Role of Gq Signaling in Promoting Podocyte Injury in Diabetes Mellitus

描述(申请人提供)：GQ信号在促进糖尿病足细胞损伤中的作用：在发达国家，糖尿病肾病(DN)是终末期肾病(ESRD)的最常见原因。越来越多的证据表明，足细胞数量减少是患有糖尿病肾病的动物和人类的特征。由于足细胞是终末分化的细胞，几乎没有增殖的潜力，失去的足细胞不能有效地被替代。反过来，足细胞的大量丢失会导致肾小球不稳定和肾小球硬化。虽然糖尿病肾病足细胞丢失的病因很复杂，但大量证据表明，细胞表面G蛋白偶联受体(GPCRs)在糖尿病肾病中起着重要的促损伤作用，包括血管紧张素II(AngII)、血栓素(TP)、前列腺素(EP1)和内皮素(ETA)的受体。事实上，这些GPCRs是由肾小球足细胞表达的，其中几个受体系统在体外和体内都被证明促进足细胞损伤。这些促进损伤的GPCRs的一个共同特征是激活Gqα亚单位(Gq)。因此，GQ及其下游效应器的激活可能是最终共同的信号通路，与其他信号级联协同促进糖尿病肾病足细胞损伤。在这方面，我们发现依赖GQ的CN激活促进足细胞凋亡，部分是通过诱导CN反应基因COX2来实现的。基于这些观察结果，我们推测GQ偶联信号通路是糖尿病肾病足细胞损伤的重要介导者，它通过促进足细胞的凋亡而发生损伤。为了验证这一假设，我们提出了三个具体目标。在特定的目标#1中，我们创造了转基因(TG)小鼠，使用可诱导的启动子系统在肾小球足细胞中表达结构性激活的GQα亚基(GQ&gT；L)或GQ抑制物(GQI)。我们将使用GQQ&GT；L或GQI TG小鼠来确定在1型糖尿病遗传模型(秋田鼠)中，分别激活或抑制GQ，尤其是肾小球足细胞是否调节肾脏疾病的严重程度。在特定的目标#2中，我们将确定GQ激活的信号级联，促进永生化足细胞系中以及体内的足细胞凋亡。最后，在特定的目标#3中，我们将创建足细胞特异性缺失COX2的小鼠，然后确定足细胞特异性COX2缺失对秋田小鼠足细胞凋亡和肾小球损伤的影响。这些研究将测试抑制GQ信号作为一种潜在的治疗策略在糖尿病肾病中的作用，以及足细胞COX2表达在疾病发病机制中的作用。如果成功，这一结果可能会为治疗糖尿病肾脏疾病提供新的治疗策略。

DESCRIPTION (provided by applicant): Role of Gq signaling in promoting podocyte injury in diabetes mellitus: Diabetic nephropathy (DN) is the most common cause of end stage renal disease (ESRD) in developed countries. Accumulating evidence indicates that a reduced number of podocytes are a characteristic feature of both animals and humans with diabetic kidney disease. Because podocytes are terminally differentiated cells with little potential for proliferation, podocytes that are lost cannot be effectively replaced. In turn, sufficient loss of podocytes leads to instability of the tuft and glomerulosclerosis. While the etiology of podocyte loss in DN is complex, a large body of evidence suggests that cell surface G protein coupled receptors (GPCRs) play an important, injury promoting role in DN including receptors for angiotensin II (ANGII), thromboxanes (TP), prostaglandins (EP1) and endothelins (ETA). Indeed, these GPCRs are expressed by glomerular podocytes and several of these receptor systems have been shown to promote podocyte injury both in vitro and in vivo. A common feature of these injury-promoting GPCRs is activation of Gq a-subunits (Gq). Activation of Gq and its downstream effectors might, therefore, be a final common signaling pathway that synergizes with other signaling cascades to promote podocyte injury in DN. In this regard, we found that Gq dependent CN activation promotes podocyte apoptosis, in part, by induction of the CN responsive gene COX2. Based on these observations, we hypothesized that Gq-coupled signaling cascades are important mediators of podocyte injury in DN by promoting podocyte apoptosis. To investigate this hypothesis, 3 specific aims are proposed. In specific aim #1, we have created transgenic (TG) mice that express either a constitutively activate Gq a-subunit (GqQ>L) or a Gq inhibitor (Gqi) specifically in glomerular podocytes using an inducible promoter system. We will use GqQ>L or Gqi TG mice to determine if either activating or inhibiting Gq, respectively, specifically in glomerular podocytes modulates the severity of kidney disease in a genetic model of type 1 diabetes (Akita mice). In specific aim #2, we will determine the signaling cascades activated by Gq that promote podocyte apoptosis in an immortalized podocyte cell line as well as in vivo. Lastly, in specific aim #3, we will create mice lacking COX2 specifically in podocytes and then determine the effects of podocyte specific COX2 deletion on podocyte apoptosis and glomerular damage in Akita mice. These studies will test the utility of inhibiting Gq signaling as a potential treatment strategy in DN and the role of podocyte COX2 expression in disease pathogenesis. If successful, the results may suggest novel therapeutic strategies for treating diabetic kidney disease.