Analýza úlohy vybraných regulátorů endocytózy v signální dráze proteinu Wnt

Signální dráha proteinu Wnt se značnou měrou podílí na ontogenetickém vývoji a homeostázi ve většině mnohobuněčných organismů. Její důležitost je podtržena její konzervovaností v evoluci a také širokým spektrem chorob způsobených její deregulací. Signální dráhu Wnt lze pro názornost rozdělit na dvě poloviny. V první jsou popsány procesy, důležité pro vznik a sekreci Wnt ligandu ve Wnt produkujících buňkách a v druhé procesy, které se odehrávají při transdukci Wnt signálu v buňkách přijímacích. Důležitým procesem v obou typech buněk je endocytóza. Regulací procesu endocytózy je zprostředkovaně regulován výsledek signalizace proteinu Wnt. V této práci byla pro charakterizaci nového regulátoru signální dráhy Wnt na úrovni endocytózy použita jako modelový organismus hlístice Caenorhabditis elegans (háďátko obecné). Tímto novým regulátorem je protein kináza SEL-5.. SEL-5 kináza patří do rodiny NAK kináz a její funkce se zdá být konzervována napříč evolucí. S využitím informací o lidském SEL-5 homologu AAK1 z dostupných databází byla předběžně popsána role SEL- 5 v regulaci signalizace Wnt u háďátka a navrženy experimenty, které by nám umožnily podrobněji prozkoumat jeho roli v této signální dráze. Popsali jsme genetické interakce sel-5 s některými komponenty retromerového komplexu a zjistili, že sel-5...Wnt signalling pathway is indispensable for a proper development and homeostasis in most of the multicellular organisms. Its evolutionary conservation and wide spectrum of diseases caused by its improper regulation only underscores its importance. Wnt signalling pathway can be conveniently divided into two halves. The first one covers processes that take place in Wnt ligand producing cells and the second one includes Wnt signal transduction in Wnt receiving cells. One of the vital steps in both types of cells is the process of endocytosis. Via regulation of this process, outcome of Wnt signalling itself is regulated. In this work, nematode Caenorhabditis elegans was used as a model organism to characterize new regulator of the Wnt signalling pathway which acts at the level of endocytosis. This new regulator described here is SEL-5 protein kinase. SEL-5 protein kinase belongs to a NAK kinase family and its function seems to be conserved throughout evolution. Its role in Wnt signalling of C. elegans was estimated by mining database information about its human homolog AAK1 and based on these information experiments were designed that would allow detailed investigation of its involvement in this pathway. Genetic interaction of sel-5 with components of the retromer complex was uncovered and it was...Department of Cell BiologyKatedra buněčné biologiePřírodovědecká fakultaFaculty of Scienc

Fosfoinositidy a jejich efektory v regulaci signální dráhy proteinu Wnt

Fosfoinositidy představují pouze malou část celkového množství lipidů v buněčných membránách. Přesto je jejich činnost zprostředkovaná proteinovými efektory nezbytná pro buněčnou signalizaci, vezikulární transport, pohyb buňky a jiné důležité procesy v životě buňky. Tato bakalářská práce popisuje funkci fosfoinositidů ve Wnt signální dráze. Při Wnt signalizaci je mnoho momentů kdy je nezbytná spolupráce s fosfoinositidy. Retrográdní transport Wntless molekuly (Wls) z plazmatické membrány zpět do Golgiho aparátu nebo internalizace Wnt receptorů v buňkách citlivých vůči Wnt signalizaci jsou pouze dva příklady. Oba procesy jsou přísně regulovány a poruchy funkce enzymů zpracovávajících fosfoinositidy může způsobit deregulaci těchto procesů, eventuálně deregulaci Wnt signální dráhy. Jelikož je deregulace Wnt signální dráhy známá příčina vážných nemocí včetně rakoviny, pochopení interakcí mezi fosfoinositidy a Wnt signalizací může pomoci vývoji nových strategií v léčbě těchto chorob.Phosphoinositides (PIs) make up only a small proportion of overall amount of lipids in cell membranes. However, their function mediated through protein effectors is indispensable for cell signaling, vesicular trafficking, cell movement and other important aspects of cellular life. In this bachelor thesis function of PIs is described in relation to Wnt signaling pathway. Proper execution of several steps of the Wnt signaling pathway requires the presence of PIs. Retrograde transport of Wntless (Wls) from the plasma membrane (PM) back to the Golgi apparatus (GA) in Wnt producing cells or internalization of Wnt receptors in Wnt receiving cells are only two examples. All processes are tightly regulated and malfunction of enzymes processing PIs can cause their deregulation resulting in disruption of the Wnt signaling pathway. As deregulated Wnt signaling is a known cause of serious diseases including cancer, understanding the crosstalk between PIs and Wnt signaling could help in designing novel strategies for therapeutic intervention.Department of Cell BiologyKatedra buněčné biologiePřírodovědecká fakultaFaculty of Scienc

Incretin mimetics: a novel therapeutic option for patients with type 2 diabetes – a review

Type 2 diabetes mellitus is a metabolic disease associated with low quality of life and early death. The goal in diabetes treatment is to prevent these outcomes by tight glycemic control and minimizing vascular risk factors. So far, even intensified combination regimen with the traditional antidiabetes agents have failed to obtain these goals. Incretin mimetics are a new class of antidiabetes drugs which involve modulation of the incretin system. They bind to and activate glucagon-like peptide-1 (GLP-1) receptors on pancreatic beta-cells following which insulin secretion and synthesis are initiated. Since the compounds have no insulinotropic activity at lower glucose concentrations the risk of hypoglycemia – a well-known shortcoming of existing antidiabetes treatments – is low. Additionally, incretin mimetics have been shown to be associated with beneficial effects on cardiovascular risk factors such as weight loss, decrease in blood pressure and changes in lipid profile. Current clinical data on the two available incretin mimetics, exenatide and liraglutide, are evaluated in this review, focusing on pharmacology, efficacy, safety and tolerability. The review is built on a systematic PubMed and Medline search for publications with the key words GLP-1 receptor agonist, exenatide, liraglutide and type 2 diabetes mellitus up to January 2009

Future Perspectives on GLP-1 Receptor Agonists and GLP-1/glucagon Receptor Co-agonists in the Treatment of NAFLD

Along the obesity pandemic, the prevalence of non-alcoholic fatty liver disease (NAFLD), often regarded as the hepatic manifestation of the metabolic syndrome, increases worldwide representing now the prevalent liver disease in western countries. No pharmacotherapy is approved for the treatment of NAFLD and, currently, the cornerstone treatment is lifestyle modifications focusing on bodyweight loss, notoriously difficult to obtain and even more difficult to maintain. Thus, novel therapeutic approaches are highly demanded. Glucagon-like peptide-1 (GLP-1) receptor agonists (GLP-1RAs) are approved for the treatment of type 2 diabetes and obesity. They exert their body weight-lowering effect by reducing satiety and food intake. GLP-1RAs have also been shown to reduce liver inflammation and fibrosis. Furthermore, glucagon receptor agonism is being investigated for the treatment of NAFLD due to its appetite and food intake-reducing effects, as well as its ability to increase lipid oxidation and thermogenesis. Recent studies suggest that glucagon receptor signaling is disrupted in NAFLD, indicating that supra-physiological glucagon receptor agonism might represent a new NAFLD treatment target. The present review provides (1) an overview in the pathophysiology of NAFLD, including the potential involvement of GLP-1 and glucagon, (2) an introduction to the currently available GLP-1RAs and (3) outlines the potential of emerging GLP-1RAs and GLP-1/glucagon receptor co-agonists in the treatment of NAFLD

On the role of gallbladder emptying and incretin hormones for nutrient-mediated TSH suppression in patients with type 2 diabetes

Bile acids are possible candidate agents in newly identified pathways through which energy expenditure may be regulated. Preclinical studies suggest that bile acids activate the enzyme type 2 iodothyronine deiodinase, which deiodinates thyroxine (T(4)) to the biologically active triiodothyronine (T(3)). We aimed to evaluate the influence of bile acid exposure and incretin hormones on thyroid function parameters in patients with type 2 diabetes. Thyroid-stimulating hormone (TSH) and thyroid hormones (total T(3) and free T(4)) were measured in plasma from two human studies: i) 75 g-oral glucose tolerance test (OGTT) and three isocaloric (500 kcal) and isovolaemic (350 ml) liquid meals with increasing fat content with concomitant ultrasonographic evaluation of gallbladder emptying in 15 patients with type 2 diabetes and 15 healthy age, gender and BMI-matched controls (meal-study) and ii) 50 g-OGTT and isoglycaemic intravenous glucose infusions (IIGI) alone or in combination with glucose-dependent insulinotropic polypeptide (GIP), glucagon-like peptide 1 (GLP1) and/or GLP2, in ten patients with type 2 diabetes (IIGI-study). In both studies, TSH levels declined (P<0.01) similarly following all meal and infusion stimuli. T(3) and T(4) concentrations did not change in response to any of the applied stimuli. TSH levels declined independently of the degree of gallbladder emptying (meal-study), route of nutrient administration and infusion of gut hormones. In conclusion, intestinal bile flow and i.v. infusions of the gut hormones, GIP, GLP1 and/or GLP2, do not seem to affect thyroid function parameters. Thus, the presence of a ‘gut–thyroid–pituitary’ axis seems questionable