The role of protein synthesis and degradation in the post-transcriptional regulation of rat multidrug resistance-associated protein 2 (Mrp2, Abcc2)
The role of protein synthesis and degradation in the post-transcriptional regulation of rat multidrug resistance-associated protein 2 (Mrp2, Abcc2)
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DOI：
10.1124/mol.105.013144
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发表时间：
2005-09-01
影响因子：
3.6
通讯作者：
Vore, M
中科院分区：
文献类型：
--
作者：
Jones, BR;Li, W;Vore, M
多药耐药相关蛋白2(MRP2，Abcc2)是一种存在于肝细胞、肾上皮细胞和肠上皮细胞顶膜上的有机阴离子转运蛋白，被认为经历了转录后调节。我们假设，与不同的mrp2蛋白表达相一致，mrp2蛋白经历了蛋白质合成或降解的改变速率。我们用[S-35]半胱氨酸/蛋氨酸或[C-14]碳酸氢钠进行体内代谢标记研究、多聚体分布分析和核糖核酸酶保护分析，分析了对照组、怀孕19天和20天以及孕烯醇酮-16α-碳腈(PCN)处理的大鼠MRP2的合成、表达和降解。与对照组相比，PCN治疗2d组大鼠的mrp2蛋白表达显著增加，而妊娠19d组大鼠的mrp2蛋白表达明显降低，各组间的mrp2基因表达差异无统计学意义。C-14标记的MRP2在对照组、妊娠期和PCN处理组的半衰期分别为27、36和22h，差异无统计学意义。PCN处理组大鼠MRP2中S-35的掺入率最高。PCN治疗后MRP2mRNA的多体分布分析与MRP2蛋白合成增加相一致。RPA测定大鼠肝脏的主要转录起始点为-98个核苷酸，其他起始点分别为-213、-163、-132和-71个核苷酸；不同组间转录起始点的使用没有差异。在对照、妊娠和PCN处理的大鼠中，mrp2蛋白降解的差异不能解释mrp2的转录后调控。相反，观察到的蛋白质合成的差异表明，大鼠mrp2蛋白的翻译调控具有内在作用。
Multidrug resistance-associated protein 2 (Mrp2, Abcc2), an organic anion transporter present in the apical membrane of hepatocytes, renal epithelial cells, and enterocytes, is postulated to undergo post-transcriptional regulation. We hypothesized that Mrp2 protein undergoes altered rates of protein synthesis or degradation consistent with different Mrp2 protein expression. We analyzed Mrp2 synthesis, expression, and degradation in control female, 19- and 20-day pregnant, and pregnenolone-16 alpha-carbonitrile (PCN)-treated rats using in vivo metabolic-labeling studies with [S-35] cysteine/methionine or [C-14]NaHCO3, polysomal distribution analyses and ribonuclease protection assays (RPA). Mrp2 protein was significantly increased in rats treated with PCN for 2 days but significantly decreased in 19-day pregnant rats relative to controls; no significant differences were observed in Mrp2 mRNA expression among these groups. The measured half-lives of C-14-labeled Mrp2 in control, pregnant, and PCN-treated rats were 27, 36, and 22 h, respectively, and were not significantly different. The rate of incorporation of S-35 into Mrp2 was highest in PCN-treated rats. Polysomal distribution analysis of Mrp2 mRNA was consistent with increased Mrp2 protein synthesis after PCN treatment. The major transcription-initiation site for rat liver determined by RPA was -98 nucleotides (nt), with other start sites observed at -213, -163, -132, and -71 nt; use of transcription sites did not differ among the groups. Differences in the degradation of Mrp2 protein cannot explain the post-transcriptional regulation of Mrp2 in control, pregnant, and PCN-treated rats. Rather, the observed difference in protein synthesis suggests an intrinsic role for the translational regulation of rat Mrp2 protein.