Mutations in PLA2G6 impair ER–mitochondria contacts and ceramide homeostasis via GRP75 in Parkinson’s disease

Background Loss-of-function mutations in PLA2G6 cause mitochondrial abnormalities that contribute to Parkinson’s disease (PD), yet the precise mechanisms remain elusive. Methods We combined genetic, cellular, and pharmacological approaches to investigate the role of PLA2G6 in Parkinson’s disease. The PLA2G6 D331Y knock-in mouse model, PLA2G6 knockout cell lines, and patient-derived dopaminergic neurons were used to assess neuronal and mitochondrial phenotypes. ER–mitochondria contacts and protein interactions were examined by Focused Ion Beam-Scanning Electron Microscope, subcellular fractionation, and biochemical assays. Lipidomic profiling and immunofluorescence were applied to quantified ceramide distribution, while mitochondrial respiration, Ca²⁺ flux, and oxidative stress were evaluated by functional assays. Ceramide-lowering drugs and GRP75 overexpression were tested for therapeutic rescue in vitro and in vivo . Results Our data show that PLA2G6 localized to mitochondria-associated membranes (MAMs) and interacted with the IP3R–GRP75–VDAC1 tether. Loss of PLA2G6 reduced GRP75 levels, disrupted ER–mitochondria contacts, and weakened IP3R–GRP75–VDAC1 interactions, leading to impaired Ca²⁺ transfer and mitochondrial dysfunction. PLA2G6 deficiency caused caused pronounced accumulation of mitochondrial ceramides, particularly C16 ceramide. GRP75 was identified as a ceramide-binding protein regulating lipid turnover in addition to Ca²⁺ transfer. Restoring GRP75 or pharmacologically lowering ceramides rescues mitochondrial function in cells and alleviates motor deficits and dopaminergic neuron loss in PLA2G6 mutant mice. GRP75 reduction was also observed in peripheral blood cells and substantia nigra tissues from PD patients, supporting its clinical relevance. Conclusions Loss of PLA2G6 destabilizes GRP75, leading to disrupted MAMs and mitochondrial ceramide overload, which drive neurodegeneration. These findings support a PLA2G6–GRP75–ceramide pathway that integrates organelle communication, lipid metabolism, and mitochondrial integrity, highlighting ceramide modulation or GRP75 restoration as therapeutic strategies for PLA2G6 -linked and sporadic PD.