USING SYNTHETIC APPROCHES TO GLYCOCONJUGATES TO UNDERSTAND CARBOHYDRATE-MEDIATED BIOCHEMICAL INTERACTIONS
Tesi di Dottorato
Data di Pubblicazione:
2014
Citazione:
USING SYNTHETIC APPROCHES TO GLYCOCONJUGATES TO UNDERSTAND CARBOHYDRATE-MEDIATED BIOCHEMICAL INTERACTIONS / M. Vetro ; tutor: D. Colombo ; coordinator: F. Bonomi. Università degli Studi di Milano, 2014 Dec 18. 27. ciclo, Anno Accademico 2014. [10.13130/vetro-maria_phd2014-12-18].
Abstract:
This PhD Thesis deals with the synthesis of carbohydrates derivatives as analogues of natural compounds and their biological evaluation as tools for the study of biochemical regulatory pathways.
Carbohydrates, together with proteins, nucleic acids and lipids, are the building blocks on which complex living systems are based. This spectacular class of compounds acts as energetic sources, signaling regulators and components of cell surface. So, they are involved in many biological processes essential for the living cell, as immune response, inflammation, cell growth, cell-cell adhesion and so forth. The possibility to develop biochemical tools based on carbohydrates structures could be used to explain their functional role in many of these mechanisms and how to intervene to conceive new drugs systems for the treatment of several pathologies like cancers and bacterial infections, generally due to altered carbohydrate-mediated interactions.
The topic of this PhD thesis can be divided into two parts. The first one, composed by Chapter 1, 2 and 3, deals with the synthesis of glycosylglycerols ligands of Akt, a protein kinase overexpressed in many cancer cells, while the second part, resumed in Chapter 4, is oriented to the study of the opportunity to employ gold nanoparticles as alternative carriers for saccharide antigens in the vaccinology field.
Protein kinase are enzymes involved in the regulation of many crucial cellular processes like proliferation, differentiation and apoptosis [1]. Among them, the serine/threonine protein kinase B, also known as Akt, plays a key role as a component of the phosphoinositide 3-kinase (PI3K)-Akt-mTOR axis, which is implicated in aberrant tumor cell signaling. Inappropriate activation of the Akt kinase is a common event in human tumors making Akt a critical player in cell survival and, consequently, inhibitors that target Akt are potentially relevant for cancer therapy.
Akt is a soluble cytosolic protein composed of three parts, a N-terminal pleckstrin homology (PH) domain, a central catalytic kinase domain and a C-terminal regulatory domain [2]. The key second messenger phosphatidylinositol 3,4,5 triphosphate [PtdIn(3,4,5)P3 or PIP3], generated by the phosphatidylinositol-3 kinase (PI3K), binds to the PH domain inducing a conformational change of Akt which exposes two site of phosphorylation, specifically threonine 308 and serine 473. Their phosphorylation results in a fully activation of Akt that dissociates from the plasma membrane and can phosphorylate many substrates in the cytoplasm and nucleus [3].
The structure of the phosphatidylinositol PIP3, the natural ligand of Akt PH domain, is composed by an inositol, with a phosphate group in position 3 and a glycerol moiety in position 1 carrying long acyl chains.
Sulfoquinovosylacylglycerol (SQDG) analogues, synthesized in our laboratory, show structural features similar to PIP3, as an acylglycerol portion and a negative head. Furthermore the inositol ring can be easily reconducted to a glucose scaffold in which the pyranosidic oxygen replaces the hydroxyl group in position 2 of the inositol. These likeness prompted us to evaluate them as potential Akt inhibitors both in vitro and in vivo. An ELISA test was performed and the obtained results demonstrated the ability of our compounds to inhibit the Akt. In particular, the presence of the anionic group and a long chain lipophilic portion were necessary for their activity. The most active in vitro compounds were also tested for their antiproliferative activity on cell systems confirming these preliminary results.
Following our interest in the research of potential Akt inhibitor able to bind selectively the PH domain, we decided to further explore the potentiality of different anionic glyc
Tipologia IRIS:
Tesi di dottorato
Keywords:
Protein Kinase B; Akt; cancer; glycolipids; saccharide; carbohydrates; antigen; capsular polysaccharide; nanoparticles; gold nanoparticles
Elenco autori:
M. Vetro
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