TSE3调控T细胞受体信号传导及T淋巴细胞发育的分子机制研究

Thymocyte development is tightly regulated at the molecular level, which is also a hot research area in recent years. We have previously identified a new molecule involved in T cell development named TSE3(Thymocyts-specific Expression, number 3). TSE3-/- mice demonstrated impaired thymocyte development. Further analysis revealed that TSE3 is associated with TCR signaling components including PLC-g1 and Grb2. We also showed that TSE3 deficiency impaired the assembly of TCR signalosome essential for TCR signaling suggesting the involvement of TSE3 in TCR signaling. This proposal will continue our study on the role of TSE3 in TCR signal transduction, detailed mapping of the protein-protein interaction domains in PLCg1 and Grb2. We will also put efforts on the identification of TSE3-binding proteins and the phosphorylation sites of TSE3 by using Tandem affinity purification and Mass spectrometry analysis. The completion of this project might provide us new insights into the current model of TCR signaling and thymocyte development and help the diagnosis and treatment of related immunodeficiency diseases.

T淋巴细胞的发育分化受到分子水平上的精细调控，相关研究一直是免疫学研究的重点和热点。本课题组在前期研究中发现了一个调控T细胞发育的新基因TSE3（Thymocytes- Specific Expression， number 3），小鼠中该基因的缺失导致了T细胞发育受损。进一步研究表明，TSE3能与pLCg1和Grb2相互作用，且TSE3缺失导致TCR信号复合物形成减弱，预示TSE3参与TCR信号传导。本课题将进一步分析TSE3缺失对TCR信号传导的影响；揭示TSE3与pLCg1和Grb2相互作用的分子机制；同时探讨与TSE3相互作用的其它蛋白及TSE3在TCR活化过程中的磷酸化修饰，以及这些相互作用与修饰在TCR信号传导中的作用。上述研究可望为现有的TCR信号传导和T 细胞分化发育机制假说提供补充，从而为阐明临床上相关T 淋巴细胞功能缺陷性疾病的发病机制及其治疗提供理论依据。

T细胞受体（T cell receptor, TCR）信号在胸腺T细胞发育和外周T细胞活化过程中均发挥关键作用。TCR刺激能诱导细胞膜附近LAT信号复合体形成，招募并活化一系列信号分子，传导信号。我们研究团队近期的研究发现，一个新的信号传导接头蛋白Tespa1，能在TCR活化后被招募到LAT信号复合体中，参与调控下游MAPKs信号通路以及Ca2+信号通路的活化。然而，Tespa1调控下游信号的具体分子机制尚不清楚。本项目的研究发现，Tespa1通过F187和F188位点直接与IP3R1结合，并将IP3R1招募到TCR信号复合体。这一招募不仅促进胞膜附近Fyn激酶对IP3R1的Tyr353的磷酸化，还有效促进了TCR信号复合体附近钙离子信号的最大活化。当我们将Tespa1与IP3R1的结合位点突变之后，TCR活化诱导的胞内钙离子信号活化受到了显著抑制。最后，携带这一突变的Tespa1-FFAA转基因小鼠完全模拟了Tespa1敲除小鼠的表型，提示Tespa1与IP3R1的相互作用在胸腺细胞的阳性选择过程中发挥了主要作用。综上所述，我们的工作揭示了Tespa1调控TCR信号传导和胸腺细胞发育全新的分子机制。