Calcium influx mediated by the inwardly rectifying K+ channel Kir4.1 (KCNJ10) at low external K+ concentration.
COS-1 cells with heterologeous expression of the Kir4.1 (KCNJ10) channel subunit, possess functional Kir4.1 channels and become capable to generating cytosolic Ca2+ transients, upon lowering of the extracellular K+ concentration to 2 mM or below. These Ca2+ transients are blocked by external Ba2+ (100 microM). Acute brain stem slices from wild-type mice (second post-natal week), which were loaded with the fluorescent Ca2+ indicator Oregon Green BAPTA-1-AM, were exposed to 0.2 mM K+. Under these conditions astrocytes, but not neurons, responded with cytosolic Ca2+ elevations in wild-type mice. This astrocyte-specific response has previously been used to identify astroglial cells type [R. Dallwig, H. Vitten, J.W. Deitmer, A novel barium-sensitive calcium influx into rat astrocytes at low external potassium. Cell Calcium 28 (2000) 247-259]. In Kir4.1 knock-out (Kir4.1-/-) mice, the number of responding cells was dramatically reduced and the Ca2+ transients in responding cells were significantly smaller than in wild-type mice. Our results indicate that Kir4.1 channels are the molecular substrate for the observed Ca2+ influx in astrocytes under conditions of low external K+-concentration.
Härtel
Kai
K
Department of Neuro- and Sensory Physiology, Georg-August-University Göttingen, Humboldtallee 23, 37073 Göttingen, Germany.
Singaravelu
Karthika
K
Kaiser
Melanie
M
Neusch
Clemens
C
Hülsmann
Swen
S
Deitmer
Joachim W
JW
D000814:Aniline Compounds / Q000378:metabolism; D000818:Animals; D001253:Astrocytes / Q000166:cytology / Q000378:metabolism; D019556:COS Cells; D002118:Calcium / Q000378:metabolism*; D002522:Chlorocebus aethiops; D005452:Fluoresceins / Q000378:metabolism; D005456:Fluorescent Dyes / Q000378:metabolism; D008564:Membrane Potentials; D051379:Mice; D018345:Mice, Knockout; D018408:Patch-Clamp Techniques; D011188:Potassium / Q000378:metabolism*; D024661:Potassium Channels, Inwardly Rectifying / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D000098854:Kcnj10 Channel
D000814:Aniline Compounds; D005452:Fluoresceins; D005456:Fluorescent Dyes; D000098854:Kcnj10 Channel; C503942:Oregon green 488 BAPTA-1; D024661:Potassium Channels, Inwardly Rectifying; D011993:Recombinant Fusion Proteins; D011188:Potassium; D002118:Calcium