Kidney Week

Abstract: SA-PO602

KEOPS Complex Dysfunction Causes Nephrotic Syndrome by Impairing Protein Biosynthesis and by Inducing ER Stress

Session Information

• Noncystic Mendelian Diseases
  November 04, 2017 | Location: Hall H, Morial Convention Center
  Abstract Time: 10:00 AM - 10:00 AM

Category: Genetic Diseases of the Kidney

• 802 Non-Cystic Mendelian Diseases

Authors

• Braun, Daniela A., Boston Children's Hospital, HMS, Boston, Massachusetts, United States

Daniela A. Braun,

• Rao, Jia, Boston Children's Hospital, HMS, Boston, Massachusetts, United States

Jia Rao,

• Mollet, Geraldine, Inserm U1163, Paris, France

Geraldine Mollet,

• Schapiro, David, Boston Children's Hospital, HMS, Boston, Massachusetts, United States

David Schapiro,

• Tan, Weizhen, Boston Children's Hospital, HMS, Boston, Massachusetts, United States

Weizhen Tan,

• Hu, Jennifer, MIT, Cambridge, Massachusetts, United States

Jennifer Hu,

• Dedon, Peter, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States

Peter Dedon,

• Van tilbeurgh, Herman, Université Paris Sud CNRS UMR9198, Orsay, France

Herman Van tilbeurgh,

• Zenker, Martin, University Hospital Magdeburg, Magdeburg, Germany

Martin Zenker,

• Antignac, Corinne, Imagine Institute, Paris, France

Corinne Antignac,

• Hildebrandt, Friedhelm, Boston Children's Hospital, HMS, Boston, Massachusetts, United States

Friedhelm Hildebrandt,

Background

Steroid resistant nephrotic syndrome (SRNS), a disease of glomerular podocytes, is a frequent cause of end-stage renal disease in children and young adults. Identification of single-gene causes of SRNS has contributed to a better understanding of podocyte biology. In 32 unrelated families, we recently identified mutations in genes encoding the evolutionarily highly conserved KEOPS complex (LAGE3, OSGEP, TP53RK, and TPRKB) as novel monogenic cause of SRNS and microcephaly. The KEOPS complex catalyzes an essential posttranscriptional modification of tRNA.

Methods

To characterize the pathogenesis of the four newly recognized human disease genes, we measured tRNA modifications by mass-spectrometry, assessed protein biosynthesis in vitro, and performed immunoblotting of ER stress marker proteins.

Results

We show that shRNA knockdown of OSGEP or TPRKB in human podocytes reduced the cellular content of t6A, a specific posttranscriptional modification of tRNA. Using a yeast system, we demonstrate that human mutations of OSGEP, identified in patients with SRNS, alter the t6A-related catalytic activity of the encoded protein. We furthermore found that knockdown of OSGEP, TP53RK, or TPRKB inhibited de novo protein biosynthesis and activated the unfolded protein response in human podocytes, thus indicating the presence of ER stress. Knockdown of either of the three genes induced apoptosis in human podocytes, suggesting a central role in the pathogenesis of SRNS in patients with mutations in KEOPS complex genes.

Conclusion

Studying the pathogenesis of four newly recognized monogenic causes of SRNS, we generate evidence that altered function of the KEOPS complex results in podocyte damage by impairing the rate and the accuracy of de novo protein biosynthesis.

Funding

• NIDDK Support