Regulation of helicobacter pylori cagA 5′UTR variants on protein expression and virulence
10.3760/cma.j.cn431274-20241125-01747
- VernacularTitle:幽门螺杆菌 cagA 5′UTR变异对蛋白表达及毒力的调控
- Author:
Cheng ZHANG
1
;
Lili WANG
;
Mengchao YU
;
Xiaoyi LI
;
Haoyi CHEN
;
Quanjiang DONG
;
Wenli LI
Author Information
1. 山东第二医科大学医学检验学院，潍坊 261053
- Publication Type:Journal Article
- Keywords:
Helicobacter pylori;
CagA;
mRNA secondary structure;
5′UTR;
Virulence
- From:
Journal of Chinese Physician
2025;27(11):1694-1700
- CountryChina
- Language:Chinese
-
Abstract:
Objective:To analyze the effect of nucleotide sequence variants in the 5′ untranslated region (5′UTR) of Helicobacter pylori (Hp) cagA on mRNA secondary structure, as well as its regulatory role in cytotoxin-associated gene A (CagA) protein expression and bacterial virulence. Methods:The upstream nucleotide sequence of cagA was amplified by polymerase chain reaction (PCR) from 37 Hp strains, and the PCR products were sequenced. MEGA 5.0 software and RNAfold prediction software were used to analyze the nucleotide sequence variants of cagA 5′UTR and the changes in mRNA secondary structure of this region, respectively. Western blot was used to detect the expression level of CagA protein in Hp strains, and the regulatory effect of cagA 5′UTR variants on the difference in CagA protein expression was analyzed. An Hp-infected AGS cell model was established to evaluate bacterial adhesion rate; quantitative PCR (qPCR) was used to analyze the mRNA transcription levels of interleukin-8 (IL-8) and tumor necrosis factor-α (TNF-α); enzyme-linked immunosorbent assay (ELISA) was used to detect the secretion levels of IL-8 and TNF-α proteins. Results:Nucleotide sequence alignment of cagA 5′UTR from 37 Hp strains showed that sequence differences were mainly concentrated in the -53motif, -10motif, + 34motif, and + 86motif regions. mRNA secondary structure prediction analysis revealed three types based on the StemB stem-loop structure: type Ⅰ (no StemB stem-loop), type ⅡA (StemB stem-loop with 3-4 base partial pairing), and type ⅡB (StemB stem-loop with 5 base full pairing). Western blot analysis showed that the CagA protein expression level was the highest in type Ⅰ Hp strains (1.72±0.29) and the lowest in type ⅡB strains (0.81±0.26), with a statistically significant difference between the two types ( P=0.030). The adhesion rate of type Ⅰ Hp strains to AGS cells was (52.90±11.17)%, which was higher than that of type Ⅱ strains [(21.27±6.16)%]. qPCR results showed that the mRNA transcription levels of IL-8 and TNF-α in AGS cells induced by type Ⅰ Hp strains were higher than those induced by type Ⅱ strains (140.23±24.47 vs 76.16±8.76, P=0.069; 55.20±9.04 vs 21.26±6.16, P=0.036). ELISA analysis further indicated that the secretion levels of IL-8 and TNF-α proteins in AGS cells induced by type Ⅰ Hp strains were also higher than those induced by type Ⅱ strains [(344.66±62.62)pg/ml vs (302.13±66.27)pg/ml, P=0.665; (131.04±4.94)pg/ml vs (79.17±11.32)pg/ml, P=0.014]. Conclusions:The cagA 5′UTR region of Hp strains exhibits significant nucleotide sequence variants. Hp strains with no StemB stem-loop (type Ⅰ) in the mRNA secondary structure show significantly increased CagA protein expression and higher bacterial pathogenic potential.
