcine trophectoderm and the two TGFbeta-associated proteins, fibronectin and LAP, are integrin mediated. Porcine trophectoderm cells (pTr2) were cultured in presence of TGFbeta1, LAP, or pan-neutralizing anti-TGFbeta antibody; TGFbeta specifically increased (P < 0.05) fibronectin mRNA levels, as determined by Northern and slot blot analyses. Immunofluorescence microscopy demonstrated a TGFbeta-induced increase in fibronectin in pTr2 cells. In dispersed cell adhesion assays, adhesion of pTr2 cells to fibronectin was inhibited by an RGD-containing peptide (P < 0.05) and pTr2 cells attached to recombinant LAP but not to an LAP mutant, which contained an RGE sequence rather than the RGD site (P < 0.05). Fibronectin- and LAP-coated microbeads induced integrin activation at apical surfaces of both trophectoderm and uterine luminal epithelial cells, as indicated by aggregation and transmembrane accumulation of talin detected with immunofluorescence microscopy. Cell surface biotinylation and immunoprecipitation revealed integrin subunits alphav and beta1 on apical membranes of pTr2 cells. These results suggest multiple effects of TGFbeta at the porcine conceptus-maternal interface, including integrin-mediated conceptus-maternal communication through LAP.

Animals↗
PubMed2006

Increased expression of integrin alphavbeta5 induces the myofibroblastic differentiation of dermal fibroblasts.

The biological effect of cytokines is mainly determined by the cytokine-receptor interaction, which is modulated by the concentration and the activity of cytokines and/or their receptors. Because alphav-containing integrins can bind to and/or activate latent TGF-beta, these integrins have been thought to be involved in the pathogenesis of fibrotic disorders. Our recent observations that alphavbeta5 is up-regulated in scleroderma fibroblasts and that the transient overexpression of alphavbeta5 increases the human alpha2(I) collagen gene expression in normal fibroblasts suggest the involvement of alphavbeta5 in the self-activation system in scleroderma fibroblasts. In this study, we established stable transfectants with alphavbeta5 using normal dermal fibroblasts and demonstrated that such cells differentiated into myofibroblasts by the stimulation of autocrine TGF-beta. This observation is explained by 1) alphavbeta5 recruiting latent TGF-beta1 on the cell surface, 2) endogenous active TGF-beta localizing on the cell surface, and 3) alphavbeta5 interacting with TGF-beta receptors. Furthermore, blockade of alphavbeta5 reversed the myofibroblastic phenotype in scleroderma fibroblasts. These data identify a novel mechanism for the establishment of autocrine TGF-beta signaling in dermal fibroblasts by the up-regulation of alphavbeta5 and suggest the possibility of regulating fibrotic disorders, especially scleroderma, by targeting this integrin.

Activin Receptors, Type I↗
PubMed1996

Osteopontin N-terminal domain contains a cryptic adhesive sequence recognized by alpha9beta1 integrin.

Osteopontin is an adhesive glycoprotein implicated in numerous diseases associated with inflammation and remodeling. There are several structural domains in osteopontin that are of particular interest. The RGD motif is a cell attachment sequence shown to be critical for cell adhesion through alphav-containing integrins. In close proximity to the RGD domain is the thrombin cleavage site. Previous observations suggest that thrombin cleavage of osteopontin occurs in vivo and may be physiologically important. To study the functional significance of osteopontin cleavage by thrombin, we made glutathione S-transferase-osteopontin fusion proteins. These proteins contain either the N- or C-terminal domains expected to be formed following thrombin cleavage at the Arg169-Ser170 peptide bond. We compared these osteopontin fragments with native osteopontin in their ability to support adhesion of several different cell lines and identified the receptors mediating these interactions. Our data show that the N-terminal osteopontin fragment, which contains the RGD domain, supports adhesion of a melanoma cell line that is unable to bind native osteopontin. This suggests that osteopontin adhesive interactions may be regulated by thrombin cleavage. We also demonstrate that osteopontin contains a cryptic binding activity, which can be recognized by a novel osteopontin receptor. This receptor has been identified as the alpha9beta1 integrin.

Animals↗