title: Exon 6 is essential for invariant chain trimerization and induction of large endosomal structures.
abstract: Invariant chain (Ii) is a transmembrane type II protein that forms a complex with the major histocompatibility complex (MHC) class II molecules in the endoplasmic reticulum (ER). The membrane proximal luminal region of Ii is responsible for the non-covalent association with MHC class II molecules. Chemical cross-linking in COS cells was used to study the effect of luminal and cytoplasmic deletions on trimerization of Ii. We demonstrate that trimerization of Ii is independent of the cytosolic tail of Ii, whereas residues 162-191 (the sequence encoded by exon 6) in the luminal part of Ii are essential for trimer formation. Immunofluorescence studies of the transfected luminal deletion constructs show that the amino acids encoded by exon 6 of Ii are also essential for the induction of large endosomal vesicles. The data suggest that Ii must be in a trimeric form to modify the endosomal pathway.
authors.affiliation: Division of Molecular Cell Biology, Department of Biology, University of Oslo, N-0316 Oslo, Norway.
authors.forename: M
authors.initials: M
authors.lastname: Gedde-Dahl
authors.forename: I
authors.initials: I
authors.lastname: Freisewinkel
authors.forename: M
authors.initials: M
authors.lastname: Staschewski
authors.forename: K
authors.initials: K
authors.lastname: Schenck
authors.forename: N
authors.initials: N
authors.lastname: Koch
authors.forename: O
authors.initials: O
authors.lastname: Bakke
mesh_terms: D000595:Amino Acid Sequence; D000596:Amino Acids / Q000032:analysis / Q000235:genetics; D000818:Animals; D015703:Antigens, CD / Q000378:metabolism*; D000944:Antigens, Differentiation, B-Lymphocyte / Q000378:metabolism*; D000951:Antigens, Neoplasm / Q000378:metabolism*; D019556:COS Cells; D011992:Endosomes / Q000378:metabolism*; D005091:Exons; D000949:Histocompatibility Antigens Class II / Q000378:metabolism*; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D009363:Neoplasm Proteins / Q000378:metabolism*; D011487:Protein Conformation; D017384:Sequence Deletion; D013329:Structure-Activity Relationship; D014162:Transfection
chemical_list: D000596:Amino Acids; D015703:Antigens, CD; D000944:Antigens, Differentiation, B-Lymphocyte; D000951:Antigens, Neoplasm; D000949:Histocompatibility Antigens Class II; D009363:Neoplasm Proteins; C045084:invariant chain