AGONIST-INDUCED DOWN-REGULATION OF PLATELET-ACTIVATING-FACTOR RECEPTOR GENE-EXPRESSION IN U937 CELLS

被引:15
作者
CHAU, LY [1 ]
PECK, K [1 ]
YEN, HH [1 ]
WANG, JY [1 ]
机构
[1] ACAD SINICA,INST BIOMED SCI,DIV CANC RES,TAIPEI,TAIWAN
关键词
D O I
10.1042/bj3010911
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
Prolonged exposure (8-24 h) of human promonocytic U937 cells to 100 nM 1-O-hexadecyl-2-N-methylcarbamyl-sn-glycero-3- phosphocholine (carbarmyl-PAF), a non-metabolizable analogue of platelet-activating factor (PAF), reduced the numbers of PAF receptors by 50-75%, as determined by the radioligand-binding assay. To clarify whether the down-regulation of receptor numbers is due to decreased expression level of the PAF-receptor gene, the effect of carbamyl-PAF on the steady-state level of PAF-receptor mRNA was examined by a highly sensitive reverse-transcriptase PCR method. A 50% decline in the level of PAF-receptor mRNA was observed in U937 cells pretreated with 100 nM carbamyl-PAF for 24 h. The effect of carbamyl-PAF was dose-dependent, with an EC(50) value around 10 nM. A PAF-receptor antagonist, SRI-63675, was able to attenuate the effect of carbamyl-PAF. Furthermore lysoPAF, at 1 mu M, was unable to induce a significant decrease in PAF-receptor mRNA after incubation for 24 h, indicating that the effect of carbamyl-PAF was specific. The half-life of the PAF-receptor mRNA measured in the presence of actinomycin D was unaffected by carbamyl-PAF treatment. In contrast, nuclear run-off experiments demonstrated that the transcription rate of the PAF-receptor gene in carbamyl-PAF-treated cells was about 65% of that in control cells. These results suggest that the PAF receptor in U937 cells is subject to down-regulation by agonist, at least partly, at the transcriptional level.
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收藏
页码:911 / 916
页数:6
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