ACTIVATION OF MUSCARINIC K-ADRENERGIC RECEPTORS IN CULTURED ATRIAL MYOCYTES TRANSFECTED WITH BETA(1) SUBUNIT OF HETEROTRIMERIC G-PROTEINS( CURRENT BY BETA)

Muscarinic K+ channels (I-K(ACh)) in native atrial myocytes are activa ted by beta gamma subunits of pertussis toxin (Ptx)-sensitive heterotr imeric G proteins coupled to different receptors. beta gamma subunits of Ptx-insensitive G(s), coupled to beta-adrenergic receptors, do not activate native IK(ACh) In atrial myocytes from adult rats transfected with rat brain B-1 subunit IK(ach) can be activated by stimulation of beta-adrenergic receptors using isoprenaline. This effect is insensit ive to Ptx. These findings demonstrate for the first time promiscuous (Ptx-insensitive) coupling of G(s beta gamma) to GIRK channels in thei r native environment. (C) 1998 Federation of European Biochemical Soci eties.