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PubMed2006

Association study between fibronectin and coronary heart disease.

Fibronectin is a known chemoattractant for several cell types that play a role in the wound healing process, including fibroblasts, endothelial cells and macrophages. It also generates a scaffold that allows attachment of other extracellular matrix components. Large amounts of fibronectin have been detected in atherosclerotic plaques, suggesting that it may play a role in the pathogenesis of atherosclerosis. To examine the possible involvement of fibronectin in the etiology of atherosclerotic coronary heart disease, we analyzed four polymorphisms in the human fibronectin gene and determined the plasma fibronectin levels in patients with coronary heart disease (n = 109) and age- and gender-matched controls (n = 123) in Chinese Han people. No significant positive association was observed between these polymorphisms and coronary heart disease. The levels of circulating plasma fibronectin, however, were significantly lower in patients with coronary heart disease (mean +/- SD 245 +/- 87 mg/L) compared with controls (354 +/- 88 mg/L) (p < 0.001). The odds ratio (OR) for plasma fibronectin was 0.94 in a multivariate unconditional logistic regression model (OR = 0.94, 95% CI 0.91-0.96, p < 0.001). We conclude that, in our population, the four fibronectin gene polymorphisms detected are not associated with clinical coronary heart disease. Our data suggest that low circulating fibronectin levels might be a new marker of coronary heart disease.

Alleles↗
PubMed1994

Progesterone stimulates fibronectin production by chicken granulosa cells in vitro.

Experiments were conducted in vitro to examine the effect of progesterone on fibronectin production by chicken ovarian granulosa cells. Granulosa cells isolated from the largest (F1; mature) and third-largest (F3; developing) preovulatory follicles as well as form a pool of immature small yellow follicles (SYF) of the domestic chicken ovary were incubated in serum-free Medium-199 and the amounts of fibronectin and progesterone produced were quantified by enzyme-linked immunosorbent assay and radioimmunoassay respectively. The amounts of basal fibronectin and progesterone produced by granulosa cells from F1, F3 and SYF follicles increased with advancing stages of follicular development. Thus, the quantity of basal fibronectin secreted by granulosa cells was directly proportional to the amount of progesterone produced by them. Exogenously supplied progesterone increased the amount of fibronectin secreted by F1 and F3 cells in a dose-dependent manner, but its effect on SYF cells was marginal. Cyanoketone (an inhibitor of progesterone synthesis) suppressed basal fibronectin production by F1 and F3 granulosa cells and its inhibitory action was reversed by exogenous progesterone. The progesterone antagonist RU 486 also attenuated basal fibronectin production by F1 and F3 granulosa cells, but only the highest concentration affected SYF cells. The inhibitory effect of RU 486 was diminished in the presence of exogenous progesterone. These data show that progesterone regulates fibronectin production by chicken granulosa cells. They suggest that in avian granulosa cells, endogenous progesterone can stimulate fibronectin synthesis in an intracrine or autocrine manner.

Animals↗
PubMed1999

Detection of fetal fibronectin in twin pregnancies in relation to gestational age.

CONTEXT: The presence of fetal fibronectin in the cervix or vagina has been investigated as a possible marker for the risk of preterm birth. Fetal fibronectin in cervical fluid can provide direct evidence of pathologic changes at the interface of fetal and maternal tissues. OBJECTIVE: To evaluate the presence of fetal fibronectin as a predictor of premature delivery in twin pregnancies in relation to gestational age. DESIGN: Accuracy study. SETTING: University referral unit. PARTICIPANTS: 52 pregnant women with twin pregnancies and gestational age of between 24 and 34 weeks. MAIN MEASUREMENTS: Sensitivity, specificity, predictive values and relative risk ratios of the correlation between fetal fibronectin and preterm birth before 34 and 37 weeks using an immediate-reading membrane test on cervicovaginal secretions obtained from participants. RESULT: The sensitivity varied between 66.7% and 85.7%, whereas the specificity was from 58.3% to 81.8% according to gestational age at the time of sampling. The relative risk of spontaneous preterm birth after a positive fetal fibronectin test, as compared with a negative fetal fibronectin test, rose from 2.8 at 24-26 weeks to 4.1 at 27-30 weeks. Analyses of the risk of delivery before 34 weeks were not statistically significant. CONCLUSION: Fetal fibronectin in the cervicovaginal secretions of patients with twin pregnancies is a useful tool for the early identification of twin pregnancies likely to deliver before 37 weeks. However, the clinical value of the fibronectin test is limited because of low indices for prediction of delivery before 34 weeks. The best period for performing the fetal fibronectin test in twin pregnancies to predict preterm delivery is between 27 and 30 weeks.

Biomarkers↗
PubMed1995

Fibronectin mRNA in the developing glomerular crescent in rabbit antiglomerular basement membrane disease.

Fibronectin is a multifunctional matrix protein important in wound healing that is markedly increased in glomerular crescents. A previous report established two phases of fibronectin metabolism in crescent formation in an anti-glomerular basement membrane model of crescentic nephritis in the rabbit. Phase I was associated with increased glomerular fibronectin content from plasma. Phase II was associated with increased fibronectin mRNA in glomeruli. To examine the hypothesis that fibronectin is synthesized in the developing crescent, rabbit fibronectin cDNA was cloned, sense and antisense riboprobes were prepared and their specificity under the conditions to be used was validated and in situ hybridization studies were performed in the model. The results showed that the cells in the developing glomerular crescent express an intense fibronectin mRNA signal at Day 7 and that this signal persisted in cells of the crescent at Day 14. This result shows that fibronectin synthesis does indeed take place in cells of the developing crescent in this model and supports the hypothesis that fibronectin may be an important agent regulating crescent formation and fibrosis.

Amino Acid Sequence↗
PubMed1986

Localization of fibronectin in gingival connective tissue of the beagle dog. Ultrastructural detection with ferritin and peroxidase-conjugated antibodies.

Ferritin and peroxidase-conjugated antibodies were used in an indirect antibody method to localize fibronectin in gingival connective tissues. Fibronectin was found in the basal lamina beneath the epithelium and endothelium. Collagen fibrils associated with the basement membranes were also heavily coated by fibronectin. Amorphous patches of fibronectin were found adjacent to the plasma membrane of epithelial cells as well as free in the interepithelial spaces. Fibronectin was present throughout the connective tissue in close association with individual collagen fibrils, apparently serving as an interfibrillar cementing substance. Patches of fibronectin were located at the cell surface of fibroblasts, plasma cells, lymphocytes, endothelial cells, smooth muscle cells, and neutrophils. These amorphous patches were observed to connect adjacent cells across narrow spaces and to connect cells to collagen fibrils. The heavy labeling for fibronectin visualized by fluorescent microscopy around gingival blood vessels (Cho et al., 1985) can be accounted for by a heavy coating of fibronectin on the collagen fibrils and basal laminas associated with endothelial cells, as well as by the presence of abundant deposits of fibronectin along the cell membranes of endothelial cells and in the intercellular spaces of the vessel wall.

Animals↗
PubMed1990

Sorption of fibronectin to human root surfaces in vitro.

The purpose of this study was to determine the conditions that favor the sorption and retention of human plasma fibronectin to cementum. Rectangular root segments prepared from teeth extracted for orthodontic reasons were mounted on a capillary pipette and immersed in solutions of 125I fibronectin for assay of cementum sorption under various conditions. Kinetic studies showed sorption to be rapid, with 77% of the maximum fibronectin sorption occurring within 1 minute. Fibronectin sorption was reduced when added in conjunction with serum and was inhibited by monovalent ions (such as sodium), but enhanced in the presence of divalent cations (such as calcium). Exposure of cementum to serum partially blocked subsequent sorption of fibronectin, while cementum bound fibronectin was eluted by subsequent exposure to serum. Treatment of cementum with citric acid pH 1.1 (4 minutes) followed by 5% sodium hypochlorite (5 minutes) caused a significant increase in fibronectin sorption with maximum retention upon subsequent exposure to serum (P less than 0.05). Fibronectin sorption to cementum was: rapid, electrostatic in nature, competitive, reversible, Ca+(+)-facilitated, and maximized by prior treatment of the root with citric acid and sodium hypochlorite. It is concluded that sorption of fibronectin to cementum can be achieved for clinical gain; however, conditions of application can significantly influence both accumulation and subsequent release of root sorbed material.

Absorption↗
PubMed1981

Binding of fibronectin to Clq; inhibition of binding by aggregated IgG.

Fibronectin was shown to bind to C1q using alkaline phosphatase conjugated fibronectin and C1q coated polystyrene tubes. The binding of the alkaline phosphatase conjugated fibronectin to C1q was dose dependent and inhibited by fibronectin and by the sulfated polymers heparin and chondroitin sulfate. The fibronectin interaction was inhibited only slightly by gelatin indicating that the fibronectin-gelatin interaction was different from that with C1q. Heat aggregated IgG blocked the binding of fibronectin to C1q and fibronectin inhibited the binding of aggregated IgG to C1q. These results suggest that fibronectin may be a factor affecting the determination of immune complexes in serum specimens by C1q binding assays.

Alkaline Phosphatase↗
PubMed1993

Fibronectin synthesis by aorta explants from rabbits fed high cholesterol diets.

Fibronectin synthesis was studied in aorta explants in culture from rabbits fed a high fat-high cholesterol diet. [3H]Mannose and [14C]leucine were used to label oligosaccharide side chains and the protein core, respectively. The synthesis was followed by monitoring immunoprecipitable fibronectin from the culture medium using polyclonal goat anti-rabbit fibronectin antibody. Synthesis of fibronectin increased by [14C]leucine (81%) and [3H]mannose (29%) incorporation over controls. On gel filtration, fibronectin synthesized by controls and cholesterol-fed rabbit resolved into four fractions. Pulse-chase experiment with [3H]glucosamine or [3H]leucine showed that fibronectin secreted by the aorta explants from rabbits fed high fat-high cholesterol diets incorporated an increased amount of radioactivity. Pulsing with [3H]mannose showed decreased incorporation of the label. During the chase period, the rate of secretion of fibronectin into the media by the hypercholesterolemic rabbit aorta explants was increased. The fibronectin that bound to the gelatin or heparin columns from cholesterol-fed rabbit aorta media had lower levels of [3H]mannose incorporated into the glycoprotein than the control. These results indicate that there is an alteration in carbohydrate composition of the fibronectin synthesized by the aorta explants from rabbits fed a high cholesterol diet. High fat-cholesterol intake could play a causative role in matrix dysfunction during atherogenesis by altering glycoprotein synthesis.

Animals↗
PubMed2002

Triglycerides predict plasma fibronectin in children with type I diabetes mellitus rather than diabetes.

Fibronectins are adhesive proteins considered as markers of endothelial activation. Plasma fibronectin levels in diabetes mellitus (DM) have been found to be associated with atherosclerotic risk factors. This study was carried out to investigate plasma fibronectin and its relation with serum lipids, apolipoproteins AI, B100 and lp(a) in diabetic children. 35 children (19F/16M) with type I DM and 30 non-diabetic age and gender-matched controls were enrolled. Apolipoprotein and fibronectin concentrations were determined with nephelometric methods. Plasma fibronectin levels of the children with type I DM and the control group are not statistically different. HbA1c and triglycerides concentration are found to be significant predictors of plasma fibronectin in diabetic children, while effect of plasma cholesterol, apolipoprotein AI, B100 and lp(a) are insignificant. Diabetic children with triglycerides 1.13 mmol/l have elevated plasma fibronectin (median, 25th-75th percentiles; 29.6, 8.3-40.8 mg/dL) compared to the diabetic > or = 19.9, 8.6-30.7 mg/dL, p < 0.05) and non-diabetic children (16.6, 12.7-32.4 mg/dL, p < 0.01) with triglycerides < 1.13 mmol/L. On the other hand plasma fibronectin concentrations of diabetic and non-diabetic children with high triglycerides are not significantly different. In conclusion our data does not support the concept that plasma fibronectin is elevated in type I diabetes mellitus at least in children, but high plasma triglycerides secondary to diabetes or not is associated with higher FNp concentrations which may have implications on atherogenesis. Plasma cholesterol, apolipoproteins AI, B100 and lp(a) are not significant determinants of FNp in type I diabetic children.

Child↗
PubMed1992

Fibronectin in HIV-infected patients: a prospective study.

Fibronectin, a non-specific opsonin involved in the clearance of microorganisms, is thought to play a role in various infectious disease processes. Its diagnostic value as a biological marker of infection and/or prognosis in human immunodeficiency virus (HIV) patients is questionable. We conducted a prospective study to evaluate plasma fibronectin levels in patients with HIV infection at different stages of the disease. Eighty-one consecutive HIV-infected patients seen in our department were evaluated clinically and biologically. Classifications according to the Centers for Disease Control (CDC) stages were: Group II (n = 22), Group III (n = 17), acquired immunodeficiency syndrome (AIDS) (n = 17) and AIDS related complex (n = 25). Plasma fibronectin levels were measured by a radial immunodiffusion assay. Plasma fibronectin levels were not different between HIV-infected patients (344 +/- 128 mg/L) and controls (n = 20, 335 +/- 45 mg/L). Among the 81 patients, plasma fibronectin levels were within normal value in 79%, with no significant difference of mean plasma fibronectin between the different CDC groups. No correlation was found between plasma fibronectin and other biological parameters including CD4+ cells, p24 antigen, beta-2-microglobulin. Furthermore, no correlation was noted between fibronectin and complement levels or presence of circulating immune complexes. These results suggest that plasma fibronectin is not a useful marker in patients with HIV infection.

AIDS-Related Complex↗
PubMed1992

Visualization of purified fibronectin-transglutaminase complexes.

It has been reported previously (Turner, P.M., and Lorand, L. (1989) Biochemistry 28, 628-635) that human erythrocyte transglutaminase forms a noncovalent complex with human plasma fibronectin near its collagen-binding domain. In the present study, we show by nondenaturing electrophoresis that guinea pig liver transglutaminase, similarly to the erythrocyte enzyme, forms a complex with human fibronectin. Studies of anisotropic shifts of fluorescein-labeled liver and erythrocyte transglutaminases, upon addition of fibronectin, indicated that both transglutaminases bind to fibronectin with a stoichiometry of about 2:1. Polymerization of fibrinogen by human erythrocyte transglutaminase was inhibited after complex formation with fibronectin. Complexes of fibronectin with either erythrocyte or liver transglutaminase were isolated by glycerol gradient zone sedimentation and examined by rotary shadowing electron microscopy. The globular transglutaminase could be readily identified binding to the thin fibronectin strand. The binding site for transglutaminase was within 5-10 nm of the N terminus of fibronectin, consistent with its proximity to the collagen-binding domain. Under some experimental conditions, the complex of fibronectin with erythrocyte transglutaminase appeared as a ring-shaped structure in which two transglutaminase molecules had probably dimerized. The molecular weight of the erythrocyte transglutaminase was determined by sedimentation equilibrium to be 71,440 +/- 830.

Animals↗
PubMed1992

Alveolar accumulation of fibronectin and hyaluronan precedes bleomycin-induced pulmonary fibrosis in the rat.

The development of bleomycin-induced pulmonary fibrosis in rats was studied over a period of 30 days after an intratracheal instillation of bleomycin. Fibronectin was visualized in histological sections and quantified in bronchoalveolar lavage fluid (BALF) and related to simultaneous measurements of hyaluronan, collagen and albumin in BALF and/or lung tissue extracts. An increase in BALF fibronectin levels was noted after 3 days and the peak value a sixty fold increase was noted at day 7. Thereafter, the fibronectin levels declined and reached control values on day 21. A pronounced, patchily distributed staining for fibronectin appeared in the injured alveolar tissue parallel to the increased lavage fluid fibronectin levels on days 3-7. A fainter, streakily distributed fibronectin staining remained within the alveolar walls in areas with proliferating fibroblasts on days 14-30. Albumin in BALF increased to a peak level, 20 times control values, after 3 days and then rapidly declined. Thus, the ratio of fibronectin to albumin increased to a peak value of 43 times control values on day 7, indicating that plasma leakage cannot be the only source of the observed increase in lavage fibronectin. Lung tissue hydroxyproline increased between days 7 and 30, whereas extractable hyaluronan in lung tissue and bronchoalveolar lavage fluid peaked on days 3-7 and then gradually declined towards normal values on days 21-30. These data demonstrate that fibronectin accumulates in the alveolar tissue during the early inflammatory phase of the bleomycin-induced lung injury, parallelling hyaluronan accumulation and preceding the development of pulmonary fibrosis.

Animals↗
PubMed1992

Effects of three antiarthritic drugs on fibronectin and keratan sulfate synthesis by cultured canine articular cartilage chondrocytes.

Because articular chondrocytes are a target for drugs that can influence the integrity of cartilage, we investigated the effects of 3 antiarthritic drugs, glycosaminoglycan polysulfate, diclofenac-Na, and S-adenosylmethionine sulfate p-toluenesulfonate on total protein, fibronectin, and DNA synthesis, as well as on extradomain-A fibronectin and keratan sulfate content. Glycosaminoglycan polysulfate stimulated dose-dependent incorporation of [35S]methionine into protein and fibronectin, whereas incorporation of [3H]thymidine into DNA was unaffected. Total fibronectin, extradomain-A fibronectin, and keratan sulfate content were high in chondrocyte cultures treated with glycosaminoglycan polysulfate. In contrast, fibronectin and DNA synthesis, as well as extradomain-A fibronectin and keratan sulfate content were unaffected by diclofenac-Na. S-Adenosyl-methionine decreased dose-dependently the synthesis of fibronectin, as well as the content of fibronectin and keratan sulfate. At the highest concentration of S-adenosyl-methionine tested, findings suggest that cell viability was impaired as assessed by the release of lactate dehydrogenase into the media.

Animals↗
PubMedDate not supplied

Fibronectin levels in chronic viral hepatitis and response of this protein to interferon therapy.

BACKGROUND/AIMS: In this study, the plasma fibronectin levels in the cases of chronic hepatitis B and C infection and this protein's response to the interferon therapy were examined. METHODOLOGY: Totally, 38 patients with chronic hepatitis, 21 of them being hepatitis B, 17 of them being hepatitis C; and 24 healthy blood donors, as the control group, took part in this study. The quantitative determinations of fibronectin in plasma samples were performed with the Bohring Nephelometer BN 100 (N Antiserum to Human Fibronectin, code no OUND, Dade Behring Marburg GmbH, Marburg Germany). RESULTS: It was observed that the fibronectin plasma levels of the control group were significantly higher than those of the patient group before the therapy (p=0.043). After the interferon therapy of six months, the difference between the fibronectin levels of 16 examined patients before and after the treatment was found to be significant (p=0.001). A negative correlation was detected between the fibronectin levels before the therapy and the inflammatory grade as far as the histopathology of the illness was concerned (r=-0.49), which is a statically significant value (p=0.002). The correlation between the levels of fibronectin and the stage of the fibrosis was found to be insignificant statistically (p=0.225). When comparing the levels before and after the therapy, as far as ALT and AST values were concerned, it was observed that both parameters fell significantly after the therapy (p=0.002). However, no correlation was observed between the fibronectin levels and ALT, AST before and after the therapy. CONCLUSIONS: Fibronectin can be a useful marker for showing the hepatic inflammation and damage in the cases of chronic hepatitis, and can also be used in the evaluation of the response to the interferon therapy like other biochemical parameters (ALT, prothrombin activity etc.).

Adult↗
PubMedDate not supplied

Sperm surface fibronectin. Expression following capacitation.

The Arg-Gly-Asp (RGD) amino acid sequence plays a role in many cell-to-cell and cell-to-matrix adhesion systems, as a recognition sequence for cell membrane receptors termed integrins. Receptors of the VLA subfamily of integrins recognize fibronectin, laminin, and collagen. Given the authors' findings that fibronectin-derived, RDG-containing peptides competitively inhibit sperm-oolemmal adhesion and penetration in both heterologous (human-hamster) and homologous (hamster-hamster) gamete interactions, the expression of fibronectin on the surface of fresh, capacitated, and acrosome-reacted human spermatozoa was studied. The majority of fresh spermatozoa did not display fibronectin on their plasma membrane (0 to 16% positive), as demonstrated by the lack of binding of both monoclonal and polyclonal anti-fibronectin antibodies. In contrast, a significantly greater proportion of spermatozoa (varying between 18% to 100% for different donors) incubated overnight under capacitating conditions reacted with anti-fibronectin antibodies. The induction of an acrosome reaction with progesterone did not alter the proportion of sperm displaying fibronectin or its distribution on the sperm surface. A physiologic role of fibronectin in sperm-oolemmal interaction was suggested by the effects of anti-fibronectin antibodies on sperm oolemmal adhesion and penetration of hamster eggs by human spermatozoa, which were both significantly reduced (P less than 0.001).

Acrosome↗
PubMed1991

The alternative splicing of fibronectin pre-mRNA is altered during aging and in response to growth factors.

The reverse transcription-polymerase chain reaction was used to examine alternative splicing at each of the three fibronectin exons known to undergo alternative splicing, i.e. extra domain A (ED-A), extra domain B (ED-B), and type III connecting sequence (IIICS). Ratios of fibronectin mRNAs with or without a given exon were determined in several rat tissues and human cell lines during aging in vivo and cellular senescence in vitro. We demonstrate that statistically significant shifts in the alternative splicing of fibronectin occur during aging in vivo and in vitro. Since all three alternatively spliced exons are spliced out at a higher frequency in aging tissues and cells, the fibronectin protein produced by old cells should be slightly smaller than that obtained from young cells. The reverse transcription-polymerase chain reaction demonstrates tissue-specific patterns of alternative splicing in several tissues. Whereas fibronectin mRNAs from adult rat tissues were found to range from 0 to 25% ED-A+ and from 0 to 10% ED-B+, fibronectin mRNAs from cultured cell lines were found to be approximately 50-60% ED-A+ and 15-25% ED-B+. We observed similarity in splicing of fibronectin RNA by the different cultured cell lines obtained from many tissues and attribute this observation to the effect of growth factors. We demonstrate that serum deprivation; placement of cells into primary culture; and growth factors such as transforming growth factor beta 1, retinoic acid, and 1,25-dihydroxyvitamin D3 can all change the alternative splicing of fibronectin pre-mRNA in the ED-A, ED-B, and type III connecting sequence exons. Possible mechanisms for the regulation of the alternative splicing of fibronectin RNA by growth factors are discussed.

Aging↗
PubMed1991

Modulation of fibronectin and proteoglycan synthesis by chondrocytes.

Synthesis of fibronectin and proteoglycan by chondrocytes in both cell and organ culture was affected by the culture conditions. Less than 2% of the fibronectin extracted from cartilage contained the ED-III-A sequence, however, chondrocytes placed in primary culture began to synthesize increased amounts of ED-III-A fibronectin (up to 36% of the total fibronectin). Expression of ED-III-A fibronectin was selectively reduced when the chondrocytes were cultured in the presence of 0.5 mM dibutyryl cyclic AMP. The amount of fibronectin in the media of DBcAMP treated cultures was reduced by 30% but there was no effect on the overall protein biosynthetic rates of the cells. Concomitant with the decrease in fibronectin was an increase in the concentration of keratan sulfate in the media of treated cultures. Treatment with 0.5 mM dibutyryl cAMP caused the cells to adopt a more rounded morphology. Proteoglycan synthesis in cartilage explants was maintained at levels comparable to those at Day 0 for up to twelve days in a medium supplemented with insulin. Fibronectin and collagen synthesis, however, declined relative to Day 0 levels in this medium. The addition of TGF-beta at 2 and 10 ng/ml to the medium not only prevented the decline in fibronectin synthesis but progressively increased its rate of synthesis until the Day 0 levels were exceeded 4-fold. Experiments were initiated to study also the effects of mechanical factors on cartilage explant metabolism.

Animals↗
PubMed1991

Cell surface molecules that bind fibronectin's matrix assembly domain.

The assembly of fibronectin into disulfide cross-linked extracellular matrices requires the interaction of mesenchymal cells with two distinct sites on fibronectin, the Arg-Gly-Asp cell adhesive site and an amino-terminal site contained within the first five type I homologous repeats (Quade, B. J., and McDonald, J. A. (1988) J. Biol. Chem. 263, 19602-19609). Proteolytically derived 29-kDa fragments of fibronectin (29kDa) containing these repeats bind to monolayers of cultured fibroblasts and inhibit fibronectin matrix assembly. The cell surface molecules interacting with fibronectin's 29-kDa matrix assembly domain have resisted purification using conventional methods such as affinity chromatography. Accordingly, in order to identify molecules which bind this fragment, 125I-labeled 29kDa was allowed to bind to fibroblast monolayers and chemically cross-linked to the cell surface with bis(sulfosuccinimidyl) suberate. Extraction of the cross-linked cell layer yielded radiolabeled complexes of 56, 150, and 280 kDa. Formation of these cross-linked complexes was specifically inhibited by the addition of excess unlabeled 29kDa but was unaffected by the presence of fibronectin fragments containing other type I repeats outside of the 29kDa matrix assembly domain. The cross-linked complexes were insoluble in nondenaturing detergents but soluble when denatured and reduced, suggesting that 29kDa may be cross-linked to components of the pericellular matrix. Immunoprecipitation of cross-linked cell extracts with a polyclonal antibody to fibronectin that does not recognize the amino terminus demonstrate that the 280-kDa band contains 29kDa cross-linked to fibronectin present on the cell surface. Formation of the 150-kDa complex was inhibited by EDTA, suggesting that divalent cations are required for its formation. Although the molecular mass and divalent cation requirement suggest that the 150-kDa complex may be related to an integrin, this complex was not immunoprecipitated by polyclonal antibodies generated to the alpha 5 beta 1 integrin fibronectin receptor.

Animals↗