The combat against viral diseases has been, and still is, a major challenge in the field of drug development. Viruses are intracellular parasites that use the host cell ma-chinery for their replication and release. Therefore it is difficult to target and destroy the viral particle without disturbing the essential functions of the host cell. This thesis describes studies towards antiviral agents targeting adenovirus type 37 (Ad37), which causes the severe ocular infection epidemic keratoconjunctivitis (EKC). Cell surface oligosaccharides serve as cellular receptors for many pathogens, including viruses and bacteria. For EKC-causing adenoviruses, cell surface oligo-saccharides with terminal sialic acid have recently been shown to be critical for their attachment to and infection of host cells. The work in this thesis support these re-sults and identifies the minimal binding epitope for viral recognition. As carbo-hydrate–protein interactions in general, the sialic acid–Ad37 interaction is very weak. Nature overcomes this problem and vastly improves the binding affinity by presenting the carbohydrates in a multivalent fashion. Adenoviruses interact with their cellular receptors via multiple fiber proteins, whereby it is likely that the ideal inhibitor of adenoviral infections should be multivalent. This thesis includes design and synthesis of multivalent sialic acid glycoconjugates that mimic the structure of the cellular receptor in order to inhibit adenoviral attachment to and infection of human corneal epithelial (HCE) cells. Synthetic routes to three different classes of sialic acid conjugates, i.e. derivatives of sialic acid, 3’-sialyllactose and N-acyl modified sialic acids, and their multivalent counterparts on human serum albumine (HSA) have been developed. Evaluation of these conjugates in cell binding and cell infectivity assays revealed that they are effective as inhibitors. Moreover the results verify the hypothesis of the multivalency effect and clearly shows that the power of inhibition is significantly increased with higher orders of valency. Potential inhibi-tors could easily be transferred to the eye using a salve or eye drops, and thereby they would escape the metabolic processes of the body, a major drawback of using carbohydrates as drugs. The results herein could therefore be useful in efforts to develop an antiviral drug for treatment of EKC.

The boronic acid functional group is known to bind compounds with the diol group tightly and reversibly in aqueous environment and has been used as a recognition moiety for the design of carbohydrate sensors. The first chapter of the dissertation studies the synthesis and substitution effect on the affinity and selectivity of a known boronic acid-based glucose sensor. In such a sensor design effort, the availability of a signaling event, whether it is fluorescence or UV, is crucial. The second chapter studies the detailed mechanism on how a well-known fluorescent boronic acid compound changes fluorescent properties upon binding. A new mechanism has been established which corrected a decade old mistake. In the third chapter, a series of boronic acid-based sensors were designed and synthesized for sialic acid, which is part of tetrasaccharide found on many cell surface carbohydrates. Such sialic acid sensors could be very useful for the development of new type of anti-influenza therapy. The fourth is on the design and synthesis novel and selective inhibitors for phosphodiesterase 4 (PDE4), which are potential anti-asthma agents.

In the heart, electrical signaling is responsible for its rhythmicity and is necessary to initiate muscle contraction. The net electrical activity in a cardiac myocyte during a contraction cycle is observed as the action potential (AP), which describes a change in membrane potential as a function of time. In ventricular cardiac myocytes, voltage-gated sodium channels (Nav) and voltage-gated potassium channels (Kv) play antagonistic roles in shaping the AP with the former initiating membrane depolarization and the latter repolarizing it. Functional changes in the primary cardiac Nav isoform, Nav 1.5, or any one of the many Kv isoforms expressed in the ventricle, as evidenced by those characterized in various congenital and/or acquired etiologies, can lead to severe cardiac pathologies. Nav and Kv are large transmembrane proteins that can be extensively post-translationally modified through processes that include glycosylation. The sequential glycosylation process typically ends with negatively charged sialic acid residues added through trans-Golgi sialyltransferase activity. Sialyltransferases belong to a much larger group of glycogene products that number in the hundreds and are responsible for creating a complex and variable glycan profile (glycome) unique to different cell types and tissues. Sialic acids impact Nav and Kv function likely by contributing to the extracellular surface potential and thereby causing channels to gate following smaller depolarizations. Additionally, developmentally regulated sialylation contributes to cardiac myocyte excitability in the neonatal mouse atria. However, little is understood concerning how the glycosylation machinery (glycogene products) influences cell and tissue electrical signaling. The sialytransferase Β-galactoside α-2,3-sialyltransferase 4 (ST3Gal4) adds sialic acids to galactose residues of N- and O-linked glycans through α-2,3-linkgages. ST3Gal4 is uniformly expressed throughout the chambers and developmental stages of the heart and therefore is likely a useful target to question whether and how glycosylation impacts these events. Additionally, diseases of glycosylation often cause symptoms that are consistent with changes in excitability that include arrhythmias and seizures. Congenital disorders of glycosylation lead to variably reduced glycoprotein and glycolipid glycosylation. However, because sialic acids are typically the terminal residues added to glycan structures, disease-related reduced glycosylation often leads to fewer sialic acids being attached. In addition, Chagas disease, which results in pathological changes in cardiac electrical function, may reduce sialic acids directly. Because of this, the ST3Gal4-/- strain was also used to investigate the role of glycosylation in the pathological cardiac electrical remodeling often associated with these diseases. The methodologies included cellular, tissue and whole-animal electrophysiology as well as biochemical assays. The data indicate that deletion of ST3Gal4 significantly affects Nav sialylation and gating with no change in maximum current density or protein expression. ST3Gal4 deletion also depolarizes the activation gating of both voltage-dependent kinetic components of repolarization found in the mouse ventricle: Ito and IKslow; however unlike the effect on INa, ST3Gal4 gene deletion causes a reduction in the peak IK density. Protein expression of the putative Kv isoforms responsible for Ito and IKslow was variably affected by ST3Gal4 gene deletion with Kv1.5 and Kv4.2 demonstrating no differences in protein densities. Contrastingly, a small but significant reduction in Kv2.1 protein from ST3Gal4-/- ventricular tissue was observed. In addition to effects on Nav and Kv activity, ST3Gal4 expression is necessary for normal cellular electrical signaling as demonstrated by a reduction in cellular refractory period and alterations in AP waveforms that include a slowing of cellular conduction and an extension of AP duration in ventricular myocytes from ST3Gal4-/- mice. Concurrent with aberrant excitability at the cellular level, the ST3Gal4-/- left ventricular epicardium demonstrated a reduced refractory period and was more susceptible to arrhythmias as observed through optical mapping studies. Additionally, ECGs of ambulatory ST3Gal4-/- mice demonstrated that deletion of the gene causes modest aberrant conduction under basal conditions and, in preliminary studies, appears to increase susceptibility to arrhythmias following a cardiac challenge, in the form of a low dosage of the Β-adrenergic agonist isoproterenol, suggesting a reduction in repolarization reserve in ST3Gal4 hearts. Based on the data reported here, it is apparent that relatively minor perturbations in the cardiac glycome cause significant changes in cardiac electrical signaling. These data highlight the role of glycosylation in normal physiology and underscore it as an important mediator in diseases where it may be altered.

Submitted by Fabio Sobreira Campos da Costa (fabio.sobreira@ufpe.br) on 2016-12-01T12:59:09Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) DISSERTAÇÃO - NEUSA LYGIA VILARIM PEREIRA.pdf: 830371 bytes, checksum: 5b2e17eefc8840d24aea2dfad45d93c0 (MD5) / Made available in DSpace on 2016-12-01T12:59:09Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) DISSERTAÇÃO - NEUSA LYGIA VILARIM PEREIRA.pdf: 830371 bytes, checksum: 5b2e17eefc8840d24aea2dfad45d93c0 (MD5) Previous issue date: 2016-03-22 / CNPq / O ácido siálico está presente nos leites na forma de ácido N-acetilneuramínico (Neu5Ac) e ácido N-glicolilneuramínico (Neu5Gc), desempenhando uma série de benefícios à saúde humana. O soro de queijo caprino é um bioproduto da fração solúvel do leite, obtido através da coagulação da caseína. É considerado importante para a indústria de alimentos, como ingrediente, sendo responsável por 55% de todos os nutrientes do leite. Neste estudo, objetivouse quantificar, pela primeira vez na literatura, o ácido siálico presente naturalmente no soro de queijo caprino por diferentes processos de coagulação láctea. O leite utilizado foi obtido de cabras da raça Saanen e submetidos ao processamento de coagulação enzimático e misto (enzima + cultura starter) para obtenção do soro, que foi acondicionado e congelado, sendo parte liofilizado. A identificação e quantificação do ácido siálico foi realizada por Cromatografia Líquida de Alta Eficiência por detector de fluorescência modelo RF-20A. A concentração desse nutriente variou de 23,5 a 292,1 mg/L. Foi verificado que a coagulação enzimática preserva o ácido siálico (Neu5Gc e Neu5Ac) mais eficientemente do que a coagulação mista, pois as bactérias da cultura starter possibilitaram a redução dos nutrientes presentes no soro para desempenharem o seu metabolismo, assim o ácido siálico presente como glicoconjugado, também foi reduzido. De acordo com os resultados obtidos, pode-se concluir que o soro de queijo caprino apresenta um potencial funcional, visto que contém uma quantidade relevante do nutriente estudado. / Sialic acid is present in milk in the form of N-acetylneuraminic acid (Neu5Ac) and Nglycolylneuraminic acid (Neu5Gc), performing a lot of benefits to human health. Goat cheese whey is a dairy byproduct from the soluble fraction obtained by casein coagulation. It is considered important for the food industry, as an ingredient, accounting for 55% of all milk nutrients. This study aimed to quantify the sialic acid present naturally in the goat cheese whey by different milk coagulation processes. The milk was obtained from Saanen goats and subjected to processing enzymatic and mixed coagulation (enzyme + starter culture) to obtain the whey, which was prepared and frozen, and part of it was lyophilized. The identification and quantitation of sialic acid was accomplished by High Performance Liquid Chromatography fluorescence detector RF-20A model. The sialic acid concentration ranged from 23.5 to 292.1 mg / L. It has been found that enzimatic coagulation preserves the sialic acid (Neu5Ac and Neu5Gc) more efficiently than mixed coagulation, because the bacterias of starter culture allowed the reduction of nutrients present in the whey to perform their metabolism, as well sialic acid present as glycoconjugate it was also reduced. According to the results, concluded that goat cheese whey has a functional potential, since it contains a significant quantity of the nutrient studied.

Submitted by Irene Nascimento (irene.kessia@ufpe.br) on 2017-03-24T17:41:49Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Dissertação Mestrado - Tiago Barros Santos Malta.pdf: 8207831 bytes, checksum: a5e3ee5357f988c47072c9481326377e (MD5) / Made available in DSpace on 2017-03-24T17:41:49Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Dissertação Mestrado - Tiago Barros Santos Malta.pdf: 8207831 bytes, checksum: a5e3ee5357f988c47072c9481326377e (MD5) Previous issue date: 2016-02-25 / CAPES, CNPQ, FACEPE / O câncer de mama feminino é o segundo tipo de câncer mais frequente no mundo, com aumento de incidência de 22% a cada ano. Estudos nas últimas décadas revelaram que a transformação maligna está associada a uma variedade de células com padrões de glicosilação alterados, como por exemplo a sialilação. Os ácidos siálicos tem sido relacionados à iniciação e progressão do câncer, tendo assim implicações potenciais na prevenção, diagnóstico e tratamento da doença. Este trabalho avaliou a expressão fenotípica de ST3Gal-I, através da imunohistoquímica, e o perfil de ácido siálico, através da histoquímica com lectinas usando Maackia Amurensis agglutinin II (MAA), em tecidos mamários diagnosticados com fibroadenoma (n=59), carcinoma ductal in situ (CDIS, n=40), carcinoma ductal invasivo (CDI, n=50) e carcinoma lobular (CL, n=42). Todos os tipos de lesões de mama apresentaram alta imunopositividade à ST3Gal-I, sendo observada uma expressão em 93,2% dos casos de Fibroadenoma, 92,5% de CDIS, 96% dos casos CDI e 85,2% de CL. As células apresentaram um padrão de marcação citoplasmático e perinuclear com relação à ST3Gal-I. Diferentes distribuições de resíduos de ácido siálico ⍺2,3-ligados, com um padrão de marcação predominantemente citoplasmático e membranar, foram observados nas lesões de mama estudadas. Os casos de fibroadenoma apresentaram o menor percentual de sialilação entre as lesões analisadas (47,5%), enquanto os de CDI o maior pecentual (98%). Embora este estudo não tenha mostrado diferença significativa na expressão de ST3Gal-I entre as lesões de mama, alterações representativas na presença de ácidos siálicos entre fibroadenoma e lesões malignas (p<0,0001), e também entre CDIS e CDI (p = 0.037) foram notadas. Não foram encontradas correlações significativas entre as expressões de ST3Gal-I e MAA, os marcadores de rotina e as características clinico-histopatológicas dos pacientes. Os resultados indicam uma distribuição particular de ácidos siálicos ⍺2,3-ligados nas células mamárias entre as lesões estudadas sugerindo seu envolvimento na progressão/manutenção do câncer de mama. / The female breast cancer is the second most common type of cancer in the world, with increased incidence of 22% every year. Recent studies in recent decades have revealed that the malignant transformation is associated with a variety of cells with altered glycosylation patterns such as sialylation. Sialic acids have been demonstrated to participate in cancer initiation and progression, thus has potential implications for cancer prevention, diagnosis and treatment. This study evaluated the phenotype expression of ST3Gal-I using immunohistochemistry and the sialic acid residues profile by histochemistry with Maackia amurensis agglutinin II (MAA) in mammary tissues diagnosed as fibroadenoma (n=59), ductal carcinoma in situ (DCIS, n=40), invasive ductal carcinoma (IDC, n=50) and lobular carcinoma (LC, n=42). All types of breast lesions showed high ST3Gal-I immunopositivity, its expression was observed in 93.2% cases of Fibroadenoma, 92.5% of DCIS, 96% of IDC and 85.2% cases of LC. The cells ST3Gal-I staining pattern was mainly cytoplasmatic and perinuclear. The MAA staining in breast lesions showed a diffuse cytoplasmatic and membrane pattern with different distribution of ⍺2,3-linked sialic acids among the lesions studied, fibroadenoma cases showed the lowest percentage among the analyzed lesions (47.5%) while IDC showed the highest (98%). Although this study did not show a significant difference in expression of ST3Gal-I among all lesions, representative alterations in sialic acid content between fibroadenoma and malignant lesions (p<0.0001), and also between CDIS and CDI (p=0.037) were observed. No significant correlations were found between the expressions of ST3Gal-I and MAA, routine markers and clinical-histopathological characteristics of the patients. Results indicate different distribution of ⍺2,3-linked sialic acids on the cells of the studied lesions which seems to be involved in breast cancer progression and/or maintenance.

Dilated cardiomyopathy (DCM) is the third most common cause of heart failure, often associated with arrhythmias and sudden cardiac death if not controlled. Metabolic and/or environmental factors, such as alcohol abuse, obesity, diabetes and Chagas disease, alter glycoprotein glycosylation, can lead to DCM. Inherited genetic disease, such as the human congenital disorders of glycosylation (CDG), causes multi-system manifestations including DCM. Non-congenital changes in glycosylation are also occurred in humans with and in animal models of DCM and heart failure. However, mechanisms responsible for glyco-dependent DCM are not understood. Here we sought to investigate the impact of sialylation and N-glycosylation in cardiac function. Partial reduction of N-α2,3-sialylation achieved through ST3Gal4 deletion (ST3Gal4-/-) led to adult late-onset DCM. The DCM symptoms progressed gradually, developing thinner left ventricular walls and dilation of all four chambers by 18-month old, but with preserved systolic function. Transverse aortic constriction (TAC) was used as a chronic stressor on 16-20 week old mice to determine whether the ability of the ST3Gal4-/- heart to compensate against pathologic insult is compromised. TAC’d ST3Gal4-/- mice presented with insufficient hypertrophy and reduced systolic function that deteriorated into congestive HF within six weeks post-surgery, while constricted WT hearts remained well-adapted throughout (ejection fraction, ST3Gal4-/-=34±5.2%; WT =53.8±7.4%; p<0.05).Calcineurin expression was decreased in ST3Gal4-/- (compared to TAC’d WT), contributed to the maladaptation of TAC’d ST3Gal4-/-. In order to better understand the role of glycosylation on cardiac function, we generated a cardiomyocyte specific knockout (αMHC-Cre) of glycosyltransferase responsible for synthesizing complex and hybrid N-glycans, Mgat1, (Mgat1CKO). Similar to but much more severe than that observed in ST3Gal4-/-, Mgat1CKO developed early-onset of DCM, late adult mortality, severely impaired cardiac systolic and diastolic function and frequent arrhythmias. Marked sex-difference in cardiac phenotype was observed in this autosomal gene (Mgat1) deletion, with male Mgat1CKO more severely affected. Both ST3Gal4 and Mgat1 did not participate in murine cardiogenesis, evidenced by normal litter size, Mendelian distribution of genotypes, no septal defect or vessel deformation under autopsy or echocardiography. In conclusion, we provided here the first and direct evidence of desialylation-elicited idiopathic dilated cardiomyopathy (DCM), reporting the cardiac phenotype of ST3Gal4-/-and cardiac-specific knockout of Mgat1. Our data showed sialylation and complex N-glycosylation are essential for cardiac function, and reduced N-glycosylation or sialylation leads to DCM development, contractile dysfunction and arrhythmia.

No description available.

Intratumor heterogeneity poses a significant challenge for the diagnosis and treatment of patients with breast cancer because distinct sub-populations of tumor cells contribute significantly more to therapy resistance and tumor recurrence than others. Consequently, understanding the mechanisms that contribute to this heterogeneity and identifying sub-populations responsible for aggressive behavior is a significant and timely problem. Considerable evidence indicates that a subpopulation of tumor cells with stem/progenitor-like characteristics, termed cancer stem cells (CSCs), is responsible for therapy resistance and recurrence, sparking interest in characterizing novel biomarkers and therapeutic targets for this aggressive population of cells. Unfortunately, CSCs share many protein markers with normal mammary stem/progenitor populations, minimizing potential targets for diagnostic and therapeutic purposes. Therefore, in my thesis research, I investigated novel ways to identify CSC populations based on their glycome. I observed that breast CSCs have a unique glycosylation pattern that can be used to distinguish them from other tumor populations. Specifically, I discovered a novel α2,3 sialoglycan on Core2 O-linked glycans expressed on CSCs that can identified using the lectin SLBR-N. I found that SLBR-N can be used to distinguish CSCs from bulk tumor cells in multiple in vitro and in vivo models. I also discovered that the CSC marker, CD44s, expresses O-linked α2,3 sialoglycan and that this glycan alters CD44s function by promoting the activation of the PDGFRβ/STAT3 pathway. In contrast, the fucosyltransferase FUT3 and its glycan sialyl Lewis X (sLeX) are expressed on non-CSCs and they function to impede stemness by inhibiting CD44s-mediated PDGFRβ/STAT3 signaling. In summary, this thesis provides insights into glycan heterogeneity in breast cancer and novel ways to identify CSCs using the glycome.

Polysialylated NCAM (polySia-NCAM) is re-expressed in a number of tumours, including small cell lung carcinoma and neuroblastoma and is strongly associated with aggressive, invasive and metastatic tumours in the clinic. SiRNA knockdown of the polysialyltransferases (polySTs), the enzymes responsible for polysialylation of neural cell adhesion molecule (NCAM), has been shown to abolish cell migration. PolySia-NCAM is thus a highly attractive novel therapeutic target. A library of potential polyST inhibitors has been synthesised, using substrate-based design and computational chemistry. Compounds synthesised include N-acylmannosamine analogues, thio-linked CMP-sialic acid analogues, N-acyl modified sialic acids and compounds incorporating elements of both approaches. Novel methodology development in the synthesis of many of the compounds is described, notably a novel route to N-acyl sialosides. In addition, compounds identified from in silico screening were considered. Routes to synthesis and isolation of analogues of biologically active compounds are described. Using an enzyme assay, compounds were evaluated for their ability to reduce polySia synthesis through polyST inhibition. Effects of agents on polySia expression in cells, and the ability of compounds to reduce cell migration in vitro was studied using a wound healing ‘scratch assay’. The data from these experiments revealed a number of potent modulators of polySia assembly and their efficacy in reducing cell migration, as well as the limits of the biosynthetic pathway to accept unnatural sialic acid precursors. This is the first example of polyST inhibition modulating tumour cell migration, and points to the potential of the polysialyltransferases as a therapeutic target in metastatic tumours. / EPSRC and BACR / The full text will be available at the end of the extended embargo: 5th March 2027

No description available.