Advanced mass spectrometry of glycosphingolipids takes the central stage in this thesis. Investigations focus on characterization of glycosphingolipid metabolism in health and disease with... Show moreAdvanced mass spectrometry of glycosphingolipids takes the central stage in this thesis. Investigations focus on characterization of glycosphingolipid metabolism in health and disease with emphasis to the detection and accurate quantitation of known and so far unknown glycosphingolipids and closely regulated metabolites. Inherited defects in lysosomal degradation of glycosphingolipids, in particular the glycosphingolipidoses Gaucher disease (GD) and Fabry disease (FD), relatively common lysosomal storage disorders, are key topics of examination. The thesis provides an introductory background on the field of research and contains three different sections describing conducted experimental work. Section one consists of studies reporting on the discovery of excessive occurrence of glycosphingoid bases in lysosomal storage diseases, the development of methods for their accurate quantitation in biological samples with UPLC-ESI-MS/MS and the use of these methods in diagnosis and disease monitoring. The great value of identical 13C-encoded (glyco)sphingolipids and their bases as internal standards in mass spectrometric quantitation of these lipids in biological materials is described. Section two introduces clinical aspects and challenges of GD and FD and provides examples of the practical value of lipid analyses in the GD and FD clinic. Section three concerns the pathophysiology of lysosomal disorders in glycosphingolipid metabolism and related fundamental investigations. Show less
The lysosomal β-glucosidase named glucocerebrosidase (GCase) is a retaining β-glucosidase that hydrolyzes the glycosphingolipid glucosylceramide (GlcCer) to ceramide and glucose at acid pH.... Show moreThe lysosomal β-glucosidase named glucocerebrosidase (GCase) is a retaining β-glucosidase that hydrolyzes the glycosphingolipid glucosylceramide (GlcCer) to ceramide and glucose at acid pH. Inherited deficiency of GCase causes Gaucher disease (GD), a relatively common lysosomal storage disorder. GCase fulfills another crucial function beyond lysosomes. The enzyme generates ceramides from GlcCer molecules in the outer part of the skin, the stratum corneum. This is essential for skin barrier properties compatible with terrestrial life. GCase is catalytically versatile and can hydrolyze as well as catalyze transglycosylation.In this thesis a novel sensitive in situ method for the detection of active GCase in skin sections is described. Followed by a study of skin sections of patiens with atopic dermatitis revealing that the localization and activity of GCase and acid sphingomyelinase (ASM) was abnormal in skin of AD patients, particularly at lesional skin sites.It is demonstrated that GCase not only cleaves 4-methylumbelliferyl-β-D-glucose, but also 4-methylumbelliferyl-β-D-xylose. It is reported for the first time that GCase is able to transxylosylate cholesterol to render xylosyl-β-cholesterol (XylChol). The formed XylChol can act as a subsequent acceptor for further transxylosylation, rendering di-xylosyl-cholesterol. And finally the discovery of of GlcChol as novel component of human epidermis is reported. Show less
Aerts, J.M.F.G.; Kuo, C.L.; Lelieveld, L.T.; Boer, D.E.C.; Lienden, M.J.C. van der; Overkleeft, H.S.; Artola, M. 2019
Glycosphingolipids are important building blocks of the outer leaflet of the cell membrane. They are continuously recycled, involving fragmentation inside lysosomes by glycosidases. Inherited... Show moreGlycosphingolipids are important building blocks of the outer leaflet of the cell membrane. They are continuously recycled, involving fragmentation inside lysosomes by glycosidases. Inherited defects in degradation cause lysosomal glycosphingolipid storage disorders. The relatively common glycosphingolipidosis Gaucher disease is highlighted here to discuss new insights in the molecular basis and pathophysiology of glycosphingolipidoses reached by fundamental research increasingly using chemical biology tools. We discuss improvements in the detection of glycosphingolipid metabolites by mass spectrometry and review new developments in laboratory diagnosis and disease monitoring as well as therapeutic interventions. Show less
Glycosylation is a widely occurring and complex modification found on lipids and proteins and is involved in the recognition, signaling and interaction events within the cell and between cells.... Show moreGlycosylation is a widely occurring and complex modification found on lipids and proteins and is involved in the recognition, signaling and interaction events within the cell and between cells. These events based on glycan structures result in adhesion, cell-matrix interaction and immune recognition. Alterations in the glycomic profile are considered a hallmark of various diseases, including cancer where it contributes to the development and progression of cancer, affecting cell-cell communication, cell-matrix interactions, tumor angiogenesis, invasion and metastasis. These functions are governed by different glycans and their terminal structures. In order to further explore these structures with regard to their potential as biomarkers and specific targets for diagnostic applications and therapeutical strategies for various diseases, in-depth glycomic analysis is needed. It is further noted that aberrant glycosylation not only results from the altered expression of glycosyltransferases (GTs) but also from the changed activity of GTs and glycosidases as well as the availability and abundance of sugar nucleotide donors. The aim of the research described in this thesis was to explore the glycomic signatures of colorectal cancer (CRC) in cell lines and tissues as well as of acute myeloid leukemia (AML) cell lines. Show less
Het onderzoek beschreven in dit proefschrift is gericht op de identificatie en karakterisering van regulatoren en/of effectoren van TGF-β-signalering en TGF-β-geïnduceerde EMT in pancreas-, long-... Show moreHet onderzoek beschreven in dit proefschrift is gericht op de identificatie en karakterisering van regulatoren en/of effectoren van TGF-β-signalering en TGF-β-geïnduceerde EMT in pancreas-, long- en borstkankertypes. Deze nieuw geïdentificeerde componenten en mechanismen kunnen worden onderzocht voor de ontwikkeling van geneesmiddelen voor kankertherapie. Show less
Background: Acute myeloid leukemia (AML) is a genetically and phenotypically heterogeneous disease that has been suffering from stagnant survival curves for decades. In the endeavor toward improved... Show moreBackground: Acute myeloid leukemia (AML) is a genetically and phenotypically heterogeneous disease that has been suffering from stagnant survival curves for decades. In the endeavor toward improved diagnosis and treatment, cellular glycosylation has emerged as an interesting focus area in AML. While mechanistic insights are still limited, aberrant glycosylation may affect intracellular signaling pathways of AML blasts, their interactions within the microenvironment, and even promote chemoresistance. Here, we performed a meta-omics study to portray the glycomic landscape of AML, thereby screening for potential subtypes and responsible glyco-regulatory networks. Results: Initially, by integrating comprehensive N-, O-, and glycosphingolipid (GSL)-glycomics of AML cell lines with transcriptomics from public databases, we were able to pinpoint specific glycosyltransferases (GSTs) and upstream transcription factors (TFs) associated with glycan phenotypes. Intriguingly, subtypes M5 and M6, as classified by the French-American-British (FAB) system, emerged with distinct glycomic features such as high (sialyl) Lewis(x/a) ((s)Le(x/a)) and high sialylation, respectively. Exploration of transcriptomics datasets of primary AML cells further substantiated and expanded our findings from cell lines as we observed similar gene expression patterns and regulatory networks that were identified to be involved in shaping AML glycan signatures. Conclusions: Taken together, our data suggest transcriptionally imprinted glycomic signatures of AML, reflecting their differentiation status and FAB classification. This study expands our insights into the emerging field of AML glycosylation and paves the way for studies of FAB class-associated glycan repertoires of AML blasts and their functional implications. Show less
Lysosomal storage disorders (LSDs) are a group of orphan diseases characterized by lysosomal dysfunction or impaired lysosomal catabolism and affect collectively about 1 in 5000 live births. A... Show moreLysosomal storage disorders (LSDs) are a group of orphan diseases characterized by lysosomal dysfunction or impaired lysosomal catabolism and affect collectively about 1 in 5000 live births. A common LSD is Gaucher disease, which is characterized by a defect in glucocerebrosidase (GCase) degrading glucosylceramide (GlcCer) in lysosomes. In this thesis, the zebrafish is evaluated as vertebrate animal model for the investigation of lysosomal storage disorders, in particular Gaucher disease. Zebrafish are an appealing model organism to study genetic disorders with a high evolutionary conservation of genes and proteins compared to humans, easy maintenance and simple genetic and pharmacological manipulation. Zebrafish larvae are of particular use as zebrafish can generate hundreds of off-spring which have a rapid embryonal development, are transparent and fit in a 96-wells plate. In this thesis several biochemical and genetic techniques have been developed in order to 1) compare the catalytic features of zebrafish GCase with human GCase, 2) investigate the consequences of its defect in zebrafish larvae and adults as well as a concomitant defect in non-lysosomal GBA2 and 3) study the potential toxicity of excessive glucosylsphingosine during GCase deficiency as consequence of a defect in lysosomal acid ceramidase. GCase-deficient zebrafish showed similar symptoms and affected molecular mechanisms as patients and mouse models. Therefore the zebrafish offers exciting new possibilities to study molecular mechanisms underlying pathological processes during lysosomal hydrolase deficiencies. Show less
