Insulin-receptor biosynthesis in cultured lymphocytes from an insulin-resistant patient (Rabson-Mendenhall syndrome). Evidence for defect before insertion of receptor into plasma membrane.

Abstract

In some patients with genetic forms of extreme insulin resistance, there is a marked decrease in the number of insulin receptors on the cell surface. We studied an insulin-resistant patient (RM-1) with the Rabson-Mendenhall syndrome. As judged by insulin-binding studies, Epstein-Barr virus-transformed lymphocytes from patient RM-1 exhibit a 90% decrease in the number of insulin receptors. Similarly, with either lactoperoxidase-catalyzed radioiodination of cell surface receptors or biosynthetic labeling of receptors with [3H]glucosamine, we demonstrated an 80-90% decrease in the number of insulin receptors in cells from patient RM-1. Previous studies have shown that the marked decrease in insulin receptors of the Rabson-Mendenhall patient is not due to accelerated receptor degradation. Therefore, we investigated the possibility that a slow rate of receptor biosynthesis might account for the 90% reduction of insulin receptors in cells from this patient. Insulin-receptor biosynthesis proceeds through a glycoprotein precursor with an apparent Mr of 190,000. It undergoes endopeptidase cleavage and further posttranslational processing to yield the mature 135,000- and 95,000-Mr glycoprotein subunits. We studied the biosynthesis of the 190,000-Mr precursor and mature receptor subunits by a pulse-chase labeling technique with [2-3H]mannose. The time course of insulin-receptor biosynthesis appeared normal in cells from patient RM-1, despite a 10-fold reduction in the number of receptors on the cell surface. Parallel pulse-chase experiments with either [2-3H]mannose or [35S]methionine yielded the same results regardless of which label was employed. Thus, the receptor precursor in the Rabson-Mendenhall patient seems to be synthesized at a normal rat.(ABSTRACT TRUNCATED AT 250 WORDS)

• Authors: V Y Moncada, J A Hedo, M Serrano-Rios, S I Taylor
• Journal: Diabetes (Diabetes) Vol. 35 Issue 7 Pg. 802-7 (Jul 1986) ISSN: 0012-1797 [Print] United States
• PMID: 3721065 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Protein Precursors
• Methionine
• Receptor, Insulin
• Mannose

Topics

• Cell Membrane (metabolism)
• Cells, Cultured
• Humans
• Insulin Resistance
• Lymphocytes (metabolism)
• Mannose (metabolism)
• Methionine (metabolism)
• Protein Precursors (metabolism)
• Radioligand Assay
• Receptor, Insulin (biosynthesis)
• Syndrome