PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Receptors, Fibronectin”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 37 records · Page 2Linked to original sources
PubMed1986

Regulation of fibronectin receptor distribution by transformation, exogenous fibronectin, and synthetic peptides.

Recent studies have shown that fibronectin and its 140K membrane receptor complex are spatially associated with microfilaments to form cell surface linkage complexes which are thought to mediate adhesive interactions between fibroblasts and their substrata. We examined the regulation of the organization of these cell surface structures in transformed and fibronectin-reconstituted cells as well as in cells treated with a competitive synthetic peptide inhibitor of fibronectin binding to its receptor. Correlative localization experiments with interference reflection microscopy and double-label or triple-label immunofluorescence revealed a concomitant loss of fibronectin, 140K receptor, and alpha-actinin colocalization at cell substratum extracellular matrix contact sites after transformation of chick fibroblasts by wild-type or temperature-sensitive Rous sarcoma viruses (RSV). Western and dot immunoblot analyses established that although similar total quantities of intact 140K molecules were present in the transformed cell cultures, significantly more was released into the culture medium of transformed cells. The 140K molecules on transformed cells were available for interaction with exogenously added fibronectin, which could reconstitute fibronectin-140K linkage complexes. In such fibronectin reconstitution experiments, many cells expressed both fibronectin-140K-actin linkage complexes and RSV pp60src, indicating that the morphological reversion could occur even in the continued presence of RSV transformation. The synthetic peptide Gly-Arg-Gly-Asp-Ser derived from the sequence of the cell-binding region of fibronectin could also prevent the organization of fibronectin-140K linkage complexes. Our results suggest that fibronectin interaction with cells regulates the organization of fibronectin receptor complexes and cytoskeletal components at the cell surface.

Actinin↗
PubMed1989

Activation of CD4 cells by fibronectin and anti-CD3 antibody. A synergistic effect mediated by the VLA-5 fibronectin receptor complex.

In this study, fibronectin synergized with anti-CD3 antibody to promote CD4 cell proliferation in a serum-free culture system. The cell-adhesive domain plus additional regions of the fibronectin molecule are involved in this synergy. Anti4B4(CDw29) antibody blocked the activation of CD4 cells in this system. Furthermore, it is the VLA-5 protein within the set of molecules recognized by anti-4B4 that serves as a fibronectin receptor on the CD4 lymphocytes. The VLA-5 fibronectin receptor was mainly expressed on CD4+ CD45R-CDw29+ cells and may in part contribute to the unique function of these cells.

Antibodies, Monoclonal↗
PubMed1992

Regulation of fibronectin receptor distribution.

To determine the role of each intracellular domain of the fibronectin receptor in receptor distribution, chimeric receptors were constructed containing the human interleukin-2 receptor (gp55 subunit) as the extracellular and transmembrane domains, in combination with either the alpha 5 or beta 1 intracellular domain of the fibronectin receptor as the cytoplasmic domain. These chimeric receptors were transiently expressed in normal fibroblasts, and their localization on the cell surface was determined by immunofluorescence using antibodies to the human interleukin-2 receptor. The alpha 5 chimera was expressed diffusely on the plasma membrane. The beta 1 chimera, however, colocalized with the endogenous fibronectin receptor at focal contacts of cells spread on fibronectin. On cells spread in the presence of serum, the beta 1 chimera colocalized both with the fibronectin receptor at sites of extracellular fibronectin fibrils and with the vitronectin receptor at focal contacts. The beta 1 intracellular domain alone, therefore, contains sufficient information to target the chimeric receptor to regions of the cell where ligand-occupied integrin receptors are concentrated. The finding that the beta 1 chimeric protein behaves like a ligand-occupied receptor, even though the beta 1 chimera cannot itself bind extracellular ligand, suggests an intracellular difference between occupied and unoccupied receptors, and predicts that the distribution of integrin receptors can be regulated by ligand occupancy. We tested this prediction by providing a soluble cell-binding fragment of fibronectin to cells spread on laminin. Under conditions preventing further ligand adsorption to the substrate, this treatment nevertheless resulted in the relocation of diffuse fibronectin receptors to focal contacts. Similarly, a redistribution of diffuse vitronectin receptors to focal contacts occurred on cells spread on laminin after the addition of the small soluble peptide GRGDS. We conclude that the propensity for receptor redistribution to focal contacts driven by the beta 1 cytoplasmic domain alone is suppressed in heterodimeric unoccupied fibronectin receptors, and that ligand occupancy can release this constraint. This redistribution of integrin receptors after the binding of a soluble substrate molecule may provide a direct means of assembling adhesion sites.

Amino Acid Sequence↗
PubMed1996

Graded fibronectin receptor aggregation in migrating cells.

We have examined the distribution of the integrin fibronectin receptor in migrating NIH 3T3 fibroblasts to test the hypothesis that cell locomotion involves regional differences of adhesive receptor aggregation. A distinct asymmetry of fibronectin receptor aggregation was observed on the surface of migrating NIH 3T3 fibroblasts. Direct current electric fields were used to stimulate directional cell migration and thus allow the quantitative correlation of receptor asymmetries to the direction of cell locomotion. Digital particle analysis of fluorescent confocal micrographs demonstrates that the leading half of cells has a higher proportion of receptors contained in small clusters than does the trailing half. Conversely, larger receptor aggregates are more prevalent in the rear of the cell than in the front. We have also observed a gradient of extracellular fibronectin fibril assembly, similar to that described for the fibronectin receptor. Extracellular fibronectin appears in progressively larger fibrils across the ventral cell surface from front to rear, with dense meshworks often deposited as a trail behind the cell. Large fibronectin receptor clusters toward the rear of the cell generally do not correlate with focal contacts, and are thus most likely aggregated by cell surface-bound fibronectin fibrils and not by adhesion to the substratum. These results suggest that spatial variations in the degree of adhesive receptor aggregation are created in fibroblasts during the processes of migration and matrix synthesis.

3T3 Cells↗
PubMed1987

Identification of fibronectin receptors on T lymphocytes.

We report the identification of fibronectin receptors on thymocytes and T lymphoma cells. Affinity chromatography of extracts of the T cell lymphoma, WR16.1, on a fibronectin-Sepharose column combined with specific elution using a synthetic peptide containing the cell attachment-promoting sequence, arginine-glycine-aspartic acid, yielded two polypeptide components having apparent molecular masses of approximately 160 kD reduced and 175 and 150 kD nonreduced. Immunoprecipitations from surface-iodinated WR16.1 cells or fibronectin-adherent thymocytes using a rabbit antiserum raised against the fibronectin receptor that is present on human fibroblasts revealed, in each case, the same two radiolabeled components. In contrast, immunoprecipitation from fibronectin-nonadherent T lymphoma cells, designated WR2.3, revealed the presence of only the smaller subunit. Although the lymphocyte receptor and the fibronectin receptor identified on fibroblasts share immunologic determinants, they differ in that the molecular mass of the lymphocyte protein is larger. Moreover, trypsinization of either thymocytes or the WR16.1 T lymphoma cells resulted in a subsequent loss of their ability to adhere to fibronectin-coated substrates and a reduction in the electrophoretic mobility of each of the polypeptide chains of the fibronectin receptor present on their surfaces. These changes, however, were not observed with normal rat kidney fibroblasts or mouse 3T3 fibroblasts in response to trypsinization. The data establish the existence on normal lymphocytes of fibronectin receptors that are quite similar to those found on fibroblasts. The possible function of this molecule on thymocytes is discussed.

Animals↗
PubMed1989

Endocytosis and recycling of the fibronectin receptor in CHO cells.

An anti-fibronectin receptor monoclonal antibody preferentially labels the leading edges of freshly plated CHO fibroblasts, suggesting that this receptor circulates through the endocytic cycle. Using a new labelling reagent, I show that this receptor is indeed endocytosed at 37 degrees C and then returned to the cell surface. These findings imply that fibronectin receptors are recirculated to the leading edge of a motile cell by the endocytic cycle, and establish that the processes of endocytosis/exocytosis and cell locomotion are intimately linked.

Animals↗
PubMed1998

Role of fibronectin-stimulated tumor cell migration in glioma invasion in vivo: clinical significance of fibronectin and fibronectin receptor expressed in human glioma tissues.

In order to clarify the role of fibronectin in glioma invasion in vivo, we analyzed the relationship between fibronectin-stimulated cell migration and adhesion in 14 primary glioma cells and the expression of fibronectin and the fibronectin receptor in the corresponding tumor tissues. The tumors comprised nine glioblastomas (GB) and five anaplastic gliomas (AG) consisting of two astrocytomas, two oligoastrocytomas and one ependymoma. All glioma cells tested in the primary cell culture were found to migrate to fibronectin in a dose-dependent manner. The extent of cell migration to fibronectin was not significantly different for the GB and AG groups. On the other hand, cell adhesion to fibronectin in the AG was much stronger than that in the GB group. Immunohistochemistry demonstrated that fibronectin positively stained in the extracellular matrix (ECM) in eight cases and that the fibronectin receptor was positive in tumor cell membranes in 10 cases. In addition, cellular fibronectin isoforms containing ED-A and ED-B sequences were found to be immunolocalized in the tumor cells and the ECM of GB. These isoforms were also specifically expressed in tumor vessels within tumor tissues, but not in those within normal brain tissues. Cell migration tended to be expressed more strongly by glioma cells derived from tumor tissues in which fibronectin was positively immunolocalized in the ECM than from tissues with negative fibronectin in the ECM. Four glioma cells derived from GB whose tumor cells did not positively stain for fibronectin receptors migrated much less extensively to fibronectin than other glioma cells whose tissues showed positive staining for the fibronectin receptor. Of these four GB, two had loss of heterozygosity in the locus of fibronectin receptor beta1 gene. These results suggest that fibronectin deposited in the extracellular matrix of tumors, which can be derived from both plasma and the tumor cell itself, strongly promotes the migration of glioma cells, and that expression of the fibronectin receptor may play a critical role in the biological behavior of the tumor cells, particularly in fibronectin-stimulated cell migration in vivo.

Astrocytoma↗
PubMed1987

Association between fibronectin receptor and the substratum: spare receptors for cell adhesion.

We have investigated the association of the recently described 140-kDa cell membrane receptor for fibronectin with the cytoskeleton or with substratum-bound fibronectin. Using a monospecific polyclonal antibody to the 140-kDa receptor, we have demonstrated that most of the receptor molecules are soluble in nonionic detergent either in suspension culture CHO cells or in CHO cells attached to and spread on a fibronectin-coated substratum. This may suggest that putative linkages of the receptor either to fibronectin or to detergent-insoluble cytoskeletal components are labile to nonionic detergent and thus are rather weak. Alternatively, it may mean that only a small fraction of the cell's receptors are needed to mediate adhesion. In order to explore this latter concept, we have coated substrata with various concentrations of PB1, a monoclonal antibody with a high affinity for fibronectin receptor. We demonstrate that coating the substratum with increasing concentrations of PB1 results in increasing amounts of 140-kDa receptor becoming bound to the substratum in detergent-insoluble form. However, the amount of receptor bound does not necessarily correlate with the degree of cell adhesion and spreading. Thus, coating the substratum with 5 micrograms/ml of PB1 results in essentially complete attachment and spreading of CHO cells, but only a small fraction of the 140-kDa receptor becomes substratum bound. Coating with 50 micrograms/ml of PB1 produces no further increase in cell adhesion and spreading, but results in the detergent-stable association of a large fraction of the total receptor pool with the substratum. These observations suggest the possibility of there being "spare" receptors for cell adhesion processes.

Animals↗
PubMed1999

The muscle-specific laminin receptor alpha7 beta1 integrin negatively regulates alpha5 beta1 fibronectin receptor function.

alpha7 beta1 is the major integrin complex expressed in differentiated muscle cells where it functions as a laminin receptor. In this work we have expressed the alpha7 integrin subunit in CHO cells to investigate the functional properties of this receptor. After transfection with alpha7 CHO cells acquired the ability to adhere and spread on laminin 1 consistent with the laminin receptor activity of the alpha7 beta1. alpha7 transfectants, however, showed a 70% reduction in the ability to adhere to fibronectin and were unable to assemble a fibronectin matrix. The degree of reduction was inversely related to the level of alpha7 expression. To define the mechanisms underlying this adhesive defect we analyzed surface expression and functional properties of the alpha5 beta1 fibronectin receptor. Although cell surface expression of alpha5 beta1 was reduced by a factor of 20-25% in alpha7 transfectants compared to control untransfected cells, this slight reduction was not sufficient to explain the dramatic reduction in cell adhesion (70%) and matrix assembly (close to 100%). Binding studies showed that the affinity of 125I-fibronectin for its surface receptor was decreased by 50% in alpha7 transfectants, indicating that the alpha5 beta1 integrin is partially inactivated in these cells. Inactivation can be reversed by Mn2+, a cation known to increase integrin affinity for their ligands. In fact, incubation of cells with Mn2+ restored fibronectin binding affinity, adhesion to fibronectin, and assembly of fibronectin matrix in alpha7 transfectants. These data indicate that alpha7 expression leads to the functional down regulation of alpha5beta1 integrin by decreasing ligand binding affinity and surface expression. In conclusion, the data reported establish the existence of a negative cooperativity between alpha7 and alpha5 integrins that may be important in determining functional regulation of integrins during myogenic differentiation.

Amino Acid Sequence↗
PubMed1989

The localization of fibronectin and 140 Kd fibronectin receptor in the truncus arteriosus of the chick embryonic heart.

The distribution of fibronectin and 140 Kd fibronectin-receptor was examined in the truncus arteriosus of the chick embryonic heart during aortico-pulmonary (AP) septation by immunohistochemistry. In 4-day-old chick embryos, immunoreactivity of both anti-fibronectin and anti-140 Kd fibronectin-receptor was seen in the primordia of the AP septum. In 5-day-old embryos, cells stained with anti-140 Kd fibronectin-receptor antibody were rarely found in the AP septum, though strong immunoreactivity of the anti-fibronectin antibody was observed in the AP septum. In 6-day-old embryos, at a late stage of septation, cells stained with anti-140 Kd fibronectin-receptor antibody were not found in the AP septum, and immunoreactivity of the anti-fibronectin antibody had decreased. In the cushion tissue, immunoreactivity of the anti-fibronectin antibody was seen, but that of the anti-140 Kd fibronectin-receptor antibody was recognizable only on a few cushion cells in the 4-day-old embryos. These findings suggest that fibronectin is involved in the formation of the AP septum primordia, that fibronectin does not promote the development of the AP septum, and that the migration mechanism of cushion cells is different from that of neural crest cells.

Animals↗
PubMed1992

Cloning and expression of two different genes from Streptococcus dysgalactiae encoding fibronectin receptors.

Binding of bacteria to fibronectin has been implicated as a mechanism of bacterial adhesion to the host tissue. In this report we have analyzed the binding of a strain of Streptococcus dysgalactiae to fibronectin. The cells bind to a site in the NH2-terminal domain of the protein via trypsin-sensitive cell surface components. Furthermore, a lysate prepared by sonication of streptococcal cells contained fibronectin-binding proteins that inhibit the binding of the ligand to intact bacteria. When the proteins were separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, blotted to an Immobilon-P filter, and probed with 125I-labeled fibronectin, a 140-kDa fibronectin-binding protein was identified along with a number of smaller binding proteins. A genomic DNA library was constructed and screened for the expression of fibronectin-binding proteins. Two clones were isolated and shown to contain unrelated inserts by restriction mapping and cross-hybridization experiments. The two encoded proteins were also immunologically distinct although both bound to the same region of the fibronectin molecule, and both effectively inhibited the binding of 125I-fibronectin to bacterial cells. Immunological analyses showed that only one of the two proteins tentatively identified as fibronectin receptors was expressed in detectable quantities in the Streptococcus dysgalactiae strain under the culture conditions employed.

Bacterial Adhesion↗
PubMed1988

Transforming growth factor beta stimulates the expression of fibronectin and of both subunits of the human fibronectin receptor by cultured human lung fibroblasts.

Transforming growth factors of the beta-class (TGFs-beta) stimulate extracellular matrix synthesis and have been implicated in embryogenesis, wound healing, and fibroproliferative responses to tissue injury. Because cells communicate with several extracellular matrix components via specific cell membrane receptors, we hypothesized that TGFs-beta may also regulate the expression of such receptors. We confirmed that TGF-beta 1 increases the expression of fibronectin, an adhesive glycoprotein expressed during embryogenesis and tissue remodeling. Based upon the 48-72-h period required for a maximal fibroproliferative response to dermal injections of TGF-beta 1, we exposed human fetal lung fibroblasts (IMR-90) to TGF-beta 1 for periods up to 48 h in vitro. We observed as much as 6-fold increases in fibronectin synthesis by 24 h as previously reported for fibroblastic cells (Ignotz, R. A., and Massagué, J. (1986) J. Biol. Chem. 261, 4337-4345; Ignotz, R. A., Endo, T., and Massagué, J. (1987) J. Biol. Chem. 262, 6443-6446; Raghow, R., Postlethwaithe, A. E., Keski-Oja, J., Moses, H. L., and Kang, A. H. (1987) J. Clin. Invest. 79, 1285-1288), but up to 30-fold increases by 48 h. These increases are accompanied by similar increases in fibronectin mRNA levels which are prevented by actinomycin D treatment. Using a monospecific antibody raised to the human placental fibronectin receptor complex, we found that TGF-beta 1 stimulated fibronectin receptor synthesis up to 20-40-fold and increases mRNA levels encoding both the alpha- and beta-subunits up to 3-fold, compared to control IMR-90 in serum-free medium. Actinomycin D blocks TGF-beta 1-mediated increases in receptor mRNA levels. The earliest detectable TGF-beta 1-mediated increases in fibronectin receptor complex protein synthesis and mRNA levels occur at 8 h, whereas the earliest increases in fibronectin protein synthesis and mRNA levels occur at 12 h. These results demonstrate that TGF-beta 1 stimulates fibronectin receptor synthesis, extending the diverse stimulatory activities of this polypeptide to matrix receptors. In addition, because fibronectin matrix assembly may involve the fibronectin cell adhesive receptor complex, increased receptor expression may help drive fibronectin deposition into matrix.

Cell Line↗
PubMed1988

Electron microscopy and structural model of human fibronectin receptor.

Highly-purified human fibronectin receptor (a heterodimer of two distinct subunits, alpha and beta) was studied using electron microscopy and a variety of preparative procedures. It was found that the receptor consists of a globular head approximately 80 by 120 A and two tails about 20 A thick and 180-200 A long. The whole complex is approximately 280 A long. At low concentrations of detergent the receptor forms doublets, triplets or rosettes associated with the tails which possess the transmembrane portion of the molecule. Computer-assisted structure prediction using the published amino acid sequence of both subunits showed differences in the secondary structure of the tails, the alpha-tail being rich in beta-strands, the beta-tail having five cysteine-rich repeats analogous to the EGF-like repeats of laminin. Estimates of the length of the tails from the predicted structure conformed well with the dimensions obtained from electron micrographs.

Amino Acid Sequence↗
PubMed1994

Activation of beta 1 integrin fibronectin receptors on HL60 cells after granulocytic differentiation.

Phorbol esters upregulate the functional affinity of beta 1 integrin receptors for fibronectin on human neutrophils and other leukocytes. We investigated the ability of phorbol myristate acetate (PMA) to stimulate the human promyelocytic cell line HL-60 to adhere to fibronectin, either in its undifferentiated state (HL60) or after dimethylsulfoxide-induced differentiation along the granulocytic pathway (dHL60). PMA stimulated little adherence of undifferentiated HL60 to fibronectin or to the 120-kD chymotryptic cell-binding domain (CBD) of fibronectin. In contrast, PMA stimulated dHL60 cells to rapidly adhere to both fibronectin- and to CBD-coated plastic. PMA-stimulated dHL60 adherence to fibronectin was largely mediated by both alpha 4 beta 1 and alpha 5 beta 1, whereas PMA-stimulated dHL60 adherence to CBD was largely mediated by alpha 5 beta 1. There was little contribution from beta 2 integrins to PMA-stimulated dHL60 adherence to fibronectin or CBD. The inability of undifferentiated HL60 to adhere to fibronectin and CBD did not result from lack of expression of alpha 4 beta 1 or alpha 5 beta 1 because HL60 and dHL60 express similar amounts of both alpha 4 beta 1 and alpha 5 beta 1 on their surface. In addition, 1 mmol/L Mn2+ induced similar amounts of alpha 5 beta 1-dependent adherence of both HL60 and dHL60, showing that alpha 5 beta 1 on undifferentiated HL60 is capable of binding to its ligand. These data suggest that activation of protein kinase C cannot functionally upregulate these beta 1 integrins on undifferentiated HL60 cells. The development of PMA-stimulated beta 1-dependent adherence after granulocytic differentiation of HL60 cells suggests that the differentiated HL60 cell is a useful model for investigating functional coupling of protein kinase C to beta 1 integrin in myeloid cells.

Animals↗
PubMed1988

Fibronectin receptors of phagocytes. Characterization of the Arg-Gly-Asp binding proteins of human monocytes and polymorphonuclear leukocytes.

We have defined the cell surface molecules of human monocytes and PMN that bind to the chymotryptic cell binding domain of Fn and to a synthetic peptide, KYAVTGRGDS, based on the sequence of Fn, by affinity chromatography. Monocytes express two receptors that differ in their affinity for CBD-Sepharose and peptide-Sepharose, but that both recognize the RGD sequence. Only a single receptor is purified from PMN, which resembles the monocyte surface molecule that binds to peptide-Sepharose. These receptors are not part of the Mac-1, LFA-1, p(150,95) family, but do have homology to the platelet Fn receptor, gpIIb/IIIa. Interestingly, the antigenic crossreactivity between gpIIb/IIIa and the phagocyte receptors purified on peptide-Sepharose is largely in the beta chain of the receptors. The alpha chains appear to be distinct, based on molecular weight, antigenic analysis, and ligand specificity. This receptor also seems to be the surface molecule on monocytes that is critical for phagocytosis enhancement by Fn. Thus, we have defined the phagocyte Fn receptor that transduces the signal for increased phagocytosis by monocytes; it may be a third member of a family of adhesion molecules that includes the gpIIb/IIIa of platelets and the vitronectin receptor of fibroblasts.

Amino Acid Sequence↗
PubMed1988

Multiple very late antigen (VLA) heterodimers on platelets. Evidence for distinct VLA-2, VLA-5 (fibronectin receptor), and VLA-6 structures.

After removal of very late antigen (VLA) 2 material from a radiolabeled detergent lysate of platelets, another VLA heterodimer was precipitated using antibody to the common VLA beta subunit. This structure was identified as VLA-5 because it contained VLA beta plus an alpha subunit that was (i) recognized by anti-alpha 5 antibodies and (ii) cleaved by V8 protease to yield a characteristic alpha 5-like pattern of peptide fragments. Besides VLA-2 and VLA-5, a third heterodimer, here named VLA-6, was also present on platelets. VLA-6 (an alpha 6 beta complex) was defined using the monoclonal antibody GoH3 (Sonnenberg, A., Janssen, H., Hogervorst, F., Calafat, J., and Hilgers, J. (1987) J. Biol. Chem. 262, 10376-10383). Although it resembled VLA-5 in size, VLA-6 was different from VLA-5 because (i) removal of the alpha 5 subunit did not remove alpha 6, (ii) removal of alpha 6 by the GoH3 antibody did not remove alpha 5, (iii) the alpha 5 and alpha 6 subunits had very distinct one-dimensional V8 peptide maps, and (iv) the alpha 6 and alpha 5 subunits had distinct migration patterns on two-dimensional O'Farrell gels. The beta subunit of VLA-6 was identified as the common VLA beta subunit because (i) it was recognized by anti-VLA beta antibody and (ii) it yielded a V8 protease cleavage map characteristic of beta. VLA-6 was not readily seen in anti-VLA beta immunoprecipitations, apparently because the alpha 6 subunit is only loosely or partially associated with the VLA beta subunit. Because VLA-5 and VLA-6 both closely resemble the previously defined Ic-IIa platelet protein complex, it is likely that there is more than one platelet "Ic" protein complexed with IIa.

Antibodies, Monoclonal↗