Abstract
Helicobacter pylori infection is a leading cause of ulcers and gastric cancer. We show that expression of the H. pylori virulence factor CagA in a model Drosophila melanogaster epithelium induces morphological disruptions including ectopic furrowing. We find that CagA alters the distribution and increases the levels of activated myosin regulatory light chain (MLC), a key regulator of epithelial integrity. Reducing MLC activity suppresses CagA-induced disruptions. A CagA mutant lacking EPIYA motifs (CagAEPISA) induces less epithelial disruption and is not targeted to apical foci like wild-type CagA. In a cell culture model in which CagAEPISA and CagA have equivalent subcellular localization, CagAEPISA is equally potent in activating MLC. Therefore, in our transgenic system, CagA is targeted by EPIYA motifs to a specific apical region of the epithelium where it efficiently activates MLC to disrupt epithelial integrity.
Highlights
Helicobacter pylori is a Gram-negative bacterium that is estimated to infect over half the world’s population [1,2,3,4]
We showed that wild-type CagA and a CagA mutant lacking the EPIYA motifs are potent in inducing myosin regulatory light chain (MLC) redistribution in a cell type in which their subcellular localization patterns are equivalent, leading us to conclude that targeting of CagA to the apical domain is critical for efficient activation of MLC and subsequent epithelial disruption in the larval eye epithelium
CagA expression induces rapid epithelial disruption Previous work in our lab showed that expression of CagA using the eye specific Gal4 line, GMR-Gal4, caused an adult ‘‘rough’’ eye phenotype [17], suggesting that CagA interferes with the processes required for the integrity of the eye epithelium
Summary
Helicobacter pylori is a Gram-negative bacterium that is estimated to infect over half the world’s population [1,2,3,4]. Virulent strains of the bacterium contain a genetic element called the CagA pathogenicity island (CagA PAI), which encodes components of a Type IV secretion system and the virulence factor, CagA [5]. CagA does not share homology with any known proteins, and its mechanism of action has remained poorly understood. Much of what is known about CagA is through cell culture studies. Using cultured human gastric cells, it was shown that CagA is inserted into host cells through a type IV secretion system, and once inside the cell it is phosphorylated by Src kinases at tyrosines within repeated EPIYA motifs [5]. Phosphorylated CagA, in turn, ectopically activates the tyrosine phosphatase, SHP-2, a well-characterized protooncogene [3,5]
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