人心房肌细胞超极化激活电流（If）的药理学调控：聚焦于G蛋白偶联受体

Pharmacological modulation of the hyperpolarization-activated current (I f) in human atrial myocytes: focus on G protein-coupled receptors.

作者信息

Lonardo Giuseppe, Cerbai Elisabetta, Casini Simona, Giunti Gabriele, Bonacchi Massimo, Battaglia Francesco, Fiorani Brenno, Stefano Pier Luigi, Sani Guido, Mugelli Alessandro

机构信息

Department of Preclinical and Clinical Pharmacology, University of Florence, Viale Pieraccini 6, 50139 Florence, Italy.

出版信息

J Mol Cell Cardiol. 2005 Mar;38(3):453-60. doi: 10.1016/j.yjmcc.2004.12.010.

DOI:10.1016/j.yjmcc.2004.12.010

PMID:15733905

Abstract

AIMS

In human atrial myocytes (HuAM) two beta-adrenergic receptors (beta-AR) and four splicing-variants of the serotonin 5-HT(4) receptor are present. Multiple coupling with G stimulatory (G(s)) and G inhibitory (G(i)) proteins has been proposed for both beta(2)-AR and 5-HT((4b)) subtypes, but no functional data exist in HuAM. Serotonin (5-HT) and catecholamines are able to trigger arrhythmias in human atrium, but the underlying cellular mechanisms are not completely understood. The pacemaker current (I(f)) is an inward Na(+)/K(+) current, constitutively present in HuAM and directly modulated by cAMP; I(f) could play a role in triggering human atrial arrhythmias. This study evaluated the different G protein coupling of beta(1)-AR, beta(2)-AR and 5-HT(4) receptors by assessing the modulation of I(f) by selective stimuli.

METHODS

HuAM were isolated from right atrial appendages and utilized for patch-clamp recording. The coupling of receptor subtypes with G(i) proteins was tested by incubating HuAM in pertussis toxin (PTX).

RESULTS

Beta(1)-AR stimulation (Isoprenaline [ISO] + ICI 118,551), and 5-HT caused a concentration-dependent significant shift of the half activation potential of I(f) activation curve (DeltaV(h)), P < 0.01. beta(2)-AR stimulation (ISO 1 microM + CGP 20712A) also significantly shifted V(h) (P < 0.0001), but with DeltaV(h)[beta(2)-AR] significantly smaller than the effect caused by 1 microM beta(1)-AR stimulation (P < 0.05). Pre-treatment of HuAM with PTX did not alter the effect of beta(1)-AR stimulation (both 0.1 and 1 microM) and 1 microM 5-HT on I(f), but significantly increased the effect in response to beta(2)-AR stimulation and 0.1 microM 5-HT (P < 0.05 for both), thus suggesting a G(i) protein coupling of these receptors.

CONCLUSIONS

Our results provide the first functional evidence of the different G protein coupling of beta(1)-AR, beta(2)-AR and 5-HT(4) receptors in HuAM. Further they support the view that I(f) current might play an important role in triggering catecholamines and serotonin-induced atrial arrhythmias.

摘要

目的

在人心房肌细胞（HuAM）中存在两种β-肾上腺素能受体（β-AR）和5-羟色胺5-HT(4)受体的四种剪接变体。已提出β(2)-AR和5-HT((4b))亚型均与刺激性G蛋白（G(s)）和抑制性G蛋白（G(i)）存在多种偶联，但在HuAM中尚无功能数据。5-羟色胺（5-HT）和儿茶酚胺能够引发人房性心律失常，但其潜在的细胞机制尚未完全明确。起搏电流（I(f)）是一种内向Na(+)/K(+)电流，在HuAM中持续存在并受cAMP直接调节；I(f)可能在引发人房性心律失常中发挥作用。本研究通过评估选择性刺激对I(f)的调节作用，来评价β(1)-AR、β(2)-AR和5-HT(4)受体与不同G蛋白的偶联情况。

方法

从右心耳分离HuAM并用于膜片钳记录。通过将HuAM与百日咳毒素（PTX）孵育来检测受体亚型与G(i)蛋白的偶联情况。

结果

β(1)-AR刺激（异丙肾上腺素[ISO]+ICI 118,551）和5-HT可使I(f)激活曲线的半激活电位发生浓度依赖性显著偏移（ΔV(h)），P<0.01。β(2)-AR刺激（1μM ISO+CGP 20712A）也显著使V(h)发生偏移（P<0.0001），但ΔV(h)[β(2)-AR]显著小于1μMβ(1)-AR刺激所产生的效应（P<0.05）。用PTX预处理HuAM不会改变β(1)-AR刺激（0.1μM和1μM）和1μM 5-HT对I(f)的作用，但会显著增强对β(2)-AR刺激和0.1μM 5-HT的反应（两者P均<0.05），从而提示这些受体与G(i)蛋白偶联。