title: Characterization of C-type lectins reveals an unexpectedly limited interaction between Cryptococcus neoformans spores and Dectin-1.
abstract: Phagocytosis by innate immune cells is an important process for protection against multiple pathologies and is particularly important for resistance to infection. However, phagocytosis has also been implicated in the progression of some diseases, including the dissemination of the human fungal pathogen, Cryptococcus neoformans. Previously, we identified Dectin-1 as a likely phagocytic receptor for C. neoformans spores through the use of soluble components in receptor-ligand blocking experiments. In this study, we used gain-of-function and loss-of-function assays with intact cells to evaluate the in vivo role of Dectin-1 and other C-type lectins in interactions with C. neoformans spores and discovered stark differences in outcome when compared with previous assays. First, we found that non-phagocytic cells expressing Dectin-1 were unable to bind spores and that highly sensitive reporter cells expressing Dectin-1 were not stimulated by spores. Second, we determined that some phagocytes from Dectin-1-/- mice interacted with spores differently than wild type (WT) cells, but the effects varied among assays and were modest overall. Third, while we detected small but statistically significant reductions in phagocytosis by primary alveolar macrophages from Dectin-1-/- mice compared to WT, we found no differences in survival between WT and Dectin-1-/- mice challenged with spores. Further analyses to assess the roles of other C-type lectins and their adapters revealed very weak stimulation of Dectin-2 reporter cells by spores and modest differences in binding and phagocytosis by Dectin-2-/- bone marrow-derived phagocytes. There were no discernable defects in binding or phagocytosis by phagocytes lacking Mannose Receptor, Mincle, Card-9, or FcRγ. Taken together, these results lead to the conclusion that Dectin-1 and other C-type lectins do not individually play a major roles in phagocytosis and innate defense by phagocytes against C. neoformans spores and highlight challenges in using soluble receptor/ligand blocking experiments to recapitulate biologically relevant interactions.
authors.affiliation: Department of Biomolecular Chemistry, University of Wisconsin-Madison, School of Medicine and Public Health, Madison, Wisconsin, United States of America.
authors.forename: Naomi M
authors.initials: NM
authors.lastname: Walsh
authors.affiliation: Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, School of Medicine and Public Health, Madison, Wisconsin, United States of America.
authors.forename: Marcel
authors.initials: M
authors.lastname: Wuthrich
authors.affiliation: Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, School of Medicine and Public Health, Madison, Wisconsin, United States of America.
authors.forename: Huafeng
authors.initials: H
authors.lastname: Wang
authors.affiliation: Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, School of Medicine and Public Health, Madison, Wisconsin, United States of America.|Department of Pediatrics, University of Wisconsin-Madison, School of Medicine and Public Health, Madison, Wisconsin, United States of America.
authors.forename: Bruce
authors.initials: B
authors.lastname: Klein
authors.affiliation: Department of Biomolecular Chemistry, University of Wisconsin-Madison, School of Medicine and Public Health, Madison, Wisconsin, United States of America.|Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, School of Medicine and Public Health, Madison, Wisconsin, United States of America.
authors.forename: Christina M
authors.initials: CM
authors.lastname: Hull
mesh_terms: D000818:Animals; D016466:CHO Cells; D003412:Cricetulus; D003453:Cryptococcosis / Q000378:metabolism; D003455:Cryptococcus neoformans / Q000472:pathogenicity / Q000502:physiology*; D054884:Host-Pathogen Interactions; D037181:Lectins, C-Type / Q000235:genetics / Q000378:metabolism*; D016676:Macrophages, Alveolar / Q000382:microbiology; D000090323:Mannose Receptor; D037241:Mannose-Binding Lectins / Q000235:genetics / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D010586:Phagocytes / Q000382:microbiology; D010587:Phagocytosis / Q000502:physiology*; D011956:Receptors, Cell Surface / Q000235:genetics / Q000378:metabolism; D013172:Spores, Fungal / Q000472:pathogenicity; D000099181:Dectin-1
chemical_list: D037181:Lectins, C-Type; D000090323:Mannose Receptor; D037241:Mannose-Binding Lectins; D008565:Membrane Proteins; D011956:Receptors, Cell Surface; D000099181:Dectin-1; C113583:Clecsf8 protein, mouse; C445340:dectin-2, mouse