New roles for IGF binding proteins

The insulin-like growth factors (IGFs), IGF binding proteins (IGFBPs), and IGFBP proteases regulate somatic growth and cellular proliferation both in vivo and in vitro. IGFs are potent mitogens whose actions are determined by the availability of free IGFs to interact with IGF receptors. IGFBPs compr ise a family of six proteins that bind IGFs with high affinity and specific ity and thereby regulate IGF-dependent actions. IGFBPs have recently emerge d as IGF-independent regulators of cell growth. Cleavage of IGFBPs by speci fic proteases modulate levels of free IGFs and IGFBPs and, thereby, their a ctions. IGFBP-related proteins bind IGFs with low affinity and also play im portant roles in cell growth and differentiation. Future research on IGF ax is physiology promises exciting insights into cell biology, as well as ther apies for diseases such as cancer, asthma, and diabetes mellitus.