Mitochondrial dysfunction and mitophagy defect triggered by heterozygous GBA mutations.

ABSTRACT

Heterozygous mutations in GBA, the gene encoding the lysosomal enzyme glucosylceramidase beta/ß-glucocerebrosidase, comprise the most common genetic risk factor for Parkinson disease (PD), but the mechanisms underlying this association remain unclear. Here, we show that in GbaL444P/WT knockin mice, the L444P heterozygous Gba mutation triggers mitochondrial dysfunction by inhibiting autophagy and mitochondrial priming, two steps critical for the selective removal of dysfunctional mitochondria by autophagy, a process known as mitophagy. In SHSY-5Y neuroblastoma cells, the overexpression of L444P GBA impeded mitochondrial priming and autophagy induction when endogenous lysosomal GBA activity remained intact. By contrast, genetic depletion of GBA inhibited lysosomal clearance of autophagic cargo. The link between heterozygous GBA mutations and impaired mitophagy was corroborated in postmortem brain tissue from PD patients carrying heterozygous GBA mutations, where we found increased mitochondrial content, mitochondria oxidative stress and impaired autophagy. Our findings thus suggest a mechanistic basis for mitochondrial dysfunction associated with GBA heterozygous mutations. Abbreviations AMBRA1 autophagy/beclin 1 regulator 1; BECN1 beclin 1, autophagy related; BNIP3L/Nix BCL2/adenovirus E1B interacting protein 3-like; CCCP carbonyl cyanide 3-chloroyphenylhydrazone; CYCS cytochrome c, somatic; DNM1L/DRP1 dynamin 1-like; ER endoplasmic reticulum; GBA glucosylceramidase beta; GBA-PD Parkinson disease with heterozygous GBA mutations; GD Gaucher disease; GFP green fluorescent protein; LC3B microtubule-associated protein 1 light chain 3 beta; LC3B-II lipidated form of microtubule-associated protein 1 light chain 3 beta; MitoGreen MitoTracker Green; MitoRed MitoTracker Red; MMP mitochondrial membrane potential; MTOR mechanistic target of rapamycin kinase; MYC MYC proto-oncogene, bHLH transcription factor; NBR1 NBR1, autophagy cargo receptor; Non-GBA-PD Parkinson disease without GBA mutations; PD Parkinson disease; PINK1 PTEN induced putative kinase 1; PRKN/PARK2 parkin RBR E3 ubiquitin protein ligase; RFP red fluorescent protein; ROS reactive oxygen species; SNCA synuclein alpha; SQSTM1/p62 sequestosome 1; TIMM23 translocase of inner mitochondrial membrane 23; TOMM20 translocase of outer mitochondrial membrane 20; VDAC1/Porin voltage dependent anion channel 1; WT wild type.