Three-layered proteomic characterization of a novel ACTN4 mutation unravels its pathogenic potential in FSGS.

Abstract

Genetic diseases constitute the most important cause for end-stage renal disease in children and adolescents. Mutations in the ACTN4 gene, encoding the actin-binding protein α-actinin-4, are a rare cause of autosomal dominant familial focal segmental glomerulosclerosis (FSGS). Here, we report the identification of a novel, disease-causing ACTN4 mutation (p.G195D, de novo) in a sporadic case of childhood FSGS using next generation sequencing. Proteome analysis by quantitative mass spectrometry (MS) of patient-derived urinary epithelial cells indicated that ACTN4 levels were significantly decreased when compared with healthy controls. By resolving the peptide bearing the mutated residue, we could proof that the mutant protein is less abundant when compared with the wild-type protein. Further analyses revealed that the decreased stability of p.G195D is associated with increased ubiquitylation in the vicinity of the mutation site. We next defined the ACTN4 interactome, which was predominantly composed of cytoskeletal modulators and LIM domain-containing proteins. Interestingly, this entire group of proteins, including several highly specific ACTN4 interactors, was globally decreased in the patient-derived cells. Taken together, these data suggest a mechanistic link between ACTN4 instability and proteome perturbations of the ACTN4 interactome. Our findings advance the understanding of dominant effects exerted by ACTN4 mutations in FSGS. This study illustrates the potential of genomics and complementary, high-resolution proteomics analyses to study the pathogenicity of rare gene variants.

• Authors: Malte P Bartram, Sandra Habbig, Caroline Pahmeyer, Martin Höhne, Lutz T Weber, Holger Thiele, Janine Altmüller, Nina Kottoor, Andrea Wenzel, Marcus Krueger, Bernhard Schermer, Thomas Benzing, Markus M Rinschen, Bodo B Beck
• Journal: Human molecular genetics (Hum Mol Genet) Vol. 25 Issue 6 Pg. 1152-64 (Mar 15 2016) ISSN: 1460-2083 [Electronic] England
• PMID: 26740551 (Publication Type: Case Reports, Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please email: [email protected].

Chemical References

• ACTN4 protein, human
• Actins
• Microfilament Proteins
• Actinin

Topics

• Actinin (genetics, metabolism)
• Actins (metabolism)
• Adolescent
• Amino Acid Sequence
• Cytoskeleton (metabolism)
• Female
• Glomerulosclerosis, Focal Segmental (genetics, metabolism)
• High-Throughput Nucleotide Sequencing
• Humans
• Kidney Failure, Chronic (genetics, metabolism)
• Microfilament Proteins (metabolism)
• Proteomics