Phosphate starvation: A novel signal that triggers ESX-5 secretion in Mycobacterium tuberculosis

Sarah R. Elliott, Anna D. Tischler

Research output: Contribution to journalArticlepeer-review

30 Scopus citations

Abstract

Mycobacterium tuberculosis uses the Type VII ESX secretion systems to transport proteins across its complex cell wall. ESX-5 has been implicated in M. tuberculosis virulence, but the regulatory mechanisms controlling ESX-5 secretion were unknown. Here we uncover a link between ESX-5 and the Pst/SenX3-RegX3 system that controls gene expression in response to phosphate availability. The DNA-binding response regulator RegX3 is normally activated by phosphate limitation. Deletion of pstA1, which encodes a Pst phosphate uptake system component, causes constitutive activation of RegX3. A ΔpstA1 mutant exhibited RegX3-dependent overexpression of esx-5 genes and hyper-secretion of the ESX-5 substrates EsxN and PPE41 when the bacteria were grown in phosphate-rich medium. In wild-type M. tuberculosis, phosphate limitation activated esx-5 transcription and secretion of both EsxN and PPE41, and this response required RegX3. Electrophoretic mobility shift assays revealed that RegX3 binds directly to a promoter within the esx-5 locus. Remarkably, phosphate limitation also induced secretion of EsxB, an effector of the virulence-associated ESX-1 secretion system, though this induction was RegX3 independent. Our work demonstrates that the Pst/SenX3-RegX3 system directly regulates ESX-5 secretion at the transcriptional level in response to phosphate availability and defines phosphate limitation as an environmental signal that activates ESX-5 secretion.

Original languageEnglish (US)
Pages (from-to)510-526
Number of pages17
JournalMolecular Microbiology
Volume100
Issue number3
DOIs
StatePublished - May 1 2016

Bibliographical note

Funding Information:
We thank Dr. Wilbert Bitter for generously providing anti-sera against the EccB5, EspG5, EsxN and PPE41 proteins, Dr. Stewart Cole for providing anti-sera against EspB, and Dr. Jennifer L. Dale for critical reading of the manuscript. The following reagents were obtained through BEI Resources, NIAID, NIH: Polyclonal Anti-Mycobacterium tuberculosis CFP10 (Gene Rv3874, EsxB) (antiserum, Rabbit), NR-13801; Monoclonal Anti-Mycobacterium tuberculosis GroEL2 (Gene Rv0440), Clone IT-70 (DCA4) (produced in vitro), NR-13657; Polyclonal Anti-Mycobacterium tuberculosis Mpt32 (Gene Rv1860) (antiserum, Rabbit), NR-13807; and Polyclonal Anti- Mycobacterium tuberculosis Antigen 85 complex (FbpA/FbpB/ FbpC; Genes Rv3804c, Rv1886c, Rv0129c) (antiserum, Rabbit), NR-13800. This work was supported by institutional startup funds from the University of Minnesota, and New Faculty and Equipment Grants from the University of Minnesota Foundation (A.D.T.). The authors have no conflicts of interest to declare.

Funding Information:
We thank Dr. Wilbert Bitter for generously providing anti-sera against the EccB5, EspG5, EsxN and PPE41 proteins, Dr. Stewart Cole for providing anti-sera against EspB, and Dr. Jennifer L. Dale for critical reading of the manuscript. The following reagents were obtained through BEI Resources, NIAID, NIH: Polyclonal Anti-Mycobacterium tuberculosis CFP10 (Gene Rv3874, EsxB) (antiserum, Rabbit), NR-13801; Monoclonal Anti-Mycobacterium tuberculosis GroEL2 (Gene Rv0440), Clone IT-70 (DCA4) (produced in vitro), NR-13657; Polyclonal Anti-Mycobacterium tuberculosis Mpt32 (Gene Rv1860) (antiserum, Rabbit), NR-13807; and Polyclonal Anti- Mycobacterium tuberculosis Antigen 85 complex (FbpA/FbpB/ FbpC; Genes Rv3804c, Rv1886c, Rv0129c) (antiserum, Rabbit), NR-13800. This work was supported by institutional startup funds from the University of Minnesota, and New Faculty and Equipment Grants from the University of Minnesota Foundation (A.D.T.). The authors have no conflicts of interest to declare.

Publisher Copyright:
© 2016 John Wiley & Sons Ltd.

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