Distribution of two alternatively spliced variants of the type II collagen N-propeptide compared with the C-propeptide in bovine chondrocyte pellet cultures.
We have analyzed the distribution of type II collagen N- and C-propeptides in the cell layers and culture medium of bovine articular chondrocyte pellet cultures. Two splice variants of the type II collagen N-propeptide were detected by immunoblotting and immunoassay, using a new anti-peptide antibody, while the C-propeptide was detected using a monoclonal antibody. Type II collagen molecules containing the N-propeptide were detected weakly in cell layers, but not in tissue culture medium of chondrocyte pellet cultures, and both splice variants were observed. Free N-propeptide could not be detected in cell layers or medium. Type II procollagen molecules containing the C-propeptide were detected strongly in cell layers, but not in tissue culture medium, while the free C-propeptide was detected in both cell layers and medium. Since the N- and C-propeptides must be synthesized in a 1:1 molar ratio, we conclude that the N-propeptide is metabolized more quickly than the C-propeptide in this system. Our model can be used to study regulation of procollagen synthesis and propeptidase activity.