title: Cryptococcus neoformans is internalized by receptor-mediated or 'triggered' phagocytosis, dependent on actin recruitment.
abstract: Cryptococcosis by the encapsulated yeast Cryptococcus neoformans affects mostly immunocompromised individuals and is a frequent neurological complication in AIDS patients. Recent studies support the idea that intracellular survival of Cryptococcus yeast cells is important for the pathogenesis of cryptococcosis. However, the initial steps of Cryptococcus internalization by host cells remain poorly understood. Here, we investigate the mechanism of Cryptococcus neoformans phagocytosis by peritoneal macrophages using confocal and electron microscopy techniques, as well as flow cytometry quantification, evaluating the importance of fungal capsule production and of host cell cytoskeletal elements for fungal phagocytosis. Electron microscopy analyses revealed that capsular and acapsular strains of C. neoformans are internalized by macrophages via both 'zipper' (receptor-mediated) and 'trigger' (membrane ruffle-dependent) phagocytosis mechanisms. Actin filaments surrounded phagosomes of capsular and acapsular yeasts, and the actin depolymerizing drugs cytochalasin D and latrunculin B inhibited yeast internalization and actin recruitment to the phagosome area. In contrast, nocodazole and paclitaxel, inhibitors of microtubule dynamics decreased internalization but did not prevent actin recruitment to the site of phagocytosis. Our results show that different uptake mechanisms, dependent on both actin and tubulin dynamics occur during yeast internalization by macrophages, and that capsule production does not affect the mode of Cryptococcus uptake by host cells.
authors.affiliation: Laboratório de Biologia Celular de Fungos, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro/RJ, Brazil.
authors.forename: Caroline Rezende
authors.initials: CR
authors.lastname: Guerra
authors.affiliation: Laboratório de Tecnologia em Bioquímica e Microscopia, Colegiado de Ciências Biológicas e da Saúde, Centro Universitário Estadual da Zona Oeste, Campo Grande/RJ, Brazil.
authors.forename: Sergio Henrique
authors.initials: SH
authors.lastname: Seabra
authors.affiliation: Instituto Nacional de Metrologia Qualidade e Tecnologia, Duque de Caxias/RJ, Brazil ; Instituto Nacional de Biologia Estrutural e Bioimagens, Universidade Federal do Rio de Janeiro, Rio de Janeiro/RJ, Brazil.
authors.forename: Wanderley
authors.initials: W
authors.lastname: de Souza
authors.affiliation: Laboratório de Biologia Celular de Fungos, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro/RJ, Brazil.
authors.forename: Sonia
authors.initials: S
authors.lastname: Rozental
mesh_terms: D000199:Actins / Q000378:metabolism*; D000818:Animals; D003453:Cryptococcosis / Q000378:metabolism / Q000382:microbiology*; D003455:Cryptococcus neoformans / Q000378:metabolism*; D003599:Cytoskeleton / Q000378:metabolism; D017737:Macrophages, Peritoneal / Q000378:metabolism / Q000382:microbiology*; D051379:Mice; D010587:Phagocytosis / Q000502:physiology*; D010588:Phagosomes / Q000378:metabolism
chemical_list: D000199:Actins