alphaPix interacts with Helicobacter pylori CagA to induce IL-8 expression in gastric epithelial cells.
OBJECTIVE
Helicobacter pylori CagA, translocated into gastric epithelial cells, induces IL-8 expression through the signalling pathways, including extracellular signal-regulated kinase (ERK) and nuclear factor-kappaB (NF-kappaB). We previously demonstrated that CagA interacts with host alphaPix. The present study was purposed to determine the role of the interaction of alphaPix with CagA on the signalling pathways for IL-8 expression in H. pylori-infected gastric epithelial cells.


METHODS
H. pylori HP99 strain (CagA+, VacA+) was infected to gastric epithelial AGS cells transfected with non-targeting (NT) or alphaPix- targeting siRNA. Activation of signalling molecules including p21-activated kinase (PAK), ERK and NF-kappaB, and expression of IL-8 in the cells were assessed.


RESULTS
H. pylori CagA was delivered into AGS cells and then interacted with alphaPix at 4 h following H. pylori infection. PAK1, ERK and NF-kappaB were activated in the cells containing NT and alphaPix siRNA at 1-2 h following H. pylori infection. However, after 4 h, the time when CagA was delivered into the cells, the activations of PAK1, ERK and NF-kappaB were inhibited by down-regulation of alphaPix using siRNA but not by NT siRNA. The results indicate that alphaPix is required for H. pylori-mediated signalling of PAK1, ERK and NF-kappaB. Additionally, alphaPix siRNA suppressed IL-8 induction after translocation of CagA into the cells, indicating that interaction of CagA with alphaPix is critical for CagA-mediating signalling for IL-8 expression.


CONCLUSIONS
The interaction of alphaPix with CagA activates PAK1, ERK and NF-kappaB, which induces IL-8 expression in H. pylori-infected gastric epithelial cells.
Lim
Joo Weon
JW
Institute of Gastroenterology, Brain Korea 21 Project for Medical Science, Yonsei University College of Medicine, Seoul, Korea.
Kim
Kyung Hwan
KH
Kim
Hyeyoung
H
D000942:Antigens, Bacterial / Q000378:metabolism*; D001426:Bacterial Proteins / Q000378:metabolism*; D004847:Epithelial Cells / Q000378:metabolism* / Q000382:microbiology; D048049:Extracellular Signal-Regulated MAP Kinases / Q000096:biosynthesis; D005753:Gastric Mucosa / Q000378:metabolism*; D020662:Guanine Nucleotide Exchange Factors / Q000378:metabolism*; D016481:Helicobacter Infections / Q000378:metabolism*; D006801:Humans; D016209:Interleukin-8 / Q000096:biosynthesis*; D016328:NF-kappa B / Q000096:biosynthesis; D064067:Rho Guanine Nucleotide Exchange Factors; D015398:Signal Transduction; D054462:p21-Activated Kinases / Q000096:biosynthesis
D000942:Antigens, Bacterial; D001426:Bacterial Proteins; D020662:Guanine Nucleotide Exchange Factors; D016209:Interleukin-8; D016328:NF-kappa B; D064067:Rho Guanine Nucleotide Exchange Factors; C080866:cagA protein, Helicobacter pylori; D054462:p21-Activated Kinases; D048049:Extracellular Signal-Regulated MAP Kinases