Expression Of Gangliosides Research Articles

1266P - Prognostic significance of tumour tissue NeuGcGM3 ganglioside expression and predictive value of circulating tumour cell count monitoring in patients receiving racotumomab immunotherapy

BackgroundRacotumomab is an anti-idiotype vaccine, a mirror image of N-Glycolylneuraminic acid (NeuGcGM3), which mimics this ganglioside and triggers an immune response in various tumors. In this study we investigated the prognostic significance of tissue NeuGcGM3 expression level and prognostic as well as predictive value of circulating tumor cell count monitoring in patients on Racotumomab treatment. MethodsOut of 48 patients characterized, 40 were non-small cell lung cancer (NSCLC), 12 stage III and 28 stage IV. 19 Adenocarcinoma and 21 Squamous Ca. 2 were small cell lung cancer (SCLC) and 6 with other carcinomas. Male/Female ratio was 3.36(37/11) and median age was 63 (31-84). All patients received Racotumomab as switch maintenance after chemotherapy. 7 PD-L1 (+) Pts also received check point inhibitors on progression. Expression of NeuGcGM3 was detected with 14F7 monoclonal antibody IHC staining and graded as 0,1+,2+ or 3+ according to intensity. Circulating tumor cell (CTC) count was monitored using Cell Sorter throughout the treatment course, before starting Racotumomab and every 3 months or on clinical progression. ResultsNeuGcGM3 IHC were performed 25 out of 48 patients whose paraffin blocks were available. 9 Patients had strong (3+), 12 had (2+) and 4 patients had (1+) NeuGcGM3 staining intensity. There was no statistically significant difference in the mean overall survival of the patients according to IHC staining level (1+) mean OS:55.3 months, (2+) mean OS:40.9 months, and (3+) OS:39.0 months. In 14 Patients, circulating tumor cell count was monitored from the blood and correlated well with clinical outcomes in 11 out of 14 patients (%78.5). Significant reduction of the CTC counts was compatible with clinical response whereas increased CTC counts were early messengers for clinical progression. ConclusionsThis study revealed that any grade of NeuGcGM3 positivity in the tumor tissue is adequate to select a patient for Racotumomab treatment regardless of the IHC intensity. We also concluded that CTC monitoring in patients receiving immunotherapy is a good predictive and prognostic tool. Legal entity responsible for the studyNecdet Uskent. FundingHas not received any funding. DisclosureAll authors have declared no conflicts of interest.

Relationship between ganglioside expression and anti-cancer effects of a plant-derived antibody in breast cancer cells

Relationship between ganglioside expression and anti-cancer effects of a plant-derived antibody in breast cancer cells

Gangliosides: The Double-Edge Sword of Neuro-Ectodermal Derived Tumors.

Gangliosides, the glycosphingolipids carrying one or several sialic acid residues, are mostly localized at the plasma membrane in lipid raft domains and implicated in many cellular signaling pathways mostly by interacting with tyrosine kinase receptors. Gangliosides are divided into four series according to the number of sialic acid residues, which can be also modified by O-acetylation. Both ganglioside expression and sialic acid modifications can be modified in pathological conditions such as cancer, which can induce either pro-cancerous or anti-cancerous effects. In this review, we summarize the specific functions of gangliosides in neuro-ectodermal derived tumors, and their roles in reprogramming the lipidomic profile of cell membrane occurring with the induction of epithelial-mesenchymal transition.

Aberrant expression of N-glycolyl GM3 ganglioside is associated with the aggressive biological behavior of human sarcomas

BackgroundThe aberrant expression of N-glycolyl GM3 ganglioside (NeuGcGM3) in patients with sarcomas was reevaluated by assessing the relation of this molecule with some clinicopathological features and overall survival (OS) of patients.MethodsFifty formalin-fixed and paraffin-embedded specimens from patients diagnosed with sarcomas were included. For the evaluation of NeuGcGM3, the 14F7 monoclonal antibody followed by a peroxidase avidin-biotin system was used. Clinicopathological features were obtained from patient records. Survival rates were estimated by the Kaplan-Meier method and compared with the log-rank test. For multivariate analyses, the Cox regression model was used to identify independent prognostic factors for OS.ResultsThe majority of samples had high levels of NeuGcGM3 expression (66.0%) that showed statistical correlation with age (p = 0.014), TNM stage (p = 0.022), histological grade (p = 0.013) and proliferation rates (p = 0.012). In addition, a tendency for association with tumor depth (p = 0.070) was evidenced. In univariate survival analysis, TNM stage (p = 0.000), occurrence of metastasis (p = 0.000) and expression of NeuGcGM3 (p = 0.034) were significant prognostic factors for OS, while a tendency for association was evidenced for histological grade (p = 0.091). Among these variables, only the presence of metastasis (p = 0.001) was an independent prognostic factor on multivariate analysis.ConclusionsThe present research suggests the evaluation of NeuGcGM3 expression as a complementary prognostic factor in sarcoma, although our results need to be validated in a larger series and prospective studies. Moreover, our results could support the use of this molecule as a target for immunotherapy.

Ganglioside GM1 promotes contact inhibition of growth by regulating the localization of epidermal growth factor receptor from glycosphingolipid-enriched microdomain to caveolae.

ObjectivesAccumulating data show that gangliosides are involved in regulation of cell proliferation. Specific changes in gangliosides expression associated with growth density of cells have been documented in several cell lines. However, the function and the potential mechanism of ganglioside GM1 in contact inhibition of growth are not clear.Materials and MethodsEdU incorporation assay and western blot were applied to detect the contact inhibition of growth in human mammary epithelial cells. GM1 manipulation of cell proliferation and epidermal growth factor receptor (EGFR) activation was investigated by immunoprecipitation, OptiPrep density gradient centrifugation and immunofluorescence. The function of GM1 on contact inhibition of growth was further studied by using GM1 stably knockdown and overexpression cells.ResultsMCF‐10A, MCF‐7 and MDA‐MB‐231 cells showed contact inhibition of growth in high‐density condition. Exogenous addition of GM1 to high‐density cells clearly inhibited cell growth and deactivated EGFR signalling. Compared to normal‐density cells, distribution of EGFR in high‐density cells was decreased in glycosphingolipid‐enriched microdomain (GEM), but more concentrated in caveolae, and incubation with GM1 obviously promoted this translocation. Furthermore, the cell growth and EGFR activation were increased in GM1 stably knockdown cells and decreased in GM1 stably overexpression cells when cultured in high density.ConclusionsOur results demonstrated that GM1 suppressed EGFR signalling and promoted contact inhibition of growth by changing the localization of EGFR from GEM to caveolae.

SiRNA-mediated knockdown of B3GALT4 decreases GM1 ganglioside expression and enhances vulnerability for neurodegeneration

Reduced levels of brain gangliosides GD1a, GD1b, GT1b and to a lesser extent GM1 have been found in substantia nigra (SN) from Parkinson's disease (PD) patients, along with decreased gene expression for key enzymes (B3Galt4, St3gal2) involved in synthesis of these gangliosides. Based on these observations, the present study examined the extent to which decreased expression of B3GALT4 mRNA and resulting decreased levels of GM1 ganglioside in dopaminergic cells may increase the vulnerability of these cells to degeneration in response to a neurotoxicant exposure that under normal circumstances would not result in neurodegeneration. Differentiated SK-N-SH cells were treated with B3GALT4 siRNA to significantly reduce B3GALT4 mRNA expression and decrease GM1 levels. Exposure of these cells to a low concentration (10 μM) of the neurotoxin MPP+ that previously produced no toxicity resulted in approximately 50% cell loss after B3GALT4 siRNA treatment. This was a similar a degree of cell loss observed with 100 μM MPP+ in normal, differentiated SK-N-SH cells. Addition of GM1 to the culture medium after siRNA treatment was able to significantly protect cells from enhanced MPP+ toxicity. These data suggest that decreased B3GALT4 and GM1 expression can increase cell vulnerability to potentially toxic stressors and that such mechanisms may contribute to dopaminergic neurodegeneration in PD.

Intracerebroventricular Infusion of Gangliosides Augments the Adult Neural Stem Cell Pool in Mouse Brain.

We previously reported that ganglioside GD3 is the predominant species in neural stem cells (NSCs) and reduced postnatal NSC pools are observed in both the subventricular zone and dentate gyrus (DG) of GD3-synthase knockout (GD3S-KO) mouse brains. Specifically, deficiency of GD3 in GD3S-KO animals revealed a dramatic reduction in cellularity in the DG of the hippocampus of the developing mouse brain, resulting in severe behavioral deficits in these animals. To further evaluate the functional role of GD3 in postnatal brain, we performed rescue experiments by intracerebroventricular infusion of ganglioside GD3 in adult GD3S-KO animals and found that it could restore the NSC pools and enhance the NSCs for self-renewal. Furthermore, 5xFAD mouse model was utilized, and GD3 restored NSC numbers and GM1 promoted neuronal differentiation. Our results thus demonstrate that exogenously administered gangliosides are capable to restore the function of postnatal NSCs. Since ganglioside expression profiles are associated not only with normal brain development but also with pathogenic mechanisms of diseases, such as Alzheimer’s disease, we anticipate that the administration of exogenous gangliosides, such as GD3 and GM1, may represent a novel and effective strategy for promoting adult neurogenesis in damaged brain for disease treatment.

Glial Sulfatides and Neuronal Complex Gangliosides Are Functionally Interdependent in Maintaining Myelinating Axon Integrity.

Sulfatides and gangliosides are raft-associated glycolipids essential for maintaining myelinated nerve integrity. Mice deficient in sulfatide (cerebroside sulfotransferase knock-out, CST−/−) or complex gangliosides (β-1,4-N-acetylegalactosaminyltransferase1 knock-out, GalNAc-T−/−) display prominent disorganization of proteins at the node of Ranvier (NoR) in early life and age-dependent neurodegeneration. Loss of neuronal rather than glial complex gangliosides underpins the GalNAc-T−/− phenotype, as shown by neuron- or glial-specific rescue, whereas sulfatide is principally expressed and functional in glial membranes. The similarities in NoR phenotype of CST−/−, GalNAc-T−/−, and axo–glial protein-deficient mice suggests that these glycolipids stabilize membrane proteins including neurofascin155 (NF155) and myelin-associated glycoprotein (MAG) at axo–glial junctions. To assess the functional interactions between sulfatide and gangliosides, CST−/− and GalNAc-T−/− genotypes were interbred. CST−/−× GalNAc-T−/− mice develop normally to postnatal day 10 (P10), but all die between P20 and P25, coinciding with peak myelination. Ultrastructural, immunohistological, and biochemical analysis of either sex revealed widespread axonal degeneration and disruption to the axo–glial junction at the NoR. In addition to sulfatide-dependent loss of NF155, CST−/− × GalNAc-T−/− mice exhibited a major reduction in MAG protein levels in CNS myelin compared with WT and single-lipid-deficient mice. The CST−/− × GalNAc-T−/− phenotype was fully restored to that of CST−/− mice by neuron-specific expression of complex gangliosides, but not by their glial-specific expression nor by the global expression of a-series gangliosides. These data indicate that sulfatide and complex b-series gangliosides on the glial and neuronal membranes, respectively, act in concert to promote NF155 and MAG in maintaining the stable axo–glial interactions essential for normal nerve function.SIGNIFICANCE STATEMENT Sulfatides and complex gangliosides are membrane glycolipids with important roles in maintaining nervous system integrity. Node of Ranvier maintenance in particular requires stable compartmentalization of multiple membrane proteins. The axo–glial adhesion molecules neurofascin155 (NF155) and myelin-associated glycoprotein (MAG) require membrane microdomains containing either sulfatides or complex gangliosides to localize and function effectively. The cooperative roles of these microdomains and associated proteins are unknown. Here, we show vital interdependent roles for sulfatides and complex gangliosides because double (but not single) deficiency causes a rapidly lethal phenotype at an early age. These findings suggest that sulfatides and complex gangliosides on opposing axo–glial membranes are responsible for essential tethering of the axo–glial junction proteins NF155 and MAG, which interact to maintain the nodal complex.

Induction of ganglioside synthesis in Drosophila brain accelerates assembly of amyloid \u03b2 protein

The assembly and deposition of amyloid β protein (Aβ) is a fundamental event during the early stages of Alzheimer’s disease (AD) and cerebral amyloid angiopathy. A growing body of evidence indicates that gangliosides form a pathological platform for the generation of ganglioside-bound Aβ, which facilitates the assembly of soluble Aβs; however, the molecular mechanisms underlying the binding of Aβ to gangliosides in the brain remain unclear due to the lack of an in vivo system that may address this issue. In insects, including the fruit fly Drosophila melanogaster, gangliosides are not intrinsically present at a detectable level. We herein demonstrate that ganglioside expression is inducible in Drosophila via the expression of transgenes of ganglioside synthesis enzymes and the feeding of exogenous sialic acid, and also that the induction of ganglioside synthesis significantly accelerates Aβ assembly in vivo. Our results support the hypothesis that gangliosides are responsible for Aβ assembly in vivo and also provide an opportunity to develop a valuable model for basic research as well as a therapeutic strategy for AD.

TNF differentially regulates ganglioside biosynthesis and expression in breast cancer cell lines.

Gangliosides are glycosphingolipids concentrated in glycolipid-enriched membrane microdomains. Mainly restricted to the nervous system in healthy adult, complex gangliosides such as GD3 and GD2 have been shown to be involved in aggressiveness and metastasis of neuro-ectoderm derived tumors such as melanoma and neuroblastoma. GD3 synthase (GD3S), the key enzyme that controls the biosynthesis of complex gangliosides, was shown to be over-expressed in Estrogen Receptor (ER)-negative breast cancer tumors, and associated with a decreased overall survival of patients. We previously demonstrated that GD3S expression in ER-negative breast cancer cells induced a proliferative phenotype and an increased tumor growth. In addition, our results clearly indicate that Tumor Necrosis Factor (TNF) induced GD3S over-expression in breast cancer cells via NFκB pathway. In this study, we analyzed the effect of TNF on ganglioside biosynthesis and expression in breast cancer cells from different molecular subtypes. We showed that TNF up-regulated the expression of GD3S in MCF-7 and Hs578T cells, whereas no change was observed for MDA-MB-231. We also showed that TNF induced an increased expression of complex gangliosides at the cell surface of a small proportion of MCF-7 cells. These results demonstrate that TNF differentially regulates gangliosides expression in breast cancer cell lines and establish a possible link between inflammation at the tumor site environment, expression of complex gangliosides and tumor development.

Altered Expression of Ganglioside Metabolizing Enzymes Results in GM3 Ganglioside Accumulation in Cerebellar Cells of a Mouse Model of Juvenile Neuronal Ceroid Lipofuscinosis.

Juvenile neuronal ceroid lipofuscinosis (JNCL) is caused by mutations in the CLN3 gene. Most JNCL patients exhibit a 1.02 kb genomic deletion removing exons 7 and 8 of this gene, which results in a truncated CLN3 protein carrying an aberrant C-terminus. A genetically accurate mouse model (Cln3Δex7/8 mice) for this deletion has been generated. Using cerebellar precursor cell lines generated from wildtype and Cln3Δex7/8 mice, we have here analyzed the consequences of the CLN3 deletion on levels of cellular gangliosides, particularly GM3, GM2, GM1a and GD1a. The levels of GM1a and GD1a were found to be significantly reduced by both biochemical and cytochemical methods. However, quantitative high-performance liquid chromatography analysis revealed a highly significant increase in GM3, suggesting a metabolic blockade in the conversion of GM3 to more complex gangliosides. Quantitative real-time PCR analysis revealed a significant reduction in the transcripts of the interconverting enzymes, especially of β-1,4-N-acetyl-galactosaminyl transferase 1 (GM2 synthase), which is the enzyme converting GM3 to GM2. Thus, our data suggest that the complex a-series gangliosides are reduced in Cln3Δex7/8 mouse cerebellar precursor cells due to impaired transcription of the genes responsible for their synthesis.

Down-regulation of glutamate release from hippocampal neurons by sialidase.

Sialidase, which removes sialic acid residues in sialylglycoconjugates, is essential for hippocampal memory and synaptic plasticity. Enzyme activity of sialidase is rapidly increased in response to neural excitation. Because sialic acid bound to gangliosides such as the tetra-sialoganglioside GQ1b is crucial for calcium signalling and neurotransmitter release, neural activity-dependent removal of sialic acid may affect hippocampal neurotransmission. In the present study, we found that 2-deoxy-2, 3-didehydro-D-N-acetylneuraminic acid (DANA), a sialidase inhibitor, increased expression of ganglioside GQ1b/GT1a in hippocampal acute slices. Extracellular glutamate level in the rat hippocampus measured by using in vivo microdialysis was increased by the sialidase inhibitor 2, 3-dehydro-2-deoxy-N-glycolylneuraminic acid as well as DANA. Synaptic vesicle exocytosis and intracellular Ca2+ increase evoked by high-K+ were also enhanced by DANA in primary cultured hippocampal neurons. Expression of GQ1b/GT1a was rapidly decreased by depolarization with high-K+, suggesting that the increase in sialidase activity by neural excitation is sufficient for cleavage of sialic acid. Our findings indicate that sialidase down-regulates glutamate release from hippocampal neurons via Ca2+ signalling modulation. Neural activity-dependent desialylation by sialidase may be a negative-feedback factor against presynaptic activity.

Ion mobility mass spectrometry provides novel insights into the expression and structure of gangliosides in the normal adult human hippocampus

Clustered into the so-called "glycosynaptic" microdomains in the central nervous system (CNS), gangliosides (GGs) are involved in the formation of functional synapses and neural circuits. Therefore, GGs are important biomarkers in the early diagnosis of CNS pathologies, which are the focus of our research as potential therapeutic targets. A series of neuropsychiatric disorders, including Alzheimer's disease and schizophrenia, are characterized by amnesia and disorientation caused by hippocampal atrophy and diminished cholinergic activity. Based on ion mobility mass spectrometry (IM-MS) capability for the reliable determination of glycopatterns, the changes in the diversity and number of GGs with age and the occurrence of neurological disorders, we report here the development of a high performance IM-MS strategy for assessing the GG profile in a complex mixture extracted from a 20 year old hippocampus. IM separation of GGs based on the charge state, carbohydrate chain length and degree of sialylation led to the detection and identification of 140 species, the largest number of GGs ever reported in an adult hippocampus. Moreover, the obtained data support the concept of GG cholinergic activity. IM tandem MS experiments using collision induced dissociation (CID) confirmed the incidence of GD1b(d18:1/24:1) in the investigated hippocampus specimen.

Biology of GM3 Ganglioside.

Since the successful molecular cloning in 1998 of GM3 synthase (GM3S, ST3GAL5), the enzyme responsible for initiating biosynthesis of all complex gangliosides, the efforts of our research group have been focused on clarifying the physiological and pathological implications of gangliosides, particularly GM3. We have identified isoforms of GM3S proteins having distinctive lengths of N-terminal cytoplasmic tails, and found that these cytoplasmic tails define subcellular localization, stability, and in vivo activity of GM3S isoforms. Our studies of the molecular pathogenesis of type 2 diabetes, focused on interaction between insulin receptor and GM3 in membrane microdomains, led to a novel concept: type 2 diabetes and certain other lifestyle-related diseases are membrane microdomain disorders resulting from aberrant expression of gangliosides. This concept has enhanced our understanding of the pathophysiological roles of GM3 and related gangliosides in various diseases involving chronic inflammation, such as insulin resistance, leptin resistance, and T-cell function and immune disorders (e.g., allergic asthma). We also demonstrated an essential role of GM3 in murine and human auditory systems; a common pathological feature of GM3S deficiency is deafness. This is the first direct link reported between gangliosides and auditory functions.

Hypothesis: Hypoxia induces de novo synthesis of NeuGc gangliosides in humans through CMAH domain substitute

Immunotherapy is a growing field in cancer research. A privileged tumor-associated antigen that has received much attention is N-glycolyl (NeuGc) GM3. This ganglioside is present in several types of cancer, but is almost undetectable in human healthy tissues. However, its non-hydroxylated variant, NeuAc GM3, is abundant in all mammals. Due to a deletion in the human gene encoding the key enzyme for synthesis of NeuGc, humans, in contrast to other mammals, cannot synthesize NeuGc GM3. Therefore the presence of this ganglioside in human cancer cells represents an enigma. It has been shown that hypoxic conditions trigger the expression of NeuGc gangliosides, which not only serve as attractive targets for cancer therapy, but also as diagnostic and prognostic tumor marker. Here, we confirm hypoxia-induced expression of the NeuGc GM3 ganglioside also in HeLa cells and reveal several candidate proteins, in particular GM3 synthase and subunit B of respiratory complex II (SDHB), that may be involved in the generation of NeuGc GM3 by SILAC-based proteome analysis. These findings have the potential to significantly advance our understanding of how this enigmatic tumor-associated antigen is produced in humans, and also suggest a possible mechanism of action of anti-tumor antibodies that recognize hypoxia markers, such as 14F7.

Cytolytic tests with hyperimmune patient sera is a good prognostic tool in racotumomab immunotherapy in advanced non-small cell lung cancer

<p>Aberrant accumulation of a specific sialic acid has been shown to exist in many human malignant cell membranes termed as N-glycolyl neuraminic acid (NeuGc). This particular ganglioside do not normally exist in normal human cells, due to the lack of an enzyme (cytidine monophospho-N-acetyl-neuraminic acid) which is responsible for the synthesis of N—glycolyl neurominic acid. The aberrant expression of NeuGcGM3 ganglioside in the cell surface of certain human tumors, made this molecule an attractive target for immunotherapy. By using 14 F7 monoclonal antibody directed to identify NeuGcGM3 in the tumor tissue, it is possible to select patients for anti-NeuGcGM3 immunotherapy. Racotumomab is an anti-idiotype vaccine, being a mirror image of NeuGcGm3 mimics this ganglioside and triggers an immune response. Antibodies reactive to NeuGcGM3 ganglioside in the vaccinated patient’s sera have cytotoxic anti-tumor properties which can be assessed in L1210 cell line, expressing this ganglioside.</p><p>In this study, we monitored 12 patients with advanced non-small cell lung cancer (NSCLC) who are on racotumomab vaccine maintenance following chemotherapy. Cytotoxic tests with vaccinated patients’ sera were performed using L1210 cell lines at the 3<sup>rd</sup>, 6<sup>th</sup>, 9<sup>th</sup>, and 12<sup>th</sup> months of vaccination and the results were compared with clinical outcomes. Serum antibodies to NeuGcGm3 ganglioside were also checked before initiation and thereafter with the same intervals. The aim of the study was to investigate the value of antibodies and cytotoxic test as biomarkers for treatment outcome. Our observation confirmed that consistently higher cytotoxicity rates in the cell culture correlated with better progression free survivals of the patients who are on racotumomab maintenance.</p>

Brain gangliosides in Alzheimer’s disease: Increased expression of cholinergic neuron-specific gangliosides

Background: Gangliosides are enriched in the neuronal membranes. Gangliosides are shown to interact with amyloid-β proteins, leading to formation of amyloid fibrils in Alzheimer’s disease (AD) brains. Several earlier studies indicated that the alterations of ganglioside metabolism could contribute the pathogenesis of AD. Methods: Gangliosides were isolated from the frontal lobes in five patients with AD and three control subjects. Gangliosides were assessed by high performance thin-layer chromatography (HPTLC) with resorcinol staining and immunostaining using mouse monoclonal antibodies against cholinergic neuronspecific (Chol-1α) gangliosides. Results: In all AD brains, not only the total sialic acid content but also a-series gangliosides, GM1 and GD1a, were dramatically reduced as compared with those in control subjects. These results are a hallmark of the pathogenesis in AD. In contrast, Chol-1α gangliosides, GT1aα and GQ1bα, which are specific markers of cholinergic neurons, were significantly increased in AD brains. Conclusion: The expression of Chol-1α gangliosides may be caused by a compensation to preserve the function of the cholinergic neuron and play an important role in cholinergic synaptic transmission.

PSA-NCAM expression in the teleost optic tectum is related to ecological niche and use of vision in finding food.

In this study, tangential migration and neuronal connectivity organization were analysed in the optic tectum of seven different teleosts through the expression of polysialylated neural cell adhesion molecule (PSA-NCAM) in response to ecological niche and use of vision. Reduced PSA-NCAM expression in rainbow trout Oncorhynchus mykiss optic tectum occurred in efferent layers, while in pike Esox lucius and zebrafish Danio rerio it occurred in afferent and efferent layers. Zander Sander lucioperca and European eel Anguilla anguilla had very low PSA-NCAM expression in all tectal layers except in the stratum marginale. Common carp Cyprinus carpio and wels catfish Silurus glanis had the same intensity of PSA-NCAM expression in all tectal layers. The optic tectum of all studied fishes was also a site of tangential migration with sustained PSA-NCAM and c-series ganglioside expression. Anti-c-series ganglioside immunoreactivity was observed in all tectal layers of all analysed fishes, even in layers where PSA-NCAM expression was reduced. Since the optic tectum is indispensable for visually guided prey capture, stabilization of synaptic contact and decrease of neurogenesis and tangential migration in the visual map are an expected adjustment to ecological niche. The authors hypothesize that this stabilization would probably be achieved by down-regulation of PSA-NCAM rather than c-series of ganglioside.

Electrospray ionization ion mobility mass spectrometry provides novel insights into the pattern and activity of fetal hippocampus gangliosides

Gangliosides (GGs), a particular class of glycosphingolipids ubiquitously found in tissues and body fluids, exhibit the highest expression in the central nervous system, especially in brain. GGs are involved in crucial processes, such as neurogenesis, synaptogenesis, synaptic transmission, cell adhesion, growth and proliferation. For these reasons, efforts are constantly invested into development and refinement of specific methods for GG analysis. We have recently shown that ion mobility separation (IMS) mass spectrometry (MS) has the capability to provide consistent compositional and structural information on GGs at high sensitivity, resolution and mass accuracy. In the present paper, we have implemented IMS MS for the first time in the study of a highly complex native GG mixture extracted and purified from human fetal hippocampus. As compared to previous studies, where no separation techniques prior to MS were applied, IMS MS technique has not just generated valuable novel information on the GG pattern characteristic for hippocampus in early developmental stage, but also provided data related to the GG molecular involvement in the synaptic functions by the discovery of 25 novel structures modified by CH3COO−. The detection and identification in fetal hippocampus of a much larger number of GG species than ever reported before was possible due to the ion mobility separation according to the charge state, the carbohydrate chain length and the degree of sialylation. By applying IMS in conjunction with collision induced dissociation (CID) tandem MS (MS/MS), novel GG species modified by CH3COO− attachment, discovered here for the first time, were sequenced and structurally investigated in details. The present findings, based on IMS MS, provide a more reliable insight into the expression and role of gangliosides in human hippocampus, with a particular emphasis on their cholinergic activity at this level.

Brain Gangliosides in Alzheimer's Disease: Increased Expression of Cholinergic Neuron-Specific Gangliosides.

Gangliosides are enriched in the neuronal membranes. Gangliosides are shown to interact with amyloid-β proteins, leading to formation of amyloid fibrils in Alzheimer's disease (AD) brains. Several earlier studies indicated that the alterations of ganglioside metabolism could contribute the pathogenesis of AD. Gangliosides were isolated from the frontal lobes in five patients with AD and three control subjects. Gangliosides were assessed by high performance thin-layer chromatography (HPTLC) with resorcinol staining and immunostaining using mouse monoclonal antibodies against cholinergic neuronspecific (Chol-1α) gangliosides. In all AD brains, not only the total sialic acid content but also a-series gangliosides, GM1 and GD1a, were dramatically reduced as compared with those in control subjects. These results are a hallmark of the pathogenesis in AD. In contrast, Chol-1α gangliosides, GT1aα and GQ1bα, which are specific markers of cholinergic neurons, were significantly increased in AD brains. The expression of Chol-1α gangliosides may be caused by a compensation to preserve the function of the cholinergic neuron and play an important role in cholinergic synaptic transmission.