Shi, ShuiliangKelly, Brian J.Wang, CongrongKlingler, KenChan, AlbertEckert, George J.Trippel, Stephen B.2018-01-042018-01-042018-03Shi, S., Kelly, B. J., Wang, C., Klingler, K., Chan, A., Eckert, G. J., & Trippel, S. B. (2017). Human IGF-I Propeptide a promotes articular chondrocyte biosynthesis and employs glycosylation-dependent heparin binding. Biochimica et Biophysica Acta (BBA) - General Subjects. https://doi.org/10.1016/j.bbagen.2017.11.017https://hdl.handle.net/1805/14937Background Insulin-like growth factor I (IGF-I) is a key regulator of chondrogenesis, but its therapeutic application to articular cartilage damage is limited by rapid elimination from the repair site. The human IGF-I gene gives rise to three IGF-I propeptides (proIGF-IA, proIGF-IB and proIGF-IC) that are cleaved to create mature IGF-I. In this study, we elucidate the processing of IGF-I precursors by articular chondrocytes, and test the hypotheses that proIGF-I isoforms bind to heparin and regulate articular chondrocyte biosynthesis. Methods Human IGF-I propeptides and mutants were overexpressed in bovine articular chondrocytes. IGF-I products were characterized by ELISA, western blot and FPLC using a heparin column. The biosynthetic activity of IGF-I products on articular chondrocytes was assayed for DNA and glycosaminoglycan that the cells produced. Results Secreted IGF-I propeptides stimulated articular chondrocyte biosynthetic activity to the same degree as mature IGF-I. Of the three IGF-I propeptides, only one, proIGF-IA, strongly bound to heparin. Interestingly, heparin binding of proIGF-IA depended on N-glycosylation at Asn92 in the EA peptide. To our knowledge, this is the first demonstration that N-glycosylation determines the binding of a heparin-binding protein to heparin. Conclusion The biosynthetic and heparin binding abilities of proIGF-IA, coupled with its generation of IGF-I, suggest that proIGF-IA may have therapeutic value for articular cartilage repair. General significance These data identify human pro-insulin-like growth factor IA as a bifunctional protein. Its combined ability to bind heparin and augment chondrocyte biosynthesis makes it a promising therapeutic agent for cartilage damage due to trauma and osteoarthritis.enPublisher Policyinsulin-like growth factorIGF-I propeptideE peptide