A chemosensory-like histidine kinase is dispensable for chemotaxis in vitro but regulates the virulence of Borrelia burgdorferi through modulating the stability of RpoS

Authors

Ching Wooen Sze, Department of Oral Craniofacial Molecular Biology, Virginia Commonwealth University, Richmond, Virginia, United States of America.
Kai Zhang, Department of Oral Craniofacial Molecular Biology, Virginia Commonwealth University, Richmond, Virginia, United States of America.
Michael J. Lynch, Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York, United States of America.
Radha Iyer, Department of Pathology, Microbiology, and Immunology, New York Medical College, Valhalla, New York, United States of America.
Brian R. Crane, Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York, United States of America.
Ira Schwartz, Department of Pathology, Microbiology, and Immunology, New York Medical College, Valhalla, New York, United States of America.Follow
Chunhao Li, Department of Oral Craniofacial Molecular Biology, Virginia Commonwealth University, Richmond, Virginia, United States of America.

Author Type(s)

Faculty

DOI

10.1371/journal.ppat.1011752

Journal Title

PLoS Pathogens

First Page

e1011752

Document Type

Article

Publication Date

11-1-2023

Department

Pathology, Microbiology and Immunology

Abstract

As an enzootic pathogen, the Lyme disease bacterium Borrelia burgdorferi possesses multiple copies of chemotaxis proteins, including two chemotaxis histidine kinases (CHK), CheA1 and CheA2. Our previous study showed that CheA2 is a genuine CHK that is required for chemotaxis; however, the role of CheA1 remains mysterious. This report first compares the structural features that differentiate CheA1 and CheA2 and then provides evidence to show that CheA1 is an atypical CHK that controls the virulence of B. burgdorferi through modulating the stability of RpoS, a key transcriptional regulator of the spirochete. First, microscopic analyses using green-fluorescence-protein (GFP) tags reveal that CheA1 has a unique and dynamic cellular localization. Second, loss-of-function studies indicate that CheA1 is not required for chemotaxis in vitro despite sharing a high sequence and structural similarity to its counterparts from other bacteria. Third, mouse infection studies using needle inoculations show that a deletion mutant of CheA1 (cheA1mut) is able to establish systemic infection in immune-deficient mice but fails to do so in immune-competent mice albeit the mutant can survive at the inoculation site for up to 28 days. Tick and mouse infection studies further demonstrate that CheA1 is dispensable for tick colonization and acquisition but essential for tick transmission. Lastly, mechanistic studies combining immunoblotting, protein turnover, mutagenesis, and RNA-seq analyses reveal that depletion of CheA1 affects RpoS stability, leading to reduced expression of several RpoS-regulated virulence factors (i.e., OspC, BBK32, and DbpA), likely due to dysregulated clpX and lon protease expression. Bulk RNA-seq analysis of infected mouse skin tissues further show that cheA1mut fails to elicit mouse tnf-α, il-10, il-1β, and ccl2 expression, four important cytokines for Lyme disease development and B. burgdorferi transmigration. Collectively, these results reveal a unique role and regulatory mechanism of CheA1 in modulating virulence factor expression and add new insights into understanding the regulatory network of B. burgdorferi.

Recommended Citation

Sze, C. W., Zhang, K., Lynch, M. J., Iyer, R., Crane, B. R., Schwartz, I., & Li, C. (2023). A chemosensory-like histidine kinase is dispensable for chemotaxis in vitro but regulates the virulence of Borrelia burgdorferi through modulating the stability of RpoS. PLoS Pathogens, 19 (11), e1011752. https://doi.org/10.1371/journal.ppat.1011752