scholarly journals Split personality of Aluminum Activated Malate Transporter family proteins: facilitation of both GABA and malate transport

2017 ◽  
Author(s):  
Sunita A. Ramesh ◽  
Muhammad Kamran ◽  
Wendy Sullivan ◽  
Larissa Chirkova ◽  
Mamoru Okamoto ◽  
...  
Keyword(s):  
Wheat Root ◽  
Gaba Uptake ◽  
Gamma Aminobutyric Acid ◽  
In Planta ◽  
Root Tips ◽  
Anion Transporters ◽  
Transporter Family ◽  
Malate Transport ◽  
Split Personality ◽  
Heterologous Expression Systems

ABSTRACTPlant aluminum activated malate transporters (ALMTs) are currently classified as anion channels; they are also known to be regulated by diverse signals leading to a range of physiological responses. Gamma-aminobutyric acid (GABA) regulation of anion flux through ALMT proteins requires the presence of a specific amino acid motif in ALMTs that shares similarity with a GABA-binding site in mammalian GABAAreceptors. Here, we explore why TaALMT1-activation leads to a negative correlation between malate efflux and endogenous GABA concentrations ([GABA]i) in both wheat root tips and in heterologous expression systems. We show that TaALMT1 activation reduces [GABA]ibecause TaALMT1 facilitates GABA efflux. TaALMT1-expression also leads to GABA transport into cells, demonstrated by a yeast complementation assay and via14CGABA uptake into TaALMT1-expressingXenopus laevisoocytes; this was found to be a general feature of all ALMTs we examined. Mutation of the GABA motif (TaALMT1F213C) prevented both GABA influx and efflux, and uncoupled the relationship between malate efflux and [GABA]i. We conclude that ALMTs are likely to act as both GABA and anion transportersin planta. GABA and malate appear to interact with ALMTs in a complex manner regulating each other’s transport, suggestive of a role for ALMTs in communicating metabolic status.

scholarly journals The varied functions of aluminium-activated malate transporters–much more than aluminium resistance

2016 ◽  
Vol 44 (3) ◽  
pp. 856-862 ◽  
Author(s):  
Antony J. Palmer ◽  
Alison Baker ◽  
Stephen P. Muench
Keyword(s):  
Wheat Root ◽  
Aminobutyric Acid ◽  
Signal Transducer ◽  
Root Tips ◽  
Transporter Family ◽  
Economically Valuable Traits ◽  
Aluminium Resistance ◽  
Functionally Diverse ◽  
Different Tissues ◽  
Malate Transporter

The ALMT (aluminium-activated malate transporter) family comprises a functionally diverse but structurally similar group of ion channels. They are found ubiquitously in plant species, expressed throughout different tissues, and located in either the plasma membrane or tonoplast. The first family member identified was TaALMT1, discovered in wheat root tips, which was found to be involved in aluminium resistance by means of malate exudation into the soil. However, since this discovery other family members have been shown to have many other functions such as roles in stomatal opening, general anionic homoeostasis, and in economically valuable traits such as fruit flavour. Recent evidence has also shown that ALMT proteins can act as key molecular actors in GABA (γ-aminobutyric acid) signalling, the first evidence that GABA can act as a signal transducer in plants.

Receptive field of the retinal bipolar cell: a pharmacological study in the tiger salamander

1996 ◽  
Vol 76 (3) ◽  
pp. 2005-2019 ◽  
Author(s):  
W. A. Hare ◽  
W. G. Owen
Keyword(s):  
Receptive Field ◽  
Gaba Receptors ◽  
Bipolar Cell ◽  
Horizontal Cell ◽  
Pharmacological Study ◽  
Bipolar Cells ◽  
Horizontal Cells ◽  
Gaba Uptake ◽  
Gamma Aminobutyric Acid ◽  
Gabaergic Synapse

1. It is widely believed that signals contributing to the receptive field surrounds of retinal bipolar cells pass from horizontal cells to bipolar cells via GABAergic synapses. To test this notion, we applied gamma-aminobutyric acid (GABA) agonists and antagonists to isolated, perfused retinas of the salamander Ambystoma tigrinum while recording intracellularly from bipolar cells, horizontal cells, and photoreceptors. 2. As we previously reported, administration of the GABA analogue D-aminovaleric acid in concert with picrotoxin did not block horizontal cell responses or the center responses of bipolar cells but blocked the surround responses of both on-center and off-center bipolar cells. 3. Surround responses were not blocked by the GABA, antagonists picrotoxin or bicuculline, the GABAB agonist baclofen or the GABAB antagonist phaclofen, and the GABAC antagonists picrotoxin or cis-4-aminocrotonic acid. Combinations of these drugs were similarly ineffective. 4. GABA itself activated a powerful GABA uptake mechanism in horizontal cells for which nipecotic acid is a competitive agonist. It also activated, both in horizontal cells and bipolar cells, large GABAA conductances that shunted light responses but that could be blocked by picrotoxin or bicuculline. 5. GABA, administered together with picrotoxin to block the shunting effect of GABAA activation, did not eliminate bipolar cell surround responses at concentrations sufficient to saturate the known types of GABA receptors. 6. Surround responses were not blocked by glycine or its antagonist strychnine, or by combinations of drugs designed to eliminate GABAergic and glycinergic pathways simultaneously. 7. Although we cannot fully discount the involvement of a novel GABAergic synapse, the simplest explanation of our findings is that the primary pathway mediating the bipolar cell's surround is neither GABAergic nor glycinergic.

Depolarizing actions of GABA and glycine on amphibian retinal horizontal cells

1991 ◽  
Vol 65 (3) ◽  
pp. 680-692 ◽  
Author(s):  
R. A. Stockton ◽  
M. M. Slaughter
Keyword(s):  
Gabaa Receptor ◽  
Gaba Receptors ◽  
Ganglion Cells ◽  
Light Response ◽  
Feedback System ◽  
Horizontal Cells ◽  
Gaba Uptake ◽  
Gamma Aminobutyric Acid ◽  
Ion Substitution ◽  
Chemical Coupling

1. The effects of inhibitory amino acid transmitters on horizontal cells in the superfused amphibian retina were studied by the use of conventional intracellular recording techniques. 2. Gamma-aminobutyric acid (GABA) caused a calcium-independent depolarization of horizontal cells in mud puppy and tiger salamander. This action was mimicked by muscimol but not baclofen (BAC) and blocked by bicuculline and picrotoxin (PTX), matching the GABAa receptor profile. 3. The purported GABA uptake inhibitors nipecotate (NPA) and guvacine (GUV) acted as GABAa agonists, having pharmacological properties very similar to GABA itself. These agents also activated receptors of amacrine and ganglion cells, causing membrane polarizations similar to GABA. Concentrations of these analogues that did not activate the GABAa receptor (submillimolar) did not lower the effective dose of GABA, even after prolonged application. 4. Glycine (GLY) also depolarized horizontal cells, but only in approximately 25% of the horizontal cells was the amplitude of the depolarization as great as GABA. The glycine response was blocked by both strychnine (STR, 10 microM) and PTX (100 microM). In contrast, the action of GABA was unaffected by STR. 5. Ion substitution and channel-blocking agents indicated that the effects of applied GABA and GLY were independent of both external sodium and calcium. 6. The results suggest that GABA receptors on horizontal cells may act 1) as a positive feedback system to modulate the light response and 2) as a mechanism for chemical coupling between horizontal cells.

The dieca effect in the respiration of barley

1957 ◽  
Vol 147 (928) ◽  
pp. 309-315 ◽  
Keyword(s):  
Related Species ◽  
Oxidation Mechanism ◽  
Wheat Root ◽  
Barley Root ◽  
Root Tips ◽  
Full Agreement ◽  
Salt Uptake ◽  
System A ◽  
Simultaneous Comparison ◽  
Independent Work

Results previously described for the respiration of barley root tips lead to the conclusion that their cytochrome system temporarily gives way to a copper-dependent system a few days after germination. Independent work with related species does not suggest similar effects. A simultaneous comparison of barley and wheat root tips has therefore been carried out and has given results in full agreement with previous work for both species. The change, referred to here as ‘the dieca effect’, occurs in barley and not in wheat. It indicates that a drastic alteration of oxidation mechanism may occur in a rapidly growing tissue without apparent disturbance to growth or salt uptake by the tissue.

Structure of renal organic anion and cation transporters

2000 ◽  
Vol 278 (6) ◽  
pp. F853-F866 ◽  
Author(s):  
Gerhard Burckhardt ◽  
Natascha A. Wolff
Keyword(s):  
Transmembrane Domain ◽  
Organic Anion ◽  
Major Facilitator Superfamily ◽  
Anion Transporters ◽  
Transporter Family ◽  
Structural And Functional Properties ◽  
Large Extracellular Loop ◽  
Cation Transporters ◽  
Renal Proximal Tubular ◽  
Major Facilitator

Here we review the structural and functional properties of organic anion transporters (OAT1, OAT2, OAT3) and organic cation transporters (OCTN1, OCTN2, OCT1, OCT2, OCT3), some of which are involved in renal proximal tubular organic anion and cation secretion. These transporters share a predicted 12-transmembrane domain (TMD) structure with a large extracellular loop between TMD1 and TMD2, carrying potential N-glycosylation sites. Conserved amino acid motifs revealed a relationship to the sugar transporter family within the major facilitator superfamily. Following heterologous expression, most OATs transported the model anion p-aminohippurate (PAH). OAT1, but not OAT2, exhibited PAH-α-ketoglutarate exchange. OCT1–3 transported the model cations tetraethylammonium (TEA), N1-methylnicotinamide, and 1-methyl-4-phenylpyridinium. OCTNs exhibited transport of TEA and/or preferably the zwitterionic carnitine. Substrate substitution as well as cis-inhibition experiments demonstrated polyspecificity of the OATs, OCTs, and OCTN1. On the basis of comparison of the structurally closely related OATs and OCTs, it may be possible to delineate the binding sites for organic anions and cations in future experiments.

scholarly journals The switch of intestinal Slc26 exchangers from anion absorptive to HCO3−secretory mode is dependent on CFTR anion channel function

2010 ◽  
Vol 298 (5) ◽  
pp. C1057-C1065 ◽  
Author(s):  
Anurag Kumar Singh ◽  
Brigitte Riederer ◽  
Mingmin Chen ◽  
Fang Xiao ◽  
Anja Krabbenhöft ◽  
...  
Keyword(s):  
Anion Channel ◽  
Transport Activity ◽  
Wild Type ◽  
Regulatory Relationship ◽  
Genetic Ablation ◽  
Anion Transporters ◽  
Absolute Requirement ◽  
Heterologous Expression Systems ◽  
Deficient Mice ◽  
Nhe3 Inhibitor

CFTR has been recognized to function as both an anion channel and a key regulator of Slc26 anion transporters in heterologous expression systems. Whether this regulatory relationship between CFTR and Slc26 transporters is seen in native intestine, and whether this effect is coupled to CFTR transport function or other features of this protein, has not been studied. The duodena of anesthetized CFTR-, NHE3-, Slc26a6-, and Scl26a3-deficient mice and wild-type (WT) littermates were perfused, and duodenal bicarbonate (HCO3−) secretion (DBS) and fluid absorptive or secretory rates were measured. The selective NHE3 inhibitor S1611 or genetic ablation of NHE3 significantly reduced fluid absorptive rates and increased DBS. Slc26a6 (PAT1) or Slc26a3 (DRA) ablation reduced the S1611-induced DBS increase and reduced fluid absorptive rates, suggesting that the effect of S1611 or NHE3 ablation on HCO3−secretion may be an unmasking of Slc26a6- and Slc26a3-mediated Cl−/HCO3−exchange activity. In the absence of CFTR expression or after application of the CFTR(inh)-172, fluid absorptive rates were similar to those of WT, but S1611 induced virtually no increase in DBS, demonstrating that CFTR transport activity, and not just its presence, is required for Slc26-mediated duodenal HCO3−secretion. A functionally active CFTR is an absolute requirement for Slc26-mediated duodenal HCO3−secretion, but not for Slc26-mediated fluid absorption, in which these transporters operate in conjunction with the Na+/H+exchanger NHE3. This suggests that Slc26a6 and Slc26a3 need proton recycling via NHE3 to operate in the Cl−absorptive mode and Cl−exit via CFTR to operate in the HCO3−secretory mode.

Effects of glycine and GABA on bulbar respiratory neurons of cat

1990 ◽  
Vol 63 (5) ◽  
pp. 955-965 ◽  
Author(s):  
A. Haji ◽  
J. E. Remmers ◽  
C. Connelly ◽  
R. Takeda
Keyword(s):  
Membrane Potential ◽  
Amino Acid ◽  
Input Resistance ◽  
Postsynaptic Membrane ◽  
Chloride Ions ◽  
Membrane Receptors ◽  
Membrane Properties ◽  
Respiratory Neurons ◽  
Gaba Uptake ◽  
Gamma Aminobutyric Acid

1. Bulbar respiratory neurons of unanesthetized, decerebrate cats were impaled with the center pipette of a compound, coaxial microelectrode. This electrode allowed intracellular recording of membrane potential (MP) through the central pipette and extracellular iontophoresis of glycine or gamma-aminobutyric acid (GABA) from micropipettes encircling the center pipette with their tips recessed 20-40 microns from the tip of the center pipette. 2. Seventy-seven studies were carried out on 32 inspiratory and 28 postinspiratory neurons with the use of brief pulses (0.3-0.5 s) or long pulses (3-10 s) spanning one or more respiratory cycles. In both neuronal types, GABA and glycine decreased spike frequency, synaptic "noise," respiratory fluctuations of MP, and "input" resistance in a dose-related fashion. 3. In most cases, the membrane was hyperpolarized by the amino acid. The reverse response (depolarization) was observed when the membrane had been hyperpolarized by current clamp. This reversal from hyperpolarization to depolarization occurred at a MP of -81 +/- 2.3 mV (mean +/- SE, n = 7) for glycine and -81 +/- 1.6 (n = 6) for GABA. 4. After intracellular iontophoresis of chloride ions, application of GABA and glycine depolarized the membrane. 5. During relatively long (3-10 s) periods of iontophoresis of glycine or GABA, the effects on MP and input resistance waned. In some cases (23%), the amino acid depolarized the membrane at the most hyperpolarizated portion of the MP trajectory. This was never observed with brief iontophoretic pulses. Such effects of long duration iontophoresis may reflect changes in membrane properties secondary to the primary action of the amino acid on the membrane of the impaled neuron or indirect synaptic actions via changes in discharge of neighboring neurons. 6. Extracellular iontophoresis of a GABA uptake inhibitor, nipecotic acid, potentiated the effects of GABA. 7. Extracellular application of tetrodotoxin appeared to act pre- and postsynaptically to reduce respiratory fluctuations in membrane potential and to increase input resistance without altering the effects of iontophoresed glycine and GABA, suggesting that the amino acids act on postsynaptic membrane receptors not linked to fast sodium channels.(ABSTRACT TRUNCATED AT 400 WORDS)

scholarly journals Concurrent acetylcholinesterase staining and gamma-aminobutyric acid uptake of cortical neurons in culture.

1981 ◽  
Vol 29 (2) ◽  
pp. 306-308 ◽  
Author(s):  
M M Mesulam ◽  
M Dichter
Keyword(s):  
Tissue Culture ◽  
Cortical Neurons ◽  
Gabaergic Neurons ◽  
Aminobutyric Acid ◽  
Gaba Uptake ◽  
Acid Uptake ◽  
Gamma Aminobutyric Acid ◽  
Acetylcholinesterase Staining ◽  
Culture Positive

Gamma-aminobutyric acid (GABA) uptake and acetylcholinesterase (AChE) content were demonstrated concurrently in cortical neurons grown in tissue culture. Positive reactions either for GABA uptake or for AChE content were encountered in pyramidal and stellate, as well as spindle-shaped neurons. Neither reaction was confined to a specific morphological subtype. Nearly half the neurons were negative for either reaction. Most of the remaining neurons were positive only for GABA or only for AChE. However, a subpopulation of neurons showed not only a high AChE content, but also an avid GABA uptake. Thus, four types of neurons could be identified on the basis of these two reactions. The high AChE content in some of the cortical neurons that also showed GABA uptake indicates that there are at least two distinct types of GABAergic neurons.

scholarly journals Intracellular pH in rice and wheat root tips under hypoxic and anoxic conditions

2008 ◽  
Vol 3 (4) ◽  
pp. 240-242 ◽  
Author(s):  
Konstantin Y. Kulichikhin ◽  
Tamara V. Chirkova ◽  
Kurt V. Fagerstedt
Keyword(s):  
Intracellular Ph ◽  
Wheat Root ◽  
Root Tips ◽  
Anoxic Conditions
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