Cloning and expression of a novel human brain inward rectifier potassium channel.
A complementary DNA encoding an inward rectifier K+ channel (HRK1) was isolated from human hippocampus using a 392-base pair cDNA (HHCMD37) as a probe. HRK1 shows sequence similarity to three recently cloned inwardly rectifying potassium channels (IRK1, GIRK1, and ROMK1, 60, 42, and 37%, respectively) and has a similar proposed topology of two membrane spanning domains that correspond to the inner core structure of voltage gated K+ channels. When HRK1 was expressed in Xenopus oocytes, large inward K+ currents were observed below the K+ reversal potential but very little outward K+ current was observed. In on-cell membrane patches, single channel conductance (g) was estimated to be 10 picosiemens by both direct measurement and noise analysis, in 102 mM external [K+]. HRK1 currents were blocked by external Ba2+ and Cs+ (K(0) = 183 microM, and K(-130) = 30 microM, respectively), and internal tetraethylammonium ion (K(0) = 62 microM), but were insensitive to external tetraethylammonium ion. The functional properties of HRK1 are very similar to those of glial cell inward rectifier K+ channels and HRK1 may represent a glial cell inward rectifier.
Makhina
E N
EN
Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri 63110.
Kelly
A J
AJ
Lopatin
A N
AN
Mercer
R W
RW
Nichols
C G
CG
D000595:Amino Acid Sequence; D000818:Animals; D001464:Barium / Q000494:pharmacology; D001483:Base Sequence; D001921:Brain / Q000378:metabolism*; D002586:Cesium / Q000494:pharmacology; D003001:Cloning, Molecular; D018076:DNA, Complementary; D006801:Humans; D008564:Membrane Potentials / Q000187:drug effects; D008969:Molecular Sequence Data; D026902:Potassium Channel Blockers; D015221:Potassium Channels / Q000235:genetics*; D024661:Potassium Channels, Inwardly Rectifying; D017386:Sequence Homology, Amino Acid; D014981:Xenopus
D018076:DNA, Complementary; C099489:KCNJ4 protein, human; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D024661:Potassium Channels, Inwardly Rectifying; D002586:Cesium; D001464:Barium