Gasque P, Chan P, Fontaine M, Ischenko A, Lamacz M, Götze O, Morgan B P
Department of Medical Biochemistry, UWCM, Cardiff, United Kingdom.
J Immunol. 1995 Nov 15;155(10):4882-9.
The C fragment C5a exerts its important physiologic and pathologic effects through interaction with a specific C5a receptor (C5aR) which is highly expressed on polymorphonuclear leukocytes and some other leukocytes. The presence of this receptor on epithelia and endothelia has recently been documented, raising the possibility that these other cells might also respond to locally generated C5a. C has been implicated in several brain disorders, notably demyelination and neurodegeneration, and cells within brain can synthesize a complete C system. It is thus of interest to examine the mechanisms by which C damages or activates brain cells. To this end we have examined the expression on human fetal astrocytes and astrocyte-derived cell lines of receptors for C fragments. We here report that human astrocytes and cell lines express a receptor for C5a (48 to 72 x 10(3) copies/cell), which is indistinguishable at the protein or mRNA level from that in leukocytes. The astrocyte C5aR was recognized by five different specific Abs, which revealed by Western blotting a protein of 40 to 45 kDa in primary human astrocytes and astrocyte cell lines. Expression was confirmed by RT-PCR using multiple primers. Neither inflammatory cytokines nor PMA caused up-regulation of the receptor on astrocytes. The receptor was functional in that addition of C5a (1 nM to 100 nM) or, at high doses (100 nM), C5adesArg, triggered a calcium transient in astrocytes. We propose that C5aR expression on astrocytes plays an important role in control of inflammation in brain and may be a central component of C-mediated brain injury.
补体片段C5a通过与一种特异性C5a受体（C5aR）相互作用发挥其重要的生理和病理作用，该受体在多形核白细胞和其他一些白细胞上高度表达。最近有文献记载上皮细胞和内皮细胞上存在这种受体，这增加了这些其他细胞也可能对局部产生的C5a作出反应的可能性。补体已被认为与几种脑部疾病有关，特别是脱髓鞘和神经退行性变，并且脑内的细胞可以合成完整的补体系统。因此，研究补体损伤或激活脑细胞的机制是很有意义的。为此，我们研究了人胎儿星形胶质细胞和星形胶质细胞衍生细胞系上补体片段受体的表达。我们在此报告，人星形胶质细胞和细胞系表达一种C5a受体（48至72×10³个拷贝/细胞），其在蛋白质或mRNA水平上与白细胞中的受体没有区别。星形胶质细胞C5aR被五种不同的特异性抗体识别，通过蛋白质印迹法在原代人星形胶质细胞和星形胶质细胞系中显示出一种40至45 kDa的蛋白质。使用多种引物通过RT-PCR证实了表达。炎性细胞因子和佛波酯均未导致星形胶质细胞上受体的上调。该受体具有功能，因为添加C5a（1 nM至100 nM）或高剂量（100 nM）的C5adesArg会在星形胶质细胞中引发钙瞬变。我们提出星形胶质细胞上C5aR的表达在控制脑内炎症中起重要作用，并且可能是补体介导的脑损伤的核心组成部分。
