Reconstitution in lipid bilayer of smooth muscle cation channels activated through a GTP-binding protein.
Reconstitution of G-protein-coupled receptor activated cation channels into the lipid bilayer was attempted with plasma membrane vesicles prepared from guinea-pig ileal smooth muscle using the purification technique previously applied to the large conductance Ca2+-dependent and ATP-sensitive K+ channels (Toro et al., 1990). Under Na+-rich conditions, incorporation of plasma membrane vesicles into the bilayer produced GTPgammaS (100 microM)-activatable channel activities that are inhibited by GDPbetaS (1 mM), sensitive to Ca2+ and enhanced by depolarization. The reversal potential and unitary conductance (tens of picosiemens) of these channels varied in a manner dependent on Na+ concentration, but not affected by Cl-. These results strongly indicate that the reconstituted channels activated by GTPgammaS belong to a class of voltage-dependent, Ca2+-sensitive cation-selective channels that are activated through a G-protein, and correspond most likely to the muscarinic receptor-activated cation channels previously identified in the same preparation. These results also suggest potential usefulness of bilayer incorporation technique to investigate the receptor-operated cation channels in smooth muscle.
Doira
N
N
Department of Pharmacology, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan.
Hanano
T
T
Onoue
H
H
Nakano
H
H
Ito
Y
Y
Inoue
R
R
D000818:Animals; D019204:GTP-Binding Proteins / Q000378:metabolism* / Q000494:pharmacology; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000494:pharmacology; D006153:Guanosine Diphosphate / Q000031:analogs & derivatives* / Q000494:pharmacology; D006168:Guinea Pigs; D007082:Ileum; D051036:Large-Conductance Calcium-Activated Potassium Channels; D008051:Lipid Bilayers / Q000378:metabolism*; D009130:Muscle, Smooth / Q000378:metabolism* / Q000502:physiology; D015221:Potassium Channels / Q000502:physiology*; D024681:Potassium Channels, Calcium-Activated / Q000502:physiology*; D012964:Sodium / Q000378:metabolism; D013873:Thionucleotides / Q000494:pharmacology
D051036:Large-Conductance Calcium-Activated Potassium Channels; D008051:Lipid Bilayers; D015221:Potassium Channels; D024681:Potassium Channels, Calcium-Activated; D013873:Thionucleotides; D006153:Guanosine Diphosphate; D016244:Guanosine 5'-O-(3-Thiotriphosphate); C023427:guanosine 5'-O-(2-thiodiphosphate); D012964:Sodium; D019204:GTP-Binding Proteins