Delayed processing of the insulin proreceptor by hepatocytes from diabetic rats.
The effect of diabetes on insulin receptor processing was assessed in rat hepatocytes, 2-4 weeks after the induction of diabetes with streptozotocin. Isolated hepatocytes from control and diabetic rats were labelled for 30 min with [35S]methionine in methionine-free medium and chased with complete medium for 1-3 hrs. Solubilized cell extracts were immunoprecipitated with a site-specific anti-insulin receptor antibody, proteins were separated by electrophoresis and labelling quantified following autoradiography. After 1 hr chase, only the insulin proreceptor was labelled in both groups. After 3 hrs, the ratio of labelled proreceptors to labelled insulin receptors was 0.57 +/- 0.063 in controls and 1.33 +/- 0.24 in hepatocytes from diabetic rats. Insulin added in vitro did not affect transit time. Delayed processing of the insulin proreceptor may reflect altered N-glycosylation and may also involve other glycoproteins.
Department of Medicine, Medical University of South Carolina, Charleston 29425-2222.
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Koh
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Robinson
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D000818:Animals; D003921:Diabetes Mellitus, Experimental / Q000378:metabolism*; D008099:Liver / Q000166:cytology / Q000378:metabolism*; D008297:Male; D011498:Protein Precursors / Q000378:metabolism*; D011499:Protein Processing, Post-Translational; D051381:Rats; D017208:Rats, Wistar; D011972:Receptor, Insulin / Q000378:metabolism*
D011498:Protein Precursors; C051512:insulin proreceptor; D011972:Receptor, Insulin