Role of Gq Signaling in Promoting Podocyte Injury in Diabetes Mellitus

描述（由申请人提供）：Gq信号在促进糖尿病足细胞损伤中的作用：糖尿病肾病（DN）是发达国家终末期肾病（ESRD）的最常见原因。越来越多的证据表明，足细胞数量减少是糖尿病肾病动物和人类的特征。因为足细胞是具有很少增殖潜力的终末分化细胞，所以丢失的足细胞不能被有效地替代。反过来，足细胞的充分损失导致簇的不稳定和肾小球硬化。虽然DN中足细胞损失的病因学是复杂的，但大量证据表明细胞表面G蛋白偶联受体（GPCR）在DN中起重要的损伤促进作用，包括血管紧张素II（ANGII）、血栓烷（TP）、血管紧张素（EP 1）和内皮素（ETA）的受体。事实上，这些GPCR由肾小球足细胞表达，并且这些受体系统中的几种已显示在体外和体内促进足细胞损伤。这些促进损伤的GPCR的共同特征是Gq α-亚基（Gq）的活化。因此，Gq及其下游效应物的激活可能是与其他信号级联协同促进DN足细胞损伤的最终共同信号通路。在这方面，我们发现，Gq依赖CN激活促进足细胞凋亡，部分是通过诱导CN响应基因COX 2。基于这些观察，我们假设Gq偶联信号级联是通过促进足细胞凋亡而导致DN足细胞损伤的重要介质。为了研究这一假设，提出了3个具体目标。在具体目标#1中，我们已经创建了转基因（TG）小鼠，其使用诱导型启动子系统在肾小球足细胞中特异性表达组成型活化的Gq α-亚基（GqQ>L）或Gq抑制剂（Gqi）。我们将使用GqQ>L或Gqi TG小鼠来确定在1型糖尿病的遗传模型（秋田小鼠）中，特异性地分别在肾小球足细胞中激活或抑制Gq是否调节肾脏疾病的严重程度。在具体目标#2中，我们将确定由Gq激活的信号级联，其促进永生化足细胞系以及体内的足细胞凋亡。最后，在具体目标#3中，我们将产生在足细胞中特异性缺乏COX 2的小鼠，然后确定足细胞特异性COX 2缺失对秋田小鼠中足细胞凋亡和肾小球损伤的影响。这些研究将测试抑制Gq信号传导作为DN的潜在治疗策略的效用以及足细胞COX 2表达在疾病发病机制中的作用。如果成功的话，这些结果可能为治疗糖尿病肾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.