Differential effect of pp120 on insulin endocytosis by two variant
insulin receptor isoforms.
Calzi, Sergio Li, Curtis V. Choice, and Sonia M. Najjar.
Department of Pharmacology and Therapeutics, Medical College of
Ohio, Toledo, OH 43614
APStracts 4:0142E, 1997.
The insulin receptor is expressed as two variably spliced isoforms
that differ by the absence (isoform A) or presence (isoform B) of a
12 amino acid-sequence encoded by exon 11 at the carboxy-terminus of
the [alpha]-subunit. Co-expression of the A isoform and pp120, a
substrate of the insulin receptor tyrosine kinase, in NIH 3T3
fibroblasts increased receptors A-mediated insulin endocytosis and
degradation by 2- to 3-fold as compared to cells expressing receptors
alone. Since B is the predominant isoform in the liver and binds
insulin with lower affinity than A, we have examined the effect of
pp120 on receptors B-mediated endocytosis. In contrast to isoform A,
the effect of pp120 on isoform B-mediated insulin internalization and
degradation in stably transfected NIH 3T3 cells was minimal.
Received 27 February 1997; accepted in final form 17 June 1997.
APS Manuscript Number E91-7.
Article publication pending Am. J. Physiol. (Endocrinol. Metab.).
ISSN 1080-4757 Copyright 1997 The American Physiological Society.
Published in APStracts on 10 July 1997