Multi-omics-based phenotyping of AFG3L2-mutant lymphoblasts determines key factors of a pathophysiological interplay between mitochondrial vulnerability and neurodegeneration in spastic ataxia type 5

Frontiers in Molecular Neuroscience, vol. 18, pp. 1548255

Abstract

Mitochondrial integrity is fundamental to cellular function, upheld by a network of proteases that regulate proteostasis and mitochondrial dynamics. Among these proteases, AFG3L2 is critical due to its roles in maintaining mitochondrial homeostasis, regulating mitochondrial protein quality, and facilitating mitochondrial biogenesis. Mutations in AFG3L2 are implicated in a spectrum of diseases, including spinocerebellar ataxia type 28 (SCA28) and spastic ataxia 5 (SPAX5), as well as other systemic conditions. This study employs a multi-omics approach to investigate the biochemical impact of AFG3L2 mutations in immortalized lymphoblastoid cell lines derived from a patient with biallelic variants leading to spastic ataxia (SPAX5). Our proteomic analysis revealed AFG3L2 impairment, with significant dysregulation of proteins critical for mitochondrial function, cytoskeletal integrity, and cellular metabolism. Specifically, disruptions were observed in mitochondrial dynamics and calcium homeostasis, alongside downregulation of key proteins like COX11, a copper chaperone for complex IV assembly, and NFU1, an iron-sulfur cluster protein linked to spastic paraparesis and infection-related worsening. Lipidomic analysis highlighted substantial alterations in lipid composition, with significant decreases in sphingomyelins, phosphatidylethanolamine, and phosphatidylcholine, reflecting disruptions in lipid metabolism and membrane integrity. Metabolomic profiling did not reveal any significant findings. Our comprehensive investigation into loss of functional AFG3L2 elucidates a pathophysiology extending beyond mitochondrial proteostasis, implicating a wide array of cellular processes. The findings reveal substantial cellular disturbances at multiple levels, contributing to neurodegeneration through disrupted mitochondrial respiratory chain, calcium homeostasis, cytoskeletal integrity, and altered lipid homeostasis. This study underscores the complexity of SPAX5 pathophysiology and the importance of multi-omics approaches in developing effective strategies to address the impact of loss of functional AFG3L2. Our data also highlight the value of immortalized lymphoblastoid cells as a tool for pre-clinical testing and research, offering a detailed biochemical fingerprint that enhances our understanding of SPAX5 and identifies potential areas for further investigation.

Authors 12

1. Menekse Oeztuerk

   Düsseldorf University Hospital · BG University Hospital Bergmannsheil Bochum · Heinrich Heine University Düsseldorf · Ruhr University Bochum

   Affiliation as printed

   Department of Neurology, BG-University Hospital Bergmannsheil, Ruhr University Bochum, Bochum, Germany

   Department of Neurology, Medical Faculty and University Hospital Düsseldorf, Heinrich Heine University, Düsseldorf, Germany

   Heimer Institute for Muscle Research, BG-University Hospital Bergmannsheil, Bochum, Germany

2. Diran Agaid Herebian

   Düsseldorf University Hospital · Heinrich Heine University Düsseldorf

   Affiliation as printed

   Department of General Pediatrics, Neonatology and Pediatric Cardiology, Medical Faculty and University Hospital Düsseldorf, Heinrich Heine University, Düsseldorf, Germany

3. Kale Dipali

   Leibniz Institute for Analytical Sciences - ISAS

   Affiliation as printed

   Leibniz-Institut für Analytische Wissenschaften -ISAS- e.V., Dortmund, Germany

4. Andreas Hentschel

   Leibniz Institute for Analytical Sciences - ISAS

   Affiliation as printed

   Leibniz-Institut für Analytische Wissenschaften -ISAS- e.V., Dortmund, Germany

5. Nina Rademacher

   University of Duisburg-Essen

   Affiliation as printed

   Department of Pediatric Neurology, Centre for Neuromuscular Disorders, Centre for Translational Neuro- and Behavioral Sciences, University Duisburg-Essen, Essen, Germany

6. Florian Kraft Aachen Institute for Human Genetics and Genomic Medicine Medical Faculty

   Universitätsklinikum Aachen · RWTH Aachen University

   Affiliation as printed

   Institute for Human Genetics and Genomic Medicine, Medical Faculty, Rheinisch-Westfälische Technische Hochschule Aachen University Hospital, Aachen, Germany

7. Rita Horváth

   University of Cambridge

   Affiliation as printed

   Department of Clinical Neurosciences, University of Cambridge, Cambridge, United Kingdom

8. Felix Distelmaier

   Düsseldorf University Hospital · Heinrich Heine University Düsseldorf

   Affiliation as printed

   Department of General Pediatrics, Neonatology and Pediatric Cardiology, Medical Faculty and University Hospital Düsseldorf, Heinrich Heine University, Düsseldorf, Germany

9. Sven Guenther Meuth

   Düsseldorf University Hospital · Heinrich Heine University Düsseldorf

   Affiliation as printed

   Department of Neurology, Medical Faculty and University Hospital Düsseldorf, Heinrich Heine University, Düsseldorf, Germany

10. Tobias Ruck

    Düsseldorf University Hospital · BG University Hospital Bergmannsheil Bochum · Heinrich Heine University Düsseldorf · Ruhr University Bochum

    Affiliation as printed

    Department of Neurology, BG-University Hospital Bergmannsheil, Ruhr University Bochum, Bochum, Germany

    Department of Neurology, Medical Faculty and University Hospital Düsseldorf, Heinrich Heine University, Düsseldorf, Germany

    Heimer Institute for Muscle Research, BG-University Hospital Bergmannsheil, Bochum, Germany

11. Ulrike Schara

    University of Duisburg-Essen

    Affiliation as printed

    Department of Pediatric Neurology, Centre for Neuromuscular Disorders, Centre for Translational Neuro- and Behavioral Sciences, University Duisburg-Essen, Essen, Germany

12. Andreas Roos corresponding

    Children's Hospital of Eastern Ontario · Düsseldorf University Hospital · Heinrich Heine University Düsseldorf · University of Duisburg-Essen

    Affiliation as printed

    Brain and Mind Research Institute, Children's Hospital of Eastern Ontario Research Institute, Ottawa, ON, Canada

    Department of Neurology, Medical Faculty and University Hospital Düsseldorf, Heinrich Heine University, Düsseldorf, Germany

    Department of Pediatric Neurology, Centre for Neuromuscular Disorders, Centre for Translational Neuro- and Behavioral Sciences, University Duisburg-Essen, Essen, Germany