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Amino Acids of the Glutamate Family: Functions beyond Primary Metabolism

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Book Series: Frontiers Research Topics ISSN: 16648714 ISBN: 9782889199365 Year: Pages: 206 DOI: 10.3389/978-2-88919-936-5 Language: English
Publisher: Frontiers Media SA
Subject: Science (General) --- Botany
Added to DOAB on : 2016-01-19 14:05:46
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Abstract

The life of proteins starts and ends as amino acids. In addition to the primary function as protein building blocks, amino acids serve multiple other purposes to make a plant's life worth living. This is true especially for the amino acids of the glutamate family, namely glutamate (Glu), glutamine (Gln), proline (Pro) and arginine (Arg), as well as the product of Glu decarboxylation, ?-aminobutyric acid (GABA). Synthesis, accumulation, interconversion and degradation of these five compounds contribute in many ways to the regulation of plant development and to responses to environmental challenges. Glu and Gln hold key positions as entry points and master regulators of nitrogen metabolism in plants, and have a pivotal role in the regulatory interplay between carbon and nitrogen metabolism. Pro and GABA are among the best-studied compatible osmolytes that accumulate in response to water deficit, yet the full range of protective functions is still to be revealed. Arg, with its exceptionally high nitrogen-to-carbon ratio, has long been recognized as a major storage form of organic nitrogen. Most of the enzymes involved in metabolism of the amino acids of the glutamate family in plants have been identified or can be predicted according to similarity with animal or microbial homologues. However, for some of these enzymes the detailed biochemical properties still remain to be determined in order to understand activities in vivo. Additionally, uncertainties regarding the subcellular localization of proteins and especially the lack of knowledge about intracellular transport proteins leave significant gaps in our understanding of the metabolic network connecting Glu, Gln, Pro, GABA and Arg. While anabolic reactions are distributed between the cytosol and chloroplasts, catabolism of the amino acids of the glutamate family takes place in mitochondria and has been implicated in fueling energy-demanding physiological processes such as root elongation, recovery from stress, bolting and pollen tube elongation. Exceeding the metabolic functions, the amino acids of the glutamate family were recently identified as important signaling molecules in plants. Extracellular Glu, GABA and a range of other metabolites trigger responses in plant cells that resemble the actions of Glu and GABA as neurotransmitters in animals. Plant homologues of the Glu-gated ion channels from mammals and protein kinase signaling cascades have been implicated in these responses. Pollen tube growth and guidance depend on GABA signaling and the root architecture is specifically regulated by Glu. GABA and Pro signaling or metabolism were shown to contribute to the orchestration of defense and programmed cell death in response to pathogen attacks. Pro signaling was additionally proposed to regulate developmental processes and especially sexual reproduction. Arg is tightly linked to nitric oxide (NO) production and signaling in plants, although Arg-dependent NO-synthases could still not be identified. Potentially Arg-derived polyamines constitute the missing link between Arg and NO signaling in response to stress. Taken together, the amino acids of the glutamate family emerge as important signaling molecules that orchestrate plant growth and development by integrating the metabolic status of the plant with environmental signals, especially in stressful conditions. This research topic collects contributions from different facets of glutamate family amino acid signaling or metabolism to bring together, and integrate in a comprehensive view the latest advances in our understanding of the multiple functions of Glu-derived amino acids in plants.

Transcellular Cycles Underlying Neurotransmission

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Book Series: Frontiers Research Topics ISSN: 16648714 ISBN: 9782889196548 Year: Pages: 105 DOI: 10.3389/978-2-88919-654-8 Language: English
Publisher: Frontiers Media SA
Subject: Science (General) --- Neurology
Added to DOAB on : 2016-08-16 10:34:25
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Synaptic transmission demands the operation of a highly specialized metabolic machinery involving the transfer of metabolites and neurotransmitters between neurons, astrocytes and microvessels. In the last years, important advances have occurred in our understanding of the mechanisms underlying cerebral activation, neuroglial coupling and the associated neurovascular response. Briefly, exacerbated oxygen consumption in stimulated neurons is thought to trigger glycolytic lactate and glucose transfer from astrocytes which, in turn, obtain these fuels from the microvasculature. Neurotransmitter release is made possible by a combination of transcellular cycles exchanging metabolites between these three compartments, returning eventually the synapsis to its pre-firing situation in the resting periods. In spite of the enormous progresses achieved in recent years, the drivers determining the predominant direction of the fluxes, their quantitative contribution and their energy requirements, have remained until today incompletely understood, more particularly under the circumstances prevailing in vivo. In many instances, progress derived from the implementation of novel methodological approaches including advanced neuroimaging and neurospectroscopy methods. As a consequence, literature in the field became vast, diverse and spread within journals of different specialities. The e-book "Transcellular cycles underlying neurotransmission" aims to summaryze in a single volume, recent progress achieved in hypothesis, methods and interpretations on the trafficking of metabolites between neurons and glial cells, and the associated mechanisms of neurovascular coupling.

Astrocytic-neuronal-astrocytic Pathway Selection for Formation and Degradation of Glutamate/GABA

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Book Series: Frontiers Research Topics ISSN: 16648714 ISBN: 9782889192434 Year: Pages: 168 DOI: 10.3389/978-2-88919-243-4 Language: English
Publisher: Frontiers Media SA
Subject: Science (General) --- Biology --- Medicine (General) --- Internal medicine
Added to DOAB on : 2015-11-16 15:44:59
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Endocrinological research early recognized the importance of intercellular interactions and realized the importance of glutamatergic and GABAergic signaling. In turn this signalling depends on elaborate interactions between astrocytes and neurons, without which neurons would be unable to produce, reuse and metabolize transmitter glutamate and GABA. Details of these subjects are described in this Research Topic by key investigators in this field. It focuses on the intricate and extremely swift pathway producing these amino acid transmitters from glucose in brain but also discusses difficulties in determining expression of some of the necessary genes in astrocytes and related processes in pancreatic islets. However, it does not discuss how closely associated astrocytes and neurons are anatomically, enabling these interactions. This is elegantly shown in this cover image, kindly provided by Professor Andreas Reichenbach (University of Leipzig, Germany).

Cell Stress, Metabolic Reprogramming, and Cancer

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Book Series: Frontiers Research Topics ISSN: 16648714 ISBN: 9782889455652 Year: Pages: 68 DOI: 10.3389/978-2-88945-565-2 Language: English
Publisher: Frontiers Media SA
Subject: Medicine (General) --- Oncology
Added to DOAB on : 2019-01-23 14:53:43
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The present eBook presents one review, five mini-reviews, and an opinion article on the achievements and perspectives of studies on important aspects of cancer cell metabolic reprogramming whose mechanisms and regulation are still largely elusive. It also sheds light on certain novel functional components, which rewires cell metabolism in tumor transformation.

Roles and Functions of ROS and RNS in Cellular Physiology and Pathology

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ISBN: 9783039287826 / 9783039287833 Year: Pages: 230 DOI: 10.3390/books978-3-03928-783-3 Language: eng
Publisher: MDPI - Multidisciplinary Digital Publishing Institute
Subject: Medicine (General) --- Pathology
Added to DOAB on : 2020-06-09 16:38:57
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Our common knowledge on oxidative stress has evolved substantially over the years and has been mostly focused on the fundamental chemical reactions and the most relevant chemical species involved in the human pathophysiology of oxidative stress-associated diseases. Thus, reactive oxygen species and reactive nitrogen species (ROS and RNS) were identified as the key players initiating, mediating, and regulating the cellular and biochemical complexity of oxidative stress either as physiological (acting pro-hormetic) or as pathogenic (causing destructive vicious circle) process. The papers published in this particular Special Issue of the Cells demonstrate the impressive pathophysiological relevance of ROS and RNS in a range of contexts, including the relevance of second messengers of free radicals like 4-hydroxynonenal, allowing us to assume that even more detailed mechanisms of their positive and negative effects lie in wait, and should assist in better monitoring of the major modern diseases and the development of advanced integrative biomedicine treatments.

Keywords

human neuroblastoma SH-SY5Y cells --- TRPM2 channel --- ROS --- neuronal cell death --- histamine --- calcium --- endothelial cells --- NADPH-oxidase --- VAS2870 --- von Willebrand factor --- aorta --- relaxation --- reactive oxygen species (ROS) --- oxidative stress --- lipid peroxidation --- acrolein --- 4-hydroxynonenal (4-HNE) --- oxidative burst --- granulocytes --- cancer cells --- growth control --- cancer regression --- hydroxyapatite-based biomaterials --- osteoblast growth --- redox balance --- vitamins --- lipid peroxidation --- 4-hydroxynonenal --- oxidative stress --- oxidative stress --- nuclear factor erythroid 2–related factor 2 --- heme-oxygenase-1 --- macrophages --- plaque vulnerability --- optical coherence tomography --- reactive oxygen species --- free radicals --- DNA damage --- cyclopurines --- DNA and RNA polymerases --- nucleotide excision repair --- LC-MS/MS --- xeroderma pigmentosum --- cancer --- intermittent hypoxia --- mitochondria --- Ca2+, ROS --- antioxidant --- free radicals --- antimicrobial --- toll-like receptors --- cannabidiol --- UV radiation --- keratinocytes --- antioxidants --- inflammation --- intracellular signaling --- Nrf2 --- NF?B --- glucose deprivation --- glutamine deprivation --- viability --- proliferation --- ROS --- NRF2-NQO1 axis --- IMR-90 --- NQO1 transcript variants --- rs1800566 --- TP53 mutation --- oxidative stress --- MFN2 --- mitochondria --- fusion/fission --- oxidative stress --- blood–brain barrier --- bEnd5 --- bEnd.3 --- glutathione --- viability --- free radicals --- redox balance --- cell signaling --- growth --- toxicity --- antioxidants --- oxidative homeostasis --- oxidative metabolism of the cells --- pathophysiology of oxidative stress

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