Reconstitution in Lipid Bilayer of Smooth Muscle Cation Channels Activated Through a GTP-Binding Protein

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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 Ca^<2+>-dependent and ATP-sensitive K^+ channels(Toro et al., 1990). Under Na^+ -rich conditions, incorporation of plasma membrane vesicles into the bilayer produced GTPγS(100 μM)-activatable channel activities that are inhibited by GDPβS(1mM), sensitive to Ca^<2+> 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 GTPγS belong to a class of voltage-dependent, Ca^<2+>-sensitive cationselective 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.
日本平滑筋学会の論文