Intracellular transport of invariant chain-MHC class II complexes to the peptide-loading compartment.
Th cells recognize peptide fragments of foreign Ags bound to MHC class II molecules. Upon synthesis in the endoplasmic reticulum, the alpha- and beta-chains of the class II molecules rapidly associate with invariant chains (li). The dissociation of li from class II molecules precedes binding of processed Ag and the formation of SDS-stable alpha beta dimers. We previously showed that functional, processed Ag-class II complexes are assembled in a dense lysosome-like compartment that contains stable class II molecules, but no li, referred to in this work as the peptide-loading compartment. We also identified a separate compartment that contains predominantly SDS-unstable li-class II complexes. Because we were unable to identify known organelle markers associated with this compartment, we refer to it as the X compartment. In this work, we provide results that indicate that the X compartment is composed of transport vesicles that move li-class II complexes to the peptide-loading compartment, where all events in the assembly of processed Ag-class II complexes occur.
Xu
X
X
Department of Biochemistry, Molecular Biology, and Cell Biology, Northwestern University, Evanston, IL 60208, USA.
Song
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W
Cho
H
H
Qiu
Y
Y
Pierce
S K
SK
D000944:Antigens, Differentiation, B-Lymphocyte / Q000502:physiology*; D001692:Biological Transport; D002451:Cell Compartmentation; D002460:Cell Line; D000949:Histocompatibility Antigens Class II / Q000502:physiology*; D006801:Humans; D008247:Lysosomes / Q000502:physiology; D010455:Peptides; D013601:T-Lymphocytes / Q000502:physiology*
D000944:Antigens, Differentiation, B-Lymphocyte; D000949:Histocompatibility Antigens Class II; D010455:Peptides; C045084:invariant chain