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Bacterial toxin modulation of the eukaryotic cell cycle: are all cytolethal distending toxins created equally?
Amandeep Gargi1, Michael Reno, Steven R Blanke
1Department of Microbiology, Institute for Genomic Biology, University of Illinois Urbana, IL, USA.
Abstract:
The cytolethal distending toxins (CDTs) comprise a family of intracellular-acting bacterial protein toxins whose actions upon eukaryotic cells result in several consequences, the most characteristic of which is the induction of G(2)/M cell cycle arrest. Most CDTs are hetero-tripartite assemblies of CdtA, CdtB, and CdtC, with CdtB required for CDT-mediated cell cycle arrest. Several lines of evidence indicate that CdtA and CdtC are required for the optimal intracellular activity of CdtB, although the exact functional roles of CdtA and CdtC remain poorly understood. The genes encoding the CDTs have been identified in a diverse array of Gram-negative pathogenic bacteria. More recently, the genes encoding several CdtB subunits have been associated with alternatively linked subunits resembling the B-subunits of pertussis toxin. Although the CDTs are generally considered to all function as bacterial genotoxins, the extent to which individual members of the CDTs employ similar mechanisms of cell surface binding, uptake, and trafficking within sensitive cells is poorly understood. Recently, data have begun to emerge suggesting differences in the molecular basis by which individual CDTs interact with and enter host cells, suggesting the possibility that CDTs possess properties reflecting the specific niches idiosyncratic to those CDT bacterial pathogens that produce them. The extent to which functional differences between individual CDTs reflect the specific requirements for intoxicating cells and tissues within the diverse range of host microenvironments colonized by CDT-producing pathogenic bacteria remains to be experimentally explored.
Insights
Cytolethal distending toxins (CDTs) cause cell cycle arrest. While CdtB is essential, the roles of CdtA and CdtC subunits in CDT toxin activity and host cell interactions require further investigation.
Area of Science:
- Microbiology
- Molecular Biology
- Toxicology
Background:
- Cytolethal distending toxins (CDTs) are bacterial protein toxins known to induce G2/M cell cycle arrest in eukaryotic cells.
- CDTs are typically composed of three subunits: CdtA, CdtB, and CdtC, with CdtB being crucial for the toxin's cell cycle-arresting activity.
Purpose of the Study:
- To investigate the precise functional roles of CdtA and CdtC subunits in CDT-mediated intracellular activity.
- To explore the diversity in cell surface binding, uptake, and trafficking mechanisms among different CDT toxins.
- To understand how variations in CDT toxin mechanisms relate to the specific host microenvironments of producing bacteria.
Main Methods:
- Literature review and analysis of existing data on CDT structure and function.
- Comparative analysis of CDT genes found in various Gram-negative pathogenic bacteria.
- Examination of emerging data on host cell interactions of different CDT toxin members.
Main Results:
- CdtA and CdtC are necessary for optimal intracellular activity of CdtB, though their exact functions are not fully elucidated.
- CDT genes are present in a wide range of Gram-negative pathogens, with some CdtB subunits associated with pertussis toxin-like subunits.
- Emerging evidence suggests variability in how different CDTs bind to, enter, and traffic within host cells.
Conclusions:
- The specific roles of CdtA and CdtC in CDT toxin function warrant further research.
- Differences in CDT toxin entry and trafficking mechanisms may be linked to the ecological niches of the bacteria that produce them.
- Experimental exploration is needed to determine if functional variations in CDTs correlate with the requirements for intoxicating specific host tissues.
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