title: LAPTM5 promotes lysosomal degradation of intracellular CD3ζ but not of cell surface CD3ζ.
abstract: The lysosomal protein LAPTM5 has been shown to negatively regulate cell surface T cell receptor (TCR) expression and T-cell activation by promoting CD3ζ degradation in lysosomes, but the mechanism remains largely unknown. Here we show that LAPTM5 promotes lysosomal translocation of intracellular CD3ζ but not of the cell surface CD3ζ associated with the mature TCR complex. Kinetic analysis of the subcellular localization of the newly synthesized CD3ζ suggests that LAPTM5 targets CD3ζ in the Golgi apparatus and promotes its lysosomal translocation. Consistently, a Golgi-localizing mutant CD3ζ can be transported to and degraded in the lysosome by LAPTM5. A CD3ζ YF mutant in which all six tyrosine residues in the immunoreceptor tyrosine-based activation motif are mutated to phenylalanines is degraded as efficiently as is wild type CD3ζ, further suggesting that TCR signaling-triggered tyrosine phosphorylation of CD3ζ is dispensable for LAPTM5-mediated degradation. Previously, Src-like adapter protein (SLAP) and E3 ubiquitin ligase c-Cbl have been shown to mediate the ubiquitination of CD3ζ in the internalized TCR complex and its subsequent lysosomal degradation. We show that LAPTM5 and SLAP/c-Cbl function in distinct genetic pathways to negatively regulate TCR expression. Collectively, these results suggest that CD3ζ can be degraded by two pathways: SLAP/c-Cbl, which targets internalized cell surface CD3ζ dependent on TCR signaling, and LAPTM5, which targets intracellular CD3ζ independent of TCR signaling.
authors.affiliation: Laboratory for Immune Diversity, Research Center for Allergy and Immunology, RIKEN Yokohama Institute, Yokohama, Japan.
authors.forename: Yohei
authors.initials: Y
authors.lastname: Kawai
authors.affiliation: Laboratory for Immune Diversity, Research Center for Allergy and Immunology, RIKEN Yokohama Institute, Yokohama, Japan.
authors.forename: Rika
authors.initials: R
authors.lastname: Ouchida
authors.affiliation: Division of Molecular Immunology, Research Center for Infectious Diseases, Medical Institute of Bioregulation, Kyushu University, Fukuoka, Japan.
authors.forename: Sho
authors.initials: S
authors.lastname: Yamasaki
authors.affiliation: National Jewish Health Colorado Children's Hospital, University of Colorado Denver, School of Medicine, Denver, CO, USA.
authors.forename: Leonard
authors.initials: L
authors.lastname: Dragone
authors.affiliation: Department of Immunology, Medical Research Institute, Tokyo Medical and Dental University, Tokyo, Japan.
authors.forename: Takeshi
authors.identifier: 0000000307601258
authors.initials: T
authors.lastname: Tsubata
authors.affiliation: 1] Department of Immunology, Shanghai Medical College, Fudan University, Shanghai, China [2] Department of Immunology, Medical Research Institute, Tokyo Medical and Dental University, Tokyo, Japan.
authors.forename: Ji-Yang
authors.initials: JY
authors.lastname: Wang
mesh_terms: D000818:Animals; D017252:CD3 Complex / Q000235:genetics / Q000276:immunology*; D002462:Cell Membrane / Q000235:genetics / Q000276:immunology; D005786:Gene Expression Regulation / Q000235:genetics / Q000276:immunology; D017874:Immediate-Early Proteins / Q000235:genetics / Q000276:immunology*; D008247:Lysosomes / Q000235:genetics / Q000276:immunology*; D008565:Membrane Proteins / Q000235:genetics / Q000276:immunology*; D051379:Mice; D018345:Mice, Knockout; D021381:Protein Transport / Q000235:genetics / Q000276:immunology; D059748:Proteolysis; D050721:Proto-Oncogene Proteins c-cbl; D016392:Proto-Oncogene Proteins pp60(c-src) / Q000235:genetics / Q000276:immunology; D011948:Receptors, Antigen, T-Cell / Q000235:genetics / Q000276:immunology*; D015398:Signal Transduction / Q000235:genetics / Q000276:immunology*
chemical_list: D017252:CD3 Complex; C485468:Cd3e protein, mouse; D017874:Immediate-Early Proteins; C484408:Laptm5 protein, mouse; D008565:Membrane Proteins; D011948:Receptors, Antigen, T-Cell; C095148:Sla protein, mouse; D050721:Proto-Oncogene Proteins c-cbl; D016392:Proto-Oncogene Proteins pp60(c-src); C493849:Cbl protein, mouse