Dynamics of forward and reverse transport by the glial glycine transporter, glyt1b.
Biophys J
; 89(3): 1657-68, 2005 Sep.
Article
in En
| MEDLINE
| ID: mdl-15951392
ABSTRACT
Glycine is a coagonist at the N-methyl-D-aspartate receptor. Changes in extracellular glycine concentration may modulate N-methyl-D-aspartate receptor function and excitatory synaptic transmission. The GLYT1 glycine transporter is present in glia surrounding excitatory synapses, and plays a key role in regulating extracellular glycine concentration. We investigated the kinetic and other biophysical properties of GLYT1b, stably expressed in CHO cells, using whole-cell patch-clamp techniques. Application of glycine produced an inward current, which decayed within a few seconds to a steady-state level. When glycine was removed, a transient outward current was observed, consistent with reverse transport of accumulated glycine. The outward current was enhanced by elevating intracellular or lowering extracellular [Na(+)], and was modulated by changes in extracellular [glycine] and time of glycine application. We developed a model of GLYT1b function, which accurately describes the time course of the transporter current under a range of experimental conditions. The model predicts that glial uptake of glycine will decay toward zero during a sustained period of elevated glycine concentration. This property of GLYT1b may permit spillover from glycinergic terminals to nearby excitatory terminals during a prolonged burst of inhibitory activity, and reverse transport may extend the period of elevated glycine concentration beyond the end of the inhibitory burst.
Full text:
1
Collection:
01-internacional
Database:
MEDLINE
Main subject:
Biophysics
/
Glycine Plasma Membrane Transport Proteins
/
Glycine
Type of study:
Prognostic_studies
Limits:
Animals
Language:
En
Journal:
Biophys J
Year:
2005
Document type:
Article
Affiliation country:
Australia