Fikri Youssef, Nyabenda Jean, Content Jean, Huygen Kris
ISP-Institut Pasteur de Bruxelles, Rue Engeland 642, 1180 Bruxelles, Belgium.
Immunogenetics. 2007 Aug;59(8):653-9. doi: 10.1007/s00251-007-0226-6. Epub 2007 May 26.
NKG2D is an activating lectin-like receptor that initiates natural killer (NK) cell responses against transformed tumor cells expressing its ligands, i.e., molecules related to major histocompatibility complex (MHC) class I molecules. NKG2D lacks signaling elements in its cytoplasmic domain and can deliver stimulatory signals only in association with transmembrane adaptor proteins DAP10 or DAP12. The complementary DNAs (cDNAs) encoding the bovine homologues of NKG2D and the adaptor proteins DAP10 and DAP12 were cloned by reverse transcriptase-polymerase chain reaction (RT-PCR) from resting bovine peripheral blood mononuclear cells (PBMC) and sequenced. Comparison with human, pig, and mouse sequences showed that bovine NKG2D is most similar to pig NKG2D and short mouse NKG2D (NKG2D-S). Similar to its human, mouse, and pig homologues, the cDNA for bovine DAP10 codes for a phosphatidyl-inositol-3 (PI-3) kinase-binding site (YxxM) in its cytoplasmic region. Finally, similar to its human, mouse, and pig homologues, the cDNA encoding bovine DAP12 demonstrates one tyrosine-based activated motif (ITAM) in its cytoplasmic domain. Bovine NKG2D cell surface expression was analyzed by flow cytometry on HEK 293 cells transiently transfected with cDNA expression vectors encoding COOH-terminal polyhistidine-tagged NKG2D and NH(2)-terminal Flag-tagged DAP10 and DAP12. Confirming previous findings for short mouse NKG2D-S, bovine NKG2D immunoreceptor could associate with either DAP10 or DAP12 adaptor protein for its cell surface expression.
NKG2D是一种激活型凝集素样受体，可启动自然杀伤（NK）细胞对表达其配体（即与主要组织相容性复合体（MHC）I类分子相关的分子）的转化肿瘤细胞的反应。NKG2D在其细胞质结构域中缺乏信号元件，仅与跨膜衔接蛋白DAP10或DAP12结合时才能传递刺激信号。通过逆转录聚合酶链反应（RT-PCR）从静息的牛外周血单个核细胞（PBMC）中克隆出编码牛NKG2D及其衔接蛋白DAP10和DAP12同源物的互补DNA（cDNA）并进行测序。与人类、猪和小鼠序列比较表明，牛NKG2D与猪NKG2D和短型小鼠NKG2D（NKG2D-S）最为相似。与其人类、小鼠和猪同源物相似，牛DAP10的cDNA在其细胞质区域编码一个磷脂酰肌醇-3（PI-3）激酶结合位点（YxxM）。最后，与其人类、小鼠和猪同源物相似，编码牛DAP12的cDNA在其细胞质结构域中显示出一个基于酪氨酸的激活基序（ITAM）。通过流式细胞术分析了牛NKG2D在瞬时转染了编码COOH末端多组氨酸标记的NKG2D以及NH(2)-末端Flag标记的DAP10和DAP12的cDNA表达载体的HEK 293细胞上的细胞表面表达。证实了先前关于短型小鼠NKG2D-S的研究结果，牛NKG2D免疫受体可与其细胞表面表达的DAP10或DAP12衔接蛋白结合。
