Oligomeric forms of the 148 kDa cartilage matrix protein.
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ABSTRACT:
SUBMITTER: Zeineldin R
PROVIDER: S-EPMC1218969 | biostudies-other | 1997 Dec
REPOSITORIES: biostudies-other
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Project description:INTRODUCTION: Cartilage oligomeric matrix protein (COMP) is a major non-collagenous component of cartilage. Earlier, we developed a new mouse model for rheumatoid arthritis using COMP. This study was undertaken to investigate the epitope specificity and immunopathogenicity of COMP-specific monoclonal antibodies (mAbs). METHODS: B cell immunodominant regions on the COMP molecule were measured with a novel enzyme-linked immunosorbent assay using mammalian expressed full-length mouse COMP as well as a panel of recombinant mouse COMP fragments. 18 mAbs specific to COMP were generated and the pathogenicity of mAbs was investigated by passive transfer experiments. RESULTS: B cell immunodominant epitopes were localized within 4 antigenic domains of the COMP but with preferential response to the epidermal growth factor (EGF)-like domain. Some of our anti-COMP mAbs showed interactions with the native form of COMP, which is present in cartilage and synovium. Passive transfer of COMP-specific mAbs enhanced arthritis when co-administrated with a sub-arthritogenic dose of a mAb specific to collagen type II. Interestingly, we found that a combination of 5 COMP mAbs was capable of inducing arthritis in naive mice. CONCLUSIONS: We have identified the specificities of mAbs to COMP and their contribution to the development of arthritis. These findings will further improve our understanding of the autoantibody mediated immunopathologies occurring widely in rheumatoid arthritis (RA), as well as in other autoimmune disorders.
| S-EPMC3580587 | biostudies-literature
Project description:Loss of articular cartilage because of extracellular matrix breakdown is the hallmark of arthritis. Degradative fragments of cartilage oligomeric matrix protein (COMP), a prominent noncollagenous matrix component in articular cartilage, have been observed in the cartilage, synovial fluid, and serum of arthritis patients. The molecular mechanism of COMP degradation and the enzyme(s) responsible for it, however, remain largely unknown. ADAMTS-12 (a disintegrin and metalloprotease with thrombospondin motifs) was shown to associate with COMP both in vitro and in vivo. ADAMTS-12 selectively binds to only the epidermal growth factor-like repeat domain of COMP of the four functional domains tested. The four C-terminal TSP-1-like repeats of ADAMTS-12 are shown to be necessary and sufficient for its interaction with COMP. Recombinant ADAMTS-12 is capable of digesting COMP in vitro. The COMP-degrading activity of ADAMTS-12 requires the presence of Zn2+ and appropriate pH (7.5-9.5), and the level of ADAMTS-12 in the cartilage and synovium of patients with both osteoarthritis and rheumatoid arthritis is significantly higher than in normal cartilage and synovium. Together, these findings indicate that ADAMTS-12 is a new COMP-interacting and -degrading enzyme and thus may play an important role in the COMP degradation in the initiation and progression of arthritis.
| S-EPMC1483932 | biostudies-literature
Project description:Cartilage oligomeric matrix protein/thrombospondin 5 (COMP/TSP5) is a major component of the extracellular matrix (ECM) of the musculoskeletal system. Its importance is underscored by its association with several growth disorders. In this report, we investigated its interaction with aggrecan, a major component of cartilage ECM. We also tested a COMP/TSP5 mutant, designated MUT3 that accounts for 30% of human pseudoachondroplasia cases, to determine if the mutation affects function. Using a solid-phase binding assay, we have shown that COMP/TSP5 can bind aggrecan. This binding was decreased with MUT3, or when COMP/TSP5 was treated with EDTA, indicating the presence of a conformation-dependent aggrecan binding site. Soluble glycosaminoglycans (GAGs) partially inhibited binding, suggesting that the interaction was mediated in part through aggrecan GAG side chains. Using affinity co-electrophoresis, we showed that COMP/TSP5, in its calcium-replete conformation, bound to heparin, chondroitin sulfates, and heparan sulfate; this binding was reduced with EDTA treatment of COMP/TSP5. MUT3 showed weaker binding than calcium-repleted COMP/TSP5. Using recombinant COMP/TSP5 fragments, we found that the "signature domain" could bind to aggrecan, suggesting that this domain can mediate the interaction of COMP/TSP5 and aggrecan. In summary, our data indicate that COMP/TSP5 is an aggrecan-binding protein, and this interaction is regulated by the calcium-sensitive conformation of COMP/TSP5; interaction of COMP with aggrecan can be mediated through the GAG side chains on aggrecan and the "signature domain" of COMP/TSP5. Our results suggest that COMP/TSP5 may function to support matrix interactions in cartilage ECM.
| S-EPMC2905148 | biostudies-literature
Project description:Lubricin, a heavily O-glycosylated protein, is essential for boundary lubrication of articular cartilage. Strong surface adherence of lubricin is required given the extreme force it must withstand. Disulfide bound complexes of lubricin and cartilage oligomeric matrix protein (COMP) have recently been identified in arthritic synovial fluid suggesting they may be lost from the cartilage surface in osteoarthritis and inflammatory arthritis. This investigation was undertaken to localise COMP-lubricin complexes within cartilage and investigate if other cartilage proteins are involved in anchoring lubricin to the joint. Immunohistochemical analysis of human cartilage biopsies showed lubricin and COMP co-localise to the cartilage surface. COMP knockout mice, however, presented with a lubricin layer on the articular cartilage leading to the further investigation of additional lubricin binding mechanisms. Proximity ligation assays (PLA) on human cartilage biopsies was used to localise additional lubricin binding partners and demonstrated that lubricin bound COMP, but also fibronectin and collagen II on the cartilage surface. Fibronectin and collagen II binding to lubricin was confirmed and characterised by solid phase binding assays with recombinant lubricin fragments. Overall, COMP, fibronectin and collagen II bind lubricin, exposed on the articular cartilage surface suggesting they may be involved in maintaining essential boundary lubrication.
| S-EPMC5640667 | biostudies-literature
Project description:Two isoforms of the 90-kDa heat shock protein, HSP90alpha and HSP90beta, are present in the cytosol of mammalian cells. Analysis by polyacrylamide gel electrophoresis under nondenaturing conditions (native PAGE) revealed that HSP90alpha predominantly exists as a homodimer and that HSP90beta is present mainly as a monomer [Minami, Kawasaki, Miyata, Suzuki and Yahara (1991) J. Biol. Chem. 266, 10099-10103]. However, only the dimeric form has been observed under other analytical conditions such as gradient centrifugation. In this study, therefore, we investigated native forms of HSP90 by use of immunochemical techniques with isoform-specific monoclonal antibodies recently developed in our laboratory. Glycerol gradient centrifugation at the physiological salt concentration as well as native PAGE analysis of rat liver cytosol revealed oligomeric forms of HSP90alpha sedimenting at 8-10S as predominant ones. On the other hand, the glycerol gradient centrifugation revealed multiple forms of HSP90beta oligomers sedimenting at 6-12S. All of the HSP90beta oligomers, however, migrated at 100-kDa monomer and 190-kDa dimer positions on native PAGE. A novel two-dimensional double native PAGE revealed that the entity was converted from the HSP90beta dimer to monomers during the electrophoresis. The same PAGE further revealed that the HSP90alpha oligomer also dissociated into dimers during the electrophoresis. Full-length form of bacterially-expressed human HSP90alpha migrated as dimers, but a considerable amount did not penetrate into the gel under native PAGE conditions, indicating the existence of oligomeric forms. Electrophoretic studies of deletion mutants of HSP90 demonstrated that the C-terminal 200 amino acids were capable of forming oligomers. Taken together, we conclude that both of the HSP90 isoforms predominantly exist as oligomeric forms in the cytosol even under unstressed conditions but that they artificially dissociate into smaller forms when subjected to native PAGE.
| S-EPMC1219235 | biostudies-other
Project description:In an effort to define the biological functions of COMP, a functional genetic screen was performed. This led to the identification of extracellular matrix protein 1 (ECM1) as a novel COMP-associated partner. COMP directly binds to ECM1 both in vitro and in vivo. The EGF domain of COMP and the C-terminus of ECM1 mediate the interaction between them. COMP and ECM1 colocalize in the growth plates invivo. ECM1 inhibits chondrocyte hypertrophy, matrix mineralization, and endochondral bone formation, and COMP overcomes the inhibition by ECM1. In addition, COMP-mediated neutralization of ECM1 inhibition depends on their interaction, since COMP largely fails to overcome the ECM1 inhibition in the presence of the EGF domain of COMP, which disturbs the association of COMP and ECM1. These findings provide the first evidence linking the association of COMP and ECM1 and the biological significance underlying the interaction between them in regulating endochondral bone growth.
| S-EPMC2862898 | biostudies-literature
Project description:Liver fibrosis is characterized by significant accumulation of extracellular matrix (ECM) proteins, mainly fibrillar collagen-I, as a result of persistent liver injury. Cartilage oligomeric matrix protein (COMP) is largely found in the ECM of skeletal tissue. Increased COMP expression has been associated with fibrogenesis in systemic sclerosis, lung fibrosis, chronic pancreatitis, cirrhosis and hepatocellular carcinoma. We hypothesized that COMP could induce fibrillar collagen-I deposition and participate in matrix remodeling thus contributing to the pathophysiology of liver fibrosis.Thioacetamide (TAA) and carbon tetrachloride (CCl4) were used to induce liver fibrosis in wild-type (WT) and Comp-/- mice. In vitro experiments were performed with primary hepatic stellate cells (HSCs).COMP expression was detected in livers from control WT mice and was upregulated in response to either TAA or CCl4-induced liver fibrosis. TAA-treated or CCl4-injected Comp-/- mice showed less liver injury, inflammation and fibrosis compared to their corresponding control WT mice. Challenge of HSCs with recombinant COMP (rCOMP) induced intra- plus extracellular collagen-I deposition and increased matrix metalloproteinases (MMPs) 2, 9 and 13, albeit similar expression of transforming growth factor beta (TGF?) protein, in addition to Tgf?, tumour necrosis factor alpha (Tnf?) and tissue inhibitor of metalloproteinases-1 (Timp1) mRNAs. We demonstrated that COMP binds collagen-I; yet, it does not prevent collagen-I cleavage by MMP1. Last, rCOMP induced collagen-I expression in HSCs via CD36 receptor signaling and activation of the MEK1/2-pERK1/2 pathway.These results suggest that COMP contributes to liver fibrosis by regulating collagen-I deposition.Cartilage oligomeric matrix protein (COMP) induces fibrillar collagen-I deposition via the CD36 receptor signaling and activation of the MEK1/2-pERK1/2 pathway, and participates in extracellular matrix remodeling contributing to the pathophysiology of liver fibrosis.
| S-EPMC5831373 | biostudies-literature
Project description:Pseudoachondroplasia (PSACH) and autosomal dominant multiple epiphyseal dysplasia (MED) are chondrodysplasias resulting in short-limbed dwarfism, joint pain and stiffness and early onset osteoarthritis. All PSACH, and the largest proportion of MED, result from mutations in cartilage oligomeric matrix protein (COMP). The first mutations in COMP were identified in 1995 in patients with both PSACH and MED and subsequently there has been over 30 publications describing COMP mutations in at least 250 PSACH-MED patients. However, despite these discoveries, a methodical analysis of the relationship between COMP mutations and phenotypes has not been undertaken. In particular, there has, to date, been little correlation between the type and location of a COMP mutation and the resulting phenotype of PSACH or MED. To determine if genotype to phenotype correlations could be derived for COMP, we collated 300 COMP mutations, including 25 recently identified novel mutations. The results of this analysis demonstrate that mutations in specific residues and/or regions of the type III repeats of COMP are significantly associated with either PSACH or MED. This newly derived genotype to phenotype correlation may aid in determining the prognosis of PSACH and MED, including the prediction of disease severity, and in the long term guide genetic counselling and contribute to the clinical management of patients with these diseases.
| S-EPMC4051597 | biostudies-literature
Project description:Cartilage Oligomeric Matrix Protein (COMP) is a soluble pentameric protein expressed in cartilage and involved in collagen organization. Publicly available mRNA expression array data indicated that COMP is overexpressed in breast cancer tissue. Tissue microarrays derived from two cohorts of patients with breast cancer (n = 122 and n = 498) were immunostained, which revealed varying amounts of COMP, both in the tumor cells and surrounding stroma. High levels of COMP in tumor cells correlated, independently of other variables, with poor survival and faster recurrence (metastases). Breast cancer cells, MDA-MB-231, stably expressing COMP were injected into the mammary fat pad of SCID (CB-17/Icr-Prkdcscid/Rj) mice. Tumors expressing COMP grew to significantly larger volumes and had increased metastasis as compared to control, mock transfected, tumors. In vitro experiments confirmed that COMP expressing cells were more invasive, which was in part related to an upregulation of metalloprotease-9. Further, microarray analyses of gene expression in tumors formed in vivo showed that expression of COMP was protective against endoplasmatic reticulum stress. This observation was confirmed in vitro since COMP expressing cells showed better survival than mock when treated with brefeldin, which leads to accumulation of proteins in endoplasmatic reticulum. The mRNA pathway analyses also implicated a metabolic switch leading to a more severe Warbug effect, which was confirmed in vitro by measurement of cell respiration and lactate production. In conclusion, COMP is a novel biomarker in breast cancer, which contributes to the severity of the disease by several novel molecular mechanisms.
2015-10-01 | GSE69668 | GEO
Project description:PurposeCartilage oligomeric matrix protein (COMP) is known as a large pentameric glycoprotein, which interacts with various extracellular matrix proteins in tissues. COMP has been reported to play a role in multiple connective tissue disorders. Recently, elevated COMP levels have been found to be associated with increased tumor size, metastases, faster recurrence of cancer, and overall poorer survival in several cancers. However, the clinical importance of COMP in urothelial carcinoma remains unclear. We investigated the association between COMP expression and clinical outcomes in urothelial carcinoma.Patients and methodsIn this retrospective study, we collected urothelial carcinoma (UC) tissue from 340 upper urinary tract UC (UTUC) patients and 295 urinary bladder UC (UBUC) patients. Pearson's chi-square test, Kaplan-Meier analysis, and the multivariate Cox proportional hazards model was used to examine the relationship between COMP expression and patient characteristics, pathological findings, and patient survival, such as metastasis-free survival (MFS) and disease-specific survival (DSS).ResultsA total of 295 UBUC patients and 340 UTUC patients were recruited. The COMP mRNA level was significantly higher among invasive tumors (pT2-pT4) than in noninvasive tumors (pTa-T1) in UBUC groups (P < 0.01). COMP overexpression was associated with advanced T stage, nodal metastases, vascular invasion, perineural invasion, high histological grade, and high mitotic rate in both UBUC and UTUC cohorts. COMP overexpression was predictive of shorter DSS (hazard ratio [HR] in UBUC, 3.986, P < 0.001; in UTUC, 2.283, P = 0.027] and MFS (HR in UBUC, 6.813, P < 0.001; in UTUC, 4.070, P < 0.001). Kaplan-Meier analysis demonstrated high COMP expression associated with poor DSS and MFS in UTUC and UBUC groups (all P < 0.0001).ConclusionCOMP overexpression was linked to poor clinical prognosis and poor pathological features in UC. These results suggest COMP as a biomarker for UC.
| S-EPMC9252317 | biostudies-literature