Specific Entry ofHelicobacter pyloriinto Cultured Gastric Epithelial Cells via a Zipper-Like Mechanism

Abstract

Although Helicobacter pylori has generally been considered an extracellular pathogen, a number of in vitro infection experiments and biopsy examinations have shown that it is capable of occasionally entering mammalian host cells. Here, we characterized this entry process by using AGS cells as a host cell model. In gentamicin protection-invasion assays, the number of H. pylori colonies recovered was lower than that for Salmonella enterica serovar Typhimurium X22, Escherichia coli expressing InvA, and Yersinia enterocolitica YO:9 grown at 25°C but higher than that for Neisseria gonorrhoeae VP1 and Y. enterocolitica YO:9 grown at 37°C. At the ultrastructural level, the entry process was observed to occur via a zipper-like mechanism. Internalized H. pylori was bound in tight LAMP-1-containing vacuoles in close association with condensed filamentous actin and tyrosine phosphorylation signals. Wortmannin, a potent inhibitor of phosphatidylinositol 3-kinase, and calphostin C, an inhibitor of protein kinase C, both inhibited the entry of H. pylori in a sensitive and dosedependent manner; however, the level of entry was enhanced by sodium vanadate, an inhibitor of tyrosine phosphatases and ATPases. Furthermore, the cytokine tumor necrosis factor alpha antagonized the entry of H. pylori into AGS cells. Collectively, these results demonstrate that the entry of H. pylori into AGS cells occurs via a zipper-like mechanism which involves various host signal transduction events.

Intracellular Helicobacter pylori in gastric epithelial progenitors

“…Previous studies of a gastric adenocarcinoma-derived cell line revealed internalized H. pylori within Lamp1-containing vacuoles, suggesting that cellular entry may occur via zipper-like receptor-mediated endocytosis, as occurs with Yersinia pseudotuberculosis, Yersinia enterocolitica, Neisseria gonorrhoeae and Listeria monocytogenes infections (21). In the latter infections, intracellular bacteria located within vacuolar compartments use several different mechanisms to prevent maturation of host cell phagosomes (i.e., their fusion to lysosomes), including alterations in the composition of the phagosomal membrane and segregation from the endocytic pathway.…”

The Phosphoinositol-3-Kinase–Protein Kinase B/Akt Pathway Is Critical forPseudomonas aeruginosaStrain PAK Internalization

“…PI3Ks modulate many cytoskeleton-based cellular processes, including adhesion, spreading, macropinocytosis, and phagocytosis. PI3K has been shown to be necessary for the invasion of epithelial cells by several bacteria, including Listeria monocytogenes (Ireton et al, 1996), Helicobacter pylori (Kwok et al, 2002), and Escherichia coli K1 (Reddy et al, 2000).Both PtdIns(3,4)P 2 and PtdIns(3,4,5)P 3 have been shown to activate one of the main downstream targets of PI3K, the serine threonine protein kinase B (PKB), also known as Akt (Burgering and Coffer, 1995;Vanhaesebroeck and Alessi, 2000). On binding to phosphoinositides by its PH domain, Akt is recruited to the membrane where it is phosphorylated by PDK1 at threonine 473 and at serine 308, leading to activation of its kinase activity.…”

Acting on Actin During Bacterial Infection

“…Both PI3-K and PKC are required for bacterial uptake and induction of cytoskeletal rearrangements [30]. Curiously preinfection of cultured gastric cells with yersinia expressing Yop virulence factors that interfere with the same signaling events impaired phagocytosis of H. pylori [30]. Internalized H. pylori was shown to be located in tight phagosomes and in close association with condensed actin filaments and localized tyrosine phosphorylation signals.…”

“…In all cases, however, invasion of H. pylori seems to involve a typical zipper-like entry process. Both PI3-K and PKC are required for bacterial uptake and induction of cytoskeletal rearrangements [30]. Curiously preinfection of cultured gastric cells with yersinia expressing Yop virulence factors that interfere with the same signaling events impaired phagocytosis of H. pylori [30].…”