Gimferrer Idoia, Ibáñez Anna, Farnós Montse, Sarrias Maria-Rosa, Fenutría Rafael, Roselló Sandra, Zimmermann Pascale, David Guido, Vives Jordi, Serra-Pagès Carles, Lozano Francisco
Servei d'Immunologia, Hospital Clínic Universitari, Institut di Investigacions Biomèdiques August Pi i Sunyer, Facultat de Medicina, Universitat de Barcelona, Barcelona, Spain.
J Immunol. 2005 Aug 1;175(3):1406-14. doi: 10.4049/jimmunol.175.3.1406.
CD6 is a type I membrane glycoprotein expressed on thymocytes, mature T and B1a lymphocytes, and CNS cells. CD6 binds to activated leukocyte cell adhesion molecule (CD166), and is considered as a costimulatory molecule involved in lymphocyte activation and thymocyte development. Accordingly, CD6 partially associates with the TCR/CD3 complex and colocalizes with it at the center of the mature immunological synapse (IS) on T lymphocytes. However, the signaling pathway used by CD6 is still mostly unknown. The yeast two-hybrid system has allowed us the identification of syntenin-1 as an interacting protein with the cytoplasmic tail of CD6. Syntenin-1 is a PDZ (postsynaptic density protein-95, postsynaptic discs large, and zona occludens-1) domain-containing protein, which functions as an adaptor protein able to bind cytoskeletal proteins and signal transduction effectors. Mutational analyses showed that certain amino acids of the most C-terminal sequence of CD6 (-YDDISAA) and the two postsynaptic density protein-95, postsynaptic discs large, and zona occludens-1 domains of syntenin-1 are relevant to the interaction. Further confirmation of the CD6-syntenin-1 interaction was obtained from pull-down and co-immunoprecipitation assays in mammalian cells. Image analyses also showed that syntenin-1 accumulates at CD6 caps and at the IS. Therefore, we propose that syntenin-1 may function as a scaffolding protein coupling CD6 and most likely other lymphocyte receptors to cytoskeleton and/or signaling effectors during IS maturation.
CD6是一种I型膜糖蛋白，表达于胸腺细胞、成熟的T和B1a淋巴细胞以及中枢神经系统细胞上。CD6与活化白细胞细胞黏附分子（CD166）结合，被认为是一种参与淋巴细胞活化和胸腺细胞发育的共刺激分子。因此，CD6部分地与TCR/CD3复合物相关联，并在T淋巴细胞成熟免疫突触（IS）的中心与其共定位。然而，CD6所使用的信号通路大多仍不清楚。酵母双杂交系统使我们能够鉴定出syntenin-1是与CD6胞质尾相互作用的蛋白。Syntenin-1是一种含PDZ（突触后致密蛋白-95、突触后大圆盘蛋白和紧密连接蛋白-1）结构域的蛋白，其作为一种衔接蛋白，能够结合细胞骨架蛋白和信号转导效应器。突变分析表明，CD6最C末端序列（-YDDISAA）的某些氨基酸以及syntenin-1的两个突触后致密蛋白-95、突触后大圆盘蛋白和紧密连接蛋白-1结构域与这种相互作用相关。通过哺乳动物细胞中的下拉和共免疫沉淀实验进一步证实了CD6与syntenin-1的相互作用。图像分析还表明，syntenin-1在CD6帽和IS处聚集。因此，我们提出syntenin-1可能作为一种支架蛋白，在IS成熟过程中将CD6以及很可能其他淋巴细胞受体与细胞骨架和/或信号效应器偶联起来。
