The human gastrointestinal (GI) tract is inhabited by trillions of commensal bacteria that play crucial roles in human physiology. Chemical communication between microbes and their hosts underlies the basis of their associations The GI pathogen enterohemorrhagic E. coli (EHEC), responsible for outbreaks of bloody diarrhea worldwide, exploits cell-to-cell signaling between the gastrointestinal microbial flora and the hos as a means to gage and recognize the host environment. This signaling is predicated upon signaling molecules that are tryptophan derivatives in the colon such as the host neurotransmitter serotonin and the microbiota produced indole. Serotonin is a neurotransmitter that is primarily synthesized in the GI tract Serotonin is released into the lamina propria to activate peristalsis, secretion, and vasodilation. However, it has been recently reported that serotonin is also secreted into the lumen, but its function in this compartment remains unclear. Many functional GI disorders are associated with alterations in serotonin signaling, but the effect of serotonin signaling on bacterial-mediated GI disorders remains unknown. Although a number of bacteria and viruses have been show to influence serotonin signaling, no study has investigated the effect that serotonin has on bacterial pathogenesis. The bacterially produced tryptophan derivative indole is known to influence intestinal barrier function, and has also been shown to regulate virulence gene expression in EHEC. We identified the bacterial membrane bound histidine sensor kinase (HK) CpxA as a sensor of serotonin and indole. CpxA is the HK that upon autophosphorylation, phosphotranfers to the response regulator (RR) CpxR, which is a transcriptional factor. CpxA also dephosphorylates this RR, and the phosphorylation state of CpxR defines which sites it binds to on its DNA targets. Through CpxA, both serotonin and indole decrease expression of the locus of enterocyte effacement (LEE) in EHEC, which encodes a type three secretion system (T3SS), effectors and an adhesin necessary for EHEC to form lesions on enterocytes leading to intestinal disease. Both serotonin and indole inhibit CpxA's autophosphorylation, consequently decreasing the expression of its targets. Altogether, these results suggest that CpxA is an important small molecule receptor crucial for cell-to-cell signaling and inhibition of virulence of GI pathogens. Accordingly, the specific aims of this application are: 1) In vitro mechanistic studies on virulence gene regulation by tryptophan derivatives. 2) Serotonin and indole signaling at the microbiota, pathogen and host cell interface. 3) Serotonin regulation of bacterial virulence in the murine GI tract.

Agency
National Institute of Health (NIH)
Institute
National Institute of Allergy and Infectious Diseases (NIAID)
Type
Research Project (R01)
Project #
5R01AI114511-05
Application #
9597220
Study Section
Host Interactions with Bacterial Pathogens Study Section (HIBP)
Program Officer
Baqar, Shahida
Project Start
2014-12-01
Project End
2020-11-30
Budget Start
2018-12-01
Budget End
2020-11-30
Support Year
5
Fiscal Year
2019
Total Cost
Indirect Cost
Name
University of Texas Sw Medical Center Dallas
Department
Microbiology/Immun/Virology
Type
Schools of Medicine
DUNS #
800771545
City
Dallas
State
TX
Country
United States
Zip Code
75390
Cameron, Elizabeth A; Curtis, Meredith M; Kumar, Aman et al. (2018) Microbiota and Pathogen Proteases Modulate Type III Secretion Activity in Enterohemorrhagic Escherichia coli. MBio 9:
Cameron, Elizabeth A; Gruber, Charley C; Ritchie, Jennifer M et al. (2018) The QseG Lipoprotein Impacts the Virulence of Enterohemorrhagic Escherichia coli and Citrobacter rodentium and Regulates Flagellar Phase Variation in Salmonella enterica Serovar Typhimurium. Infect Immun 86:
Pifer, Reed; Russell, Regan M; Kumar, Aman et al. (2018) Redox, amino acid, and fatty acid metabolism intersect with bacterial virulence in the gut. Proc Natl Acad Sci U S A 115:E10712-E10719
Carlson-Banning, Kimberly M; Sperandio, Vanessa (2018) Enterohemorrhagic Escherichia coli outwits hosts through sensing small molecules. Curr Opin Microbiol 41:83-88
Hernandez-Doria, Juan D; Sperandio, Vanessa (2018) Bacteriophage Transcription Factor Cro Regulates Virulence Gene Expression in Enterohemorrhagic Escherichia coli. Cell Host Microbe 23:607-617.e6
Parker, Christopher T; Russell, Regan; Njoroge, Jacqueline W et al. (2017) Genetic and Mechanistic Analyses of the Periplasmic Domain of the Enterohemorrhagic Escherichia coli QseC Histidine Sensor Kinase. J Bacteriol 199:
Bäumler, Andreas J; Sperandio, Vanessa (2016) Interactions between the microbiota and pathogenic bacteria in the gut. Nature 535:85-93
Kendall, Melissa M; Sperandio, Vanessa (2016) What a Dinner Party! Mechanisms and Functions of Interkingdom Signaling in Host-Pathogen Associations. MBio 7:e01748
Cameron, Elizabeth A; Sperandio, Vanessa (2015) Frenemies: Signaling and Nutritional Integration in Pathogen-Microbiota-Host Interactions. Cell Host Microbe 18:275-84
Sperandio, Vanessa (2015) Bacterial Reductionism: Host Thiols Enhance Virulence. Cell Host Microbe 18:7-8