Wu Z, Ji H, Hassan A, Aguilera G, Sandberg K
Center for the Study of Sex Differences, Georgetown University, Washington, DC 20057, USA.
J Neuroendocrinol. 2004 Mar;16(3):214-20. doi: 10.1111/j.0953-8194.2004.01153.x.
Long-term adrenalectomy (ADX) is associated with marked down-regulation of pituitary corticotropin releasing factor type-1 receptors (CRF-R1) but normal CRF-R1 mRNA levels, suggesting that regulation of receptor levels occurs at post-transcriptional sites. We have reported that adrenal cytosolic proteins, which bind to cis elements in the 5' leader sequence (5'LS) of the rat angiotensin II type 1a receptor (AT(1a)R) mRNA, participate in the regulation of AT(1a)R density by inhibiting AT(1a)R mRNA translation. In this study, we examined anterior pituitary cytosolic proteins that form RNA protein complexes (RPC) with the 5'LS of the CRF-R1 and the AT(1a)R. Competition studies and ultraviolet-crosslinking analysis suggest that formation of CRF-R1 and AT(1a)R 5'LS RPC require at least some proteins that are common to both receptor mRNAs. Pituitaries isolated from male Sprague-Dawley rats six days after ADX showed significant (P < 0.05) increases of 2.9-fold in CRF-R1 5'LS RNA binding protein (BP) activity compared to pituitaries from sham-operated rats; this effect of ADX was prevented by glucocorticoid replacement. By contrast, no differences in the number of pituitary AT(1a)R binding sites or pituitary AT(1a)R 5'LS BP activity were observed between sham and ADX rats, indicating that the effect of ADX on RPC formation was specific for CRF-R1 mRNA. Addition of pituitary cytosolic extracts inhibited in vitro translation of CRF-R1 mRNA by 79% under conditions that had no significant effects on the translation of a control mRNA. The data suggest that CRF-R1 translation is regulated by modulation of the HPA axis through pituitary cytosolic proteins binding to the CRF-R1 5'LS.
长期肾上腺切除术（ADX）与垂体促肾上腺皮质激素释放因子1型受体（CRF-R1）的显著下调有关，但CRF-R1 mRNA水平正常，这表明受体水平的调节发生在转录后位点。我们曾报道，与大鼠血管紧张素II 1a型受体（AT(1a)R）mRNA的5'前导序列（5'LS）中的顺式元件结合的肾上腺胞质蛋白，通过抑制AT(1a)R mRNA翻译参与AT(1a)R密度的调节。在本研究中，我们检测了与CRF-R1和AT(1a)R的5'LS形成RNA蛋白复合物（RPC）的垂体前叶胞质蛋白。竞争研究和紫外线交联分析表明，CRF-R1和AT(1a)R 5'LS RPC的形成至少需要一些两种受体mRNA共有的蛋白质。与假手术大鼠的垂体相比，ADX术后6天从雄性Sprague-Dawley大鼠分离的垂体中，CRF-R1 5'LS RNA结合蛋白（BP）活性显著（P < 0.05）增加2.9倍；糖皮质激素替代可预防ADX的这种作用。相比之下，假手术和ADX大鼠之间垂体AT(1a)R结合位点数量或垂体AT(1a)R 5'LS BP活性没有差异，表明ADX对RPC形成的影响对CRF-R1 mRNA具有特异性。在对对照mRNA翻译无显著影响的条件下，添加垂体胞质提取物可使CRF-R1 mRNA的体外翻译抑制79%。数据表明，CRF-R1的翻译通过垂体胞质蛋白与CRF-R1 5'LS结合对HPA轴的调节来调控。
