title: Membrane microdomain components of Histoplasma capsulatum yeast forms, and their role in alveolar macrophage infectivity.
abstract: Analysis of membrane lipids of Histoplasma capsulatum showed that ~40% of fungal ergosterol is present in membrane microdomain fractions resistant to treatment with non-ionic detergent at 4°C. Specific proteins were also enriched in these fractions, particularly Pma1p a yeast microdomain protein marker (a plasma membrane proton ATPase), a 30kDa laminin-binding protein, and a 50kDa protein recognized by anti-α5-integrin antibody. To better understand the role of ergosterol-dependent microdomains in fungal biology and pathogenicity, H. capsulatum yeast forms were treated with a sterol chelator, methyl-beta-cyclodextrin (mβCD). Removal of ergosterol by mβCD incubation led to disorganization of ergosterol-enriched microdomains containing Pma1p and the 30kDa protein, resulting in displacement of these proteins from detergent-insoluble to -soluble fractions in sucrose density gradient ultracentrifugation. mβCD treatment did not displace/remove the 50kDa α5-integrin-like protein nor had effect on the organization of glycosphingolipids present in the detergent-resistant fractions. Ergosterol-enriched membrane microdomains were also shown to be important for infectivity of alveolar macrophages; after treatment of yeasts with mβCD, macrophage infectivity was reduced by 45%. These findings suggest the existence of two populations of detergent-resistant membrane microdomains in H. capsulatum yeast forms: (i) ergosterol-independent microdomains rich in integrin-like proteins and glycosphingolipids, possibly involved in signal transduction; (ii) ergosterol-enriched microdomains containing Pma1p and the 30kDa laminin-binding protein; ergosterol and/or the 30kDa protein may be involved in macrophage infectivity.
authors.affiliation: Department of Biochemistry, Universidade Federal de São Paulo, São Paulo, SP, Brazil.
authors.forename: Loriane
authors.initials: L
authors.lastname: Tagliari
authors.forename: Marcos S
authors.initials: MS
authors.lastname: Toledo
authors.forename: Tanil G
authors.initials: TG
authors.lastname: Lacerda
authors.forename: Erika
authors.initials: E
authors.lastname: Suzuki
authors.forename: Anita H
authors.initials: AH
authors.lastname: Straus
authors.forename: Helio K
authors.initials: HK
authors.lastname: Takahashi
mesh_terms: D000818:Animals; D004875:Ergosterol / Q000378:metabolism; D005656:Fungal Proteins / Q000378:metabolism*; D006658:Histoplasma / Q000378:metabolism* / Q000472:pathogenicity*; D006660:Histoplasmosis / Q000378:metabolism* / Q000382:microbiology / Q000473:pathology; D016676:Macrophages, Alveolar / Q000378:metabolism* / Q000382:microbiology / Q000473:pathology; D021962:Membrane Microdomains / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism*; D051379:Mice; D008807:Mice, Inbred BALB C; D047392:beta-Cyclodextrins / Q000494:pharmacology
chemical_list: D005656:Fungal Proteins; D008565:Membrane Proteins; D047392:beta-Cyclodextrins; C108732:methyl-beta-cyclodextrin; D004875:Ergosterol