Biology subjects

Jastrab, J. B.

Publications and source records attributed to Jastrab, J. B..

3 recordsLinked to original sources

bioRxiv2025

Wall teichoic acid is required for DNA-triggered innate immune receptor activation by Staphylococcus aureus

Receptors that stimulate inflammation are commonly activated by ligands that are buried within microbial cells. The mechanisms that facilitate immunostimulatory ligand release from microbes during infection are largely undefined. Using the pathogen Staphylococcus aureus, we describe wall teichoic acid (WTA) as a critical mediator of DNA release from bacterial cells during infection. Mechanistically, we found that the -glycosylated form of WTA, generated by the enzyme TarM, is the primary mediator of bacterial DNA release within macrophages. This process is antagonized by the enzyme O-acetyltransferase, which prevents WTA attachment to peptidoglycan. This competition among peptidoglycan modifying enzymes determines activation of cytosolic DNA receptors AIM2 and cGAS. WTA therefore operates as a meta-regulator of inflammation, by controlling the availability of microbial ligands that stimulate innate immunity.

immunology↗

bioRxiv2018

The Mycobacterium tuberculosis Pup-proteasome system regulates nitrate metabolism through an essential protein quality control system

The human pathogen Mycobacterium tuberculosis (M. tuberculosis) encodes a proteasome that carries out regulated degradation of bacterial proteins. It has been proposed that the proteasome contributes to nitrogen metabolism in M. tuberculosis, although this hypothesis had not been tested. Upon assessing M. tuberculosis growth in several nitrogen sources, we found that a mutant strain lacking the Mycobacterium proteasomal activator Mpa was unable to use nitrate as a sole nitrogen source due to a specific failure in the pathway of nitrate reduction to ammonium. We found that the robust activity by the nitrite reductase complex NirBD depended on expression of the groEL/groES chaperonin genes, which are regulated by the repressor HrcA. We identified HrcA as a likely proteasome substrate, and propose that the degradation of HrcA is required for the full expression of chaperonin genes. Furthermore, our data suggest that degradation of HrcA, along with numerous other proteasome substrates, is enhanced during growth in nitrate to facilitate the de-repression of the chaperonin genes. Importantly, growth in nitrate is the first example of a specific condition that reduces the steady-state levels of numerous proteasome substrates in M. tuberculosis.\n\nSIGNIFICANCE STATEMENTThe proteasome is required for the full virulence of M. tuberculosis. However, the extent of its role as a regulator of bacterial physiology remains unclear. In this work, we demonstrate a novel function of the proteasome system in maintaining the expression of essential chaperonin genes. This activity by the proteasome is required for M. tuberculosis to use nitrate as a nitrogen source. Furthermore, we identified a specific growth condition that robustly decreases the abundance of pupylated proteins. This observation strongly suggests the presence of a yet-to-be-determined mechanism of control over the Pup-proteasome system in M. tuberculosis that is induced in nitrate.

microbiology↗

bioRxiv2018

Proteasome Substrate Capture and Gate Activation by Mycobacterium tuberculosis PafE

In all domains of life, proteasomes are gated chambered proteases that require opening by activators in order to facilitate protein degradation. Twelve proteasome accessory factor E (PafE) monomers assemble into a single, dodecameric ring to promote proteolysis that is required for the full virulence of the human bacterial pathogen Mycobacterium tuberculosis. While the best characterized proteasome activators use ATP to deliver proteins into a proteasome, PafE does not require ATP. In order to understand the mechanism of PafE-mediated protein targeting and proteasome activation, we studied the interactions of PafE with native substrates, including a newly identified proteasome substrate, Rv3213c, and with proteasome core particles. We characterized the function of a highly conserved feature conserved in bacterial proteasome activator proteins: a glycine-glutamine-tyrosine-leucine or \"GQYL\" motif at their carboxyl-termini that is essential to stimulate proteolysis. Using cryo-electron microscopy, we found that the GQYL motif of PafE interacts with specific residues in the -subunits of the proteasome core particle to trigger gate opening and degradation. Finally, we found that PafE rings have 40-[A] openings lined with hydrophobic residues that form a chamber for capturing substrates prior to the onset of degradation. This result suggests PafE has a previously unrecognized chaperone activity. Collectively, our data provide new insights on the mechanistic understanding of ATP-independent proteasome degradation in bacteria.

biochemistry↗