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Functional interaction between aquaporins and Kir4.1/Kir4.1‐Kir5.1 channels
Author(s) -
Søe Rikke,
Klærke Dan Arne
Publication year - 2007
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.21.5.a540-d
Subject(s) - aquaporin , xenopus , aquaporin 4 , microbiology and biotechnology , chemistry , aquaporin 1 , homeostasis , water transport , cell , osmotic concentration , cell membrane , cell type , biophysics , biology , biochemistry , water channel , gene , water flow , mechanical engineering , environmental engineering , inlet , engineering
In the CNS glial cells, Kir4.1 and Kir4.1‐Kir5.1 channels are involved in clearance of K + during neuronal activity. A number of studies have shown that Kir channels are co‐localized with aquaporins (AQP4) in the glial cells, and coupled water and K + influx is suggested to underlie activity‐induced glial cell swelling. Recently aquaporin knockout studies have indicated that aquaporins participate in water as well as in K + clearance from the ECS after neuronal activity. A number of K + channels are dramatically regulated by small changes in cell volume when co‐expressed with aquaporins in mammalian cells and Xenopus oocytes. To test a possible functional interaction between Kir channels and aquaporins, Kir4.1 or Kir4.1–5.1 were co‐expressed in Xenopus oocytes in presence or absence of co‐expressed aquaporins and subsequently challenged with osmotic changes of up to ±75mOsm resulting in fast cell volume changes of up to ±11%. The results showed that Kir 4.1 and Kir4.1–5.1 were activated by 16 to 18% during cell swelling at physiological [K + ] O and membrane potential clamped at −70 mV. In absence of co‐expressed aquaporins changes in osmolarity had no effect. In conclusion, our results imply that during K + clearance into glial cells the local cell swelling mediated through the influx of osmotically obliged water will further increase the activity of the Kir channels in a positive feed‐back manner.