Neuron 1996 Feb 01;162:423-9. doi: 10.1016/s0896-6273(00)80060-4.

Cloning of a Xenopus laevis inwardly rectifying K+ channel subunit that permits GIRK1 expression of IKACh currents in oocytes.

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Xenopus oocytes injected with GIRK1 mRNA express inwardly rectifying K+ channels resembling IKACh. Yet IKACh, the atrial G protein-regulated ion channel, is a heteromultimer of GIRK1 and CIR. Reasoning that an oocyte protein might be substituting for CIR, we cloned XIR, a CIR homolog endogenously expressed by Xenopus oocytes. Coinjecting XIR and GIRK1 mRNAs produced large, inwardly rectifying K+ currents responsive to m2-muscarinic receptor stimulation. The m2-stimulated currents of oocytes expressing GIRK1 alone decreased 80% after injecting antisense oligonucleotides specific to the 5' untranslated region of XIR, but GIRK1/CIR currents were unaffected. Thus, GIRK1 without XIR or CIR only ineffectively produces currents in oocytes. This result suggests that GIRK1 does not form native homomultimeric channels.

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Species referenced: Xenopus laevis
Genes referenced: cir1 kcnj3