title: Protein modification by deamidation indicates variations in joint extracellular matrix turnover.
abstract: As extracellular proteins age, they undergo and accumulate nonenzymatic post-translational modifications that cannot be repaired. We hypothesized that these could be used to systemically monitor loss of extracellular matrix due to chronic arthritic diseases such as osteoarthritis (OA). To test this, we predicted sites of deamidation in cartilage oligomeric matrix protein (COMP) and confirmed, by mass spectroscopy, the presence of deamidated (Asp(64)) and native (Asn(64)) COMP epitopes (mean 0.95% deamidated COMP (D-COMP) relative to native COMP) in cartilage. An Asp(64), D-COMP-specific ELISA was developed using a newly created monoclonal antibody 6-1A12. In a joint replacement study, serum D-COMP (p = 0.017), but not total COMP (p = 0.5), declined significantly after replacement demonstrating a joint tissue source for D-COMP. In analyses of 450 participants from the Johnston County Osteoarthritis Project controlled for age, gender, and race, D-COMP was associated with radiographic hip (p < 0.0001) but not knee (p = 0.95) OA severity. In contrast, total COMP was associated with radiographic knee (p < 0.0001) but not hip (p = 0.47) OA severity. D-COMP was higher in soluble proteins extracted from hip cartilage proximal to OA lesions compared with remote from lesions (p = 0.007) or lesional and remote OA knee (p < 0.01) cartilage. Total COMP in cartilage did not vary by joint site or proximity to the lesion. This study demonstrates the presence of D-COMP in articular cartilage and the systemic circulation, and to our knowledge, it is the first biomarker to show specificity for a particular joint site. We believe that enrichment of deamidated epitope in hip OA cartilage indicates a lesser repair response of hip OA compared with knee OA cartilage.
authors.affiliation: Departments of Medicine, Duke University Medical Center, Durham, North Carolina 27710, USA.
authors.forename: Jonathan B
authors.initials: JB
authors.lastname: Catterall
authors.forename: Ming F
authors.initials: MF
authors.lastname: Hsueh
authors.forename: Thomas V
authors.initials: TV
authors.lastname: Stabler
authors.forename: Christopher R
authors.initials: CR
authors.lastname: McCudden
authors.forename: Michael
authors.initials: M
authors.lastname: Bolognesi
authors.forename: Robert
authors.initials: R
authors.lastname: Zura
authors.forename: Joanne M
authors.initials: JM
authors.lastname: Jordan
authors.forename: Jordan B
authors.initials: JB
authors.lastname: Renner
authors.forename: Sheng
authors.initials: S
authors.lastname: Feng
authors.forename: Virginia B
authors.initials: VB
authors.lastname: Kraus
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D058846:Antibodies, Monoclonal, Murine-Derived / Q000737:chemistry; D019644:Arthroplasty, Replacement, Hip; D019645:Arthroplasty, Replacement, Knee; D001216:Asparagine / Q000378:metabolism; D001224:Aspartic Acid / Q000378:metabolism; D002356:Cartilage / Q000378:metabolism* / Q000473:pathology / Q000601:surgery; D064236:Cartilage Oligomeric Matrix Protein; D015331:Cohort Studies; D004797:Enzyme-Linked Immunosorbent Assay; D016326:Extracellular Matrix Proteins / Q000378:metabolism*; D005260:Female; D006023:Glycoproteins / Q000378:metabolism*; D006801:Humans; D008297:Male; D013058:Mass Spectrometry; D064235:Matrilin Proteins; D008875:Middle Aged; D015207:Osteoarthritis, Hip / Q000378:metabolism* / Q000473:pathology / Q000601:surgery; D020370:Osteoarthritis, Knee / Q000378:metabolism* / Q000473:pathology / Q000601:surgery; D011499:Protein Processing, Post-Translational
chemical_list: D058846:Antibodies, Monoclonal, Murine-Derived; D064236:Cartilage Oligomeric Matrix Protein; D016326:Extracellular Matrix Proteins; D006023:Glycoproteins; D064235:Matrilin Proteins; C577553:TSP5 protein, human; D001224:Aspartic Acid; D001216:Asparagine