Inhibitory effects of prostaglandin A1 on membrane transport of folates mediated by both the reduced folate carrier and ATP-driven exporters
Inhibitory effects of prostaglandin A1 on membrane transport of folates mediated by both the reduced folate carrier and ATP-driven exporters
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DOI：
10.1016/s0006-2952(99)00227-0
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发表时间：
1999-10-15
影响因子：
5.8
通讯作者：
Goldman, ID
中科院分区：
文献类型：
--
作者：
Assaraf, YG;Sierra, EE;Goldman, ID
有研究报告描述了前列腺素A（1）（PGA（1））对控制叶酸穿过中国仓鼠卵巢（CHO）细胞质膜转运的过程的多方面抑制作用：还原型叶酸载体、RFC 1和ATP依赖性输出者。PGA（1）是RFC 1介导的MTX内流的非竞争性抑制剂，Ki值约为21 μ M。抑制作用几乎是瞬时的，不可逆的，似乎需要将PGA（1）掺入脂质膜中;仅表面吸附不足以抑制RFC 1转运活性。相反，PGA（1）对叶酸转运的影响很小（类似于对总流入的20%抑制），这与CHO细胞中叶酸转运的主要部分由不同于RFC 1的低pH机制介导的观察结果一致。PGA（1）也是一种有效的抑制剂ATP驱动的MTX和叶酸的外排。在浓度为7 μ M PGA（1）时，这些叶酸的外排速率常数分别降低了约70%和约50%。PGA（1）对叶酸双向通量的净效应转化为净转运的显著改变。与未处理的CHO细胞相比，向处于稳态的细胞中加入7 μ M PGA（1）和1 μ M MTX，产生了净摄取的快速开始，并实现了稳态游离MTX水平的相似至3倍的增加。向稳态细胞中加入7 μ M PGA（1）和1 μ M叶酸，使游离叶酸水平增加约5倍。这些研究证实PGA（1）是还原型叶酸载体和ATP驱动的叶酸输出蛋白的有效抑制剂。在阴离子化合物中，RFC 1抑制的非竞争性性质是独特的，阴离子化合物通常是载体的竞争性抑制剂。(C)1999 ELsevier Science Inc.
Studies are reported that describe the multifaceted inhibitory effects of prostaglandin A(1)(PGA(1)) on processes that govern the transport of folates across the plasma membrane of Chinese hamster ovary (CHO) cells: the reduced folate carrier, RFC1, and ATP-dependent exporters. PGA(1) was a noncompetitive inhibitor of MTX influx mediated by RFC1 with a K-i of similar to 21 mu M. The onset of inhibition was virtually instantaneous, not reversible, and appeared to require the incorporation of PGA(1) into the lipid membrane; surface adsorption alone was insufficient for inhibition of RFC1 transport activity. In contrast, the effect of PGA(1) on folic acid transport was small (similar to 20% inhibition of total influx), consistent with the observation that the major portion of folic acid transport in CHO cells is mediated by a low pH mechanism distinct from RFC1. PGA(1) was also a potent inhibitor of the ATP-driven efflux of both MTX and folic acid. At a concentration of 7 mu M PGA(1) the efflux rate constants for these folates were depressed by similar to 70 and similar to 50%, respectively. The net effects of PGA(1) on the bidirectional folate fluxes translated into marked alterations in net transport. The addition of 7 mu M PGA(1) to cells at steady state with 1 mu M MTX produced a rapid onset of net uptake and the achievement of an similar to 3-fold increase in the steady state free MTX level as compared with untreated CHO cells. The addition of 7 mu M PGA(1) to cells at steady state with 1 mu M folic acid produced an similar to 5-fold increase in the free folate level. These studies establish PGA(1) as a potent inhibitor of both the reduced folate carrier and ATP-driven folate exporter(s). The noncompetitive nature of the inhibition of RFC1 is unique among anionic compounds, which are usually competitive inhibitors of the carrier. (C) 1999 ELsevier Science Inc.