APOL1 risk allele RNA contributes to renal toxicity by activating protein kinase R

Koji Okamoto,Shashi Shrivastav,Hidefumi Wakashin,Jeffrey B Kopp,Cheryl A Winkler,Avi Z Rosenberg,Kosuke Suzuki,Maarten Hoek,Myung K Shin,Patricio E Ray,Eisei Noiri,Jason W Rausch,Preeti Chandra,Zhe Han,Patrick D Dummer,Stephen M Hewitt,Yulong Fu,Stuart F J Le Grice,Joon-Yong Chung

doi:10.1038/s42003-018-0188-2

Abstract

APOL1 risk alleles associate with chronic kidney disease in African Americans, but the mechanisms remain to be fully understood. We show that APOL1 risk alleles activate protein kinase R (PKR) in cultured cells and transgenic mice. This effect is preserved when a premature stop codon is introduced to APOL1 risk alleles, suggesting that APOL1 RNA but not protein is required for the effect. Podocyte expression of APOL1 risk allele RNA, but not protein, in transgenic mice induces glomerular injury and proteinuria. Structural analysis of the APOL1 RNA shows that the risk variants possess secondary structure serving as a scaffold for tandem PKR binding and activation. These findings provide a mechanism by which APOL1 variants damage podocytes and suggest novel therapeutic strategies.

Highlights

Apolipoprotein L1 (APOL1) risk alleles associate with chronic kidney disease in African Americans, but the mechanisms remain to be fully understood
We hypothesized that APOL1 genetic variants might interfere with translation initiation, and we examined the status of eIF2α
We found markedly increased phosphorylation in HEK293FT cells that over-expressed APOL1 risk alleles G1 or G2 compared to wild type G0 allele or empty vector (Fig. 1a)

Summary

Introduction

APOL1 risk alleles associate with chronic kidney disease in African Americans, but the mechanisms remain to be fully understood. These results suggest that APOL1 risk alleles activate PKR, which in turn produces an interferon response, leading to eIF2α phosphorylation to inhibit protein synthesis and cause toxic effect on cells. We demonstrated that APOL1 risk allele mRNA alone is sufficient to increase levels of phosphorylated PKR in stablytransfected cell lines (Fig. 2a).

Results

Conclusion