Tumor-associated Tn-MUC1 glycoform is internalized through the macrophage galactose-type C-type lectin and delivered to the HLA class I and II compartments in dendritic cells.
The type of interaction between tumor-associated antigens and specialized antigen-presenting cells such as dendritic cells (DCs) is critical for the type of immunity that will be generated. MUC1, a highly O-glycosylated mucin, is overexpressed and aberrantly glycosylated in several tumor histotypes. This results in the expression of tumor-associated glycoforms and in MUC1 carrying the tumor-specific glycan Tn (GalNAcalpha1-O-Ser/Thr). Glycopeptides corresponding to three tandem repeats of MUC1, enzymatically glycosylated with 9 or 15 mol of GalNAc, were shown to specifically bind and to be internalized by immature monocyte-derived DCs (iDCs). Binding required calcium and the GalNAc residue and was competed out by GalNAc polymer and Tn-MUC1 or Tn-MUC2 glycopeptides. The macrophage galactose-type C-type lectin (MGL) receptor expressed on iDCs was shown to be responsible for the binding. Confocal analysis and ELISA done on subcellular fractions of iDCs showed that the Tn-MUC1 glycopeptides colocalized with HLA class I and II compartments after internalization. Importantly, although Tn-MUC1 recombinant protein was bound and internalized by MGL, the glycoprotein entered the HLA class II compartment, but not the HLA class I pathway. These data indicate that MGL expressed on iDCs is an optimal receptor for the internalization of short GalNAcs carrying immunogens to be delivered into HLA class I and II compartments. Such glycopeptides therefore represent a new way of targeting the HLA class I and II pathways of DCs. These results have possible implications in designing cancer vaccines.
Napoletano
Chiara
C
Department of Experimental Medicine, University of Rome Sapienza, IRCCS San Raffaele Pisana, Rome, Italy.
Rughetti
Aurelia
A
Agervig Tarp
Mads P
MP
Coleman
Julia
J
Bennett
Eric P
EP
Picco
Gianfranco
G
Sale
Patrizio
P
Denda-Nagai
Kaori
K
Irimura
Tatsuro
T
Mandel
Ulla
U
Clausen
Henrik
H
Frati
Luigi
L
Taylor-Papadimitriou
Joyce
J
Burchell
Joy
J
Nuti
Marianna
M
D015295:Antigens, Tumor-Associated, Carbohydrate / Q000737:chemistry / Q000378:metabolism*; D002478:Cells, Cultured; D003713:Dendritic Cells / Q000378:metabolism*; D004705:Endocytosis / Q000276:immunology; D006031:Glycosylation; D015395:Histocompatibility Antigens Class I / Q000378:metabolism*; D000949:Histocompatibility Antigens Class II / Q000378:metabolism*; D006801:Humans; D020014:K562 Cells; D037181:Lectins, C-Type / Q000378:metabolism*; D018396:Mucin-1 / Q000737:chemistry / Q000378:metabolism*; D020033:Protein Isoforms / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism