BopC is a type III secreted effector protein of Burkholderia pseudomallei
Sunsiree Muangman1, Sunee Korbsrisate, Veerachat Muangsombut
1Department of Immunology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand.
Abstract:
Burkholderia pseudomallei, the causative agent of melioidosis, exploits the Bsa type III secretion system (T3SS) to deliver effector proteins into host cells. These effectors manipulate host cell functions; thus, contributing to the ability of the bacteria to evade the immune response and cause disease. Only two Bsa-secreted effectors have been conclusively identified to date. Here, we report the identification of the third B. pseudomallei type III secreted effector protein, designated BopC. BopC is encoded by the bpss1516 gene abutting bpss1517, which encodes its putative chaperone. The genes are located in the close proximity to the bsa T3SS gene cluster of B. pseudomallei K96243 (Fig. 1). BopC was secreted into culture supernatant by the wild-type B. pseudomallei strain, but its secretion was abolished in the bsaZ T3SS mutant. Using pull down and co-purification assays, we confirmed that BopC interacts with its putative chaperone, BPSS1517, in vitro. Furthermore, the first 20 N-terminal amino acids of BopC were found to be sufficient to mediate the T3SS-dependent translocation of a reporter protein from a heterologous enteropathogenic Escherichia coli host into mammalian cells. Finally, bopC mutant was found to be less invasive than the wild-type strain in the epithelial cells.
Insights
Researchers identified BopC, the third effector protein secreted by Burkholderia pseudomallei's Bsa type III secretion system (T3SS). This discovery advances understanding of melioidosis pathogenesis and bacterial immune evasion strategies.
Area of Science:
- Microbiology
- Bacterial Pathogenesis
- Molecular Biology
Background:
- Burkholderia pseudomallei causes melioidosis by injecting effector proteins into host cells via the Bsa type III secretion system (T3SS).
- Understanding these effectors is crucial for deciphering bacterial virulence and immune evasion mechanisms.
- Previously, only two Bsa-secreted effectors were identified.
Purpose of the Study:
- To identify and characterize novel effector proteins secreted by the Bsa T3SS of Burkholderia pseudomallei.
- To investigate the role of the newly identified effector, BopC, in bacterial virulence and host cell interaction.
Main Methods:
- Identification of BopC through analysis of secreted proteins from wild-type and T3SS mutant strains.
- Confirmation of BopC-chaperone interaction using in vitro pull-down and co-purification assays.
- Functional analysis of BopC translocation and its impact on bacterial invasion using reporter assays and mutant strains.
Main Results:
- BopC was identified as the third Bsa-T3SS secreted effector protein, encoded by bpss1516.
- BopC interacts with its putative chaperone, BPSS1517.
- The N-terminus of BopC mediates T3SS-dependent translocation, and a bopC mutant exhibits reduced invasion of epithelial cells.
Conclusions:
- BopC is a novel effector protein secreted by the B. pseudomallei Bsa T3SS.
- BopC contributes to the virulence of B. pseudomallei, specifically influencing bacterial invasion.
- This finding expands the known repertoire of Bsa T3SS effectors and their roles in melioidosis.
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