TY - JOUR
T1 - A membrane-depolarizing toxin substrate of the Staphylococcus aureus type VII secretion system mediates intraspecies competition
AU - Ulhuq, Fatima R.
AU - Gomes, Margarida C.
AU - Duggan, Gina M.
AU - Guo, Manman
AU - Mendonca, Chriselle
AU - Buchanan, Grant
AU - Chalmers, James D.
AU - Cao, Zhenping
AU - Kneuper, Holger
AU - Murdoch, Sarah
AU - Thomson, Sarah
AU - Strahl, Henrik
AU - Trost, Matthias
AU - Mostowy, Serge
AU - Palmer, Tracy
N1 - Copyright © 2020 the Author(s). Published by PNAS.
PY - 2020/8/25
Y1 - 2020/8/25
N2 - The type VII protein secretion system (T7SS) is conserved across Staphylococcus aureus strains and plays important roles in virulence and interbacterial competition. To date, only one T7SS substrate protein, encoded in a subset of S. aureus genomes, has been functionally characterized. Here, using an unbiased proteomic approach, we identify TspA as a further T7SS substrate. TspA is encoded distantly from the T7SS gene cluster and is found across all S. aureus strains as well as in Listeria and Enterococci. Heterologous expression of TspA from S. aureus strain RN6390 indicates its C-terminal domain is toxic when targeted to the Escherichia coli periplasm and that it depolarizes the cytoplasmic membrane. The membrane-depolarizing activity is alleviated by coproduction of the membrane-bound TsaI immunity protein, which is encoded adjacent to tspA on the S. aureus chromosome. Using a zebrafish hindbrain ventricle infection model, we demonstrate that the T7SS of strain RN6390 promotes bacterial replication in vivo, and deletion of tspA leads to increased bacterial clearance. The toxin domain of TspA is highly polymorphic and S. aureus strains encode multiple tsaI homologs at the tspA locus, suggestive of additional roles in intraspecies competition. In agreement, we demonstrate TspA-dependent growth inhibition of RN6390 by strain COL in the zebrafish infection model that is alleviated by the presence of TsaI homologs.
AB - The type VII protein secretion system (T7SS) is conserved across Staphylococcus aureus strains and plays important roles in virulence and interbacterial competition. To date, only one T7SS substrate protein, encoded in a subset of S. aureus genomes, has been functionally characterized. Here, using an unbiased proteomic approach, we identify TspA as a further T7SS substrate. TspA is encoded distantly from the T7SS gene cluster and is found across all S. aureus strains as well as in Listeria and Enterococci. Heterologous expression of TspA from S. aureus strain RN6390 indicates its C-terminal domain is toxic when targeted to the Escherichia coli periplasm and that it depolarizes the cytoplasmic membrane. The membrane-depolarizing activity is alleviated by coproduction of the membrane-bound TsaI immunity protein, which is encoded adjacent to tspA on the S. aureus chromosome. Using a zebrafish hindbrain ventricle infection model, we demonstrate that the T7SS of strain RN6390 promotes bacterial replication in vivo, and deletion of tspA leads to increased bacterial clearance. The toxin domain of TspA is highly polymorphic and S. aureus strains encode multiple tsaI homologs at the tspA locus, suggestive of additional roles in intraspecies competition. In agreement, we demonstrate TspA-dependent growth inhibition of RN6390 by strain COL in the zebrafish infection model that is alleviated by the presence of TsaI homologs.
KW - type VII secretion system
KW - Staphylococcus aureus
KW - zebrafish
KW - membrane-depolarizing toxin
KW - bacterial competition
KW - Bacterial competition
KW - Type VII secretion system
KW - Zebrafish
KW - Membrane-depolarizing toxin
UR - http://www.scopus.com/inward/record.url?scp=85090069771&partnerID=8YFLogxK
U2 - 10.1073/pnas.2006110117
DO - 10.1073/pnas.2006110117
M3 - Article
C2 - 32769205
VL - 117
SP - 20836
EP - 20847
JO - Proceedings of the National Academy of Sciences
JF - Proceedings of the National Academy of Sciences
SN - 0027-8424
IS - 34
ER -