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Chlamydia trachomatis Infection Leads to Defined Alterations to the Lipid Droplet Proteome in Epithelial Cells
Hector Alex Saka1, J Will Thompson2, Yi-Shan Chen1
1Department of Molecular Genetics and Microbiology and Center for Microbial Pathogenesis, Duke University Medical Center, Durham, North Carolina, United States of America.
Abstract:
The obligate intracellular bacterium Chlamydia trachomatis is a major human pathogen and a main cause of genital and ocular diseases. During its intracellular cycle, C. trachomatis replicates inside a membrane-bound vacuole termed an "inclusion". Acquisition of lipids (and other nutrients) from the host cell is a critical step in chlamydial replication. Lipid droplets (LD) are ubiquitous, ER-derived neutral lipid-rich storage organelles surrounded by a phospholipids monolayer and associated proteins. Previous studies have shown that LDs accumulate at the periphery of, and eventually translocate into, the chlamydial inclusion. These observations point out to Chlamydia-mediated manipulation of LDs in infected cells, which may impact the function and thereby the protein composition of these organelles. By means of a label-free quantitative mass spectrometry approach we found that the LD proteome is modified in the context of C. trachomatis infection. We determined that LDs isolated from C. trachomatis-infected cells were enriched in proteins related to lipid metabolism, biosynthesis and LD-specific functions. Interestingly, consistent with the observation that LDs intimately associate with the inclusion, a subset of inclusion membrane proteins co-purified with LD protein extracts. Finally, genetic ablation of LDs negatively affected generation of C. trachomatis infectious progeny, consistent with a role for LD biogenesis in optimal chlamydial growth.
Insights
Chlamydia trachomatis infection alters the protein composition of host cell lipid droplets (LDs). These modified LDs are crucial for bacterial replication, as their absence impairs the generation of infectious Chlamydia trachomatis progeny.
Area of Science:
- Microbiology
- Cell Biology
- Infectious Diseases
Background:
- Chlamydia trachomatis is an obligate intracellular bacterium causing significant human diseases.
- Chlamydia replicates within a host-derived vacuole called an inclusion.
- Lipid droplets (LDs) are host cell organelles that Chlamydia interacts with during infection.
Purpose of the Study:
- To investigate how Chlamydia trachomatis infection modifies the proteome of host cell lipid droplets.
- To determine the functional significance of these LD modifications for bacterial replication.
Main Methods:
- Label-free quantitative mass spectrometry was employed to analyze LD protein composition.
- LDs were isolated from both uninfected and Chlamydia-infected host cells.
- Genetic ablation of LDs was performed to assess their role in chlamydial growth.
Main Results:
- Chlamydia infection significantly altered the proteome of isolated LDs.
- Infected LDs showed enrichment in proteins involved in lipid metabolism, biosynthesis, and LD-specific functions.
- A subset of inclusion membrane proteins was found to co-purify with LD protein extracts.
- Genetic removal of LDs impaired the production of infectious Chlamydia trachomatis progeny.
Conclusions:
- Chlamydia trachomatis actively manipulates host cell lipid droplets, altering their protein composition.
- Modified lipid droplets play a critical role in supporting optimal chlamydial replication and progeny production.
- LDs and the chlamydial inclusion membrane interact, suggesting a direct role in nutrient acquisition or manipulation.
