NEURONAL INSULIN-RECEPTORS IN Y79 RETINOBLASTOMA CELLS

Immunoblot analysis of Y79 cell membrane proteins indicated that Y79 i nsulin receptors (InsRs) alpha subunits had a mass of 115 kDa. Biosynt hetic studies revealed a typical transit time for InsR delivery to the Golgi (similar to 2h) and receptor processing. However, neither the p roreceptor nor the mature receptor exhibited endoglycosidase H-resista nce, consistent with a lack of N-linked glycan processing. Insulin sti mulated a rapid and transient tyrosine phosphorylation of receptor bet a subunits (95 kDa) and of IRS-1 in intact Y79 cells, whereas in vitro studies with enriched membrane glycoproteins resulted in the autophos phorylation of both InsR (95 kDa) and IGF-1-R (98k Da) beta subunits. These studies provide the first biochemical dissection of InsR structu re and function in retinoblastoma cells. (C) 1995 Academic Press, Inc.