La maladie d’Alzheimer (MA), la forme la plus répandue de démence, est caractérisée par une accumulation cérébrale de plaques amyloïdes formées de peptide beta-amyloïde, et d’enchevêtrements neurofibrillaires (NFT) de protéine tau anormalement phosphorylée (P-tau). Depuis plusieurs années, l’évidence d’une implication majeure d’altérations synaptiques dans la pathologie a émergée. De plus, il a été observé dans les cerveaux MA que les héparanes sulfates (HS), normalement extracellulaires, accumulent à l’intérieur des neurones, où ils co-localisent avec tau. Le laboratoire CRRET a mis en évidence que la 3-sulfotransferase 2 (HS3ST2), enzyme prédominante dans le cerveau où elle génère des HS 3-O-sulfatés (3S-HS) de rôle inconnu, est impliquée dans les mécanismes à l’origine de la tauopathie. Puisque la HS3ST2 et les 3S-HS n’ont jamais été caractérisés à la synapse où ils pourraient participer au développement de la tauopathie, les objectifs de ce travail sont : 1) déterminer si la HS3ST2 et les 3S-HS sont présents à la synapse et étudier des possibles rôles physiologiques ; 2) déterminer si les 3S-HS accumulent au niveau intracellulaire dans des cellules neuronales et/ou dans de synaptosomes issus d’un modèle murin de tauopathie ; et 3) examiner si les 3S-HS intracellulaires produits par la HS3ST2 sont impliqués dans le développement ou évolution de la tauopathie au niveau synaptique.Dans ce travail, nous avons montré la présence des 3S-HS et de la HS3ST2 à la synapse de cellules hippocampiques et accumulé des preuves de leur implication dans la stabilité et l’activité synaptique, toutes deux altérées par des peptides se liant aux 3S-HS ont pu bloquer cette activité. Nous avons implémenté et caractérisé le modèle murin de tauopathie rTg4510 et mise en place les cultures primaires de leur neurones hippocampiques. Dans ces cellules, nous avons montré l’accumulation intracellulaire des 3S-HS et une surexpression de la HS3ST2 corrélant avec l’accumulation de P-tau. La digestion enzymatique des HS dans les synaptosomes a résulté dans l’inhibition de la tauopathie.Ce travail révèle pour la première fois un rôle fondamental de la 3-O-sulfatation des chaines d’HS à la synapse, aussi bien dans des conditions physiologiques que pathologiques. Pour la première fois, l’enzyme HS3ST2 est décrite à la synapse. De plus, ce travail donne la preuve d’un lien fort entre l’expression d’HS3ST2, l’accumulation de 3S-HS et la tauopathie au niveau synaptique, ouvrant de nouvelles opportunités pour mieux comprendre la MA. / Alzheimer’s disease (AD), the main form of dementia in the world, is characterized by brain accumulation of amyloid plaques formed of amyloid beta, and neurofibrillary tangles (NFT) made of tau protein in an abnormally hyperphosphorylated form (P-tau). Strong evidences show that synaptic changes are central to the disease process. Moreover, previous observations in AD have shown that heparan sulfates (HS), typically present outside the cell , accumulate inside neurons of AD in where they interact with tau. Recently, the CRRET laboratory demonstrated that the neural 3-O-sulfotransferase 2 (HS3ST2), which generates 3-O-sulfated HS (3S-HS) of still unrevealed physiological roles, is involved in the mechanisms leading to tauopathy. Since it was unknown whether HS3ST2 and 3S-HS are expressed at the synapse and if there they participate to tauopathy development and/or evolution, the objectives of this work were: 1) to determine if HS3ST2 and 3S-HS are present at the synapse and to get insights on their physiological role; 2) to investigate whether 3S-HS accumulate intracellularly in hippocampal cells and/or in synaptosomes from a mice model of tauopathy; and 3) to investigate whether intracellular 3S-HS made by HS3ST2 are involved in tauopathy development and/or evolution at the synaptic level.We described here the presence of 3S-HS and HS3ST2 at the synapse and the role that may play 3S-HS in maintaining synaptic transmission and stability in primary cell culture from mice. These roles are the results of potential multiple implications of 3S-HS in various processes. Secondly, we implement and characterized the rTg4510 mice model of AD-related tauopathy and set primary cultures of hippocampal cells from these mice. In the tauopathic cells, we showed the intracellular accumulation of 3S-HS and HS3ST2 overexpression. Finally, we cleaned P-tau in synaptosomes from the rTg4510 mice aged of 2 months by digesting HS.The present work reveals, for the first time, the presence and a possible fundamental role of HS3ST2 and 3S-HS at the synapse. We give evidences of an interplay between 3S-HS, produced by HS3ST2, and tau and the synaptic level, leading to its abnormal phosphorylation. The results of these work open a new way to understand the phenomenon leading to synaptic impairment in AD patients and could reveal new targets to elaborate protection strategies against the AD pathological lesions.

京都大学 / 0048 / 新制・課程博士 / 博士(医学) / 甲第18141号 / 医博第3861号 / 新制||医||1002(附属図書館) / 30999 / 京都大学大学院医学研究科医学専攻 / (主査)教授 坂井 義治, 教授 髙田 穣, 教授 武藤 学 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

Glycans and glycoconjugates exert myriad important biological functions, extending and diversifying the functionality of protein molecules. Extensive studies have focused on the protein and gene realms; however, due to the lack of means for external amplification and the inherent heterogeneity of glycans and glycoconjugates, their researches have not adequately informed the understanding of critical biological and pathological processes. Researchers in glycoscience have strived to bridge this gap and redefine our understanding of carbohydrate functions. Glycosaminoglycans (GAGs) represent the most highly charged and poly-disperse animal glycans. GAGs exist on the surfaces of most mammalian cells and in the extracellular matrices. They play critical roles in anticoagulation, angiogenesis, inflammation, metastasis, cell proliferation and differentiation. Heparin and heparan sulfate (HS) are the most highly sulfated and structurally diverse GAGs, regulating a variety of cell functions by interacting directly with many growth factors and their receptors. Examples include fibroblast growth factor, bone morphogenetic protein and Wnt. These interactions rely on the unique structural properties of HS/heparin molecules. Extracellular enzymes (Sulfs and heparanase) also alter the fine structure of HS molecules. In order to investigate to the correlation between structure and function for mature HS/heparin chains, we employed mass spectrometry (MS) coupled with liquid chromatography (LC) as a sensitive and robust platform for composition profiling and detailed structural characterization. We developed a novel HPLC-chip based LC-MS platform to enable HS oligosaccharide profiling. In this thesis work, the chip LC-MS platform was improved for effective and informative tandem MS for HS oligosaccharides. We also advanced electron-based ion dissociation methods for more detailed and reliable sequence determination of HS oligosaccharides. These newly developed methods enable the investigation of the HS/heparin structural changes induced by HS extracellular remodeling enzymes, human Sulfs and heparanase. Application of the methods revealed the recognition preferences of these remodeling enzymes at the oligosaccharide level and led to the discovery of a novel peeling reaction induced by the 3-O-sulfation at the reducing end of HS saccharides.

No description available.

The primary aim of this text is to gain insight on how cellular activation by a insulin-like growth factor (IGF-I), in the presence of insulin-like growth factor binding protein-3 (IGFBP-3), is influenced by heparan sulfate proteoglycans (HSPG). Initial research will be presented, assumptions and hypotheses that were included in the development of mathematical models will be discussed, and the future enhancements of the models will be explored. There are many potential scenarios for how each component might influence the others. Mathematical modeling techniques will highlight the contributions made by numerous extracellular parameters on IGF-I cell surface binding. Tentative assumptions can be applied to modeling techniques and predictions may aid in the direction of future experiments. Experimentally, it was found that IGFBP-3 inhibited IGF-I Bovine Aortic Endothelial (BAE) cell surface binding while p9 HS slightly increased IGF-I BAE cell surface binding. IGFBP-3 has a higher binding affinity for IGF-I (3 x 10-9 M) than p9 HS has for IGF-I (1.5 x 10-8 M) as determined with cell-free binding assays. The presence of p9 HS countered the inhibiting effect of IGFBP-3 on IGF-I BAE cell surface binding. Although preliminary experiments with labeled p9 HS and IGFBP-3 indicated little to no cell surface binding, later experiments indicated that both IGFBP-3 and p9 HS do bind to the BAE cell surface. Pre-incubation of BAE cells with either IGFBP-3 or p9 HS resulted in an increase of IGF-I BAE cell surface binding . There was a more substantial increase of IGF-I surface binding when cells were pre-incubated with IGFBP- 3 than p9 HS. There was a larger increase of IGF-I BAE cell surface binding when cells were pre-incubated with p9 HS than when p9 HS and IGF-I were added simultaneously. This suggests that IGFBP-3 and p9 HS surface binding plays key role in IGF-I surface binding, however, p9 HS surface binding does not alter IGF-I surface binding as much as IGFBP-3 surface binding seems to. Experimental work helps further the understanding of IGF-I cellular activation as regulated by IGFBP-3 and p9 HS. Developing mathematical models allows the researcher to focus on individual elements in a complex systems and gain insight on how the real system will respond to individual changes. Discrepancies between the model results and the experimental data presented indicate that soluble receptor inhibition is not sufficient to account for experimental results. The alliance of engineering analysis and molecular biology helps to clarify significant principles relevant to the conveyance of growth factors into tissue. Awareness of the effects of individual parameters in the delivery system, made possible with mathematical models, will provide guidance and save time in the design of future therapeutics involving growth factors. / Master of Science

The correct patterning of embryos requires the exchange of information between cells. This is in part achieved by the proper distribution of signaling molecules, many of which exert their function by establishing gradients of concentration. Because of this property they were named "morphogens", or "form giving" substances. Among these, proteins belonging to the Hedgehog (Hh) family have received much attention, owing to their unusual double lipid modification and their involvement in human disease, causing congenital birth defects and cancer. Great efforts have been made in order to elucidate the mechanisms by which Hh molecules are propagated in the embryo. However, no conclusive evidence exists to date to which structures these molecules localize and how they, despite their membrane association, establish a gradient of concentration. Therefore, I decided to study the distribution of the vertebrate Hh homolog, Sonic Hedgehog (Shh) in developing zebrafish embryos. By fluorescently tagging Shh proteins, I found that these localize to discrete punctate structures at the membranes of expressing cells. These were often regions from which filopodial protrusions emanated from the cells. Puctate deposits of Shh were also located outside of expressing cells. In dividing cells, Shh accumulated at the cleavage plane. Furthermore, by making use of confocal microscopy and time lapse analysis, I visualized Shh proteins moving in filopodial extensions present between cells. This suggests a novel mechanism of Shh distribution, which relies on the direct contact of cells by filopodia for the exchange of signaling proteins. In a second part of my thesis, I characterized genes implicated in regulating Shh protein distribution and signaling function. I cloned three zebrafish genes belonging to the Ext1 (exostosin) family of glycosyltransferases required for the synthesis of Heparan Sulfate Proteoglycans and established a tentative link of these genes to somitic Hh signaling. In addition, I characterized the developmental expression and function of zebrafish Rab23, a small GTPase, which acts as a negative regulator of the Shh signaling pathway. Performing knock-down experiments of zebrafish Rab23, I found that Rab23 functions in left-right axis specification, a process previously shown to depend on proper Shh signaling.

The correct patterning of embryos requires the exchange of information between cells. This is in part achieved by the proper distribution of signaling molecules, many of which exert their function by establishing gradients of concentration. Because of this property they were named "morphogens", or "form giving" substances. Among these, proteins belonging to the Hedgehog (Hh) family have received much attention, owing to their unusual double lipid modification and their involvement in human disease, causing congenital birth defects and cancer. Great efforts have been made in order to elucidate the mechanisms by which Hh molecules are propagated in the embryo. However, no conclusive evidence exists to date to which structures these molecules localize and how they, despite their membrane association, establish a gradient of concentration. Therefore, I decided to study the distribution of the vertebrate Hh homolog, Sonic Hedgehog (Shh) in developing zebrafish embryos. By fluorescently tagging Shh proteins, I found that these localize to discrete punctate structures at the membranes of expressing cells. These were often regions from which filopodial protrusions emanated from the cells. Puctate deposits of Shh were also located outside of expressing cells. In dividing cells, Shh accumulated at the cleavage plane. Furthermore, by making use of confocal microscopy and time lapse analysis, I visualized Shh proteins moving in filopodial extensions present between cells. This suggests a novel mechanism of Shh distribution, which relies on the direct contact of cells by filopodia for the exchange of signaling proteins. In a second part of my thesis, I characterized genes implicated in regulating Shh protein distribution and signaling function. I cloned three zebrafish genes belonging to the Ext1 (exostosin) family of glycosyltransferases required for the synthesis of Heparan Sulfate Proteoglycans and established a tentative link of these genes to somitic Hh signaling. In addition, I characterized the developmental expression and function of zebrafish Rab23, a small GTPase, which acts as a negative regulator of the Shh signaling pathway. Performing knock-down experiments of zebrafish Rab23, I found that Rab23 functions in left-right axis specification, a process previously shown to depend on proper Shh signaling.

Heparan sulfate (HS), an unbranched sulfated carbohydrate chain, and the HS-degrading enzyme heparanase play important roles in physiological and pathological processes during all stages of life, from early embryogenesis to ageing. Accumulated information shows that HS and heparanase are involved in inflammatory processes and associated diseases, e.g. rheumatoid arthritis (RA) and Alzheimer’s disease. In this thesis I have investigated the role of HS and heparanase (Hpa) in inflammatory-related pathologies. In the first project, Hpa overexpressing mice (Hpa-tg) were induced with a murine model of RA. We found a pro-inflammatory role of Hpa through enhancing the activity of T-cells and innate immune cells, which contributed to an augmented severity of clinical symptoms in the Hpa-tg mice. In my second project, we revealed co-current interaction of heparin with both ApoA1 and SAA of HDL isolated from plasma of inflamed mouse. Mass spectrometry analysis indicated close proximity of ApoA1 and SAA on the HDL surface, providing a molecular and structural mechanism for the simultaneous binding of heparin to apoA1 and SAA. In my third project, we investigated the role of Hpa in AA amyloid formation and resolution in mice in a model of AA-amyloidosis. We found a similar degree of amyloid formation in Hpa-KO mice compared to the wildtype control mice, but the resolution process was faster in Hpa-KO mice. The rapid clearance of deposited SAA in Hpa-KO mice was associated with upregulated expression of matrix metalloproteases. The results suggest an associated function of ECM proteases with heparanase in the process of AA amyloid resolution. In my fourth project, we found that overexpression of heparanase impaired inflammation associated beta amyloid (Aβ) clearance in the brain of an Alzheimer’s disease mouse model. Examination of the cytokine profile of brain lysates revealed an overall lower inflammatory reaction in the double transgenic (tgHpa*Swe) mice compared to single APP-tg (tg-Swe) mice in response to LPS-induced inflammation.

En accordance avec son haut prévalence dans le monde, parmi tous les cas de démence, la maladie d'Alzheimer (MA) est considérée comme la principal pathologie affectant les personnes plus âgées que 65 ans. Depuis son première description en 1907, de la recherche important et des observations innovants ont été faites concernant des aspects histopathologiques et moléculaires la neurodégénération associée à la maladie. Cependant, les mécanismes moléculaires de la pathogenèse et de la progression de la MA restent toujours partiellement compris. Outre, des stratégies thérapeutiques efficaces soit pour la prévention, soit pour l'arrêt de la progression de la maladie ne sont pas encore développées. Il semble donc crucial le développement de la recherche dans des domaines émergeants, nés à partir des concepts innovants et basés sur des approches mécanistiques novateurs à fin de découvrir des aspects dans la physiopathologie de la neurodégénérescence qui puissent conduire à des stratégies thérapeutiques pour soigner ces maladies.Les études présentées ici sont centrées dans le rôle des héparanes sulfates (HS), un membre particulier de la famille des glycosaminoglycannes, dans la physiopathologie des troubles neurodégénératifs, tels que la MA et démences associées, nommées taupathies. Ce travail de recherche, basé sur plusieurs observations isolées suggérant une association entre la pathologie de tau caractéristique des taupathies et les HS, explore par des moyens de études moléculaires, cellulaires et animaux les implications pathologiques de telle interaction. Comme résultat, je montre ici des évidences suggérant une participation clé des HS dans les évènements pathologiques de tau, tels que la phosphorylation anormale, la formation des inclusions intracellulaires, et la propagation des amas de tau.Globalement, le travail présenté ici dévoile une implication importante des HS hautement sulfatés dans la pathologie de tau associée à la MA, et au même temps ouvre une gamme de voies de recherche novatrices pour approfondir dans la caractérisation de l'interaction tau/HS et ses consequences physiopathologiques. De plus, ceci suggère des cibles pharmacologiques alternatives qui puisèrent donner d'espoir pour trouver un traitement effectif pour la MA. / According to its higher prevalence worldwide among all dementia cases, Alzheimer's disease (AD) is placed as the first pathology affecting people aged of more than 65 years old. Since it first description in 1907, profound research and groundbreaking observations have been made concerning the histopathological and molecular aspects of its associated neurodegeneration. However, the molecular mechanisms of AD pathogenesis and progression remain still poorly understood. In addition, an efficient therapeutic approach to either prevent or stop the disease progression has not yet been developed. It becomes hence crucial to develop research in emerging areas raising from groundbreaking concepts and supported by new mechanistic approaches in order to unveil novel aspects of the physiopathology of neurodegeneration and therefore design new therapeutic approaches to treat these pathologies.The present study is focused on the role of heparan sulfate (HS), a particular member of the glycosaminoglycan family, in the physiopathology of neurodegenerative disorders, such as AD and related dementias, termed tauopathies. Based on numerous separate observations suggesting an association between tau pathology characteristic of tauopathies and HS, this research explores the pathological implications of such interaction by the means of molecular, cellular, and animal studies. As a result, I hereby present evidence suggesting a crucial involvement of HS in tau pathological events, such as abnormal phosphorylation, inclusion formation, and assembly propagation.Globally, the present work unveils a strong implication of highly sulfated HS in tau pathology associated to AD and related tauopathies, and opens a wide array of novel research pathways to deepen into the characterization of tau /HS interplay and its pathophysiologic consequences. In addition, it suggests alternative pharmacological targets that could bring some hope in finding an effective treatment for AD.

A síntese noturna de melatonina pela glândula pineal é inibida por padrões moleculares associados à patógenos ou à danos, como por exemplo lipopolissacarídeo (LPS) ou peptídeo β-amilóide. A interação destas moléculas com receptores toll 4 (TLR4) ativa o eixo imune-pineal, favorecendo a migração de leucócitos para o local da injúria. Heparan sulfato (HS) é um glicosaminoglicano da matrix extracelular que por dano tecidual, inflamação generalizada ou migração de células tumorais, liberam dissacarídeos que podem ligar a TLR4, levando a formação de uma resposta inflamatória. Avaliamos se HS poderia prejudicar a atividade da melatonina. HS é capaz de inibir a síntese noturna de melatonina, através da supressão da expressão gênica e do conteúdo enzimático de acetilserotonina O-metiltransferase (ASMT). Este efeito é modulado pela interação de HS com TLR4, mas não envolve a via de translocação nuclear de NF-κB. Estes dados sugerem que um aumento de moléculas de HS na matriz da glândula pineal é traduzido a todo o organismo por uma redução no pico noturno de melatonina. / The nocturnal synthesis of melatonin by the pineal gland is inhibited by pathogen or damage-associated molecular patterns, such as lipopolysaccharide (LPS) and β-amyloid peptide. The interaction of these molecules with toll like receptors 4 (TLR4) activates the immune-pineal axis, favoring the migration of leukocytes for the site of lesion. Heparan sulfate (HS), a glycosaminoglycan of the extracellular matrix, that in case of tissue injury, generalized inflammation or migration of tumor cells, releases disaccharide, which can bind to TLR4 triggering an inflammatory response. Here we evaluated if HS could impair nocturnal melatonin activity. HS is capable of inhibit the melatonin synthesis by the suppression of the gene expression and enzymatic content of acetylserotonin O-methyltransferase (ASMT). This effect is modulated by the interaction of HS with TLR4, but does not involve the NF-κB nuclear translocation pathway. This data suggest that the increase in HS in pineal gland matrix is translated to the whole organism by a reduction in the nocturnal melatonin peak.