NEUTROPHIL COLLAGENASE (MMP-8) CLEAVES AT THE AGGRECANASE SITE E(373)-A(374) IN THE INTERGLOBULAR DOMAIN OF CARTILAGE AGGRECAN

Native and recombinant neutrophil collagenase (MMP-8) was shown to cleave at the E(373)-A(374) 'aggrecanase'' site in the interglobular domain of aggrecan. The time course of digestion in vitro showed that MMP-8 cleaved initially at N-341-F-342, the predominant metalloproteinase site, before cleaving at the E(373)-A(374) site. A synthetic peptide, IPENFFG, inhibited cleavage at E(373)-A(374) but not N-341-F-342 in vitro, indicating that the E(373)-A(374) sequence was a less preferred site for MMP-8 cleavage than N-341-F-342. IPENFFG also inhibited release of A(374) RGSVI fragments from cartilage in explant culture, suggesting that a metalloproteinase cleaved at the aggrecanase site in situ. The possibility remains that 'aggrecanase' may be a metalloproteinase in cartilage.