Accumulation of MFG-E8/lactadherin on exosomes from immature dendritic cells.
Exosomes are vesicles of endocytic origin secreted spontaneously by dendritic cells (DCs). We have shown previously that exosomes can transfer antigen or MHC-peptide complexes between DCs, thus potentially amplifying the immune response. We had also identified milk fat globule EGF/factor VIII (MFG-E8), also called lactadherin, as one of the major exosomal proteins. MFG-E8 has two domains: an Arg-Gly-Asp sequence that binds integrins alphavbeta3 and alphavbeta5 (expressed by human DCs and macrophages) and a phosphatidyl-serine (PS) binding sequence through which it associates to PS-containing membranes (among which exosomes). MFG-E8 is thus a good candidate molecule to address exosomes to DCs. Here, we show that MFG-E8 is expressed by immature bone-marrow-derived DCs (BMDCs) and secreted in association with exosomes in vitro. We have generated mice expressing an inactive form of MFG-E8, fused to beta-galactosidase. Analyzing these mice, we demonstrate that MFG-E8 is expressed in vivo in splenic DCs. In a mouse DC-dependent, antigen-specific, CD4 T cell-stimulation assay, exosomes produced by MFG-E8-deficient BMDCs were barely less efficient than exosomes bearing MFG-E8. We conclude that MFG-E8 is efficiently targeted to exosomes but is not essential to address exosomes to mouse BMDCs. Involvement of MFG-E8/lactadherin in exosome targeting to other DC subpopulations, or to human DCs, is still possible.
Véron
Philippe
P
INSERM U653, Institut Curie, 26 rue d'Ulm, 75245 Paris Cedex 05, France.
Segura
Elodie
E
Sugano
Gaël
G
Amigorena
Sebastian
S
Théry
Clotilde
C
D000818:Animals; D017951:Antigen Presentation; D000954:Antigens, Surface / Q000276:immunology / Q000378:metabolism*; D001854:Bone Marrow Cells; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology; D002450:Cell Communication / Q000276:immunology; D003713:Dendritic Cells / Q000737:chemistry* / Q000276:immunology* / Q000378:metabolism; D011992:Endosomes / Q000737:chemistry* / Q000378:metabolism; D008213:Lymphocyte Activation / Q000276:immunology; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D008894:Milk Proteins / Q000276:immunology / Q000378:metabolism*; D013154:Spleen / Q000166:cytology
D000954:Antigens, Surface; C490919:Mfge8 protein, mouse; D008894:Milk Proteins