How potassium came to be the dominant biological cation: of metabolism, chemiosmosis, and cation selectivity since the beginnings of life

BioEssays ◽  
2020 ◽  
Vol 43 (1) ◽  
pp. 2000108 ◽  
Author(s):  
Nikolay Korolev
Keyword(s):  
Cation Selectivity

Cation selectivity and inhibition of malignant glioma Na+ channels by Psalmotoxin 1

2004 ◽  
Vol 287 (5) ◽  
pp. C1282-C1291 ◽  
Author(s):  
James K. Bubien ◽  
Hong-Long Ji ◽  
G. Yancey Gillespie ◽  
Catherine M. Fuller ◽  
James M. Markert ◽  
...  
Keyword(s):  
Malignant Gliomas ◽  
Outward Current ◽  
Whole Cell ◽  
Amino Acid Peptide ◽  
Cation Selectivity ◽  
Astrocytoma Cells ◽  
Acid Sensing Ion Channels ◽  
Inward Currents ◽  
Cell Current ◽  
Peptide Toxin

Psalmotoxin 1 (a component of the venom of a West Indies tarantula) is a 40-amino acid peptide that inhibits cation currents mediated by acid-sensing ion channels (ASIC). In this study we performed electrophysiological experiments to test the hypothesis that Psalmotoxin 1 (PcTX1) inhibits Na+ currents in high-grade human astrocytoma cells (glioblastoma multiforme, or GBM). In whole cell patch-clamped cultured GBM cells, the peptide toxin quickly and reversibly inhibited both inward and outward current with an IC50 of 36 ± 2 pM. The same inhibition was observed in freshly resected GBM cells. However, when the same experiment was performed on normal human astrocytes, the toxin failed to inhibit the whole cell current. We also determined a cationic selectivity sequence for inward currents in three cultured GBM cell lines (SK-MG-1, U87-MG, and U251-MG). The selectivity sequence yielded a unique biophysical fingerprint with inward K+ conductance approximately fourfold greater than that of Na+, Li+, and Ca2+. These observations suggest that PcTX1 may prove useful in determining whether GBM cells express a specific ASIC-containing ion channel type that can serve as a target for both diagnostic and therapeutic treatments of aggressive malignant gliomas.

Cover Picture: Ionophoric Properties of [14]Tetraazaannulene Derivatives and Substituent Effect on the Cation-selectivity (Electroanalysis 7/2017)

2017 ◽  
Vol 29 (7) ◽  
pp. 1659-1659
Author(s):  
T. M. Kawakami ◽  
M. Obita ◽  
T. Tsujinaka ◽  
A. Higashikado ◽  
T. Moriuchi
Keyword(s):  
Substituent Effect ◽  
Cation Selectivity

Perfect divalent cation selectivity with capacitive deionization

2021 ◽  
pp. 117959
Author(s):  
Rana Uwayid ◽  
Eric N. Guyes ◽  
Amit Shocron ◽  
Jack Gilron ◽  
Menachem Elimelech ◽  
...  
Keyword(s):  
Divalent Cation ◽  
Capacitive Deionization ◽  
Cation Selectivity

scholarly journals Characterization of the R162W Kir7.1 mutation associated with snowflake vitreoretinopathy

2013 ◽  
Vol 304 (5) ◽  
pp. C440-C449 ◽  
Author(s):  
Wei Zhang ◽  
Xiaoming Zhang ◽  
Hui Wang ◽  
Anil K. Sharma ◽  
Albert O. Edwards ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Expression System ◽  
Dominant Negative ◽  
Dominant Negative Effect ◽  
Xenopus Laevis Oocyte ◽  
Cation Selectivity ◽  
Negative Effect ◽  
Dominant Disease ◽  
Vitreoretinal Degeneration ◽  
Inwardly Rectifying

KCNJ13 encodes Kir7.1, an inwardly rectifying K+ channel that is expressed in multiple ion-transporting epithelia. A mutation in KCNJ13 resulting in an arginine-to-tryptophan change at residue 162 (R162W) of Kir7.1 was associated with snowflake vitreoretinal degeneration, an inherited autosomal-dominant disease characterized by vitreous degeneration and mild retinal degeneration. We used the Xenopus laevis oocyte expression system to assess the functional properties of the R162W (mutant) Kir7.1 channel and determine how wild-type (WT) Kir7.1 is affected by the presence of the mutant subunit. Recordings obtained via the two-electrode voltage-clamp technique revealed that injection of oocytes with mutant Kir7.1 cRNA resulted in currents and cation selectivity that were indistinguishable from those in water-injected oocytes, suggesting that the mutant protein does not form functional channels in the plasma membrane. Coinjection of oocytes with equal amounts of mutant and WT Kir7.1 cRNAs resulted in inward K+ and Rb+ currents with amplitudes that were ∼17% of those in oocytes injected with WT Kir7.1 cRNA alone, demonstrating a dominant-negative effect of the mutant subunit. Similar to oocytes injected with WT Kir7.1 cRNA alone, coinjected oocytes exhibited inwardly rectifying Rb+ currents that were more than seven times larger than K+ currents, indicating that mutant subunits did not alter Kir7.1 channel selectivity. Immunostaining of Xenopus oocytes or Madin-Darby canine kidney cells expressing mutant or WT Kir7.1 demonstrated distribution of both proteins primarily in the plasma membrane. Our data suggest that the R162W mutation suppresses Kir7.1 channel activity, possibly by negatively impacting gating by membrane phosphadidylinositol 4,5-bisphosphate.

Activation of recombinant trp by thapsigargin in Sf9 insect cells

1994 ◽  
Vol 267 (5) ◽  
pp. C1501-C1505 ◽  
Author(s):  
L. Vaca ◽  
W. G. Sinkins ◽  
Y. Hu ◽  
D. L. Kunze ◽  
W. P. Schilling
Keyword(s):  
Expression System ◽  
Cation Selectivity ◽  
Drosophila Protein ◽  
Insect Cell Expression System ◽  
Cell Expression ◽  
Insect Cell Expression ◽  
Mammalian Protein ◽  
Entry Mechanism ◽  
Proline Rich Region ◽  
Cell Expression System

The mammalian protein responsible for Ca2+ release-activated current (Icrac) may be homologous to the Drosophila protein designated trp. Thus the activity of trp, and another Drosophila protein designated trp-like or trpl, may be linked to depletion of the internal Ca2+ store via the so-called capacitative Ca2+ entry mechanism. To test this hypothesis, the effect of thapsigargin, a selective inhibitor of the endoplasmic reticulum Ca2+ pump, on trp- and trpl-induced whole cell membrane current was determined using the baculovirus Sf9 insect cell expression system. The results demonstrate that trp and trpl form Ca(2+)-permeable cation channels. The trpl encodes a nonselective cation channel that is constitutively active under basal nonstimulated conditions and is unaffected by thapsigargin, whereas trp is more selective for Ca2+ than Na+ and is activated by depletion of the internal Ca2+ store. Although evaluation of cation selectivity suggests that trp is not identical to the channel responsible for Icrac, these channels must share some structural feature(s) since both are activated by thapsigargin. A unique proline-rich region in the COOH-terminal tail of trp, which is absent in trpl, may be necessary for capacitative Ca2+ entry.

scholarly journals A Model for Predicting Cation Selectivity and Permeability in AMPA and NMDA Receptors Based on Receptor Subunit Composition

2021 ◽  
Vol 13 ◽  
Author(s):  
Sampath Kumar ◽  
Sanjay S. Kumar
Keyword(s):  
Experimental Data ◽  
Divalent Cations ◽  
Ion Selectivity ◽  
Gene Families ◽  
Subunit Composition ◽  
Receptor Subunit ◽  
Cation Selectivity ◽  
Subunit Stoichiometry ◽  
Ampa And Nmda Receptors

Glutamatergic AMPA (α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid) and NMDA (N-methyl-D-aspartate) receptors are implicated in diverse functions ranging from synaptic plasticity to cell death. They are heterotetrameric proteins whose subunits are derived from multiple distinct gene families. The subunit composition of these receptors determines their permeability to monovalent and/or divalent cations, but it is not entirely clear how this selectivity arises in native and recombinantly-expressed receptor populations. By analyzing the sequence of amino acids lining the selectivity filters within the pore forming membrane helices (M2) of these subunits and by correlating subunit stoichiometry of these receptors with their ability to permeate Na+ and/or Ca2+, we propose here a mathematical model for predicting cation selectivity and permeability in these receptors. The model proposed is based on principles of charge attractivity and charge neutralization within the pore forming region of these receptors; it accurately predicts and reconciles experimental data across various platforms including Ca2+ permeability of GluA2-lacking AMPARs and ion selectivity within GluN3-containing di- and tri-heteromeric NMDARs. Additionally, the model provides insights into biophysical mechanisms regulating cation selectivity and permeability of these receptors and the role of various subunits in these processes.

scholarly journals Tuning the ion selectivity of glutamate transporter–associated uncoupled conductances

2016 ◽  
Vol 148 (1) ◽  
pp. 13-24 ◽  
Author(s):  
Rosemary J. Cater ◽  
Robert J. Vandenberg ◽  
Renae M. Ryan
Keyword(s):  
Excitatory Amino Acid ◽  
Ion Selectivity ◽  
Glutamate Transporter ◽  
Amino Acid Transporters ◽  
Primary Role ◽  
Cation Selectivity ◽  
Anion Selectivity ◽  
Transport Domain ◽  
Cl Conductance

The concentration of glutamate within a glutamatergic synapse is tightly regulated by excitatory amino acid transporters (EAATs). In addition to their primary role in clearing extracellular glutamate, the EAATs also possess a thermodynamically uncoupled Cl− conductance. This conductance is activated by the binding of substrate and Na+, but the direction of Cl− flux is independent of the rate or direction of substrate transport; thus, the two processes are thermodynamically uncoupled. A recent molecular dynamics study of the archaeal EAAT homologue GltPh (an aspartate transporter from Pyrococcus horikoshii) identified an aqueous pore at the interface of the transport and trimerization domains, through which anions could permeate, and it was suggested that an arginine residue at the most restricted part of this pathway might play a role in determining anion selectivity. In this study, we mutate this arginine to a histidine in the human glutamate transporter EAAT1 and investigate the role of the protonation state of this residue on anion selectivity and transporter function. Our results demonstrate that a positive charge at this position is crucial for determining anion versus cation selectivity of the uncoupled conductance of EAAT1. In addition, because the nature of this residue influences the turnover rate of EAAT1, we reveal an intrinsic link between the elevator movement of the transport domain and the Cl− channel.

Cation selectivity coefficient variations in acidic forest soils from Sutton, Québec

Geoderma ◽  
1995 ◽  
Vol 68 (4) ◽  
pp. 301-308 ◽  
Author(s):  
Sébastien Sauvé ◽  
William H. Hendershot
Keyword(s):  
Forest Soils ◽  
Selectivity Coefficient ◽  
Cation Selectivity

Structure and Cation Selectivity of Unsymmetrical Bis(Crown Ether)s

Heterocycles ◽  
1984 ◽  
Vol 21 (2) ◽  
pp. 761
Author(s):  
Toshihiko Ikeda ◽  
Kiyoshi Kikukawa ◽  
Tsutomu Matsuda
Keyword(s):  
Crown Ether ◽  
Cation Selectivity
Sign in / Sign up

Export Citation Format

Share Document