Numerous regulatory genes and environmental cues that influence Streptococcus pyogenes virulence gene regulation in vitro have been identified. However, very little is currently known as to how these signals are sensed, how different regulatory pathways interact and whether these cues are relevant in vivo. These are important questions, as differential regulation in response to compartment-specific cues may determine whether infection proceeds to a self-limiting or tissue-destructive outcome, an issue that is only very poorly understood for S. pyogenes. To gain insight into these questions, my lab has focused on regulation of speB, which encodes the secreted SpeB cysteine protease. We defined a set of in vitro conditions, including growth phase, pH, Cl- anion concentration and a carbohydrate-poor/peptide rich nutritional environment, that reflects expression patterns measured in vivo. Mutagenesis to identify a regulatory factor that could coordinate speB regulation in response to each of these cues resulted in the discovery of LacD.1, a tagatose aldolase that acts to repress speB transcription. Interestingly, S. pyogenes and several other Gram-positive pathogens contain two lactose operons (Lac.1 and Lac.2) where several of the genes encoding enzymes upstream of LacD.1, but not LacD.2, in the catabolic pathway are missing or are pseudogenes, suggesting that Lac.2 is involved in catabolism and that Lac.1 has evolved to a regulatory function. Consistent with this, LacD.2 has no regulatory phenotype and cannot complement the regulatory phenotype of LacD.1 and mutations that disrupt the catalytic center of LacD.1 do not alter its regulatory function;however, other mutations that may alter its ability to bind substrate do ablate regulation. Furthermore, we have shown that LacD.1 forms a complex in vivo with RopB, a DMA-binding protein and a known regulator of transcription and other metabolic genes. RopB is a member of the Rgg-family of transcription regulators broadly distributed among Gram-positive pathogens and virtually nothing is known about how this important family of regulators interacts with signal transduction systems. Based on examples of how other aldolases and sugar catabolic enzymes have been adapted to regulatory functions, these data suggest the following model for LacD.1 function: 1. That LacD.1 has been adapted as a sensor of intermediary metabolism;2. That under carbohydrate-rich conditions, binding its substrate allows LacD.1 to act as an """"""""anti-activator"""""""" and sequester RopB in an inactive form;3. That LacD.1 may play a broader role in carbon catabolite repression and virulence gene expression;and 4. that LacD.1 is important for virulence. This project will explore these questions

Agency
National Institute of Health (NIH)
Institute
National Institute of Allergy and Infectious Diseases (NIAID)
Type
Research Project (R01)
Project #
5R01AI070759-05
Application #
8084162
Study Section
Bacterial Pathogenesis Study Section (BACP)
Program Officer
GU, Xin-Xing
Project Start
2007-07-01
Project End
2013-06-30
Budget Start
2011-07-01
Budget End
2013-06-30
Support Year
5
Fiscal Year
2011
Total Cost
$328,826
Indirect Cost
Name
Washington University
Department
Microbiology/Immun/Virology
Type
Schools of Medicine
DUNS #
068552207
City
Saint Louis
State
MO
Country
United States
Zip Code
63130
Cusumano, Zachary T; Caparon, Michael G (2015) Citrulline protects Streptococcus pyogenes from acid stress using the arginine deiminase pathway and the F1Fo-ATPase. J Bacteriol 197:1288-96
Port, Gary C; Paluscio, Elyse; Caparon, Michael G (2015) Complete Genome Sequences of emm6 Streptococcus pyogenes JRS4 and Parental Strain D471. Genome Announc 3:
Paluscio, Elyse; Caparon, Michael G (2015) Streptococcus pyogenes malate degradation pathway links pH regulation and virulence. Infect Immun 83:1162-71
Cusumano, Zachary T; Watson Jr, Michael E; Caparon, Michael G (2014) Streptococcus pyogenes arginine and citrulline catabolism promotes infection and modulates innate immunity. Infect Immun 82:233-42
Cusumano, Zachary; Caparon, Michael (2013) Adaptive evolution of the Streptococcus pyogenes regulatory aldolase LacD.1. J Bacteriol 195:1294-304
Watson Jr, Michael E; Nielsen, Hailyn V; Hultgren, Scott J et al. (2013) Murine vaginal colonization model for investigating asymptomatic mucosal carriage of Streptococcus pyogenes. Infect Immun 81:1606-17
Kietzman, Colin C; Caparon, Michael G (2011) Distinct time-resolved roles for two catabolite-sensing pathways during Streptococcus pyogenes infection. Infect Immun 79:812-21
Kietzman, Colin C; Caparon, Michael G (2010) CcpA and LacD.1 affect temporal regulation of Streptococcus pyogenes virulence genes. Infect Immun 78:241-52
Weston, Benjamin F; Brenot, Audrey; Caparon, Michael G (2009) The metal homeostasis protein, Lsp, of Streptococcus pyogenes is necessary for acquisition of zinc and virulence. Infect Immun 77:2840-8