Insulin causes insulin-receptor internalization in human erythrocyte ghosts

Abstract

The effect of incubation with insulin on insulin-receptor internalization by erythrocyte ghosts was investigated. The number of surface insulin receptors decreased by 30-40% after incubation of ghosts with insulin. Total insulin-receptor binding to solubilized ghosts was the same in insulin-incubated and control ghosts, whereas insulin binding to an internal vesicular fraction was substantially increased in insulin-incubated ghosts. Our findings suggest that erythrocyte-ghost insulin receptors are internalized to a vesicular compartment in response to incubation with insulin.

Insulin-induced lipid binding to hemoglobin

“…In this regard, these findings support previous suggestions that internalized insulin receptors are present in inside-out vesicles. 19 Accordingly, at the leaflet facing the cytoplasm, PS and PE will be exposed, as these lipids are predominantly restricted to the inner leaflet of the erythrocyte membrane. Since C 6 -NBD-PC is not found associated with Hb in Hb aggregates, PS, PE and cholesterol likely gain access to Hb as monomers, rather than as whole vesicles acting as nucleation sites for Hb.…”