Plants have developed a number of ways how to minimise negative influence of the environment. As a consequence of stress action, plants carbohydrate metabolism is quite often influenced, esp. on the level of expression and activities of different enzymes and also several metabolites concentration. One of key enzymes of carbohydrate metabolism is invertase. The aim of this work was to find out, whether the activity of its isoforms (cytoplasmic, vacuolar and extracellular) in tobacco plants is influenced by Potato virus Y (PVY). It was shown, that activity of cytoplasmic invertase was not affected, but the activity of vacuolar and extracellular isoform was enhanced during potyviral infection. Hence, it is likely, that vacuolar and extracellular invertases are related to plant antiviral defence. The effect of PVY on other enzymes of carbohydrate metabolism and several metabolites content was studied. Activity of α-amylase and phosphorylase, starch-degrading enzymes, was strongly enhanced during potyviral infection. That is probably how plant cells get glucose, which is a key source of energy and metabolites for biosynthesis of different compounds. It may also serve as a signal molecule. Activity of other hydrolytic enzymes, β-glucosidase and β-hexosaminidase, was also slightly increased. There was no...

The primary goal of my thesis research was to characterize the basis for the hypersensitive response of glycogen phosphorylase to catecholamine stimulation in primary culture diabetic cardiomyocytes. Toward this goal, I have investigated several key regulatory sites in this signaling pathway which could promote the hypersensitive activation of phosphorylase. Specifically, I investigated (1) which adrenergic receptors are involved in mediating the hypersensitive response of glycogen phosphorylase to epinephrine stimulation; (2) whether the presence of fatty acid metabolites affects phosphorylase activation; (3) whether the hypersensitive response of phosphorylase results from altered signal transduction through the β-adrenergic receptor system or from a post-receptor defect; and (4) the potential role for phosphorylase kinase in mediating the hypersensitive response of phosphorylase to catecholamine stimulation. The basis for adrenergic receptor mediation of the catecholamine-induced activation of glycogen phosphorylase was investigated in adult rat cardiomyocytes isolated from normal and alloxan-diabetic animals. Cells derived from diabetic animals exhibited a hypersensitive response to epinephrine stimulation which was apparent 3 hours after cell isolation and was further enhanced upon maintenance of the myocytes in culture for 24 hours. Normal cells initially lacked the hypersensitive response to epinephrine stimulation although upon maintenance of these cells in culture for 24 hours, the hypersensitive response was acquired in vitro. To assess alpha- and beta- adrenergic mediation of the response, normal and diabetic cardiomyocytes were incubated with propranolol, a β-receptor antagonist, prior to direct α1receptor stimulation with phenylephrine. Both normal and diabetic myocytes failed to undergo activation of phosphorylase in 3 or 24 hour cell cultures. In addition, the effects of epinephrine on phosphorylase activation were completely inhibited by propranolol whereas prazosin, an α-receptor antagonist, was unsuccessful. This data suggests that the hypersensitive response of glycogen phosphorylase in normal and diabetic cardiomyocytes is solely mediated through β-adrenergic receptor activation. Since the accumulation of various fatty acid metabolites can affect certain enzymes and signal transduction pathways within the cell, the potential effect of various fatty acid metabolites on phosphorylase activation was investigated. To determine the potential effects of fatty acid metabolites on phosphorylase activation in cultured cardiomyocytes, normal and alloxan-diabetic cells were incubated with either carnitine or palmitoylcarnitine prior to stimulation with epinephrine. Pretreatment of cardiomyocytes with or without carnitine or palmitoylcarnitine for 3 or 24 hours before epinephrine stimulation failed to alter phosphorylase activation. The addition of exogenous carnitine in the absence and presence of insulin was also unsuccessful in attenuating the hypersensitive phosphorylase activation response in 3 and 24 hour, normal and alloxan-diabetic derived cardiomyocytes. To determine if carnitine palmitoyltransferase 1 (CPT-1) activity was responsible for the hypersensitive response of phosphorylase in the diabetic myocytes, both normal and diabetic myocytes were maintained for 3 and 24 hours in the absence and presence of etomoxir, a CPT-1 inhibitor. Subsequent activation of phosphorylase by epinephrine in normal and diabetic myocytes was unaltered in the presence of etomoxir. Collectively, these data fail to support a critical role for fatty acid metabolite involvement in the hypersensitive activation of glycogen phosphorylase in acute, alloxan-diabetic cardiomyocytes. To assess potential G-protein involvement in the response, normal and diabetic-derived myocytes were incubated with either cholera or pertussis toxin prior to hormonal stimulation. Pretreatment of cardiomyocytes with cholera toxin resulted in a potentiated response to epinephrine stimulation whereas pertussis toxin did not affect the activation of this signaling pathway. To determine if the enhanced response of phosphorylase activation resulted from an alteration in adenylyl cyclase activation, the cells were challenged with forskolin. After 3 hours in primary culture, diabetic cardiomyocytes exhibited a hypersensitive response to forskolin stimulation relative to normal cells. However, after 24 hours in culture, both normal and diabetic myocytes responded identically to forskolin challenge. The present data suggest that a cholera toxin sensitive G-protein mediates the hypersensitive response of glycogen phosphorylase to catecholamine stimulation in diabetic cardiomyocytes. This response, which is present in alloxan-diabetic cells, and is induced in vitroin normal cardiomyocytes, is primarily due to a defect at a post-receptor site. To assess the role of phosphorylase kinase in the hypersensitive activation of glycogen phosphorylase in the diabetic heart, phosphorylase kinase activity was measured initially in perfused hearts (to optimize the assay parameters) and subsequently in primary culture cardiomyocytes. Results from these experiments demonstrate that the present method for measuring phosphorylase kinase activity is a reliable indicator of the enzyme's activity in the heart, although the assay conditions must be further optimized before this system can be applied to the measurement of phosphorylase kinase activity in primary cultured cardiomyocytes.

Los cuerpos nucleares de Cajal (CBs) son estructuras nucleares implicadas en la biogénesis de ribonucleoproteínas nucleares y nucleolares de pequeño tamaño (snRNPs y snoRNPs) requeridas para el procesamiento nuclear de pre-mRNAs y pre-rRNAs, respectivamente. El CB concentra la proteína coilina, un marcador molecular de esta estructura, snRNPs, el factor de supervivencia de las neuronas motoras (SNM) y las proteínas que comparte con el nucleolo Nopp140 y fibrilarina. Los CB son estructuras dependientes de transcripción, pero los mecanismos de ensamblaje molecular de estos cuerpos nucleares son poco conocidos.En este estudio se utilizan métodos de inmunofluorescencia, expresión ectópica de proteínas del CB y métodos bioquímicos para analizar la importancia de dos modificaciones postraduccionales, la metilación de la coilina y la conjugación con SUMO1 del factor SMN para el ensamblaje molecular de los CBs. Se ha utilizado la línea celular MCF7 como un modelo de hipometilación endógena debido al déficit del gen MTAP. La hipometilación de la coilina conduce al desensamblaje de los CBs y a la relocalización nucleolar de la coilina no metilada. Este efecto revierte en células transfectadas que expresan el gen MTAPwt, indicando que el grado de metilación de la coilina marca su destino nuclear.Respecto a la importancia de la sumoilación en el ensamblaje de los CBs, hemos demostrado la existencia de un subtipo de CBs que concentran SUMO1 y la conjugasa de SUMO Ubc9. En neuronas, hemos detectado la presencia de SUMO durante la fase de reformación de CBs, en la respuesta al estrés. Los experimentos de inmunoprecipitación confirman la interacción de SUMO-1 con el factor SMN y demuestran que la lisina K119, portadora de una secuencia consenso de sumoilación, es esencial para la regulación del número de CBs. / Cajal bodies (CBs) are nuclear structures involved in the biogenesis of small nuclear and nucleolar ribonucleoproteins (snRNPs and snoRNPs) required for nuclear processing of pre-mRNAs and pre-rRNAs, respectively. CBs concentrate the protein coilin, a molecular marker of this structure, snRNPs, the survival of motor neurons factor (SMN) and proteins shared with the nucleolus Nopp140 and fibrillarin. CBs are transcription-dependent structures, but the mechanisms of molecular assembly of these structures are poorly understood.In this study we used inmunofluorescence, ectopic expresion of CB proteins and biochemical methods to analyze the importance of two posttranslational modifications, methylation of coilin and conjugation of SMN with SUMO1, for the molecular assembly of CBs. The cell line MCF7 has been used as a model of endogenous hypomethylation due to the lack of MTAP gene. Coilin hypomethylation leads to the disassembly of CBs and nucleolar relocation of unmethylated coilin. This effect reverses in transfected cells expressing the gene MTAPwt, indicating that the degree of methylation of coilin directs its nuclear destination.On the importance of sumoylation in the assembly of CBs, we have demonstrated the existence of a subset of CBs which concentrate SUMO1 and the SUMO1 conjugase Ubc9. In neurons, we detected the presence of SUMO1 during the reformation of CBs in response to stress. Immunoprecipitation experiments confirm the molecular interaction of SUMO1 with SMN and demonstrate that lysine 119, carrying the SMN sumoylation consensus sequence, is essential for regulating the number of CBs.

Indiana University-Purdue University Indianapolis (IUPUI) / Multiple sclerosis (MS) is a disabling disease that afflicts an estimated two million people worldwide. The disease is characterized by degradation of the myelin sheath that insulates neurons of the central nervous system manifesting as a heterogeneous collection of symptoms. Two enzymes, protein arginine deaminases type 2 and 4 (PAD2 and PAD4) have been implicated to play an etiologic role in demyelination and neurodegeneration by catalyzing a post-translational modification of arginine peptide residues to citrulline. The pathogenesis of MS is poorly understood, though vitamin D deficiency is a well-associated risk factor for developing the disorder. Using the experimental autoimmune encephalomyelitis (EAE) model of MS we demonstrate vitamin D treatment to attenuate over-expression of PAD 2 and 4 in the brain and spine during EAE. In addition, we identify two molecules produced by peripheral immune cells, IFNɣ and IL-6, as candidate signaling molecules that induce PAD expression in the brain. We demonstrate vitamin D treatment to inhibit IFNɣ mediated up regulation of PAD2 and PAD4 both directly within the brain and by modulating PAD-inducing cytokine production by infiltrating immune cells. These results provide neuroprotective rational for the supplementation of vitamin D in MS patients. More importantly, these results imply an epigenetic link between vitamin D deficiency and the pathogenesis of MS that merits further investigation.