Functional role of E-cadherin in Helicobacter pylori-associated carcinogenesis

The gastric epithelium is established and maintained through intact cell-cell adhesions, a tightly regulated actin cytoskeleton and an apical-basal polarity forming effective barriers against pathogens. However, the human pathogen and class-1 carcinogen Helicobacter pylori (Hp) developed fascinating strategies to disrupt the epithelial barrier function where it induces inflammatory and neoplastic disorders in the human stomach. In-vitro, Hp mediates a strong migration of epithelial host cells which involves a drastic loss of intercellular adhesions. In our previous studies, we identified the Hp-secreted protease HtrA that directly cleaves the ectodomain of the cell adhesion molecule E-cadherin on the surface of host cells. Additionally to the function as an adhesion molecule, the transmembrane protein E-cadherin suppresses the development and progression of cancer through its binding to intracellular catenins, which play important roles in cancer- and migration-associated signal transduction pathways. In the proposed project, we will analyze the functional consequences of HtrA-mediated E-cadherin ectodomain shedding on Hp-induced migration of gastric epithelial cells. We will identify the specific cleavage site for the bacterial serine protease HtrA in the E-cadherin molecule and create a protease-resistant mutant. The cleavage- resistant E-cadherin variant will be expressed in epithelial host cells to characterize the effects of protein cleavage on the motility of Hp-infected epithelial cells. In combination with our pharmacological lead structure (HHI) inhibiting HpHtrA activity, the disintegration and subcellular localization of the E-cadherin complex upon Hp- mediated cleavage will be determined. Eukaryotic proteases shedding the E-cadherin`s ectodomain destabilize the intracellular protein complex. Hence, we will continue to characterize and quantify the effect of E-cadherin fragmentation on Hp-mediated cell motility and cellular invasion. The prospective direct influence of released catenins in the regulation of the Rho GTPase activity, which are crucially involved in cellular migration, will be investigated in generated stable a-catenin and p120ctn knock-down cell lines. The analyses of E-cadherin cleavage during Hp-induced cell migration will add important aspects to a better understanding of invasive growth of cancer cells that leads to the high mortality of gastric cancer.

The gastric epithelium is established and maintained through intact cell-cell adhesions, a tightly regulated actin cytoskeleton and an apical-basal polarity forming effective barriers against pathogens. However, the human pathogen and class-1 carcinogen Helicobacter pylori (Hp) developed fascinating strategies to disrupt the epithelial barrier function where it induces inflammatory and neoplastic disorders in the human stomach. In-vitro, Hp mediates a strong migration of epithelial host cells which involves a drastic loss of intercellular adhesions. In our previous studies, we identified the Hp-secreted protease HtrA that directly cleaves the ectodomain of the cell adhesion molecule E-cadherin on the surface of host cells. Additionally to the function as an adhesion molecule, the transmembrane protein E-cadherin suppresses the development and progression of cancer through its binding to intracellular catenins, which play important roles in cancer- and migration-associated signal transduction pathways. In the proposed project, we will analyze the functional consequences of HtrA-mediated E-cadherin ectodomain shedding on Hp-induced migration of gastric epithelial cells. We will identify the specific cleavage site for the bacterial serine protease HtrA in the E-cadherin molecule and create a protease-resistant mutant. The cleavage-resistant E-cadherin variant will be expressed in epithelial host cells to characterize the effects of protein cleavage on the motility of Hp-infected epithelial cells. In combination with our pharmacological lead structure (HHI) inhibiting HpHtrA activity, the disintegration and subcellular localization of the E-cadherin complex upon Hp-mediated cleavage will be determined. Eukaryotic proteases shedding the E-cadherins ectodomain destabilize the intracellular protein complex. Hence, we will continue to characterize and quantify the effect of E-cadherin fragmentation on Hp-mediated cell motility and cellular invasion. The prospective direct influence of released catenins in the regulation of the Rho GTPase activity, which are crucially involved in cellular migration, will be investigated in generated stable -catenin and p120ctn knock-down cell lines. The analyses of E-cadherin cleavage during Hp-induced cell migration will add important aspects to a better understanding of invasive growth of cancer cells that leads to the high mortality of gastric cancer.