title: Enhanced T-cell signaling in cells bearing linker for activation of T-cell (LAT) molecules resistant to ubiquitylation.
abstract: Linker for activation of T cells (LAT) plays a central role in T-cell activation by nucleating signaling complexes that are critical for the propagation of T-cell signals from the plasma membrane to the cellular interior. The role of phosphorylation and palmitoylation in LAT function has been well studied, but not much is known about other strategies by which the cell modulates LAT activity. We have focused on LAT ubiquitylation and have mapped the sites on which LAT is ubiquitylated. To elucidate the biological role of this process, we substituted LAT lysines with arginines. This resulted in a dramatic decrease in overall LAT ubiquitylation. Ubiquitylation-resistant mutants of LAT were internalized at rates comparable to wild-type LAT in a mechanism that required Cbl family proteins. However, these mutants displayed a defect in protein turnover rates. T-cell signaling was elevated in cells reconstituted with LAT mutants resistant to ubiquitylation, indicating that inhibition of LAT ubiquitylation enhances T-cell potency. These results support LAT ubiquitylation as a molecular checkpoint for attenuation of T-cell signaling.
authors.affiliation: Laboratory of Cellular and Molecular Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: Lakshmi
authors.initials: L
authors.lastname: Balagopalan
authors.forename: Benjamin A
authors.initials: BA
authors.lastname: Ashwell
authors.forename: Kelsie M
authors.initials: KM
authors.lastname: Bernot
authors.forename: Itoro O
authors.initials: IO
authors.lastname: Akpan
authors.forename: Naeha
authors.initials: N
authors.lastname: Quasba
authors.forename: Valarie A
authors.initials: VA
authors.lastname: Barr
authors.forename: Lawrence E
authors.initials: LE
authors.lastname: Samelson
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D000911:Antibodies, Monoclonal; D019556:COS Cells; D002522:Chlorocebus aethiops; D017931:DNA Primers / Q000235:genetics; D005434:Flow Cytometry; D005453:Fluorescence; D006801:Humans; D015151:Immunoblotting; D047468:Immunoprecipitation; D019169:Jurkat Cells; D008213:Lymphocyte Activation / Q000502:physiology*; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D018613:Microscopy, Confocal; D009154:Mutation / Q000235:genetics; D016133:Polymerase Chain Reaction; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000235:genetics; D015398:Signal Transduction / Q000276:immunology*; D013601:T-Lymphocytes / Q000502:physiology*; D014162:Transfection; D054875:Ubiquitination
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D000911:Antibodies, Monoclonal; D017931:DNA Primers; C110810:LAT protein, human; D008565:Membrane Proteins; D034741:RNA, Small Interfering