title: Candida albicans Hgt1p, a multifunctional evasion molecule: complement inhibitor, CR3 analogue, and human immunodeficiency virus-binding molecule.
abstract: BACKGROUND
  The complement system is tightly controlled by several regulators. Two of these, factor H (FH) and C4b-binding protein (C4BP), can be acquired by pathogens conveying resistance to complement attack. The aim of the study was to characterize the FH binding molecule of Candida albicans, a potentially life-threatening yeast.
  
  
  METHODS
  The gene coding for this molecule was identified by probing an expression library and homozygous deletion mutants of the respective gene were constructed. Binding and functional assays were undertaken to compare wild-type and knockout strains.
  
  
  RESULTS
  The high-affinity glucose transporter 1 (CaHgt1p) was identified as an FH-binding molecule. Homozygous hgt1Δ/Δ deletion mutants, but not the restored strain in which HGT1 was reintegrated, showed a decreased binding of FH and even of C4BP, demonstrating its function as an FH- and C4BP-binding protein. This led to an enhanced terminal complement complex deposition after incubation with human serum; CaHgt1p thus functions as complement inhibitor. hgt1Δ/Δ mutants failed to form rosettes with complement-coated sheep erythrocytes, and show reduced binding to HIV-gp160, implying that a complement receptor 3 (CR3) moiety, known as fungal HIV binding molecule is lacking.
  
  
  CONCLUSIONS
  CaHgt1p is a multifunctional evasion molecule, as complement inhibitor, CR3 analogue and HIV receptor.
authors.affiliation: Division of Hygiene and Medical Microbiology, Innsbruck Medical University, Austria.
authors.forename: Iwona
authors.initials: I
authors.lastname: Lesiak-Markowicz
authors.forename: Georgia
authors.initials: G
authors.lastname: Vogl
authors.forename: Tobias
authors.initials: T
authors.lastname: Schwarzmüller
authors.forename: Cornelia
authors.initials: C
authors.lastname: Speth
authors.forename: Cornelia
authors.initials: C
authors.lastname: Lass-Flörl
authors.forename: Manfred P
authors.initials: MP
authors.lastname: Dierich
authors.forename: Karl
authors.initials: K
authors.lastname: Kuchler
authors.forename: Reinhard
authors.initials: R
authors.lastname: Würzner
mesh_terms: D002176:Candida albicans / Q000166:cytology / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D002177:Candidiasis / Q000276:immunology / Q000378:metabolism*; D015935:Complement C4b / Q000378:metabolism*; D017242:Complement Factor H / Q000276:immunology / Q000378:metabolism*; D015938:Complement Membrane Attack Complex / Q000378:metabolism*; D005656:Fungal Proteins / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D051246:Glucose Transport Proteins, Facilitative / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D019302:HIV Envelope Protein gp160 / Q000378:metabolism*; D006801:Humans; D007113:Immunity, Innate; D016177:Macrophage-1 Antigen / Q000378:metabolism; D011485:Protein Binding
chemical_list: D015938:Complement Membrane Attack Complex; D005656:Fungal Proteins; D051246:Glucose Transport Proteins, Facilitative; C405029:HGT1 protein, Candida albicans; D019302:HIV Envelope Protein gp160; D016177:Macrophage-1 Antigen; D015935:Complement C4b; D017242:Complement Factor H