Two virulence factors produced by Vibrio cholerae, cholera toxin (CT) and toxin-corregulated pilus (TCP), are indispensable for cholera infection. ToxT is the central regulatory protein involved in activation of CTand TCP expression. We previously reported that lack of a respiration-linked sodium-translocating NADH-ubiquinone oxidoreductase (Na+-NQR) significantly increases toxT transcription. In this study, we further characterized this link and found that Na+-NQR affects toxT expression only at the early-log growth phase, whereas lack of Na+-NQR decreases CT production after the mid-log growth phase. Such decreased CT production was independent of toxT and ctxB transcription. Supplementing a respiratory substrate, l-lactate, into the growth media restored CT production in the nqrA-F mutant, suggesting that decreased CT production in the Na+-NQR mutant is dependent on electron transport chain (ETC) activity. This notion was supported by the observations that two chemical inhibitors, a Na+-NQR specific inhibitor 2-n-Heptyl-4-hydroxyquinoline N-oxide (HQNO) and a succinate dehydrogenase (SDH) inhibitor, thenoyltrifluoroacetone (TTFA), strongly inhibited CT production in both classical and El Tor biotype strains of V.cholerae. Accordingly, we propose the main respiratory enzyme of V.cholerae, as a potential drug target to treat cholera because human mitochondria do not contain Na+-NQR orthologs.
Bibliographical noteFunding Information:
We thank Erin J. Lind, Frances M. Biel and Dr. Alisha M. Aagesen for their excellent technical assistances. This research was supported by grants from the National Institutes of Health to C.C.H. [ AI-063121-02 ]. S.R.F was partially supported by the OSU Undergraduate Research, Innovation, Scholarship & Creativity (URISC) fund and the OSU Howard Hughes Medical Institute Summer Undergraduate Research Program.
- Anti-virulence drug
- Cholera toxin
- Electron transport chain
- Vibrio cholerae