title: The contribution of Candida albicans vacuolar ATPase subunit V₁B, encoded by VMA2, to stress response, autophagy, and virulence is independent of environmental pH.
abstract: Candida albicans vacuoles are central to many critical biological processes, including filamentation and in vivo virulence. The V-ATPase proton pump is a multisubunit complex responsible for organellar acidification and is essential for vacuolar biogenesis and function. To study the function of the V₁B subunit of C. albicans V-ATPase, we constructed a tetracycline-regulatable VMA2 mutant, tetR-VMA2. Inhibition of VMA2 expression resulted in the inability to grow at alkaline pH and altered resistance to calcium, cold temperature, antifungal drugs, and growth on nonfermentable carbon sources. Furthermore, V-ATPase was unable to fully assemble at the vacuolar membrane and was impaired in proton transport and ATPase-specific activity. VMA2 repression led to vacuolar alkalinization in addition to abnormal vacuolar morphology and biogenesis. Key virulence-related traits, including filamentation and secretion of degradative enzymes, were markedly inhibited. These results are consistent with previous studies of C. albicans V-ATPase; however, differential contributions of the V-ATPase Vo and V₁ subunits to filamentation and secretion are observed. We also make the novel observation that inhibition of C. albicans V-ATPase results in increased susceptibility to osmotic stress. Notably, V-ATPase inhibition under conditions of nitrogen starvation results in defects in autophagy. Lastly, we show the first evidence that V-ATPase contributes to virulence in an acidic in vivo system by demonstrating that the tetR-VMA2 mutant is avirulent in a Caenorhabditis elegans infection model. This study illustrates the fundamental requirement of V-ATPase for numerous key virulence-related traits in C. albicans and demonstrates that the contribution of V-ATPase to virulence is independent of host pH.
authors.affiliation: Section of Infectious Diseases, New Mexico Veterans Healthcare System, Albuquerque, New Mexico, USA.
authors.forename: Hallie S
authors.initials: HS
authors.lastname: Rane
authors.affiliation: Section of Infectious Diseases, New Mexico Veterans Healthcare System, Albuquerque, New Mexico, USA Division of Infectious Diseases, University of New Mexico Health Science Center, Albuquerque, New Mexico, USA.
authors.forename: Stella M
authors.initials: SM
authors.lastname: Bernardo
authors.affiliation: Department of Biochemistry and Molecular Biology, University of New Mexico Health Science Center, Albuquerque, New Mexico, USA.
authors.forename: Summer R
authors.initials: SR
authors.lastname: Hayek
authors.affiliation: Department of Biochemistry and Molecular Biology, University of New Mexico Health Science Center, Albuquerque, New Mexico, USA.
authors.forename: Jessica L
authors.initials: JL
authors.lastname: Binder
authors.affiliation: Department of Biochemistry and Molecular Biology, University of New Mexico Health Science Center, Albuquerque, New Mexico, USA.
authors.forename: Karlett J
authors.initials: KJ
authors.lastname: Parra
authors.affiliation: Section of Infectious Diseases, New Mexico Veterans Healthcare System, Albuquerque, New Mexico, USA Division of Infectious Diseases, University of New Mexico Health Science Center, Albuquerque, New Mexico, USA SamALee@salud.unm.edu.
authors.forename: Samuel A
authors.initials: SA
authors.lastname: Lee
mesh_terms: D000818:Animals; D001343:Autophagy / Q000235:genetics*; D017173:Caenorhabditis elegans / Q000235:genetics / Q000382:microbiology; D002176:Candida albicans / Q000201:enzymology* / Q000235:genetics / Q000472:pathogenicity; D006863:Hydrogen-Ion Concentration; D021122:Protein Subunits / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D013312:Stress, Physiological / Q000235:genetics; D025262:Vacuolar Proton-Translocating ATPases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D014617:Vacuoles / Q000201:enzymology / Q000235:genetics; D014774:Virulence / Q000235:genetics
chemical_list: D021122:Protein Subunits; D025262:Vacuolar Proton-Translocating ATPases