Key result
M4 mAChR co-expression with GIRK1 couples to activate inwardly rectifying K+ currents.
Why the study?
The specificity of coupling of M3 and M4 muscarinic acetylcholine receptor isoforms to the GIRK1 channel was not determined.
The study demonstrates a new function for the M4 mAChR and a high degree of specificity for coupling of each muscarinic receptor subtype to the inward-rectifying K+ channel GIRK1.
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M3 couples to GIRK1 in oocytes; leaves open receptor-channel specificity and functional roles in native heart or brain.
Gadbut et al. (1996) studied this question. Co-expression of GIRK1 with chick M2, M3, or M4 mAChR was evaluated on Carbamylcholine-stimulated K+ currents. Co-expression of GIRK1 with chick M2 or M4 mAChR in Xenopus oocytes produced carbamylcholine-stimulated K+ currents, demonstrating a new function for the M4 mAChR.
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