Regulation of Insulin-like Growth Factor I Receptor Dephosphorylation by SHPS-1 and the Tyrosine Phosphatase SHP-2

Laura A Maile,David R Clemmons

doi:10.1074/jbc.m109258200

Abstract

Activation of insulin-like growth factor I receptor (IGF-IR) kinase is an important site of control of IGF-I-linked intracellular signaling pathways. One potentially important regulatory variable is IGF-IR dephosphorylation. It has been shown that SHP-2, a tyrosine phosphatase, can bind to the activated IGF-IR in vitro; however, its role in IGF-IR dephosphorylation in whole cells is unknown. These studies were undertaken to determine whether SHP-2 was a candidate for mediating IGF-IR dephosphorylation. The IGF-IR in smooth muscle cells was dephosphorylated rapidly beginning 10 min after ligand addition, and this was temporally associated with SHP-2 binding to the receptor. IGF-I stimulated SHPS-1 phosphorylation and the subsequent recruitment of SHP-2. In cells expressing a SHPS-1 mutant that did not bind SHP-2 there was no recruitment of SHP-2 to the IGF-IR. Cells expressing a catalytically inactive form of SHP-2 showed SHP-2 recruitment to SHPS-1, but this did not result in SHPS-1 dephosphorylation, and there was a prolonged IGF-IR phosphorylation response after IGF-I stimulation. These studies indicate that IGF-IR stimulates phosphorylation of SHPS-1 which is critical for SHP-2 recruitment to the plasma membrane and for its recruitment to the IGF-IR. Recruitment of SHP-2 to the receptor then results in receptor dephosphorylation. The regulation of this process may be an important determinant of IGF-IR-mediated signaling.

Highlights

For sustained stimulation of insulin-like growth factor I (IGF-I)-stimulated biologic responses
After a 10-min stimulation there was detectable SHP-2 association, and at 20 min there was a marked 16 Ϯ 4.5-fold increase (n ϭ 3) in SHP-2 association with the insulin-like growth factor I receptor (IGF-IR). These results suggest that there is a correlation between the time at which the phosphorylation state of the IGF-IR is decreasing and the time at which the SHP-2 tyrosine phosphatase association increases
From the studies presented here we propose that the recruitment of SHP-2 to the IGF-IR via SHPS-1 is responsible for the decrease in IGF-IR phosphorylation after IGF-I-induced receptor activation and is an important regulator of IGF-I signaling

Summary

Introduction

For sustained stimulation of IGF-I-stimulated biologic responses. Mutation of specific tyrosines in the receptor has been shown to result in attenuation of the ability of IGF-I to stimulate DNA synthesis, cell migration, and inhibition of apoptosis [6]. After phosphorylation of two tyrosines that are contained in the intracellular domain of SHPS-1, SHP-2 is recruited from the cytoplasm to the plasma membrane, and its binding to SHPS-1 activates its phosphatase activity (18 –20) Mutation of these tyrosines in SHPS-1 results in the failure of SHP-2 to be recruited to the membrane [21]. The recruitment of SHP-2 to SHPS-1 has been shown to correlate with the negative effect of SHPS-1 on insulin signaling [19], and in the case of the GH receptor, loss of SHP-2 recruitment to SHPS-1 has been shown to result in prolonged GH receptor phosphorylation [22] Based on these prior observations, we attempted to determine whether SHP-2 dephospho-. IGF-I Receptor Dephosphorylation rylates the IGF-IR after IGF-I-induced receptor activation, to identify the role of SHPS-1 in recruitment of SHP-2 to the activated receptor, and to determine the consequences of blocking this recruitment using mutagenesis

Methods

Results

Conclusion