AATF and Renal Protection

描述（由申请人提供）：肾小管上皮细胞特别容易受到缺血/再灌注（I/R）诱导的损伤。I/R是急性肾功能衰竭的最常见原因，是一个发病率和死亡率极高的主要临床问题。尽管细胞凋亡和坏死细胞死亡都可导致肾I/R损伤，但目前尚无有效的治疗方法。我们最近发现AATF（凋亡拮抗转录因子）在肾近端小管细胞中表达，在肾I/R模型中，它在抑制细胞死亡途径中起着至关重要的作用。AATF的表达增加明显改善，而RNA干扰（RNAi）沉默AATF加剧了肾小管上皮细胞I/R后的凋亡和坏死细胞死亡。初步研究表明，AATF与促凋亡蛋白Par-4（前列腺凋亡反应-4）相互作用，阻断Par-4在肾小管上皮细胞中启动的细胞死亡途径。重要的是，par4依赖性细胞死亡似乎是通过核易位和抑制bcl-2转录介导的。此外，我们发现AATF是蛋白激酶Akt1的新型磷酸化底物，是磷脂酰肌醇3-激酶的重要下游靶点。这些发现开启了一种令人兴奋的可能性，即AATF代表Par4-

DESCRIPTION (provided by applicant): Renal tubule epithelial cells are particularly vulnerable to ischemia/reperfusion (I/R)-induced injury. I/R is the most common cause of acute renal failure, a major clinical problem with exceptionally high morbidity and mortality. Although both apoptotic and necrotic cell death contribute renal I/R injury, effective treatment for this devastating condition is lacking. We have recently found that AATF (apoptosis antagonizing transcription factor) is expressed in renal proximal tubule cells wherein it plays a crucial role in inhibiting cell-death pathways in well-characterized models of renal I/R. Increased expression of AATF significantly ameliorated, while silencing of AATF by RNA interference (RNAi) exacerbated apoptotic and necrotic cell death following I/R in renal tubule epithelial cells. Preliminary studies indicates that AATF interacts with the proapoptotic protein Par-4 (prostate apoptosis response-4), and blocks cell death pathways initiated by Par-4 in renal tubule epithelial cells. Of importance, Par4-dependent cell death seems to be mediated by nuclear translocation and suppression of bcl-2 transcription. In addition, we found that AATF was novel phosphorylation substrate of Akt1, a protein kinase and an important downstream target of phosphatidylinositol 3-kinase. These findings open the exciting possibility that AATF represents a Par4- interacting, Akt1-regulated pathway that plays a critical role in controlling renal damage following I/R. We propose three specific aims to investigate this novel mechanism of renal protection: (1) to determine if AATF plays a critical role in protection of renal tubule epithelial cells, and if targeted delivery of AATF in the kidney using recombinant adeno-associated virus (AAV)-based vectors can be used as a potential therapeutic approach for I/R-induced renal injury in vivo; (2) to investigate the molecular mechanisms of Par4-mediaited renal toxicity and to study how transcriptional activation of the anti-apoptotic gene bcl-2 is regulated by AATF/Par-4 complex formation; and (3) to examine if binding and phosphorylation of AATF by Akt1 represents a novel regulatory mechanism underlying the renoprotective actions of AATF following I/R. Targeted delivery of AATF in the kidney by pharmacological and/or genetic manipulations may provide novel therapeutic applications for ischemia-reperfusion induced renal injury. PUBLIC HEALTH RELEVANCE Ischemia/reperfusion-induced renal injury (IRI) is the most common cause of acute renal failure, a major clinical problem with exceptionally high morbidity and mortality. Our preliminary studies suggest that AATF (apoptosis antagonizing transcription factor) is expressed in renal proximal tubule cells wherein it may play a crucial role in protecting against IRI. This project will use multidisciplinary approaches to examine the mechanisms underlying the renal protective actions of AATF at cellular and molecular levels, and to determine if pharmacological and/or genetic manipulations of renal AATF may provide new therapeutic applications for IRI.