Bellón Teresa, Kitzig Friederike, Sayós Joan, López-Botet Miguel
Hospital de la Princesa, Madrid, Spain.
J Immunol. 2002 Apr 1;168(7):3351-9. doi: 10.4049/jimmunol.168.7.3351.
The inhibitory receptor Ig-like transcript (ILT)2 (leukocyte Ig-like receptor or CD85j) is a type I transmembrane protein expressed by different leukocyte lineages. The extracellular region of ILT2 binds HLA class I molecules, and its cytoplasmic domain displays four immunoreceptor tyrosine-based inhibition motifs. Upon tyrosine phosphorylation ILT2 recruits the Src homology 2 domain-containing protein tyrosine phosphatase 1 (SHP-1) that is involved in negative signaling. To address the structural basis of ILT2-mediated inhibitory signaling, deletion and single tyrosine mutants were generated and transfected in the COS-7 and rat basophilic leukemia cell lines; their abilities to bind SHP-1 and to inhibit FcepsilonR-induced serotonin release in rat basophilic leukemia cells were studied. Both biochemical and functional analyses revealed tyrosines 644 (SIYATL) and 614 (VTYAQL) as the SHP-1 docking sites required for ILT2 inhibitory function. Substitution of tyrosine 562 (VTYAEV) did not alter receptor function. By contrast, mutation of tyrosine 533 (NLYAAV) interfered with ILT2 tyrosine phosphorylation and the subsequent SHP-1 recruitment, thus supporting a regulatory role for this motif.
抑制性受体免疫球蛋白样转录物（ILT）2（白细胞免疫球蛋白样受体或CD85j）是一种由不同白细胞谱系表达的I型跨膜蛋白。ILT2的细胞外区域与I类HLA分子结合，其胞质结构域具有四个基于免疫受体酪氨酸的抑制基序。酪氨酸磷酸化后，ILT2招募参与负向信号传导的含Src同源2结构域的蛋白酪氨酸磷酸酶1（SHP-1）。为了阐明ILT2介导的抑制性信号传导结构基础，构建了缺失突变体和单个酪氨酸突变体，并转染至COS-7细胞系和大鼠嗜碱性粒细胞白血病细胞系；研究了它们结合SHP-1以及抑制大鼠嗜碱性粒细胞白血病细胞中FcepsilonR诱导的5-羟色胺释放的能力。生化和功能分析均显示，酪氨酸644（SIYATL）和614（VTYAQL）是ILT2抑制功能所需的SHP-1对接位点。酪氨酸562（VTYAEV）的替换未改变受体功能。相比之下，酪氨酸533（NLYAAV）的突变干扰了ILT2的酪氨酸磷酸化及随后的SHP-招募，从而证实了该基序的调节作用。
