Insulin-like Growth Factor-I Receptor Internalization Regulates Signaling via the Shc/Mitogen-activated Protein Kinase Pathway, but Not the Insulin Receptor Substrate-1 Pathway

Abstract

Insulin-like growth factor-I (IGF-I) receptors activate divergent signaling pathways by phosphorylating multiple cellular proteins, including insulin receptor substrate-1 (IRS-1) and the Shc proteins. Following hormone binding, IGF-I receptors cluster into clathrincoated pits and are internalized via an endocytotic mechanism. This study investigates the relationship between IGF-I receptor internalization and signaling via IRS-1 and Shc. A mutation in the C terminus of the IGF-I receptor decreased both the rate of receptor internalization and IGF-I-stimulated Shc phosphorylation by more than 50%, but did not affect IRS-1 phosphorylation. Low temperature (15°C) decreased IGF-I receptor internalization and completely inhibited Shc phosphorylation. Although receptor and IRS-1 phosphorylation were decreased in accordance with delayed binding kinetics at 15°C, the ratio of IRS-1 to receptor phosphorylation was increased more than 2-fold. Dansylcadaverine decreased receptor internalization and Shc phosphorylation, but did not change receptor or IRS-1 phosphorylation. Consistent with these findings, dansylcadaverine inhibited IGF-I-stimulated Shc-Grb2 association, mitogen-activated protein kinase phosphorylation, and p90 ribosomal S6 kinase activation, but did not affect the association of phosphatidylinositide 3-kinase with IRS-1 or activation of p70 S6 kinase. These data support the concept that Shc/mitogen-activated protein kinase pathway activation requires IGF-I receptor internalization, whereas the IRS-1 pathway is activated by both cell surface and endosomal receptors.

New mechanisms in heptahelical receptor signaling to mitogen activated protein kinase cascades

“…Thus, blocking endocytosis a ected only a subset of signaling functions carried out by the EGFR. Similar ®ndings were reported for the insulin like growth factor-1 receptor, an RTK of the insulin receptor family (Chow et al, 1998).…”

A recombinant humanized anti‐insulin‐like growth factor receptor type I antibody (h7C10) enhances the antitumor activity of vinorelbine and anti‐epidermal growth factor receptor therapy against human cancer xenografts

“…Previous studies 55,56 based in part on direct evidence and on homologies with the insulin receptor signaling pathways demonstrate that IGF-I binding initiates the migration of IGF-IR to clathrin-coated pits and the subsequent formation of early endosomes containing internalized but still active receptors. The ligand receptor complex ultimately becomes dissociated and inactivated in the acidic environment of late endosomes where ligands and receptors are sorted for degradation or recycling to the cell surface.…”

“…The ligand receptor complex ultimately becomes dissociated and inactivated in the acidic environment of late endosomes where ligands and receptors are sorted for degradation or recycling to the cell surface. 55,56 It has been shown that anti-IGF-IR antibodies such as MAB391 30 and scFvFc 49 induce a significant down-regulation of the IGF-IR compared to what observed when IGF-1 binds to its receptor. Our results demonstrate that both 7C10 and h7C10 are capable of inducing a degradation of the IGF-IR resulting consequently in its downregulation in both MCF-7 and A549 cells.…”

Inhibition of Receptor Internalization by Monodansylcadaverine Selectively Blocks p55 Tumor Necrosis Factor Receptor Death Domain Signaling

“…The enzymatic action of transglutaminase involves cross-linking of proteins by forming an isopeptide bond between a lysine residue of one protein and a glutamine residue of another protein during coated pit formation. MDC has been shown to block endocytosis of ␣ 2 -macroglobulin and many polypeptide hormones and cytokines like epidermal growth factor, hepatocyte growth factor, insulin-like growth factor-I, and IL-8 (37,38,40,43,44,58,60). MDC-mediated inhibition of transglutaminase has also been implicated in the blocking of endocytosis of vesicular stomatitis virus, Semliki Forest virus, and other types of endocytosis occurring through clathrincoated vesicles (61,62).…”