Conserved Vdelta1 binding geometry in a setting of locus-disparate pHLA recognition by delta/alphabetaTCRs: insight into recognition of HIV peptides by TCR----中国科学院微生物研究所

科研成果

论文题目:	Conserved Vdelta1 binding geometry in a setting of locus-disparate pHLA recognition by delta/alphabetaTCRs: insight into recognition of HIV peptides by TCR
作者:	Shi Yi, Kawana-Tachikawa Ai, Gao Feng, Qi Jianxun, Liu Chuansheng, Gao Jia, Cheng Hao, Ueno Takamasa, Iwamoto Aikichi, and Gao George F*.
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刊物名称:	J Virol
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年份:	2017
影响因子:	4.272
论文下载:	http://jvi.asm.org/content/91/17/e00725-17
摘要:	Given a limited set of TCR V genes which are used to create TCRs that are reactive to different ligands, such as MHC class I, MHC class II and MHC-like proteins (for example, MIC molecules and CD1 molecules), the Vdelta1 segment can be rearranged with Ddelta-Jdelta-Cdelta or Jalpha-Calpha segments, to form classical gammadeltaTCR or uncommon alphabetaTCR using a Vdelta1 segment (delta/alphabetaTCR). Here we have determined two complex structures of the delta/alphabetaTCRs (S19-2 and TU55) bound to different locus-disparate MHCIs with HIV peptides (HLA-A2402-Nef138-10 and HLA-B3501-Pol448-9). The overall binding modes resemble classical alphabetaTCRs, but display a strong tilt binding geometry of Vdelta1 domain towards the HLA alpha1 helix, due to a conserved extensive interaction between the CDR1delta loop and N-terminal region of alpha1 helix (mainly in position 62). The aromatic amino acids of the CDR1delta loop exploit different conformations ("aromatic-ladder" or "aromatic-hairpin") to accommodate distinct MHC helical scaffolds. This tolerance helps to explain how a particular TCR V region can similarly dock onto multiple MHC molecules, and thus, may potentially explain the nature of TCR cross-reactivity. In addition, the length of CDR3delta loop could affect the extent of tilt binding of Vdelta1 domain, and adaptively, the pairing Vbeta domains adjust their mass centers to generate differential MHC contacts, hence probably ensuring the TCR specificity to a certain peptide-MHC. Our data have provided further structural insights into the TCR recognition of classical pMHCI molecules, unifying the cross-reactivity and specificity together.IMPORTANCE The specificity of alphabeta T cell recognition is determined by the CDR loops of the alphabetaTCR and the general binding mode of alphabetaTCRs to pMHC has been established over the last decade. Due to the intrinsic genomic structure of the TCR alpha/delta chain locus, some Vdelta segments can rearrange with Calpha segment, forming a hybrid VdeltaCalphaVbetaCbeta TCR, delta/alphabetaTCR. However, the basis for the molecular recognition of such TCRs to their ligands is elusive. Here, an alphabetaTCR using Vdelta1 segment, S19-2, is isolated from a HIV-infected patient, in an HLA-A*24:02 restricted manner. Then we solved the crystal structures of S19-2 TCR and another delta/alphabetaTCR TU55 binding to their ligands respectively, revealing a conserved Vdelta1 binding feature. Further binding kinetics analysis reveals that the S19-2 and TU55 TCRs bind pHLA very tightly and long-lastingly. Our results illustrate the binding mode of a TCR using Vdelta1 segment to its ligand, virus-derived pHLA.