Molecular characterization of dendritic cell-derived exosomes. Selective accumulation of the heat shock protein hsc73.
Exosomes are membrane vesicles secreted by hematopoietic cells upon fusion of late multivesicular endosomes with the plasma membrane. Dendritic cell (DC)-derived exosomes induce potent antitumor immune responses in mice, resulting in the regression of established tumors (Zitvogel, L., A. Regnault, A. Lozier, J. Wolfers, C. Flament, D. Tenza, P. Ricciardi-Castagnoli, G. Raposo, and S. Amigorena. 1998. Nat. Med. 4:594-600). To unravel the molecular basis of exosome-induced immune stimulation, we now analyze the regulation of their production during DC maturation and characterize extensively their protein composition by peptide mass mapping. Exosomes contain several cytosolic proteins (including annexin II, heat shock cognate protein hsc73, and heteromeric G protein Gi2alpha), as well as different integral or peripherally associated membrane proteins (major histocompatibility complex class II, Mac-1 integrin, CD9, milk fat globule-EGF-factor VIII [MFG-E8]). MFG-E8, the major exosomal component, binds integrins expressed by DCs and macrophages, suggesting that it may be involved in exosome targeting to these professional antigen-presenting cells. Another exosome component is hsc73, a cytosolic heat shock protein (hsp) also present in DC endocytic compartments. hsc73 was shown to induce antitumor immune responses in vivo, and therefore could be involved in the exosome's potent antitumor effects. Finally, exosome production is downregulated upon DC maturation, indicating that in vivo, exosomes are produced by immature DCs in peripheral tissues. Thus, DC-derived exosomes accumulate a defined subset of cellular proteins reflecting their endosomal biogenesis and accounting for their biological function.
Théry
C
C
Institut National de la Santé et de la Recherche Médicale, U520, Institut Curie, 75005 Paris, France.
Regnault
A
A
Garin
J
J
Wolfers
J
J
Zitvogel
L
L
Ricciardi-Castagnoli
P
P
Raposo
G
G
Amigorena
S
S
D000818:Animals; D017306:Annexin A2 / Q000378:metabolism; D000954:Antigens, Surface; D000970:Antineoplastic Agents / Q000276:immunology / Q000378:metabolism; D002454:Cell Differentiation; D002460:Cell Line; D003600:Cytosol / Q000378:metabolism; D003713:Dendritic Cells / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D011992:Endosomes / Q000737:chemistry / Q000378:metabolism; D005089:Exocytosis; D050883:HSC70 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins; D006360:Heat-Shock Proteins / Q000276:immunology / Q000378:metabolism*; D000949:Histocompatibility Antigens Class II / Q000378:metabolism; D016023:Integrins / Q000378:metabolism; D008264:Macrophages / Q000166:cytology / Q000276:immunology; D008562:Membrane Glycoproteins / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D008894:Milk Proteins; D008970:Molecular Weight; D009374:Neoplasms, Experimental / Q000276:immunology / Q000378:metabolism / Q000473:pathology; D015388:Organelles / Q000737:chemistry* / Q000378:metabolism* / Q000648:ultrastructure; D010449:Peptide Mapping; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
D017306:Annexin A2; D000954:Antigens, Surface; D000970:Antineoplastic Agents; D050883:HSC70 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins; D006360:Heat-Shock Proteins; D000949:Histocompatibility Antigens Class II; C494372:Hspa8 protein, mouse; D016023:Integrins; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; C490919:Mfge8 protein, mouse; D008894:Milk Proteins