title: Essential role for vacuolar acidification in Candida albicans virulence.
abstract: Fungal infections are on the rise, with mortality above 30% in patients with septic Candida infections. Mutants lacking V-ATPase activity are avirulent and fail to acidify endomembrane compartments, exhibiting pleiotropic defects in secretory, endosomal, and vacuolar pathways. However, the individual contribution of organellar acidification to virulence and its associated traits is not known. To dissect their separate roles in Candida albicans pathogenicity we generated knock-out strains for the V0 subunit a genes VPH1 and STV1, which target the vacuole and secretory pathway, respectively. While the two subunits were redundant in many vma phenotypes, such as alkaline pH sensitivity, calcium homeostasis, respiratory defects, and cell wall integrity, we observed a unique contribution of VPH1. Specifically, vph1Δ was defective in acidification of the vacuole and its dependent functions, such as metal ion sequestration as evidenced by hypersensitivity to Zn(2+) toxicity, whereas stv1Δ resembled wild type. In growth conditions that elicit morphogenic switching, vph1Δ was defective in forming hyphae whereas stv1Δ was normal or only modestly impaired. Host cell interactions were evaluated in vitro using the Caco-2 model of intestinal epithelial cells, and murine macrophages. Like wild type, stv1Δ was able to inflict cellular damage in Caco-2 and macrophage cells, as assayed by LDH release, and escape by filamentation. In contrast, vph1Δ resembled a vma7Δ mutant, with significant attenuation in host cell damage. Finally, we show that VPH1 is required for fungal virulence in a murine model of systemic infection. Our results suggest that vacuolar acidification has an essential function in the ability of C. albicans to form hyphae and establish infection.
authors.affiliation: From the Departments of Physiology and.
authors.forename: Cassandra
authors.initials: C
authors.lastname: Patenaude
authors.affiliation: From the Departments of Physiology and.
authors.forename: Yongqiang
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Molecular Biology and Genetics, The Johns Hopkins School of Medicine, Baltimore, Maryland 21205 and.
authors.forename: Brendan
authors.initials: B
authors.lastname: Cormack
authors.affiliation: the Division of Infectious Diseases, Children's Hospital, Harvard Medical School, Boston, Massachusetts 02115.
authors.forename: Julia
authors.initials: J
authors.lastname: Köhler
authors.affiliation: From the Departments of Physiology and. Electronic address: rrao@jhmi.edu.
authors.forename: Rajini
authors.initials: R
authors.lastname: Rao
mesh_terms: D000818:Animals; D018938:Caco-2 Cells; D002176:Candida albicans / Q000201:enzymology / Q000235:genetics / Q000472:pathogenicity*; D002177:Candidiasis / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D004195:Disease Models, Animal; D005260:Female; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D055785:Gene Knockdown Techniques; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008264:Macrophages / Q000378:metabolism / Q000382:microbiology / Q000473:pathology; D051379:Mice; D008807:Mice, Inbred BALB C; D025262:Vacuolar Proton-Translocating ATPases / Q000235:genetics / Q000378:metabolism*; D014617:Vacuoles / Q000201:enzymology* / Q000235:genetics; D037521:Virulence Factors / Q000235:genetics / Q000378:metabolism*
chemical_list: D005656:Fungal Proteins; D037521:Virulence Factors; D025262:Vacuolar Proton-Translocating ATPases
keywords: Candida albicans; Hyphae; Morphogenesis; Proton Pumps; V-ATPase; Vacuolar Acidification; Vacuole; Virulence Factors