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Imaging G-protein Coupled Receptor (GPCR)-mediated Signaling Events that Control Chemotaxis of Dictyostelium Discoideum
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G protein-coupled receptor Gpr4 senses amino acids and activates the cAMP-PKA pathway in Cryptococcus neoformans

Chaoyang Xue1, Yong-Sun Bahn, Gary M Cox

  • 1Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC 27710, USA.

Molecular Biology of the Cell
|November 18, 2005
PubMed

Insights

Researchers identified Gpr4 as a novel receptor in Cryptococcus neoformans that activates the cAMP-PKA pathway. This discovery reveals how nutrients like amino acids regulate fungal virulence and differentiation.

Area of Science:

  • Mycology
  • Molecular Biology
  • Cellular Signaling

Background:

  • The Galpha protein Gpa1 regulates the cAMP-PKA pathway, crucial for virulence and differentiation in Cryptococcus neoformans.
  • The specific signals and receptors initiating this pathway in C. neoformans remained unidentified.

Purpose of the Study:

  • To identify the upstream signals and receptors that activate the Gpa1-governed cAMP-PKA pathway in C. neoformans.
  • To elucidate the role of identified receptors in fungal physiology and nutrient sensing.

Main Methods:

  • Bioinformatic analysis to identify putative G protein-coupled receptors (GPCRs).
  • Genetic analysis of gpr4 mutants, including phenotypic characterization and epistasis studies.
  • Yeast two-hybrid and split-ubiquitin assays to investigate protein interactions.
  • Fluorescence microscopy to determine protein localization and receptor internalization.

Main Results:

  • Seven putative GPCRs were identified; Gpr4 showed functional and structural similarities to known receptors.
  • gpr4 mutants displayed defects in capsule production and mating, mirroring gpa1 mutants.
  • Gpr4 functions upstream of Gpa1, interacting with it and localizing to the plasma membrane.
  • Methionine triggered Gpr4 internalization, and gpr4 mutants showed altered responses to amino acids, suggesting Gpr4 acts as an amino acid sensor.

Conclusions:

  • Gpr4 is a novel GPCR that functions upstream of Gpa1 to regulate the cAMP-PKA pathway in C. neoformans.
  • Amino acids, such as methionine, likely act as ligands for Gpr4, linking nutrient availability to fungal signaling.
  • This nutrient sensing mechanism involving glucose and amino acids represents a conserved system in pathogenic fungi.

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