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.

R01DK079057

2008-04-01

2013-01-31