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Type III Secretion in Chlamydia
1Department of Pathology and Microbiology, University of Nebraska Medical Center, Durham Research Center II, Omaha, Nebraska, USA.
Microbiology and Molecular Biology Reviews : MMBR
|June 26, 2023
Summary
Type III secretion systems (T3SSs) are crucial for Chlamydiaceae pathogenesis, delivering effectors to manipulate host cells. This review details T3SS discovery, function, and effectors throughout the chlamydial developmental cycle.
Area of Science:
- Microbiology
- Cell Biology
- Pathogenesis
Background:
- Type III secretion systems (T3SSs) are essential virulence factors in Gram-negative pathogens, enabling direct injection of effector proteins into host cells.
- Chlamydiaceae, obligate intracellular bacteria, possess a highly conserved T3SS critical for their survival and propagation, with a significant portion of their genome dedicated to T3SS components.
- Chlamydiae exhibit a biphasic developmental cycle (infectious elementary bodies and replicative reticulate bodies), with T3SS structures and effectors active at various stages.
Purpose of the Study:
- To review the historical discovery and biochemical characterization of the chlamydial T3SS apparatus and its associated chaperones.
- To elucidate the functional role of the T3SS throughout the chlamydial developmental cycle.
- To discuss recent advances in understanding chlamydial effectors and the use of surrogate models for T3SS research.
Main Methods:
- Review of existing literature on T3SS discovery and characterization in Chlamydiaceae.
- Biochemical analysis of T3SS apparatus components and chaperones.
- Functional analysis of T3SS effectors at different stages of the chlamydial developmental cycle.
- Utilizing heterologous/surrogate models to study chlamydial T3SS.
Main Results:
- The chlamydial T3SS is a conserved, essential system for pathogenesis, operating throughout the organism's biphasic life cycle.
- Biochemical characterization has identified key components of the T3SS apparatus and chaperones, despite limitations in genetic tools.
- Effector proteins delivered by the T3SS play roles in chlamydial entry, intracellular survival, and egress.
Conclusions:
- The chlamydial T3SS is a central virulence determinant, integral to the unique biology and pathogenesis of Chlamydiaceae.
- Understanding the T3SS and its effectors provides insights into host-pathogen interactions and potential therapeutic targets.
- Heterologous systems are valuable tools for dissecting the complex mechanisms of the chlamydial T3SS.
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