title: Interaction of the heterotrimeric G protein alpha subunit SSG-1 of Sporothrix schenckii with proteins related to stress response and fungal pathogenicity using a yeast two-hybrid assay.
abstract: BACKGROUND
  Important biological processes require selective and orderly protein-protein interactions at every level of the signalling cascades. G proteins are a family of heterotrimeric GTPases that effect eukaryotic signal transduction through the coupling of cell surface receptors to cytoplasmic effector proteins. They have been associated with growth and pathogenicity in many fungi through gene knock-out studies. In Sporothrix schenckii, a pathogenic, dimorphic fungus, we previously identified a pertussis sensitive G alpha subunit, SSG-1. In this work we inquire into its interactions with other proteins.
  
  
  RESULTS
  Using the yeast two-hybrid technique, we identified protein-protein interactions between SSG-1 and other important cellular proteins. The interactions were corroborated using co-immuneprecipitation. Using these techniques we identified a Fe/Mn superoxide dismutase (SOD), a glyceraldehyde-3-P dehydrogenase (GAPDH) and two ion transport proteins, a siderophore-iron transporter belonging to the Major Facilitator Superfamily (MFS) and a divalent-cation transporter of the Nramp (natural resistance-associated macrophage protein) family as interacting with SSG-1. The cDNA's encoding these proteins were sequenced and bioinformatic macromolecular sequence analyses were used for the correct classification and functional assignment.
  
  
  CONCLUSIONS
  This study constitutes the first report of the interaction of a fungal G alpha inhibitory subunit with SOD, GAPDH, and two metal ion transporters. The identification of such important proteins as partners of a G alpha subunit in this fungus suggests possible mechanisms through which this G protein can affect pathogenicity and survival under conditions of environmental stress or inside the human host. The two ion transporters identified in this work are the first to be reported in S. schenckii and the first time they are identified as interacting with fungal G protein alpha subunits. The association of G protein alpha subunits to transport molecules reinforces the role of G proteins in the response to environmental signals and also highlights the involvement of fungal G protein alpha subunits in nutrient sensing in S. schenckii. These interactions suggest that these permeases could function as transceptors for G proteins in fungi.
authors.affiliation: Department of Microbiology and Medical Zoology, Medical Sciences Campus, University of Puerto Rico, PO Box 365067, San Juan, PR 00936-5067, USA.
authors.forename: Lizaida
authors.initials: L
authors.lastname: Pérez-Sánchez
authors.forename: Elizabeth
authors.initials: E
authors.lastname: González
authors.forename: Emilee E
authors.initials: EE
authors.lastname: Colón-Lorenzo
authors.forename: Waleska
authors.initials: W
authors.lastname: González-Velázquez
authors.forename: Ricardo
authors.initials: R
authors.lastname: González-Méndez
authors.forename: Nuri
authors.initials: N
authors.lastname: Rodríguez-del Valle
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D005656:Fungal Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D044385:GTP-Binding Protein alpha Subunits / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases / Q000235:genetics / Q000378:metabolism; D006801:Humans; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding; D055503:Protein Multimerization; D013175:Sporothrix / Q000737:chemistry / Q000235:genetics / Q000472:pathogenicity / Q000502:physiology*; D013174:Sporotrichosis / Q000382:microbiology; D013312:Stress, Physiological; D013482:Superoxide Dismutase / Q000235:genetics / Q000378:metabolism; D020798:Two-Hybrid System Techniques
chemical_list: D005656:Fungal Proteins; D044385:GTP-Binding Protein alpha Subunits; D010446:Peptide Fragments; C068142:glyceraldehyde 3-phosphate dehydrogenase (304-313); D013482:Superoxide Dismutase; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases