Neuronal insulin receptors in Y79 retinoblastoma cells.

Immunoblot analysis of Y79 cell membrane proteins indicated that Y79 insulin receptors (InsRs) alpha subunits had a mass of 115 kDa. Biosynthetic studies revealed a typical transit time for InsR delivery to the Golgi (approximately 2h) and receptor processing. However, neither the proreceptor nor the mature receptor exhibited endoglycosidase H-resistance, consistent with a lack of N-linked glycan processing. Insulin stimulated a rapid and transient tyrosine phosphorylation of receptor beta subunits (95 kDa) and of IRS-1 in intact Y79 cells, whereas in vitro studies with enriched membrane glycoproteins resulted in the autophosphorylation of both InsR (95 kDa) and IGF-1-R (98k Da) beta subunits. These studies provide the first biochemical dissection of InsR structure and function in retinoblastoma cells.