Regulation of [gamma-3H]aminobutyric acid transport by Ca2+ in isolated synaptic plasma membrane vesicles

Brain Res Mol Brain Res. 1997 Nov;51(1-2):106-14. doi: 10.1016/s0169-328x(97)00223-4.

Abstract

We studied the effect of Ca2+ on the transport of the gamma-aminobutyric acid (GABA) by synaptic plasma membrane (SPM) vesicles isolated from sheep brain cortex and observed that intravesicular Ca2+ inhibits the [3H]GABA accumulation in a concentration-dependent manner. This inhibitory effect of Ca2+ exhibited two distinct components: one in the micromolar range of Ca2+ concentration, and the other in the millimolar range. Previous EGTA washing of the membranes, or incorporation of trifluoperazine into the vesicular space reduced the inhibitory action of Ca2+, particularly at low Ca2+ (1-5 microM). Okadaic acid (1 microM) also relieved the Ca2+ inhibition at low, but not at high Ca2+ concentrations (1 mM), whereas the calpain inhibitor I did not alter the effect of the low Ca2+, but it partially reduced (approximately 28%) the effect of Ca2+ in the millimolar range. The results indicate that the GABA transporter is regulated by low Ca2+ concentration (microM) and probably its effect is mediated by the (Ca2+ x calmodulin)-stimulated phosphatase 2B (calcineurin). In contrast, the GABA uptake inhibition observed at high Ca2+ concentrations (1 mM) is less specific, and probably it is partially related to the proteolytic activity of membrane bound calpain II.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Biological Transport / drug effects
  • Calcium / metabolism*
  • Calcium / pharmacology*
  • Calmodulin / antagonists & inhibitors
  • Carrier Proteins / drug effects
  • Carrier Proteins / metabolism*
  • Cerebral Cortex / metabolism*
  • Egtazic Acid / pharmacology
  • GABA Plasma Membrane Transport Proteins
  • Ionomycin / pharmacology
  • Kinetics
  • Membrane Proteins / drug effects
  • Membrane Proteins / metabolism*
  • Membrane Transport Proteins*
  • Organic Anion Transporters*
  • Sheep
  • Synaptic Membranes / drug effects
  • Synaptic Membranes / metabolism*
  • Trifluoperazine / pharmacology
  • Tritium
  • Valinomycin / pharmacology
  • gamma-Aminobutyric Acid / metabolism*
  • p-Methoxy-N-methylphenethylamine / pharmacology

Substances

  • Calmodulin
  • Carrier Proteins
  • GABA Plasma Membrane Transport Proteins
  • Membrane Proteins
  • Membrane Transport Proteins
  • Organic Anion Transporters
  • Tritium
  • Valinomycin
  • Trifluoperazine
  • p-Methoxy-N-methylphenethylamine
  • Egtazic Acid
  • gamma-Aminobutyric Acid
  • Ionomycin
  • Calcium