ESX-1 secreted virulence factors are recognized by multiple cytosolic AAA ATPases in pathogenic mycobacteria.
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.
Champion
Patricia A DiGiuseppe
PA
Department of Microbiology and Immunology, University of California, San Francisco, San Francisco, CA 94143-2200, USA.
Champion
Matthew M
MM
Manzanillo
Paolo
P
Cox
Jeffery S
JS
D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000595:Amino Acid Sequence; D000942:Antigens, Bacterial / Q000378:metabolism; D001426:Bacterial Proteins / Q000378:metabolism*; D008954:Models, Biological; D008969:Molecular Sequence Data; D009169:Mycobacterium tuberculosis / Q000378:metabolism*; D055503:Protein Multimerization; D021381:Protein Transport; D037521:Virulence Factors / Q000378:metabolism*
D000942:Antigens, Bacterial; D001426:Bacterial Proteins; C117940:CFP-10 protein, Mycobacterium tuberculosis; C093276:ESAT-6 protein, Mycobacterium tuberculosis; D037521:Virulence Factors; D000251:Adenosine Triphosphatases
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