title: c-Cbl-mediated regulation of LAT-nucleated signaling complexes.
abstract: The engagement of the T-cell receptor (TCR) causes the rapid recruitment of multiple signaling molecules into clusters with the TCR. Upon receptor activation, the adapters LAT and SLP-76, visualized as chimeric proteins tagged with yellow fluorescent protein, transiently associate with and then rapidly dissociate from the TCR. Previously, we demonstrated that after recruitment into signaling clusters, SLP-76 is endocytosed in vesicles via a lipid raft-dependent pathway that requires the interaction of the endocytic machinery with ubiquitylated proteins. In this study, we focus on LAT and demonstrate that signaling clusters containing this adapter are internalized into distinct intracellular compartments and dissipate rapidly upon TCR activation. The internalization of LAT was inhibited in cells expressing versions of the ubiquitin ligase c-Cbl mutated in the RING domain and in T cells from mice lacking c-Cbl. Moreover, c-Cbl RING mutant forms suppressed LAT ubiquitylation and caused an increase in cellular LAT levels, as well as basal and TCR-induced levels of phosphorylated LAT. Collectively, these data indicate that following the rapid formation of signaling complexes upon TCR stimulation, c-Cbl activity is involved in the internalization and possible downregulation of a subset of activated signaling molecules.
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: Valarie A
authors.initials: VA
authors.lastname: Barr
authors.forename: Connie L
authors.initials: CL
authors.lastname: Sommers
authors.forename: Mira
authors.initials: M
authors.lastname: Barda-Saad
authors.forename: Amrita
authors.initials: A
authors.lastname: Goyal
authors.forename: Matthew S
authors.initials: MS
authors.lastname: Isakowitz
authors.forename: Lawrence E
authors.initials: LE
authors.lastname: Samelson
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism*; D000818:Animals; D019556:COS Cells; D002451:Cell Compartmentation; D002522:Chlorocebus aethiops; D006801:Humans; D019169:Jurkat Cells; D008213:Lymphocyte Activation; D008565:Membrane Proteins / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D010766:Phosphorylation; D011392:Proline / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D050721:Proto-Oncogene Proteins c-cbl / Q000737:chemistry / Q000172:deficiency / Q000378:metabolism*; D011948:Receptors, Antigen, T-Cell / Q000378:metabolism; D015398:Signal Transduction; D013601:T-Lymphocytes / Q000166:cytology / Q000378:metabolism; D054875:Ubiquitination; D051746:ZAP-70 Protein-Tyrosine Kinase / Q000378:metabolism
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C110810:LAT protein, human; D008565:Membrane Proteins; D011948:Receptors, Antigen, T-Cell; D011392:Proline; D050721:Proto-Oncogene Proteins c-cbl; D051746:ZAP-70 Protein-Tyrosine Kinase; C497261:ZAP70 protein, human