Targeting collagen biosynthesis by small molecules inhibiting the function of the peptide-substrate-binding domain of collagen prolyl 4-hydroxylases

Collagen prolyl 4-hydroxylase (C-P4H) is an essential enzyme in collagen synthesis and known to be a potential target for drugs that prevent excess collagen formation. Currently known C-P4H inhibitors target the catalytic site of C-P4H, being analogues of 2-oxoglutarate (2OG). However, in mammalian cells there are many other 2OG-dependent dioxygenases with a highly similar catalytic domain, which limits the selective specificity of drugs targeting C-P4H activity. The peptide-substrate-binding (PSB) domain is unique for the C-P4H family and known to be important for the catalytic efficiency of C-P4H. Therefore, interfering with peptide binding to the PSB domain might allow more specific inhibition of the hydroxylation activity of C-P4Hs. We developed a robust FRET-based high-throughput screening assay (Z’ > 0.73) based on PSB-peptide interactions. This assay was used to screen a peptidomimetic library of 15614 compounds with the PSB domains of C-P4H isoforms I and II. A hit compound (OUL-PSBi-001) was identified with IC50s of 40 µM and 62 µM for PSB-I and PSB-II, respectively. We also showed that this compound indeed inhibits the catalytic activity of the full-length CP4H-I and -II. This FRET assay provides a new strategy for finding selective inhibitors for the treatment of fibrotic diseases and cancer.