title: DOα⁻β⁺ expression in favor of HLA-DR engagement in exosomes.
abstract: The expression of DOβ and not DOα, in addition to the high intracellular DR, low DM levels and absence of surface DR expression in K562 and HL-60 cells introduce alternative regulatory pathways in DR trafficking and consequently the antigen presentation process. The present study attempted to define the naturally occurring DOα negative state and explain the role of DOβ in the intracellular DR accumulation in K562 and HL-60 cells. Despite the absence of DOα, the DOβ chain was detected in the endosomal compartments. The lack of DOα was found to be partially responsible for the absence of DR from the cell membrane since stable K562-DOα transfectants allowed expression of membrane DR. This expression could be significantly increased upon DM induction by IFN-γ, indicating that DM was another limiting factor for the migration of DR to the cell surface of K562 and HL-60 cells. Furthermore, intracellular DR co-localized with the exosome specific marker CD9, while culture supernatants were shown to contain exosome-engaged and exosome free DR activity as evaluated by SDS-page followed by western blot, ELISA and transmission electron microscopy analysis. These findings indicated that in DOα⁻β⁺ cells, DR molecules were programmed to secretion rather than surface expression. The presented results provide novel regulatory processes as to DR trafficking, avoiding expression to the cell surface.
authors: Department of Biology, Laboratory of Immunology, University of Crete, Heraklion 71409, Crete, Greece.
authors: Lina
authors: L
authors: Papadimitriou
authors: Ioanna
authors: I
authors: Zerva
authors: Mirella
authors: M
authors: Georgouli
authors: Takis
authors: T
authors: Makatounakis
authors: Joseph
authors: J
authors: Papamatheakis
authors: Irene
authors: I
authors: Athanassakis
mesh_terms: D017951:Antigen Presentation / Q000276:immunology*; D045744:Cell Line, Tumor; D055354:Exosomes; D018922:HL-60 Cells; D006681:HLA-D Antigens / Q000096:biosynthesis / Q000276:immunology* / Q000378:metabolism; D006684:HLA-DR Antigens / Q000276:immunology*; D006801:Humans; D007371:Interferon-gamma; D020014:K562 Cells; D021381:Protein Transport / Q000276:immunology*
chemical_list: D006681:HLA-D Antigens; C084245:HLA-DM antigens; C046148:HLA-DO antigens; D006684:HLA-DR Antigens; D007371:Interferon-gamma