Cold-shock-stimulated γ-aminobutyric acid synthesis is mediated by an increase in cytosolic Ca2+, not by an increase in cytosolic H+

Synthesis of the nonprotein amino acid γ-aminobutyric acid is stimulated within minutes by diverse environmental factors. Synthesis (L-Glu + H+ – γ-aminobutyric acid + CO2) is catalysed by L-Glu decarboxylase, a cytosolic enzyme having an acidic pH optimum. This study uses isolated Asparagus sprengeri (Regel) mesophyll cells to investigate the possible role of Ca2+ in stimulated γ-aminobutyric acid synthesis. Abrupt cold shock (20 °C to 1 °C) stimulated γ-aminobutyric acid levels from 2.7 to 5.6 nmol/106 cells within 15 min. This 100% increase was reduced to 28% in the presence of the Ca2+ channel blocker lanthanum, and was significantly reduced by incubation with 1 mM of the calmodulin antagonist N-(6-aminohexyl)-5-chloro-1-naphthalene-sulfonamide. Incubation at 20 °C with 25 μM calcimycin, a Ca2+ ionophore, increased levels by 61% within 15 min. A fluorescent Ca2+ indicator demonstrated that cytosolic Ca2+ increased within 2 s of cold shock, followed by a return to initial levels within 25 s. In contrast, comparable experiments indicate a rapid and prolonged decrease in cytosolic H+. L-Glu decarboxylase isolated from asparagus cladophylls was stimulated 100% by addition of 500 μM Ca2+ and 200 nM calmodulin. This activity was reduced to control values by the calmodulin antagonist. Collectively, the data indicate that cold shock initiates a signal transduction pathway in which increased cytosolic Ca2+ stimulates calmodulin-dependent L-Glu decarboxylase activity and γ-aminobutyric acid synthesis. This mechanism appears independent of increased H+. Key words: cold shock, GABA, Ca2+, H+.

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Abscisic Acid Promotes γ-Aminobutyric Acid Accumulation in Soybean Germinating Under Hypoxia-NaCl Stress

Current Topics in Nutraceutical Research ◽

10.37290/ctnr2641-452x.19:283-287 ◽

2020 ◽

Vol 19 (3) ◽

pp. 283-287

Author(s):

Yuan-Xin Guo ◽

Dong-Xu Wang ◽

Hua Ye ◽

Zhen-Xin Gu ◽

Run-Qiang Yang

Keyword(s):

Abscisic Acid ◽

Glutamate Decarboxylase ◽

Diamine Oxidase ◽

Acid Synthesis ◽

Nacl Stress ◽

Aminobutyric Acid ◽

Oxidase Gene ◽

Nonprotein Amino Acid ◽

Acid Accumulation ◽

Diamine Oxidase Activity

γ-aminobutyric acid is a nonprotein amino acid that accumulates in plants under stress. Abscisic acid is important for stress regulation via modulation of γ-aminobutyric acid function. Our results show that the expression of glutamate decarboxylase but not diamine oxidase gene is upregulated in germinating soybean treating treated with exogenous abscisic acid. There was a concomitant increase in glutamate decarboxylase and diamine oxidase activities and putrescine and spermine contents with a decrease in glutamate. These changes were abrogated by fluridone, an inhibitor of abscisic acid synthesis. In conclusion, abscisic acid treatment increases γ-aminobutyric acid accumulation by upregulating diamine oxidase gene expression and activation of glutamate decarboxylase and diamine oxidase activity in germinating soybean under hypoxia-salt stress.

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Calcineurin mediates homeostatic synaptic plasticity by regulating retinoic acid synthesis

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1510239112 ◽

2015 ◽

Vol 112 (42) ◽

pp. E5744-E5752 ◽

Cited By ~ 31

Author(s):

Kristin L. Arendt ◽

Zhenjie Zhang ◽

Subhashree Ganesan ◽

Maik Hintze ◽

Maggie M. Shin ◽

...

Keyword(s):

Retinoic Acid ◽

Synaptic Plasticity ◽

Synaptic Transmission ◽

Critical Role ◽

Signal Transduction Pathway ◽

Acid Synthesis ◽

Synaptic Activity ◽

Homeostatic Synaptic Plasticity ◽

Dependent Protein

Homeostatic synaptic plasticity is a form of non-Hebbian plasticity that maintains stability of the network and fidelity for information processing in response to prolonged perturbation of network and synaptic activity. Prolonged blockade of synaptic activity decreases resting Ca2+ levels in neurons, thereby inducing retinoic acid (RA) synthesis and RA-dependent homeostatic synaptic plasticity; however, the signal transduction pathway that links reduced Ca2+-levels to RA synthesis remains unknown. Here we identify the Ca2+-dependent protein phosphatase calcineurin (CaN) as a key regulator for RA synthesis and homeostatic synaptic plasticity. Prolonged inhibition of CaN activity promotes RA synthesis in neurons, and leads to increased excitatory and decreased inhibitory synaptic transmission. These effects of CaN inhibitors on synaptic transmission are blocked by pharmacological inhibitors of RA synthesis or acute genetic deletion of the RA receptor RARα. Thus, CaN, acting upstream of RA, plays a critical role in gating RA signaling pathway in response to synaptic activity. Moreover, activity blockade-induced homeostatic synaptic plasticity is absent in CaN knockout neurons, demonstrating the essential role of CaN in RA-dependent homeostatic synaptic plasticity. Interestingly, in GluA1 S831A and S845A knockin mice, CaN inhibitor- and RA-induced regulation of synaptic transmission is intact, suggesting that phosphorylation of GluA1 C-terminal serine residues S831 and S845 is not required for CaN inhibitor- or RA-induced homeostatic synaptic plasticity. Thus, our study uncovers an unforeseen role of CaN in postsynaptic signaling, and defines CaN as the Ca2+-sensing signaling molecule that mediates RA-dependent homeostatic synaptic plasticity.

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Cytosolic acidification and γ-aminobutyric acid synthesis during the o×idative burst in isolated Asparagus sprengeri mesophyll cells

Canadian Journal of Botany ◽

10.1139/cjb-79-4-438 ◽

2001 ◽

Vol 79 (4) ◽

pp. 438-443 ◽

Cited By ~ 1

Author(s):

David J. Janzen ◽

Lisa J. Allen ◽

Kennaway B. MacGregor ◽

Alan W. Bown

Keyword(s):

Acid Synthesis ◽

Aminobutyric Acid ◽

Mesophyll Cells ◽

Cytosolic Acidification

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POSSIBLE ROLE OF GAMMA-AMINOBUTYRIC ACID SYNTHESIS IN THE MECHANISM OF DEXAMETHASONE FEEDBACK ACTION

Journal of Endocrinology ◽

10.1677/joe.0.0770137 ◽

1978 ◽

Vol 77 (1) ◽

pp. 137-141 ◽

Cited By ~ 27

Author(s):

Z. ÁCS ◽

E. STARK

Keyword(s):

Central Nervous System ◽

Nervous System ◽

Glutamic Acid Decarboxylase ◽

Acid Synthesis ◽

Aminobutyric Acid ◽

Acid Decarboxylase ◽

Specific Inhibition ◽

Gamma Aminobutyric Acid ◽

The Central Nervous System

Specific inhibition of glutamic acid decarboxylase (GAD, EC 4.1.1.15; the main enzyme involved in the synthesis of γ-aminobutyric acid) by mercaptopropionic acid interferes with the effect of dexamethasone on both the resting and stress-induced secretion of ACTH. It is postulated that dexamethasone may, at least in part, inhibit the secretion of ACTH via the induction of GAD, thereby raising the level of γ-aminobutyric acid in the central nervous system.

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Cytosolic acidification and γ-aminobutyric acid synthesis during the oxidative burst in isolated Asparagus sprengeri mesophyll cells

Canadian Journal of Botany ◽

10.1139/b01-024 ◽

2001 ◽

Vol 79 (4) ◽

pp. 438-443

Author(s):

David J Janzen ◽

Lisa J Allen ◽

Kennaway B MacGregor ◽

Alan W Bown

Keyword(s):

Oxidative Burst ◽

Acid Synthesis ◽

Aminobutyric Acid ◽

Intracellular Acidification ◽

Protein Amino Acid ◽

Mesophyll Cells ◽

Intracellular Ca ◽

Gaba Accumulation ◽

Gaba Synthesis ◽

The Relationship

The four carbon, non-protein amino acid γ-aminobutyrate (GABA) accumulates rapidly in response to diverse stresses. Its synthesis is stimulated by increases in intracellular Ca2+ or H+ levels. The pathogen-induced oxidative burst is also associated with increases in Ca2+ and H+ levels. This study investigated the relationship between GABA synthesis and the oxidative burst. A Mas-7-induced consumption of oxygen in isolated Asparagus sprengeri Regel mesophyll cells was accompanied by rapid GABA synthesis. At pH 5.0, a 300% increase occurred within 16 min from 6.6 to 26.3 nmol GABA·106 cells1. At pH 6.0, the increase was from 8.5 to 18.1 nmol GABA·106 cells1. Mas-7 also stimulated rapid external alkalinization and intracellular acidification. Intracellular pH decreased 0.44 pH units at pH 5.0, and 0.21 pH units at pH 6.0. The Mas-7-induced oxidative burst, GABA synthesis, extracellular alkalinization, and intracellular acidification were all eliminated when lanthanum, a Ca2+ channel blocker, replaced Ca2+ in the incubation medium. The data demonstrate that GABA accumulation is associated with the oxidative burst, and results from the fluxes of H+ and Ca2+, which are known to accompany the oxidative burst. They are discussed in light of emerging data that indicate a role for GABA in plant cell to cell signaling.Key words: γ-aminobutyric acid, GABA, oxidative burst.

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Role of γ‐Aminobutyric Acid in the Mitigation of Abiotic Stress in Plants

Protective Chemical Agents in the Amelioration of Plant Abiotic Stress ◽

10.1002/9781119552154.ch20 ◽

2020 ◽

pp. 413-423

Author(s):

Ankur Singh ◽

Aryadeep Roychoudhury

Keyword(s):

Abiotic Stress ◽

Aminobutyric Acid

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Four Mutant Alleles Elucidate the Role of the G2 Protein in the Development of C4 and C3 Photosynthesizing Maize Tissues

Genetics ◽

10.1093/genetics/159.2.787 ◽

2001 ◽

Vol 159 (2) ◽

pp. 787-797

Author(s):

Lizzie Cribb ◽

Lisa N Hall ◽

Jane A Langdale

Keyword(s):

Cell Types ◽

Bundle Sheath ◽

Primary Role ◽

Ribulose Bisphosphate Carboxylase ◽

Sheath Cell ◽

Mesophyll Cells ◽

Phenotypic Data ◽

Bisphosphate Carboxylase ◽

Bundle Sheath Cell

Abstract Maize leaf blades differentiate dimorphic photosynthetic cell types, the bundle sheath and mesophyll, between which the reactions of C4 photosynthesis are partitioned. Leaf-like organs of maize such as husk leaves, however, develop a C3 pattern of differentiation whereby ribulose bisphosphate carboxylase (RuBPCase) accumulates in all photosynthetic cell types. The Golden2 (G2) gene has previously been shown to play a role in bundle sheath cell differentiation in C4 leaf blades and to play a less well-defined role in C3 maize tissues. To further analyze G2 gene function in maize, four g2 mutations have been characterized. Three of these mutations were induced by the transposable element Spm. In g2-bsd1-m1 and g2-bsd1-s1, the element is inserted in the second intron and in g2-pg14 the element is inserted in the promoter. In the fourth case, g2-R, four amino acid changes and premature polyadenylation of the G2 transcript are observed. The phenotypes conditioned by these four mutations demonstrate that the primary role of G2 in C4 leaf blades is to promote bundle sheath cell chloroplast development. C4 photosynthetic enzymes can accumulate in both bundle sheath and mesophyll cells in the absence of G2. In C3 tissue, however, G2 influences both chloroplast differentiation and photosynthetic enzyme accumulation patterns. On the basis of the phenotypic data obtained, a model that postulates how G2 acts to facilitate C4 and C3 patterns of tissue development is proposed.

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The Role of Deoxyribonucleic Acid in Ribonucleic Acid Synthesis

Journal of Biological Chemistry ◽

10.1016/s0021-9258(19)84522-2 ◽

1962 ◽

Vol 237 (12) ◽

pp. 3778-3785 ◽

Cited By ~ 1

Author(s):

Fred M. Kahan ◽

Jerard Hurwitz

Keyword(s):

Ribonucleic Acid ◽

Deoxyribonucleic Acid ◽

Acid Synthesis

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FSMP-15. EVALUATING THE ROLE OF LONG-CHAIN FATTY ACID METABOLISM IN PROMOTING GLIOBLASTOMA GROWTH

Neuro-Oncology Advances ◽

10.1093/noajnl/vdab024.079 ◽

2021 ◽

Vol 3 (Supplement_1) ◽

pp. i19-i19

Author(s):

Divya Ravi ◽

Carmen del Genio ◽

Haider Ghiasuddin ◽

Arti Gaur

Keyword(s):

Fatty Acids ◽

Fatty Acid ◽

Survival Rate ◽

Tumor Progression ◽

Acid Synthesis ◽

Normal Brain ◽

Acid Uptake ◽

Exogenous Fatty Acid ◽

Long Chain

Abstract Glioblastomas (GBM) or Stage IV gliomas, are the most aggressive of primary brain tumors and are associated with high mortality and morbidity. Patients diagnosed with this lethal cancer have a dismal survival rate of 14 months and a 5-year survival rate of 5.6% despite a multimodal therapeutic approach, including surgery, radiation therapy, and chemotherapy. Aberrant lipid metabolism, particularly abnormally active de novo fatty acid synthesis, is recognized to have a key role in tumor progression and chemoresistance in cancers. Previous studies have reported a high expression of fatty acid synthase (FASN) in patient tumors, leading to multiple investigations of FASN inhibition as a treatment strategy. However, none of these have developed as efficacious therapies. Furthermore, when we profiled FASN expression using The Cancer Genome Atlas (TCGA) we determined that high FASN expression in GBM patients did not confer a worse prognosis (HR: 1.06; p-value: 0.51) and was not overexpressed in GBM tumors compared to normal brain. Therefore, we need to reexamine the role of exogenous fatty acid uptake over de novofatty acid synthesis as a potential mechanism for tumor progression. Our study aims to measure and compare fatty acid oxidation (FAO) of endogenous and exogenous fatty acids between GBM patients and healthy controls. Using TCGA, we have identified the overexpression of multiple enzymes involved in mediating the transfer and activation of long-chain fatty acids (LCFA) in GBM tumors compared to normal brain tissue. We are currently conducting metabolic flux studies to (1) assess the biokinetics of LCFA degradation and (2) establish exogenous versus endogenous LCFA preferences between patient-derived primary GBM cells and healthy glial and immune cells during steady state and glucose-deprivation.

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