title: Intracellular transport of invariant chain-MHC class II complexes to the peptide-loading compartment.
abstract: 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.
authors.affiliation: Department of Biochemistry, Molecular Biology, and Cell Biology, Northwestern University, Evanston, IL 60208, USA.
authors.forename: X
authors.initials: X
authors.lastname: Xu
authors.forename: W
authors.initials: W
authors.lastname: Song
authors.forename: H
authors.initials: H
authors.lastname: Cho
authors.forename: Y
authors.initials: Y
authors.lastname: Qiu
authors.forename: S K
authors.initials: SK
authors.lastname: Pierce
mesh_terms: 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*
chemical_list: D000944:Antigens, Differentiation, B-Lymphocyte; D000949:Histocompatibility Antigens Class II; D010455:Peptides; C045084:invariant chain