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 6

KLF6 binds to the promoter region of SCO2.

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KLF6 binds to the promoter region of SCO2. To confirm that binding sites...
To confirm that binding sites for KLF6 are present in the promoter region of SCO2. KLF6 was initially overexpressed in HEK 293 cells using LentiORF transfection, and ChIP was performed. (A) Overexpression of KLF6 was confirmed with Western blot analysis (left panel), and the presence of putative KLF6 binding sites in the promoter of SCO2 in HEK 293 cells is shown (right panel) (n = 4). Kruskal-Wallis test with Dunn’s post-hoc test, **P < 0.01 vs. the two other groups. (B) Cultured podocytes were treated with ADR for 12 hours, RNA was extracted for real-time PCR, and Sco2 mRNA expression is shown (n = 4). Kruskal-Wallis test with Dunn’s post-hoc test, *P < 0.05, **P < 0.01. (C) SCO2 expression level was also confirmed by immunofluorescence in Podocin-Cre Klf6fl/fl and Podocin-Cre Klf6+/+ mice treated with and without ADR. Representative pictures of six mice in each group are shown in the top panel (original magnification, ×20). A total of 30 glomeruli per mouse were selected, and SCO2 expression was quantified in the glomerular region (n = 6) shown in the bottom panel. Kruskal-Wallis test with Dunn’s post-hoc test, **P < 0.01. (D) MT-CO2 levels were assessed in Podocin-Cre Klf6fl/fl and Podocin-Cre Klf6+/+ mice treated with and without ADR. Representative immunofluorescence images of six mice in each group are shown in the top panel (original magnification, ×20). A total of 30 glomeruli per mouse were selected, and MT-CO2 expression was quantified in the glomerular region (n = 6) in the bottom panel. Kruskal-Wallis test with Dunn’s post-hoc test, **P < 0.01, ***P < 0.001.