アセチルコリンによる心筋カリウムチャネル活性化の分子機構

概要

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Recent progresses in the understandings of molecular mechanisms underlying activation of K+ channels by acetylcholine (ACh) were reviewed. Electrophysiological studies using patch clamp techniques revealed that GTP-binding proteins, whose functions are inhibited by pertussis toxin, couple m-ACh and adenosine receptors to a K+ channel in the cardiac cell membrane. The activation of G proteins by intracellular GTP analogues has an absolute requirement for intracellular Mg2+. During activation with GTP and Mg2+, G proteins may be dissociated into its subunits (α-GTP, βγ). Reoonstitutional experiments using purified subunits from bovine brain showed that βγ subunits can activate the K+ channel. A simple model for activation of the channel by G proteins has been proposed. Recently, it was shown that G proteins may also be involved in the short-term desensitization of the ACh-induced K+ channel current. The precise mechanisms of the desensitization is now awaited to be clarified.
日本生物物理学会の論文