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ESX‐1 secreted virulence factors are recognized by multiple cytosolic AAA ATPases in pathogenic mycobacteria
Author(s) -
DiGiuseppe Champion Patricia A.,
Champion Matthew M.,
Manzanillo Paolo,
Cox Jeffery S.
Publication year - 2009
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.2009.06821.x
Subject(s) - biology , virulence , cytosol , microbiology and biotechnology , secretion , virulence factor , atpase , gene , genetics , enzyme , biochemistry
Summary The ESX‐1 secretion system of Mycobacterium tuberculosis delivers bacterial virulence factors to host cells during infection. The most abundant factor, the ESAT‐6/CFP‐10 dimer, is targeted for secretion via a C‐terminal signal sequence on CFP‐10 that is recognized by the cytosolic ATPase, Rv3871. However, the selection determinants for other ESX‐1 substrates appear to be more complex. Some substrates, such as ESAT‐6, are secreted despite lacking signal sequences. Furthermore, all substrates require targeting of the other ESX‐1 secreted proteins, a distinguishing feature of this system. How ESX‐1 substrates are selected and the basis for co‐dependent secretion is unknown. Here we show that the EspC substrate interacts with Rv3868, a cytosolic AAA ATPase, through its C‐terminus. Swapping the C‐termini of EspC and CFP‐10 revealed that these signals are functionally distinct, suggesting that the proteins are targeted via interactions with different ATPases. Surprisingly, biochemical purification experiments demonstrate that these substrates and ATPases form multi‐protein complexes inside the cell and identified a new secreted substrate. By interfering with this protein interaction network, we have partially uncoupled co‐dependent substrate secretion. Our results suggest that proper functioning of the ESX‐1 pathway requires the interaction of multiple ESX‐1 substrates and components prior to their secretion. Ultimately, understanding the details of ESX‐1 targeting may allow for engineering of better vaccines to prevent tuberculosis.