Genetics of cell surface receptors for bioactive polypeptides: variants of Swiss/3T3 fibroblasts resistant to a cytotoxic chimeric insulin.

Insulin crosslinked to the catalytic fragment A of diphtheria toxin has previously been shown to be cytotoxic to insulin-responsive mouse BALBc/3T3 cells but noncytotoxic to insulin-nonresponsive variant IN-2 cells [Miskimins, W. K. & Shimizu, N. (1979) Biochem. Biophys. Res. Commun. 91, 143-151]. We have now used this cytotoxic chimeric insulin to select resistant variants of Swiss/3T3 fibroblasts. Of eight resistant colonies isolated, two proved to be deficient in insulin receptor and exhibited altered morphologies and growth rates. These variants, however, retained the ability to bind and respond to epidermal growth factor. Thus, this selection technique is effective for the isolation of variants specifically related to cellular binding and processing of insulin. Such variants will be advantageous for the genetic and biochemical characterization of the mechanism of insulin's action.