Impaired cellular bioenergetics caused by GBA1 depletion sensitizes neurons to calcium overload

Heterozygous mutations of the lysosomal enzyme glucocerebrosidase (GBA1) represent the major genetic risk for Parkinson's disease (PD), while homozygous GBA1 mutations cause Gaucher disease, a lysosomal storage disorder, which may involve severe neurodegeneration. We have previously demonstrated impaired autophagy and proteasomal degradation pathways and mitochondrial dysfunction in neurons from GBA1 knockout (gba1^-/-) mice. We now show that stimulation with physiological glutamate concentrations causes pathological [Ca²⁺]_c responses and delayed calcium deregulation, collapse of mitochondrial membrane potential and an irreversible fall in the ATP/ADP ratio. Mitochondrial Ca²⁺ uptake was reduced in gba1^-/- cells as was expression of the mitochondrial calcium uniporter. The rate of free radical generation was increased in gba1^-/- neurons. Behavior of gba1^+/- neurons was similar to gba1^-/- in terms of all variables, consistent with a contribution of these mechanisms to the pathogenesis of PD. These data signpost reduced bioenergetic capacity and [Ca²⁺]_c dysregulation as mechanisms driving neurodegeneration.