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PubMed1988

Hydrocortisone-induced accumulation of fibronectin mRNA and cell surface-associated fibronectin.

A Morris hepatoma 7777-derived cell line, DTH-3, was used to study the control of fibronectin gene expression. In cultures of DTH-3 cells in conventional medium supplemented with serum or in chemically defined MX-83 medium supplemented with insulin no cell surface fibronectin was detectable by indirect immunofluorescence techniques using specific polyclonal antibodies. By Northern blot hybridization analysis a dose- and time-dependent accumulation of 8 kb fibronectin mRNA in response to hydrocortisone treatment was demonstrated. Furthermore, 24 h after addition of hydrocortisone an extensive fibrillar fibronectin network was established. The results suggest that the hydrocortisone-dependent induction of fibronectin production might, at least in part, be controlled at the transcriptional level.

Animals↗
PubMed1985

Appearance and persistence of fibronectin in cartilage. Specific interaction of fibronectin with collagen type II.

Binding of fibronectins (FN) to collagen types I-IV were studied using polyclonal antibodies against human and chicken FNs, proteoglycan monomers, collagen type II and monoclonal antibodies reacting with both soluble and insoluble forms of human FN. Plasma fibronectin and type II collagen were shown to interact specifically in a homologous system. Type II collagen, however, proved to be less effective in inhibition assays compared to other types of collagen. In high density cultures of chicken limb bud cells, fibronectin was first localized within the fibroblast-like cells of 4 hr cultures and an extensive extracellular filamentous network developed by the end of day 1. Fibronectin was present in the newly formed cartilage nodules although it seemed to disappear by day 6, when the proteoglycan accumulation became more intensive. Enzyme treatments (testicular hyaluronidase, chondroitinase ABC) helped to localize FN at this stage of development of chicken cartilage, in microdroplet high density cultures of human fetal chondrocytes and in articular cartilage. Fibronectin was localized only in the pericellular ring of intact human articular cartilage using monoclonal antibodies with the biotin-avidin system.

Animals↗
PubMed1987

The effect of fibronectin therapy and fibronectin deficiency on healing of rat burns and excision wounds.

Rats with standardized burns and skin excision wounds were treated i.p. with human fibronectin or swine skin gelatin. Controls received bovine albumin, solvent, or no treatment. Wound healing was assessed by planimetry, additionally plasma fibronectin was determined. Solvent or albumin did not influence the healing process, neither did fibronectin. However, when opsonizing fibronectin was additionally consumed by application of gelatin, a significant retardation of wound healing was observed. The results support the opinion that fibronectin is of essential importance for posttraumatic opsonization of gelatin-like material originating from the damaged tissue.

Animals↗
PubMed1985

The effect of proteolytic degradation of plasma fibronectin on the responses of functional and immunometric assays for intact fibronectin.

Numerous studies have been made into the nature and importance of altered levels of plasma fibronectin seen in a range of clinical disorders. However, fibronectin is highly sensitive to the proteolytic degradation which may accompany some of these conditions. The influence of such degradation on the assays used is frequently unknown. We have investigated the effects of controlled protease degradation on the responses of an electroimmuno and a functional assay, using purified fibronectin. Tryptic digestion influenced the assays more than thrombin, in relation to the degree of breakdown. Both enzymes reduced the functional (gelatin-binding) activity whilst tryptic cleavage increased the apparent concentration by electroimmunoassay. The findings demonstrate that certain assays may be inappropriate for those clinical conditions where levels of intact fibronectin are of most interest. It is also necessary, then, to determine the degree of fibronectin breakdown when measuring pathological levels.

Chromatography, High Pressure Liquid↗
PubMed1988

Altered accumulations of fibronectin are not dependent on fibronectin modifications during the differentiation of F-9 teratocarcinoma stem cells.

F-9 teratocarcinoma stem cells differentiate into parietal endoderm when monolayer cultures are treated with retinoic acid. This change in phenotype is accompanied by increased accumulation and altered organization of fibronectin deposits. Although both stem cells and treated cells synthesize and accumulate fibronectin, only the treated cells deposit a fibrillar array of the protein. We have monitored the accumulation of fibronectin in nontreated and treated F-9 cells with indirect immunofluorescence and have biochemically analyzed the fibronectin synthesized by each cell type with one- and two-dimensional acrylamide gels and peptide maps. Our data suggest that no differences exist between these fibronectins to account for the observed changes in accumulation. Thus, another mechanism may regulate the organization of matrix deposition.

Cell Line↗
PubMed1981

Independence of reciprocal attachment sites on denatured collagen and fibronectin from antigenic sites, and binding of gelatin-based plasma substitutes to plasma fibronectin.

Fibronectin and denatured collagen possess attachment sites for each other and, in addition, antigenic sites reacting with the respective antibodies. Using an enzyme linked immunosorbent assay it was shown that attachment sites and antigenic sites on fibronectin and on collagen reacted independently of each other. Gelatin-based plasma substitutes blocked the binding of fibronectin to denatured collagen thus showing that attachment sites for fibronectin are preserved in the gelatin preparations used for manufacturing these plasma substitutes. Antigenic sites, in contrast, were destroyed during the manufacturing process as shown with antibodies to denatured collagen raised in guinea-pigs. It is concluded that complex formation of gelatin-based plasma substitutes with plasma fibronectin may occur upon infusion of such plasma substitutes but that formation of antigen/antibody complexes in vivo is unlikely.

Animals↗
PubMed1986

DNA-binding domains of human plasma fibronectin. pH and calcium ion modulation of fibronectin binding to DNA and heparin.

We have studied the binding of fibronectin and its thermolysin fragments to DNA and heparin. Elution of polypeptides bound to DNA-cellulose and heparin-Sepharose affinity chromatography columns was performed by NaCl linear gradients in buffers at different pH and in the presence and absence of calcium ions. The NaCl concentration required to elute fibronectin from both types of column increased as the pH decreased. Fibronectin was not retained on DNA-cellulose or heparin-Sepharose affinity chromatography columns using a buffer containing physiological concentrations of Ca2+, Mg2+ and NaCl, at pH 7.4. On the other hand at pH 6.4 in conditions of physiological ionic strength, fibronectin was retained by both columns, eluting from the DNA-cellulose at 280 mM NaCl and from the heparin-Sepharose column at 210 mM. Furthermore, we have studied the interaction of thermolysin-digested fibronectin both with DNA-cellulose and heparin-Sepharose using the above procedure. The results demonstrate that there are four distinct domains, which interact both with DNA and heparin. We also report here the modulation by pH and Ca2+ ions of the interaction with DNA and heparin of these different domains.

Amino Acid Sequence↗
PubMed1991

Latent fibronectin-degrading serine proteinase activity in N-terminal heparin-binding domain of human plasma fibronectin.

The N-terminal 70-kDa fragment of human plasma fibronectin, purified from a cathepsin D digest, is characterized by lack of stability. It is processed proteolytically during incubation in the presence of Ca2+ into 27-kDa N-terminal heparin-binding and 45-kDa collagen-binding domains. The N-terminal residue in the 27-kDa fragment was blocked as in native fibronectin. The 45-kDa fragments began with the sequences AAVYQP, AVYQP and VYQP (residues 260, 261, 262-265 of fibronectin) that correspond to the beginning of the collagen-binding domain. In the presence of Ca2+ the purified 27-kDa fragment underwent further processing finally leading to the cleavage of the bond K85-D86 and to the simultaneous appearance of a specific proteolytic activity. Inhibition studies suggests that the newly generated enzyme is a Ca(2+)-dependent serine proteinase. Among all assayed matrix proteins, the newly generated enzyme cleaves native fibronectin and its fragments. It is proposed that this fibronectinase may originate from the N-terminal domain of fibronectin.

Amino Acid Sequence↗
PubMed2003

Microarray assessment of fibronectin, collagen and integrin expression and the role of fibronectin-collagen coating in the growth of normal, SV40 T-antigen-immortalised and malignant human oral keratinocytes.

Extracellular matrix proteins affect the growth and survival of epithelial tissues. Accordingly, surface coating with fibronectin and collagen is a common practice for promoting keratinocyte culture. In this study, the expression of fibronectin and collagen-related factors, including integrins, by normal (NOK), SV40 T-antigen-immortalised (SVpgC2a) and malignant (SqCC/Y1) human oral keratinocytes, under standardised, serum-free conditions, was investigated by using microarray analysis. Cell growth was also studied in the presence and absence of a matrix consisting of human fibronectin and bovine collagen type I (FN-COL). Fibronectin transcripts were abundant in all cells, whereas 16 of 29 collagen chains and 14 of 24 integrin subunits were variably detected. With regard to both the expression level and the number of transcripts, higher collagen and lower integrin expression was observed in SVpgC2a cells than in NOKs and SqCC/Y1 cells. The cell types differed with regard to colony-forming efficiency and the rate and kinetics of growth at high cell density. For all cell types, FN-COL coating consistently stimulated cell migration, without influencing growth in mass culture or clonal density. The results demonstrate the transcription of genes associated with the formation and function of fibronectin and collagen in oral epithelium, and variably altered expression patterns in transformed states, and show that keratinocyte lines can be successfully transferred without the stimulus from extracellular FN-COL.

Antigens, Polyomavirus Transforming↗
PubMed1990

Potential proteolytic activity of human plasma fibronectin: fibronectin gelatinase.

Human plasma fibronectin contains a latent proteinase that after activation cleaves gelatin and fibronectin. The autoactivation propensity of the two purified cathepsin D-produced fragments of fibronectin (190 and 120 kDa) was compared. Both polypeptides were spontaneously activated in the presence of Ca2+. This activation was inhibited by EDTA. The active gelatinase was isolated from the autodigest of the 190-kDa fragment. Among various protein substrates, including laminin and native type I and IV collagens, the purified enzyme degraded only gelatin and fibronectin. We have named this proteinase FN-gelatinase. FN-gelatinase is inhibited by phenylmethanesulfonyl fluoride and also by pepstatin A like retroviral aspartic proteinases. The amino-acid composition of the purified enzyme (35 kDa) was compared with the entire fibronectin sequence using the computer programme FIT. The optimal fit indicated that the 35-kDa fragment corresponds to the stretch # 1043-1404. This sequence contains a 93-residue segment (# 1140-1233) analogous to retroviral aspartic proteinases, comprising the sequence DTG of their putative active site.

Amino Acid Sequence↗
PubMedDate not supplied

Changes in fibronectin production in rat liver during cirrhotic evolution due to treatment with CCl4 and steroid hormones: correlation with plasmatic fibronectin.

Previous our studies showed that some steroid hormones, as pure crystalline Progesterone (pPc) and 17-alpha-hydroxyprogesterone capronate (17 alpha HPC) heightened the cirrhogenic action produced in rat liver by carbon tetrachloride. Medroxyprogesterone (MPA), however, did not appear to promote cirrhosis, but increased just steatosis. In the present paper, we have studied the above mentioned steroid hormones for their possible capability of inducing changes in plasma fibronectin concentration. For this purpose, the soluble plasma fibronectin level was measured in female rats 45 days after CCl4-induced cirrhosis, and it was compared with the insoluble fibronectin of liver (detected by immunostaining) and the collagen content in the organ. The results obtained show that, after treatment with CCl4 and MPA, both plasma and liver fibronectin content strongly increases, whereas liver collagen content lowers. However, after treatment with CCl4 alone or in association with the other two steroid hormones, any changes in fibronectin content is not observable, but, on the contrary, is evident a heightened collagen production associated with a cirrhotic change of liver.

17 alpha-Hydroxyprogesterone Caproate↗
PubMed1985

Inhibition of platelet adhesion to fibronectin, fibrinogen, and von Willebrand factor substrates by a synthetic tetrapeptide derived from the cell-binding domain of fibronectin.

The role in platelet function of the cell-binding region of fibronectin was explored by the use of synthetic peptides. The prototypical peptide gly-arg-gly-asp-ser was capable of inhibiting thrombin-induced platelet aggregation without altering the degree of platelet activation as judged by the secretion of 14C-serotonin. The peptide also effectively inhibited, in a concentration-dependent manner, the binding of radiolabeled fibronectin to platelets and the adhesion of platelets to fibronectin substrates. The smallest peptide from the cell-binding region of fibronectin which retained full activity was arg-gly-asp-ser. Transposition of amino acids or conservative substitutions of amino acids within this short sequence resulted in inactive peptides. Peptides containing the arg-gly-asp-ser sequence were also capable of inhibiting the adhesion of platelets to fibrinogen and von Willebrand factor substrates. Examination of the entire panel of synthetic peptides for ability to inhibit adhesion to fibrinogen or von Willebrand factor substrates revealed the same structure-function relationships that had been determined in the studies with fibronectin.

Amino Acid Sequence↗
PubMed1985

[Changes in the structure of fibronectin glycans caused by the transformation of BHK21/C13 cells induced by hamster sarcoma viruses. Hypothesis concerning metastatic diffusion by masking lectin sites of fibronectin].

Transformation of BHK21/C13 cells by the hamster sarcoma virus induces dramatic modifications of glycans of the N-acetyllactosaminic type from fibronectin secreted in the culture medium. In fact, the ratio tri + tetraantennary glycans/biantennary glycans increases from 0.73 to 2.46. Moreover, the fibronectin is enriched in sialic acid due to the increase of di-, tri- and tetrasialylated glycans. An hypothesis is proposed concerning the mechanism of metastasis on the basis of the knowledge we have now of the spatial conformation of glycans. In fact, tri- and tetraantennary glycans, in adopting an extended conformation called "umbrella-conformation", firmly maintained by ionic bonds between sialic acid and basic amino acid residues, cover large area of the protein. The enrichment of fibronectin from cancerous cells in tri- and tetraantennary glycans and, in the same time, in sialic acid could be related: (i) to the decrease or loss of reactivity of the protein moiety of fibronectin by masking the lectin sites and (ii) to the disappearance of fibronectin from cancer tissues and, consequently, (iii) to the mechanism of the metastasis itself.

Animals↗
PubMed1985

Studies on fibronectin in inflammatory vs non-inflammatory polymorphonuclear leucocytes of patients with rheumatoid arthritis. II. Synthesis and release of fibronectin in vitro.

We conducted studies dealing with the synthesis and release of fibronectin in vitro by polymorphonuclear leucocytes (PMNL). The specific purpose of our study was to look for any changes in these events as they happen in inflammatory vs non-inflammatory PMNL. We used PMNL isolated from the synovial fluid of patients with rheumatoid arthritis as a source of inflammatory cells and PMNL isolated from peripheral blood as a source of non-inflammatory cells. Marked differences were observed. Using 35S-methionine metabolic labelling and SDS-polyacrylamide gel analysis, we were first able to clearly observe an increased synthesis of fibronectin by inflammatory PMNL when compared to non-inflammatory PMNL. Furthermore, the release of fibronectin in vitro by these cells was increased by factors of up to 20 when compared to non-inflammatory peripheral blood PMNL. Experimental evidence was also obtained which strongly suggests that fibronectin exists in a stored form inside the inflammatory PMNL we used in this study. Finally, we observed that PMNL are capable of synthesizing a 95 kD gelatin binding protein which appears to be distinct from fibronectin.

Arthritis, Rheumatoid↗
PubMed1982

Carbohydrate structure of hamster plasma fibronectin. Evidence for chemical diversity between cellular and plasma fibronectins.

The structure of the carbohydrate moiety of hamster plasma fibronectin was determined. The glycopeptides and oligosaccharides released by hydrazinolysis (Fukuda, M., Kondo, T., and Osawa, T. (1976) J. Biochem. (Tokyo) 80, 1223-1232) were analyzed by methylation and exoglycosidase digestion and the major oligosaccharide unit of hamster plasma fibronectin was shown to be (formula, see text) The structure of carbohydrate moiety of plasma fibronectin shown above (NeuGly, N-glycolyl-neuraminic acid) and that of cellular fibronectin (Fukuda, M., and Hakomori, S. (1979) J. Biol. Chem. 254, 5451-5457) are distinctly different with respect to the linkage of sialic acid, the degree of sialylation and the absence or presence of fucose. These results, therefore, provide the evidence for chemical diversity between cellular (fibroblast) and plasma fibronectins.

Animals↗
PubMed1989

Coordinate induction of fibronectin, fibronectin receptor, tropomyosin, and actin genes in serum-stimulated fibroblasts.

From a collection of more than 80 nonoverlapping clones, isolated by differential screening of a lambda cDNA library prepared from serum-stimulated cells in the presence of cycloheximide, we have identified four clones that encoded for components of the cytoskeleton and extracellular matrix. DNA sequencing of clones B2, V58, TT1, and P38 demonstrated that they corresponded to beta-actin, alpha-tropomyosin, fibronectin, and the beta-subunit of fibronectin receptor. All four mRNA levels showed a detectable increase 30 min after stimulation and remained at high levels for at least 8 h. The half-lives of these mRNAs were found to be very long in contrast to those of other growth factor-inducible genes. An increase in transcription was observed for the four genes. Actin and fibronectin showed nearly maximal increase at 15 min, while fibronectin receptor and tropomyosin reached their maximum transcription at 1 h. These results demonstrated that four interacting components of the cytoskeleton and extracellular matrix are rapidly induced in stimulated quiescent cells, possibly reflecting part of the coordinate changes in gene expression that occur during embryogenesis and wound healing.

Actins↗
PubMed1988

The function of multiple extracellular matrix receptors in mediating cell adhesion to extracellular matrix: preparation of monoclonal antibodies to the fibronectin receptor that specifically inhibit cell adhesion to fibronectin and react with platelet glycoproteins Ic-IIa.

We have identified monoclonal antibodies that inhibit human cell adhesion to collagen (P1H5), fibronectin (P1F8 or P1D6), and collagen and fibronectin (P1B5) that react with a family of structurally similar glycoproteins referred to as extracellular matrix receptors (ECMRs) II, VI, and I, respectively. Each member of this family contains a unique alpha subunit, recognized by the antibodies, and a common beta subunit, each of approximately 140 kD. We show here that ECMR VI is identical to the fibronectin receptor (FNR), very late antigen (VLA) 5, and platelet glycoproteins Ic-IIa and shall be referred to as FNR. Monoclonal antibodies to FNR inhibit lymphocyte, fibroblast, and platelet adhesion to fibronectin-coated surfaces. ECMRs I, II, and FNR were differentially expressed in platelets, resting or activated lymphocytes, and myeloid, epithelial, endothelial, and fibroblast cell populations, suggesting a functional role for the receptors in vascular emigration and selective tissue localization. Tissue staining of human fetal skin localized ECMRs I and II to the basal epidermis primarily, while monoclonal antibodies to the FNR stained both the dermis and epidermis. Experiments carried out to investigate the functional roles of these receptors in mediating cell adhesion to complex extracellular matrix (ECM) produced by cells in culture revealed that complete inhibition of cell adhesion to ECM required antibodies to both the FNR and ECMR II, the collagen adhesion receptor. These results show that multiple ECMRs function in combination to mediate cell adhesion to complex EMC templates and predicts that variation in ECM composition and ECMR expression may direct cell localization to specific tissue domains.

Antibodies, Monoclonal↗
PubMed1986

Response of pulmonary macrophages to hyperoxic pulmonary injury. Acquisition of surface fibronectin and fibrin/ogen and enhanced expression of a fibronectin receptor.

The in vivo acquisition of coagulation plasma proteins on the surface of pulmonary macrophages was studied in guinea pigs breathing 95% oxygen. Fibrin/ogen and fibronectin appeared rapidly and concurrently on the surfaces of macrophages in the bronchoalveolar lavage fluid, which was judged by immunohistologic examination and flow cytometry. Pulmonary macrophages showed a parallel increase in the expression of a surface fibronectin receptor. Hyperoxic lung injury was accompanied by deposition of an extravascular pulmonary matrix of fibronectin and fibrin/ogen and depressed plasma levels of fibronectin. Binding to clot matrix proteins may lead to aggregation and retention of macrophages at sites of acute lung injury as well as alteration of cell function.

Animals↗