Diabetes-induced functional and structural changes in insulin receptors from rat skeletal muscle.

Abstract

The effect of diabetes on the structure and function of insulin receptors was studied in rats 7 d after streptozotocin injection, using solubilized, partially purified receptors from rat hindlimb muscles. Diabetes increased the number of insulin receptors per gram of muscle 60-70% without apparent change in insulin binding affinity. Incubation of receptors at 40C with 1y-32PIATP and insulin resulted in dose-dependent autophosphorylation of the (i-subunit on tyrosine residues; receptors from diabetic rats showed decreased base-line phosphorylation, as well as a decrease in autophosphorylation at maximally stimulating insulin concentrations. These receptors also showed diminished exogenous substrate kinase activity using histone H2b and angiotensin II as phosphoacceptors. The electrophoretic mobility (sodium dodecyl sulfate-polyacrylamide gel electrophoresis) of a subpopulation of (i-subunits derived from diabetics was slightly decreased; differences in electrophoretic mobility between controland diabetic-derived (i-subunits were enhanced by generating fragments by partial Staphylococcus aureus V8 protease digestion. Endoglycosidase-H or neuraminidase treatment increased the electrophoretic mobility of (-subunits in both groups, but only neuraminidase appeared to decrease or abolish differences in electrophoretic mobility between controls and diabetics, suggesting that excess sialidation may account, in part, for the altered mobility of diabetic derived (i-subunits. All structural and functional alterations in insulin receptors were prevented by treating diabetic rats with insulin for 60 h. Peripheral insulin resistance associated with insulinopenic diabetes may be related to modifications in insulin receptor structure, resulting in impaired signal transmission.

Effect of diabetes and fasting on GLUT-4 (muscle/fat) glucose-transporter expression in insulin-sensitive tissues. Heterogeneous response in heart, red and white muscle

“…In this regard, it should be kept in mind that insulin action relies not only on the content of cellular GLUT-4 but also on the biological activities of the insulin receptor, as well as on several post-receptor events distal to the glucose carrier itself. In this regard, it should be mentioned that streptozotocininduced diabetes leads to a marked impairment of tyrosine receptor kinase activity in skeletal muscle [51], and that fasting enhances insulin binding as assessed in the incubated muscle preparation [13,14].…”

Differential regulation of multiple hepatic protein tyrosine phosphatases in alloxan diabetic rats.

“…The 48-kD IRKD, purified from Sf9 cells after transfection with baculovirus expressing this domain, represents the intracellular domain of the insulin receptor beta subunit, lacking only eight amino acids adjacent to the transmembrane region (10 15 mM 2-mercaptoethanol, and 1 mg/ml BSA. Reactions were initiated by addition of an aliquot (50 ,l) of the preincubation mixture to each well.…”

Hepatic protein phosphotyrosine phosphatase. Dephosphorylation of insulin and epidermal growth factor receptors in normal and alloxan diabetic rats.

“…Decreased insulin receptor tyrosine kinase activity has been reported in adipocytes (13,14), erythrocytes (15), skeletal muscle (16) and liver (17) from non-insulin-dependent diabetic subjects, and adipocytes from nondiabetic, obese individuals (14). Correlative animal studies exist (18)(19)(20), although at least two studies have failed to demonstrate decreased hepatic insulin receptor kinase activity in experimental diabetes in rats (21,22). Given the reciprocal action of tyrosine kinases and phosphatases, we hypothesized that an increase in protein phosphotyrosine phosphatase (PPTPase) activity might contribute to the insulin resistance associated with decreased receptor-mediated tyrosine phosphorylation.…”