PMID: 6411700Aug 25, 1983Paper

Biosynthesis and glycosylation of the insulin receptor. Evidence for a single polypeptide precursor of the two major subunits.

The Journal of Biological Chemistry
J A HedoM Kasuga

Abstract

The biosynthesis and carbohydrate processing of the insulin receptor were studied in cultured human lymphocytes by means of metabolic and cell surface labeling, immunoprecipitation with anti-receptor autoantibodies, and analysis on sodium dodecyl sulfate-polyacrylamide gels under reducing conditions. In addition to the two major subunits of Mr = 135,000 and Mr = 95,000, two higher molecular weight bands were detected of Mr = 210,000 and Mr = 190,000. The Mr = 210,000 band and the two major subunits were labeled by [3H]mannose, [3H]glucosamine, [3H]galactose, and [3H]fucose, and were bound by immobilized lentil, wheat germ, and ricin I lectins. On the other hand, the Mr = 190,000 band was labeled only by [3H]mannose and [3H]glucosamine and was bound only by lentil lectin. All four components could be labeled with [35S] methionine; however, in contrast with the other three polypeptides, the Mr = 190,000 band was not labeled by cell surface iodination with lactoperoxidase, suggesting that it is not exposed at the outer surface of the plasma membrane. Pulse-chase studies with [3H]mannose showed that the Mr = 190,000 was the earliest labeled component of the receptor; radioactivity in this band reached a maximum 1 h after the pulse,...Continue Reading

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