Journal
BIOCHIMICA ET BIOPHYSICA ACTA-GENERAL SUBJECTS
Volume 1790, Issue 5, Pages 375-384Publisher
ELSEVIER SCIENCE BV
DOI: 10.1016/j.bbagen.2009.03.016
Keywords
Proteyglycan 4; Lubricin; Synovial fluid; Mucin; Cartilage
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Funding
- Arthritis Foundation (JDS)
- Robert Katz and Joan and Paul Rubschlager Endowment for Osteoarthritis Research at Rush University Medical College (AHP)
- Faculty of Kinesiology and the Schulich School of Engineering's Centre for Bioengineering Research and Education at the University of Calgary (TAS)
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Background: The proteoglycan 4 (PRG4) gene encodes for a mucin-like O-linked glycosylated protein with several names, including lubricin and superficial zone protein. The objective of this study was to analyze PRG4 in normal bovine calf and steer synovial fluids for evidence of native multimers formed by intermolecular disulfide bonds. Methods: A combination of mucin biochemical techniques, with antibodies to both terminal domains and the mucin-like domain of PRG4, were used for analyses. Results: Multimers were present in both calf and steer fluids, and reduction and alkylation converts the multimeric complex (likely dimeric) into monomeric subunits. Tandem mass spectrometry analyses supported the Western blot data and identified PRG4 in the reduced similar to 345 kDa monomeric form. Interestingly, similar to 70 kDa fragments released upon reduction contained peptides from both the N and C terminal regions, which most likely represent fragments of a sparsely glycosylated PRG4 population that are disulfide-linked to extensively glycosylated, intact monomers. Conclusions: The analyses described here have demonstrated the presence of native disulfide-bonded multimers of PRG4 in normal bovine synovial fluids. General significance: These structures are similar to those described for multimerization of mucins in general. Such multimerization and proteolytic cleavage of PRG4 may have functional significance in joint health and disease. (C) 2009 Elsevier B.V. All rights reserved.
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