Biology subjects

Burke, T. P.

Publications and source records attributed to Burke, T. P..

3 recordsLinked to original sources

bioRxiv2020

Lysine methylation shields an intracellular pathogen from ubiquitylation

Many intracellular pathogens avoid detection by their host cells. However, it remains unknown how they avoid being tagged by ubiquitin, an initial step leading to anti-microbial autophagy. Here, we show that the intracellular bacterial pathogen Rickettsia parkeri uses two protein-lysine methyltransferases (PKMTs) to modify outer membrane proteins (OMPs) and prevent their ubiquitylation. Mutants deficient in the PKMTs were avirulent in mice and failed to grow in macrophages due to ubiquitylation and autophagy. Analysis of the lysine-methylome revealed that PKMTs modify a subset of OMPs by methylation at the same sites that are recognized by host ubiquitin. These findings show that lysine methylation is an essential determinant of rickettsial pathogenesis that shields bacterial proteins from ubiquitylation to evade autophagic targeting.

microbiology↗

bioRxiv2020

Rickettsia parkeri Sca2 promotes dissemination in an intradermal infection mouse model

Rickettsia are arthropod-borne pathogens that cause severe human disease worldwide. The spotted fever group (SFG) pathogen Rickettsia parkeri elicits skin lesion (eschar) formation in humans after tick bite. However, intradermal inoculation of inbred mice with millions of bacteria fails to elicit eschar formation or disseminated disease, hindering investigations into understanding eschar-associated rickettsiosis. Here, we report that intradermal infection of mice deficient for both interferon receptors (Ifnar-/-Ifngr-/-) with R. parkeri causes eschar formation, recapitulating the hallmark clinical feature of human disease. Intradermal infection with doses that recapitulate tick infestation caused eschar formation and lethality, including with as few as 10 bacteria. Using this model, we found that the actin-based motility protein Sca2 is required for R. parkeri dissemination from the skin to internal organs and for causing lethal disease, and that the abundant R. parkeri outer membrane protein OmpB contributes to eschar formation. We also found that immunizing mice with sca2 and ompB mutant R. parkeri protects against subsequent rechallenge with wild-type bacteria, revealing live-attenuated vaccine candidates. Thus, interferon receptor-deficient mice are a tractable model to investigate rickettsiosis, bacterial virulence factors, and immunity. Our results suggest that differences in interferon signaling in the skin between mice and humans may explain the discrepancy in susceptibility to SFG Rickettsia.

microbiology↗

bioRxiv2019

Inflammasome-mediated antagonism of type I interferon enhances Rickettsia pathogenesis

Inflammasomes and interferons constitute two critical arms of innate immunity. Most facultative bacterial pathogens that inhabit the host cell cytosol avoid activating inflammasomes and are often resistant to killing by type I interferon (IFN-I). We report that the human pathogen Rickettsia parkeri, an obligate intracellular pathogen that resides in the cytosol, is sensitive to IFN-I. The mechanism of IFN-I-dependent restriction requires the transcription factor IRF5, which upregulates anti-rickettsial factors including guanylate-binding proteins and iNOS. However, R. parkeri curtails cGAS-dependent IFN-I production by causing caspase-11-dependent pyroptosis. In vivo, inflammasome activation antagonizes IFN-I production, enhancing R. parkeri abundance in the spleen. Mice lacking either IFN-I or IFN-{gamma} signaling are resistant to infection, but mice lacking both rapidly succumb, revealing that both interferons are required to control R. parkeri. This study illuminates how an obligate cytosolic pathogen exploits the intrinsic trade-off between cell death and cytokine production to escape killing by innate immunity.\n\nHighlightsO_LIRickettsia killed by GBPs activates caspase-11 and GSDMD, promoting pyroptosis\nC_LIO_LIRickettsia exploits pyroptosis to avoid cGAS-dependent type I interferon\nC_LIO_LIIRF5, GBPs, and iNOS contribute to controlling R. parkeri infection\nC_LIO_LIIfnar-/-Ifngr-/- mice succumb to infection, uncovering a mouse model to study R. parkeri\nC_LI

immunology↗