Inhibitors of Helicobacter pylori ATPase Cagalpha block CagA transport and cag virulence.
With the steadily increasing occurrence of antibiotic resistance in bacteria, there is a great need for new antibacterial compounds. The approach described here involves targeting virulence-related bacterial type IV secretion systems (TFSSs) with small-molecule inhibitors. The cag TFSS of Helicobacter pylori was chosen as a model, and novel inhibitors directed against the cag VirB11-type ATPase Cagalpha were identified. The cag genes encode proteins that are components of a contact-dependent secretion system used by the bacterium to translocate the effector molecule CagA into host cells. Translocated CagA is associated with severe gastritis, and carcinoma. Furthermore, functional TFSSs and immunodominant CagA play a role in interleukin (IL)-8 induction, which is an important factor for chronic inflammation. Inhibitors of Cagalpha were identified by high-throughput screening of chemical libraries that comprised 524 400 small molecules. The ATPase activity of Cagalpha was inhibited by the selected compounds in an in vitro enzymic assay using the purified enzyme. The most active compound, CHIR-1, reduced TFSS function to an extent that cellular effects on AGS cells mediated by CagA were virtually undetectable, while reduced levels of IL-8 induction were observed. Gastric colonization by CHIR-1-pre-treated bacteria was found to be impaired in a dose-dependent manner using a mouse model of infection. Small-molecule Cagalpha inhibitors, the first described inhibitors of a TFSS, are potential candidates for the development of new antibacterial compounds that may lead to alternative medical treatments. The compounds are expected to impose weak selective pressure, since they target virulence functions. Moreover, the targeted virulence protein is conserved in a variety of bacterial pathogens. Additionally, TFSS inhibitors are potent tools to study the biology of TFSSs.
Hilleringmann
Markus
M
Cellular Microbiology and Bioinformatics Unit, Immunological Research Institute Siena (IRIS), Novartis Vaccines S.r.l., Via Fiorentina 1, I-53100 Siena, Italy.
Pansegrau
Werner
W
Cellular Microbiology and Bioinformatics Unit, Immunological Research Institute Siena (IRIS), Novartis Vaccines S.r.l., Via Fiorentina 1, I-53100 Siena, Italy.
Doyle
Michael
M
Research and Development, Biopharmaceuticals, Novartis, 4560 Horton St M/S 4.4, Emeryville, CA 94608-2916, USA.
Kaufman
Susan
S
Research and Development, Biopharmaceuticals, Novartis, 4560 Horton St M/S 4.4, Emeryville, CA 94608-2916, USA.
MacKichan
Mary Lee
ML
Research and Development, Biopharmaceuticals, Novartis, 4560 Horton St M/S 4.4, Emeryville, CA 94608-2916, USA.
Gianfaldoni
Claudia
C
Serology and Animal Model Unit, Immunological Research Institute Siena (IRIS), Novartis Vaccines S.r.l., Via Fiorentina 1, I-53100 Siena, Italy.
Ruggiero
Paolo
P
Serology and Animal Model Unit, Immunological Research Institute Siena (IRIS), Novartis Vaccines S.r.l., Via Fiorentina 1, I-53100 Siena, Italy.
Covacci
Antonello
A
Cellular Microbiology and Bioinformatics Unit, Immunological Research Institute Siena (IRIS), Novartis Vaccines S.r.l., Via Fiorentina 1, I-53100 Siena, Italy.
D000251:Adenosine Triphosphatases / Q000037:antagonists & inhibitors*; D000818:Animals; D000900:Anti-Bacterial Agents / Q000302:isolation & purification / Q000494:pharmacology*; D000942:Antigens, Bacterial / Q000378:metabolism*; D001426:Bacterial Proteins / Q000378:metabolism*; D045744:Cell Line, Tumor; D015169:Colony Count, Microbial; D004353:Drug Evaluation, Preclinical; D004791:Enzyme Inhibitors / Q000302:isolation & purification / Q000494:pharmacology*; D004847:Epithelial Cells / Q000382:microbiology; D005753:Gastric Mucosa / Q000382:microbiology; D016481:Helicobacter Infections / Q000382:microbiology / Q000517:prevention & control; D016480:Helicobacter pylori / Q000187:drug effects / Q000201:enzymology* / Q000472:pathogenicity*; D006801:Humans; D016209:Interleukin-8 / Q000096:biosynthesis; D051379:Mice; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D014774:Virulence
D000900:Anti-Bacterial Agents; D000942:Antigens, Bacterial; D001426:Bacterial Proteins; D004791:Enzyme Inhibitors; D016209:Interleukin-8; C080866:cagA protein, Helicobacter pylori; D000251:Adenosine Triphosphatases