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PubMed1986

Opsonic activity of plasma fibronectin for Staphylococcus aureus by human alveolar macrophages: inefficacy of trypsin-sensitive staphylococcal fibronectin receptor.

The binding of 125I-fibronectin (FN) to some bacteria and the phagocytic activity of human alveolar macrophages (AM) by a culture method using 3H-labelled bacteria were examined. FN-binding of Staphylococcus aureus (S. aureus) was higher than that of gram-negative rods and was reduced markedly by trypsin-treatment. FN enhanced the uptake of S. aureus by AM in dose dependent manner. To determine whether FN-binding to S. aureus mediates the promotion of staphylococcal phagocytosis, we compared the uptake of non-treated S. aureus with that of trypsin-treated bacteria by AM. No significant difference was found between the uptake of these bacteria and no effect of FN-binding to S. aureus on the phagocytic activity. It is concluded that FN plays an essential role as a non-immune opsonin for S. aureus in the human lung which is found to be abundant in FN, and that FN-binding to S. aureus is probably not related to this effect.

Endocytosis↗
PubMedDate not supplied

Fibronectin and fibronectin receptors in lung development.

Fibronectin (FN) is a cell adhesive extracellular matrix protein highly expressed in developing lungs. Although the role of FN in lung development remains to be elucidated, several observations suggest that it plays important roles in many developmental processes. In vitro, FN can affect the migration, proliferation, differentiation, and even apoptosis of various cell types, all considered necessary for organogenesis. The cellular effects of FN are primarily mediated by cell surface heterodimeric receptors of the integrin family. Ligand binding to these receptors triggers the activation of intracellular signaling events responsible for alterations in gene transcription and, ultimately, cell function. Immunohistochemical analysis of embryos revealed increased deposition of FN during the pseudoglandular stage of lung development, coinciding with the period of branching morphogenesis. This observation, together with the strategic location of FN around developing airways predominantly at cleft sites, suggests a role in airways formation. This hypothesis is supported by studies showing that reagents capable of preventing FN-FN receptor binding inhibit branching morphogenesis in murine lung explants. Less is known about the potential role of FN in other aspects of lung development. However, in vitro studies suggest that FN may affect vessel formation, alveolar epithelial cell differentiation and lung growth and maturation.

Animals↗
PubMed1991

[Immunohistochemical localization of fibronectin, laminin and fibronectin-receptor in human malignant gliomas--in relation to tumor invasion].

In order to examine a role of extracellular matrix (ECM) components in the process of glioma cell invasion, we investigated the immunohistochemical localization of fibronectin (FN), laminin(LN) and FN-receptor (FN-R) in human malignant gliomas. The surgical specimens were obtained from 15 patients with malignant gliomas. Tumor tissue and adjacent brain tissue including tumor infiltration were frozen at -80 degree C immediately after the resection. Ten microns thick frozen tissue was cut out on a cryostat and divided into three different parts on the histology stained with HE, ie, the tumor region(T), brain tissues with tumor infiltration(I), and the border region between these two parts(B). These sections were air-dried, and fixed with cold acetone (-4 degrees C) for 5min. Adjacent sections were immunohistochemically stained by ABC method, using monoclonal antibody for FN-R and polyclonal antibodies for FN and LN. FN, LN and FN-R were all stained at the vascular and pial-glial basement membranes intensely in all gliomas. In immunostain for FN, fine networks of FN were observed in the extracellular space in all three parts. Some tumor cells were clustered around such networks of FN in brain tissues with tumor infiltration. Immunostain for LN demonstrated that the vascularity in the border between the tumor and the brain with tumor infiltration was much higher than that in other parts. LN was not stained in the extracellular space in all these gliomas. FN-R was expressed in some tumor cells, especially in the clustered tumor cells in the brain with tumor infiltration.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMedDate not supplied

Fibronectin modulates interleukin 6 and fibronectin synthesis of human glomerular mesangial cells in culture.

In this paper we report that fibronectin (FN) and its proteolytic 120-kD fragment regulate synthesis and secretion of interleukin 6 (IL-6) and of FN by human glomerular mesangial cells. While intact FN and a fragment derived from the heparin-binding domain had no effect on IL-6 secretion, the 120-kD FN fragment containing the cell attachment site stimulated secretion by 40-fold. The same FN fragment reduced FN secretion and the steady state mRNA level by 80%. The intact FN showed only a weak inhibitory effect (+/- 30%); the 30-kD fragment containing the heparin-binding domain had no effect. The effects of the 120-kD FN were inhibited by the peptide RGDS, implying participation of the cell attachment site in signal transduction. An antibody to the alpha-chain of VLA-3 mimicked the effect of the 120-kD FN, whereas an antibody to the alpha-chain of VLA-5 was partly inhibitory. Taken together, the data suggest that FN by interacting with its receptors differentially regulates the protein synthesis of glomerular mesangial cells, promoting IL-6 secretion and inhibiting FN synthesis.

Antibodies↗
PubMed1998

Circulating cellular fibronectin may be a natural ligand for the hepatic asialoglycoprotein receptor: possible pathway for fibronectin deposition and turnover in the rat liver.

It has been postulated that the in vivo removal of many plasma glycoproteins after desialylation is mediated by their interaction with a specific endocytic receptor on hepatocytes called the asialoglycoprotein receptor (ASGP-R), which is known to have a high affinity for specific carbohydrate residues, such as galactose. However, this mechanism has never been proven in vivo, nor has a naturally occurring ligand for the ASGP-R been identified. We investigated the influence of the terminal galactose residues on plasma fibronectin (pFn) on its liver deposition and turnover in adult rats, using neuraminidase to remove sialic acid residues to expose galactose residues. We also tested the hypothesis that the normal presence of a large amount of terminal galactose residues in cellular Fn (cFn) may allow cFn to serve as a natural ligand readily able to interact with the ASGP-R. In contrast to the slow clearance of normal pFn from the blood, cFn and desialylated pFn (aFn) displayed a rapid plasma clearance (P < .001) with greater than 50% of both the 125I-cFn or 125I-aFn depositing in the liver within 15 minutes. The enhanced plasma removal and liver deposition of both 125I-cFn and 125I-aFn was competitively inhibited (P < .01) by prior intravenous infusion of excess asialofetuin, which can selectively bind to the ASGP-R. The enzymatic addition of terminal sialic acid residues onto cFn to "mask" or "cap" the normally exposed galactose residues delayed the rapid plasma removal of cFn. Accelerated degradation of 125I-aFn and 125I-cFn as compared with 125I-pFn was demonstrated in vitro by both primary cultures of normal rat hepatocytes or incubated (37 degrees C) tissue slices of livers harvested from normal rats after in vivo preloading with tracer 125I-Fn forms. Thus, the ASGP-R appears to directly participate in the rapid in vivo removal of cFn from the blood, while native pFn may be removed by an alternative pathway unless it can become desialylated in vivo. These findings suggest that cFn may be a naturally occurring ligand that does not require desialylation before removal by the ASGP-R on hepatocytes.

Animals↗
PubMed1993

Studies on fibronectin and its domains. I. Novel recombinant cell-binding domain of fibronectin--a modulator of human platelet functions.

The DNA sequences encoding for two proteins of the cell-binding domain (CBD) of human fibronectin (FN), namely a 33-kDa protein (aa 1329-1722) and a 40-kDa (aa 1380-1851) protein, were cloned and expressed in Escherichia coli. The interactions of the resulting rCBD proteins, refolded and purified to homogeneity, with human platelets were studied in comparison with those of the pentapeptide GRGDS. The binding of both the 33-kDa and the 40-kDa proteins to washed platelets appeared to be dependent upon platelet activation. In the case of the 33-kDa protein, binding to stimulated platelets was shown to be saturable, with Kd = 2 microM (thrombin as agonist). Moreover, both the 33-kDa and the 40-kDa proteins inhibited fibrinogen binding (at 0.1 microM) to ADP- or thrombin-stimulated platelets with IC50 values in the same concentration range. Binding seemed therefore to occur mainly at the GPIIb/IIIa receptor, and accordingly monoclonal antibodies against this receptor prevented up to 85% of the binding of the 33-kDa protein to platelets. With most stimuli the 33-kDa and the 40-kDa proteins inhibited platelet aggregation at concentrations 15- to 25-fold lower than those required by GRGDS and, in the case of the 33-kDa protein, this was shown to occur in either platelet-rich plasma, washed platelets, or whole blood. The 33-kDa protein also inhibited platelet aggregation and thromboxane A2 (TXA2) generation on the subendothelial extracellular matrix, whereas the GRGDS peptide inhibited only matrix-induced platelet aggregation, but not TXA2 formation. Furthermore, the 33-kDa protein, which is derived from the human FN CBD, seemed to be highly selective, since it inhibited the aggregation of platelets from primates only, and not from other animals tested. Finally, the 33-kDa protein did not promote fibroblast cell attachment, as was observed for both whole FN and the 40-kDa protein, thus displaying a selectivity toward platelets. In conclusion, the unique properties of the 33-kDa protein, and, in particular, its special affinity directed only toward activated primate platelets, seem to hold a promising potential for the further development of an antithrombotic agent.

3T3 Cells↗
PubMed1993

Studies on fibronectin and its domains. II. Secondary structure and spatial configuration of fibronectin and of its domains.

Fibronectin (FN) from human plasma, as well as recombinant proteins derived from two of its major domains, the N-terminal fibrin-binding domain (FBD) and the cell-binding domain (CBD), were studied by circular dichroism (CD), Fourier transform infrared (FTIR), and fluorescence spectroscopies. Secondary structure estimations derived from both FTIR spectra and far uv CD indicate significant differences between FBD and CBD proteins. Thus, the CBD 33-kDa protein contains 80% beta-sheet and 20% beta-turns, whereas the three refolded FBD recombinant proteins studied, the 12-, 18.5-, and r31-kDa proteins, as well as the plasma-derived p31-kDa protein, all contain some percentage of aperiodic structure, ranging from 14 to 23% for both 31-kDa proteins, and between 33 and 46% for the smaller 12- and 18.5-kDa proteins. The amount of aperiodic structure increases drastically (from 23 to 67%) in a misfolded recombinant 31 kDa, the scrambled 31 kDa. Both native FN and a chimeric 45-kDa protein, consisting of both the FBD 12-kDa and the CBD 33-kDa proteins, were found to resemble the CBD 33-kDa protein itself, i.e., consisting only of beta-sheet and beta-turns and being free of aperiodic structure. These differences between two types of conformation are corroborated by the differences in the environment and spatial configuration of the aromatic amino acids of these proteins, as evidenced from near uv CD and intrinsic fluorescence spectroscopies. Thus, in the near uv CD the typical CBD proteins, i.e., the 33- and 45-kDa proteins display a maximum at 294 nm, whereas the FBD proteins, except for the scrambled 31-kDa protein, all have a characteristic strong negative peak at 300 nm. Similarly, the lambda max of the emission spectra of the whole FN and the 33- and 45-kDa proteins are characteristically blue-shifted (317-326 nm) and with high normalized intensity, when compared with the relatively red-shifted lambda max (338-340 nm) and low intensities of the folded FBD proteins. The scrambled 31-kDa protein again takes exception, having a relatively high normalized intensity due to misfolding. The two major conclusions from this work, attained by a combination of four spectroscopic methods, are: (a) functionally different FN domains, i.e., the FBD and CBD adopt totally different conformations, with the CBD having an almost exclusive beta structure; (b) the functional specificity of the various domains of FN may depend on subtle differences in the flexibility in their protein backbones, with the FBD being more flexible than the CBD.

Circular Dichroism↗
PubMed1999

Hepatocyte growth Factor/Scatter factor (HGF/SF) is a regulator of fibronectin splicing in MDCK cells: comparison between the effects of HGF/SF and TGF-beta1 on fibronectin splicing at the EDA region.

EDA-containing fibronectin (EDA + FN) is selectively produced under several physiological and pathological conditions requiring tissue remodeling, where cells actively proliferate and migrate. Only a few growth factors, such as transforming growth factor (TGF)-beta1, have been reported to regulate FN splicing at the EDA region. In the present study, we showed for the first time that hepatocyte growth factor/scatter factor (HGF/SF), which is mainly produced by mesenchymal cells and functions as a motogenic and mitogenic factor for epithelial cells, modulates FN splicing at the EDA region in MDCK epithelial cells. HGF/SF treatment increased the ratio of EDA + FN mRNA to mRNA of FN that lacks EDA (EDA - FN) (EDA+/EDA- ratio) more than TGF-beta1 treatment did: at a range from 0.02 to 20 ng/ml, HGF/SF increased the ratio in a dose-dependent manner by up to 2. 1-fold compared with nontreated control, while TGF-beta1 stimulated the EDA+/EDA- ratio by 1.5-fold at the optimum dose of 10 ng/ml. However, TGF-beta1 increased total FN mRNA levels by 3-fold at 10 ng/ml, but HGF/SF did not. We previously demonstrated that fibroblasts cultured at low cell density expressed more EDA + FN than those at high cell density. The same effect of cell density was also observed in MDCK cells. Furthermore, at low cell density, HGF/SF stimulated EDA inclusion into FN mRNA more effectively than did TGF-beta1, whereas at high cell density, TGF-beta1 was more potent than HGF/SF. Simultaneous treatment of cells with HGF/SF and TGF-beta1 synergistically stimulated EDA inclusion into FN mRNA. This stimulation of EDA inclusion into FN mRNA by HGF/SF led to increased EDA + FN protein production and secretion by cells, which was demonstrated by immunoblotting. Thus, our studies have shown that HGF/SF is an enhancer of EDA inclusion into FN mRNA as is TGF-beta1. However, these two factors were different in their effects at low and high cell densities and also in their effects on total FN mRNA levels.

Animals↗
PubMed2001

Regulation of fibronectin expression and splicing in migrating epithelial cells: migrating MDCK cells produce a lesser amount of, but more active, fibronectin.

Previously we have demonstrated that in MDCK epithelial cells not only transforming growth factor-beta (TGF-beta) but also hepatocyte growth factor/scatter factor (HGF/SF) regulates fibronectin (FN) splicing by increasing the ratio of EDA-containing FN (EDA+ FN) mRNA to EDA-minus FN (EDA- FN) mRNA (EDA+/EDA- ratio). EDA+ FN is known to be upregulated in tissues where cells actively migrate, such as those during morphogenesis, wound healing, and tumorigenesis. However, a direct association between cell migration and FN splicing at the EDA region has never been investigated. In this work, we have shown by using an in vitro wound migration assay that migrating epithelial cells regulate FN production and splicing differently compared to nonmigrating cells. Wounds were introduced as migration stimuli into the 10-day-old confluent cell sheet, where the EDA+/EDA- ratio and FN mRNA expression levels were stable. In migrating cells at the wound edge, the FN mRNA level decreased by 0.73-fold and the EDA+/EDA- ratio increased by 1.32-fold when compared with nonmigrating cells apart from the wound edge. HGF/SF significantly stimulated cell migration at the wound edge and concomitantly decreased the FN mRNA level by 0.60-fold and increased the EDA+/EDA- ratio by 1.84-fold in migrating cells. In nonmigrating cells apart from the wound edge, FN mRNA expression and splicing were not influenced by either wound stimulation or HGF/SF. EDA+ FN stimulates cell migration more effectively than EDA- FN and thus is considered to be a more active variant of FN. Taken together, migrating MDCK cells appear to regulate FN mRNA expression and splicing to produce a lesser amount of, but more active, FN.

Animals↗
PubMed1995

Adhesion activity in fibronectin's alternatively spliced domain EDa (EIIIA): complementarity to plasma fibronectin functions.

The EDa (EIIIA) domain is one of two alternatively spliced type III homology repeats in fibronectins which differentiate cellular (cFN) from plasma isoforms (pFN). A bacteria-expressed recombinant polypeptide encoding the EDa type III repeat promotes adhesion of some cell types and its activity is synergistic with neighboring repeats III11 and III12. We show in this study that co-coating substrata with the EDa-only polypeptide and a suboptimal concentration of pFN leads to increased attachment and extensive spreading of v-src-transformed 3T3 cells relative to that found on substrata of suboptimal pFN or EDa polypeptide alone. This complementarity of activities requires as little as 1 microgram/ml EDa polypeptide in the adsorbing mixture and displays sequence specificity for only EDa (recombinant polypeptides of neighboring repeats III11 or III12 were without effect). Furthermore, stress fibers and focal contacts are inducible on the EDa:pFN mixture, suggesting that the EDa sequence and its receptor participate in signal transduction. The codistribution of phosphotyrosine proteins, including pp125FAK, along with vinculin and talin into focal contacts supports this hypothesis. Therefore, an alternatively spliced domain EDa which is expressed in various proportions in cells and tissues may have special functions related to adhesion processes by complementing the functions of pFN circulating in blood.

3T3 Cells↗
PubMed1983

Fibronectin in early amphibian embryos. Migrating mesodermal cells contact fibronectin established prior to gastrulation.

The three-dimensional organisation of fibronectin (FN) in early amphibian embryos (Ambystoma mexicanum, Pleurodeles waltlii) was studied with the use of antibodies against amphibian-FN. Immunofluorescence labelling was performed on whole-mount specimens. It was shown that before gastrulation an extensive extracellular network consisting of anastomosed FN-fibrils underlies the roof of the blastocoel prior to the migration of mesodermal cells. Initially, FN-fibrils develop radially on the inner surface of ectodermal cells (early blastula stage) and become confluent there to elaborate a fibrillar network. During the late blastula stage the entire surface of the blastocoel roof (presumptive ectoderm and mesoderm) is covered by the FN-rich extracellular matrix. As gastrulation proceeds, the migrating mesodermal cells interact with the FN-fibrillar network. The results suggest that the FN-containing extracellular matrix plays an important role in mediating mesodermal cell-substratum contacts in gastrulating embryos. No FN-fibrils were found in other parts of the embryo.

Ambystoma↗
PubMed2004

Fibronectin fragments elevate nitric oxide (NO) and inducible NO synthetase (iNOS) levels in bovine cartilage and iNOS inhibitors block fibronectin fragment mediated damage and promote repair.

OBJECTIVE AND DESIGN: To determine whether fibronectin fragments (Fn-f) upregulate nitric oxide (NO) and inducible NO synthetase (iNOS) levels in explants and whether iNOS inhibitors block Fn-f mediated cartilage damage or promote repair. MATERIAL: Bovine cartilage explants were studied. TREATMENT: Explants were cultured with Fn-f and involvement of NO pathway investigated. METHODS: Induction of iNOS was tested by RT-PCR. Upregulation of iNOS protein was visualized by Western blotting. Proteoglycan (PG) content of cartilage treated with iNOS inhibitors was tested by dye binding assays of cartilage digests. RESULTS: Fn-fs elevated NO release in explants and upregulated iNOS protein and mRNA while native Fn had only weak activity. Three different iNOS inhibitors blocked Fn-f mediated PG depletion from explants and facilitated restoration of PG in pre-damaged cartilage. CONCLUSIONS: The Fn-f cartilage damaging pathway involves upregulation of iNOS. Interestingly, iNOS inhibitors not only blocked damage but repaired damaged cartilage. This may be the first report of reparative activities of iNOS inhibitors.

Animals↗
PubMed2003

Expression of fibronectin splice variants and oncofetal glycosylated fibronectin in the synovial membranes of patients with rheumatoid arthritis and osteoarthritis.

OBJECTIVE: The aim of this study was to define and compare the expression of fibronectin (Fn) isoforms in synovial tissue of patients with rheumatoid arthritis (RA) and osteoarthritis (OA). METHODS: Using monoclonal antibodies specific for total Fn, extra domain (ED)-A Fn, ED-B Fn, and oncofetal glycosylated Fn, we studied the expression of the Fn isoforms in synovium. Furthermore, in situ hybridization for the detection of ED-B Fn mRNA including a double labeling technique for the detection of cell type was applied. RESULTS: Strong expression of total Fn, ED-A Fn, oncofetal glycosylated Fn and, to a lesser extent, ED-B Fn could be demonstrated in the synovial lining layer in both RA and OA. Stromal and vessel expression of Fn isoforms was more prominent in RA tissue. Pannus tissue showed strong labeling with ED-B Fn. CONCLUSION: The expression of alternatively spliced isoforms of Fn is associated with tissue remodeling and, as a partial process of this phenomenon, with neovascularization rather than underlying disease, X-ray status, or parameters of acute inflammation. In the lining layer, Fn expression correlates with hyperplasia associated with cell recruitment but not with proliferative status. Most remarkably, the expression of ED-B Fn in pannus tissue seems to be associated with the invasive phenotype described in RA tissue.

Alternative Splicing↗
PubMed2006

Importance of the heparin-binding domain of fibronectin for enhancing cell adhesion activity of the recombinant fibronectin.

We have previously shown that the recombinant human fibronectin (FN) fragment composed of central cell binding domains (CCBD) spanning the ninth and tenth type III domains promotes cell adhesion and proliferation of osteoblasts. In the present study, we investigated the biological potency of heparin-binding domain (HBD) of FN spanning the twelfth and fourteenth type III domains. The HBD of FN significantly enhances the RGD-containing CCBD-mediated cell adhesion and proliferation in HOS cells (P < 0.05).

Binding Sites↗
PubMedDate not supplied

Differential effects of cellular fibronectin and plasma fibronectin on ovarian cancer cell adhesion, migration, and invasion.

The main form of fibronectin (FN) encountered by tumor cells in vivo is cellular FN (cFN), which differs structurally and functionally from the commonly used plasma FN (pFN). We compared the effects of cFN and pFN on the ovarian carcinoma lines OVCAR-3 and SKOV-3 and on cultures of normal ovarian surface epithelium, which is the precursor of the epithelial ovarian carcinomas. Ovarian surface epithelial cells and SKOV-3 cells attached and spread faster on cFN than on pFN. On cFN, SKOV-3 migration was enhanced compared with pFN or plastic. In a matrigel transfilter assay, cFN strongly inhibited SKOV-3 invasion, whereas pFN did not. In contrast to SKOV-3, OVCAR-3 cells adhered faster on FN than on plastic but did not discriminate between cFN and pFN, and they did not migrate or invade matrigel either with or without FN. In both carcinoma lines, proliferation was unaffected by either FN. The results show profound differences in the responses to cFN and pFN by two invasive ovarian carcinoma lines. Because cFN is the main type that cancer cells encounter in vivo, extrapolations from culture data to in vivo events should preferably be based on studies using this form of FN.

Cell Adhesion↗
PubMed1991

Collagen gel contraction by fibroblasts requires cellular fibronectin but not plasma fibronectin.

Fibroblasts embedded in three-dimensional lattices of collagen fibrils have been known to require serum constituents to induce a cell-mediated contraction of collagen gels. The gel contraction was studied with human skin fibroblasts cultured in the presence of fetal bovine serum (FBS). Removal of bovine serum fibronectin (sFN) from FBS did not affect the extent of gel contraction. Gel contraction occurred in serum-free defined media. Therefore, it is concluded that sFN is not required for gel contraction. That cellular FN (cFN) synthesized and secreted by fibroblasts plays a crucial role in gel contraction was suggested by the following experiments: (1) We obtained monoclonal antibodies (mAb A3A5) against fibroblast surface antigens, which suppressed the fibroblast-mediated gel contraction. Immunoblot analyses showed that mAb A3A5 recognizes cFN secreted by human fibroblasts and human plasma FN (pFN), but not bovine sFN in FBS used for culture. (2) Addition of rabbit antisera, which recognize human cFN, to a serum-free gel culture inhibited contraction. Uninvolvement of human pFN in gel contraction was further confirmed by the fact that neither pretreatment of fibroblasts with excess amounts of human pFN nor the presence of excess amounts of human pFN in gels affected the extent of gel contraction. This study seems to be the first demonstration of functional difference between cFN and pFN (or sFN) and proposes a novel mode of binding of fibroblasts with collagen fibrils via cFN during cell-mediated collagen morphogenesis.

Antibodies, Monoclonal↗
PubMed1991

Augmentation of macrophage recognition of oxidatively damaged erythrocytes by substratum-bound fibronectin and macrophage surface fibronectin.

Thioglycollate-induced mouse peritoneal macrophages plated on a coverglass bind oxidized mouse erythrocytes in the absence of serum. Macrophages plated on a coverglass pre-coated with fibronectin (FN) were more active in binding of the oxidized erythrocytes. This effect of FN-coated coverglass was due to specific binding of an RGD-containing sequence of FN to FN-receptors on the macrophage, since GRGDSP hexapeptide in solution inhibited this effect, and GRGDSP-coated coverglass exhibited the same effect as FN-coated coverglass. Removal of FN originally present on the macrophage surface by trypsinization, prior to attachment to the coverglass, resulted in diminution of their ability of recognition of the oxidized erythrocytes, but the diminished ability was restored when the trypsinized macrophages were plated on a FN-coated coverglass, indicating that the cell surface FN is required for the macrophage recognition. Attachment to the coverglass was necessary for the cell surface FN to be effective. These results suggest that solid-phase FN, produced either by deposition of soluble FN to substratum or attachment of macrophage surface FN to substratum, activates the macrophages and augments their ability to recognize the oxidized erythrocytes.

Amino Acid Sequence↗
PubMed2006

Molecular basis for the presence of glycosylated onco-foetal fibronectin in oral carcinomas: the production of glycosylated onco-foetal fibronectin by carcinoma cells.

Glycosylated onco-foetal fibronectin (GOF) deposited in the stroma of oral squamous cell carcinomas correlates with survival. One of the two polypeptide GalNAc-transferases, GalNAc-T3 or GalNAc-T6, is required for the biosynthesis of GOF by the initiation of a unique O-glycan in the alternative spliced IIICS region. Using cell culture experiments, immunohistochemical staining of primary tissue, and RT-PCR of tumour cells isolated by laser capture techniques we have examined the molecular basis for the production of GOF in oral carcinomas. Immuno-histochemical investigation confirmed the stromal deposition of GOF in oral carcinomas. However, neither GalNAc-T3 nor GalNAc-T6 could be detected in stromal fibroblasts. In contrast both transferases were present in the oral squamous carcinoma cells, suggesting that GOF is produced by the oral cancer cells and not only the stromal cells. RT-PCR analysis of RNA isolated from carcinoma cells provided further support for this conclusion by demonstrating in-splicing of the alternative spliced IIICS domain in GOF.

Actins↗