TCR signal initiation machinery is pre-assembled and activated in a subset of membrane rafts.
Recent studies suggest that rafts are involved in numerous cell functions, including membrane traffic and signaling. Here we demonstrate, using a polyoxyethylene ether Brij 98, that detergent-insoluble microdomains possessing the expected biochemical characteristics of rafts are present in the cell membrane at 37 degrees C. After extraction, these microdomains are visualized as membrane vesicles with a mean diameter of approximately 70 nm. These findings provide further evidence for the existence of rafts under physiological conditions and are the basis of a new isolation method allowing more accurate analyses of raft structure. We found that main components of T cell receptor (TCR) signal initiation machinery, i.e. TCR-CD3 complex, Lck and ZAP-70 kinases, and CD4 co-receptor are constitutively partitioned into a subset of rafts. Functional studies in both intact cells and isolated rafts showed that upon ligation, TCR initiates the signaling in this specialized raft subset. Our data thus strongly indicate an important role of rafts in organizing TCR early signaling pathways within small membrane microdomains, both prior to and following receptor engagement, for efficient TCR signal initiation upon stimulation.
Drevot
Philippe
P
Centre d'Immunologie de Marseille-Luminy, CNRS-INSERM-Université de la Mediterranee, Case 906, F-13288 Marseille Cedex 9, France.
Langlet
Claire
C
Guo
Xiao-Jun
XJ
Bernard
Anne-Marie
AM
Colard
Odile
O
Chauvin
Jean-Paul
JP
Lasserre
Rémi
R
He
Hai-Tao
HT
D015704:CD4 Antigens / Q000378:metabolism; D002460:Cell Line; D003902:Detergents; D006801:Humans; D021962:Membrane Microdomains / Q000378:metabolism*; D010938:Plant Oils; D011092:Polyethylene Glycols; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D017260:Receptor-CD3 Complex, Antigen, T-Cell / Q000378:metabolism*; D015398:Signal Transduction; D012995:Solubility; D051746:ZAP-70 Protein-Tyrosine Kinase
D015704:CD4 Antigens; D003902:Detergents; D010938:Plant Oils; D017260:Receptor-CD3 Complex, Antigen, T-Cell; D011092:Polyethylene Glycols; C033084:polyethylene glycol oleyl ether; D011505:Protein-Tyrosine Kinases; D051746:ZAP-70 Protein-Tyrosine Kinase; C497261:ZAP70 protein, human