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Downregulation of Kir4.1 inward rectifying potassium channel subunits by RNAi impairs potassium transfer and glutamate uptake by cultured cortical astrocytes†
Article first published online: 7 NOV 2006
Copyright © 2006 Wiley-Liss, Inc.
Volume 55, Issue 3, pages 274–281, February 2007
How to Cite
Kucheryavykh, Y. V., Kucheryavykh, L. Y., Nichols, C. G., Maldonado, H. M., Baksi, K., Reichenbach, A., Skatchkov, S. N. and Eaton, M. J. (2007), Downregulation of Kir4.1 inward rectifying potassium channel subunits by RNAi impairs potassium transfer and glutamate uptake by cultured cortical astrocytes. Glia, 55: 274–281. doi: 10.1002/glia.20455
- Issue published online: 8 DEC 2006
- Article first published online: 7 NOV 2006
- Manuscript Accepted: 4 OCT 2006
- Manuscript Revised: 20 SEP 2006
- Manuscript Received: 29 MAR 2006
- NIH. Grant Numbers: NIH-NINDS-S11-NS48201, NIH-MBRS-SO6-GM50695, NIH-NCRR-RCMI-G12RR03035
- Interdisziplinäres Zentrum für Klinische Forschung, Medical Faculty of the Universität Leipzig (project C05)
- K+ buffering;
- glutamate clearance;
- RNA interference
Glial cell-mediated potassium and glutamate homeostases play important roles in the regulation of neuronal excitability. Diminished potassium and glutamate buffering capabilities of astrocytes result in hyperexcitability of neurons and abnormal synaptic transmission. The role of the different K+ channels in maintaining the membrane potential and buffering capabilities of cortical astrocytes has not yet been definitively determined due to the lack of specific K+ channel blockers. The purpose of the present study was to assess the role of the inward-rectifying K+ channel subunit Kir4.1 on potassium fluxes, glutamate uptake and membrane potential in cultured rat cortical astrocytes using RNAi, whole-cell patch clamp and a colorimetric assay. The membrane potentials of control cortical astrocytes had a bimodal distribution with peaks at −68 and −41 mV. This distribution became unimodal after knockdown of Kir4.1, with the mean membrane potential being shifted in the depolarizing direction (peak at −45 mV). The ability of Kir4.1-suppressed cells to mediate transmembrane potassium flow, as measured by the current response to voltage ramps or sequential application of different extracellular [K+], was dramatically impaired. In addition, glutamate uptake was inhibited by knock-down of Kir4.1-containing channels by RNA interference as well as by blockade of Kir channels with barium (100 μM). Together, these data indicate that Kir4.1 channels are primarily responsible for significant hyperpolarization of cortical astrocytes and are likely to play a major role in potassium buffering. Significant inhibition of glutamate clearance in astrocytes with knock-down of Kir4.1 highlights the role of membrane hyperpolarization in this process. © 2006 Wiley-Liss, Inc.