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PLoS Pathog. 2017 Jul 28;13(7):e1006515. doi: 10.1371/journal.ppat.1006515. eCollection 2017 Jul.

Mycobacterium tuberculosis universal stress protein Rv2623 interacts with the putative ATP binding cassette (ABC) transporter Rv1747 to regulate mycobacterial growth.

Author information

1
Department of Medicine, Albert Einstein College of Medicine & Montefiore Medical Center, Bronx, New York, United States of America.
2
Department of Microbiology and Immunology, Albert Einstein College of Medicine & Montefiore Medical Center, Bronx, New York, United States of America.
3
MS & Proteomics Resource of the W.M. Keck Biotechnology Resource Laboratory, Yale University School Medicine, New Haven, Connecticut, United States of America.
4
Department of Molecular Biophysics & Biochemistry, Yale University, New Haven, Connecticut, United States of America.
5
Department of Biochemistry, Albert Einstein College of Medicine & Montefiore Medical Center, Bronx, New York, United States of America.
6
Howard Hughes Medical Institute, Albert Einstein College of Medicine & Montefiore Medical Center, Bronx, New York, United States of America.
7
Department of Microbial Infection and Immunity, College of Medicine, The Ohio State University, Columbus, Ohio, United States of America.
8
Department of Medicine, School of Stomatology and Medicine, Foshan University, Foshan, China.
9
Departments of Physiology & Biophysics, Albert Einstein College of Medicine & Montefiore Medical Center, Bronx, New York, United States of America.

Abstract

We have previously shown that the Mycobacterium tuberculosis universal stress protein Rv2623 regulates mycobacterial growth and may be required for the establishment of tuberculous persistence. Here, yeast two-hybrid and affinity chromatography experiments have demonstrated that Rv2623 interacts with one of the two forkhead-associated domains (FHA I) of Rv1747, a putative ATP-binding cassette transporter annotated to export lipooligosaccharides. FHA domains are signaling protein modules that mediate protein-protein interactions to modulate a wide variety of biological processes via binding to conserved phosphorylated threonine (pT)-containing oligopeptides of the interactors. Biochemical, immunochemical and mass spectrometric studies have shown that Rv2623 harbors pT and specifically identified threonine 237 as a phosphorylated residue. Relative to wild-type Rv2623 (Rv2623WT), a mutant protein in which T237 has been replaced with a non-phosphorylatable alanine (Rv2623T237A) exhibits decreased interaction with the Rv1747 FHA I domain and diminished growth-regulatory capacity. Interestingly, compared to WT bacilli, an M. tuberculosis Rv2623 null mutant (ΔRv2623) displays enhanced expression of phosphatidyl-myo-inositol mannosides (PIMs), while the ΔRv1747 mutant expresses decreased levels of PIMs. Animal studies have previously shown that ΔRv2623 is hypervirulent, while ΔRv1747 is growth-attenuated. Collectively, these data have provided evidence that Rv2623 interacts with Rv1747 to regulate mycobacterial growth; and this interaction is mediated via the recognition of the conserved Rv2623 pT237-containing FHA-binding motif by the Rv1747 FHA I domain. The divergent aberrant PIM profiles and the opposing in vivo growth phenotypes of ΔRv2623 and ΔRv1747, together with the annotated lipooligosaccharide exporter function of Rv1747, suggest that Rv2623 interacts with Rv1747 to modulate mycobacterial growth by negatively regulating the activity of Rv1747; and that Rv1747 might function as a transporter of PIMs. Because these glycolipids are major mycobacterial cell envelope components that can impact on the immune response, our findings raise the possibility that Rv2623 may regulate bacterial growth, virulence, and entry into persistence, at least in part, by modulating the levels of bacillary PIM expression, perhaps through negatively regulating the Rv1747-dependent export of the immunomodulatory PIMs to alter host-pathogen interaction, thereby influencing the fate of M. tuberculosis in vivo.

PMID:
28753640
PMCID:
PMC5549992
DOI:
10.1371/journal.ppat.1006515
[Indexed for MEDLINE]
Free PMC Article

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