Sluyter Ronald, Wiley James S
Department of Medicine, University of Sydney, Level 5 South Block, Nepean Hospital, Penrith, NSW 2750, Australia.
Int Immunol. 2002 Dec;14(12):1415-21. doi: 10.1093/intimm/dxf111.
Dendritic cells (DC) express a number of P2X receptors including the P2X7/P2Z receptor whose activation by extracellular adenosine 5'-triphosphate (ATP) induces the influx of calcium, DC maturation, cytokine release and apoptosis. In B lymphocytes ATP induces the rapid shedding of CD23 and CD62 ligand by activating a membrane metalloprotease. In this study, we examined the expression and early effects of P2X7 receptor activation on monocyte-derived DC, generated from individuals either wild-type or homozygous for a loss-of-function single nucleotide polymorphism at position 1513 of the P2X7 gene. Labeling with an anti-human P2X7 receptor mAb demonstrated that DC express the P2X7 receptor at a lower level than macrophages. Short-term incubations (5 min) of DC with ATP induced an influx of ethidium+ (314 Da) into wild-type DC, but not into DC homozygous for the loss-of-function polymorphism. In contrast to results with ethidium+, ATP did not induce the influx of the viability dye propidium2+ (415 Da) into DC in short-term incubations. Addition of ATP also induced a rapid loss of CD23 from the surface of wild-type DC (t(1/2 )< 120 s), and this loss was inhibited by oxidized ATP and KN-62 which are known P2X7 receptor antagonists. Moreover, ATP-induced shedding of CD23 was slower from DC homozygous for the loss-of-function polymorphism than from wild-type DC. The data show that monocyte-derived DC express the P2X7 receptor whose activation opens a cation-selective channel, and which leads to rapid and near complete shedding of CD23. Both of these functions of the P2X7 receptor are impaired on DC from subjects who are homozygous for the loss-of-function 1513 polymorphism.
树突状细胞（DC）表达多种P2X受体，包括P2X7/P2Z受体，细胞外三磷酸腺苷（ATP）对其激活可诱导钙离子内流、DC成熟、细胞因子释放及细胞凋亡。在B淋巴细胞中，ATP通过激活一种膜金属蛋白酶诱导CD23和CD62配体快速脱落。在本研究中，我们检测了P2X7受体激活对单核细胞来源的DC的表达及早期影响，这些DC由野生型个体或P2X7基因第1513位存在功能丧失性单核苷酸多态性的纯合子个体产生。用抗人P2X7受体单克隆抗体标记显示，DC表达P2X7受体的水平低于巨噬细胞。用ATP对DC进行短期孵育（5分钟）可诱导野生型DC摄入乙锭⁺（314 Da），但不能诱导功能丧失性多态性纯合子DC摄入。与乙锭⁺的结果相反，短期孵育时ATP未诱导活性染料碘化丙啶⁺（415 Da）进入DC。添加ATP还可诱导野生型DC表面的CD23快速丢失（半衰期<120秒），已知的P2X7受体拮抗剂氧化ATP和KN-62可抑制这种丢失。此外，功能丧失性多态性纯合子DC的ATP诱导的CD23脱落比野生型DC慢。数据表明，单核细胞来源的DC表达P2X7受体，其激活可打开一个阳离子选择性通道，并导致CD23快速且几乎完全脱落。P2X7受体的这两种功能在功能丧失性1513多态性纯合子受试者的DC上均受损。
