Cellular Regulation of Angiotensin Converting Enzyme 2

描述（由申请人提供）：几十年的研究已经确定肾素-血管紧张素系统是血压、体内平衡和细胞增殖的主要调节剂。肾素-血管紧张素系统的作用是由肽血管紧张素II （Ang II）和血管紧张素-(1-7)[Ang-(1- 7)]的相反作用介导的，Ang II是一种有效的血管收缩剂和有丝分裂原，Ang-(1- 7)]是一种血管扩张剂和生长抑制剂。血管紧张素转换酶2 （ACE2）最近被发现是ACE的同源物，它优先从Ang II生成Ang-(1-7)。高血压大鼠肾脏中ACE2表达降低提示其参与Ang II与Ang-之间的平衡（1-7）。虽然ACE2最初定位于外周器官，如心脏、肾脏和睾丸，但我们在新生儿和成年Sprague-Dawley大鼠以及培养的神经元和星形胶质细胞的不同脑区发现了ACE2 mRNA和蛋白。此外，我们证明用Ang II处理培养的神经元和星形胶质细胞导致ACE2 mRNA和蛋白的显著降低。在令人兴奋的新结果中，我们发现ACE2的抑制降低了心率的压力反射控制，这表明ACE2的调节和Ang II与Ang-(1-7)比值的改变对血压的中枢控制至关重要。我们认为ACE2是大脑中Ang ll/Ang-(1-7)浓度平衡的主要调节因子。在Specific Aim 1中，我们将确定Ang II是否调节表达改变肽浓度的转基因大鼠大脑中的ACE2 mRNA和蛋白，以及这些大鼠的心率的压力反射控制是否会在ACE2活性抑制后发生改变。Specific Aim 2的研究将重点关注培养的星形胶质细胞分泌的ACE2，评估其底物特异性，并确定培养的星形胶质细胞和神经元以及完整脑切片分泌ACE2的分子机制。最后，在Specific Aim 3中，我们将鉴定星形胶质细胞和神经元中ACE2的转录调节因子。相关性：ACE2优先将Ang II转化为Ang-(1-7)，这是一种在血压中枢控制中具有相反作用的肽。ACE2的调控可能对维持大脑肾素-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.