Helicobacter pylori infection induces STAT3 phosphorylation on Ser727 and autophagy in human gastric epithelial cells and mouse stomach

Hyeong-Jun Han,Do-Hee Kim,Sin-Aye Park,Nayoung Kim,Kichul Yoon,Ki Baik Hahm,Juan-Yu Piao,Su-Jung Kim,Ha-Na Lee,Hye-Kyung Na,Ji Hyun Park,Young-Joon Surh

doi:10.1038/s41598-020-72594-3

Abstract

Helicobacter pylori (H. pylori) infection is considered as one of the principal risk factors of gastric cancer. Constitutive activation of the signal transducer and activator of transcription 3 (STAT3) plays an important role in inflammation-associated gastric carcinogenesis. In the canonical STAT3 pathway, phosphorylation of STAT3 on Tyr705 is a major event of STAT3 activation. However, recent studies have demonstrated that STAT3 phosphorylated on Ser727 has an independent function in mitochondria. In the present study, we found that human gastric epithelial AGS cells infected with H. pylori resulted in localization of STAT3 phosphorylated on Ser727 (P-STAT3Ser727), predominantly in the mitochondria. Notably, H. pylori-infected AGS cells exhibited the loss of mitochondrial integrity and increased expression of the microtubule-associated protein light chain 3 (LC3), the autophagosomal membrane-associated protein. Treatment of AGS cells with a mitophagy inducer, carbonyl cyanide 3-chlorophenylhydrazone (CCCP), resulted in accumulation of P-STAT3Ser727 in mitochondria. In addition, the elevated expression and mitochondrial localization of LC3 induced by H. pylori infection were attenuated in AGS cells harboring STAT3 mutation defective in Ser727 phosphorylation (S727A). We also observed that both P-STAT3Ser727 expression and LC3 accumulation were increased in the mitochondria of H. pylori-inoculated mouse stomach.

Highlights

Helicobacter pylori (H. pylori) infection is considered as one of the principal risk factors of gastric cancer
signal transducer and activator of transcription 3 (STAT3) is a transcription factor activated by various external stimuli including cytokines and growth factors
STAT3 is phosphorylated on Tyr[705] and translocates to nucleus where it regulates expression of target genes involved in cell proliferation, survival and so o n1,3,5–7,22

Summary

Introduction

Helicobacter pylori (H. pylori) infection is considered as one of the principal risk factors of gastric cancer. We found that human gastric epithelial AGS cells infected with H. pylori resulted in localization of STAT3 phosphorylated on Ser[727] (P-STAT3Ser727), predominantly in the mitochondria. The elevated expression and mitochondrial localization of LC3 induced by H. pylori infection were attenuated in AGS cells harboring STAT3 mutation defective in Ser[727] phosphorylation (S727A). It is well known that the signal transducer and activator of transcription 3 (STAT3) functions as a nuclear transcription factor to regulate expression of target genes involved in cell proliferation, survival and t ransformation[1]. Our previous study demonstrated that H. pylori infection induced phosphorylation and nuclear translocation of STAT3 in cultured human gastric AGS cells and mouse stomach in vivo[7]. The Ser[727] phosphorylation of STAT3 is associated with negative estrogen receptor status in infiltrating breast ductal c arcinoma[11], and progression of cervical intraepithelial neoplasia[12]

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