title: T-cell antigen receptor-induced signaling complexes: internalization via a cholesterol-dependent endocytic pathway.
abstract: T-cell antigen receptor engagement causes the rapid assembly of signaling complexes. The adapter protein SLP-76, detected as SLP-yellow fluorescent protein, initially clustered with the TCR and other proteins, then translocated medially on microtubules. As shown by total internal reflection fluorescence microscopy and the inhibition of SLP-76 movement at 16 degrees C, this movement required endocytosis. Immunoelectron microscopy showed SLP-76 staining of smooth pits and tubules. Cholesterol depletion decreased the movement of SLP-76 clusters, as did coexpression of the ubiquitin-interacting motif domain from eps15. These data are consistent with the internalization of SLP-76 via a lipid raft-dependent pathway that requires interaction of the endocytic machinery with ubiquitinylated proteins. The endocytosed SLP-76 clusters contained phosphorylated SLP-76 and phosphorylated LAT. The raft-associated, transmembrane protein LAT likely targets SLP-76 to endocytic vesicles. The endocytosis of active SLP-76 and LAT complexes suggests a possible mechanism for downregulation of signaling complexes induced by TCR activation.
authors.affiliation: Laboratory of Cellular and Molecular Biology, Department of Health and Human Services, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: Valarie A
authors.initials: VA
authors.lastname: Barr
authors.forename: Lakshmi
authors.initials: L
authors.lastname: Balagopalan
authors.forename: Mira
authors.initials: M
authors.lastname: Barda-Saad
authors.forename: Roman
authors.initials: R
authors.lastname: Polishchuk
authors.forename: Hacène
authors.initials: H
authors.lastname: Boukari
authors.forename: Stephen C
authors.initials: SC
authors.lastname: Bunnell
authors.forename: Kelsie M
authors.initials: KM
authors.lastname: Bernot
authors.forename: Yoko
authors.initials: Y
authors.lastname: Toda
authors.forename: Ralph
authors.initials: R
authors.lastname: Nossal
authors.forename: Lawrence E
authors.initials: LE
authors.lastname: Samelson
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism*; D002784:Cholesterol / Q000502:physiology*; D004705:Endocytosis / Q000502:physiology*; D006801:Humans; D010750:Phosphoproteins / Q000378:metabolism*; D011948:Receptors, Antigen, T-Cell / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D010750:Phosphoproteins; D011948:Receptors, Antigen, T-Cell; C092947:SLP-76 signal Transducing adaptor proteins; D002784:Cholesterol