The
metalloprotease meprin has been implicated in tissue remodelling due to its capability to degrade extracellular matrix components. Here, we investigated the susceptibility of
tenascin-C to cleavage by meprinbeta and the functional properties of its proteolytic fragments. A set of
monoclonal antibodies against chicken and human
tenascin-C allowed the mapping of proteolytic fragments generated by meprinbeta. In chicken
tenascin-C, meprinbeta processed all three major splicing variants by removal of 10kDa N-terminal and 38kDa C-terminal
peptides, leaving a large central part of subunits intact. A similar cleavage pattern was found for large human
tenascin-C variant where two N-terminal
peptides (10 or 15kDa) and two C-terminal fragments (40 and 55kDa) were removed from the intact subunit. N-terminal sequencing revealed the exact
amino acid positions of cleavage sites. In both chicken and human
tenascin-C N-terminal cleavages occurred just before and/or after the heptad repeats involved in subunit oligomerization. In the human
protein, an additional cleavage site was identified in the alternative
fibronectin type III repeat D. Whereas all these sites are known to be attacked by several other
proteases, a unique cleavage by meprinbeta was located to the 7th constant
fibronectin type III repeat in both chicken and human
tenascin-C, thereby removing the C-terminal domain involved in its anti-adhesive activity. In cell adhesion assays meprinbeta-digested human
tenascin-C was not able to interfere with
fibronectin-mediated cell spreading, confirming cleavage in the anti-adhesive domain. Whereas the expression of meprinbeta and
tenascin-C does not overlap in normal colon tissue, inflamed lesions of the mucosa from patients with
Crohn's disease exhibited many meprinbeta-positive leukocytes in regions where
tenascin-C was strongly induced. Our data indicate that, at least under pathological conditions, meprinbeta might attack specific functional sites in
tenascin-C that are important for its oligomerization and anti-adhesive activity.