T-cell antigen receptor-induced signaling complexes: Internalization via a cholesterol-dependent endocytic pathway

Valarie A. Barr, Lakshmi Balagopalan, Mira Barda-Saad, Roman Polishchuk, Hacène Boukari, Stephen C. Bunnell, Kelsie M. Bernot, Yoko Toda, Ralph Nossal, Lawrence E. Samelson

Research output: Contribution to journalArticlepeer-review

72 Scopus citations


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°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.

Original languageEnglish
Pages (from-to)1143-1162
Number of pages20
Issue number9
StatePublished - Sep 2006
Externally publishedYes


  • Adapter proteins
  • Confocal microscopy
  • Endocytosis
  • Lipid rafts
  • Signaling complexes
  • T-cell activation
  • Ubiquitin


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