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			PubMed Journals: Diabetes

  Source:		PMID: 8513978


    		Diabetes. 1993 Jul;42(7):966-74.
     
			Glycosylation of Asn397 or Asn418 is required
			for normal insulin receptor biosynthesis and
			processing.

			Bastian W(1), Zhu J, Way B, Lockwood D,
			Livingston J.

			Author Information
			(1) University of Rochester Medical Center,
			Department of Medicine, New York.

			Two N-linked sites of glycosylation in the
			insulin receptor were examined for their
			contribution to insulin binding, tyrosine
			kinase activity, and receptor biosynthesis. Asn397
			and Asn418 were replaced by Gln using site-directed
			mutagenesis either as single mutations,
			i.e., Q-397 and Q-418, or as a double mutation
			in which both sites were removed (Q-D).
			The mutations were transiently expressed
			in COS cells and the findings compared with
			cells that transiently expressed the wild-type
			human insulin receptor. Q-397 and Q-418
			mutant insulin receptors had insulin-binding
			characteristics similar to the wild-type
			human insulin receptor, whereas no insulin-binding
			activity could be detected above the control
			level in cells transfected with Q-D. Flow
			cytometry with antibodies against the human
			insulin receptor indicated the presence
			of Q-397, Q-418, and wild-type human insulin
			receptors in the surface of COS cells and
			failed to demonstrate a Q-D receptor.
			Insulin-induced autophosphorylation was
			similar in Q-397, Q-418, and wild-type human
			insulin receptors as was their ability to
			phosphorylate an artificial substrate, poly
			Glu-Tyr (4:1). Our inability to detect Q-D
			receptors was not caused by a lack of Q-D
			mRNA. COS cells transfected with Q-D cDNA
			generated as much Q-D mRNA as the amount
			of wild-type human insulin receptor mRNA
			present in cells transfected with wild-type
			receptor cDNA. Finally, pulse-chase experiments
			with [35S]Met were able to detect 190,000-M(r)
			proreceptors and the alpha-subunits for
			Q-397, Q-418, and wild-type human insulin
			receptors.(ABSTRACT TRUNCATED AT 250 WORDS)

			PMID: 8513978 [Indexed for MEDLINE]

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