The role of the de novo pyrimidine biosynthetic pathway in Cryptococcus neoformans high temperature growth and virulence

Fungal infections are often difficult to treat due to the inherent similarities between fungal and animal cells and the resulting host toxicity from many antifungal compounds. Cryptococcus neoformans is an opportunistic fungal pathogen of humans that causes life-threatening disease, primarily in immunocompromised patients. Since antifungal therapy for this microorganism is limited, many investigators have explored novel drug targets aim at virulence factors, such as the ability to grow at mammalian physiological temperature (37 degrees C). To address this issue, we used the Agrobacterium tumefaciens gene delivery system to create a random insertion mutagenesis library that was screened for altered growth at elevated temperatures. Among several mutants unable to grow at 37 degrees C, we explored one bearing an interruption in the URA4 gene. This gene encodes dihydroorotase (DHOase) that is involved in the de nova synthesis of pyrimidine ribonucleotides. Loss of the C. neoformans Ura4 protein, by targeted gene interruption, resulted in an expected uracil/uridine auxotrophy and an unexpected high temperature growth defect. in addition, the ura4 mutant displayed phenotypic defects in other prominent virulence factors (melanin, capsule and phospholipase) and reduced stress response compared to wild type and reconstituted strains. Accordingly, this mutant had a decreased survival rate in macrophages and attenuated virulence in a murine model of cryptococcal infection. Quantitative PCR analysis suggests that this biosynthetic pathway is induced during the transition from 30 degrees C to 37 degrees C, and that transcriptional regulation of de nova and salvage pyrimidine pathway are under the control of the Ura4 protein. (C) 2014 the Authors. Published by Elsevier Inc. This is an open access article under the CC BY-NC-SA license (http://creativecommons.org/licenses/by-nc-sa/3.0/).Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)NIHUniversidade Federal de São Paulo, Dept Ciencias Biol, BR-09972270 Diadema, SP, BrazilUniv Brasilia, Fac Ceilandia, Brasilia, DF, BrazilDuke Univ, Sch Med, Dept Med, Durham, NC 27706 USAUniversidade Federal de São Paulo, Dept Ciencias Biol, BR-09972270 Diadema, SP, BrazilFAPESP: 2007/50536-3FAPESP: 2011/50953-9NIH: AI050128NIH: AI074677Web of Scienc

Metabolic regulation by p53

We are increasingly aware that cellular metabolism plays a vital role in diseases such as cancer, and that p53 is an important regulator of metabolic pathways. By transcriptional activation and other means, p53 is able to contribute to the regulation of glycolysis, oxidative phosphorylation, glutaminolysis, insulin sensitivity, nucleotide biosynthesis, mitochondrial integrity, fatty acid oxidation, antioxidant response, autophagy and mTOR signalling. The ability to positively and negatively regulate many of these pathways, combined with feedback signalling from these pathways to p53, demonstrates the reciprocal and flexible nature of the regulation, facilitating a diverse range of responses to metabolic stress. Intriguingly, metabolic stress triggers primarily an adaptive (rather than pro-apoptotic) p53 response, and p53 is emerging as an important regulator of metabolic homeostasis. A better understanding of how p53 coordinates metabolic adaptation will facilitate the identification of novel therapeutic targets and will also illuminate the wider role of p53 in human biology

PARAMETERS OF BATTERWORTH-VAN DYKE ELECTRIC CIRCUIT OF THE PIEZOELEMENT WITH INTER-ELECTRODE AIR GAP AND ONE-SIDED MASS-LOADING

На основі аналізу існуючих моделей еквівалентних електричних схем (ЕЕС) кварцових п'єзорезонаторів показана можливість застосування ЕЕС Batterworth-Van Dyke (BVD) для випадку п'єзоелемента (ПЕ) з міжелектродним зазором і однобічним масонавантаженням. Приведено методику визначення параметрів ЕЕС для кварцових ПЕ з міжелектродним зазором і однобічним масонавантаженням на основі одномірної моделі коливань ПЕ. Отримано параметри рівнобіжної і послідовної галузей ЕЕС і співвідношення для добротності і ємнісного відношення ПЕ. Проведено порівняння відомих і отриманих співвідношень.На основе анализа существующих моделей эквивалентных электрических схем (ЭЭС) кварцевых пьезорезонаторов показана возможность применения ЭЭС Batterworth-Van Dyke (BVD)для случая пьезоэлемента (ПЭ) с межэлектродным зазором и односторонней массонагрузкой. Приведена методика определения параметров ЭЭС для кварцевых ПЭ с межэлектродным зазором и односторонней массонагрузкой на основе одномерной модели колебаний ПЭ. Получены параметры параллельной и последовательной ветвей ЭЭС и соотношения для добротности и емкостного отношения ПЭ. Проведено сравнение известных и полученных соотношений.On the basis of the analysis of existing models of equivalent electric circuits (EEC) of the quartz piezoresonators the possibility of application Batterworth-Van Dyke (BVD) EEC for a case of a piezoelement (PE) with an interelectrode air-gap and one-sided mass-loading is shown. The method of determination of parameters of EEC for quartz PE with an interelectrode airgap and one-sided mass-loading is given. The parameters of parallel and serial branches of EES and correlations for quality and capacity relation of PE is given. Comparison of the known and got correlations is conducted