Tertiary Structure-Function Analysis Reveals the Pathogenic Signaling Potentiation Mechanism of Helicobacter pylori Oncogenic Effector CagA

Abstract

The Helicobacter pylori type IV secretion effector CagA is a major bacterial virulence determinant and critical for gastric carcinogenesis. Upon delivery into gastric epithelial cells, CagA localizes to the inner face of the plasma membrane, where it acts as a pathogenic scaffold/hub that promiscuously recruits host proteins to potentiate oncogenic signaling. We find that CagA comprises a structured N-terminal region and an intrinsically disordered C-terminal region that directs versatile protein interactions. X-ray crystallographic analysis of the N-terminal CagA fragment (residues 1-876) revealed that the region has a structure comprised of three discrete domains. Domain I constitutes a mobile CagA N terminus, while Domain II tethers CagA to the plasma membrane by interacting with membrane phosphatidylserine. Domain III interacts intramolecularly with the intrinsically disordered C-terminal region, and this interaction potentiates the pathogenic scaffold/hub function of CagA. The present work provides a tertiary-structural basis for the pathophysiological/oncogenic action of H. pylori CagA.

Helicobacter pylori CagA promotes Snail-mediated epithelial–mesenchymal transition by reducing GSK-3 activity

“…In this study, we found that multiple domains of CagA are also responsible for Snail stabilization and that the C-terminus of CagA having the EPIYA motif binds to 38). Considering that a dynamic CagA structure having a-helices and undergoing activation of the Wnt/EMT process depends on more than EPIYA phosphorylation 26,29,45 , it is not surprising that many domains of CagA are able to bind GSK-3, resulting in depletion of GSK-3 and subsequent increased Snail protein abundance.…”

“…that EPIYA motif phosphorylation plays important roles in entire CagA structure and protein interactions 29 . In this study, we found that multiple domains of CagA are also responsible for Snail stabilization and that the C-terminus of CagA having the EPIYA motif binds to 38).…”

“…3b). Intriguingly, the EPIYA phosphorylation motif on the C-terminus strongly reinforces CagA function on Snail abundance, whereas the N-terminus of CagA including domain I and a subdomain of domain II were only minimally or moderately effective 26,29 . These results indicate that multiple domains of CagA are responsible for the stabilization of Snail.…”

“…As CagA comprises multiple structural domains 29 , we next made several expression constructs to determine the domain of CagA responsible for stabilizing Snail (Fig. 3a).…”

Structure et mode d’injection de l’oncoprotéine CagA d’Helicobacter pylori

“…Les cellules LLC-B ont un métab olisme plus actif que les cellules saines, ce qui entraîne une production plus importante de radicaux libres et une dépendance vis-à-vis des antioxydants cellulaires comme le glutathion (GSH) pour maintenir leur balance redox intracellulaire [8,9]. De plus, l'interaction des cellules LLC-B avec les cellules accessoires (cellules stromales, cellules nurse-like) dans la moelle osseuse ou les ganglions est aussi importante pour leur survie [10,11]. En effet, les cellules leucémiques expriment à leur surface le récepteur de chémokines CXCR4 Résistance des cellules de LLC à l'apoptose…”