Role of BMPRII Mutants in the Pathogenesis of Pulmonary Hypertension

描述(申请人提供)：肺动脉高压(PH)的特征是肺血管阻力增加，阻碍右室射血，导致右室衰竭。原发性肺高压(PPH)是一种罕见的进展性疾病，4年内死亡率为30%。骨形态发生蛋白受体II(BMPRII)是转化生长因子受体家族的一员，最近在50%以上的家族性PPH患者和30%的散发性PPH患者中发现了BMPRII的胚系突变。在胞外、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域(尾部结构域)都发现了突变。该应用的长期目标是了解BMPRII突变在肺动脉高压发病机制中的分子机制(S)。我们发现BMPs促进了正常人肺动脉平滑肌细胞(PASMCs)的细胞凋亡。BMP介导的PASMCs的凋亡与caspase-3、-8和-9的激活、细胞色素c的释放和Bcl-2的下调有关。在PPH患者中发现的表达BMPRII突变形式的PASMC对BMP介导的细胞凋亡具有抵抗力。需要检验的具体假设是，BMPRII的突变(S)破坏了BMP介导的PASMCs的凋亡，这是维持肺血管系统正常细胞数量所必需的。在特定的目标1中，我们将研究BMP7介导的PASMCs的凋亡信号通路。在特定的目标2中，我们将鉴定在PPH中发现的BMPRII突变体的生物学活性，并建立表达BMPRII尾部结构域截断突变基因的转基因小鼠，以检测该突变体在体内的作用。我们最近发现，在哺乳动物细胞中，神经细胞死亡诱导的假定激酶(NIPK)与BMPRII的尾部结构域相互作用。NIPK含有丝氨酸/苏氨酸激酶样结构域。因此，在特定的目标3中，我们将重点研究NIPK与BMPRII尾部结构域相互作用在BMP介导的信号通路调节中的功能作用。这些研究将阐明PASMCs中BMP依赖的细胞凋亡机制以及BMPRII的尾部结构域在BMP信号通路中的调控作用，这对于理解肺动脉高压发病的分子机制具有重要意义。

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.