Pre-steady-state and reverse transport currents in the GABA transporter GAT1

Francesca Cherubino, Simone Bertram, Elena Bossi, Antonio Peres

Research output: Contribution to journalArticlepeer-review

Abstract

The role of internal substrates in the biophysical properties of the GABA transporter GAT1 has been investigated electrophysiologically in Xenopus oocytes heterologously expressing the cotransporter. Increments in Cl - and/or Na + concentrations caused by intracellular injections did not produce significant effects on the pre-steady-state currents, while a positive shift of the charge-voltage (Q-V) and decay time constant (τ)-voltage (τ-V) curves, together with a slowing of τ at positive potentials, was observed following treatments producing cytosolic Cl- depletion. Activation of the reverse transport mode by injections of GABA caused a reduction in the displaced charge. In the absence of external Cl -, a stronger reduction in the displaced charge, together with a significant increase in reverse transport current, was observed. Therefore, complementarity between pre-steady-state and transport currents, observed in the forward mode, is preserved in the reverse mode. All these findings can be qualitatively reproduced by a kinetic scheme in which, in the forward mode, the Cl - ion is released first, after the inward charge movement, while the two Na + ions can be released only after binding of external GABA. In the reverse mode, internal GABA must bind first to the empty transporter, followed by internal Na + and Cl -.

Original languageEnglish
JournalAmerican Journal of Physiology - Cell Physiology
Volume302
Issue number8
DOIs
Publication statusPublished - Apr 15 2012

Keywords

  • Chloride ion
  • Kinetic scheme
  • Modeling
  • Oocytes

ASJC Scopus subject areas

  • Cell Biology
  • Physiology

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