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Accumulation of the protein α-synuclein into insoluble intracellular deposits termed Lewy bodies (LBs) is the characteristic neuropathological feature of LB diseases, such as Parkinson’s disease (PD), Parkinson’s disease dementia (PDD) and dementia with LB (DLB). α-Synuclein aggregation is thought to be a critical pathogenic event in the aetiology of LB disease, based on genetic analyses, fundamental studies using model systems, and the observation of LB pathology in post-mortem tissue. However, some monogenic disorders not traditionally characterised as synucleinopathies, such as lysosomal storage disorders, iron storage disorders and mitochondrial diseases, appear disproportionately vulnerable to the deposition of LBs, perhaps suggesting the process of LB formation may be a result of processes perturbed as a result of these conditions. The present review discusses biological pathways common to monogenic disorders associated with LB formation, identifying catabolic processes, particularly related to lipid homeostasis, autophagy and mitochondrial function, as processes that could contribute to LB formation. These findings are discussed in the context of known mediators of α-synuclein aggregation, highlighting the potential influence of impairments to these processes in the aetiology of LB formation.

The lysosomal storage disorder Fabry disease is characterized by a deficiency of the lysosomal enzyme α-Galactosidase A. The observation that missense variants in the encoding GLA gene often lead to structural destabilization, endoplasmic reticulum retention and proteasomal degradation of the misfolded, but otherwise catalytically functional enzyme has resulted in the exploration of alternative therapeutic approaches. In this context, we have investigated proteostasis regulators (PRs) for their potential to increase cellular enzyme activity, and to reduce the disease-specific accumulation of the biomarker globotriaosylsphingosine in patient-derived cell culture. The PRs also acted synergistically with the clinically approved 1-deoxygalactonojirimycine, demonstrating the potential of combination treatment in a therapeutic application. Extensive characterization of the effective PRs revealed inhibition of the proteasome and elevation of GLA gene expression as paramount effects. Further analysis of transcriptional patterns of the PRs exposed a variety of genes involved in proteostasis as potential modulators. We propose that addressing proteostasis is an effective approach to discover new therapeutic targets for diseases involving folding and trafficking-deficient protein mutants.

In the last decades, lysosomes and mitochondria were considered distinct and physically separated organelles involved in different cellular functions. While lysosomes were thought to exclusively be the rubbish dump of the cell involved in the degradation of proteins and other cell compartments, mitochondria were considered solely involved in the oxidation of energy substrate to get ATP, together with other minor duties. Nowadays, our view of these organelles is profoundly changed since studies demonstrated that mitochondria and lysosome are mutually functional, maintaining proper cell homeostasis. Furthermore, the onset of neurodegenerative diseases (i.e., Parkinson's disease, Alzheimer's disease, lysosomal storage disorders, and amyotrophic lateral sclerosis) is tightly linked to mutations in mitochondrial and lysosomal regulators. In this context, mitochondrial dysfunction leads to lysosomal impairment and buildup of autophagy by-products, whereas lysosomal imperfections trigger functional and morphological mitochondrial defects. Here, we provide an updated overview covering recent findings about mitochondria and lysosomal interaction in physiology and pathophysiology, focusing the attention on the molecular mechanism that control their interdependence.