Modulation of Kir4.1 and Kir4.1-Kir5.1 channels by small changes in cell volume.
The K+ channels Kir4.1 and Kir4.1-Kir5.1 are expressed in the glial cells of the CNS and are involved in regulation of the K+ homeostasis. Several studies have shown that Kir4.1 channels are co-localized with aquaporins (AQP4) in the glial endfeet, and a putative functional coupling between the Kir channels and aquaporins is therefore debated. To test a possible volume-sensitivity of the Kir channels, the Kir4.1 or Kir4.1-Kir5.1 channels were expressed in Xenopus oocytes with or without co-expression of aquaporins and subsequently exposed to cell volume alterations. Our results show an increase in Kir4.1 and Kir4.1-Kir5.1 currents upon swelling of the oocytes and a reduction in the current when the oocytes were shrunk. The volume-dependent changes in channel activity were not due to changes in the kinetics of the channels. These findings implicate a putative functional interaction between the Kir channels and aquaporins via small, fast cell volume changes in the glial cells.
Department of Physiology and Biochemistry, IBHV, Faculty of Life Sciences, University of Copenhagen, Grønnegaardsvej 7, 1870 Frederiksberg C, Denmark. rso@life.ku.dk
Rikke
R
Soe
Nanna
N
Macaulay
Dan Arne
DA
Klaerke
D000818:Animals; D051398:Aquaporin 1 / Q000378:metabolism; D051401:Aquaporin 4 / Q000378:metabolism; D048429:Cell Size; D006801:Humans; D008564:Membrane Potentials / Q000502:physiology; D009865:Oocytes / Q000166:cytology* / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D024661:Potassium Channels, Inwardly Rectifying / Q000378:metabolism*; D051381:Rats; D014982:Xenopus laevis; D000097062:Kir5.1 Channel; D000098854:Kcnj10 Channel
D051398:Aquaporin 1; D051401:Aquaporin 4; D024661:Potassium Channels, Inwardly Rectifying; D000097062:Kir5.1 Channel; D000098854:Kcnj10 Channel