TheHelicobacter pyloritypeIVsecretion system upregulates epithelial cortactin expression by aCagA‐ andJNK‐dependent pathway

Abstract

Cortactin represents an important actin‐binding factor, which controls actin‐cytoskeletal remodelling in host cells. In this way, cortactin has been shown to exhibit crucial functions both for cell movement and tumour cell invasion. In addition, the cortactin gene cttn is amplified in various cancer types of humans. Helicobacter pylori is the causative agent of multiple gastric diseases and represents a significant risk factor for the development of gastric adenocarcinoma. It has been repeatedly shown that H. pylori manipulates cancer‐related signal transduction events in infected gastric epithelial cells such as the phosphorylation status of cortactin. In fact, H. pylori modifies the activity of cortactin's binding partners to stimulate changes in the actin‐cytoskeleton, cell adhesion and motility. Here we show that H. pylori infection of cultured AGS and Caco‐2 cells for 24–48 hr leads to the overexpression of cortactin by 2–3 fold at the protein level. We demonstrate that this activity requires the integrity of the type IV secretion system (T4SS) encoded by the cag pathogenicity island (cagPAI) as well as the translocated effector protein CagA. We further show that ectopic expression of CagA is sufficient to stimulate cortactin overexpression. Furthermore, phosphorylation of CagA at the EPIYA‐repeat region is not required, suggesting that this CagA activity proceeds in a phosphorylation‐independent fashion. Inhibitor studies further demonstrate that the involved signalling pathway comprises the mitogen‐activated protein kinase JNK (c‐Jun N‐terminal kinase), but not ERK1/2 or p38. Taken together, using H. pylori as a model system, this study discovered a previously unrecognised cortactin activation cascade by a microbial pathogen. We suggest that H. pylori targets cortactin to manipulate the cellular architecture and epithelial barrier functions that can impact gastric cancer development. Take Aways Helicobacter pylori infection induces overexpression of cortactin at the protein level Cortactin upregulation requires the T4SS and effector protein CagA Ectopic expression of CagA is sufficient to stimulate cortactin overexpression Overexpression of cortactin proceeds CagA phosphorylation‐independent The involved host cell signalling pathway comprises the MAP kinase JNK

Cortactin: A universal host cytoskeletal target of Gram‐negative and Gram‐positive bacterial pathogens

“…In line with these observations, complete cortactin knockout strongly diminished this phenotype (Knorr et al, 2021). Moreover, H. pylori upregulate the expression of cortactin via translocated CagA in a c‐Jun N‐terminal kinase (JNK)‐dependent manner, which inhibits Snail1, a controller of cttn gene expression, and promotes stabilization of cortactin by paxillin and FAK to protect it from degradation (Figure 2d) (Sharafutdinov et al, 2021a). The pathogen furthermore manipulates cortactin phosphorylation (Sharafutdinov et al, 2020).…”

Cortactin Promotes Effective AGS Cell Scattering by Helicobacter pylori CagA, but Not Cellular Vacuolization and Apoptosis Induced by the Vacuolating Cytotoxin VacA

“…Afterwards, serine-phosphorylated cortactin induces the auto-phosphorylation of FAK at tyrosine 397, which triggers a signaling pathway involving the activation of Src and Abl kinases, which results in the pronounced phosphorylation of injected CagA [49]. Furthermore, it was shown that H. pylori triggers cortactin overexpression at the protein level in a CagA-and JNK-dependent manner, which can be associated with gastric carcinogenesis [63]. However, other H. pylori virulence factors such as VacA have also been reported to target cortactin.…”

“…Prior to probing, the PVDF membranes were blocked with either 3% BSA or 5% non-fat dry milk in TBST, depending on the primary antibody and manufacturers instructions [70]. Primary antibodies used were specific against cortactin (Merck-Millipore, Darmstadt, Germany #05-180), GAPDH (Santa Cruz, Heidelberg, Germany, #SC-47724), CagA (Austral Biologicals, San Ramon, CA, USA, #HPP-5003-9), CagE [63], VacA [34], FlaA [71], RPTP-α (Santa Cruz, #SC-28907), integrin-β1 (Santa Cruz, #SC-H96), full-length caspase-3 (Cell Signaling Technology, Frankfurt, Germany, #9668) and active caspase-3 (Cell Signaling Technology, #9664). Secondary antibodies detected either mouse (Invitrogen, Darmstadt, Germany, #31446) or rabbit (Invitrogen, #31460) primary antibodies and were coupled to horseradish peroxidase.…”

Influence of Helicobacter pylori oncoprotein CagA in gastric cancer: A critical-reflective analysis

“…However, it is still unclear whether the instability of the HopQ–CEACAMs relationship favors the host or the bacterium, so more studies are needed to investigate the possibility of these interactions being beneficial in favor of the patient infected with H. pylori. BabA is apparently also capable of increasing T4SS activity[ 55 ].…”