Angiotensin Receptor Regulation By Upstream Short Open Reading Frames

 说明(申请人提供)：血管紧张素II(Ang II)在维持体液平衡和血压(BP)方面起着关键作用。我们最近发现，在血管紧张素1a型受体(AT1aR)的5‘前导序列第二外显子中编码的七个氨基酸多肽(PEP7)可以抑制细胞外信号调节蛋白激酶1和2(ERK1/2)的Ang II激活，并调节AT1aR在细胞内的转运。PEP7还显著减少Ang II介导的钠摄入量，而对Ang II介导的饮水没有任何影响，并拮抗Ang II引起的血压升高。认识到随着年龄的增长，口渴、尿液集中能力以及排出水和电解质的能力会发生显著变化，我们确定了年龄是否会改变AT1aR的两个剪接变体[一个编码PEP7(E-1，2，3-AT1aR)和另一个不编码(E-1，3-AT1aR)]的剪接变体的表达比率，并确实发现，年轻动物比老年动物表达更高的E-1，2，3-AT1aR/E-1，3-AT1aR的比率。我们还观察到衰老对肾上腺AT1R结合密度的影响。因此，PEP7表达的变化(由于E-1，2，3-和E-1，3-AT1aR表达的变化，在年轻动物中存在比老年动物更高的水平)可能导致AT1R调节受损，以响应环境电解质平衡的变化。本申请中提出的研究(对我们资助的拨款HL121456的补充)解决了这样的假设，即AT1aR剪接变体的表达比率随着年龄的变化而变化，有利于E-1，3-AT1aR，导致PEP7的产生减少，并导致与年龄相关的液体和电解质动态平衡和血压损害。我们将确定在老年动物中补充PEP7是否使它们的液体稳态恢复正常，以及年轻动物中PEP7产量的减少是否会导致老年表型的沉淀。肾素-血管紧张素系统功能障碍与多种与衰老相关的病理机制有关。因此，这些研究可能导致新的治疗方法来治疗与年龄相关的液体稳态和心血管功能改变。

 DESCRIPTION (provided by applicant):Angiotensin II (Ang II) plays a key role in fluid homeostasis and blood pressure (BP). We recently found that a seven amino acid peptide (PEP7) encoded within a short open reading frame in exon 2 of the 5' leader sequence of the angiotensin type 1a receptor (AT1aR) mRNA inhibits Ang II activation of extracellular signal-regulated protein kinases 1 and 2 (Erk1/2) and regulates AT1aR trafficking in cells. PEP7 also markedly reduced Ang II-mediated sodium intake without having any effect on Ang II-mediated water drinking and it antagonized Ang II-induced increases in BP. Recognizing that with aging come significant changes in thirst, urinary concentrating ability and the ability to excrete water and electrolytes, we determined if aging alters the ratio of expression of the two splice variants of the AT1aR [one that encodes PEP7 (E-1,2,3-AT1aR) and the other that does not (E-1,3-AT1aR)] and found, indeed, that young animals express a higher ratio of E-1,2,3-AT1aR/E-1,3-AT1aR than aged animals. We also observed that aging affects the density of AT1R binding in adrenal gland. Thus changes in the expression of PEP7 (present in higher levels in young compared to older animals because of changes changes in E-1,2,3- and E-1,3-AT1aR expression) may lead to impaired AT1R regulation in response to environmental changes in electrolyte balance. Studies proposed in this application (supplement to our funded grant HL121456) address the hypothesis that the ratio of the expression of the splice variants of the AT1aR changes with aging, favoring the E-1,3-AT1aR, resulting in less PEP7 production, and contributing to age-associated impairments in fluid and electrolyte homeostasis and blood pressure. We will determine if supplementation with PEP7 in aged animals returns their fluid homeostasis to normal and if reduction in PEP7 production in young animals precipitates the aged phenotype. Renin-angiotensin system dysfunction is associated with diverse pathologies associated with aging. Therefore, these studies may lead to novel therapeutic approaches for the treatment of age-related alterations in fluid homeostasis and cardiovascular function.