Regulation of RKIP function by Helicobacter pylori in gastric cancer.
Helicobacter pylori (H. pylori) is a gram-negative, spiral-shaped bacterium that infects more than half of the world's population and is a major cause of gastric adenocarcinoma. The mechanisms that link H. pylori infection to gastric carcinogenesis are not well understood. In the present study, we report that the Raf-kinase inhibitor protein (RKIP) has a role in the induction of apoptosis by H. pylori in gastric epithelial cells. Western blot and luciferase transcription reporter assays demonstrate that the pathogenicity island of H. pylori rapidly phosphorylates RKIP, which then localizes to the nucleus where it activates its own transcription and induces apoptosis. Forced overexpression of RKIP enhances apoptosis in H. pylori-infected cells, whereas RKIP RNA inhibition suppresses the induction of apoptosis by H. pylori infection. While inducing the phosphorylation of RKIP, H. pylori simultaneously targets non-phosphorylated RKIP for proteasome-mediated degradation. The increase in RKIP transcription and phosphorylation is abrogated by mutating RKIP serine 153 to valine, demonstrating that regulation of RKIP activity by H. pylori is dependent upon RKIP's S153 residue. In addition, H. pylori infection increases the expression of Snail, a transcriptional repressor of RKIP. Our results suggest that H. pylori utilizes a tumor suppressor protein, RKIP, to promote apoptosis in gastric cancer cells.
Department of Medicine, Rhode Island Hospital, Providence, Rhode Island, United States of America.
Erika L
EL
Moen
Sicheng
S
Wen
Talha
T
Anwar
Sam
S
Cross-Knorr
Kate
K
Brilliant
Faith
F
Birnbaum
Sherida
S
Rahaman
John M
JM
Sedivy
Steven F
SF
Moss
Devasis
D
Chatterjee
D000942:Antigens, Bacterial / Q000378:metabolism; D017209:Apoptosis / Q000235:genetics; D001426:Bacterial Proteins / Q000378:metabolism; D045744:Cell Line, Tumor; D016481:Helicobacter Infections / Q000378:metabolism*; D016480:Helicobacter pylori / Q000378:metabolism* / Q000472:pathogenicity; D006801:Humans; D015850:Interleukin-6 / Q000494:pharmacology; D049488:Phosphatidylethanolamine Binding Protein / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D011493:Protein Kinase C / Q000378:metabolism; D055550:Protein Stability; D021381:Protein Transport; D050796:STAT3 Transcription Factor / Q000235:genetics / Q000378:metabolism; D000071250:Snail Family Transcription Factors; D013274:Stomach Neoplasms / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism; D014158:Transcription, Genetic / Q000187:drug effects
D000942:Antigens, Bacterial; D001426:Bacterial Proteins; D015850:Interleukin-6; C511482:PEBP1 protein, human; D049488:Phosphatidylethanolamine Binding Protein; D050796:STAT3 Transcription Factor; D000071250:Snail Family Transcription Factors; D014157:Transcription Factors; C080866:cagA protein, Helicobacter pylori; D011493:Protein Kinase C