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Vesicular roles of Arp2/3 nucleation-promoting factors
Dostál, Vojtěch ; Libusová, Lenka (advisor) ; Malínský, Jan (referee) ; Befekadu, Asfaw (referee)
F-actin is involved in key aspects of vesicular traffic, such as membrane deformation, tubulation and vesicle motion. Branching of F-actin is mediated by Arp2/3 but this complex must first be activated by so-called nucleation-promoting factors (NPFs). These factors play an essential role in the decision where and when branched actin should form on the membrane surface. The thesis focuses on the mechanisms which underlie localization and activation of NPFs, especially in terms of the phosphoinositide composition of the vesicle membranes. I show that one of the NPFs, the WASH complex, does not exclusively depend on the retromer complex for its membrane anchoring, as previously theorized. Rather, its understudied subunit SWIP enables the complex to independently bind to the membrane. I also present data showing that the WASH complex has essential roles in maintaining lysosomal function. Additionally, I elucidate the function of another NPF known as WHAMM in the ERGIC compartment, showing that it depends on the presence of myotubularin 9 for its ability to form membrane tubules. The thesis improves our understanding of the interface between the actin cytoskeleton and intracellular membrane system.
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Fumarate hydratase as tumor suppressor
Kedrová, Kateřina ; Hansíková, Hana (advisor) ; Befekadu, Asfaw (referee)
1 Abstract Fumarate hydratase (fumarase, EC 4.2.1.2) catalyzes the reverse hydration of fumarate to S malate. In mammalian cells, it changes fumarate in the mitochondrial matrix as a part of the citric acid cycle and in the cytosol, where functions to metabolize fumarate the product of the degradation of some amino acids, of ammonia transformation to urea acid or of the purine nucleotide synthesis. . In human cells, fumarase is encoded by FH gene localized on chromosome 1 (1q42.1). The FH gene consists of 10 exons and encodes for a 510 amino acids-long protein including the N-terminal mitochondrial signal sequence. Germline heterozygous FH mutations were found in two autosomal dominant syndromes. These are multiple cutaneous and uterine leiomyomatosis (MCUL1 or MCL) and hereditary leiomyomatosis and renal cell cancer (HLRCC). In the most of tumors from these patients, loss of FH gene heterozygosity was also found. It has been suggested that fumarase acts as a tumor suppressor according to Knudson's two-hit hypothesis. The aim of the bachelor thesis was to study the activity and amounts of fumarase in a series of 22 samples of uterine leiomyomas from 22 young women patients (21-31 years) with sporadic uterine leiomyomas. As a control sample, uterine leiomyoma from a 38-year-old patient was used. Activity of...
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Study of transferrin as a marker of congenital disorders of glycosylation
Ondrušková, Nina ; Stiborová, Marie (advisor) ; Befekadu, Asfaw (referee)
Congenital disorders of glycosylation (CDG) represent a heterogeneous group of mul- tisystemic metabolic disorders which are caused by defects in biosynthetic pathways of glycoproteins. The screening test for N-glycosylation disorders is the analyses of sialylated isoforms of serum transferrin (Tf) by means of isoelectric focusing (IEF). Two distinct pathological IEF patterns of Tf are observed. A type I pattern is cha- racterized by a decrease of tetra- and an increase of di- and asialotransferrin, whereas a type II pattern shows in addition an increase of tri- and monosialotransferrin. The aims of diploma thesis were: 1) to evaluate reference range for spectrum of sialylated forms of Tf separated by IEF and 2) to perform biochemical and molecular analyses in three patients (P1-P3) with clinical suspicion for CDG. Serum and genomic DNA from three patients with clinical suspicion for CDG and family members of P1 were analysed. Sera from 99 healthy volunteers within the age range of 2-42 years served as a control group. Tf was analysed by IEF with direct immunofixation, SDS-PAGE and Western blot using specific antibody against human Tf (Dako). Profiles of Tf were quantified by AlphaEaseFC software (Alpha Innotech). Data were analysed by software STATISTICA 9.0 (StatSoft). TF a PMM2 genes were analysed...
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Changes in the composition and localization of gangliosides in cholestasis associated with other markers of pathological processes in hepatocytes.
Petr, Tomáš ; Muchová, Lucie (advisor) ; Mičuda, Stanislav (referee) ; Befekadu, Asfaw (referee)
This thesis is focused on the study of glycosphingolipids in the rat liver in different types of cholestasis and the effect of oxidative stress on changes in the composition and localization of gangliosides. First, it was necessary to optimize the immunochemical detection of glycosphingolipids. GM1 ganglioside was selected as a representative of a large glycolipid family. We found that minimum water content in the fixing solution was a key condition for fixation of histological sections. Optimized method of GM1 detection was subsequently used in in vivo experiments. We have demonstrated that estrogen-induced cholestasis characterized by high concentrations of bile acids and increased oxidative stress caused changes in the synthesis and distribution of liver gangliosides. HMOX induction is associated with a reduction in oxidative stress level and accompanied by normalization in GSL content. In experiments with obstructive cholestasis, we found that changes in the distribution and synthesis of gangliosides were not strictly specific to a particular type of cholestasis. We assume that it represents a general mechanism of hepatoprotection. We also confirmed the important role of bilirubin, product of HMOX reaction, in protection of hepatocytes against oxidative damage caused by high concentrations of...
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Site-directed mutagenesis of human cytochromes P450 family 1 and their interacting partners
Milichovský, Jan ; Martínek, Václav (advisor) ; Befekadu, Asfaw (referee) ; Souček, Pavel (referee)
Cytochromes P450 represent a large group of proteins metabolizing variety of substrates. Many of them are responsible for metabolism of xenobiotics including drugs and chemical carcinogens. Heme-protein cytochrome b5 is a single-electron donor cooperating with a NADPH:cytochrome P450 reductase and NADH:cytochrome b5 reductase 3 enzyme. Cytochrome b5 can affect the xenobiotic metabolism via modulation of the cytochromes P450 activity. One of the goals of the Ph.D. thesis was to utilize site directed mutagenesis of cytochromes P450 family 1 to elucidate the mechanism of their nitroreductase activity. Another aim was to study the interaction between cytochrome b5 and cytochromes P450 of the 1A subfamily using site directed mutagenesis on presumed protein-protein contact interface. Another goal was to utilize the combination of theoretical and experimental approaches to explain variance in the reduction state of several human cytochromes P450 heterologously expressed in intact bacterial cells. The results found in the thesis show that nitroreductase activity of CYP1A1, CYP1A2 and CYP1B1 is mediated by the presence of a particular hydroxyl group in their active centre. Single mutation introducing a hydroxyl group to the specific part of CYP1B1 active site to the active site turned on its artificial...
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Fumarate hydratase as tumor suppressor
Kedrová, Kateřina ; Hansíková, Hana (advisor) ; Befekadu, Asfaw (referee)
1 Abstract Fumarate hydratase (fumarase, EC 4.2.1.2) catalyzes the reverse hydration of fumarate to S malate. In mammalian cells, it changes fumarate in the mitochondrial matrix as a part of the citric acid cycle and in the cytosol, where functions to metabolize fumarate the product of the degradation of some amino acids, of ammonia transformation to urea acid or of the purine nucleotide synthesis. . In human cells, fumarase is encoded by FH gene localized on chromosome 1 (1q42.1). The FH gene consists of 10 exons and encodes for a 510 amino acids-long protein including the N-terminal mitochondrial signal sequence. Germline heterozygous FH mutations were found in two autosomal dominant syndromes. These are multiple cutaneous and uterine leiomyomatosis (MCUL1 or MCL) and hereditary leiomyomatosis and renal cell cancer (HLRCC). In the most of tumors from these patients, loss of FH gene heterozygosity was also found. It has been suggested that fumarase acts as a tumor suppressor according to Knudson's two-hit hypothesis. The aim of the bachelor thesis was to study the activity and amounts of fumarase in a series of 22 samples of uterine leiomyomas from 22 young women patients (21-31 years) with sporadic uterine leiomyomas. As a control sample, uterine leiomyoma from a 38-year-old patient was used. Activity of...
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Metabolism of and DNA Adduct Formation by Carcinogenic o-Anisidine and its Metabolite N-(2-Methoxyphenyl) hydroxylamine
Naiman, Karel ; Stiborová, Marie (advisor) ; Sofrová, Danuše (referee) ; Befekadu, Asfaw (referee)
CHARLES UNIVERSITY IN PRAGUE FACULTY OF SCIENCE DEPARTMENT OF BIOCHEMISTRY Metabolism of and DNA Adduct Formation by Carcinogenic o-Anisidine and its Metabolite N-(2-Methoxyphenyl)hydroxylamine Summary of Ph.D. Thesis RNDr. Karel Naiman Supervisor: Prof. RNDr. Marie Stiborová, DrSc. PRAGUE 2010 Introduction - 2 - INTRODUCTION Aromatic amines are potent toxic or carcinogenic compounds, presenting a considerable danger to the human population (NTP, 1978; IARC, 1982; Garner et al., 1984). They are widely distributed environmental pollutants found in workplaces (e.g. in chemical industry), in emissions from diesel and gasoline engines and on the surface of ambient air particulate matter (NTP, 1978; IARC, 1982), where they add to local and regional pollution (car exhausts, technological spills). Their toxicity and carcinogenicity has been widely examined, but the knowledge in metabolism of several aromatic amines and their physiological effects in humans are still incomplete. This is also the case of o-anisidine. 2-Methoxyaniline (o-anisidine, Fig. 1) is a potent carcinogen, causing tumours of the urinary bladder in both genders of F344 rats and B6C3F1 mice (NTP, 1978; IARC, 1982). The International Agency for Research on Cancer (IARC) has classified o-anisidine as a group 2B carcinogen (IARC, 1982), which is...
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Study of transferrin as a marker of congenital disorders of glycosylation
Ondrušková, Nina ; Stiborová, Marie (advisor) ; Befekadu, Asfaw (referee)
Congenital disorders of glycosylation (CDG) represent a heterogeneous group of mul- tisystemic metabolic disorders which are caused by defects in biosynthetic pathways of glycoproteins. The screening test for N-glycosylation disorders is the analyses of sialylated isoforms of serum transferrin (Tf) by means of isoelectric focusing (IEF). Two distinct pathological IEF patterns of Tf are observed. A type I pattern is cha- racterized by a decrease of tetra- and an increase of di- and asialotransferrin, whereas a type II pattern shows in addition an increase of tri- and monosialotransferrin. The aims of diploma thesis were: 1) to evaluate reference range for spectrum of sialylated forms of Tf separated by IEF and 2) to perform biochemical and molecular analyses in three patients (P1-P3) with clinical suspicion for CDG. Serum and genomic DNA from three patients with clinical suspicion for CDG and family members of P1 were analysed. Sera from 99 healthy volunteers within the age range of 2-42 years served as a control group. Tf was analysed by IEF with direct immunofixation, SDS-PAGE and Western blot using specific antibody against human Tf (Dako). Profiles of Tf were quantified by AlphaEaseFC software (Alpha Innotech). Data were analysed by software STATISTICA 9.0 (StatSoft). TF a PMM2 genes were analysed...
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