A NOVEL ATP-DEPENDENT INWARD RECTIFIER POTASSIUM CHANNEL EXPRESSED PREDOMINANTLY IN GLIAL-CELLS

We have isolated a novel inward rectifier K+ channel predominantly expressed in glial cells of the central nervous system. Its amino acid sequence exhibited 53% identity with ROMK1 and approximately 40% identity with other inward rectifier K+ channels. Xenopus oocytes injected with cRNA derived from this clone expressed a K+ current, which showed classical inward rectifier K+ channel characteristics. Intracenular Mg . ATP was required to sustain channel activity in excised membrane patches, which is consistent with a Walker type-ii ATP-binding domain on this clone. We designate this new clone as K-AB-2 (the second type of inward rectifying K+ channel with an ATP-binding domain). In situ hybridization showed K-AB-2 mRNA to be expressed predominantly in glial cells of the cerebellum and forebrain. This is the first description of the cloning of a glial cell inward rectifier potassium channel, which may be responsible for K+ buffering action of glial cells in the brain.