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Binding and localization of recombinant lubricin to articular cartilage surfaces
Author(s) -
Jones Aled R.C.,
Gleghorn Jason P.,
Hughes Clare E.,
Fitz Lori J.,
Zollner Richard,
Wainwright Shane D.,
Caterson Bruce,
Morris Elisabeth A.,
Bonassar Lawrence J.,
Flannery Carl R.
Publication year - 2007
Publication title -
journal of orthopaedic research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.041
H-Index - 155
eISSN - 1554-527X
pISSN - 0736-0266
DOI - 10.1002/jor.20325
Subject(s) - cartilage , articular cartilage , osteoarthritis , recombinant dna , microbiology and biotechnology , boundary lubrication , glycoprotein , synovial fluid , proteoglycan , synovial joint , chemistry , medicine , gene , anatomy , biochemistry , biology , pathology , lubricant , alternative medicine , organic chemistry
Abstract Lubricin is a secreted, cytoprotective glycoprotein that contributes to the essential boundary lubrication mechanisms necessary for maintaining low friction levels at articular cartilage surfaces. Diminishment of lubricin function is thereby implicated as an adverse contributing factor in degenerative joint diseases such as osteoarthritis. Lubricin occurs as a soluble component of synovial fluid, and is synthesized and localized in the superficial layer of articular cartilage (and thus has also been described as “superficial zone protein”, or SZP); however, defined interactions responsible for lubricin retention at this site are not well characterized. In the current studies, we identified molecular determinants that enable lubricin to effectively bind to articular cartilage surfaces. Efficient and specific binding to the superficial zone was observed for synovial lubricin, as well as for recombinant full‐length lubricin and a protein construct comprising the lubricin C‐terminal (hemopexin‐like) domain (LUB‐C, encoded by exons 7–12). A construct representing the N‐terminal region of lubricin (LUB‐N, encoded by exons 2–5) exhibited no appreciable cartilage‐binding ability, but displayed the capacity to dimerize, and thus potentially influence lubricin aggregation. Disulfide bond disruption significantly attenuated recombinant lubricin and LUB‐C binding to cartilage surfaces, demonstrating a requirement for protein secondary structure in facilitating the appropriate localization of lubricin at relevant tissue interfaces. These findings help identify additional key attributes contributing to lubricin functionality, which would be expected to be instrumental in maintaining joint homeostasis. © 2006 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res