Ganglioside GM1 Research Articles

ToF-SIMS imaging reveals changes in tumor cell lipids during metastatic progression of melanoma.

Most melanomas progress from radial to vertical growth phase before spreading locoregionally and distally. Much is still unknown about the metabolic changes in the tumor cells and their microenvironment during this metastatic progression. We aimed to gain new insight into the molecular characteristics of melanoma in regard to spatial lipidomics to deliver new knowledge regarding tumor metastatic progression. We included 10 fresh tumor samples from 10 patients including two insitu melanomas, two invasive primary melanomas, and six metastatic melanomas (four in-transit metastases and two distant metastases). In addition, we analyzed four healthy skin controls from the same patients. Time-of-flight imaging secondary ion mass spectrometry (ToF-SIMS) enabled detailed spatial-lipidomics that could be directly correlated with conventional histopathological analysis of consecutive H&E-stained tissue sections. Significant differences in the lipid profiles were found in primary compared to metastatic melanomas, notably an increase in phosphatidylethanolamine lipids relative to phosphatidylinositol lipids and an increase in GM3 gangliosides in the metastatic samples. Furthermore, analysis of the data from in transit versus distant metastases samples highlighted that specific phospholipids, and a difference in the long versus shorter chain GM3 gangliosides, discriminated the metastatic routes. Further studies are warranted to verify these preliminary findings. Lipidomic changes could serve as a novel biomarker for tumor progression and even serve as a target for novel treatments. Furthermore, analyzing the lipid profiles could help to differentiate between primary and metastatic melanomas in challenging cases.

Evidence of Lysosomal β-Hexosaminidase Enzymatic Activity Associated with Extracellular Vesicles: Potential Applications for the Correction of Sandhoff Disease.

Extracellular vesicles (EVs) can be isolated from biological fluids and cell culture medium. Their nanometric dimension, relative stability, and biocompatibility have raised considerable interest for their therapeutic use as delivery vehicles of macromolecules, namely nucleic acids and proteins. Deficiency in lysosomal enzymes and associated proteins is at the basis of a group of genetic diseases known as lysosomal storage disorders (LSDs), characterized by the accumulation of undigested substrates into lysosomes. Among them, GM2 gangliosidoses are due to a deficiency in the activity of lysosomal enzyme β-hexosaminidase, leading to the accumulation of the GM2 ganglioside and severe neurological symptoms. Current therapeutic approaches, including enzyme replacement therapy (ERT), have proven unable to significantly treat these conditions. Here, we provide evidence that the lysosomal β-hexosaminidase enzyme is associated with EVs released by HEK cells and that the EV-associated activity can be increased by overexpressing the α-subunit of β-hexosaminidase. The delivery of EVs to β-hexosaminidase-deficient fibroblasts results in a partial cross-correction of the enzymatic defect. Overall findings indicate that EVs could be a source of β-hexosaminidase that is potentially exploitable for developing therapeutic approaches for currently untreatable LSDs.

Integrative Single-Plaque Analysis Reveals Signature Aβ and Lipid Profiles in the Alzheimer's Brain.

Cerebral accumulation of amyloid-β (Aβ) initiates molecular and cellular cascades that lead to Alzheimer's disease (AD). However, amyloid deposition does not invariably lead to dementia. Amyloid-positive but cognitively unaffected (AP-CU) individuals present widespread amyloid pathology, suggesting that molecular signatures more complex than the total amyloid burden are required to better differentiate AD from AP-CU cases. Motivated by the essential role of Aβ and the key lipid involvement in AD pathogenesis, we applied multimodal mass spectrometry imaging (MSI) and machine learning (ML) to investigate amyloid plaque heterogeneity, regarding Aβ and lipid composition, in AP-CU versus AD brain samples at the single-plaque level. Instead of focusing on a population mean, our analytical approach allowed the investigation of large populations of plaques at the single-plaque level. We found that different (sub)populations of amyloid plaques, differing in Aβ and lipid composition, coexist in the brain samples studied. The integration of MSI data with ML-based feature extraction further revealed that plaque-associated gangliosides GM2 and GM1, as well as Aβ1-38, but not Aβ1-42, are relevant differentiators between the investigated pathologies. The pinpointed differences may guide further fundamental research investigating the role of amyloid plaque heterogeneity in AD pathogenesis/progression and may provide molecular clues for further development of emerging immunotherapies to effectively target toxic amyloid assemblies in AD therapy. Our study exemplifies how an integrative analytical strategy facilitates the unraveling of complex biochemical phenomena, advancing our understanding of AD from an analytical perspective and offering potential avenues for the refinement of diagnostic tools.

Automated Machine Learning and Explainable AI (AutoML-XAI) for Metabolomics: Improving Cancer Diagnostics.

Metabolomics generates complex data necessitating advanced computational methods for generating biological insight. While machine learning (ML) is promising, the challenges of selecting the best algorithms and tuning hyperparameters, particularly for nonexperts, remain. Automated machine learning (AutoML) can streamline this process; however, the issue of interpretability could persist. This research introduces a unified pipeline that combines AutoML with explainable AI (XAI) techniques to optimize metabolomics analysis. We tested our approach on two data sets: renal cell carcinoma (RCC) urine metabolomics and ovarian cancer (OC) serum metabolomics. AutoML, using Auto-sklearn, surpassed standalone ML algorithms like SVM and k-Nearest Neighbors in differentiating between RCC and healthy controls, as well as OC patients and those with other gynecological cancers. The effectiveness of Auto-sklearn is highlighted by its AUC scores of 0.97 for RCC and 0.85 for OC, obtained from the unseen test sets. Importantly, on most of the metrics considered, Auto-sklearn demonstrated a better classification performance, leveraging a mix of algorithms and ensemble techniques. Shapley Additive Explanations (SHAP) provided a global ranking of feature importance, identifying dibutylamine and ganglioside GM(d34:1) as the top discriminative metabolites for RCC and OC, respectively. Waterfall plots offered local explanations by illustrating the influence of each metabolite on individual predictions. Dependence plots spotlighted metabolite interactions, such as the connection between hippuric acid and one of its derivatives in RCC, and between GM3(d34:1) and GM3(18:1_16:0) in OC, hinting at potential mechanistic relationships. Through decision plots, a detailed error analysis was conducted, contrasting feature importance for correctly versus incorrectly classified samples. In essence, our pipeline emphasizes the importance of harmonizing AutoML and XAI, facilitating both simplified ML application and improved interpretability in metabolomics data science.

The use of Bacillus subtilis as a cost-effective expression system for production of Cholera Toxin B fused factor VIII epitope regions applicable for inducing oral immune tolerance.

Coagulation factor replacement therapy for the X-linked bleeding disorder Haemophilia, characterized by a deficiency of coagulation protein factor VIII (FVIII), is severely complicated by antibody (inhibitors) formation. The development of FVIII inhibitors drastically alters the quality of life of the patients and is associated with a tremendous increase in morbidity as well as treatment costs. The ultimate goal of inhibitor control is antibody elimination. Immune tolerance induction (ITI) is the only clinically established approach for developing antigen-specific tolerance to FVIII. This work aims to establish a novel cost-effective strategy to produce FVIII molecules in fusion with cholera toxin B (CTB) subunit at the N terminus using the Bacillus subtilis expression system for oral tolerance, as the current clinical immune tolerance protocols are expensive. Regions of B-Domain Deleted (BDD)-FVIII that have potential epitopes were identified by employing Bepipred linear epitope prediction; 2 or more epitopes in each domain were combined and cDNA encoding these regions were fused with CTB and cloned in the Bacillus subtilis expression vector pHT43 and expression analysis was carried out. The expressed CTB-fused FVIII epitope domains showed strong binding affinity towards the CTB-receptor GM1 ganglioside. To conclude, Bacillus subtilis expressing FVIII molecules might be a promising candidate for exploring for the induction of oral immune tolerance.

Tailored multivalent peptide targeting the B-subunit pentamer of cholera toxin inhibits its intestinal toxicity by inducing aberrant transport of the toxin in cells

Cholera toxin (Ctx) is a major virulence factor produced by Vibrio cholerae that can cause gastrointestinal diseases, including severe watery diarrhea and dehydration, in humans. Ctx binds to target cells through multivalent interactions between its B-subunit pentamer and the receptor ganglioside GM1 present on the cell surface. Here, we identified a series of tetravalent peptides that specifically bind to the receptor-binding region of the B-subunit pentamer using affinity-based screening of multivalent random-peptide libraries. These tetravalent peptides efficiently inhibited not only the cell-elongation phenotype but also the elevated cAMP levels, both of which are induced by Ctx treatment in CHO cells or a human colon carcinoma cell line (Caco-2 cells), respectively. Importantly, one of these peptides, NRR-tet, which was highly efficient in these two activities, markedly inhibited fluid accumulation in the mouse ileum caused by the direct injection of Ctx. In consistent, NRR-tet reduced the extensive Ctx-induced damage of the intestinal villi. After NRR-tet bound to Ctx, the complex was incorporated into the cultured epithelial cells and accumulated in the recycling endosome, affecting the retrograde transport of Ctx from the endosome to the Golgi, which is an essential process for Ctx to exert its toxicity in cells. Thus, NRR-tet may be a novel type of therapeutic agent against cholera, which induces the aberrant transport of Ctx in the intestinal epithelial cells, detoxifying the toxin.

Development of an Infantile GM2 Clinical Rating Scale: Remote Assessment of Clinically Meaningful Health-Related Function.

GM2 gangliosidoses (GM2) are a group of rare lysosomal storage disorders in which accumulation of GM2 gangliosides results in progressive central nervous system damage. The infantile GM2 phenotype is characterized by delays in milestones by 6 months of age, followed by rapid loss of motor, cognitive, and visual function. Advancements in early diagnosis and pharmacotherapies provide promise for improved outcomes. However, the lack of feasible and clinically meaningful clinical outcome assessments for GM2 poses a challenge to characterizing GM2 natural history and selecting clinical trial endpoints. The purpose of this study was to develop a remotely administered infantile GM2 rating scale to measure health-related function in children with infantile GM2. A 2-phase mixed methods design was employed. In phase 1 of the study, 8 families of children with Infantile GM2 completed a natural history survey and a 1:1 semistructured interview to provide caregiver perspectives on the impacts of GM2 on health-related function. In phase 2 of the study, 8 expert clinicians provided feedback via surveys and participated in videoconference-hosted focus groups to refine scale administration and scoring procedures. These methods guided the development of 16 scale items to assess function in 5 health-related function domains: vision, hand and arm use, communication, gross motor, and feeding. This study used caregiver perspectives and expert clinician feedback to develop a remotely administered clinical outcome assessment of clinically meaningful health-related function in children with infantile GM2. Future studies will further evaluate the feasibility, reliability, and validity of the Infantile GM2 Clinical Rating Scale.

Central cord syndrome: Mechanisms, clinical presentation, and management strategies

Central Cord Syndrome (CCS) is a prevalent form of incomplete spinal cord injury (SCI) characterized by distinct motor and sensory deficits. This paper discusses the nuances of CCS, covering epidemiology, etiology, mechanisms, clinical presentation, diagnosis, predictive factors for outcomes, management strategies, and emerging therapeutic approaches. CCS accounts for a significant portion of SCIs, with trauma, particularly hyperextension injuries in individuals with preexisting spinal stenosis, being the primary cause. Patient demographics reveal skewed distributions in age, sex, and race, influencing outcomes and care approaches. Symptoms impact patients' quality of life extensively, ranging from motor dysfunction to neuropathic pain and bladder complications. Diagnosis involves a multifaceted approach utilizing clinical assessment tools, radiological imaging, and electrophysiological tests. Predictive factors for outcomes include age, time to presentation, and injury severity, guiding treatment decisions between conservative and surgical approaches. Initial management strategies focus on trauma assessment, neuroprotection, and preventing secondary injury. While established treatments have evolved, emerging therapies present promising avenues, including GM1 gangliosides, riluzole, minocycline, stem cell therapy, and transcutaneous electrical spinal stimulation. In conclusion, this paper sheds light on the multifaceted nature of CCS, exploring various aspects from epidemiology to emerging therapeutic approaches. It offers valuable insights for the advancement of care and outcomes in individuals affected by CCS.

Aβ peptide enhances GluA1 internalization via lipid rafts in Alzheimer's-related hippocampal LTP dysfunction.

Amyloid β (Aβ) is a central contributor to neuronal damage and cognitive impairment in Alzheimer's disease (AD). Aβ disrupts AMPA receptor-mediated synaptic plasticity, a key factor in early AD progression. Numerous studies propose that Aβ oligomers hinder synaptic plasticity, particularly long-term potentiation (LTP), by disrupting GluA1 (encoded by GRIA1) function, although the precise mechanism remains unclear. In this study, we demonstrate that Aβ mediates the accumulation of GM1 ganglioside in lipid raft domains of cultured cells, and GluA1 exhibits preferential localization in lipid rafts via direct binding to GM1. Aβ enhances the raft localization of GluA1 by increasing GM1 in these areas. Additionally, chemical LTP stimulation induces lipid raft-dependent GluA1 internalization in Aβ-treated neurons, resulting in reduced cell surface and postsynaptic expression of GluA1. Consistent with this, disrupting lipid rafts and GluA1 localization in rafts rescues Aβ-mediated suppression of hippocampal LTP. These findings unveil a novel functional deficit in GluA1 trafficking induced by Aβ, providing new insights into the mechanism underlying AD-associated cognitive dysfunction.

Silencing of B4Galnt1 Gene Prevents GM2 Accumulation in Tay-Sachs Cells

Introduction. The Tay-Sachs disease (TSD) is a progressive neurodegenerative disorder resulting from genetic mutations in the HEXA gene encoding the α-subunit of β-hexosaminidase A leading to the accumulation of GM2 ganglioside in the central nervous system. Multiple therapeutical strategies have been investigated such as gene therapy for Tay-Sachs patients; however, there is still no cure. In the present study, we suggest a new approach for the treatment of the Tay-Sachs disease with the concept of substrate reduction therapy by using AAV9-mediated RNAi technology targeting the B4Galnt1 gene at the upstream of the enzymatic defect in TSD pathology to decrease GM2 biosynthesis and accumulation in cell models of TSD. Material and Methods. We employed AAV9-mediated shRNA transduction for mice and human Tay-Sachs cells. After transduction, expression levels of ganglioside metabolism genes were analyzed by RT-PCR and GM2 and lysosome-associated membrane protein 1 (LAMP1) protein levels were evaluated by immunocytochemistry analysis. Results. Here, we have shown that AAV9-shRNA transduction effectively reduced B4Galnt1 expression in TSD cells demonstrating a reduction in GM2 accumulation and LAMP1. Discussion. Our data shows that AAV-mediated B4Galnt1-shRNA transduction can ameliorate disease pathologies by decreasing the lysosomal accumulation of GM2 through selectively reducing B4Gant1 activity in cell models of the Tay-Sachs disease. Therefore, we suggest promising novel experimental therapy for this devastating disease using a mouse model in the future.

Cinnamic acid, a natural plant compound, exhibits neuroprotection in a mouse model of Sandhoff disease via PPARα.

Tay-Sachs disease (TSD) and its severe form Sandhoff disease (SD) are autosomal recessive lysosomal storage metabolic disorders, which often result into excessive GM2 ganglioside accumulation predominantly in lysosomes of nerve cells. Although patients with these diseases appear normal at birth, the progressive accumulation of undegraded GM2 gangliosides in neurons leads to early death accompanied by manifestation of motor difficulties and gradual loss of behavioral skills. Unfortunately, there is still no effective treatment available for TSD/SD. The present study highlights the importance of cinnamic acid (CA), a naturally occurring aromatic fatty acid present in a number of plants, in inhibiting the disease process in a transgenic mouse model of SD. Oral administration of CA significantly attenuated glial activation and inflammation and reduced the accumulation of GM2 gangliosides/glycoconjugates in the cerebral cortex of Sandhoff mice. Besides, oral CA also improved behavioral performance and increased the survival of Sandhoff mice. While assessing the mechanism, we found that oral administration of CA increased the level of peroxisome proliferator-activated receptor α (PPARα) in the brain of Sandhoff mice and that oral CA remained unable to reduce glycoconjugates, improve behavior and increase survival in Sandhoff mice lacking PPARα. Our results indicate a beneficial function of CA that utilizes a PPARα-dependent mechanism to halt the progression of SD and thereby increase the longevity of Sandhoff mice.

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.

Ganglioside GM1 Drives Hemin and Protoporphyrin Adsorption in Phospholipid Membranes: A Structural Study.

Monosialoganglioside (GM1), a ubiquitous component of lipid rafts, and hemin, an integral part of heme proteins such as hemoglobin, are essential to the cell membranes of brain neurons and erythrocyte red blood cells for regulating cellular communication and oxygen transport. Protoporphyrin IX (PPIX) and its derivative hemin, on the contrary, show significant cytotoxic effects when in excess causing hematological diseases, such as thalassemia, anemia, malaria, and neurodegeneration. However, the in-depth molecular etiology of their interactions with the cell membrane has so far been poorly understood. Herein, the structure of the polymer cushion-supported lipid bilayer (SLB) of the binary mixture of phospholipid and GM1 in the presence of PPIX and its derivative hemin has been investigated to predict the molecular interactions in model phospholipid membranes. A high-resolution synchrotron-based X-ray scattering technique has been employed to explore the out-of-plane structure of the assembly at different compositions and concentrations. The structural changes have been complemented with the isobaric changes in the mean molecular area obtained from the Langmuir monolayer isotherm to predict the additive-induced membrane condensation and fluidization. PPIX-induced fluidization of phospholipid SLB without GM1 was witnessed, which was reversed to condensation with 2-fold higher structural changes in the presence of GM1. A hemin concentration-dependent linear condensing effect was observed in the pristine SLB. The effect was significantly reduced, and the linearity was observed to be lost in the mixed SLB containing GM1. Our study shows that GM1 alters the interaction of hemin and PPIX with the membrane, which could be explained with the aid of hydrophobic and electrostatic interactions. Our study indicates favorable and unfavorable interactions of GM1 with PPIX and hemin, respectively, in the membrane. The observed structural changes in both SLB and the underlying polymer cushion layer lead to the proposal of a molecule-specific interaction model that can benefit the pharmaceutical industries specialized for drug designing. Our study potentially enriches our fundamental biophysical understanding of neurodegenerative diseases and drug-membrane interactions.

Campylobacter jejuni extracellular vesicles harboring cytolethal distending toxin bind host cell glycans and induce cell cycle arrest in host cells.

Campylobacter jejuni is the leading cause of foodborne gastroenteritis in humans worldwide and a significant cause of childhood mortality due to diarrheal disease in developing countries. A major factor by which C. jejuni causes disease is a toxin, called cytolethal distending toxin (CDT). The biology of this toxin, however, is poorly understood. In this study, we report that C. jejuni CDT is protected within membrane blebs, known as extracellular vesicles (EVs), released by the bacterium. We showed that proteins on the surfaces of EVs are not required for EV uptake by host cells. Furthermore, we identified several sugar receptors that may be required for EV binding to host cells. By studying the EV-associated form of C. jejuni CDT, we will gain a greater understanding of how C. jejuni intoxicates host cells and how EV-associated CDT may be used in various therapeutic applications, including as anti-tumor therapies.

Chimeric antigen receptor T cells targeting the GM3(Neu5Gc) ganglioside.

Chimeric antigen receptor (CAR) T cell technology has ushered in a new era of immunotherapy, enabling the targeting of a broad range of surface antigens, surpassing the limitations of traditional T cell epitopes. Despite the wide range of non-protein tumor-associated antigens, the advancement in crafting CAR T cells for these targets has been limited. Owing to an evolutionary defect in the CMP-Neu5Ac hydroxylase (CMAH) that abolishes the synthesis of CMP-Neu5Gc from CMP-Neu5Ac, Neu5Gc is generally absent in human tissues. Despite this, Neu5Gc-containing antigens, including the ganglioside GM3(Neu5Gc) have consistently been observed on tumor cells across a variety of human malignancies. This restricted expression makes GM3(Neu5Gc) an appealing and highly specific target for immunotherapy. In this study, we designed and evaluated 14F7-28z CAR T cells, with a targeting unit derived from the GM3(Neu5Gc)-specific murine antibody 14F7. These cells exhibited exceptional specificity, proficiently targeting GM3(Neu5Gc)-expressing murine tumor cells in syngeneic mouse models, ranging from B cell malignancies to epithelial tumors, without compromising safety. Notably, human tumor cells enhanced with murine Cmah were effectively targeted and eliminated by the 14F7 CAR T cells. Nonetheless, despite the detectable presence of GM3(Neu5Gc) in unmodified human tumor xenografts, the levels were insufficient to trigger a tumoricidal T-cell response with the current CAR T cell configuration. Overall, our findings highlight the potential of targeting the GM3(Neu5Gc) ganglioside using CAR T cells across a variety of cancers and set the stage for the optimization of 14F7-based therapies for future human clinical application.

Determination of biomarker candidates for the placenta accreta spectrum by plasma proteomic analysis

Placenta accreta spectrum (PAS) presents a significant obstetric challenge, associated with considerable maternal and fetal-neonatal morbidity and mortality. Nevertheless, it is imperative to acknowledge that a noteworthy subset of PAS cases remains undetected until the time of delivery, thereby contributing to an augmented incidence of morbidity among the affected individuals. The delayed identification of PAS not only hinders timely intervention but also exacerbates the associated health risks for both the maternal and fetal outcomes. This underscores the urgency to innovate strategies for early PAS diagnosis. In this study, we aimed to explore plasma proteins as potential diagnostic biomarkers for PAS. Integrated transcriptome and proteomic analyses were conducted to establish a novel diagnostic approach. A cohort of 15 pregnant women diagnosed with PAS and delivering at Inonu University Faculty of Medicine between 01/04/2021 and 01/01/2023, along with a matched control group of 15 pregnant women without PAS complications, were enrolled. Plasma protein identification utilized enzymatic digestion and liquid chromatography-tandem mass spectrometry techniques. Proteomic analysis identified 228 plasma proteins, of which 85 showed significant differences (P < 0.001) between PAS and control cases. We refined this to a set of 20 proteins for model construction, resulting in a highly accurate classification model (96.9% accuracy). Notable associations were observed for proteins encoded by P01859 (Immunoglobulin heavy constant gamma 2), P02538 (Keratin type II cytoskeletal 6A), P29622 [Kallistatin (also known as Serpin A4)], P17900 (Ganglioside GM2 activator Calmodulin-like protein 5), and P01619 (Immunoglobulin kappa variable 3–20), with fold changes indicating their relevance in distinguishing PAS from control groups. In conclusion, our study has identified novel plasma proteins that could serve as potential biomarkers for early diagnosis of PAS in pregnant women. Further research and validation in larger PAS cohorts are necessary to determine the clinical utility and reliability of these proteomic biomarkers for diagnosing PAS.

Molecular and cellular evidence of a direct interaction between the TRAF2 C-terminal domain and ganglioside GM1

TNF receptor-associated factor 2 (TRAF2) is involved in different cellular processes including signal transduction and transcription regulation. We here provide evidence of a direct interaction between the TRAF domain of TRAF2 and the monosialotetrahexosylganglioside (GM1). Previously, we showed that the TRAF domain occurs mainly in a trimeric form in solution, but it can also exist as a stable monomer when in the nanomolar concentration range. Here, we report that the quaternary structure of the TRAF domain is also affected by pH changes, since a weakly acidic pH (5.5) favors the dissociation of the trimeric TRAF domain into stable monomers, as previously observed at neutral pH (7.6) with the diluted protein. The TRAF domain-GM1 binding was similar at pH 5.5 and 7.6, suggesting that GM1 interacts with both the trimeric and monomeric forms of the protein. However, only the monomeric protein appeared to cause membrane deformation and inward vesiculation in GM1-containing giant unilamellar vesicles (GUVs). The formation of complexes between GM1 and TRAF2, or its TRAF domain, was also observed in cultured human leukemic HAP1 cells expressing either the truncated TRAF domain or the endogenous full length TRAF2. The GM1-protein complexes were observed after treatment with tunicamycin and were more concentrated in cells undergoing apoptosis, a condition which is known to cause cytoplasm acidification. These findings open the avenue for future studies aimed at deciphering the physiopathological relevance of the TRAF domain-GM1 interaction.

Evaluation of the effects of HexM and its mannose-6-hyper-phosphorylated form (PhosHexM) in reducing GM2 ganglioside storage in a Tay-Sachs disease mouse model

Evaluation of the effects of HexM and its mannose-6-hyper-phosphorylated form (PhosHexM) in reducing GM2 ganglioside storage in a Tay-Sachs disease mouse model

Alterations in Plasma Lipid Profiles Associated with Melanoma and Therapy Resistance.

Dysfunctions of lipid metabolism are associated with tumor progression and treatment resistance of cutaneous melanoma. BRAF/MEK inhibitor resistance is linked to alterations of melanoma lipid pathways. We evaluated whether a specific lipid pattern characterizes plasma from melanoma patients and their response to therapy. Plasma samples from patients and controls were analyzed for FASN and DHCR24 levels and lipidomic profiles. FASN and DHCR24 expression resulted in association with disease condition and related to plasma cholesterol and triglycerides in patients at different disease stages (n = 144) as compared to controls (n = 115). Untargeted lipidomics in plasma (n = 40) from advanced disease patients and controls revealed altered levels of different lipids, including fatty acid derivatives and sphingolipids. Targeted lipidomics identified higher levels of dihydroceramides, ceramides, sphingomyelins, ganglioside GM3, sphingosine, sphingosine-1-phosphate, and dihydrosphingosine, saturated and unsaturated fatty acids. When melanoma patients were stratified based on a long/short-term clinical response to kinase inhibitors, differences in plasma levels were shown for saturated fatty acids (FA 16:0, FA18:0) and oleic acid (FA18:1). Our results associated altered levels of selected lipid species in plasma of melanoma patients with a more favorable prognosis. Although obtained in a small cohort, these results pave the way to lipidomic profiling for melanoma patient stratification.

Filipin complex-reactive brain lesions: a cautionary tale.

Filipin complex is an autooxidation-prone fluorescent histochemical stain used in the diagnosis of Niemann-Pick Disease Type C (NP-C), a neurodegenerative lysosomal storage disorder. It is also widely used by researchers examining the distribution and accumulation of unesterified cholesterol in cell and animal models of neurodegenerative diseases including NP-C and Sanfilippo syndrome (mucopolysaccharidosis IIIA; MPS IIIA). Recently, it has been suggested to be useful in studying Alzheimer's and Huntington's disease. Given filipin's susceptibility to photobleaching, we sought to establish a quantitative biochemical method for free cholesterol measurement. Brain tissue from mice with MPS IIIA was stained with filipin. Total and free cholesterol in brain homogenates was measured using a commercially available kit and a quantitative LC-MS/MS assay was developed. Gangliosides GM1, GM2 and GM3 were also quantified using LC-MS/MS. As anticipated, the MPS IIIA mouse brain displayed large numbers of filipin-positive intra-cytoplasmic inclusions, presumptively endo-lysosomes. Challenging the prevailing dogma, however, we found no difference in the amount of free cholesterol in MPS IIIA mouse brain homogenates cf. control tissue, using either the fluorometric kit or LC-MS/MS assay. Filipin has previously been reported to bind to GM1 ganglioside, however, this lipid does not accumulate in MPS IIIA cells/tissues. Using a fluorometric assay, we demonstrate for the first time that filipin cross-reacts with both GM2 and GM3 gangliosides, explaining the filipin-reactive inclusions observed in MPS IIIA brain cells. Filipin is not specific for free cholesterol, and positive staining in any setting should be interpreted with caution.