Insulinlike growth factor-binding protein proteolysis - An emerging paradigm in insulinlike growth factor physiology

In biologic fluids, insulinlike growth factors (IGF-I and IGF-II) ave bound to high-affinity insulinlike growth factor binding proteins (IGFBPs), of which seven have now been identified (IGFBPs 1-7). In a variety of biologic fluids, several IGFBPs undergo proteolytic degradation. Such degradation can lead to increased IGF bioavailability at the cell surface, facilitating receptor interactions. Herein, recent data identifying several IGFBP-degrading proteinases and their effects on IGF bioactivity is reviewed, and how IGFBP proteolysis is regulated by IGFs and IGFBPs, as well as how IGFBP cleavage analysis provides insights into the structure and function of IGFBPs, is explored. (C) 1997, Elsevier Science Inc.