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.
Soe
Rikke
R
Department of Physiology and Biochemistry, IBHV, Faculty of Life Sciences, University of Copenhagen, Grønnegaardsvej 7, 1870 Frederiksberg C, Denmark. rso@life.ku.dk
Macaulay
Nanna
N
Klaerke
Dan Arne
DA
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