Transcriptional control of mitochondrial function by KLF6 in diabetic kidney disease

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Project Summary/Abstract The Centers for Disease Control and Prevention estimates more than 10% of adults in the United States, over 20 million Americans have chronic kidney disease. Diabetes Mellitus is the leading risk factor for chronic kidney disease in the United States. Despite improved glycemic control, individuals with Diabetes Mellitus continue to develop and progress to diabetic kidney disease (DKD). In DKD, along with endothelial injury and mesangial expansion, podocyte loss directly contributes to the functional capacity to maintain the renal filtration barrier. Mitochondrial injury is also uniformly observed in DKD and is accompanied by mitochondrial DNA damage as well as altered expression of genes involved in mitochondrial biogenesis, function, and fragmentation. We recently reported the essential role for the zinc-finger transcription factor, Krüppel-like factor 6 (KLF6), in podocyte injury. Specifically, we demonstrated that KLF6 is an early inducible injury response gene that enhances mitochondrial respiratory complex IV (cytochrome c oxidase, COX) expression, thereby abrogating the release of cytochrome c and activation of apoptosis in the setting of cell stress. KLF6 maintains COX assembly by regulating the expression of key transcripts involved in mitochondrial replication, transcription, and function under cell stress. To date, this is the first study demonstrating a direct regulatory effect of a zinc-finger transcription factor on mitochondrial function in the podocyte. Our preliminary data also suggests that podocyte-specific loss of Klf6 (Klf6-/-) accelerated DKD in mice. In addition, we observed a significant increase in mitochondrial injury with podocyte loss in the diabetic Klf6-/- mice as compared to diabetic wildtype mice. Furthermore, we observed that modulating the level of KLF6 expression in the podocyte directly regulated mitochondrial structure, function, genes involved in COX assembly, and apoptosis. Finally, KLF6 expression was reduced in DKD as compared to healthy control subjects in three independent gene expression arrays from human kidney biopsies. The objective of this research proposal is to demonstrate that KLF6 is required to prevent mitochondrial dysfunction and podocyte injury in DKD. The long-term goal of our project is to identify “druggable” targets in restoring mitochondrial function in podocytes of diabetic kidney. This proposal will address a current gap in the field by demonstrating that COX assembly is critical to preventing mitochondrial dysfunction in podocytes of diabetic kidney. The potential impact of this proposed research is that it will shed new light on the critical role of respiratory complex assembly in improving mitochondrial function in the podocyte and slowing the rate of DKD progression in the kidney. Finally, deciphering the mechanism by which KLF6 regulates COX assembly will provide us with a novel pathway to target in DKD.