A novel NOD1- and CagA-independent pathway of interleukin-8 induction mediated by the Helicobacter pylori type IV secretion system

Rebecca J Gorrell, Jye Swei Guan, Yue Xin, Mona Anoushiravani Tafreshi, Melanie L Hutton, Michael A McGuckin, Richard L Ferrero, Terry Kwok

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The type IV secretion system (T4SS) of Helicobacter pylori triggers massive inflammatory responses during gastric infection by mechanisms that are poorly understood. Here we provide evidence for a novel pathway by which the T4SS structural component, CagL, induces secretion of interleukin-8 (IL-8) independently of CagA translocation and peptidoglycan-sensing nucleotide-binding oligomerization domain 1 (NOD1) signalling. Recombinant CagL was sufficient to trigger IL-8 secretion, requiring activation of alpha(5) beta(1) integrin and the arginine-glycine-aspartate (RGD) motif in CagL. Mutation of the encoded RGD motif to arginine-glycine-alanine (RGA) in the cagL gene of H. pylori abrogated its ability to induce IL-8. Comparison of IL-8 induction between H. pylori DeltavirD4 strains bearing wild-type or mutant cagL indicates that CagL-dependent IL-8 induction can occur independently of CagA translocation. In line with this notion, exogenous CagL complemented H. pylori DeltacagL mutant in activating NF-kappaB and inducing IL-8 without restoring CagA translocation. The CagA translocation-independent, CagL-dependent IL-8 induction involved host signalling via integrin alpha(5) beta(1) , Src kinase, the mitogen-activated protein kinase (MAPK) pathway and NF-kappaB but was independent of NOD1. Our findings reveal a novel pathway whereby CagL, via interaction with host integrins, can trigger proinflammatory responses independently of CagA translocation or NOD1 signalling.
Original languageEnglish
Pages (from-to)554 - 570
Number of pages17
JournalCellular Microbiology
Issue number4
Publication statusPublished - 2013

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