Maria E Fernandez-Suarez

Background: Parkinson’s disease (PD) is a prevalent neurodegenerative disorder characterized by progressive motor dysfunction and broad cellular impairment, including significant disruptions in lysosomal function, lipid metabolism, and intracellular trafficking. Glycosphingolipids (GSLs), critical for various cellular processes, depend on effective lysosomal degradation. Aberrant GSL metabolism has been linked to PD pathology, and glycoprotein non-metastatic melanoma protein B (GPNMB) has emerged as a biomarker associated with lysosomal dysfunction and lipid imbalance in PD Objectives: To assess the relationship between GPNMB and GSL levels in cerebrospinal fluid (CSF) and plasma from PD patients and controls within the BioFIND cohort. We also investigated potential sex differences and associations with PD-related biomarkers such as α-synuclein Methods: GSL species and GPNMB protein levels were quantified using high-performance liquid chromatography (HPLC) and ELISA assays, respectively, in matched CSF and plasma samples from PD patients and controls Results: Levels of the paraglobosides GSL species, alpha-2,3SpG and pGb were significantly elevated in the plasma of PD patients compared to healthy controls, while levels of the ganglioside GD1a and the lacto-series GSL, Le ^b combined (GD1a + Le ^b ), were significantly reduced in PD. GPNMB levels positively correlated with several GSL species in both plasma and CSF. Plasma GSLs and GPNMB concentrations were significantly higher in females compared to males, independent of PD diagnosis. CSF GPNMB correlated positively with age and α-synuclein concentrations Interpretation: Our findings confirm that GSL metabolism is altered in PD. They also highlight significant sex-based biochemical variations in GSL and GPNMB levels, emphasizing the need for sex-specific analyses in PD biomarker research. The relationship between GSLs and GPNMB supports their potential as interconnected biomarkers of lipid pathology in PD.

BioStudies – one package for all the data supporting a study

BioStudies – one package for all the data supporting a study

BioStudies – one package for all the data supporting a study

BioStudies – one package for all the data supporting a study

Plasma membrane calcium ATPases (PMCAs) are believed to function exclusively at the plasma membrane where they expel calcium from the cytosol. We have unexpectedly identified a splice variant-dependent localisation of the PMCA isoform PMCA2 to the lysosome, where it forms an evolutionarily conserved complex with NPC1, the lysosomal membrane protein defective in the rare lysosomal storage disease Niemann-Pick disease type C (NPC). This interaction is required for lysosomal Ca ²⁺ homeostasis and implicates PMCA2 as a mediator of Ca ²⁺ uptake into lysosomes. Disruption of the NPC1-PMCA2 complex contributes to the pathophysiology of both Niemann-Pick disease type C and Parkinson’s disease, revealing an unrecognised intracellular function for PMCA2 and a shared mechanism linking lysosomal Ca ²⁺ and lipid regulation in neurodegeneration.

It is well established that lysosomal glucocerebrosidase gene (GBA) variants are a risk factor for Parkinson’s disease (PD), with increasing evidence suggesting a loss of function mechanism. One question raised by this genetic association is whether variants of genes involved in other aspects of sphingolipid metabolism are also associated with PD. Recent studies in sporadic PD have identified variants in multiple genes linked to diseases of glycosphingolipid (GSL) metabolism to be associated with PD. GSL biosynthesis is a complex pathway involving the coordinated action of multiple enzymes in the Golgi apparatus. GSL catabolism takes place in the lysosome and is dependent on the action of multiple acid hydrolases specific for certain substrates and glycan linkages. The finding that variants in multiple GSL catabolic genes are over-represented in PD in a heterozygous state highlights the importance of GSLs in the healthy brain and how lipid imbalances and lysosomal dysfunction are associated with normal ageing and neurodegenerative diseases. In this article we will explore the link between lysosomal storage disorders and PD, the GSL changes seen in both normal ageing, lysosomal storage disorders (LSDs) and PD and the mechanisms by which these changes can affect neurodegeneration.

Niemann–Pick disease type C (NPC) is a rare lysosomal storage disease caused by mutations in either theNPC1orNPC2genes. Mutations in theNPC1gene lead to the majority of clinical cases (95%); however, the function of NPC1 remains unknown. To gain further insights into the biology of NPC1, we took advantage of the homology between the human NPC1 protein and its yeast orthologue, Niemann–Pick C–related protein 1 (Ncr1). We recreated theNCR1mutant in yeast and performed screens to identify compensatory or redundant pathways that may be involved in NPC pathology, as well as proteins that were mislocalized inNCR1-deficient yeast. We also identified binding partners of the yeast Ncr1 orthologue. These screens identified several processes and pathways that may contribute to NPC pathogenesis. These included alterations in mitochondrial function, cytoskeleton organization, metal ion homeostasis, lipid trafficking, calcium signalling, and nutrient sensing. The mitochondrial and cytoskeletal abnormalities were validated in patient cells carrying mutations inNPC1, confirming their dysfunction in NPC disease.

Niemann‐Pick disease type C (NPC) and Tangier disease are genetically and clinically distinct rare inborn errors of metabolism. NPC is caused by defects in either NPC1 or NPC2; whereas Tangier disease is caused by a defect in ABCA1. Tangier disease is currently without therapy, whereas NPC can be treated with miglustat, a small molecule inhibitor of glycosphingolipid biosynthesis that slows the neurological course of the disease. When a Tangier disease patient was misdiagnosed with NPC and treated with miglustat, her symptoms improved. This prompted us to consider whether there is mechanistic convergence between these two apparently unrelated rare inherited metabolic diseases. In this study, we found that when ABCA1 is defective (Tangier disease) there is secondary inhibition of the NPC disease pathway, linking these two diseases at the level of cellular pathophysiology. In addition, this study further supports the hypothesis that miglustat, as well as other substrate reduction therapies, may be potential therapeutic agents for treating Tangier disease as fibroblasts from multiple Tangier patients were corrected by miglustat treatment.

Selective estrogen receptor modulators (SERMs) are widely prescribed drugs that alter cellular and whole-body cholesterol homeostasis. Here we evaluate the effect of SERMs on the macrophage-specific reverse cholesterol transport (M-RCT) pathway, which is mediated by HDL. Treatment of human and mouse macrophages with tamoxifen, raloxifene or toremifene induced the accumulation of cytoplasmic vesicles of acetyl-LDL-derived free cholesterol. The SERMs impaired cholesterol efflux to apolipoprotein A-I and HDL, and lowered ABCA1 and ABCG1 expression. These effects were not altered by the antiestrogen ICI 182,780 nor were they reproduced by 17β-estradiol. The treatment of mice with tamoxifen or raloxifene accelerated HDL-cholesteryl ester catabolism, thereby reducing HDL-cholesterol concentrations in serum. When [³H]cholesterol-loaded macrophages were injected into mice intraperitoneally, tamoxifen, but not raloxifene, decreased the [³H]cholesterol levels in serum, liver and feces. Both SERMs downregulated liver ABCG5 and ABCG8 protein expression, but tamoxifen reduced the capacity of HDL and plasma to promote macrophage cholesterol efflux to a greater extent than raloxifene. We conclude that SERMs interfere with intracellular cholesterol trafficking and efflux from macrophages. Tamoxifen, but not raloxifene, impair M-RCT in vivo. This effect is primarily attributable to the tamoxifen-mediated reduction of the capacity of HDL to promote cholesterol mobilization from macrophages.