GPCR signaling cascades in Cryptococcus neoformans

Summary

Principal Investigator: JOSEPH B HEITMAN
Abstract: [unreadable] DESCRIPTION (provided by applicant): Cryptococcus neoformans is a pathogenic basidiomycetous fungus that infects the central nervous system causing meningoencephalitis. This project's objective is to understand signaling mechanisms controlling sexual reproduction and virulence in this model pathogenic fungus. Tremendous advances have been achieved in studies on the role of G protein regulated signal transduction pathways that control cell type and virulence. Two well-conserved cascades involving cAMP and MAP kinase signaling have been previously characterized. But it still remains largely unknown how fungal pathogens sense environmental and host signals that trigger these G protein governed pathways. We have identified a family of G protein-coupled receptors (GPCRs) and discovered that one GPCR, Gpr4, senses amino acids and interacts with the Ga protein Gpa1 to activate cAMP signaling. Our studies further reveal Gpa1 is required to sense multiple signals, which may provide new paradigms to understand how G proteins are activated by both receptor-dependent and receptor-independent mechanisms. The studies proposed here will provide new approaches to understand how ligand-GPCR-G protein interactions control microbial pathogenesis. The split-ubiquitin system will be applied to study the interactions between the family of GPCRs and associated Ga proteins. A yeast heterologous expression system will be developed to screen for potential ligands of individual GPCRs. Gene deletion mutants for each GPCR have been generated and their roles in signaling and pathogenesis will be studied in vitro and in a murine infection model. The specific aims of this project are to: 1) Identify and characterize sensors involved in cAMP signaling, and to test the hypothesis that a multiple sensor system operates in C. neoformans to activate the Ga protein Gpa1; 2) Elucidate interactions between the GPCR family and the Ga proteins Gpa1, Gpa2, and Gpa3; 3) Identify potential GPCR ligands and their roles in development and virulence. Outcomes of this project should fill critical research gaps between extracellular signal sensing and signal transduction cascades controlling sexual reproduction and virulence factor production in C. neoformans. Understanding ligand- GPCR-G protein interactions and regulation of fungal development will provide insights to develop new drug targets, and may provide the means to control C. neoformans and other pathogenic fungi, which have medical significance of considerable importance. Cryptococcus neoformans is a human fungal pathogen that infects the central nervous system and often causes meningitis that is fatal if untreated. Understanding ligand- GPCR-G protein interactions and regulation of fungal development will provide insights to development new drug targets, and may provide the means to control C neoformans and other pathogenic fungi, which have medical significance of considerable importance. [unreadable] [unreadable] [unreadable]
Funding Period: 2007-08-01 - 2009-07-31
more information: NIH RePORT

Top Publications

  1. pmc G protein signaling governing cell fate decisions involves opposing Galpha subunits in Cryptococcus neoformans
    Yen Ping Hsueh
    Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC 27710, USA
    Mol Biol Cell 18:3237-49. 2007
  2. pmc Ssk2 mitogen-activated protein kinase kinase kinase governs divergent patterns of the stress-activated Hog1 signaling pathway in Cryptococcus neoformans
    Yong Sun Bahn
    Department of Bioinformatics and Life Science, Soongsil University, Seoul, Korea
    Eukaryot Cell 6:2278-89. 2007
  3. pmc The RGS protein Crg2 regulates both pheromone and cAMP signalling in Cryptococcus neoformans
    Chaoyang Xue
    Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC 27710, USA
    Mol Microbiol 70:379-95. 2008
  4. pmc Magnificent seven: roles of G protein-coupled receptors in extracellular sensing in fungi
    Chaoyang Xue
    Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC, USA
    FEMS Microbiol Rev 32:1010-32. 2008
  5. pmc A constitutively active GPCR governs morphogenic transitions in Cryptococcus neoformans
    Yen Ping Hsueh
    Department of Molecular Genetics and Microbiology, Duke University, Durham, NC 27710, USA
    EMBO J 28:1220-33. 2009
  6. pmc Comparative transcriptome analysis reveals novel roles of the Ras and cyclic AMP signaling pathways in environmental stress response and antifungal drug sensitivity in Cryptococcus neoformans
    Shinae Maeng
    Department of Biotechnology, Center for Fungal Pathogenesis, Yonsei University, 134 Shinchon dong, Seodaemun gu, 120 749 Seoul, Republic of Korea
    Eukaryot Cell 9:360-78. 2010
  7. pmc Comparative transcriptome analysis of the CO2 sensing pathway via differential expression of carbonic anhydrase in Cryptococcus neoformans
    Min Su Kim
    Department of Biotechnology, Center for Fungal Pathogenesis, Yonsei University, Seoul 120 749, Korea
    Genetics 185:1207-19. 2010
  8. pmc Assessment of constitutive activity of a G protein-coupled receptor, CPR2, in Cryptococcus neoformans by heterologous and homologous methods
    Chaoyang Xue
    Public Health Research Institute, University of Medicine and Dentistry of New Jersey, Newark, New Jersey, USA
    Methods Enzymol 484:397-412. 2010

Detail Information

Publications8

  1. pmc G protein signaling governing cell fate decisions involves opposing Galpha subunits in Cryptococcus neoformans
    Yen Ping Hsueh
    Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC 27710, USA
    Mol Biol Cell 18:3237-49. 2007
    ..The incorporation of an additional Galpha into the regulatory circuit enabled increased signaling complexity and facilitated cell fate decisions involving choice between yeast growth and filamentous asexual/sexual development...
  2. pmc Ssk2 mitogen-activated protein kinase kinase kinase governs divergent patterns of the stress-activated Hog1 signaling pathway in Cryptococcus neoformans
    Yong Sun Bahn
    Department of Bioinformatics and Life Science, Soongsil University, Seoul, Korea
    Eukaryot Cell 6:2278-89. 2007
    ..Taken together, these findings indicate that Ssk2 is a critical interface connecting the two-component system and the Pbs2-Hog1 MAPK pathway in C. neoformans...
  3. pmc The RGS protein Crg2 regulates both pheromone and cAMP signalling in Cryptococcus neoformans
    Chaoyang Xue
    Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC 27710, USA
    Mol Microbiol 70:379-95. 2008
    ..We conclude that Crg2 participates in controlling both Gpa1-cAMP-virulence and pheromone-mating signalling cascades and hypothesize it may serve as a molecular interface between these two central signalling conduits...
  4. pmc Magnificent seven: roles of G protein-coupled receptors in extracellular sensing in fungi
    Chaoyang Xue
    Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC, USA
    FEMS Microbiol Rev 32:1010-32. 2008
    ..We also emphasize the utility of yeast as a discovery tool for systemic studies of GPCRs from other organisms...
  5. pmc A constitutively active GPCR governs morphogenic transitions in Cryptococcus neoformans
    Yen Ping Hsueh
    Department of Molecular Genetics and Microbiology, Duke University, Durham, NC 27710, USA
    EMBO J 28:1220-33. 2009
    ..This study established a new paradigm in which a naturally occurring constitutively active G protein-coupled receptor governs morphogenesis in fungi...
  6. pmc Comparative transcriptome analysis reveals novel roles of the Ras and cyclic AMP signaling pathways in environmental stress response and antifungal drug sensitivity in Cryptococcus neoformans
    Shinae Maeng
    Department of Biotechnology, Center for Fungal Pathogenesis, Yonsei University, 134 Shinchon dong, Seodaemun gu, 120 749 Seoul, Republic of Korea
    Eukaryot Cell 9:360-78. 2010
    ..Among the cAMP-dependent gene products that we characterized, two small heat shock proteins, Hsp12 and Hsp122, were found to be involved in the polyene antifungal drug susceptibility of C. neoformans...
  7. pmc Comparative transcriptome analysis of the CO2 sensing pathway via differential expression of carbonic anhydrase in Cryptococcus neoformans
    Min Su Kim
    Department of Biotechnology, Center for Fungal Pathogenesis, Yonsei University, Seoul 120 749, Korea
    Genetics 185:1207-19. 2010
    ..neoformans. In conclusion, this study provides insights into the comprehensive signaling networks orchestrated by CA/CO(2)-sensing pathways in pathogenic fungi...
  8. pmc Assessment of constitutive activity of a G protein-coupled receptor, CPR2, in Cryptococcus neoformans by heterologous and homologous methods
    Chaoyang Xue
    Public Health Research Institute, University of Medicine and Dentistry of New Jersey, Newark, New Jersey, USA
    Methods Enzymol 484:397-412. 2010
    ..In this chapter, we summarize methods used for assessing the constitutive activity of Cpr2 and its mutants, which could be beneficial for other GPCR studies...