Cloning provides evidence for a family of inward rectifier and G‐protein coupled K⁺ channels in the brain

Abstract

MbIRK3, mbGIRK2 and mbGIRK3 K' channels cDNAs have been cloned from adult mourn brain. These cDNAs encode polypeptides of 445,414 and 376 amino acids, respectively, which display the hallmarks of inward rectifier K+ channels, i.e. two hydrophobic membrane-spanning domains Ml and M2 and a pore-forming domain H5. MbIRK3 shows around 65% amino acid identity with IRK1 and rbIRK2 and only 50% with ROMKl and GIRKl. On the other hand, mbGIRK2 and mbGIRK3 are more similar to GIRKl (60%) than to ROMKl and IRK1 (50%). Northern blot analysis reveals that these three novel clones are mainly expressed in the brain. Xenopus oocytes injected with mbIRK3 and mbGIRK2 cRNAs display inward rectifier K+-selective currents very similar to IRK1 and GIRKl , respectively. As expected from the sequence homology, mbGIRK2 cRNA directs the expression of G-protein coupled inward rectityer K' channels which has been observed through their functional coupling with 1.

Activation of heteromeric G protein-gated inward rectifier K + channels overexpressed by adenovirus gene transfer inhibits the excitability of hippocampal neurons

“…All bands were blocked by preabsorption with the immunogenic fusion protein (data not shown). The higher molecular weight of the GIRK2 protein in adult hippocampus (49 kDa) vs. the AdGIRK2-expressed 46 kDa protein may indicate the expression of a longer, alternatively spliced GIRK2 isoform in adult hippocampus (31) or may be due to unknown posttranslational modifications. Quantitative comparison of these bands indicates an 8-fold overexpression of GIRK2 protein, equivalent to the GIRK1 data.…”

Heteromeric channel formation and Ca2+‐free media reduce the toxic effect of the weaver Kir 3.2 allele

“…The weaver gene has been localised and a point mutation, G953A, identified in the weaver gene which encodes a G-protein coupled inward rectifier potassium channel subunit, Kir 3.2 [3][4][5]. This mutation results in a single amino acid substitution, G156S, in the putative pore region of the channel.…”

Agonist unbinding from receptor dictates the nature of deactivation kinetics of G protein-gated K + channels

“…G protein-gated Kir channels are also expressed in many central neurones, where they can be activated by a large variety of neurotransmitters acting at G i/o -coupled receptors (10) including ␥-aminobutyric acid (GABA) at the GABA type B (GABA B ) receptor complex and adenosine at A 1 receptors, and they mediate postsynaptic inhibitory events (9,11,12). The molecular counterparts of these currents have now been identified by cloning techniques (13)(14)(15)(16): the channel is a heterotetramer of members of the Kir3.0 family of K ϩ channels. Coexpression of Kir3.1 with Kir3.2 or Kir3.4 in heterologous expression systems results in currents that show many of the basic characteristics of the native channels in neurones and atria, respectively.…”