Impaired recruitment of the small GTPase rab7 correlates with the inhibition of phagosome maturation by Leishmania donovani promastigotes.
We have shown recently that one of the survival strategies used by Leishmania donovani promastigotes during the establishment of infection in macrophages consists in inhibiting phagosome-endosome fusion. This inhibition requires the expression of lipophosphoglycan (LPG), the predominant surface glycoconjugate of promastigotes, as parasites expressing truncated forms of LPG reside in phagosomes that fuse extensively with endocytic organelles. In the present study, we developed a single-organelle fluorescence analysis approach to study and analyse the intracellular trafficking of 'fusogenic' and 'low-fusogenic' phagosomes induced by an LPG repeating unit-defective mutant (Ipg2 KO) or by wild-type L. donovani promastigotes respectively. The results obtained indicate that phagosomes containing mutant parasites fuse extensively with endocytic organelles and transform into phagolysosomes by losing the early endosome markers EEA1 and transferrin receptor, and acquiring the late endocytic and lysosomal markers rab7 and LAMP1. In contrast, a majority of 'low-fusogenic' phagosomes containing wild-type L. donovani promastigotes do not acquire rab7, wheres they acquire LAMP1 with slower kinetics. These results suggest that L. donovani parasites use LPG to restrict phagosome-endosome fusion at the onset of infection in order to prevent phagosome maturation. This is likely to permit the transformation of hydrolase-sensitive promastigotes into hydrolase-resistant amastigotes within a hospitable vacuole not displaying the harsh environment of phagolysosomes.
Scianimanico
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Département de pathologie et biologie cellulaire, Université de Montréal, Québec, Canada.
Desrosiers
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Dermine
J F
JF
Méresse
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Descoteaux
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Desjardins
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D000818:Animals; D015703:Antigens, CD / Q000032:analysis / Q000378:metabolism; D002460:Cell Line; D011992:Endosomes / Q000502:physiology; D005434:Flow Cytometry; D019084:Fluorescent Antibody Technique, Indirect; D006028:Glycosphingolipids / Q000235:genetics; D007893:Leishmania donovani / Q000235:genetics / Q000254:growth & development*; D052118:Lysosomal-Associated Membrane Protein 1; D051907:Lysosomal Membrane Proteins; D008247:Lysosomes / Q000378:metabolism; D008264:Macrophages / Q000166:cytology / Q000469:parasitology*; D008561:Membrane Fusion; D008562:Membrane Glycoproteins / Q000032:analysis / Q000378:metabolism; D008565:Membrane Proteins / Q000032:analysis / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D010588:Phagosomes / Q000469:parasitology / Q000502:physiology*; D015800:Protozoan Proteins; D011990:Receptors, Transferrin / Q000378:metabolism; D033921:Vesicular Transport Proteins; D020691:rab GTP-Binding Proteins / Q000032:analysis / Q000378:metabolism*; D000090802:rab7 GTP-Binding Proteins
D015703:Antigens, CD; D006028:Glycosphingolipids; C095909:LPG2 protein, Leishmania; D052118:Lysosomal-Associated Membrane Protein 1; D051907:Lysosomal Membrane Proteins; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D015800:Protozoan Proteins; D011990:Receptors, Transferrin; D033921:Vesicular Transport Proteins; C093846:early endosome antigen 1; D000090802:rab7 GTP-Binding Proteins; D020691:rab GTP-Binding Proteins