Skd3 (human CLPB) is a potent mitochondrial protein disaggregase that is inactivated by 3-methylglutaconic aciduria-linked mutations

  1. Ryan R Cupo
  2. James Shorter  Is a corresponding author
  1. University of Pennsylvania, United States


Cells have evolved specialized protein disaggregases to reverse toxic protein aggregation and restore protein functionality. In nonmetazoan eukaryotes, the AAA+ disaggregase Hsp78 resolubilizes and reactivates proteins in mitochondria. Curiously, metazoa lack Hsp78. Hence, whether metazoan mitochondria reactivate aggregated proteins is unknown. Here, we establish that a mitochondrial AAA+ protein, Skd3 (human CLPB), couples ATP hydrolysis to protein disaggregation and reactivation. The Skd3 ankyrin-repeat domain combines with conserved AAA+ elements to enable stand-alone disaggregase activity. A mitochondrial inner-membrane protease, PARL, removes an autoinhibitory peptide from Skd3 to greatly enhance disaggregase activity. Indeed, PARL-activated Skd3 dissolves α-synuclein fibrils connected to Parkinson's disease. Human cells lacking Skd3 exhibit reduced solubility of various mitochondrial proteins, including anti-apoptotic Hax1. Importantly, Skd3 variants linked to 3-methylglutaconic aciduria, a severe mitochondrial disorder, display diminished disaggregase activity (but not always reduced ATPase activity), which predicts disease severity. Thus, Skd3 is a potent protein disaggregase critical for human health.

Data availability

All data generated or analysed during this study are included in the manuscript and supporting files.

Article and author information

Author details

  1. Ryan R Cupo

    Biochemistry and Biophysics, University of Pennsylvania, Philadelphia, United States
    Competing interests
    The authors declare that no competing interests exist.
  2. James Shorter

    Biochemistry and Biophysics, University of Pennsylvania, Philadelphia, United States
    For correspondence
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0001-5269-8533


National Institutes of Health (R01GM099836)

  • James Shorter

National Institutes of Health (F31AG060672)

  • Ryan R Cupo

National Institutes of Health (T32GM008275)

  • Ryan R Cupo

Blavatnik Family Foundation (Blavatnik Family Foundation Fellowship)

  • Ryan R Cupo

The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.

Reviewing Editor

  1. James M Berger, Johns Hopkins University School of Medicine, United States

Publication history

  1. Received: January 19, 2020
  2. Accepted: June 22, 2020
  3. Accepted Manuscript published: June 23, 2020 (version 1)
  4. Version of Record published: July 8, 2020 (version 2)


© 2020, Cupo & Shorter

This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.


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  1. Ryan R Cupo
  2. James Shorter
Skd3 (human CLPB) is a potent mitochondrial protein disaggregase that is inactivated by 3-methylglutaconic aciduria-linked mutations
eLife 9:e55279.

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