TY - JOUR
T1 - Separable roles for Mycobacterium tuberculosis ESX-3 effectors in iron acquisition and virulence
AU - Tufariello, Jo Ann M.
AU - Chapman, Jessica R.
AU - Kerantzas, Christopher A.
AU - Wong, Ka Wing
AU - Vilchèze, Catherine
AU - Jones, Christopher M.
AU - Cole, Laura E.
AU - Tinaztepe, Emir
AU - Thompson, Victor
AU - Fenyö, David
AU - Niederweis, Michael
AU - Ueberheide, Beatrix
AU - Philips, Jennifer A.
AU - Jacobs, William R.
N1 - Funding Information:
We thank Bing Chen, Mei Chen, and John Kim for assistance with mouse infections; Annie Dai for phage preparation; Colin Ratledge for providing mycobactins; Brian Weinrick for mutant verification by whole genome sequencing; Michelle Larsen and Anthony Orth for sharing constructs from the Genomics Institute of the Novartis Research Foundation phasmid collection; Katherine Moccia and Eva Yang for assistance with strain generation and verification; and members of the W.R.J. and J.A.P. laboratories for numerous helpful discussions. This work was supported by NIH Grants AI26170 and AI098925 (to W.R.J.) and T32GM007288 for support of C.A.K. at the Albert Einstein College of Medicine; and NIH Grant AI087682 and funds from the New York University School of Medicine (to J.A.P.).
PY - 2016/1/19
Y1 - 2016/1/19
N2 - Mycobacterium tuberculosis (Mtb) encodes five type VII secretion systems (T7SS), designated ESX-1-ESX-5, that are critical for growth and pathogenesis. The best characterized is ESX-1, which profoundly impacts host cell interactions. In contrast, the ESX-3 T7SS is implicated in metal homeostasis, but efforts to define its function have been limited by an inability to recover deletion mutants. We overcame this impediment using medium supplemented with various iron complexes to recover mutants with deletions encompassing select genes within esx-3 or the entire operon. The esx-3 mutants were defective in uptake of siderophore-bound iron and dramatically accumulated cell-associated mycobactin siderophores. Proteomic analyses of culture filtrate revealed that secretion of EsxG and EsxH was codependent and that EsxG-EsxH also facilitated secretion of several members of the proline-glutamic acid (PE) and proline-proline-glutamic acid (PPE) protein families (named for conserved PE and PPE N-terminalmotifs). Substrates that depended on EsxG-EsxH for secretion included PE5, encoded within the esx-3 locus, and the evolutionarily related PE15-PPE20 encoded outside the esx-3 locus. In vivo characterization of the mutants unexpectedly showed that the ESX-3 secretion system plays both irondependent and -independent roles in Mtb pathogenesis. PE5-PPE4 was found to be critical for the siderophore-mediated iron-acquisition functions of ESX-3. The importance of this iron-acquisition function was dependent upon host genotype, suggesting a role for ESX-3 secretion in counteracting host defense mechanisms that restrict iron availability. Further, we demonstrate that the ESX-3 T7SS secretes certain effectors that are important for iron uptake while additional secreted effectors modulate virulence in an iron-independent fashion.
AB - Mycobacterium tuberculosis (Mtb) encodes five type VII secretion systems (T7SS), designated ESX-1-ESX-5, that are critical for growth and pathogenesis. The best characterized is ESX-1, which profoundly impacts host cell interactions. In contrast, the ESX-3 T7SS is implicated in metal homeostasis, but efforts to define its function have been limited by an inability to recover deletion mutants. We overcame this impediment using medium supplemented with various iron complexes to recover mutants with deletions encompassing select genes within esx-3 or the entire operon. The esx-3 mutants were defective in uptake of siderophore-bound iron and dramatically accumulated cell-associated mycobactin siderophores. Proteomic analyses of culture filtrate revealed that secretion of EsxG and EsxH was codependent and that EsxG-EsxH also facilitated secretion of several members of the proline-glutamic acid (PE) and proline-proline-glutamic acid (PPE) protein families (named for conserved PE and PPE N-terminalmotifs). Substrates that depended on EsxG-EsxH for secretion included PE5, encoded within the esx-3 locus, and the evolutionarily related PE15-PPE20 encoded outside the esx-3 locus. In vivo characterization of the mutants unexpectedly showed that the ESX-3 secretion system plays both irondependent and -independent roles in Mtb pathogenesis. PE5-PPE4 was found to be critical for the siderophore-mediated iron-acquisition functions of ESX-3. The importance of this iron-acquisition function was dependent upon host genotype, suggesting a role for ESX-3 secretion in counteracting host defense mechanisms that restrict iron availability. Further, we demonstrate that the ESX-3 T7SS secretes certain effectors that are important for iron uptake while additional secreted effectors modulate virulence in an iron-independent fashion.
KW - ESX-3
KW - Mycobacterium tuberculosis
KW - Mycobactin
KW - Siderophore
KW - Type VII secretion system
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U2 - 10.1073/pnas.1523321113
DO - 10.1073/pnas.1523321113
M3 - Article
C2 - 26729876
AN - SCOPUS:84955084428
SN - 0027-8424
VL - 113
SP - E348-E357
JO - Proceedings of the National Academy of Sciences of the United States of America
JF - Proceedings of the National Academy of Sciences of the United States of America
IS - 3
ER -
