NOVEL ANGIOTENSIN II-FORMING PATHWAY IN THE HUMAN HEART

我们已经证明血管紧张素(Ang)H受体存在于 人体心脏的心肌、交感神经和传导系统。 血管紧张素转换酶II对人体心脏有正性变力作用。在……里面 人体心室匀浆，主要(&gt；75%)酶 Ang I到Ang II的转化是由一种丝氨酸蛋白酶产生的 不受血管紧张素转换酶(ACE)抑制剂抑制。我们有 纯化并克隆了该酶。从结构上讲，这种酶属于 类糜蛋白酶的凝乳酶基团，并将 称为人心脏糜酶(HHC)。不像胰凝乳酶和， 事实上，其他凝乳酶，HHC是最特异和最有效的Ang II- 所述的形成酶。 使用心脏小梁的初步研究表明， 人心脏血管紧张素Ⅱ形成的非依赖功能途径 血管紧张素转换酶途径。因为高水平的免疫反应-HHC是 与肌细胞周围的细胞外基质相关，我们 推测心脏血管紧张素转换酶II形成的ACE非依赖性途径 确实依赖于HHC。 我们建议开发基于底物和抗体的特定抑制剂。 最终确定HHC是主要的功能和II- 在人的心脏中形成酶。这些抑制剂将被用来证明 在人类心脏小梁中，血管紧张素I向血管紧张素Ⅱ的主要转化， 而Ang I引起的反应，是由于HHC。 在平行研究中，我们计划以天然形式结晶HHC和 以络合形式研究缓蚀剂的独特结构 HHC的决定因素是其高底物特异性的原因。研究 还计划在功能上映射延伸的底物结合位点 使用血管紧张素转换酶类似物。在人类心脏中，免疫反应-HHC是 储存在心脏肥大细胞颗粒中。为了研究HHC的加工工艺，我们 建议建立一种表达HHC的人心脏肥大细胞系。 该细胞系还将用于研究顺式作用元件和 只允许一部分肥大细胞表达的反式作用因子 HHC。 人类心脏中HHC的存在表明心脏血管紧张素II 在治疗高血压和高血压的过程中不得停止形成 血管紧张素转换酶抑制剂治疗充血性心力衰竭。取得的成就 拟议研究的目标最终将帮助我们理解 心脏血管紧张素Ⅱ在正常心脏和衰竭心脏中形成的后果， 并将提高我们对心力衰竭及其治疗的理解。

We have shown the presence of angiotensin (Ang) H receptors in the myocardium, sympathetic nerves and conduction system of the human heart. Ang II elicits a positive inotropic effect in the human heart. In homogenates of the human cardiac ventricle, the major (>75%) enzymatic conversion of Ang I to Ang II is produced by a serine proteinase that is not inhibited by Ang I-converting enzyme (ACE) inhibitors. We have purified and cloned this proteinase. Structurally, this enzyme belongs to the chymase group of chymotrypsin-like proteinases and will be referred to as human heart chymase (hHC). Unlike chymotrypsin and, indeed, other chymases, hHC is the most specific and efficient Ang II- forming enzyme described. Preliminary studies using cardiac trabeculae show the presence of a functional pathway for Ang II formation in the human heart independent of the ACE pathway. Because high levels of immunoreactive-hHC are associated with the extracellular matrix surrounding myocytes, we speculate that the ACE-independent pathway of cardiac Ang II formation is indeed hHC-dependent. We propose to develop specific substrate-and antibody-based inhibitors of hHC to definitively establish that hHC is the major functional Ang II- forming enzyme in the human heart. These inhibitors will be used to show that the major conversion of Ang I to Ang II in human cardiac trabeculae, and that the response elicited by Ang I, are due to hHC. In parallel studies, we plan to crystallize hHC in the native form and in the inhibitor complexed form to study the unique structural determinants of hHC responsible for its high substrate specifity. Studies are also planned to functionally map the extended substrate binding site of hHC using Ang I analogs. In the human heart, immunoreactive-hHC is stored in cardiac mast cell granules. To study the processing of hHC, we propose to develop a human cardiac mast cell line that expresses hHC. This cell line will also be used to study the cis-acting elements and trans-acting factors that allow only a subset of mast cells to express hHC. The presence of hHC in the human heart suggests that cardiac Ang II formation may not cease during the treatment of hypertension and congestive heart failure with ACE inhibitors. The achievement of the goals of the proposed studies will ultimately help us understand the consequence of cardiac Ang II formation in the normal and failing heart, and will improve our understanding of heart failure and its treatment.