Roles of the components of the cag-pathogenicity island encoded type IV secretion system in Helicobacter pylori

Abstract

The Helicobacter pylori (H. pylori) cytotoxin-associated gene pathogenicity island (cagPAI) encodes 31 genes that assemble the cag type IV secretion system (T4SS) apparatus, which includes structures such as the outer membrane core complex, periplasmic ring, inner membrane complex and bacterial hairs. These proteins interact with each other to inject CagA into the host gastric epithelium. There are also individual unique functions that help H. pylori interfere with host cellular pathways, modulate the immune response and colonize the host for a long time. However, the functions of some of the proteins remain unclear. This review summarizes what is known about the structure and function of these auxiliary components and discusses their role in H. pylori pathogenesis.

Keywords: Cag-T4SS; CagL; CagY; Helicobacter pylori; cagPAI.

Figure 1.

Schematic representation of the Helicobacter pylori Cag-T4SS. A schematic of the specific locations of the currently known cagPAI components is modelled as shown in Fig. The Pilus component, OMCC, IMC and other components are shown in the boxes. Specifically included are pilus: CagL; OMCC: CagY, CagX, CagT, Cag3 (Cagδ) and CagM; IMC: CagE, Cagα, Cagβ, B8 (CagV),and B6 (CagW); and the translocation molecules CagF and CagZ. The components of the Cag-T4SS are depicted in a simplified manner. They are not drawn to scale or in the exact number of subunits and are positioned based on the predicted structure or experimental data. Each defined component of the Cag-T4SS is indicated in a different color based on its coding.