The lysosomal β-glucocerebrosidase strikes mitochondria: implications for Parkinson's therapeutics

Abstract

Parkinson's disease (PD) is a neurodegenerative disorder primarily known for typical motor features that arise due to the loss of dopaminergic neurons in the substantia nigra. However, the precise molecular etiology of the disease is still unclear. Several cellular pathways have been linked to PD, including the autophagy-lysosome pathway (ALP), α-synuclein (α-syn) aggregation, and mitochondrial function. Interestingly, the mechanistic link between GBA1, the gene that encodes for lysosomal β-glucocerebrosidase (GCase), and PD lies in the interplay between GCase functions in the lysosome and mitochondria. GCase mutations alter mitochondria-lysosome contact sites. In the lysosome, reduced GCase activity leads to glycosphingolipid buildup, disrupting lysosomal function and autophagy, thereby triggering α-syn accumulation. Additionally, α-syn aggregates reduce GCase activity, creating a self-perpetuating cycle of lysosomal dysfunction and α-syn accumulation. GCase can also be imported into the mitochondria, where it promotes the integrity and function of mitochondrial complex I. Thus, GCase mutations that impair its normal function increase oxidative stress in mitochondria, the compartment where dopamine is oxidized. In turn, the accumulation of oxidized dopamine-adducts further impairs GCase activity, creating a second cycle of GCase dysfunction. The oxidative state triggered by GCase dysfunction can also induce mitochondrial DNA damage which, in turn, can cause dopaminergic cell death. In this review, we highlight the pivotal role of GCase in PD pathogenesis and discuss promising examples of GCase-based therapeutics such as gene and enzyme replacement therapies, small molecule chaperones, and substrate reduction therapies, among others, as potential therapeutic interventions.

Keywords: Gaucher’s disease; Parkinson’s disease; lysosome; mitochondria; neurodegeneration; therapeutics.