The transmembrane region of CD2-associated signal-transducing proteins is crucial for the outcome of CD2-mediated T-cell activation.
Signalling through the CD2 molecule was shown previously to employ similar signalling molecules as the T-cell receptor (TCR). Here, we show that CD2-mediated signalling is strongly influenced by the expressed transmembrane region of the employed signal-transducing molecule. We used TCR-negative cells expressing chimeric fusion proteins that consist of human interleukin-2 (IL-2) receptor alpha-chain-derived sequences (hCD25) fused to mouse-specific zeta-chain segments (hCD25-zeta). One set of TCR-negative cell lines expressed the hCD25-derived extracellular part fused to mouse-specific transmembrane and cytoplasmic zeta-protein sequences ('TZZ'). The second type of cell lines expressed the hCD25-derived extracellular and transmembrane portions fused to the mouse-specific zeta-chain cytoplasmic segment ('TTZ'). After cross-linking the hCD25-zeta molecules with specific monoclonal antibodies (mAb), all TCR-negative cell lines produced similar amounts of IL-2. Cross-linking with stimulating pairs of CD2-specific mAb, however, led to IL-2 production only in cell lines expressing the zeta-chain-specific transmembrane segment. Co-cross-linking of CD25 and CD2 molecules resulted in an effective stimulation of both TZZ- and TTZ-expressing cell lines. Moreover, TTZ- and TZZ-expressing cell lines differed in their pattern of tyrosine-phosphorylated proteins after stimulation with hCD25-specific mAb. Thus, although CD2 and TCR molecules share signalling components and pathways, the fine tuning of CD2 co-receptor function appears to be regulated in part by transmembrane regions of signal-transducing molecules like the TCR-associated zeta-chain.
Von Bonin
A
A
Bernhard-Nocht Institute for Tropical Medicine, Hamburg, Germany.
Ehrlich
S
S
Fleischer
B
B
D000911:Antibodies, Monoclonal / Q000494:pharmacology; D018801:CD2 Antigens / Q000276:immunology*; D002478:Cells, Cultured; D006801:Humans; D006825:Hybridomas; D007376:Interleukin-2 / Q000378:metabolism; D008213:Lymphocyte Activation; D011948:Receptors, Antigen, T-Cell / Q000276:immunology*; D015375:Receptors, Interleukin-2 / Q000276:immunology*; D015398:Signal Transduction / Q000502:physiology*; D013601:T-Lymphocytes / Q000276:immunology*
D000911:Antibodies, Monoclonal; D018801:CD2 Antigens; D007376:Interleukin-2; D011948:Receptors, Antigen, T-Cell; D015375:Receptors, Interleukin-2