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Approximately one-half of the amino acid sequence (911 amino acid residues out of 1,880 expected) for bovine plasma fibronectin (cold-insoluble globulin) has been determined. Three types of internal homology were identified, showing that a number of partial gene duplications (multiplications) have occurred during the evolution of this protein. Digestion of fibronectin with plasmin results in major fragments with molecular masses of 29, 170,23, and 6 kilodaltons (kDal). The NH2-terminal 29-kDal fragment consists of259 residues ordered as five mutually homologous domains (type I homology) with two disulfide bonds in each domain. The 170-kDal fragment shows two to three bands after NaDodSO4 gel electrophoresis, indicating heterogeneity. This fragment contains the gelatin binding site and the strong heparin binding site present in fibronectin. Digestion of the 170-kDal fragment with chymotrypsin liberates a 45-kDal fragment that also binds to gelatin. This fragment contains at least one domain oftype I homology and two domains of type II homology. Further digestion of the 170-kDal fragment with chymotrypsin results in the formation of a 30-kDal fragment that retains the heparin binding activity. This fragment contains sequences constituting type m homology. The 23-kDal fragment consists of 178 residues having three domains of type I homology. The 6-kDal fragment consists oftwo identical peptides of26 residues, and these two peptides are linked to each other by two disulfide bonds that form the interchain bridges. Another one ofthe peptides for which the sequence was determined links the COOH-terminus of the 29-kDal fragment to the NH2-terminus of the 170-kDal fragment. This and the fact that the COOH-terminal residue of the 6-kDal fragment is a glutamic acid residue order the four plasmin-digestion fragments as 29-, 170-, 23-, and 6-kDal in the intact fibronectin molecule.Fibronectin is a protein or a group of similar proteins found in blood plasma (1) and on the surface of different cell types (2) (for review, see refs. 3-5). The functions attributed to fibronectin, such as cell adhesion to substratum, cell spreading, opsonization of bacteria and other particulate matter, and wound healing, are all related to its affinity to cell surfaces. Binding to vastly different biological compounds, such as gelatin (6), glycosaminoglycans (7), DNA (8), fibrin (9), actin (10), sphingolipids (11), acetyl cholinesterase (12), amyloid P component (13), and complement factor Clq (14), has been demonstrated. Some of these binding sites have been found to be contained in specific fragments generated by limited proteolysis of fibronectin (15)(16)(17)(18)(19)(20)(21)(22)(23)(24). Recently, a transformation-enhancing activity has been shown in the gelatin binding fragments offibronectin (25).Fibronectin is a substrate for blood coagulation factor XIIIa (26) and can be covalently crosslinked to fibrin (26), collagen (21), and the surface ofStaphylococcus aureus (22) by this transglutaminase. Fibronectin used to be known as cold...

IntroductionCo-morbidity and mortality due to cardiovascular disease (CVD) are increased in patients with rheumatoid arthritis (RA). Most published studies in this field are retrospective or cross sectional. We investigated the presence of traditional and disease related risk factors for CVD at the onset of RA and during the first five years following diagnosis. We also evaluated their potential for predicting a new cardiovascular event (CVE) during the five-year follow-up period and the modulatory effect of pharmacological treatment.MethodsAll patients from the four northern-most counties of Sweden with early RA are, since December 1995, consecutively recruited at diagnosis (T0) into a large survey on the progress of the disease. Information regarding cardiovascular co-morbidity and related predictors was collected from clinical records and supplemented with questionnaires. By April 2008, 700 patients had been included of whom 442 patients had reached the five-year follow-up (T5).ResultsAmong the 442 patients who reached T5 during the follow-up period, treatment for hypertension increased from 24.5 to 37.4% (P < 0.001)), diagnosis of diabetes mellitus (DM) from 7.1 to 9.5% (P < 0.01) whilst smoking decreased from 29.8 to 22.4% (P < 0.001) and the BMI from 26.3 to 25.8 (P < 0.05), respectively. By T5, 48 patients had suffered a new CVE of which 12 were fatal. A total of 23 patients died during the follow-up period. Age at disease onset, male sex, a previous CVE, DM, treatment for hypertension, triglyceride level, cumulative disease activity (area under the curve (AUC) disease activity score (DAS28)), extra-articular disease, corticosteroid use, shorter duration of treatment with disease modifying anti-rheumatic drugs (DMARDs) and use of COX-2 inhibitors increased the hazard rate for a new CVE. A raised erythrocyte sedimentation rate (ESR) at inclusion and AUC DAS28 at six months increased the hazard rate of CVE independently whilst DMARD treatment was protective in multiple Cox extended models adjusted for sex and CV risk factors. The risk of a CVE due to inflammation was potentiated by traditional CV risk factors.ConclusionsThe occurrence of new CV events in very early RA was explained by traditional CV risk factors and was potentiated by high disease activity. Treatment with DMARDs decreased the risk. The results may have implications for cardio-protective strategies in RA.

The primary structure of the 2265 residues of bovine plasma fibronectin has been completed. The new sequences reported in this paper are residues 600-868 (269 residues), 1138-1217 (80 residues), 1518-1599 (82 residues) and 1868-2061 (194 residues). These sequences constitute six type I11 homology units and two nonhomologous connecting strands. Thus, there are fifteen type I11 homology units in plasma fibronectin. Evidence for two of the three splice variants found in rat liver cells [Schwarzbauer et al. (1983) Cell 35, 421 -4311 was obtained. No indication of the 'extra' type I11 domain present in some human fibroblast fibronectins [Kornblihtt et al. (1984) EMBO J. 3, 221 -2261 was found. Three carbohydrate groups (two glucosamine-based and one galactosamine-based) were identified, giving a total of eight carbohydrate groups in the longest splice variant of bovine plasma fibronectin. A second free sulfhydryl group (cysteine) was identified. This cysteine, like the first, is in a type I11 homology unit. HPLC patterns of peptides obtained from the C-terminal6-kDa fragment suggested that the interchain bridge pattern of fibronectin is antiparallel. The bovine plasma fibronectin sequence is highly homologous to the human cellular fibronectin sequence deduced from the cDNA sequence [Kornblihtt et al. (1985) EMBO J. 4,1755-17591. Fibronectin is a high-molecular-mass, multidomain glycoprotein found in a soluble form in blood plasma and in an insoluble form in loose connective tissue and basement membranes (reviewed in [l -31). Plasma fibronectin, which is synthesized and secreted by hepatocytes [4], and fibronectin synthesized by cultured fibroblasts are similar but not identical. Differences include carbohydrate content [5], fragmentation pattern [6], antigenicity [7] and number of chains [8, 91. Recently the existence of two fibronectin mRNA species from a human cell line was reported [lo]. One of these coded for an extra domain (ED) of 90 amino acid residues relative to the other mRNA. This ED insert seems to be absent in plasma fibronectin [lo] and may, therefore, account for at least some of the difference between cellular and plasma fibronectin.Plasma fibronectin consists of two subunits, which are linked to each other by two disulfide bonds near the C terminus [ll]. The subunits have a molecular mass of about 225 -250 kDa, that is, they vary in mass by 10 -25 kDa when subjected to SDS/polyacrylamide gel electrophoresis, under reducing conditions. The subunits have identical N-terminal and C-terminal sequences, showing that the difference is not due to limited proteolysis.Six cDNA clones, three from rat liver cells [12] and three from human cell lines [13-151, have been isolated corresponding to five different mRNAs. These differ in another area called IIICS (for type 111 connecting segment) C-terminal to the ED, and this area corresponds to the region in which (EC 3.4.21.19). differences between the two chains of fibronectin have been found (at the protein level) to be located [16-181. Recently the th...

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IntroductionDisease activity, severity and comorbidity contribute to increased mortality in patients with rheumatoid arthritis (RA). We evaluated the impact of age at disease onset on prognostic risk factors and treatment in patients with early disease.MethodsIn this study, 950 RA patients were followed regularly from the time of inclusion (<12 months from symptom onset) for disease activity (erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), tender and/or swollen joints, Visual Analogue Scale pain and global scores, and Disease Activity Score in 28 joints (DAS28)) and function (Health Assessment Questionnaire (HAQ)). Disease severity, measured on the basis of radiographs of the hands and feet (erosions based on Larsen score), extraarticular disease, nodules, and comorbidities and treatment (disease-modifying antirheumatic drugs (DMARDs), corticosteroids, biologics and nonsteroidal anti-inflammatory drugs) were recorded at the time of inclusion and at 5 years. Autoantibodies (rheumatoid factor, antinuclear antibodies and antibodies against cyclic citrullinated peptides (ACPAs)) and genetic markers (human leucocyte antibody (HLA) shared epitope and protein tyrosine phosphatase nonreceptor type 22 (PTPN22)) were analysed at the time of inclusion. Data were stratified as young-onset RA (YORA) and late-onset RA (LORA), which were defined as being below or above the median age at the time of onset of RA (58 years).ResultsLORA was associated with lower frequency of ACPA (P < 0.05) and carriage of PTPN22-T variant (P < 0.01), but with greater disease activity at the time of inclusion measured on the basis of ESR (P < 0.001), CRP (P < 0.01) and accumulated disease activity (area under the curve for DAS28 score) at 6 months (P < 0.01), 12 months (P < 0.01) and 24 months (P < 0.05), as well as a higher HAQ score (P < 0.01) compared with YORA patients. At baseline and 24 months, LORA was more often associated with erosions (P < 0.01 for both) and higher Larsen scores (P < 0.001 for both). LORA was more often treated with corticosteroids (P < 0.01) and less often with methotrexate (P < 0.001) and biologics (P < 0.001). YORA was more often associated with early DMARD treatment (P < 0.001). The results of multiple regression analyses supported our findings regarding the impact of age on chosen treatment.ConclusionYORA patients were more frequently ACPA-positive than LORA patients. LORA was more often associated with erosions, higher Larsen scores, higher disease activity and higher HAQ scores at baseline. Nevertheless, YORA was treated earlier with DMARDs, whilst LORA was more often treated with corticosteroids and less often with DMARDs in early-stage disease. These findings could have implications for the development of comorbidities.

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