Truncated mutants of beta-glucosidase 2 (GBA2) are localized in the mitochondrial matrix and cause mitochondrial fragmentation

PLoS One. 2020 Jun 3;15(6):e0233856. doi: 10.1371/journal.pone.0233856. eCollection 2020.

Abstract

The enzyme β-glucosidase 2 (GBA2) is clinically relevant because it is targeted by the drug miglustat (Zavesca®) and because it is involved in inherited diseases. Mutations in the GBA2 gene are associated with two neurological diseases on the ataxia-spasticity spectrum, hereditary spastic paraplegia 46 (SPG46) and Marinesco-Sjögren-like syndrome (MSS). To establish how GBA2 mutations give rise to neurological pathology, we have begun to investigate mutant forms of GBA2 encoded by disease-associated GBA2 alleles. Previously, we found that five GBA2 missense mutants and five C-terminally truncated mutants lacked enzyme activity. Here we have examined the cellular locations of wild-type (WT) and mutant forms of GBA2 by confocal and electron microscopy, using transfected cells. Similar to GBA2-WT, the D594H and M510Vfs*17 GBA2 mutants were located at the plasma membrane, whereas the C-terminally truncated mutants terminating after amino acids 233 and 339 (GBA2-233 and -339) were present in the mitochondrial matrix, induced mitochondrial fragmentation and loss of mitochondrial transmembrane potential. Deletional mutagenesis indicated that residues 161-200 are critical for the mitochondrial fragmentation of GBA2-233 and -339. Considering that the mitochondrial fragmentation induced by GBA2-233 and -339 is consistently accompanied by their localization to the mitochondrial matrix, our deletional analysis raises the possibility that that GBA2 residues 161-200 harbor an internal targeting sequence for transport to the mitochondrial matrix. Altogether, our work provides new insights into the behaviour of GBA2-WT and disease-associated forms of GBA2.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alleles
  • Cell Line, Tumor
  • Cell Membrane / metabolism
  • Cell Membrane / ultrastructure
  • Glucosylceramidase / genetics
  • Glucosylceramidase / metabolism*
  • Humans
  • Membrane Potential, Mitochondrial
  • Microscopy, Electron
  • Mitochondria / enzymology
  • Mitochondria / pathology*
  • Mitochondria / ultrastructure
  • Mutation
  • Spastic Paraplegia, Hereditary / genetics
  • Spinocerebellar Degenerations / genetics

Substances

  • GBA2 protein, human
  • Glucosylceramidase

Grants and funding

ACvdS received grant RGPIN/386633 from the Natural Sciences and Engineering Research Council of Canada, https://portal-portail.nserc-crsng.gc.ca/s/login.aspx; ACvdS received grant MED-DI-2017-1276 from Research Nova Scotia (previously the Nova Scotia Health Research Foundation), https://researchns.ca/; ACvdS received funding from the Dalhousie University Medical Research Development Office, https://medicine.dal.ca/research-dal-med/people/office-staff.html; ACvdS received funding from Dalhousie University Department of Pediatrics, https://medicine.dal.ca/departments/department-sites/pediatrics.html; SS received funding from Research Nova Scotia (previously the Nova Scotia Health Research Foundation), https://researchns.ca/; SS & IWK received funding from Health Centre Halifax, http://www.iwk.nshealth.ca/; SS received funding from the Dalhousie University Faculty of Graduate Studies, https://www.dal.ca/faculty/gradstudies/funding/appprocres/scholarshiprefs/nsgs.html. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.