Deficiency in Apoptosis-Inducing Factor Recapitulates Chronic Kidney Disease via Aberrant Mitochondrial Homeostasis

Melinda T. Coughlan, Gavin C. Higgins, Tuong-Vi Nguyen, Sally A. Penfold, Vicki Thallas-Bonke, Sih Min Tan, Georg Ramm, Nicole J. Van Bergen, Darren C. Henstridge, Karly C. Sourris, Brooke E. Harcourt, Ian A. Trounce, Portia M. Robb, Adrienne Laskowski, Sean L. McGee, Amanda J. Genders, Ken Walder, Brian G. Drew, Paul Gregorevic, Hongwei Qian, Merlin C. Thomas, George Jerums, Richard J. Macisaac, Alison Skene, David A. Power, Elif I. Ekinci, Xiaonan W. Wijeyeratne, Linda A. Gallo, Michal Herman-Edelstein, Michael T. Ryan, Mark E. Cooper, David R. Thorburn, Josephine M. Forbes

Apoptosis inducing factor (AIF) is a mitochondrial flavoprotein with dual roles in redox signalling and programmed cell death. Deficiency in AIF is known to result in defective oxidative phosphorylation (OXPHOS), via loss of complex I activity and assembly in other tissues. Since the kidney relies on OXPHOS for metabolic homeostasis, we hypothesised that a decrease in AIF would result in chronic kidney disease (CKD). Here, we report that partial knockdown of Aif in mice recapitulates many features of CKD, in association with a compensatory increase in the mitochondrial ATP pool via a shift toward mitochondrial fusion, excess mitochondrial ROS production and Nox4 up-regulation. However, despite a 50% lower AIF protein content in the kidney cortex, there was no loss of complex I activity or assembly. When diabetes was superimposed onto Aif knockdown there were extensive changes in mitochondrial function and networking which augmented the renal lesion. Studies in patients with diabetic nephropathy showed a decrease in AIF within the renal tubular compartment and lower AIFM1 renal cortical gene expression, which correlated with declining glomerular filtration rate. Lentiviral overexpression of Aif1m rescued glucose-induced disruption of mitochondrial respiration in human primary proximal tubule cells. These studies demonstrate that AIF deficiency is a risk factor for the development of diabetic kidney disease.