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Identification of an outer membrane protease of Rickettsia rickettsii responsible for maturation of surface exposed autotransporters

ABSTRACT: Strains of R. rickettsii, the agent of Rocky Mountain spotted fever, differ greatly in the severity of the disease caused. The genetic differences responsible for this disparity are only now being uncovered. An avirulent, laboratory adapted strain of R. rickettsii fails to proteolytically process several large surface protein antigens. We have identified a protease that cleaves the protein precursors to their mature form. The gene encoding this protease is mutated in the avirulent strain. Complementation of the active form of the gene identifies proteolytic processing of surface antigens as important to virulence.

INSTRUMENT(S): Q Exactive Plus

ORGANISM(S): Rickettsia Rickettsii Str. 'sheila Smith' Rickettsia Rickettsii Str. Iowa

SUBMITTER: Yixiang Zhang

LAB HEAD: Ted Hackstadt

PROVIDER: PXD041355 | Pride | 2023-07-06

REPOSITORIES: Pride

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Project description:Phosphorylation is a regulatory mechanism by which intracellular apicomplexan parasites control the process of invading and modifying host cells. However, the sporulated oocysts’ phosphoprotein repertoires between virulent and avirulent strains of Toxoplasma gondii and the underlying mechanisms contributing to virulence is still a mystery. A quantitative analysis of the sporulated oocysts’ phosphoproteome profile of T. gondii virulent and avirulent strains belonging to different genotypes was conducted to reveal phosphoprotein expression patterns that contribute to the virulence of a particular phenotype. Phosphopeptides from the sporulated oocysts of the virulent strain PYS (Chinese ToxoDB#9) and the avirulent strain type II (PRU strain) were enriched by titanium dioxide (TiO2) affinity chromatography and quantified using iBT technology. A total of 10,645 unique phosphopeptides, 8,181 nonredundant phosphorylation sites and 2,792 phosphoproteins were identified. The quantitative analysis identified 4,129 differentially expressed phosphopeptides (DEPs) between sporulated oocysts of the PYS strain and PRU strain (|log1.5 fold change| > 1 and P < 0.05), including 2,485 upregulated and 1,644 downregulated phosphopeptides. Motif analysis identified 24 motifs from the upregulated phosphorylated peptides including 22 serine motifs and two threonine motifs (TPE and TP), and 15 motifs from the downregulated phosphorylated peptides including 12 serine motifs and three threonine motifs (TP, RxxT and KxxT) in PYS strain when comparing PYS/PRU. Several kinases were consistent with motifs of overrepresented phosphopeptides, such as PKA, PKG, CKII, IKK, MAPK, EGFR, INSR, Jak, Syk, Src, Ab1. GO analysis, KEGG pathway analysis and STRING analysis revealed differentially expressed phosphoproteins (DEPs) exhibiting significant functional properties. Kinase associated network analysis showed that AGC kinase had the greatest connected peptides. Our findings reveal significant difference in phosphopeptides of sporulated oocysts between virulent and avirulent T. gondii strains, which provides solid foundation for further exploring the mechanisms contributing to the virulence of T. gondii.

Dataset Information

Identification of an outer membrane protease of Rickettsia rickettsii responsible for maturation of surface exposed autotransporters

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