Mechanism of retinoic acid induced attenuation of PTH action in UMR 106-01 cells.
Mechanism of retinoic acid induced attenuation of PTH action in UMR 106-01 cells.
复制标题
视黄酸诱导 UMR 106-01 细胞 PTH 作用减弱的机制。
DOI：
10.1007/s00223-001-1083-1
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发表时间：
2002
期刊：
影响因子：
--
通讯作者：
Martin,KJ
中科院分区：
文献类型：
--
作者：
Gonzalez,EA;McConkey,CL;Martin,KJ
我们实验室在成骨细胞样细胞中的研究表明，PTH引起EGF受体表达的增加是环AMP介导的，并可被维甲酸（RA）阻断。本研究探讨了RA对PTH作用的机制。将UMR 106-01细胞暴露于RA，并测试cAMP对PTH的反应以及125 I PTH结合。RA使PTH引起的cAMP生成显著降低（为对照组的25.1 ± 1.6%），而PTH结合仅轻微降低。对于腺苷酸环化酶活性的研究，从暴露于RA的完整细胞中分离膜。RA治疗降低了PTH刺激的腺苷酸环化酶活性;然而，毛喉素刺激的酶活性没有变化。用百日咳毒素处理完整的细胞，以抑制G1，没有改变RA对PTH刺激的腺苷酸环化酶活性的抑制作用。添加GppNHp（GTP的不可水解类似物）完全恢复了膜中对PTH的反应。因此，我们检测了IMP脱氢酶（GTP生物合成的限速酶）和GMP还原酶（抵消合成酶的作用）的活性。用RA处理48小时使GMP还原酶活性增加240.9 ± 24.2%，使IMP脱氢酶活性降低至对照值的67.5 ± 8.8%。这些数据表明，RA损害了完整细胞对PTH的反应。这种钝化的反应在膜制备物中得以保留，但被GTP纠正。RA诱导的GTP生物合成途径中涉及的酶的改变有利于减少GTP生物合成的方向提供了一个解释RA对PTH作用的抑制作用。
Studies from our laboratory in osteoblast-like cells have shown that the increase in EGF receptor expression in response to PTH was cyclic AMP mediated and was blocked by treatment with retinoic acid (RA). The present studies investigate the mechanism for this effect of RA on PTH actions. UMR 106-01 cells were exposed to RA and were tested for cAMP response to PTH as well as for 125I PTH binding. cAMP production in response to PTH was markedly decreased by RA (25.1 ± 1.6% of control) whereas there was only a slight decrease in PTH binding in response to RA. For the study of adenylate cyclase activity, membranes were isolated from intact cells that had been exposed to RA. Treatment with RA decreased PTH-stimulated adenylate cyclase activity; however, forskolin-stimulated enzyme activity was unchanged. Treatment of intact cells with pertussis toxin, to inactivate Gi, did not alter the inhibitory effect of RA on PTH-stimulated adenylate cyclase activity. Addition of GppNHp, a non-hydrolyzable analogue of GTP, completely restored the response to PTH in the membranes. Therefore, we examined the activity of IMP dehydrogenase, the rate-limiting enzyme for GTP biosynthesis, and GMP reductase which counteracts the effect of the synthetic enzyme. Treatment with RA for 48 hours increased GMP reductase activity by 240.9 ± 24.2% and decreased IMP dehydrogenase activity to 67.5 ± 8.8% of control values. These data indicate that RA impairs the response to PTH in intact cells. This blunted response was preserved in membrane preparations but was corrected by GTP. The RA-induced alterations of enzymes involved in the GTP biosynthetic pathway in a direction that favors a decrease in GTP biosynthesis provide an explanation for the inhibitory effect of RA on PTH actions.