A protein–protein interaction map reveals that the Coxiella burnetii effector CirB inhibits host proteasome activity

Abstract

Coxiella burnetii is the etiological agent of the zoonotic disease Q fever, which is featured by its ability to replicate in acid vacuoles resembling the lysosomal network. One key virulence determinant of C. burnetii is the Dot/Icm system that transfers more than 150 effector proteins into host cells. These effectors function to construct the lysosome-like compartment permissive for bacterial replication, but the functions of most of these effectors remain elusive. In this study, we used an affinity tag purification mass spectrometry (AP-MS) approach to generate a C. burnetii-human protein-protein interaction (PPI) map involving 53 C. burnetii effectors and 3480 host proteins. This PPI map revealed that the C. burnetii effector CBU0425 (designated CirB) interacts with most subunits of the 20S core proteasome. We found that ectopically expressed CirB inhibits hydrolytic activity of the proteasome. In addition, overexpression of CirB in C. burnetii caused dramatic inhibition of proteasome activity in host cells, while knocking down CirB expression alleviated such inhibitory effects. Moreover, we showed that a region of CirB that spans residues 91–120 binds to the proteasome subunit PSMB5 (beta 5). Finally, PSMB5 knockdown promotes C. burnetii virulence, highlighting the importance of proteasome activity modulation during the course of C. burnetii infection.

The endogenous Coxiella burnetii plasmid encodes a functional toxin–antitoxin system

“…This result indicated that the inducible CRISPRi system could target genes essential for intracellular infection and small SCV‐specific genes. Constitutive CRISPRi knockdown of the Dot/Icm substrate CirB in C. burnetii was recently described (Fu et al, 2022 ). This shuttle vector‐based system adopts an always‐on approach using the cbu1169 promoter to drive both sgRNA and dcas9 expression.…”

“…The CRISPRi system was first tested by knocking down the production of the host cell essential Dot/Icm protein IcmD (Figure S1) and then by simultaneously knocking down both IcmD and the small SCV-specific protein ScvA production (39 amino acids) (Figure S2). This result indicated that the inducible CRISPRi system could target genes essential for intracel- described (Fu et al, 2022). This shuttle vector-based system adopts an always-on approach using the cbu1169 promoter to drive both sgRNA and dcas9 expression.…”

Skin infectome of patients with a tick bite history

“…However, we cannot determine whether the detected bacteria were in the tick or on the tick, or whether pathogens or bacteria were transmitted from the tick's surface. In addition, excluding known bacterial pathogens, such as the spotted fever group rickettsia C. burnetii (Huang et al, 2021;Fu et al, 2022), a potentially new pathogen, R. cervicalis, was detected in both the blood and skin samples of patients. Although more than 10 viral families were found in ticks by RNA-seq in our previous study (Li et al, 2021), only three viruses (i.e., JMTV, BLTV4, and DTMV) could be detected in skin biopsy specimens.…”

A toxin-antitoxin system ensures plasmid stability in Coxiella burnetii

“…This result indicated that the inducible CRISPRi system could target genes essential for intracellular infection and small SCV- specific genes. Constitutive CRISPRi knockdown of the Dot/Icm substrate CirB in C. burnetii was recently described (Fu et al, 2022). This shuttle vector-based system adopts an always on approach using the cbu1169 promoter to drive both sgRNA and dcas9 expression.…”