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Helicobacter pylori CagA protein targets the c-Met receptor and enhances the motogenic response.

Churin Y, Al-Ghoul L, Kepp O, Meyer TF, Birchmeier W, Naumann M - J. Cell Biol. (2003)

Bottom Line: The H. pylori effector protein CagA intracellularly targets the c-Met receptor and promotes cellular processes leading to a forceful motogenic response.CagA could represent a bacterial adaptor protein that associates with phospholipase Cgamma but not Grb2-associated binder 1 or growth factor receptor-bound protein 2.The activation of the motogenic response in H. pylori-infected epithelial cells suggests that CagA could be involved in tumor progression.

View Article: PubMed Central - PubMed

Affiliation: Institute of Experimental Internal Medicine, Medical Faculty, Otto-von-Guericke-University, Leipziger Strasse 44, 39120 Magdeburg, Germany.

ABSTRACT
Infection with the human microbial pathogen Helicobacter pylori is assumed to lead to invasive gastric cancer. We find that H. pylori activates the hepatocyte growth factor/scatter factor receptor c-Met, which is involved in invasive growth of tumor cells. The H. pylori effector protein CagA intracellularly targets the c-Met receptor and promotes cellular processes leading to a forceful motogenic response. CagA could represent a bacterial adaptor protein that associates with phospholipase Cgamma but not Grb2-associated binder 1 or growth factor receptor-bound protein 2. The H. pylori-induced motogenic response is suppressed and blocked by the inhibition of PLCgamma and of MAPK, respectively. Thus, upon translocation, CagA modulates cellular functions by deregulating c-Met receptor signaling. The activation of the motogenic response in H. pylori-infected epithelial cells suggests that CagA could be involved in tumor progression.

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H. pylori–induced motogenic response requires ERK activity. (A) H. pylori induces PI3-K–dependent PKB phosphorylation. AGS cells were pretreated with inhibitor of PI3-K (Ly) and infected with H. pylori. Total cell lysates were prepared at the indicated time points after infection and analyzed by Western blot analysis using phospho-PKB (Ser473) antibody. (B) Inhibitor of PI3-K fails to suppress the motogenic response of AGS cells after H. pylori infection. AGS cells were pretreated with Ly294002 and infected with H. pylori. Phase-contrast microscopy was performed at 4 h after infection. (C) Pretreatment of AGS cells with MAPK/extracellular regulated kinase (MEK) inhibitor PD98059 inhibits ERK1/2 activation by H. pylori. AGS cells were pretreated with or without PD98059 and infected with H. pylori. Total cell lysates were prepared at the indicated time points after infection and analyzed by Western blot analysis using phospho-p44/42 MAPK antibody. (D) Treatment with the MEK inhibitor PD98059 blocks the motogenic response in AGS cells. AGS cells were pretreated with the MEK inhibitor PD98059 and infected with H. pylori. Phase-contrast microscopy was performed 4 h after infection.
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fig5: H. pylori–induced motogenic response requires ERK activity. (A) H. pylori induces PI3-K–dependent PKB phosphorylation. AGS cells were pretreated with inhibitor of PI3-K (Ly) and infected with H. pylori. Total cell lysates were prepared at the indicated time points after infection and analyzed by Western blot analysis using phospho-PKB (Ser473) antibody. (B) Inhibitor of PI3-K fails to suppress the motogenic response of AGS cells after H. pylori infection. AGS cells were pretreated with Ly294002 and infected with H. pylori. Phase-contrast microscopy was performed at 4 h after infection. (C) Pretreatment of AGS cells with MAPK/extracellular regulated kinase (MEK) inhibitor PD98059 inhibits ERK1/2 activation by H. pylori. AGS cells were pretreated with or without PD98059 and infected with H. pylori. Total cell lysates were prepared at the indicated time points after infection and analyzed by Western blot analysis using phospho-p44/42 MAPK antibody. (D) Treatment with the MEK inhibitor PD98059 blocks the motogenic response in AGS cells. AGS cells were pretreated with the MEK inhibitor PD98059 and infected with H. pylori. Phase-contrast microscopy was performed 4 h after infection.

Mentions: The dual protein/phospholipid kinase PI3-K has been shown to be activated during growth factor signaling (Comoglio and Boccaccio, 2001; Kassis et al., 2001). Therefore, we tested next whether PI3-K is involved in stimulation of cell motility by H. pylori. AGS cells were treated with Ly294002, an inhibitor of PI3-K before infection with H. pylori. We assayed the activity of PI3-K by monitoring the phosphorylation state of the PI3-K downstream target protein kinase B (PKB). Recruitment of this serine-threonine kinase to the cellular membrane and subsequent phosphorylation at Thr308 and Ser473 residues is dependent on the production of the PI3-K lipid product, PIP3 (Marte and Downward, 1997). H. pylori infection activated PI3-K in AGS cells and Ly294002 strongly inhibited the PI3-K activation (Fig. 5 A). However, in spite of the presence of the PI3-K inhibitor, AGS cells were motile (Fig. 5 B). These observations indicated that the induction of AGS motogenic response by H. pylori is independent of PI3-K. In contrast to AGS and HeLa cells, MDCK cells treated with a specific PI3-K inhibitor and infected with H. pylori does not show scattering (unpublished data). AGS and HeLa cells are gastric and cervix cancer cell lines, whereas MDCK cells represent polarized primary canine kidney cells, thus, the observed difference in PI3-K requirement is due to cell type specificity.


Helicobacter pylori CagA protein targets the c-Met receptor and enhances the motogenic response.

Churin Y, Al-Ghoul L, Kepp O, Meyer TF, Birchmeier W, Naumann M - J. Cell Biol. (2003)

H. pylori–induced motogenic response requires ERK activity. (A) H. pylori induces PI3-K–dependent PKB phosphorylation. AGS cells were pretreated with inhibitor of PI3-K (Ly) and infected with H. pylori. Total cell lysates were prepared at the indicated time points after infection and analyzed by Western blot analysis using phospho-PKB (Ser473) antibody. (B) Inhibitor of PI3-K fails to suppress the motogenic response of AGS cells after H. pylori infection. AGS cells were pretreated with Ly294002 and infected with H. pylori. Phase-contrast microscopy was performed at 4 h after infection. (C) Pretreatment of AGS cells with MAPK/extracellular regulated kinase (MEK) inhibitor PD98059 inhibits ERK1/2 activation by H. pylori. AGS cells were pretreated with or without PD98059 and infected with H. pylori. Total cell lysates were prepared at the indicated time points after infection and analyzed by Western blot analysis using phospho-p44/42 MAPK antibody. (D) Treatment with the MEK inhibitor PD98059 blocks the motogenic response in AGS cells. AGS cells were pretreated with the MEK inhibitor PD98059 and infected with H. pylori. Phase-contrast microscopy was performed 4 h after infection.
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fig5: H. pylori–induced motogenic response requires ERK activity. (A) H. pylori induces PI3-K–dependent PKB phosphorylation. AGS cells were pretreated with inhibitor of PI3-K (Ly) and infected with H. pylori. Total cell lysates were prepared at the indicated time points after infection and analyzed by Western blot analysis using phospho-PKB (Ser473) antibody. (B) Inhibitor of PI3-K fails to suppress the motogenic response of AGS cells after H. pylori infection. AGS cells were pretreated with Ly294002 and infected with H. pylori. Phase-contrast microscopy was performed at 4 h after infection. (C) Pretreatment of AGS cells with MAPK/extracellular regulated kinase (MEK) inhibitor PD98059 inhibits ERK1/2 activation by H. pylori. AGS cells were pretreated with or without PD98059 and infected with H. pylori. Total cell lysates were prepared at the indicated time points after infection and analyzed by Western blot analysis using phospho-p44/42 MAPK antibody. (D) Treatment with the MEK inhibitor PD98059 blocks the motogenic response in AGS cells. AGS cells were pretreated with the MEK inhibitor PD98059 and infected with H. pylori. Phase-contrast microscopy was performed 4 h after infection.
Mentions: The dual protein/phospholipid kinase PI3-K has been shown to be activated during growth factor signaling (Comoglio and Boccaccio, 2001; Kassis et al., 2001). Therefore, we tested next whether PI3-K is involved in stimulation of cell motility by H. pylori. AGS cells were treated with Ly294002, an inhibitor of PI3-K before infection with H. pylori. We assayed the activity of PI3-K by monitoring the phosphorylation state of the PI3-K downstream target protein kinase B (PKB). Recruitment of this serine-threonine kinase to the cellular membrane and subsequent phosphorylation at Thr308 and Ser473 residues is dependent on the production of the PI3-K lipid product, PIP3 (Marte and Downward, 1997). H. pylori infection activated PI3-K in AGS cells and Ly294002 strongly inhibited the PI3-K activation (Fig. 5 A). However, in spite of the presence of the PI3-K inhibitor, AGS cells were motile (Fig. 5 B). These observations indicated that the induction of AGS motogenic response by H. pylori is independent of PI3-K. In contrast to AGS and HeLa cells, MDCK cells treated with a specific PI3-K inhibitor and infected with H. pylori does not show scattering (unpublished data). AGS and HeLa cells are gastric and cervix cancer cell lines, whereas MDCK cells represent polarized primary canine kidney cells, thus, the observed difference in PI3-K requirement is due to cell type specificity.

Bottom Line: The H. pylori effector protein CagA intracellularly targets the c-Met receptor and promotes cellular processes leading to a forceful motogenic response.CagA could represent a bacterial adaptor protein that associates with phospholipase Cgamma but not Grb2-associated binder 1 or growth factor receptor-bound protein 2.The activation of the motogenic response in H. pylori-infected epithelial cells suggests that CagA could be involved in tumor progression.

View Article: PubMed Central - PubMed

Affiliation: Institute of Experimental Internal Medicine, Medical Faculty, Otto-von-Guericke-University, Leipziger Strasse 44, 39120 Magdeburg, Germany.

ABSTRACT
Infection with the human microbial pathogen Helicobacter pylori is assumed to lead to invasive gastric cancer. We find that H. pylori activates the hepatocyte growth factor/scatter factor receptor c-Met, which is involved in invasive growth of tumor cells. The H. pylori effector protein CagA intracellularly targets the c-Met receptor and promotes cellular processes leading to a forceful motogenic response. CagA could represent a bacterial adaptor protein that associates with phospholipase Cgamma but not Grb2-associated binder 1 or growth factor receptor-bound protein 2. The H. pylori-induced motogenic response is suppressed and blocked by the inhibition of PLCgamma and of MAPK, respectively. Thus, upon translocation, CagA modulates cellular functions by deregulating c-Met receptor signaling. The activation of the motogenic response in H. pylori-infected epithelial cells suggests that CagA could be involved in tumor progression.

Show MeSH
Related in: MedlinePlus