Helicobacter pylori Exploits a Unique Repertoire of Type IV Secretion System Components for Pilus Assembly at the Bacteria-Host Cell Interface

PLoS Pathogens

Ewa E. Hennig¹  Elizabeth M. Johnson²  John T. Loh²  Jennifer A. Gaddy²  Mark S. McClain²  Carrie L. Shaffer³  Timothy L. Cover³  Salisha Hill⁴  W. Hayes McDonald⁴ 

[1] Department of Gastroenterology and Hepatology, Medical Center for Postgraduate Education, and Department of Oncological Genetics, Cancer Center Institute, Warsaw, Poland;Department of Medicine, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America;Department of Microbiology and Immunology, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America;Proteomics Laboratory, Mass Spectrometry Research Center, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America

关键词: Helicobacter pylori;    Pili;    fimbriae;    Mutant strains;    Epithelial cells;    Secretion systems;    Complement system;    Immune serum;    Immunoblotting;   

DOI  :  10.1371/journal.ppat.1002237

学科分类：生物科学（综合）

来源: Public Library of Science

【 摘 要 】

Colonization of the human stomach by Helicobacter pylori is an important risk factor for development of gastric cancer. The H. pylori cag pathogenicity island (cag PAI) encodes components of a type IV secretion system (T4SS) that translocates the bacterial oncoprotein CagA into gastric epithelial cells, and CagL is a specialized component of the cag T4SS that binds the host receptor α5β1 integrin. Here, we utilized a mass spectrometry-based approach to reveal co-purification of CagL, CagI (another integrin-binding protein), and CagH (a protein with weak sequence similarity to CagL). These three proteins are encoded by contiguous genes in the cag PAI, and are detectable on the bacterial surface. All three proteins are required for CagA translocation into host cells and H. pylori-induced IL-8 secretion by gastric epithelial cells; however, these proteins are not homologous to components of T4SSs in other bacterial species. Scanning electron microscopy analysis reveals that these proteins are involved in the formation of pili at the interface between H. pylori and gastric epithelial cells. ΔcagI and ΔcagL mutant strains fail to form pili, whereas a ΔcagH mutant strain exhibits a hyperpiliated phenotype and produces pili that are elongated and thickened compared to those of the wild-type strain. This suggests that pilus dimensions are regulated by CagH. A conserved C-terminal hexapeptide motif is present in CagH, CagI, and CagL. Deletion of these motifs results in abrogation of CagA translocation and IL-8 induction, and the C-terminal motifs of CagI and CagL are required for formation of pili. In summary, these results indicate that CagH, CagI, and CagL are components of a T4SS subassembly involved in pilus biogenesis, and highlight the important role played by unique constituents of the H. pylori cag T4SS.

【 授权许可】

CC BY