Global ETD Search

1	Structural and Signaling Elements Important for the Efficient Degradation of BHMT through Macroautophagy Mercer, Carol A. 18 April 2007 (has links) No description available. Autophagy BHMT mTOR S6 kinase
2	Regulation of energy balance in Caenorhabditis elegans / Reglering av energibalans i Caenorhabditis elegans Sheng, Ming January 2015 (has links) Obesity is a medical condition in which excess body fat has been accumulated. It is most commonly caused by imbalance between energy intake and energy expenditure (lack of physical activity and lower metabolic rate, etc.). The control of energy metabolism involves multiple tissues and signalling pathways and there is a great need for further understanding of these different interactions. In this study, I use Caenorhabditis elegans to study these complex pathways at the level of a whole organism. The downstream target of mTOR, p70 S6 kinase (S6K), has been implicated in the phosphorylation of multiple substrates and the regulation of growth and metabolism. In this study the worm homolog of S6K, rsks-1, found to be important for fat metabolism. Previous work in our lab found that RSKS-1::GFP is expressed at high levels in a set of sensory neurons and upregulated in ASJ, ASE and BAG sensory neurons in starved worms or mutants with low insulin activity. In this study, I found that the upregulation of rsks-1 expression was affected by serotonin, but not by the other neurotransmitters. Combined with the result that rsks-1 is required for the expression of TGFβ and insulin in ASI, rsks-1 may control dietary sensing by affecting insulin and TGFβ signalling within nervous system. Quantification of fat accumulation by TLC/GC revealed that in comparison to wild type worms, rsks-1 mutants have more than two-fold higher levels of triglycerides. This was confirmed by FT-IR microspectroscopy analysis. rsks-1 mutants also contain disproportionately high levels of C16:1n9 and C18:1n9 lipids compared with wild type worms. Genetic analysis has shown that rsks-1 acts either downstream of, or in parallel to the insulin and TGFβ pathways to affect fat levels. My studies showed that rsks-1 affects fat metabolism by influencing mRNA levels of genes encoding proteins in the β-oxidation pathway. Combined with defects in dietary sensing, fatty acid absorption, fertility and mitochondria function, the loss of rsks-1 activity induced much more energy storage than wild type by making a profound metabolic shift. These results are consistent with the metabolomics data analysis. Tissue specific RNAi showed that rsks-1 was required in many different tissues to regulate fat metabolism. Taken together, it can be concluded that RSKS-1 activity is needed for co-ordination of metabolic states in C. elegans. In order to understand more about the physiology behind fat accumulation, I analysed a mutant, aex-5, that has significantly lowered lipid levels. I found that this defect is associated with a significant reduction in the rate at which dietary fatty acids are taken up from the intestinal lumen. The aex-5 gene, which encodes a Kex2/subtilisin-family, Ca2+-sensitive proprotein convertase, is required for a discrete step in an ultraradian rhythmic phenomenon called the defecation motor program (DMP). Combined with other results, we conclude that aex-5 and other defecation genes may affect fat uptake by promoting the correct distribution of acidity within the intestinal lumen. This dissertation also described how to use Fourier transform infrared (FT-IR) microspectroscopy to detect lipids, proteins and carbohydrates directly in single worm. In conclusion, in this thesis I have uncovered several components that play roles in dietary sensing, fatty acid synthesis, adiposity regulation and fatty acid absorption in C. elegans. C.elegans fat metabolism S6 Kinase FT-IR
3	Signalling mechanisms involved in the regulation of mammary protein synthesis by amino acids Alderson, Jon January 2000 (has links) The aim of this study was to develop an <I>in vitro</I> mammary model, based on rat mammary explants, which could be used to examine the effects of amino acid profile and concentration in the media on protein synthesis. Secondly, to ascertain whether these responses to amino acids, in particular leucine and α ketoisocaproic acid, were transmitted through the mTOR/p70 S6 kinase signalling pathway. Mammary explant protein synthesis was found to be stimulated up to twofold in response to graded levels of a complete mixture of amino acids (2 x and 4 x, normal rat plasma concentrations). The acute (1 h) stimulation of protein synthesis was at the level of translation. Inhibition of mTOR by rapamycin did not block the stimulation of protein synthesis by amino acids. In fact, when total amino acid concentrations were increased 0.5 to 4-fold, p70 S6 kinase activity decreased, despite the fact that protein synthesis was elevated up to 2.5 fold. When explants were incubated with either leucine or its transamination product α ketoisocaproic acid at 4 x normal levels in the presence of other amino acids (1 x), p70 S6 kinase activity was increased. There was a tendency for p70 S6 kinase activity to be blocked when transamination was inhibited. The failure to decrease protein synthesis by inhibition of transamination, despite the fact that p70 S6 kinase activity was inhibited, suggests that other translation factors may be more important in regulating mammary protein synthesis. This Phd thesis demonstrates a novel role for amino acids in mammary protein synthesis, whereby amino acids modulate the activity of the translation regulator p70 S6 kinase. In particular leucine and its transamination are important in the regulation of p70 S6 kinase activity. This provides the starting point for future studies exploring the role of translation factors in the regulation of mammary protein synthesis. 572
4	Sustained acidosis and phenylephrine activate the myocardial Na+/H+ exchanger through phosphorylation of Ser770 and Ser771 Coccaro, Ersilia 06 1900 (has links) The mammalian Na+/H+ exchanger isoform 1 (NHE1) is a ubiquitously expressed membrane protein that regulates myocardial intracellular pH. Inhibition of NHE1 prevents hypertrophy and reduces ischemia-reperfusion (I/R) injury in animal models. To understand the regulation of NHE1 in the myocardium by phosphorylation we constructed adenoviruses, which express wild type or mutant cDNA for NHE1. Additionally, wild type and mutant NHE1 had mutations Leu163Phe/Gly174Ser, which increases NHE1 resistance to EMD87580 (NHE1 inhibitor) by 100-fold. This allowed measurement of exogenous NHE1 activity while inhibiting endogenous NHE1 activity. We examined the effects of a series of mutations of phosphorylation sites in the cytosolic domain of NHE1. Sustained intracellular acidosis and phenylephrine caused an ERK-dependent activation of NHE1 activity and phosphorylation levels. We demonstrated that amino acids Ser770 and Ser771 were essential for activation of NHE1 activity in isolated rat cardiomyocytes by sustained intracellular acidosis and phenylephrine. Furthermore, mutation of Ser770 and Ser771 to Ala prevented increased NHE1 phosphorylation by sustained intracellular acidosis and phenylephrine. This was found to occur in an ERK-dependent manner. Taken together, our results demonstrate that both sustained intracellular acidosis and phenylephrine rapidly activate the NHE1 protein in isolated cardiac cells via an ERK-dependent pathway that acts on the common amino acids Ser770 and Ser771 of the C-terminal tail of NHE1. sodium hydrogen exchanger sustained acidosis phenylephrine myocardium extracellular regulated kinase 1/2 p90 risobomal S6 kinase
5	Sustained acidosis and phenylephrine activate the myocardial Na+/H+ exchanger through phosphorylation of Ser770 and Ser771 Coccaro, Ersilia Unknown Date No description available. sodium hydrogen exchanger sustained acidosis phenylephrine myocardium extracellular regulated kinase 1/2 p90 risobomal S6 kinase
6	Occurrence and Structure of an Activating Enzyme for an S6 Kinase Determined by Monoclonal Antibody Analysis Murdoch, Fern E. (Fern Elizabeth) 05 1900 (has links) In this study, the production of monoclonal antibodies directed against the activating enzyme for an S6 kinase is examined and described. Evidence is presented for the association of an Mr. 55,000 abd Mr. 95,000 protein with the s6 kinase. These proteins are phosphorylated in the presence of Activating Enzyme. A sequence of regulatory events for insulin-stimulated phosphorylation of ribosomal protein S6 in cells is postulated as follows: insulin activates the receptor tyrosine kinase, which phosphorylates the Mr 116,000 subunit of Activating Enzyme. The Activating Enzyme then activates the S6 kniase by phosphorylation, and phosphorylation of the ribosomal protein s6 is promoted. protein kinases enzyme activation monoclonal antibodies S6 kinase Protein kinases. Enzyme activation. Monoclonal antibodies.
7	A Global Kinase and Phosphatase Interaction Network in the Budding Yeast Reveals Novel Effectors of the Target of Rapamycin (TOR) Pathway Sharom, Jeffrey Roslan 31 August 2011 (has links) In the budding yeast Saccharomyces cerevisiae, the evolutionarily conserved Target of Rapamycin (TOR) signaling network regulates cell growth in accordance with nutrient and stress conditions. In this work, I present evidence that the TOR complex 1 (TORC1)-interacting proteins Nnk1, Fmp48, Mks1, and Sch9 link TOR to various facets of nitrogen metabolism and mitochondrial function. The Nnk1 kinase controlled nitrogen catabolite repression-sensitive gene expression via Ure2 and Gln3, and physically interacted with the NAD+-linked glutamate dehydrogenase Gdh2 that catalyzes deamination of glutamate to alpha-ketoglutarate and ammonia. In turn, Gdh2 modulated rapamycin sensitivity, was phosphorylated in Nnk1 immune complexes in vitro, and was relocalized to a discrete cytoplasmic focus in response to NNK1 overexpression or respiratory growth. The Fmp48 kinase regulated respiratory function and mitochondrial morphology, while Mks1 linked TORC1 to the mitochondria-to-nucleus retrograde signaling pathway. The Sch9 kinase appeared to act as both an upstream regulator and downstream sensor of mitochondrial function. Loss of Sch9 conferred a respiratory growth defect, a defect in mitochondrial DNA transmission, lower mitochondrial membrane potential, and decreased levels of reactive oxygen species. Conversely, loss of mitochondrial DNA caused loss of Sch9 enrichment at the vacuolar membrane, loss of Sch9 phospho-isoforms, and small cell size suggestive of reduced Sch9 activity. Sch9 also exhibited dynamic relocalization in response to stress, including enrichment at mitochondria under conditions that have previously been shown to induce apoptosis in yeast. Taken together, this work reveals intimate connections between TORC1, nitrogen metabolism, and mitochondrial function, and has implications for the role of TOR in regulating aging, cancer, and other human diseases. Target of Rapamycin budding yeast Saccharomyces cerevisiae yeast kinase phosphatase protein-protein interactions TOR nutrients growth rapamycin signaling network metabolism nitrogen catabolite repression retrograde response glutamate dehydrogenase glutamine glutamate alpha-ketoglutarate cell size aging lifespan mitochondria uncoupled respiration petite reactive oxygen species free radical theory of aging apoptosis cancer glutaminolysis TORC1 Nnk1 Fmp48 Mks1 Sch9 Gdh2 Ure2 ribosomal protein S6 kinase S6K cell biology molecular biology 0307 0379 0369 0410 0306
8	A Global Kinase and Phosphatase Interaction Network in the Budding Yeast Reveals Novel Effectors of the Target of Rapamycin (TOR) Pathway Sharom, Jeffrey Roslan 31 August 2011 (has links) In the budding yeast Saccharomyces cerevisiae, the evolutionarily conserved Target of Rapamycin (TOR) signaling network regulates cell growth in accordance with nutrient and stress conditions. In this work, I present evidence that the TOR complex 1 (TORC1)-interacting proteins Nnk1, Fmp48, Mks1, and Sch9 link TOR to various facets of nitrogen metabolism and mitochondrial function. The Nnk1 kinase controlled nitrogen catabolite repression-sensitive gene expression via Ure2 and Gln3, and physically interacted with the NAD+-linked glutamate dehydrogenase Gdh2 that catalyzes deamination of glutamate to alpha-ketoglutarate and ammonia. In turn, Gdh2 modulated rapamycin sensitivity, was phosphorylated in Nnk1 immune complexes in vitro, and was relocalized to a discrete cytoplasmic focus in response to NNK1 overexpression or respiratory growth. The Fmp48 kinase regulated respiratory function and mitochondrial morphology, while Mks1 linked TORC1 to the mitochondria-to-nucleus retrograde signaling pathway. The Sch9 kinase appeared to act as both an upstream regulator and downstream sensor of mitochondrial function. Loss of Sch9 conferred a respiratory growth defect, a defect in mitochondrial DNA transmission, lower mitochondrial membrane potential, and decreased levels of reactive oxygen species. Conversely, loss of mitochondrial DNA caused loss of Sch9 enrichment at the vacuolar membrane, loss of Sch9 phospho-isoforms, and small cell size suggestive of reduced Sch9 activity. Sch9 also exhibited dynamic relocalization in response to stress, including enrichment at mitochondria under conditions that have previously been shown to induce apoptosis in yeast. Taken together, this work reveals intimate connections between TORC1, nitrogen metabolism, and mitochondrial function, and has implications for the role of TOR in regulating aging, cancer, and other human diseases. Target of Rapamycin budding yeast Saccharomyces cerevisiae yeast kinase phosphatase protein-protein interactions TOR nutrients growth rapamycin signaling network metabolism nitrogen catabolite repression retrograde response glutamate dehydrogenase glutamine glutamate alpha-ketoglutarate cell size aging lifespan mitochondria uncoupled respiration petite reactive oxygen species free radical theory of aging apoptosis cancer glutaminolysis TORC1 Nnk1 Fmp48 Mks1 Sch9 Gdh2 Ure2 ribosomal protein S6 kinase S6K cell biology molecular biology 0307 0379 0369 0410 0306

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