Role of RTN1A in the Progression of Diabetic Nephropathy

项目摘要 糖尿病肾病（DKD）仍然是美国ESRD的主要原因，治疗方案包括 有限公司因此，识别DKD进展的促成因素对我们来说至关重要。通过分析 在具有不同疾病进展速率的小鼠模型中的转录组学数据集，我们鉴定了Reticulon-1 （Rtn 1），一种编码内质网（ER）相关蛋白的基因，作为进展的危险因素， CKD。我们发现RTN 1A表达在病变肾脏中显著增加，并且与肾脏病理改变呈负相关。 与DKD患者的eGFR相关。在体外实验中，我们发现RTN 1A介导了肾细胞中的ER应激和细胞凋亡。 肾小管上皮细胞（RTEC）。在体内，我们发现，Rtn 1a表达的整体敲低减弱了 链脲佐菌素（STZ）诱导的糖尿病小鼠的蛋白尿和肾损伤。在上一个融资周期，我们 进一步证明了STZ诱导的糖尿病小鼠中RTEC中RTN 1A表达的诱导 导致肾功能下降和肾纤维化的发展，这在糖尿病患者中通常不会观察到 STZ诱导的糖尿病小鼠。RTN 1A相互作用蛋白的筛选令人惊讶地表明，RTN 1A的高度相互作用蛋白质在细胞中表达。 排序的蛋白质是线粒体蛋白质，例如己糖激酶1（HK 1）、TOMM 40和SLC 25 A12。 与此一致，最近的一项研究也表明，在ER-线粒体中存在大量的RTN 1A， 接触部位。ER-线粒体接触（EMC），或也称为线粒体相关ER膜 （MAMs），对多种细胞内事件具有多效性作用，包括线粒体损伤、Ca 2 + 信号传导、ER应激、凋亡和自噬。然而，EMC与肾脏疾病的直接关联 还没有报道。我们的初步数据显示RTN 1A在HK 2细胞中的过表达不能诱导 不仅是内质网应激，还有线粒体功能障碍。高糖同时增加内质网应激和线粒体膜电位， 在HK 2细胞中，RTN 1A过表达进一步加重了功能障碍。在体内，糖尿病小鼠与 RTN 1A在RTEC中的过表达增加了ER应激和线粒体功能障碍的标志物。 这些数据表明RTN 1A可能在介导ER应激和线粒体功能障碍中起关键作用 通过EMC。此外，我们证实RTN 1A与HK 1相互作用，并诱导HK 1降解。 RTEC和HK 1是细胞凋亡和炎性小体激活的关键调节因子。根据这些数据，我们 假设RTN 1A介导的EMC在诱导肾小管细胞损伤和进展中起关键作用， 的DKD。为了验证这一点，我们建议确定1）RTN 1A在RTEC损伤中介导EMC的作用， 糖尿病状况; 2）RTN 1A介导的EMC在糖尿病状况下的RTEC损伤中的机制;和3）RTN 1A介导的EMC在糖尿病状况下的RTEC损伤中的机制。 将EMC作为DKD治疗的潜在干预措施。

Project Summary Diabetic kidney disease (DKD) remains as the leading cause of ESRD in USA and the treatment options are limited. Therefore, it is critical for us to identify contributing factors for the progression of DKD. By analyzing the transcriptomic datasets in mouse models with different rates of disease progression, we identified Reticulon-1 (Rtn1), a gene encoding an endoplasmic reticulum (ER)-associated protein, as a risk factor for progression of CKD. We found that RTN1A expression is markedly increased in the diseased kidney and inversely correlated with eGFR in human with DKD. In vitro, we showed that RTN1A mediates ER stress and apoptosis in renal tubular epithelial cells (RTEC). In vivo, we showed that a global knockdown of Rtn1a expression attenuated albuminuria and kidney injury in streptozotocin (STZ)-induced diabetic mice. During the last funding period, we further demonstrated that the induction of RTN1A expression in RTEC in the STZ-induced diabetic mice resulted in the decline of renal function and development of renal fibrosis, which are not typically observed in STZ-induced diabetic mice. Screening of RTN1A-interacting proteins surprisingly showed that the highly ranked proteins were mitochondrial proteins, such as hexokinase 1 (HK1), TOMM40, and SLC25A12. Consistent with this, a recent study also demonstrates a large amount of RTN1A in the ER-mitochondrial contact sites. ER-mitochondrial contact (EMC), or also referred as mitochondria-associated ER membranes (MAMs), have pleiotropic effects on a variety of intracellular events including mitochondrial damage, Ca2+ signaling, ER stress, apoptosis, and autophagy. However, the direct association of EMC with kidney disease has not been reported. Our preliminary data showed that overexpression of RTN1A in HK2 cells induced not only ER stress but also mitochondrial dysfunction. High glucose increased both ER stress and mitochondrial dysfunction in HK2 cells, which was further aggravated by RTN1A overexpression. In vivo, diabetic mice with RTN1A overexpression in RTEC had increased markers for both ER stress and mitochondrial dysfunction. These data suggest a critical role of RTN1A in mediating both ER stress and mitochondrial dysfunction likely through EMC. Also, we confirmed that RTN1A interacted with HK1 and induced the degradation of HK1 in RTEC and HK1 is a key regulator of apoptosis and inflammasome activation. Based on these data, we hypothesize that RTN1A-mediated EMC plays a critical role in inducing tubular cell injury and the progression of DKD. To test this, we propose to determine 1) the role of RTN1A in mediating EMC in RTEC injury in diabetic condition; 2) the mechanism of RTN1A-mediated EMC in RTEC injury in diabetic condition; and 3) the potential interventions to regulate EMC as a therapy for DKD.