title: A threonine-based targeting signal in the human CD1d cytoplasmic tail controls its functional expression.
abstract: CD1d molecules are MHC class I-like molecules that present lipids to a unique subpopulation of T cells called NKT cells. The cytoplasmic tail of human CD1d possesses a tyrosine-based endosomal targeting motif (YXXZ). As such, these molecules traffic through the endocytic pathway, where it is believed that they are loaded with the antigenic lipid that stimulates NKT cells. In the current study, it was found that the T322 residue in the human CD1d tail is a major signal controlling transport to the cell surface and thus its functional expression. Mimicking the phosphorylation of this residue or removal of the entire cytoplasmic tail negates its ability to regulate CD1d trafficking, resulting in lysosomal targeting and degradation. These results demonstrate an important role of a heretofore unknown signal in the cytoplasmic tail of CD1d that may have relevance to other type I integral membrane proteins that traverse through the endocytic pathway.
authors.affiliation: Department of Microbiology and Immunology, Indiana University School of Medicine, Indianapolis, IN 46202, USA.
authors.forename: Jianyun
authors.initials: J
authors.lastname: Liu
authors.forename: Daniel
authors.initials: D
authors.lastname: Shaji
authors.forename: Sungyoo
authors.initials: S
authors.lastname: Cho
authors.forename: Wenjun
authors.initials: W
authors.lastname: Du
authors.forename: Jacquelyn
authors.initials: J
authors.lastname: Gervay-Hague
authors.forename: Randy R
authors.initials: RR
authors.lastname: Brutkiewicz
mesh_terms: D020816:Amino Acid Motifs / Q000235:genetics / Q000276:immunology; D019943:Amino Acid Substitution / Q000235:genetics / Q000276:immunology; D055610:Antigens, CD1d / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D002460:Cell Line; D002461:Cell Line, Transformed; D002478:Cells, Cultured; D018920:Coculture Techniques; D003593:Cytoplasm / Q000737:chemistry / Q000235:genetics / Q000276:immunology*; D004705:Endocytosis / Q000235:genetics / Q000276:immunology; D005786:Gene Expression Regulation / Q000276:immunology*; D018390:Gene Targeting; D006801:Humans; D008565:Membrane Proteins / Q000737:chemistry / Q000145:classification / Q000502:physiology; D055611:Natural Killer T-Cells / Q000276:immunology / Q000378:metabolism; D017434:Protein Structure, Tertiary / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology; D015398:Signal Transduction / Q000235:genetics / Q000276:immunology*; D013912:Threonine / Q000737:chemistry / Q000235:genetics / Q000502:physiology*
chemical_list: D055610:Antigens, CD1d; C526877:CD1D protein, human; D008565:Membrane Proteins; D011993:Recombinant Fusion Proteins; D013912:Threonine