Abstract
RhoB is the only member of the Rho subfamily of small GTPases, which is classified as an immediate early gene product. RhoB is up-regulated in response to growth factors as well as cytotoxic and genotoxic agents. Clostridial glucosylating toxins have been reported to evoke pronounced RhoB expression, based on the inactivation of Rho/Ras proteins. In this study, we report on a long lasting expression of RhoB in cultured cells upon activation of Rho proteins by the cytotoxic necrotizing factor 1 (CNF1) from Escherichia coli. The observations of this study highlight a new pathway involving Rac1, which positively regulates the activity of the rhoB promoter and RhoB expression. Conversely, the isomeric cytotoxic necrotizing factor from Yersinia pseudotuberculosis (CNFy) drives GTP-loading of basal RhoB but fails to cause activation of the rhoB promoter and thus its expression. CNF1 inhibits cytokinesis and induces the formation of bi-nucleated (tetraploid) cells. Upon long term treatment with CNF1, RhoB(-/-) mouse embryonic fibroblasts (MEFs) exhibit DNA fragmentation, phosphatidylserine exposure, and loss of membrane integrity, while RhoB(+/-) MEFs persist as bi-nucleated (tetraploid) cells without any signs of cell death. In conclusion, the cytoprotective RhoB response is not only evoked by bacterial protein toxins inactivating Rho/Ras proteins but also by the Rac1-activating toxin CNF1.
Original language | English |
---|---|
Journal | International Journal of Biochemistry & Cell Biology |
Volume | 45 |
Issue number | 8 |
Pages (from-to) | 1767-75 |
Number of pages | 9 |
ISSN | 1357-2725 |
DOIs | |
Publication status | Published - Aug 2013 |
Keywords
- Animals
- Bacterial Toxins
- Cell Death
- Cell Shape
- Cytoprotection
- Enzyme Activation
- Escherichia coli
- Escherichia coli Proteins
- Gene Expression Regulation
- HT29 Cells
- HeLa Cells
- Humans
- Mice
- NIH 3T3 Cells
- Polyploidy
- Promoter Regions, Genetic
- RNA, Messenger
- Transcriptional Activation
- Yersinia pseudotuberculosis
- rac1 GTP-Binding Protein
- rhoB GTP-Binding Protein