Ammonium transport: unifying concepts and unique aspects

2001 ◽  
Vol 28 (9) ◽  
pp. 959 ◽  
Author(s):  
Anne van Dommelen ◽  
René de Mot ◽  
Jos Vanderleyden
Keyword(s):  
Current Knowledge ◽  
Natural Habitat ◽  
Physiological Role ◽  
Ammonium Uptake ◽  
Ammonium Transport ◽  
Symbiotic Interaction ◽  
Ammonium Transporters ◽  
Operating Current ◽  
Living Organisms

This paper originates from an address at the 8th International Symposium on Nitrogen Fixation with Non-Legumes, Sydney, NSW, December 2000 Ammonium uptake by cells has been studied for more than a century, but only recently a family of ammonium transporters (Mep/Amt) with 10–12 transmembrane domains has been defined. These proteins are probably ubiquitous, since homologues have been found in the major kingdoms of living organisms. Plants as well as yeast and some archaebacteria have multiple Mep/Amt paralogues, which can be distinguished by their affinity for ammonium and the ammonium analogue methylammonium. Most ammonium transporters are induced in nitrogen-starving conditions, both in prokaryotes and plants. In Saccharomyces cerevisiae, Escherichia coli and Azospirillum brasilense Mep/Amt proteins where shown to be necessary for growth when the external concentration of the diffusive ammonium form (NH3) becomes limiting. Ammonium transporters also play an important role in pseudohyphal differentiation in yeast and efficient symbiotic interaction between Rhizobium etli and its host plant. In most bacteria, NH4+ transport appears to be a uniport mechanism driven by the membrane potential, but, depending on the organism, a different mode of ammonium uptake may be operating. Current knowledge offers the basis to investigate further the physiological role of ammonium transporters in the natural habitat of organisms and their importance in plant–bacteria interactions.

scholarly journals Role of Mitochondrial Cytochrome P450 2E1 in Healthy and Diseased Liver

Cells ◽  
2022 ◽  
Vol 11 (2) ◽  
pp. 288
Author(s):  
Julie Massart ◽  
Karima Begriche ◽  
Jessica H. Hartman ◽  
Bernard Fromenty
Keyword(s):  
Oxidative Stress ◽  
Cytochrome P450 ◽  
Liver Disease ◽  
Fatty Liver ◽  
Current Knowledge ◽  
Physiological Role ◽  
Experimental Investigations ◽  
Rat Liver Mitochondria ◽  
Cytochrome P450 2E1

Cytochrome P450 2E1 (CYP2E1) is pivotal in hepatotoxicity induced by alcohol abuse and different xenobiotics. In this setting, CYP2E1 generates reactive metabolites inducing oxidative stress, mitochondrial dysfunction and cell death. In addition, this enzyme appears to play a role in the progression of obesity-related fatty liver to nonalcoholic steatohepatitis. Indeed, increased CYP2E1 activity in nonalcoholic fatty liver disease (NAFLD) is deemed to induce reactive oxygen species overproduction, which in turn triggers oxidative stress, necroinflammation and fibrosis. In 1997, Avadhani’s group reported for the first time the presence of CYP2E1 in rat liver mitochondria, and subsequent investigations by other groups confirmed that mitochondrial CYP2E1 (mtCYP2E1) could be found in different experimental models. In this review, we first recall the main features of CYP2E1 including its role in the biotransformation of endogenous and exogenous molecules, the regulation of its expression and activity and its involvement in different liver diseases. Then, we present the current knowledge on the physiological role of mtCYP2E1, its contribution to xenobiotic biotransformation as well as the mechanism and regulation of CYP2E1 targeting to mitochondria. Finally, we discuss experimental investigations suggesting that mtCYP2E1 could have a role in alcohol-associated liver disease, xenobiotic-induced hepatotoxicity and NAFLD.

Signalling functions of coenzyme A and its derivatives in mammalian cells

2014 ◽  
Vol 42 (4) ◽  
pp. 1056-1062 ◽  
Author(s):  
Hongorzul Davaapil ◽  
Yugo Tsuchiya ◽  
Ivan Gout
Keyword(s):  
Mammalian Cells ◽  
Coenzyme A ◽  
Current Knowledge ◽  
Pantothenic Acid ◽  
Future Developments ◽  
Malonyl Coa ◽  
Vitamin B5 ◽  
Coa Thioesters ◽  
Living Organisms

In all living organisms, CoA (coenzyme A) is synthesized in a highly conserved process that requires pantothenic acid (vitamin B5), cysteine and ATP. CoA is uniquely designed to function as an acyl group carrier and a carbonyl-activating group in diverse biochemical reactions. The role of CoA and its thioester derivatives, including acetyl-CoA, malonyl-CoA and HMG-CoA (3-hydroxy-3-methylglutaryl-CoA), in the regulation of cellular metabolism has been extensively studied and documented. The main purpose of the present review is to summarize current knowledge on extracellular and intracellular signalling functions of CoA/CoA thioesters and to speculate on future developments in this area of research.

Fungal Production and Manipulation of Plant Hormones

2018 ◽  
Vol 25 (2) ◽  
pp. 253-267 ◽  
Author(s):  
Sandra Fonseca ◽  
Dhanya Radhakrishnan ◽  
Kalika Prasad ◽  
Andrea Chini
Keyword(s):  
Stress Responses ◽  
Current Knowledge ◽  
Critical Role ◽  
Plant Defence ◽  
Pathogenic Fungi ◽  
Plant Responses ◽  
Defensive Strategies ◽  
Hormone Balance ◽  
Living Organisms

Living organisms are part of a highly interconnected web of interactions, characterised by species nurturing, competing, parasitizing and preying on one another. Plants have evolved cooperative as well as defensive strategies to interact with neighbour organisms. Among these, the plant-fungus associations are very diverse, ranging from pathogenic to mutualistic. Our current knowledge of plant-fungus interactions suggests a sophisticated coevolution to ensure dynamic plant responses to evolving fungal mutualistic/pathogenic strategies. The plant-fungus communication relies on a rich chemical language. To manipulate the plant defence mechanisms, fungi produce and secrete several classes of biomolecules, whose modeof- action is largely unknown. Upon perception of the fungi, plants produce phytohormones and a battery of secondary metabolites that serve as defence mechanism against invaders or to promote mutualistic associations. These mutualistic chemical signals can be co-opted by pathogenic fungi for their own benefit. Among the plant molecules regulating plant-fungus interaction, phytohormones play a critical role since they modulate various aspects of plant development, defences and stress responses. Intriguingly, fungi can also produce phytohormones, although the actual role of fungalproduced phytohormones in plant-fungus interactions is poorly understood. Here, we discuss the recent advances in fungal production of phytohormone, their putative role as endogenous fungal signals and how fungi manipulate plant hormone balance to their benefits.

scholarly journals A twin histidine motif is the core structure for high-affinity substrate selection in plant ammonium transporters

2020 ◽  
Vol 295 (10) ◽  
pp. 3362-3370 ◽  
Author(s):  
Pascal Ganz ◽  
Toyosi Ijato ◽  
Romano Porras-Murrilo ◽  
Nils Stührwohldt ◽  
Uwe Ludewig ◽  
...  
Keyword(s):  
Membrane Proteins ◽  
Core Structure ◽  
Ammonium Uptake ◽  
Ammonium Transport ◽  
Substrate Affinity ◽  
Substrate Selection ◽  
Alkali Cations ◽  
High Substrate ◽  
The Core ◽  
Ammonium Transporters

Ammonium transporters (AMT), methylamine permeases (Mep), and the more distantly related rhesus factors (Rh) are trimeric membrane proteins present in all domains of life. AMT/Mep/Rhs are highly selective membrane proteins required for ammonium uptake or release, and they efficiently exclude the similarly sized K+ ion. Previously reported crystal structures have revealed that each transporter subunit contains a unique hydrophobic but occluded central pore, but it is unclear whether the base (NH3) or NH3 coupled with an H+ are transported. Here, using expression of two plant AMTs (AtAMT1;2 and AMT2) in budding yeast, we found that systematic replacements in the conserved twin-histidine motif, a hallmark of most AMT/Mep/Rh, alter substrate recognition, transport capacities, N isotope selection, and selectivity against K+. AMT-specific differences were found for histidine variants. Variants that completely lost ammonium N isotope selection, a feature likely associated with NH4+ deprotonation during passage, substantially transported K+ in addition to NH4+. Of note, the twin-histidine motif was not essential for ammonium transport. However, it conferred key AMT features, such as high substrate affinity and selectivity against alkali cations via an NH4+ deprotonation mechanism. Our findings indicate that the twin-His motif is the core structure responsible for substrate deprotonation and isotopic preferences in AMT pores and that decreased deprotonation capacity is associated with reduced selectivity against K+. We conclude that optimization for ammonium transport in plant AMT represents a compromise between substrate deprotonation for optimal selectivity and high substrate affinity and transport rates.

scholarly journals The Physiological Role of Irisin in the Regulation of Muscle Glucose Homeostasis

Endocrines ◽  
2021 ◽  
Vol 2 (3) ◽  
pp. 266-283
Author(s):  
Naohiro Yano ◽  
Yu Tina Zhao ◽  
Ting C. Zhao
Keyword(s):  
Adipose Tissue ◽  
Glucose Metabolism ◽  
Current Knowledge ◽  
Physiological Role ◽  
Target Organ ◽  
Direct Effects ◽  
Beneficial Effects ◽  
The Relationship ◽  
Major Target

Irisin is a myokine that primarily targets adipose tissue, where it increases energy expenditure and contributes to the beneficial effects of exercise through the browning of white adipose tissue. As our knowledge has deepened in recent years, muscle has been found to be a major target organ for irisin as well. Several studies have attempted to characterize the role of irisin in muscle to improve glucose metabolism through mechanisms such as reducing insulin resistance. Although they are very intriguing reports, some contradictory results make it difficult to grasp the whole picture of the action of irisin on muscle. In this review, we attempted to organize the current knowledge of the role of irisin in muscle glucose metabolism. We discussed the direct effects of irisin on glucose metabolism in three types of muscle, that is, skeletal muscle, smooth muscle, and the myocardium. We also describe irisin’s effects on mitochondria and its interactions with other hormones. Furthermore, to consider the relationship between the irisin-induced improvement of glucose metabolism in muscle and systemic disorders of glucose metabolism, we reviewed the results from animal interventional studies and human clinical studies.

scholarly journals Toward Understanding the Role of Aryl Hydrocarbon Receptor in the Immune System: Current Progress and Future Trends

2014 ◽  
Vol 2014 ◽  
pp. 1-14 ◽  
Author(s):  
Hamza Hanieh
Keyword(s):  
Immune System ◽  
Aryl Hydrocarbon Receptor ◽  
Immune Cells ◽  
Immune Cell ◽  
Current Knowledge ◽  
Physiological Role ◽  
Clinical Practices ◽  
Aryl Hydrocarbon ◽  
Active Research

The immune system is regulated by distinct signaling pathways that control the development and function of the immune cells. Accumulating evidence suggest that ligation of aryl hydrocarbon receptor (Ahr), an environmentally responsive transcription factor, results in multiple cross talks that are capable of modulating these pathways and their downstream responsive genes. Most of the immune cells respond to such modulation, and many inflammatory response-related genes contain multiple xenobiotic-responsive elements (XREs) boxes upstream. Active research efforts have investigated the physiological role of Ahr in inflammation and autoimmunity using different animal models. Recently formed paradigm has shown that activation of Ahr by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) or 3,3′-diindolylmethane (DIM) prompts the differentiation of CD4+Foxp3+regulatory T cells (Tregs) and inhibits T helper (Th)-17 suggesting that Ahr is an innovative therapeutic strategy for autoimmune inflammation. These promising findings generate a basis for future clinical practices in humans. This review addresses the current knowledge on the role of Ahr in different immune cell compartments, with a particular focus on inflammation and autoimmunity.

scholarly journals The Role of Autophagy in Immunity and Autoimmune Diseases / Uloga Autofagije U Imunskom Odgovoru I Autoimunskim Bolestima

2014 ◽  
Vol 15 (4) ◽  
pp. 223-229
Author(s):  
Bojana Simovic Markovic ◽  
Ljubica Vucicevic ◽  
Sanja Bojic ◽  
Vladislav Volarevic
Keyword(s):  
Autoimmune Diseases ◽  
Potential Role ◽  
Current Knowledge ◽  
Inflammatory Diseases ◽  
Physiological Role ◽  
Immune Functions ◽  
Complex Relationships ◽  
Cellular Components ◽  
Chaperone Mediated Autophagy

ABSTRACT Autophagy is a catabolic mechanism in the cell that involves the degradation of unnecessary or dysfunctional cellular components by the lysosomal machinery. Recent studies have indicated that autophagy is a source of autoantigens, thus highlighting its potential role in the pathogenesis of autoimmunity. There are at least three different forms of autophagy: macroautophagy, microautophagy and chaperone-mediated autophagy (CMA). The physiological role of autophagy is to maintain cellular homeostasis by removing long-lived, damaged proteins and dysfunctional organelles and by providing energy. Aberrant autophagy may contribute to chronic inflammatory diseases and autoimmune diseases. An understanding of the complex relationships between autophagy and autophagy-related genes in each autoimmune disease creates the possibility of developing more specific and effective therapeutic strategies. Given the importance of autophagy in immune functions, this review article summarises current knowledge about the role of autophagy in the pathogenesis of autoimmune diseases.

The BPI-like/PLUNC family proteins in cattle

2011 ◽  
Vol 39 (4) ◽  
pp. 1006-1011 ◽  
Author(s):  
Thomas T. Wheeler ◽  
Brendan J. Haigh ◽  
Marita K. Broadhurst ◽  
Kylie A. Hood ◽  
Nauman J. Maqbool
Keyword(s):  
Protein Gene ◽  
Current Knowledge ◽  
Physiological Role ◽  
Secretory Protein ◽  
Salivary Protein ◽  
Ancestral Gene ◽  
Bacterial Aggregation ◽  
Parotid Secretory Protein ◽  
Pathogen Exposure

Members of the protein family having similarity to BPI (bactericidal/permeability increasing protein) (the BPI-like proteins), also known as the PLUNC (palate, lung and nasal epithelium clone) family, have been found in a range of mammals; however, those in species other than human or mouse have been relatively little characterized. Analysis of the BPI-like proteins in cattle presents unique opportunities to investigate the function of these proteins, as well as address their evolution and contribution to the distinct physiology of ruminants. The present review summarizes the current understanding of the nature of the BPI-like locus in cattle, including the duplications giving rise to the multiple BSP30 (bovine salivary protein 30 kDa) genes from an ancestral gene in common with the single PSP (parotid secretory protein) gene found in monogastric species. Current knowledge of the expression of the BPI-like proteins in cattle is also presented, including their pattern of expression among tissues, which illustrate their independent regulation at sites of high pathogen exposure, and the abundance of the BSP30 proteins in saliva and salivary tissues. Finally, investigations of the function of the BSP30 proteins are presented, including their antimicrobial, lipopolysaccharide-binding and bacterial aggregation activities. These results are discussed in relation to hypotheses regarding the physiological role of the BPI-like proteins in cattle, including the role they may play in host defence and the unique aspects of digestion in ruminants.

scholarly journals GDNF and protection of adult central catecholaminergic neurons

2011 ◽  
Vol 46 (3) ◽  
pp. R83-R92 ◽  
Author(s):  
Alberto Pascual ◽  
María Hidalgo-Figueroa ◽  
Raquel Gómez-Díaz ◽  
José López-Barneo
Keyword(s):  
Current Knowledge ◽  
Physiological Role ◽  
Adult Brain ◽  
Peripheral Neurons ◽  
Central Neurons ◽  
Small Proteins ◽  
Therapeutic Tools ◽  
And Function ◽  
Catecholaminergic Cells

Neurotrophic factors are small proteins necessary for neuron survival and maintenance of phenotype. They are considered as promising therapeutic tools for neurodegenerative diseases. The glial cell line-derived neurotrophic factor (GDNF) protects catecholaminergic cells from toxic insults; thus, its potential therapeutic applicability in Parkinson's disease has been intensely investigated. In recent years, there have been major advances in the analysis of GDNF signaling pathways in peripheral neurons and embryonic dopamine mesencephalic cells. However, the actual physiological role of GDNF in maintaining catecholaminergic central neurons during adulthood is only starting to be unraveled, and the mechanisms whereby GDNF protects central brain neurons are poorly known. In this study, we review the current knowledge of GDNF expression, signaling, and function in adult brain, with special emphasis on the genetic animal models with deficiency in the GDNF-dependent pathways.

scholarly journals BZR1 Regulates Brassinosteroid-Mediated Activation of AMT1;2 in Rice

2021 ◽  
Vol 12 ◽  
Author(s):  
Shuo Yang ◽  
Depeng Yuan ◽  
Yang Zhang ◽  
Qian Sun ◽  
Yuan Hu Xuan
Keyword(s):  
Signaling Pathway ◽  
Receptor Gene ◽  
Ammonium Uptake ◽  
Plant Nutrient ◽  
Regulatory Effect ◽  
Plant Growth And Development ◽  
Rice Roots ◽  
Ammonium Transporters ◽  
Genetic Combination

Although it is known that brassinosteroids (BRs) play pleiotropic roles in plant growth and development, their roles in plant nutrient uptake remain unknown. Here, we hypothesized that BRs directly regulate ammonium uptake by activating the expression of rice AMT1-type genes. Exogenous BR treatment upregulated both AMT1;1 and AMT1;2 expression, while this induction was impaired in the BR-receptor gene BRI1 mutant d61-1. We then focused on brassinazole-resistant 1 (BZR1), a central hub of the BR signaling pathway, demonstrating the important role of this signaling pathway in regulating AMT1 expression and rice roots NH4+ uptake. The results showed that BR-induced expression of AMT1;2 was suppressed in BZR1 RNAi plants but was increased in bzr1-D, a gain-of-function BZR1 mutant. Further EMSA and ChIP analyses showed that BZR1 bound directly to the BRRE motif located in the promoter region of AMT1;2. Moreover, cellular ammonium contents, 15NH4+ uptake, and the regulatory effect of methyl-ammonium on root growth are strongly dependent on the levels of BZR1. Overexpression lines of BRI1 and BZR1 and Genetic combination of them mutants showed that BZR1 activates AMT1;2 expression downstream of BRI1. In conclusion, the findings suggest that BRs regulation of NH4+ uptake in rice involves transcription regulation of ammonium transporters.

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