Novel Serine 176 Phosphorylation of YBX1 Activates NF-κB in Colon Cancer

Matthew Martin,Laiqing Hua,Benlian Wang,Han Wei,Lakshmi Prabhu,Antja-Voy Hartley,Guanglong Jiang,Yunlong Liu,Tao Lu

doi:10.1074/jbc.m116.740258

Matthew Martin, Laiqing Hua + Show 7 more

Open Access

https://doi.org/10.1074/jbc.m116.740258

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Abstract

Y box protein 1 (YBX1) is a well known oncoprotein that has tumor-promoting functions. YBX1 is widely considered to be an attractive therapeutic target in cancer. To develop novel therapeutics to target YBX1, it is of great importance to understand how YBX1 is finely regulated in cancer. Previously, we have shown that YBX1 could function as a tumor promoter through phosphorylation of its Ser-165 residue, leading to the activation of the NF-κB signaling pathway (1). In this study, using mass spectrometry analysis, we discovered a distinct phosphorylation site, Ser-176, on YBX1. Overexpression of the YBX1-S176A (serine-to-alanine) mutant in either HEK293 cells or colon cancer HT29 cells showed dramatically reduced NF-κB-activating ability compared with that of WT-YBX1, confirming that Ser-176 phosphorylation is critical for the activation of NF-κB by YBX1. Importantly, the mutant of Ser-176 and the previously reported Ser-165 sites regulate distinct groups of NF-κB target genes, suggesting the unique and irreplaceable function of each of these two phosphorylated serine residues. Our important findings could provide a novel cancer therapy strategy by blocking either Ser-176 or Ser-165 phosphorylation or both of YBX1 in colon cancer.

Highlights

Y box protein 1 (YBX1) is a well known oncoprotein that has tumor-promoting functions
Identification of the Novel Phosphorylation on Ser-176 of YBX1—Previously, YBX1 was shown to be phosphorylated on Ser-102 in response to insulin-like growth factor 1 (IGF1) in breast cancer cells [9, 10], and, more recently by us, on Ser-165 upon IL-1␤ treatment [1]
Phosphorylation of Ser-176 Is Important for the Activation of NF-␬B—To determine whether Ser-176 phosphorylation plays an essential role in the activation of NF-␬B, we successfully expressed the S176A mutant at a level comparable with WTYBX1 in 293 cells

Summary

Introduction

Y box protein 1 (YBX1) is a well known oncoprotein that has tumor-promoting functions. The mutant of Ser-176 and the previously reported Ser-165 sites regulate distinct groups of NF-␬B target genes, suggesting the unique and irreplaceable function of each of these two phosphorylated serine residues. It has been demonstrated previously that insulin-like growth factor 1 (IGF1)3 activates the PI3K/AKT pathway, leading to the phosphorylation of Ser102 on YBX1 protein and governs its nuclear translocation in breast cancer cells [8, 9].

Results

Conclusion