Borrelia burgdorferi (Bb), the agent of Lyme disease (LD), is maintained in nature within a complex enzootic cycle involving a mammalian reservoir host and a tick vector. To sustain this cycle, Bb must adjust its transcriptome, proteome, and metabolome to arthropod- and mammalian host-derived signals as it shuttles between the two. The Rrp2/RpoN/RpoS pathway has gained widespread recognition as a central player in borrelial gene regulation. Our laboratory has long been at the forefront of efforts to characterize the cohort of genes controlled by RpoS in both the tick and mammal. Unfortunately, we still do not know the entire output of RpoS-RNA polymerase (RNAP) holoenzyme in nature. The present proposal addresses this shortfall by combining state-of-the-art transcriptomic and mutagenesis methodologies to determine where/when individual genes contribute to RpoS's dual-host `mission'. In prior publications, we were instrumental in delineating the temporal boundaries of the RpoS-ON and ?OFF states in vivo. In recent years, however, our thinking about this dichotomy has become much more nuanced. We now believe that the contours of the RpoS regulon change profoundly and in host-specific fashion during the RpoS-ON state These results, in concert with studies of the Hk1/Rrp1 pathway, give rise to our central hypothesis--the dynamic nature of the RpoS regulon reflects the confluence of non-RpoS regulatory pathways with mechanisms that govern the ON/OFF states of RpoS and the output of RpoS-RNAP. Along these lines, we now propose that the tick-phase signaling molecule c-di-GMP is crucial to this regulatory cross-talk. Moreover, we and others have found that the c-di-GMP-binding protein PlzA promotes expression of RpoS and, hence, Bb virulence in the mouse, the stage of the enzootic cycle in which the Hk1/Rrp1 pathway is OFF. Our efforts to clarify this bifunctional role of PlzA as a mediator of c-di-GMP signaling in ticks and a c-di-GMP-independent regulator of RpoS in mice takes our field into uncharted territory. Lastly, in years past, our analysis of mammalian host-adapted spirochetes cultivated in dialysis membrane chambers revealed that RpoS not only upregulates genes required for tick transmission and mammalian infection but also represses genes required for colonization and adaptation to the tick. Our recent work suggests that RpoS-RNAP directly represses transcription of tick-phase genes by occluding their ?70 promoters. We will test this `RpoS as repressor' model and explore new data that c-di-GMP antagonizes RpoS-mediated repression in mammalian host-adapted Bb. Our long-term objective is to achieve an integrative understanding of how the Rrp2/RpoN/RpoS pathway fulfills its essential mission--guiding LD spirochetes from tick to mouse and back again. We will accomplish this by defining the contours of the RpoS regulon in ticks and mice (Aim 1); clarifying the convergence of c-di-GMP- and PlzA-dependent signaling with the RpoS pathway (Aim 2); and dissecting RpoS-mediated repression of tick-phase genes and its antagonism by c-di-GMP in mammalian host-adapted Bb (Aim 3).

Public Health Relevance

Borrelia burgdorferi (Bb), the causative agent of Lyme disease, is maintained in nature by an enzootic cycle that involves an Ixodes tick vector and a mammalian host, typically wild rodents. Since its discovery, the Rrp2/RpoN/RpoS pathway has gained widespread recognition as a central player in borrelial gene regulation, tick transmission, and virulence. The experiments in our proposal will define more precisely how and where RpoS-dependent genes function in ticks and mice and how the convergence of non-RpoS pathways, particularly those involving cyclic di-GMP and PlzA, contribute to its many layers of regulation.

Agency
National Institute of Health (NIH)
Institute
National Institute of Allergy and Infectious Diseases (NIAID)
Type
Research Project (R01)
Project #
5R01AI029735-29
Application #
9991719
Study Section
Bacterial Pathogenesis Study Section (BACP)
Program Officer
Ilias, Maliha R
Project Start
1990-04-01
Project End
2023-08-31
Budget Start
2020-09-01
Budget End
2021-08-31
Support Year
29
Fiscal Year
2020
Total Cost
Indirect Cost
Name
University of Connecticut
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
022254226
City
Farmington
State
CT
Country
United States
Zip Code
06030
Caimano, Melissa J (2018) Generation of Mammalian Host-Adapted Borrelia burgdorferi by Cultivation in Peritoneal Dialysis Membrane Chamber Implantation in Rats. Methods Mol Biol 1690:35-45
Nally, Jarlath E; Grassmann, Andre A; Planchon, Sébastien et al. (2017) Pathogenic Leptospires Modulate Protein Expression and Post-translational Modifications in Response to Mammalian Host Signals. Front Cell Infect Microbiol 7:362
Hawley, Kelly L; Cruz, Adriana R; Benjamin, Sarah J et al. (2017) IFN? Enhances CD64-Potentiated Phagocytosis of Treponema pallidum Opsonized with Human Syphilitic Serum by Human Macrophages. Front Immunol 8:1227
Grove, Arianna P; Liveris, Dionysios; Iyer, Radha et al. (2017) Two Distinct Mechanisms Govern RpoS-Mediated Repression of Tick-Phase Genes during Mammalian Host Adaptation by Borrelia burgdorferi, the Lyme Disease Spirochete. MBio 8:
Puthenveetil, Robbins; Kumar, Sanjiv; Caimano, Melissa J et al. (2017) The major outer sheath protein forms distinct conformers and multimeric complexes in the outer membrane and periplasm of Treponema denticola. Sci Rep 7:13260
Groshong, Ashley M; Dey, Abhishek; Bezsonova, Irina et al. (2017) Peptide Uptake Is Essential for Borrelia burgdorferi Viability and Involves Structural and Regulatory Complexity of its Oligopeptide Transporter. MBio 8:
Miller, Daniel P; Oliver Jr, Lee D; Tegels, Brittney K et al. (2016) The Treponema denticola FhbB Protein Is a Dominant Early Antigen That Elicits FhbB Variant-Specific Antibodies That Block Factor H Binding and Cleavage by Dentilisin. Infect Immun 84:2051-2058
Caimano, Melissa J; Drecktrah, Dan; Kung, Faith et al. (2016) Interaction of the Lyme disease spirochete with its tick vector. Cell Microbiol 18:919-27
Kenedy, Melisha R; Scott 2nd, Edgar J; Shrestha, Binu et al. (2016) Consensus computational network analysis for identifying candidate outer membrane proteins from Borrelia spirochetes. BMC Microbiol 16:141
Gulia-Nuss, Monika; Nuss, Andrew B; Meyer, Jason M et al. (2016) Genomic insights into the Ixodes scapularis tick vector of Lyme disease. Nat Commun 7:10507

Showing the most recent 10 out of 98 publications