Identification of HSP47 binding site on native collagen and its implications on the development of HSP47 inhibitors

Cai, H., Sasikumar, P., Little, G., Bihan, D., Hamaia, S. W., Zhou, A., Gibbins, J. M. ORCID: https://orcid.org/0000-0002-0372-5352 and Farndale, R. W. (2021) Identification of HSP47 binding site on native collagen and its implications on the development of HSP47 inhibitors. Biomolecules, 11 (7). 983. ISSN 2218-273X doi: 10.3390/biom11070983

Abstract/Summary

Abstract: HSP47 (Heat Shock Protein 47) is a collagen-specific molecular chaperone that is essential for procollagen folding and function. Previous studies have shown that HSP47 binding requires a critical Arg residue at the Y position of the (Gly-Xaa-Yaa) repeats of collagen, however, the exact binding sites of HSP47 on native collagens are not fully defined. To address this, we mapped the HSP47 binding sites on collagens through an ELISA binding assay using collagen Toolkits, synthetic collagen peptides covering the entire amino acid sequences of collagen types II and III assembled in triple-helical conformation. Our results showed that HSP47 binds to only a few of the GXR motifs in collagen and most of the HSP47 binding sites identified are located near the N-terminal part of collagen triple-helical region. Molecular modelling and binding energy calculation indicated that residues flanking the key Arg in the collagen sequence also play an important role in defining the high affinity HSP47 binding site of collagen. Based on this binding mode of HSP47 to collagen, virtual screening targeting both the Arg binding site and its neighboring area on the HSP47 surface, and subsequently bioassay, identified two novel compounds with blocking activity towards HSP47 binding of collagen. Overall, our study revealed the native HSP47 binding sites on collagen and provided novel information for the design of small molecule inhibitors of HSP47.