bims-tofagi Biomed News
on Mitophagy
Issue of 2024‒08‒04
two papers selected by
Michele Frison, University of Cambridge and Aitor Martínez Zarate, Euskal Herriko Unibertsitatea
  1. The parkin V380L variant is a genetic modifier of Machado-Joseph disease with impact on mitophagy.
  2. Capturing the catalytic intermediates of parkin ubiquitination.
  1. Acta Neuropathol. 2024 Aug 01. 148(1): 14
    The parkin V380L variant is a genetic modifier of Machado-Joseph disease with impact on mitophagy.
    EUROSCA Network
      Machado-Joseph disease (MJD) is an autosomal dominant neurodegenerative spinocerebellar ataxia caused by a polyglutamine-coding CAG repeat expansion in the ATXN3 gene. While the CAG length correlates negatively with the age at onset, it accounts for approximately 50% of its variability only. Despite larger efforts in identifying contributing genetic factors, candidate genes with a robust and plausible impact on the molecular pathogenesis of MJD are scarce. Therefore, we analysed missense single nucleotide polymorphism variants in the PRKN gene encoding the Parkinson's disease-associated E3 ubiquitin ligase parkin, which is a well-described interaction partner of the MJD protein ataxin-3, a deubiquitinase. By performing a correlation analysis in the to-date largest MJD cohort of more than 900 individuals, we identified the V380L variant as a relevant factor, decreasing the age at onset by 3 years in homozygous carriers. Functional analysis in an MJD cell model demonstrated that parkin V380L did not modulate soluble or aggregate levels of ataxin-3 but reduced the interaction of the two proteins. Moreover, the presence of parkin V380L interfered with the execution of mitophagy-the autophagic removal of surplus or damaged mitochondria-thereby compromising cell viability. In summary, we identified the V380L variant in parkin as a genetic modifier of MJD, with negative repercussions on its molecular pathogenesis and disease age at onset.
    Keywords:   PRKN ; Aggregation; Polyglutamine disease; SCA3; SNP; Spinocerebellar ataxia type 3
    DOI:  https://doi.org/10.1007/s00401-024-02762-6
  2. Proc Natl Acad Sci U S A. 2024 Aug 06. 121(32): e2403114121
    Capturing the catalytic intermediates of parkin ubiquitination.
    Elizabeth M Connelly, Anne C Rintala-Dempsey, Mehmet Gundogdu, E Aisha Freeman, Joanna Koszela, Jacob D Aguirre, Grace Zhu, Outi Kämäräinen, Roya Tadayon, Helen Walden, Gary S Shaw.
      Parkin is an E3 ubiquitin ligase implicated in early-onset forms of Parkinson's disease. It catalyzes a transthiolation reaction by accepting ubiquitin (Ub) from an E2 conjugating enzyme, forming a short-lived thioester intermediate, and transfers Ub to mitochondrial membrane substrates to signal mitophagy. A major impediment to the development of Parkinsonism therapeutics is the lack of structural and mechanistic detail for the essential, short-lived transthiolation intermediate. It is not known how Ub is recognized by the catalytic Rcat domain in parkin that enables Ub transfer from an E2~Ub conjugate to the catalytic site and the structure of the transthiolation complex is undetermined. Here, we capture the catalytic intermediate for the Rcat domain of parkin in complex with ubiquitin (Rcat-Ub) and determine its structure using NMR-based chemical shift perturbation experiments. We show that a previously unidentified α-helical region near the Rcat domain is unmasked as a recognition motif for Ub and guides the C-terminus of Ub toward the parkin catalytic site. Further, we apply a combination of guided AlphaFold modeling, chemical cross-linking, and single turnover assays to establish and validate a model of full-length parkin in complex with UbcH7, its donor Ub, and phosphoubiquitin, trapped in the process of transthiolation. Identification of this catalytic intermediate and orientation of Ub with respect to the Rcat domain provides important structural insights into Ub transfer by this E3 ligase and explains how the previously enigmatic Parkinson's pathogenic mutation T415N alters parkin activity.
    Keywords:  NMR; Parkinson’s disease; catalysis; parkin; protein structure
    DOI:  https://doi.org/10.1073/pnas.2403114121
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