Calcium influx mediated by the inwardly rectifying K super(+) channel Kir4.1 (KCNJ10) at low external K super(+) concentration

• Published in: Cell calcium (Edinburgh) Vol. 42; no. 3; pp. 271 - 280
• Main Authors: Hartel, K, Singaravelu, K, Kaiser, M, Neusch, C, Hulsmann, S, Deitmer, J W
• Format: Journal Article
• Language: English
• Published: 01.09.2007
• ISSN: 0143-4160
• DOI: 10.1016/j.ceca.2006.12.004

COS-1 cells with heterologeous expression of the Kir4.1 (KCNJ10) channel subunit, possess functional Kir4.1 channels and become capable to generating cytosolic Ca super(2) super(+) transients, upon lowering of the extracellular K super(+) concentration to 2mM or below. These Ca super(2) super(+) transients are blocked by external Ba super(2) super(+) (100 mu M). Acute brain stem slices from wild-type mice (second post-natal week), which were loaded with the fluorescent Ca super(2) super(+) indicator Oregon Green BAPTA-1-AM, were exposed to 0.2mM K super(+). Under these conditions astrocytes, but not neurons, responded with cytosolic Ca super(2) super(+) 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 super(-) super(/) super(-)) mice, the number of responding cells was dramatically reduced and the Ca super(2) super(+) 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 Ca super(2) super(+) influx in astrocytes under conditions of low external K super(+)-concentration.