The major function of the link protein (LP) of proteoglycan aggregates (PG) appears to be to stabilize the aggregation of PG monomers with hyaluronic acid (HA). Such aggregates form ordered structures with collagen and together these form the majority of the macromolecular species in cartilage. The mechanism of assembly is not known, but is thought to involve the formation of LP-PG binary complexes which subsequently bind to HA extracellularly. The mechanisms for the modulation of this process, either intrinsic or via cellular processes, are currently unknown. We have previously described the primary structures of LP and the PG region which binds to HA (HABR) and found them to be very similar. In addition to HABR, another domain in PG is similar to LP. This is the recently described G2 domain. This is very similar to both the COOH-terminal half of LP and HABR but as yet has not been assigned a function. We propose to extend the descriptions of the primary structures of these regions by outlining the detailed functions of these domains. We intend to define the exact regions of LP and HABR which bind to HA and which regions bind to HABR and LP respectively. Peptides derived from the intact proteins or synthesized de novo will be analyzed for their ability to (1) inhibit aggregation and (2) bind to the macromolecules in question. Some synthetic peptides have already been synthesized and display interesting properties. In addition, maps of exposed residues in HABR and LP will be developed by differential derivatiztion of the monomers, the binary complexes and the ternary complex of PG-HA and LP. This will enable us to define the residues which are directly involved in aggregation. Throughout these studies, we will utilize the similarity between LP and HABR as an internal control: results obtained with one molecule should be reflected in the other. Eventually, we will develop a model for aggregation which can be used in defining cartilage repair processes.

Agency
National Institute of Health (NIH)
Institute
National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS)
Type
Research Project (R01)
Project #
5R01AR035322-06
Application #
3157154
Study Section
Pathobiochemistry Study Section (PBC)
Project Start
1989-04-01
Project End
1993-03-31
Budget Start
1991-04-01
Budget End
1993-03-31
Support Year
6
Fiscal Year
1991
Total Cost
Indirect Cost
Name
University of South Florida
Department
Type
Schools of Medicine
DUNS #
City
Tampa
State
FL
Country
United States
Zip Code
33612
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Cheng, H; Caterson, B; Neame, P J et al. (1996) Differential distribution of lumican and fibromodulin in tooth cementum. Connect Tissue Res 34:87-96
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Neame, P J; Barry, F P (1994) The link proteins. EXS 70:53-72
Neame, P J; Sommarin, Y; Boynton, R E et al. (1994) The structure of a 38-kDa leucine-rich protein (chondroadherin) isolated from bovine cartilage. J Biol Chem 269:21547-54
Barry, F P; Neame, P J; Sasse, J et al. (1994) Length variation in the keratan sulfate domain of mammalian aggrecan. Matrix Biol 14:323-8
Neame, P J; Barry, F P (1993) The link proteins. Experientia 49:393-402
Neame, P J; Young, C N; Brock, C W et al. (1993) Pleiotrophin is an abundant protein in dissociative extracts of bovine fetal epiphyseal cartilage and nasal cartilage from newborns. J Orthop Res 11:479-91

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