A leucine to proline mutation at position 233 in the insulin receptor inhibits cleavage of the proreceptor and transport to the cell surface

Abstract

We have previously shown that a homozygous mutation encoding a substitution of proline for leucine at position 233 in the insulin receptor is linked with the syndrome of leprechaunism, being a lethal form of insulin resistance in newborn children. Specific binding of insulin and insulin-stimulated autophosphorylation of the insulin receptor are nearly absent in fibroblasts from the leprechaun patient. To examine the molecular basis of the observed insulin receptor abnormalities, CHO cell lines overexpressing mutant insulin receptors were made by transfection. The results show that the mutation inhibits cleavage and transport of the proreceptor from intracellular sites to the cell surface. As the mutant receptor is poorly precipitated by two different monoclonal antibodies recognizing epitopes on undenatured wild-type alpha-subunits, the mutation probably affects overall folding of the alpha-subunit. The mutant proreceptor is unable to bind insulin and exhibits no insulin-stimulated autophosphorylation. These data explain the abnormalities seen in the patient's fibroblasts. Pulse-chase labeling experiments on transfected cells show that the mutant precursor has an extended half-life (approximately 5 h) compared to the precursor of wild-type insulin receptors (approximately 2 h). This mutation is the first example of a naturally occurring mutation in the insulin receptor which completely blocks cleavage of the proreceptor and transport to the cell surface.

An arginine to cysteine252 mutation in insulin receptors from a patient with severe insulin resistance inhibits receptor internalisation but preserves signalling events

“…But these different maturation steps proceed at a slower rate in IR R252C than in IRwt. These results are in agreement with previous studies showing that mutations in the N-terminal half of the α-subunit could impair intracellular transport [28,29,30,31,32,33]. One possible interpretation of these events is a misfolding of the protein in the endoplasmic reticulum.…”

Myotubes derived from human-induced pluripotent stem cells mirror in vivo insulin resistance

“…Both insulin and IGF1 contribute to normal muscle growth, and insulin resistance and diabetes mellitus can be associated with varying degrees of skeletal muscle atrophy and impaired satellite cell proliferation and differentiation (29). Thus, it is possible that alterations in differentiation pattern observed in the mutant lines contribute to the low muscle mass observed in children with Donohue syndrome (10)(11)(12).…”

“…C1 fibroblasts (BJ) were from ATCC; C2, C3, C4, IR-M2 and IR-M3, and IR-M4 fibroblasts were from Coriell. IR-M1 and IR-M3 fibroblasts were previously characterized (11,12). iPS cells were generated from fibroblasts by retroviral transduction of KLF4, SOX2, OCT4, and c-MYC reprogramming factors and tested for pluripotency as previously described (9).…”

“…Donohue syndrome (also called leprechaunism) is caused by homozygous or compound heterozygous mutations in the insulin receptor, resulting in a complex clinical phenotype including marked insulin resistance, failure to thrive, and early death (10)(11)(12). iPS cells derived from these patients exhibit severe insulin resistance with defects in insulin signaling, cell proliferation, and gene transcription (9,13).…”

An in-frame insertion in exon 3 and a nonsense mutation in exon 2 of the insulin receptor gene associated with severe insulin resistance in a patient with Rabson-Mendenhall syndrome

“…However, partially purified insulin receptors of PK were not autophosphorylated by incubation with IGF-I, indicating that IGF-I cannot activate the insulin receptor kinase in these cells. Several missense mutations have been characterized in the N-terminal c~-subunit of the insulin receptor which are all associated with incomplete processing and defective transport [36,[44][45][46][47][48] to the plasma membrane. Cor- Fig.6.…”