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Updated: Jul 22, 2025
Markerless Gene Deletion by Floxed Cassette Allelic Exchange Mutagenesis in Chlamydia trachomatis
Published on: January 30, 2020
Chlamydia trachomatis TmeB antagonizes actin polymerization via direct interference with Arp2/3 activity
Kaylyn R Scanlon1, Gabrielle Keb2, Katerina Wolf2
1Division of Immunity and Pathogenesis, Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida, Orlando, FL, United States.
Abstract:
Chlamydia trachomatis is an obligate intracellular pathogen that actively promotes invasion of epithelial cells. A virulence-associated type III secretion system contributes to chlamydial entry and at least four effectors have been described that are deployed during this time. Two of these invasion-related effectors, the translocated membrane-associated effectors A and B (TmeA and TmeB), are encoded in a bi-cistronic operon. TmeA directly activates host N-WASP to stimulate Arp2/3-dependent actin polymerization. According to current working models, TmeA-mediated N-WASP activation contributes to invasion. TmeB has not been functionally characterized. Unlike a tmeA null strain, loss of tmeB does not impact invasion efficiency of C. trachomatis. Using strains deficient for multiple genes, we provide evidence that TmeA is dispensable for invasion in the absence of TmeB. Our data indicate that overabundance of TmeB interferes with invasion and that this activity requires active Arp2/3 complex. We further show that TmeB is capable of interfering with Arp2/3-mediated actin polymerization. In aggregate, these data point to opposing functions for TmeA and TmeB that manifest during the invasion process. These studies raise intriguing questions regarding the dynamic interplay between TmeA, TmeB, and branched actin polymerization during chlamydial entry.
Insights
Chlamydia trachomatis invasion involves effectors TmeA and TmeB with opposing roles in actin polymerization. TmeA promotes invasion, while TmeB inhibits it by interfering with Arp2/3 complex activity.
Area of Science:
- Microbiology
- Cell Biology
- Pathogen-Host Interactions
Background:
- Chlamydia trachomatis uses a type III secretion system for epithelial cell invasion.
- Invasion effectors TmeA and TmeB are encoded together and TmeA activates N-WASP for actin polymerization.
- The function of TmeB and the interplay between TmeA and TmeB during invasion remain unclear.
Purpose of the Study:
- To functionally characterize TmeB and elucidate the roles of TmeA and TmeB in Chlamydia trachomatis invasion.
- To investigate the mechanism by which TmeB affects host cell invasion.
- To explore the opposing functions of TmeA and TmeB in the context of actin polymerization.
Main Methods:
- Genetic manipulation of Chlamydia trachomatis strains to create TmeA and TmeB deficient mutants.
- Analysis of bacterial invasion efficiency using various mutant strains.
- Investigating the role of the Arp2/3 complex in TmeB-mediated inhibition of invasion.
- Biochemical assays to assess TmeB's effect on actin polymerization.
Main Results:
- TmeA is dispensable for invasion when TmeB is absent.
- TmeB overabundance inhibits Chlamydia trachomatis invasion, requiring an active Arp2/3 complex.
- TmeB directly interferes with Arp2/3-mediated actin polymerization.
Conclusions:
- TmeA and TmeB possess opposing functions during Chlamydia trachomatis invasion.
- TmeB acts as an inhibitor of invasion by disrupting Arp2/3-dependent actin polymerization.
- These findings reveal a complex regulatory mechanism involving TmeA, TmeB, and actin dynamics during bacterial entry.
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