Max Planck Institute of Immunobiology and Epigenetics, 79108 Freiburg, Germany.
J Biol Chem. 2012 Dec 14;287(51):42664-74. doi: 10.1074/jbc.M112.386045. Epub 2012 Oct 22.
The T-cell antigen receptor (TCR) exists in monomeric and nanoclustered forms independently of antigen binding. Although the clustering is involved in the regulation of T-cell sensitivity, it is unknown how the TCR nanoclusters form. We show that cholesterol is required for TCR nanoclustering in T cells and that this clustering enhances the avidity but not the affinity of the TCR-antigen interaction. Investigating the mechanism of the nanoclustering, we found that radioactive photocholesterol specifically binds to the TCRβ chain in vivo. In order to reduce the complexity of cellular membranes, we used a synthetic biology approach and reconstituted the TCR in liposomes of defined lipid composition. Both cholesterol and sphingomyelin were required for the formation of TCR dimers in phosphatidylcholine-containing large unilamellar vesicles. Further, the TCR was localized in the liquid disordered phase in giant unilamellar vesicles. We propose a model in which cholesterol and sphingomyelin binding to the TCRβ chain causes TCR dimerization. The lipid-induced TCR nanoclustering enhances the avidity to antigen and thus might be involved in enhanced sensitivity of memory compared with naive T cells. Our work contributes to the understanding of the function of specific nonannular lipid-membrane protein interactions.
T 细胞抗原受体 (TCR) 存在于单体和纳米聚集体形式中，与抗原结合无关。尽管聚集参与了 T 细胞敏感性的调节，但 TCR 纳米聚集体如何形成尚不清楚。我们表明胆固醇是 T 细胞中 TCR 纳米聚集所必需的，并且这种聚集增强了 TCR-抗原相互作用的亲合力而非亲和力。研究纳米聚集的机制，我们发现放射性光胆固醇在体内特异性结合 TCRβ 链。为了降低细胞膜的复杂性，我们使用合成生物学方法在具有明确定义脂质组成的脂质体中重新构建 TCR。胆固醇和神经鞘磷脂对于含有卵磷脂的大单层囊泡中 TCR 二聚体的形成都是必需的。此外，TCR 在巨大的单层囊泡中定位于无序的液态相中。我们提出了一个模型，其中胆固醇和神经鞘磷脂与 TCRβ 链结合导致 TCR 二聚化。脂质诱导的 TCR 纳米聚集增强了对抗原的亲合力，因此可能与记忆 T 细胞相比增强了对幼稚 T 细胞的敏感性有关。我们的工作有助于理解特定的非环形脂质-膜蛋白相互作用的功能。
