ABSTRACT
Chlamydia trachomatis, an obligate intracellular bacterium with limited metabolic capabilities, possesses the futalosine pathway for menaquinone biosynthesis. Futalosine pathway enzymes have promise as narrow spectrum targets, but the activity and essentiality of chlamydial menaquinone biosynthesis have yet to be established. In this work, menaquinone-7 (MK-7) was identified as a C. trachomatis-produced quinone through LC-MS/MS. An immunofluorescence-based assay revealed that treatment of C. trachomatis-infected HeLa cells with futalosine pathway inhibitor docosahexaenoic acid (DHA) reduced inclusion number, inclusion size, and infectious progeny. Supplementation with MK-7 nanoparticles rescued the effect of DHA on inclusion number, indicating that the futalosine pathway is a target of DHA in this system. These results open the door for menaquinone biosynthesis inhibitors to be pursued in antichlamydial development.
Competing Interest Statement
The authors have declared no competing interest.
Abbreviations
- ATP
- adenosine triphosphate;
- DHA
- docosahexaenoic acid;
- DMEM
- Dulbecco’s modified Eagle’s medium;
- EIC
- extracted ion chromatogram;
- FBS
- fetal bovine serum;
- IFU
- inclusion-forming unit;
- LC-MS/MS
- liquid chromatography-tandem mass spectrometry;
- MK-4
- menaquinone-4;
- MK-7
- menaquinone-7;
- MOI
- multiplicity of infection;
- MS
- mass spectrometry;
- MTAN
- 5’-methylthioadenosine nucleosidase;
- MTT
- 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide;
- PBS
- phosphate-buffered saline;
- s.e.m.
- standard error of the mean;
- SPG
- sucrose-phosphate-glutamate