Functional characterization of NIPA2, a selective Mg2+ transporter

2008 ◽  
Vol 295 (4) ◽  
pp. C944-C953 ◽  
Author(s):  
Angela Goytain ◽  
Rochelle M. Hines ◽  
Gary A. Quamme
Keyword(s):  
Plasma Membrane ◽  
Functional Characterization ◽  
Affinity Constant ◽  
Fluorescence Studies ◽  
Low Magnesium ◽  
Early Endosomes ◽  
Electrode Voltage ◽  
Voltage Dependent ◽  
Transmembrane Regions

We used microarray analysis to identify renal cell transcripts that were upregulated with low magnesium. One transcript, identified as NIPA2 (nonimprinted in Prader-Willi/Angelman syndrome) subtype 2, was increased over twofold relative to cells cultured in normal magnesium. The deduced sequence comprises 129 amino acids with 8 predicted transmembrane regions. As the secondary structure of NIPA2 conformed to a membrane transport protein, we expressed it in Xenopus oocytes and determined that it mediated Mg2+ uptake with two-electrode voltage-clamp and fluorescence studies. Mg2+ transport was electrogenic, voltage dependent, and saturable, demonstrating a Michaelis affinity constant of 0.31 mM. Unlike other reported Mg2+ transporters, NIPA2 was very selective for the Mg2+ cation. NIPA2 mRNA is found in many tissues but particularly abundant in renal cells. With the use of immunofluorescence, it was shown that NIPA2 protein was normally localized to the early endosomes and plasma membrane and was recruited to the plasma membrane in response to low extracellular magnesium. We conclude that NIPA2 plays a role in magnesium metabolism and regulation of renal magnesium conservation.

scholarly journals Functional Characterization of the Oxantel-Sensitive Acetylcholine Receptor from Trichuris muris

2021 ◽  
Vol 14 (7) ◽  
pp. 698
Author(s):  
Tina V. A. Hansen ◽  
Richard K. Grencis ◽  
Mohamed Issouf ◽  
Cédric Neveu ◽  
Claude L. Charvet
Keyword(s):  
Single Dose ◽  
Mouse Model ◽  
Xenopus Laevis ◽  
Acetylcholine Receptor ◽  
Drug Target ◽  
Functional Characterization ◽  
Xenopus Laevis Oocytes ◽  
Trichuris Muris ◽  
Electrode Voltage

The human whipworm, Trichuris trichiura, is estimated to infect 289.6 million people globally. Control of human trichuriasis is a particular challenge, as most anthelmintics have a limited single-dose efficacy, with the striking exception of the narrow-spectrum anthelmintic, oxantel. We recently identified a novel ACR-16-like subunit from the pig whipworm, T. suis which gave rise to a functional acetylcholine receptor (nAChR) preferentially activated by oxantel. However, there is no ion channel described in the mouse model parasite T. muris so far. Here, we have identified the ACR-16-like and ACR-19 subunits from T. muris, and performed the functional characterization of the receptors in Xenopus laevis oocytes using two-electrode voltage-clamp electrophysiology. We found that the ACR-16-like subunit from T. muris formed a homomeric receptor gated by acetylcholine whereas the ACR-19 failed to create a functional channel. The subsequent pharmacological analysis of the Tmu-ACR-16-like receptor revealed that acetylcholine and oxantel were equally potent. The Tmu-ACR-16-like was more responsive to the toxic agonist epibatidine, but insensitive to pyrantel, in contrast to the Tsu-ACR-16-like receptor. These findings confirm that the ACR-16-like nAChR from Trichuris spp. is a preferential drug target for oxantel, and highlights the pharmacological difference between Trichuris species.

scholarly journals Functional characterization of a novel plasma membrane intrinsic protein2 in barley

2012 ◽  
Vol 7 (12) ◽  
pp. 1648-1652 ◽  
Author(s):  
Mineo Shibasaka ◽  
Sizuka Sasano ◽  
Sigeko Utsugi ◽  
Maki Katsuhara
Keyword(s):  
Plasma Membrane ◽  
Functional Characterization

Functional characterization of human NBC4 as an electrogenic Na+-HCO 3 − cotransporter (NBCe2)

2002 ◽  
Vol 282 (6) ◽  
pp. C1278-C1289 ◽  
Author(s):  
Leila V. Virkki ◽  
Darren A. Wilson ◽  
Richard D. Vaughan-Jones ◽  
Walter F. Boron
Keyword(s):  
Human Heart ◽  
Functional Characterization ◽  
Reversal Potential ◽  
Regulatory Function ◽  
Disulfonic Acid ◽  
Xenopus Laevis Oocytes ◽  
Slow Recovery ◽  
Bicarbonate Transporter ◽  
Electrode Voltage

We have functionally characterized Na+-driven bicarbonate transporter (NBC)4, originally cloned from human heart by Pushkin et al. (Pushkin A, Abuladze N, Newman D, Lee I, Xu G, and Kurtz I. Biochem Biophys Acta 1493: 215–218, 2000). Of the four NBC4 variants currently present in GenBank, our own cloning efforts yielded only variant c. We expressed NBC4c (GenBank accession no. AF293337 ) in Xenopus laevis oocytes and assayed membrane potential ( V m) and pH regulatory function with microelectrodes. Exposing an NBC4c-expressing oocyte to a solution containing 5% CO2 and 33 mM HCO[Formula: see text]elicited a large hyperpolarization, indicating that the transporter is electrogenic. The initial CO2-induced decrease in intracellular pH (pHi) was followed by a slow recovery that was reversed by removing external Na+. Two-electrode voltage clamp of NBC4c-expressing oocytes revealed large HCO[Formula: see text]- and Na+-dependent currents. When we voltage clamped V m far from NBC4c's estimated reversal potential ( E rev), the pHirecovery rate increased substantially. Both the currents and pHi recovery were blocked by 200 μM 4,4′-diisothiocyanostilbene-2,2′-disulfonic acid (DIDS). We estimated the transporter's HCO[Formula: see text]:Na+ stoichiometry by measuring E rev at different extracellular Na+ concentration ([Na+]o) values. A plot of E rev against log[Na+]o was linear, with a slope of 54.8 mV/log[Na+]o. This observation, as well as the absolute E rev values, are consistent with a 2:1 stoichiometry. In conclusion, the behavior of NBC4c, which we propose to call NBCe2-c, is similar to that of NBCe1, the first electrogenic NBC.

Functional characterization of a plasma membrane Na+/H+ antiporter from alkali grass (Puccinellia tenuiflora)

2010 ◽  
Vol 38 (7) ◽  
pp. 4813-4822 ◽  
Author(s):  
Xin Wang ◽  
Ru Yang ◽  
Baichen Wang ◽  
Guifeng Liu ◽  
Chuanping Yang ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Functional Characterization ◽  
Puccinellia Tenuiflora

scholarly journals RsSOS1 Responding to Salt Stress Might Be Involved in Regulating Salt Tolerance by Maintaining Na+ Homeostasis in Radish (Raphanus sativus L.)

Horticulturae ◽  
2021 ◽  
Vol 7 (11) ◽  
pp. 458
Author(s):  
Wanting Zhang ◽  
Jingxue Li ◽  
Junhui Dong ◽  
Yan Wang ◽  
Liang Xu ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Salt Stress ◽  
Salt Tolerance ◽  
Functional Characterization ◽  
Vital Role ◽  
Salt Stress Response ◽  
Reading Frame ◽  
Yield And Quality

Radish is a kind of moderately salt-sensitive vegetable. Salt stress seriously decreases the yield and quality of radish. The plasma membrane Na+/H+ antiporter protein Salt Overly Sensitive 1 (SOS1) plays a crucial role in protecting plant cells against salt stress, but the biological function of the RsSOS1 gene in radish remains to be elucidated. In this study, the RsSOS1 gene was isolated from radish genotype ‘NAU-TR17’, and contains an open reading frame of 3414 bp encoding 1137 amino acids. Phylogenetic analysis showed that RsSOS1 had a high homology with BnSOS1, and clustered together with Arabidopsis plasma membrane Na+/H+ antiporter (AtNHX7). The result of subcellular localization indicated that the RsSOS1 was localized in the plasma membrane. Furthermore, RsSOS1 was strongly induced in roots of radish under 150 mmol/L NaCl treatment, and its expression level in salt-tolerant genotypes was significantly higher than that in salt-sensitive ones. In addition, overexpression of RsSOS1 in Arabidopsis could significantly improve the salt tolerance of transgenic plants. Meanwhile, the transformation of RsSOS1△999 could rescue Na+ efflux function of AXT3 yeast. In summary, the plasma membrane Na+/H+ antiporter RsSOS1 plays a vital role in regulating salt-tolerance of radish by controlling Na+ homeostasis. These results provided useful information for further functional characterization of RsSOS1 and facilitate clarifying the molecular mechanism underlying salt stress response in radish.

scholarly journals Discovery and characterization of Hv1-type proton channels in reef-building corals.

2021 ◽  
Author(s):  
Gisela Rangel-Tescas ◽  
Cecilia Cervantes ◽  
Miguel A Cervantes-Rocha ◽  
Esteban Suarez-Delgado ◽  
Anastazia T Banaszak ◽  
...  
Keyword(s):  
Voltage Dependence ◽  
Ph Regulation ◽  
Functional Characterization ◽  
Gene Encoding ◽  
Proton Channels ◽  
Gating Model ◽  
Mechanistic Insight ◽  
Voltage Dependent ◽  
Insight Into

Voltage-dependent proton-permeable channels are membrane proteins mediating a number of important physiological functions. Here we report the presence of a gene encoding for Hv1 voltage-dependent, proton-permeable channels in two species of reef-building corals. We performed a characterization of their biophysical properties and found that these channels are fast-activating and modulated by the pH gradient in a manner that makes them interesting models for studying these processes more easily. We have also developed an allosteric gating model that provides mechanistic insight into the modulation of voltage-dependence by protons. This work also represents the first functional characterization of any ion channel in scleractinian corals. We discuss the implications of the presence of these channels in the membranes of coral cells in the calcification and pH regulation processes and possible consequences of ocean acidification related to the function of these channels.

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