Role of BMPRII Mutants in the Pathogenesis of Pulmonary Hypertension

描述（由申请人提供）：肺动脉高压（PH）的特征是肺血管阻力增加，阻碍右心室射血，导致右心室衰竭。原发性PH（PPH）是一种罕见但进行性的疾病，4年内死亡率为30%。最近，在超过50%的家族性PPH患者和30%的散发性PPH病例中发现了骨形态发生蛋白受体II（BMPRII）（转化生长因子受体家族成员）的种系突变。在细胞外、配体结合和细胞质丝氨酸/苏氨酸激酶结构域以及长羧基末端区（尾结构域）中发现了突变。本申请的长期目标是了解BMPRII突变导致肺动脉高压发病的分子机制。我们发现骨形成蛋白促进正常人肺动脉平滑肌细胞（PASMCs）的凋亡。在PASMCs中BMP介导的凋亡与半胱天冬酶-3、-8和-9的激活、细胞色素c的释放和Bcl-2的下调相关。在PPH患者中鉴定的表达BMPRII突变形式的PASMCs对BMP介导的细胞凋亡具有抗性。待检验的特定假设是BMPRII中的突变破坏PASMC中BMP介导的细胞凋亡，这是维持肺血管系统中正常细胞数量所需的。在具体目标1中，我们将描述PASMCs中BMP 7介导的抗肿瘤信号通路。在具体目标2中，我们将表征PPH中发现的BMPRII突变体的生物活性，并产生在平滑肌中表达BMPRII尾域截短突变体基因的转基因小鼠，以检查该突变体BMPRII在体内的作用。我们最近发现，神经元细胞死亡诱导的推定激酶（NIPK）与哺乳动物细胞中的BMPRII的尾部结构域相互作用。NIPK含有一个丝氨酸/苏氨酸激酶样结构域。因此，在特定目标3中，我们将重点关注NIPK和BMPRII的尾域之间的相互作用在BMP介导的信号通路的调节中的功能作用。这些研究将阐明PASMCs中BMP依赖性凋亡的机制以及BMPRII的尾部结构域在BMP信号通路调节中的作用，这对于理解肺动脉高压发病机制的分子机制至关重要。

DESCRIPTION (provided by applicant): Pulmonary hypertension (PH) is characterized by an increase in pulmonary vascular resistance that impedes ejection of blood by the right ventricle, leading to right ventricular failure. Primary PH (PPH) is a rare but progressive disease with a mortality of 30 percent over 4 years. Recently germline mutations in bone morphogenetic protein receptor type II (BMPRII), a member of the transforming growth factor ¿ (TGF ¿) receptor family, have been found in over 50 percent of familial PPH patients and in 30 percent of sporadic cases of PPH. Mutations have been found in the extracellular, ligand binding, and cytoplasmic serine/threonine kinase domains, as well as the long carboxyl-terminal region (tail domain). The long-term objective of this application is to understand the molecular mechanism(s) by which BMPRII mutations contribute to the pathogenesis of pulmonary arterial hypertension. We found that BMPs promote, apoptotic cell death in normal human pulmonary artery smooth muscle cells (PASMCs). BMP-mediated apoptosis in PASMCs is associated with activation of caspases-3, -8, and -9, cytochrome c release, and downregulation of Bcl-2. PASMCs expressing mutant forms of BMPRII identified in PPH patients are resistant to BMP- mediated apoptosis. The specific hypothesis to be tested is that mutation(s) in the BMPRII disrupts BMP- mediated apoptosis in PASMCs, which is required for maintenance of normal cell number in the pulmonary vasculature. In Specific Aim 1, we will characterize the apoptotic-signaling pathway mediated by BMP7 in PASMCs. In Specific Aim 2, we will characterize the biological activities of BMPRII mutants found in PPH and generate transgenic mice expressing a BMPRII tail domain truncation mutant gene in smooth muscle to examine the role of this mutant BMPRII in vivo. We recently discovered that neuronal cell death-inducible putative kinase (NIPK) interacts with the tail domain of BMPRII in mammalian cells. NIPK contains a ser/thr kinase-like domain. Therefore, in Specific Aim 3 we will focus on the functional role of the interaction between NIPK and the tail domain of BMPRII in the regulation of BMP-mediated signaling pathways. These studies will elucidate the mechanism of BMP-dependent apoptosis in PASMCs and the role of the tail domain of the BMPRII in the regulation of the BMP signaling pathway, which is of fundamental importance to understanding the molecular mechanisms underlying the pathogenesis of pulmonary hypertension.