Krüppel-like factor 6 regulates mitochondrial function in the kidney
Sandeep K. Mallipattu, … , Vincent W. Yang, John C. He
Sandeep K. Mallipattu, … , Vincent W. Yang, John C. He
Published February 17, 2015
Citation Information: J Clin Invest. 2015;125(3):1347-1361. https://doi.org/10.1172/JCI77084.
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Research Article

Krüppel-like factor 6 regulates mitochondrial function in the kidney

Abstract

Maintenance of mitochondrial structure and function is critical for preventing podocyte apoptosis and eventual glomerulosclerosis in the kidney; however, the transcription factors that regulate mitochondrial function in podocyte injury remain to be identified. Here, we identified Krüppel-like factor 6 (KLF6), a zinc finger domain transcription factor, as an essential regulator of mitochondrial function in podocyte apoptosis. We observed that podocyte-specific deletion of Klf6 increased the susceptibility of a resistant mouse strain to adriamycin-induced (ADR-induced) focal segmental glomerulosclerosis (FSGS). KLF6 expression was induced early in response to ADR in mice and cultured human podocytes, and prevented mitochondrial dysfunction and activation of intrinsic apoptotic pathways in these podocytes. Promoter analysis and chromatin immunoprecipitation studies revealed that putative KLF6 transcriptional binding sites are present in the promoter of the mitochondrial cytochrome c oxidase assembly gene (SCO2), which is critical for preventing cytochrome c release and activation of the intrinsic apoptotic pathway. Additionally, KLF6 expression was reduced in podocytes from HIV-1 transgenic mice as well as in renal biopsies from patients with HIV-associated nephropathy (HIVAN) and FSGS. Together, these findings indicate that KLF6-dependent regulation of the cytochrome c oxidase assembly gene is critical for maintaining mitochondrial function and preventing podocyte apoptosis.

Authors

Sandeep K. Mallipattu, Sylvia J. Horne, Vivette D’Agati, Goutham Narla, Ruijie Liu, Michael A. Frohman, Kathleen Dickman, Edward Y. Chen, Avi Ma’ayan, Agnieszka B. Bialkowska, Amr M. Ghaleb, Mandayam O. Nandan, Mukesh K. Jain, Ilse Daehn, Peter Y. Chuang, Vincent W. Yang, John C. He

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Figure 10

SCO2, a downstream target of KLF6, is critical to preventing the activation of intrinsic apoptotic pathway.

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SCO2, a downstream target of KLF6, is critical to preventing the activat...
Primary podocytes were isolated from WT and Tg26 mice (FVB/N). RNA was extracted, and real-time PCR was performed. (A) Sco2 mRNA expression was compared between WT and Tg26 mice (n = 5). Mann-Whitney U test, **P < 0.01. (B) SCO2 expression was confirmed using immunofluorescence. Representative images of six independent experiments are shown in the left panel (original magnification, ×20). A total of 30 glomeruli per mouse were selected, and SCO2 expression was quantified in the glomerular region (n = 6) as shown in the right panel. Unpaired t test ***P < 0.001. (C) To assess the role of SCO2 in mitochondrial injury, shRNA-mediated SCO2 knockdown was performed in human podocytes. Western blot analysis was performed for SCO2 and cleaved caspase-9. Representative blots from three independent experiments are shown in the top panel. Quantification by densitometry (n = 3) is shown in the bottom panel. Mann-Whitney U test, **P < 0.01. (D) Immunofluorescence images of cytochrome c staining in EV-shRNA and SCO2-shRNA podocytes are shown. Representative images of four independent experiments are shown to demonstrate the distribution of cytochrome c staining (original magnification, ×20). Arrows show mitochondrial cytochrome c distribution. Arrowheads show cytosolic distribution of cytochrome c.