Structure, substrate recognition and therapeutic targeting of the human ADAMTS-5 spacer domain

The ADAMTS (a disintegrin-like and metalloproteinase domain with thrombospondin type 1 motifs) family of secreted metalloproteinases plays essential roles in extracellular matrix remodeling. ADAMTS-5 contributes to cartilage degradation, cleaving proteoglycans such as aggrecan and versican, and being involved in both physiological tissue turnover and pathological processes such as osteoarthritis and atherosclerosis. Although structural insights into its catalytic domain have informed inhibitor development, the role of ancillary domains, particularly the spacer domain, in substrate recognition and specificity remains underexplored. Here, we report the crystal structure of a segment of human ADAMTS-5 encompassing the C-terminal portion of the cysteine-rich domain and the spacer domain (residues 694-876). This structure reveals critical features of the spacer domain, including the hypervariable loops that function as exosites essential for the binding of aggrecan and versican. Our findings provide new structural insights into the molecular determinants of the substrate specificity of ADAMTS-5 and underscore the spacer domain as a promising target for the development of selective inhibitors.