The high affinity insulin receptor mediates growth stimulation in rat hepatoma cells.

Insulin and insulin-like growth factor (IGF) I1 independently are potent stimulators of H-35 rat hepatoma cell proliferation.To determine which receptor species mediates this effect, the growth factor receptors present in H-35 cells were identified by affinity labeling with the corresponding '2%labeled ligands and disuccinimidyl suberate.The native insulin receptor in H-35 cells consists of a disulfide-linked (a& receptor structure typical of insulin receptors in other systems.1251-IGF-I1 interacts with a M, = 230,000 membrane polypeptide in H-35 cells similar to the IGF-I1 receptor affinity labeled in other cell types.A growth factor receptor with a subunit structure similar to the insulin receptor and displaying high affinity for IGF-I and lower affinity for IGF-II and insulin in other cell types is not detectable in H-35 cells.The half-maximal and maximal effects of insulin on cell proliferation are observed a t 0.1 n~ and 10 nM insulin, respectively.Insulin binds to the ( a f i ) ~ insulin receptor in H-35 with a K d = 4.8-13 nM.We conclude that this insulin receptor structure in H-35 cells does mediate the stimulation of cell proliferation by insulin.IGF-I1 is 0.1 to 1.0% as potent as insulin in both competing with 1251-insulin for binding to the insulin receptor and promoting growth of H-35 cells, suggesting that at least part of the growth stimulatory activity of IGF-I1 in H-35 cells is mediated through the insulin receptor.The M, = 230,000 IGF-I1 receptor in H-35 cells binds to IGF-I1 with a Kd = 12 n~ and may be involved in the stimulation of cell growth by this factor.In intact H-35 cells, insulin induces a rapid increase in the affinity of the IGF-I1 receptor for IGF-11.This effect is half-maximal at 10"' M insulin and is not observed in isolated H-35 membranes.These data indicate that insulin regulates the affinity of the IGF-I1 receptor as well as cell proliferation through the disulfide-linked heterotetrameric insulin receptor structure in H-35 hepatoma cells.Cell lines derived from rat hepatoma are unusual in that they grow in response to physiological concentrations of insulin (1).The ability of insulin to promote cell growth in other cell types is relatively poor when compared to its potency as a rapid stimulator of sugar transport and other metabolic processes.Thus, the concentrations of insulin that support growth of human skin fibroblasts (2) or chick embryo fibro-