Rubin J, Biskobing D, Titus L, Thornton D L, Catherwood B D, Nanes M S
Department of Medicine, Veterans Affairs Medical Center, Atlanta, Georgia, USA.
Am J Med Sci. 1996 Feb;311(2):73-9. doi: 10.1097/00000441-199602000-00003.
Complement 5a receptor (C5aR) mediates both acute and chronic participation of monocytes in the immune response. In the human U937 monoblast, C5aR is maximally expressed 4 days after treatment with 1,25(OH)2D3 (or cycloheximide) and prostaglandin E2 combined. The authors asked whether these agents altered expression of C5aR messenger RNA (mRNA). Unstimulated U937 cells expressed neither C5aR mRNA nor C5a binding. Complement 5aR mRNA rose 3 hours after prostaglandin E2 application and fell to basal levels by 12 hours. This early rise in C5aR mRNA did not cause an acute rise in C5a binding, which gradually increased between 1 and 4 days. Neither 1,25(OH)2D3 nor cycloheximide induced expression of C5aR mRNA in the absence of prostaglandin E2 but did enhance prostaglandin E2-stimulated C5aR mRNA expression and C5a binding. The authors observed a late increase in C5aR mRNA at day 3 in treated cells. Inhibition of this late rise in mRNA with 5,6-dichlorobenzimidazole riboside attenuated C5a binding by 65%, indicating its importance in the generation of C5a binding sites. The expression of functional C5aR is, therefore, a complex process involving regulation at transcriptional and posttranscriptional levels.
补体5a受体（C5aR）介导单核细胞在免疫反应中的急性和慢性参与。在人U937单核细胞中，用1,25(OH)2D3（或环己酰亚胺）和前列腺素E2联合处理4天后，C5aR表达达到最大值。作者询问这些试剂是否改变了C5aR信使核糖核酸（mRNA）的表达。未受刺激的U937细胞既不表达C5aR mRNA，也不结合C5a。应用前列腺素E2后3小时，C5aR mRNA升高，到12小时降至基础水平。C5aR mRNA的这种早期升高并未导致C5a结合的急性升高，C5a结合在1至4天之间逐渐增加。在没有前列腺素E2的情况下，1,25(OH)2D3和环己酰亚胺均未诱导C5aR mRNA的表达，但确实增强了前列腺素E2刺激的C5aR mRNA表达和C5a结合。作者观察到处理后的细胞在第3天C5aR mRNA出现后期增加。用5,6-二氯苯并咪唑核糖核苷抑制mRNA的这种后期升高可使C5a结合减少65%，表明其在C5a结合位点产生中的重要性。因此，功能性C5aR的表达是一个复杂的过程，涉及转录和转录后水平的调控。
