Daily regulation of glucocerebrosidase activity and impact of fixed-time rotarod training in a mouse model of Gba1-associated Parkinson's disease

Introduction Mutations in the glucocerebrosidase (GBA1) gene are a major genetic risk factor for Parkinson's disease (PD) and result in dysfunctional glucocerebrosidase (GCase), the lysosomal enzyme responsible for cleaving glucosylceramide into glucose and ceramide. The pathogenic L444P variant disrupts the enzyme structure and activity, leading to lysosomal accumulation of glucosylceramide and ultimately impairing the clearance of monomeric alpha-synuclein (alpha-syn). Given the functional crosstalk among lysosomal homeostasis, the molecular circadian clock, and physical activity, we investigated whether GCase activity exhibits daily rhythmicity, and can be modulated by daily, fixed-time rotarod activity in healthy and Gba1-mutant mice.Methods C57BL/6J healthy controls and Gba1-mutant PD model mice were housed under a 12 h light/dark cycle, and blood samples were collected at four Zeitgeber times (ZT2, ZT8, ZT14, and ZT20), with and without daily, fixed-time rotarod training. A fluorometric assay was performed on plasma samples to investigate the daily pattern of GCase activity.Results Our results showed that rotarod performance was influenced by genotype-dependent vulnerabilities and by daily, fixed-time physical activity, with overall better performance during the dark-phase training. The fluorometric assay revealed that GCase activity shows a ZT-dependent daily pattern in healthy mice, whereas this pattern was disrupted in Gba1-mutant PD models and partially rescued by timed physical activity.Discussion Overall, both the time of day and daily fixed-time physical activity influenced GCase regulation. Our findings reveal a functional interplay between daily biological timing and lysosomal enzyme regulation, suggesting that optimizing drug dosing and timing of administration may improve the efficacy of GCase-targeted treatments.