title: Antifungal Mechanism of Action of Lactoferrin: Identification of H+-ATPase (P3A-Type) as a New Apoptotic-Cell Membrane Receptor.
abstract: Human lactoferrin (hLf) is a protein of the innate immune system which induces an apoptotic-like process in yeast. Determination of the susceptibility to lactoferrin of several yeast species under different metabolic conditions, respiratory activity, cytoplasmic ATP levels, and external medium acidification mediated by glucose assays suggested plasma membrane Pma1p (P3A-type ATPase) as the hLf molecular target. The inhibition of plasma membrane ATPase activity by hLf and the identification of Pma1p as the hLf-binding membrane protein confirmed the previous physiological evidence. Consistent with this, cytoplasmic ATP levels progressively increased in hLf-treated Candida albicans cells. However, oligomycin, a specific inhibitor of the mitochondrial F-type ATPase proton pump (mtATPase), abrogated the antifungal activity of hLf, indicating a crucial role for mtATPase in the apoptotic process. We suggest that lactoferrin targeted plasma membrane Pma1p H(+)-ATPase, perturbing the cytoplasmic ion homeostasis (i.e., cytoplasmic H(+) accumulation and subsequent K(+) efflux) and inducing a lethal mitochondrial dysfunction. This initial event involved a normal mitochondrial ATP synthase activity responsible for both the ATP increment and subsequent hypothetical mitochondrial proton flooding process. We conclude that human lactoferrin inhibited Pma1p H(+)-ATPase, inducing an apoptotic-like process in metabolically active yeast. Involvement of mitochondrial H(+)-ATPase (nonreverted) was essential for the progress of this programmed cell death in which the ionic homeostasis perturbation seems to precede classical nonionic apoptotic events.
authors.affiliation: Laboratory of Oral Microbiology, School of Stomatology, Faculty of Medicine, University of Oviedo, Oviedo, Spain.
authors.forename: María T
authors.identifier: 0000-0002-7827-981X
authors.initials: MT
authors.lastname: Andrés
authors.affiliation: Laboratory of Oral Microbiology, School of Stomatology, Faculty of Medicine, University of Oviedo, Oviedo, Spain Department of Functional Biology (Microbiology), Faculty of Medicine, University of Oviedo, Oviedo, Spain.
authors.forename: Maikel
authors.identifier: 0000-0002-9562-6887
authors.initials: M
authors.lastname: Acosta-Zaldívar
authors.affiliation: Laboratory of Oral Microbiology, School of Stomatology, Faculty of Medicine, University of Oviedo, Oviedo, Spain Department of Functional Biology (Microbiology), Faculty of Medicine, University of Oviedo, Oviedo, Spain jffierro@uniovi.es.
authors.forename: José F
authors.identifier: 0000-0003-2752-0690
authors.initials: JF
authors.lastname: Fierro
mesh_terms: D000935:Antifungal Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D002176:Candida albicans / Q000187:drug effects* / Q000201:enzymology*; D002462:Cell Membrane / Q000201:enzymology*; D007781:Lactoferrin / Q000494:pharmacology*; D006180:Proton-Translocating ATPases / Q000378:metabolism*
chemical_list: D000935:Antifungal Agents; D007781:Lactoferrin; D006180:Proton-Translocating ATPases