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Signaling efficiency of the T cell receptor controlled by a single amino acid in the beta chain constant region.

Bäckström BT, Hausmann BT, Palmer E - J. Exp. Med. (1997)

Bottom Line: TCRs in which this Cbeta residue is mutated to Phe, the residue found in TCR-gamma, are unresponsive to antigenic ligands.However, the biological response of the mutant TCR could be rescued with a calcium ionophore, implying that mutant TCRs are defective in generating a calcium-mediated signal.The implications of the differences between Cbeta and Cgamma are considered.

View Article: PubMed Central - PubMed

Affiliation: Basel Institute for Immunology, CH-4005 Basel, Switzerland.

ABSTRACT
A single amino acid residue, Gln136, located within the connecting peptide domain of Cbeta controls the ability of the alpha/beta TCR to transmit a full signal. TCRs in which this Cbeta residue is mutated to Phe, the residue found in TCR-gamma, are unresponsive to antigenic ligands. Interestingly, this Cbeta residue is either polar or charged in every species studied thus far, including the trout and the skate. In contrast, the analogous residue in Cgamma is always hydrophobic. In spite of their compromised antigen responsiveness, the mutant TCR complex contains the CD3-gamma, -delta, -epsilon, and -zeta chains, and undergoes zeta chain phosphorylation and ZAP-70 recruitment. However, the biological response of the mutant TCR could be rescued with a calcium ionophore, implying that mutant TCRs are defective in generating a calcium-mediated signal. The implications of the differences between Cbeta and Cgamma are considered.

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Point mutation of Gln136 affects antigen responsiveness. Hybridomas expressing the wt TCR-α chain and wt or mutant β chains  were stimulated with DAP.3-DR1–presenting cells and SEB as described  in Fig. 2. IL-2 and IL-3 responses are shown in A and B, respectively. Sequences of the CP domains from different species (22, 23) are shown in  C, using the single letter amino acid codes. Sequences were aligned using  the Lasergene Navigator MegAlign Software program (Clustal alignment  method with the PAM250 residue weight table). The conserved amino  acids present in the TCR-β and γ chain CP domains are indicated in  boldface.
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Figure 5: Point mutation of Gln136 affects antigen responsiveness. Hybridomas expressing the wt TCR-α chain and wt or mutant β chains were stimulated with DAP.3-DR1–presenting cells and SEB as described in Fig. 2. IL-2 and IL-3 responses are shown in A and B, respectively. Sequences of the CP domains from different species (22, 23) are shown in C, using the single letter amino acid codes. Sequences were aligned using the Lasergene Navigator MegAlign Software program (Clustal alignment method with the PAM250 residue weight table). The conserved amino acids present in the TCR-β and γ chain CP domains are indicated in boldface.

Mentions: The functional chimera, βV, contains the β chain sequence ASYQQ, which has been replaced with the γ chain sequence, LQFQF, in the nonfunctional chimeric chain, βVI (Fig. 1 A). The most striking amino acids in this region are Tyr134 and Gln136, both of which are encoded by Phe in murine Cγ1. Point mutations were introduced into the wt β chain cDNA, and the resulting mutant β chains were paired with an αwt chain and were tested for their reactivity to SEB. As seen in Fig. 5, A and B, the Tyr134 → Phe mutation had a negligible effect on the response to SEB, whereas TCRs carrying the Gln136 → Phe mutation had a marked and reproducible effect on SEB responsiveness. Considering the pronounced effect of the Gln136 → Phe exchange on superantigen responsiveness, we examined the amino acid residues present at this position in all Cβ and Cγ sequences, some of which are shown in Fig. 5 C. Strikingly, the amino acids at this position in the β chain are always polar or charged. In contrast, γ chains always contain hydrophobic amino acids at this position (Fig. 5 C and reference 23).


Signaling efficiency of the T cell receptor controlled by a single amino acid in the beta chain constant region.

Bäckström BT, Hausmann BT, Palmer E - J. Exp. Med. (1997)

Point mutation of Gln136 affects antigen responsiveness. Hybridomas expressing the wt TCR-α chain and wt or mutant β chains  were stimulated with DAP.3-DR1–presenting cells and SEB as described  in Fig. 2. IL-2 and IL-3 responses are shown in A and B, respectively. Sequences of the CP domains from different species (22, 23) are shown in  C, using the single letter amino acid codes. Sequences were aligned using  the Lasergene Navigator MegAlign Software program (Clustal alignment  method with the PAM250 residue weight table). The conserved amino  acids present in the TCR-β and γ chain CP domains are indicated in  boldface.
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Related In: Results  -  Collection

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Figure 5: Point mutation of Gln136 affects antigen responsiveness. Hybridomas expressing the wt TCR-α chain and wt or mutant β chains were stimulated with DAP.3-DR1–presenting cells and SEB as described in Fig. 2. IL-2 and IL-3 responses are shown in A and B, respectively. Sequences of the CP domains from different species (22, 23) are shown in C, using the single letter amino acid codes. Sequences were aligned using the Lasergene Navigator MegAlign Software program (Clustal alignment method with the PAM250 residue weight table). The conserved amino acids present in the TCR-β and γ chain CP domains are indicated in boldface.
Mentions: The functional chimera, βV, contains the β chain sequence ASYQQ, which has been replaced with the γ chain sequence, LQFQF, in the nonfunctional chimeric chain, βVI (Fig. 1 A). The most striking amino acids in this region are Tyr134 and Gln136, both of which are encoded by Phe in murine Cγ1. Point mutations were introduced into the wt β chain cDNA, and the resulting mutant β chains were paired with an αwt chain and were tested for their reactivity to SEB. As seen in Fig. 5, A and B, the Tyr134 → Phe mutation had a negligible effect on the response to SEB, whereas TCRs carrying the Gln136 → Phe mutation had a marked and reproducible effect on SEB responsiveness. Considering the pronounced effect of the Gln136 → Phe exchange on superantigen responsiveness, we examined the amino acid residues present at this position in all Cβ and Cγ sequences, some of which are shown in Fig. 5 C. Strikingly, the amino acids at this position in the β chain are always polar or charged. In contrast, γ chains always contain hydrophobic amino acids at this position (Fig. 5 C and reference 23).

Bottom Line: TCRs in which this Cbeta residue is mutated to Phe, the residue found in TCR-gamma, are unresponsive to antigenic ligands.However, the biological response of the mutant TCR could be rescued with a calcium ionophore, implying that mutant TCRs are defective in generating a calcium-mediated signal.The implications of the differences between Cbeta and Cgamma are considered.

View Article: PubMed Central - PubMed

Affiliation: Basel Institute for Immunology, CH-4005 Basel, Switzerland.

ABSTRACT
A single amino acid residue, Gln136, located within the connecting peptide domain of Cbeta controls the ability of the alpha/beta TCR to transmit a full signal. TCRs in which this Cbeta residue is mutated to Phe, the residue found in TCR-gamma, are unresponsive to antigenic ligands. Interestingly, this Cbeta residue is either polar or charged in every species studied thus far, including the trout and the skate. In contrast, the analogous residue in Cgamma is always hydrophobic. In spite of their compromised antigen responsiveness, the mutant TCR complex contains the CD3-gamma, -delta, -epsilon, and -zeta chains, and undergoes zeta chain phosphorylation and ZAP-70 recruitment. However, the biological response of the mutant TCR could be rescued with a calcium ionophore, implying that mutant TCRs are defective in generating a calcium-mediated signal. The implications of the differences between Cbeta and Cgamma are considered.

Show MeSH