Shunichi Shimasaki (Whittier Institute for Diabetes and Endocrinology, La Jolla, Calif.): "There are two types of insulin-like growth factors: IGF-I and IGF-II, which act on a wide variety of target cells to regulate growth and cytodifferentiation. The IGF ligands interact with plasma membrane receptors, and the interactions are transduced into signals that evoke the biological responses. Physiologically, most of the IGFs do not exist as free ligands, but rather are bound to specific proteins called the IGF-binding proteins (IGFBPs). At present, the precise function of the IGFBPs is unknown. However, there is an increasing body of evidence demonstrating that the IGFBPs can modulate--either enhance or suppress--the biological responses of the IGF ligands. Thus, the `concept is emerging that the IGFBPs may play a pivotal role in determining the cellular responses to IGF-I and IGF-II.
"As described in this paper, we undertook a comprehensive purification scheme to isolate all of the ...
