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Phagocytosis of Leishmania donovani amastigotes is Rac1 dependent and occurs in the absence of NADPH oxidase activation
Author(s) -
Lodge Robert,
Descoteaux Albert
Publication year - 2006
Publication title -
european journal of immunology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.272
H-Index - 201
eISSN - 1521-4141
pISSN - 0014-2980
DOI - 10.1002/eji.200636089
Subject(s) - internalization , phagosome , superoxide , nadph oxidase , amastigote , phagocytosis , leishmania donovani , biology , leishmania , microbiology and biotechnology , biochemistry , reactive oxygen species , immunology , leishmaniasis , visceral leishmaniasis , parasite hosting , world wide web , computer science , enzyme , cell
Abstract Macrophages produce little superoxide during phagocytosis of Leishmania donovani amastigotes. In this study, we characterized molecular events associated with L. donovani amastigotes uptake by mouse macrophages, to further define the mechanisms by which they are internalized without triggering superoxide production. Using transient transfections, we first showed that internalization of L. donovani amastigotes is mediated by the GTPases Rac1 and Arf6, of which Rac1 is recruited and retained on parasite‐containing phagosomes. Next, we showed that, whereas internalization of amastigotes induced no superoxide release, co‐internalization of serum‐opsonized zymozan and amastigotes resulted in superoxide production. Furthermore, in co‐internalization experiments, we detected superoxide production in over 95% of phagosomes containing IgG‐opsonized SRBC compared to 5% of amastigote‐harboring phagosomes. These results suggest that amastigotes evade the ability of macrophages to produce superoxide during phagocytosis. Consistently, we observed that amastigotes induced barely detectable phosphorylation of the NADPH oxidase component p47 phox , leading to a defective phagosomal recruitment of p67 phox and p47 phox . Finally, we showed that amastigotes disrupt phagosomal lipid raft integrity, potentially interfering with NADPH oxidase assembly. Collectively, our results indicate that internalization of L. donovani amastigotes is a Rac1‐ and Arf6‐dependent process that occurs in the absence of significant NADPH oxidase activation.