Article Information
PubMed
Related Articles
- Anion Competition for a Volume-Regulated CurrentAnion Competition for a Volume-Regulated Current
Biophysical Journal, Volume 75, Issue 1, 1 July 1998, Pages 226-235
Irena Levitan and Sarah S. Garber
AbstractWe have examined whether the anionic amino acids, glutamate and aspartate, permeate through the same volume-regulated conductance permeant to Cl ions. Cell swelling was initiated in response to establishing a whole-cell configuration in the presence of a hyposmotic gradient. Volume-regulated anion currents carried by Cl, glutamate, or aspartate developed with similar time courses and showed similar voltage-dependent inactivation. Permeability ratios (/) calculated from measured reversal potentials were dependent on the mole fraction ratio (MFR) of the permeant anions ([aa]/([aa]+[Cl])). MFR was varied from 0.00 to 0.97. As the fraction of amino acid increased, / decreased. Current amplitude was similarly dependent on MFR. These results show that the permeation of anionic amino acids and that of Cl ions are not independent of each other, indicating that the ion channel underlying the volume-regulated conductance can be occupied by more than one ion at a time. Application of Eyring rate theory indicated that the major barrier to Cl ion permeation is at the intracellular side of the membrane, and that the major barrier to amino acid permeation is at the extracellular side of the membrane. The interactions between these permeant ions may have a physiological modulatory role in volume regulation through a volume-regulated anion conductance.
Abstract | Full Text | PDF (206 kb) - Nonsynaptic Glycine Receptor Activation during Early Neocort...Nonsynaptic Glycine Receptor Activation during Early Neocortical Development
Neuron, Volume 20, Issue 1, 1 January 1998, Pages 43-53
Alexander C Flint, Xiaolin Liu and Arnold R Kriegstein
SummaryGlycine receptors (GlyRs) contribute to fast inhibitory synaptic transmission in the brain stem and spinal cord. GlyR subunits are expressed in the developing neocortex, but a neurotransmitter system involving cortical GlyRs has yet to be demonstrated. Here, we show that GlyRs in immature neocortex are excitatory and activated by a nonsynaptically released endogenous ligand. Of the potential ligands for cortical GlyRs, taurine is by far the most abundant in the developing neocortex. We found that taurine is stored in immature cortical neurons and that manipulations known to elevate extracellular taurine cause GlyR activation. These data indicate that nonsynaptically released taurine activates GlyRs during neocortical development. As fetal taurine deprivation can cause cortical dysgenesis, it is possible that taurine influences neocortical development by activating GlyRs.
Summary | Full Text | PDF (438 kb) - Integration of sodium and osmosensory signals in vasopressin...Integration of sodium and osmosensory signals in vasopressin neurons
Trends in Neurosciences, Volume 25, Issue 4, 1 April 2002, Pages 199-205
Daniel L. Voisin and Charles W. Bourque
AbstractRecent studies provide cellular and molecular insights on how changes in osmotic pressure and sodium concentration are detected and integrated in central osmoregulatory neurons.
Abstract | Full Text | PDF (259 kb) - …more
Copyright © 1997 The Biophysical Society. All rights reserved.
Biophysical Journal, Volume 72, Issue 1, 141-145, 1 January 1997
doi:10.1016/S0006-3495(97)78653-3
Research Article
Anion, cation, and zwitterion selectivity of phospholemman channel molecules
G.C. Kowdley, S.J. Ackerman, Z. Chen, G. Szabo, L.R. Jones and J.R. Moorman
Abstract
Phospholemman (PLM), a 72-amino acid membrane protein with a single transmembrane domain, forms taurine-selective ion channels in lipid bilayers. Because taurine forms zwitterions, a taurine-selective channel might have binding sites for both anions and cations. Here we show that PLM channels indeed allow fluxes of both cations and anions, making instantaneous and voltage-dependent transitions among conformations with drastically different ion selectivity characteristics. This surprising and novel ion channel behavior offers a molecular explanation for selective taurine flux across cell membranes and may explain why molecules in the phospholemman family can induce cation- or anion-selective conductances when expressed in Xenopus oocytes.
