Insulin-like growth factor binding proteins: New proteins, new functions

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 act ions. IGFBP-related proteins (IGFBP-rPs) bind IGFs with low affinity and al so play important roles in cell growth and differentiation. The GH-IGF-IGFB P axis is complex and powerful. Future research on its physiology promises exciting insights into cell biology as well as therapies for; diseases such as cancer and diabetes mellitus.