CD3δ Establishes a Functional Link between the T Cell Receptor and CD8

doi:10.1074/jbc.M208119200

CD3δ Establishes a Functional Link between the T Cell Receptor and CD8*

From the ^‡Institute for Biochemistry, University of Lausanne, Epalinges 1066, Switzerland, the ^¶Ludwig Institute for Cancer Research, Lausanne Branch, University of Lausanne, Epalinges 1066, Switzerland, and the ^‖Laboratory of Transplantation Immunology and Nephrology, University Hospital Basel, Basel 4031, Switzerland

Abstract

T cells expressing T cell receptor (TCR) complexes that lack CD3δ, either due to deletion of the CD3δgene, or by replacement of the connecting peptide of the TCRα chain, exhibit severely impaired positive selection and TCR-mediated activation of CD8 single-positive T cells. Because the same defects have been observed in mice expressing no CD8β or tailless CD8β, we examined whether CD3δ serves to couple TCR·CD3 with CD8. To this end we used T cell hybridomas and transgenic mice expressing the T1 TCR, which recognizes a photoreactive derivative of the PbCS 252–260 peptide in the context of H-2K^d. We report that, in thymocytes and hybridomas expressing the T1 TCR·CD3 complex, CD8αβ associates with the TCR. This association was not observed on T1 hybridomas expressing only CD8αα or a CD3δ⁻ variant of the T1 TCR. CD3δ was selectively co-immunoprecipitated with anti-CD8 antibodies, indicating an avid association of CD8 with CD3δ. Because CD8αβ is a raft constituent, due to this association a fraction of TCR·CD3 is raft-associated. Cross-linking of these TCR-CD8 adducts results in extensive TCR aggregate formation and intracellular calcium mobilization. Thus, CD3δ couples TCR·CD3 with raft-associated CD8, which is required for effective activation and positive selection of CD8⁺ T cells.

Footnotes

↵* This work was supported by grants from the Swiss National Foundation (Grant 31-61946.00) and the Sandoz Foundation.The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
↵§ Both authors contributed equally to the work.
↵** To whom correspondence should be addressed. Tel.: 41-21-692-5988; Fax: 41-21-653-4474; E-mail: iluesche@eliot.unil.ch.
Published, JBC Papers in Press, September 4, 2002, DOI 10.1074/jbc.M208119200
↵2 M.-A. Doucey, L. Goffin, D. Naeher, O. Michielin, P. Baumgärtner, P. Guillaume, E. Palmer, and I. F. Luescher, unpublished results.
Abbreviations:

DP

CD4⁺CD8⁺ double-positive thymocytes

SP

single-positive

ABA

4-azidobenzoic acid

αCPM

TCRα chain connecting peptide motif

DN

CD4⁻CD8⁻double-negative thymocytes

FRET

fluorescence resonance energy transfer

IASA

iodo-4-azidosalicylic acid

LAT

linker for activation of T cells

PbCS

Plasmodium berghei circumsporozoite

TCR

T cell receptor

TCR αIV/βIII

TCR in which residues 225–270 of the α chain and residues 270–300 of the β chain are replaced with the corresponding sequences of the TCRδ and γ chain, respectively

mAb

monoclonal antibody

FACS

fluorescence-activated cell sorting

DMEM

Dulbecco's modified Eagle's medium

BSA

bovine serum albumin

PBS

phosphate-buffered saline

MES

4-morpholineethanesulfonic acid

MHC

major histocompatibility complex
- Received August 8, 2002.
- Revision received September 4, 2002.
The American Society for Biochemistry and Molecular Biology, Inc.