An exosome-based secretion pathway is responsible for protein export from Leishmania and communication with macrophages.
Specialized secretion systems are used by numerous bacterial pathogens to export virulence factors into host target cells. Leishmania and other eukaryotic intracellular pathogens also deliver effector proteins into host cells; however, the mechanisms involved have remained elusive. In this report, we identify exosome-based secretion as a general mechanism for protein secretion by Leishmania, and show that exosomes are involved in the delivery of proteins into host target cells. Comparative quantitative proteomics unambiguously identified 329 proteins in Leishmania exosomes, accounting for >52% of global protein secretion from these organisms. Our findings demonstrate that infection-like stressors (37 degrees C +/- pH 5.5) upregulated exosome release more than twofold and also modified exosome protein composition. Leishmania exosomes and exosomal proteins were detected in the cytosolic compartment of infected macrophages and incubation of macrophages with exosomes selectively induced secretion of IL-8, but not TNF-alpha. We thus provide evidence for an apparently broad-based mechanism of protein export by Leishmania. Moreover, we describe a mechanism for the direct delivery of Leishmania molecules into macrophages. These findings suggest that, like mammalian exosomes, Leishmania exosomes function in long-range communication and immune modulation.
Department of Medicine, Division of Infectious Diseases, University of British Columbia, Faculties of Medicine and Science, 2733 Heather St, Vancouver, BC V5Z 3J5, Canada.
Judith Maxwell
JM
Silverman
Joachim
J
Clos
Carolina Camargo
CC
de'Oliveira
Omid
O
Shirvani
Yuan
Y
Fang
Christine
C
Wang
Leonard J
LJ
Foster
Neil E
NE
Reiner
D000818:Animals; D015415:Biomarkers / Q000378:metabolism; D002450:Cell Communication; D017077:Culture Media, Conditioned / Q000378:metabolism; D055354:Exosomes / Q000378:metabolism* / Q000648:ultrastructure; D005110:Extracellular Space / Q000378:metabolism; D018869:Heat-Shock Response; D006863:Hydrogen-Ion Concentration; D016209:Interleukin-8 / Q000378:metabolism; D007893:Leishmania donovani / Q000166:cytology* / Q000378:metabolism* / Q000472:pathogenicity / Q000648:ultrastructure; D008264:Macrophages / Q000166:cytology / Q000378:metabolism / Q000469:parasitology* / Q000648:ultrastructure; D008954:Models, Biological; D021381:Protein Transport; D040901:Proteomics; D015800:Protozoan Proteins / Q000378:metabolism*; D055571:Secretory Pathway; D013696:Temperature; D037521:Virulence Factors / Q000378:metabolism
D015415:Biomarkers; D017077:Culture Media, Conditioned; D016209:Interleukin-8; D015800:Protozoan Proteins; D037521:Virulence Factors