ADCK4 mutations promote steroid-resistant nephrotic syndrome through CoQ10 biosynthesis disruption
Shazia Ashraf, et al.
Shazia Ashraf, et al.
View: Text | PDF
Research Article

ADCK4 mutations promote steroid-resistant nephrotic syndrome through CoQ10 biosynthesis disruption

Abstract

Identification of single-gene causes of steroid-resistant nephrotic syndrome (SRNS) has furthered the understanding of the pathogenesis of this disease. Here, using a combination of homozygosity mapping and whole human exome resequencing, we identified mutations in the aarF domain containing kinase 4 (ADCK4) gene in 15 individuals with SRNS from 8 unrelated families. ADCK4 was highly similar to ADCK3, which has been shown to participate in coenzyme Q10 (CoQ10) biosynthesis. Mutations in ADCK4 resulted in reduced CoQ10 levels and reduced mitochondrial respiratory enzyme activity in cells isolated from individuals with SRNS and transformed lymphoblasts. Knockdown of adck4 in zebrafish and Drosophila recapitulated nephrotic syndrome-associated phenotypes. Furthermore, ADCK4 was expressed in glomerular podocytes and partially localized to podocyte mitochondria and foot processes in rat kidneys and cultured human podocytes. In human podocytes, ADCK4 interacted with members of the CoQ10 biosynthesis pathway, including COQ6, which has been linked with SRNS and COQ7. Knockdown of ADCK4 in podocytes resulted in decreased migration, which was reversed by CoQ10 addition. Interestingly, a patient with SRNS with a homozygous ADCK4 frameshift mutation had partial remission following CoQ10 treatment. These data indicate that individuals with SRNS with mutations in ADCK4 or other genes that participate in CoQ10 biosynthesis may be treatable with CoQ10.

Authors

Shazia Ashraf, Heon Yung Gee, Stephanie Woerner, Letian X. Xie, Virginia Vega-Warner, Svjetlana Lovric, Humphrey Fang, Xuewen Song, Daniel C. Cattran, Carmen Avila-Casado, Andrew D. Paterson, Patrick Nitschké, Christine Bole-Feysot, Pierre Cochat, Julian Esteve-Rudd, Birgit Haberberger, Susan J. Allen, Weibin Zhou, Rannar Airik, Edgar A. Otto, Moumita Barua, Mohamed H. Al-Hamed, Jameela A. Kari, Jonathan Evans, Agnieszka Bierzynska, Moin A. Saleem, Detlef Böckenhauer, Robert Kleta, Sherif El Desoky, Duygu O. Hacihamdioglu, Faysal Gok, Joseph Washburn, Roger C. Wiggins, Murim Choi, Richard P. Lifton, Shawn Levy, Zhe Han, Leonardo Salviati, Holger Prokisch, David S. Williams, Martin Pollak, Catherine F. Clarke, York Pei, Corinne Antignac, Friedhelm Hildebrandt

×

Figure 3

ADCK4 localizes to the mitochondria and cytoplasm of podocytes in adult rat glomeruli and also in cultured human podocytes.

Options: View larger image (or click on image) Download as PowerPoint
ADCK4 localizes to the mitochondria and cytoplasm of podocytes in adult ...
(A–C) Coimmunofluorescence of ADCK4 with (A) WT1 as well as (B) MTCO1 and (C) COXIV in adult rat glomeruli. ADCK4 partially colocalizes to mitochondria with the 2 mitochondrial markers COXIV and MTCO1. Scale bar: 10 μm. (D) Immunogold electron microscopy of adult rat kidney displays localization of ADCK4 (black arrowheads) at podocyte foot processes of glomeruli. A control without a primary antibody is shown on the left. Scale bar: 1 μm; ×2.5 (inset). (E) Podocytes were transfected with ADCK4-RFP and stained with an anti-COXIV antibody. ADCK4 partially colocalizes to mitochondria with COXIV. Note that ADCK4 also localizes along the plasma membrane (white arrowheads) in podocytes. Scale bar: 25 μm. (F) Subcellular fractionation of ADCK4 in undifferentiated and differentiated podocytes. Mitochondrial and cytosol fractions were prepared and immunoblotted for ADCK4, MTCO1, and COXIV, respectively. Each lane was loaded with 50 μg protein. Note that ADCK4 is present in both mitochondrial (marked by MTCO1 and COXIV), and cytosolic fractions in both undifferentiated and differentiated podocytes. W, whole cell lysates; Cyto, cytosol fraction; MT, mitochondrial fraction.