Cellular Regulation of Angiotensin Converting Enzyme 2

描述（由申请人提供）：几十年的研究已经确立了肾素-血管紧张素系统作为血压，稳态和细胞增殖的主要调节因子。肾素-血管紧张素系统作用由肽血管紧张素II（Ang II）（一种有效的血管收缩剂和促分裂剂）和血管紧张素-（1-7）[Ang-（1- 7）]（一种血管扩张剂和生长抑制剂）的相反作用介导。血管紧张素转换酶2（ACE 2）是近年来发现的一种ACE的同源物，它优先从血管紧张素II（Ang II）转化为血管紧张素（1-7）。ACE 2在高血压大鼠肾脏中的表达减少表明其对Ang II与Ang-（1-7）平衡的贡献。虽然ACE 2最初定位于外周器官，如心脏，肾脏和睾丸，我们确定ACE 2 mRNA和蛋白质在不同的脑区域从新生儿和成年SD大鼠以及培养的神经元和星形胶质细胞。此外，我们证明，培养的神经元和星形胶质细胞与血管紧张素II治疗引起ACE 2 mRNA和蛋白质显着减少。在令人兴奋的新结果中，我们发现ACE 2的抑制降低了心率的压力感受性反射控制，这表明ACE 2的调节和Ang II与Ang-（1-7）比率的改变在血压的中枢控制中至关重要。我们认为ACE 2是脑中Ang II/Ang-（1-7）浓度平衡的主要调节剂。在具体目标1中，我们将确定血管紧张素II是否调节表达改变肽浓度的转基因大鼠脑中ACE 2 mRNA和蛋白，以及这些大鼠或ACE 2活性抑制后压力感受性反射对心率的控制是否改变。具体目标2的研究将集中在从培养的星形胶质细胞分泌的ACE 2，以评估其底物特异性，并确定从培养的星形胶质细胞和神经元以及从完整的脑切片分泌ACE 2的分子机制。最后，在具体目标3中，我们将确定星形胶质细胞和神经元中ACE 2的转录调节因子。相关性：ACE 2优先将Ang II转化为Ang-（1-7），这是在血压的中枢控制中具有相反作用的肽。ACE 2的调节可能对维持脑中的肾素-血管紧张素系统的正常功能至关重要。

DESCRIPTION (provided by applicant): Decades of research have established the renin-angiotensin system as a major regulator of blood pressure, homeostasis, and cell proliferation. Renin-angiotensin system effects are mediated by the opposing actions of the peptides angiotensin II (Ang II), a potent vasoconstrictor and mitogen, and angiotensin-(1-7) [Ang-(1- 7)], a vasodilator and growth inhibitor. Angiotensin-converting enzyme 2 (ACE2) recently was identified as a homologue of ACE that preferentially forms Ang-(1-7) from Ang II. Reduced ACE2 expression in the kidney of hypertensive rats suggests its contribution to the balance of Ang II to Ang-(1-7). Although ACE2 was initially localized in peripheral organs such as heart, kidney and testis, we identified ACE2 mRNA and protein in distinct brain regions from both neonatal and adult Sprague-Dawley rats as well as cultured neurons and astrocytes. Further, we demonstrated that treatment of cultured neurons and astrocytes with Ang II caused a marked reduction in ACE2 mRNA and protein. In exciting new results, we showed that inhibition of ACE2 reduced baroreflex control of heart rate, suggesting that the regulation of ACE2 and alterations in the ratio of Ang II to Ang-(1-7) is critical in central control of blood pressure. We propose that ACE2 serves as a major regulator of the balance of Ang ll/Ang-(1-7) concentration in the brain. In Specific Aim 1, we will ascertain whether Ang II regulates ACE2 mRNA and protein in the brain of transgenic rats expressing altered peptide concentrations and whether baroreflex control of heart rate is altered in these rats or following inhibition of ACE2 activity. Studies in Specific Aim 2 will focus on ACE2 secreted from cultured astrocytes, to assess its substrate specificity and determine the molecular mechanism of ACE2 secretion from cultured astrocytes and neurons and from intact brain slices. Finally, in Specific Aim 3, we will identify the transcriptional regulators of ACE2 in astrocytes and neurons. Relevance: ACE2 preferentially converts Ang II to Ang-(1-7), peptides which have opposing actions in the central control of blood pressure. The regulation of ACE2 may be critical to maintaining the normal function of the renin-angiotensin system in the brain.