The relationship between depletion of brain GM1 ganglioside and Parkinson's disease

Alpha-Synuclein and GM1 Ganglioside Co-Localize in Neuronal Cytosol Leading to Inverse Interaction-Relevance to Parkinson's Disease

Research on GM1 ganglioside and its neuroprotective role in Parkinson's disease (PD), particularly in mitigating the aggregation of α-Synuclein (aSyn), is well established across various model organisms. This essential molecule, GM1, is intimately linked to preventing aSyn aggregation, and its deficiency is believed to play a key role in the initiation of PD. In our current study, we attempted to shed light on the cytosolic interactions between GM1 and aSyn based on previous reports demonstrating gangliosides and monomeric aSyn to be present in neuronal cytosol. Native-PAGE and Western blot analysis of neuronal cytosol from mouse brains demonstrated the presence of both GM1 and monomeric aSyn in the neuronal cytosol of normal mouse brain. To demonstrate that an adequate level of GM1 prevents the aggregation of aSyn, we used NG108-15 and SH-SY5Y cells with and without treatment of 1-phenyl-2-palmitoyl-3-morpholino-1-propanol (PPMP), which inhibits the synthesis/expression of GM1. Cells treated with PPMP to reduce GM1 expression showed a significant increase in the formation of aggregated aSyn compared to untreated cells. We thus demonstrated that sufficient GM1 prevents the aggregation of aSyn. For this to occur, aSyn and GM1 must show proximity within the neuron. The present study provides evidence for such co-localization in neuronal cytosol, which also facilitates the inverse interaction revealed in studies with the two cell types above. This adds to the explanation of how GM1 prevents the aggregation of aSyn and onset of Parkinson's disease.

Glycosyltransferase 8 domain-containing protein 1 (GLT8D1) is a UDP-dependent galactosyltransferase

Glycosyltransferases (GTs) are enzymes that catalyze the formation of glycosidic bonds and hundreds of GTs have been identified so far in humans. Glycosyltransferase 8 domain-containing protein 1 (GLT8D1) has been associated with central nervous system diseases and cancer. However, evidence on its enzymatic properties, including its substrates, has been scarcely described. In this paper, we have produced and purified recombinant secretory GLT8D1. The enzyme was found to be N-glycosylated. Differential scanning fluorimetry was employed to analyze the stabilization of GLT8D1 by Mn2+ and nucleotides, revealing UDP as the most stabilizing nucleotide scaffold. GLT8D1 displayed glycosyltransferase activity from UDP-galactose onto N-acetylgalactosamine but with a low efficiency. Modeling of the structure revealed similarities with other GT-A fold enzymes in CAZy family GT8 and glycosyltransferases in other families with galactosyl-, glucosyl-, and xylosyltransferase activities, each with retaining catalytic mechanisms. Our study provides novel structural and functional insights into the properties of GLT8D1 with implications in pathological processes.

Astaxanthin alleviates ganglioside metabolism disorder in the cortex of Alzheimer's disease mice

The present study analyzed the amelioration effect and mechanism of two kinds of astaxanthin (AST), including free-AST (F-AST) and docosahexaenoic acid-acylated AST monoester (AST-DHA), on ganglioside (GLS) metabolism in the cortex of APP/PS1 mice using the LC-MS strategy in combination with molecular biology. Water maze and immunohistochemical experiments demonstrated that AST significantly improved the cognitive level of APP/PS1 mice and reduced Aβ deposition in the cortex. After the dietary intake of AST, the composition and level of 84 GLS molecular species in the mouse cortex were determined using the LC-MS strategy. The results showed that the total GLS was reduced, most complex GLS was decreased, and simple GLS (GM3 and GM1a) was increased in the APP/PS1 mouse cortex. Notably, F-AST mainly regulated complex GLS (p < 0.001), whereas AST-DHA primarily reacted with simple GLS (p < 0.001). OAc-GQ1a(38:1), OAc-GQ1a(36:1), GD1a(36:1), and GM3(38:1) decreased 3.73, 2.31, and 2.29-fold and increased 3.54-fold, respectively, and were identified as potential AD biomarkers in the cortices of APP/PS1 mice. Additionally, the AST diet significantly upregulated the mRNA expression of GLS synthesizing genes (st3gal5, st8sia1, b3galt4, st3fal2, and soat) and siae (p < 0.05) and down-regulated that of the GLS catabolizing gene hexa (p < 0.01). In conclusion, improving GLS homeostasis in the AD mouse cortex might be a critical pathway to explain the AD-preventing effect of AST.

Ganglioside GM1 and the Central Nervous System

GM1 is one of the major glycosphingolipids (GSLs) on the cell surface in the central nervous system (CNS). Its expression level, distribution pattern, and lipid composition are dependent upon cell and tissue type, developmental stage, and disease state, which suggests a potentially broad spectrum of functions of GM1 in various neurological and neuropathological processes. The major focus of this review is the roles that GM1 plays in the development and activities of brains, such as cell differentiation, neuritogenesis, neuroregeneration, signal transducing, memory, and cognition, as well as the molecular basis and mechanisms for these functions. Overall, GM1 is protective for the CNS. Additionally, this review has also examined the relationships between GM1 and neurological disorders, such as Alzheimer's disease, Parkinson's disease, GM1 gangliosidosis, Huntington's disease, epilepsy and seizure, amyotrophic lateral sclerosis, depression, alcohol dependence, etc., and the functional roles and therapeutic applications of GM1 in these disorders. Finally, current obstacles that hinder more in-depth investigations and understanding of GM1 and the future directions in this field are discussed.

GM1 Ganglioside as a Disease-Modifying Therapeutic for Parkinson's Disease: A Multi-Functional Glycosphingolipid That Targets Multiple Parkinson's Disease-Relevant Pathogenic Mechanisms

Parkinson's disease (PD) is a progressive neurodegenerative disorder affecting millions of patients worldwide. Many therapeutics are available for treating PD symptoms but there is no disease-modifying therapeutic that has been unequivocally shown to slow or stop the progression of the disease. There are several factors contributing to the failure of many putative disease-modifying agents in clinical trials and these include the choice of patients and clinical trial designs for disease modification trials. Perhaps more important, however, is the choice of therapeutic, which for the most part, has not taken into account the multiple and complex pathogenic mechanisms and processes involved in PD. This paper discusses some of the factors contributing to the lack of success in PD disease-modification trials, which have mostly investigated therapeutics with a singular mechanism of action directed at one of the many PD pathogenic processes, and suggests that an alternative strategy for success may be to employ multi-functional therapeutics that target multiple PD-relevant pathogenic mechanisms. Evidence is presented that the multi-functional glycosphingolipid GM1 ganglioside may be just such a therapeutic.