Molecular cloning and functional expression of a novel brain-specific inward rectifier potassium channel.
We have cloned a novel brain-specific inward rectifier K+ channel from a mouse brain cDNA library and designated it MB-IRK3. The mouse brain cDNA library was screened using a fragment of the mouse macrophage inward rectifier K+ channel (IRK1) cDNA as a probe. The amino acid sequence of MB-IRK3 shares 61% and 64% identity to MB-IRK1 and RB-IRK2, respectively. Xenopus oocytes injected with cRNA derived from this clone expressed a potassium current which showed inward-rectifying channel characteristics similar to MB-IRK1 and RB-IRK2 currents, but distinct from ROMK1 or GIRK1 current. However, the single channel conductance of MB-IRK3 was approximately 10 pS with 140 mM extracellular K+, which was distinct from that of MB-IRK1 (20 pS). MB-IRK3 mRNA expressed specifically in the forebrain, which clearly differed from MB-IRK1 and RB-IRK2 mRNAs. These results indicate that members of the IRK family with distinct electrophysiological properties express differentially and may play heterogenous functional roles in brain functions.
Morishige
K
K
Department of Internal Medicine, Mayo Clinic, Rochester, MN 55905.
Takahashi
N
N
Jahangir
A
A
Yamada
M
M
Koyama
H
H
Zanelli
J S
JS
Kurachi
Y
Y
D000595:Amino Acid Sequence; D000818:Animals; D001464:Barium / Q000494:pharmacology; D001483:Base Sequence; D001923:Brain Chemistry; D003001:Cloning, Molecular; D004553:Electric Conductivity; D004594:Electrophysiology; D005260:Female; D015870:Gene Expression; D018014:Gene Transfer Techniques; D008564:Membrane Potentials; D051379:Mice; D008969:Molecular Sequence Data; D009865:Oocytes / Q000378:metabolism; D015221:Potassium Channels / Q000737:chemistry / Q000235:genetics* / Q000502:physiology; D024661:Potassium Channels, Inwardly Rectifying; D012333:RNA, Messenger / Q000032:analysis; D014018:Tissue Distribution; D014981:Xenopus
D015221:Potassium Channels; D024661:Potassium Channels, Inwardly Rectifying; D012333:RNA, Messenger; D001464:Barium