Endogenous RGS proteins and Gα subtypes differentially control muscarinic and adenosine-mediated chronotropic effects

被引:77
作者
Fu, Y
Huang, XY
Zhong, HL
Mortensen, RM
D'Alecy, LG
Neubig, RR
机构
[1] Univ Michigan, Dept Pharmacol, Ann Arbor, MI 48109 USA
[2] Univ Michigan, Dept Mol & Integrat Physiol, Ann Arbor, MI 48109 USA
[3] Univ Michigan, Dept Vasc Surg, Ann Arbor, MI 48109 USA
[4] William Beaumont Hosp, Dept Surg, Royal Oak, MI 48072 USA
关键词
RGS; automaticity; adenosine receptor; beta(2) adrenergic receptor; muscarinic receptor;
D O I
10.1161/01.RES.0000207497.50477.60
中图分类号
R5 [内科学];
学科分类号
1002 ; 100201 ;
摘要
Cardiac automaticity is controlled by G protein-coupled receptors, such as adrenergic, muscarinic, and adenosine receptors. The strength and duration of G protein signaling is attenuated by regulator of G protein signaling (RGS) proteins acting as GTPase-activating proteins for G alpha subunits; however, little is known about the role of endogenous RGS proteins in cardiac function. We created point mutations in G alpha subunits that disrupt G alpha-RGS binding and introduced them into embryonic stem (ES) cells by homologous recombination. Spontaneously contacting cardiocytes derived from the ES cells were used to evaluate the role of endogenous RGS proteins in chronotropic regulation. The RGS-insensitive G alpha(o)G184S homozygous knock-in (G alpha(o)GS/GS) cells demonstrated enhanced adenosine A(1) and muscarinic M-2 receptor-mediated bradycardic responses. In contrast, G alpha(i2)GS/GS cells showed enhanced responses to M-2 but not A(1) receptors. Similarly M-2 but not A(1) bradycardic responses were dramatically enhanced in G alpha(i2)GS/GS mice. Blocking G protein-coupled inward rectifying K+ (GIRK) channels largely abolished the mutation-induced enhancement of the M-2 receptor-mediated response but had a minimal effect on A(1) responses. The G alpha(s)-dependent stimulation of beating rate by the beta(2) adrenergic receptor agonist procaterol was significantly attenuated in G alpha(o)GS/GS and nearly abolished in G alpha(i2)GS/GS cells because of enhanced signaling via a pertussis toxin sensitive mechanism. Thus, endogenous RGS proteins potently reduce the actions of G alpha(i/o)-linked receptors on cardiac automaticity. Furthermore, M-2 and A(1) receptors differentially use G alpha(i2) and G alpha(o) and associated downstream effectors. Thus, alterations in RGS function may play a role in pathophysiological processes and RGS proteins could represent novel cardiovascular therapeutic targets.
引用
收藏
页码:659 / 666
页数:8
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