The effector EmcB is a deubiquitinase that inhibits RIG-I signaling.

Eukaryotes have cytosolic surveillance systems to detect invading microorganisms and initiate protective immune responses. In turn, host-adapted pathogens have evolved strategies to modulate these surveillance systems, which can promote dissemination and persistence in the host. The obligate intracellular pathogen infects mammalian hosts without activating many innate immune sensors.

Lysosomal degradation products induce virulence.

is an intracellular pathogen that replicates in a lysosome-like vacuole through activation of a Dot/Icm-type IVB secretion system and subsequent translocation of effectors that remodel the host cell. Here a genome-wide small interfering RNA screen and reporter assay were used to identify host proteins required for Dot/Icm effector translocation. Significant, and independently validated, hits demonstrated the importance of multiple protein families required for endocytic trafficking of the -containing vacuole to the lysosome.

Effector Protein Cig2 Decreases Host Tolerance of Infection by Directing Constitutive Fusion of Autophagosomes with the Coxiella-Containing Vacuole.

Unlabelled: Coxiella burnetii replicates in an acidified lysosome-derived vacuole. Biogenesis of the Coxiella-containing vacuole (CCV) requires bacterial effector proteins delivered into host cells by the Dot/Icm secretion system. Genetic and cell biological analysis revealed that an effector protein called Cig2 promotes constitutive fusion of autophagosomes with the CCV to maintain this compartment in an autolysosomal stage of maturation.

Rickettsia actin-based motility occurs in distinct phases mediated by different actin nucleators.

Many intracellular bacterial pathogens undergo actin-based motility to promote cell-cell spread during infection [1]. For each pathogen, motility was assumed to be driven by a single actin polymerization pathway. Curiously, spotted fever group Rickettsia differ from other pathogens in possessing two actin-polymerizing proteins.

Expression of an epitope-tagged virulence protein in Rickettsia parkeri using transposon insertion.

Despite recent advances in our ability to genetically manipulate Rickettsia, little has been done to employ genetic tools to study the expression and localization of Rickettsia virulence proteins. Using a mariner-based Himar1 transposition system, we expressed an epitope-tagged variant of the actin polymerizing protein RickA under the control of its native promoter in Rickettsia parkeri, allowing the detection of RickA using commercially-available antibodies. Native RickA and epitope-tagged RickA exhibited similar levels of expression and were specifically localized to bacteria.

Rickettsia parkeri invasion of diverse host cells involves an Arp2/3 complex, WAVE complex and Rho-family GTPase-dependent pathway.

Rickettsiae are obligate intracellular pathogens that are transmitted to humans by arthropod vectors and cause diseases such as spotted fever and typhus. Although rickettsiae require the host cell actin cytoskeleton for invasion, the cytoskeletal proteins that mediate this process have not been completely described. To identify the host factors important during cell invasion by Rickettsia parkeri, a member of the spotted fever group (SFG), we performed an RNAi screen targeting 105 proteins in Drosophila melanogaster S2R+ cells.