Abstract
In cartilage, link protein(s) (LP) stabilize proteoglycan aggregates via their specific association with hyaluronic acid and proteoglycan monomers. Two major link glycoproteins are produced in bovine articular cartilage, designated LP1 (49.5 kDa) and LP2 (44.0 kDa), whereas rat chondrosarcoma produces a single link protein species similar in size to bovine LP2. Although multiple link proteins differ to a significant degree in carbohydrate content, it is not known whether they arise from variable glycosylation of a single common protein core or from complete glycosylation of different protein cores. Biosynthesis of these molecules has been studied under conditions where differences generated by N-linked glycosylation would not be evident. Link proteins were immunoprecipitated 1) from cell-free translation products of total cellular and size fractionated RNA and 2) from cell lysates and medium of cultured chondrocytes using short term radioactive labeling of the protein in the presence and absence of tunicamycin. A 42-kDa link protein precursor is synthesized by cell-free translation of either rat chondrosarcoma or bovine chondrocyte mRNa. An apparently single 41.5-kDa link protein is synthesized with inhibition of N-linked glycosylation by tunicamycin, whereas LP1 and LP2 are the mature products of cultured bovine chondrocytes. The size range of translatable rat chondrosarcoma LP mRNA is 4.0-5.5 kilobase pairs and bovine LP mRNA is 3.0-4.5 kilobase pairs, both much larger than required to encode the link protein molecule. These results suggest that a single link protein precursor gives rise to multiple fully glycosylated forms and that link protein is not synthesized as a significantly larger "pro" form.
Highlights
In cartilage, link protein(s) (LP) stabilize proteoglayc-id (Hardingham, 1979;Tang et al, 1979; Kimura et al, 1979; can aggregates via their specific association with hy- 1980), influencethe dimensionsof the aggregate
An ap- ogeneity or the controlof multiple link protein synthesis.To parently single 41.5-kDa link protein is synthesized begin to address thisproblem, we have examined thebiosynwith inhibition of N-linked glycosylation by tunica- thesis of link proteins under conditionws here differences due mycin, whereas LP1 and LPa2re the mature products to glycosylation and the generation of additional species due of culturedbovinechondrocytes.Thesizerange of to proteolytic degradation would not be evident
Antiserum R13 was obtained from Dr Bruce Caterson, University of West Virginia, and Dr James Christner, University of Alabama at Birmingham
Summary
Link protein(s) (LP) stabilize proteoglayc-id (Hardingham, 1979;Tang et al, 1979; Kimura et al, 1979; can aggregates via their specific association with hy- 1980), influencethe dimensionsof the aggregate Antiserum and Monoclonal Antibodies-The monoclonal antibody (mAb) 8A4 wasused to immunoprecipitate link protein from cell-free translation products of rat chondrosarcoma. A polyclonal antiserum designated R13 wasused to immunoprecipitate link protein from cellfree translation products of bovine mRNA or from cultured bovine chondrocyte lysates and medium.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
