T-cell antigen receptor-induced signaling complexes: internalization via a cholesterol-dependent endocytic pathway.
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.
Barr
Valarie A
VA
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.
Balagopalan
Lakshmi
L
Barda-Saad
Mira
M
Polishchuk
Roman
R
Boukari
Hacène
H
Bunnell
Stephen C
SC
Bernot
Kelsie M
KM
Toda
Yoko
Y
Nossal
Ralph
R
Samelson
Lawrence E
LE
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*
D048868:Adaptor Proteins, Signal Transducing; D010750:Phosphoproteins; D011948:Receptors, Antigen, T-Cell; C092947:SLP-76 signal Transducing adaptor proteins; D002784:Cholesterol