Frontiers in Cellular Neuroscience (Dec 2013)

The contribution of TWIK-1 channels to astrocyte K+ current is limited by retention in intracellular compartments

  • Wei eWang,
  • Adhytia ePutra,
  • Gary P. Schools,
  • Baofeng eMa,
  • Haijun eChen,
  • Leonard K. Kaczmarek,
  • Jacques eBarhanin,
  • Florian eLesage,
  • Min eZhou

DOI
https://doi.org/10.3389/fncel.2013.00246
Journal volume & issue
Vol. 7

Abstract

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TWIK-1 two-pore domain K+ channels are expressed abundantly in astrocytes. In the present study, we examined the extent to which TWIK-1 contributes to the linear current-voltage (I-V) relationship (passive) K+ membrane conductance, a dominant electrophysiological feature of mature hippocampal astrocytes. Astrocytes from TWIK-1 knockout mice have a more negative resting potential than those from wild type animals and a reduction in both inward rectification and Cs+ permeability. Nevertheless, the overall whole-cell passive conductance was not altered significantly in TWIK-1 knockout astrocytes. The expression of Kir4.1 and TREK-1, two other major astrocytic K+ channels, or of other two-pore K+ channels was not altered in TWIK-1 knockout mice, suggesting that the mild effect of TWIK knockout does not result from compensation by these channels. Fractionation experiments showed that TWIK-1 is primarily localized in intracellular cytoplasmic fractions (55%) and mildly hydrophobic internal compartment fraction (41%), with only 5% in fractions containing plasma membranes. Our study revealed that TWIK-1 proteins are mainly located in the intracellular compartments of hippocampal astrocyte under physiological condition, therefore a minimal contribution of TWIK-1 channels to whole-cell currents is likely attributable to a relatively low level presence of channels in the plasma membrane.

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