THE ROLE OF THE INSULIN-LIKE GROWTH-FACTOR BINDING-PROTEINS AND THE IGFBP PROTEASES IN MODULATING IGF ACTION

The IGFs, IGFBPs, and BP-Pr are involved in the regulation of somatic growth and cellular proliferation in vivo and in vitro. IGFs are poten t mitogenic agents-and their actions are determined by the availabilit y of free IGFs to interact with the IGF receptors. The IGFBPs are a fa mily of proteins that bind to IGFs with high affinity and specificity. IGFBPs not only regulate IGF bioavailability but also seem to have th eir own receptors that mediate IGF-independent actions. The cleavage o f IGFBPs by specific proteases have a key role in modulation-free IGF and IGFBP levels and actions.