The E3 Ligase TRAF4 Promotes Igf Signaling by Mediating Atypical Ubiquitination of IRS-1

Authors

Wenjuan Yu
Ramesh Singh
Zhao Wang
Bert W O'Malley
Ping Yi

Publication Date

1-1-2021

Journal

Journal of Biological Chemistry

DOI

10.1016/j.jbc.2021.100739

PMID

33991522

PMCID

PMC8191236

PubMedCentral® Posted Date

5-13-2021

PubMedCentral® Full Text Version

Post-print

Published Open-Access

yes

Keywords

HEK293 Cells, Humans, Insulin Receptor Substrate Proteins, Insulin-Like Growth Factor I, MCF-7 Cells, Signal Transduction, TNF Receptor-Associated Factor 4, Ubiquitination, ubiquitination, insulin receptor substrate 1 (IRS-1), insulin-like growth factor (IGF), TNF receptor associated factor (TRAF), protein phosphorylation, proliferation, Akt

Abstract

Insulin-like growth factor (IGF) is a potent mitogen that activates the IGF receptor (IGFR)/insulin receptor substrate (IRS) axis, thus stimulating growth in normal cells and uncontrolled cell proliferation in cancer. Posttranslational modifications of IRS such as ubiquitination tightly control IGF signaling, and we previously identified IRS-1 as a potential substrate for the E3 ubiquitin ligase TRAF4 using an unbiased screen. Here we provide evidence that TRAF4-mediated ubiquitination of IRS-1 is physiologically relevant and crucial for IGF signal transduction. Through site-directed mutagenesis we found that TRAF4 promotes an atypical K29-linked ubiquitination at the C-terminal end of IRS-1. Its depletion abolishes AKT and ERK phosphorylation downstream of IGF-1 and inhibits breast cancer cell proliferation. Overexpression of TRAF4 enhances IGF1-induced IGFR-IRS-1 interaction, IRS-1 tyrosine phosphorylation, and downstream effector protein activation, whereas mutation of IRS-1 ubiquitination sites completely abolishes these effects. Altogether, our studies demonstrate that nonproteolytic ubiquitination of IRS-1 is a key step in conveying IGF-1 stimulation from IGFR to IRS-1.

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