Activation of cardiac human ether-a-go-go related gene potassium currents is regulated by alpha(1A)-adrenoceptors.

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Thomas D, Wu K, Wimmer AB, Zitron E, Hammerling BC, Kathofer S, Lueck S, Bloehs R, Kreye VA, Kiehn J, Katus HA, Schoels W, Karle CA

Activation of cardiac human ether-a-go-go related gene potassium currents is regulated by alpha(1A)-adrenoceptors.

J Mol Med (Berl). 2004 Dec;82(12):826-37. doi: 10.1007/s00109-004-0582-8. Epub 2004 Sep 8.

PubMed ID

15365637 [ View in PubMed

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Abstract

Patients with cardiac disease typically develop life-threatening ventricular arrhythmias during physical or emotional stress, suggesting a link between adrenergic stimulation and regulation of the cardiac action potential. Human ether-a-go-go related gene (hERG) potassium channels conduct the rapid component of the repolarizing delayed rectifier potassium current, I(Kr). Previous studies have revealed that hERG channel activation is modulated by activation of the beta-adrenergic system. In contrast, the influence of the alpha-adrenergic signal transduction cascade on hERG currents is less well understood. The present study examined the regulation of hERG currents by alpha(1A)-adrenoceptors. hERG channels and human alpha(1A)-adrenoceptors were heterologously coexpressed in Xenopus laevis oocytes, and currents were measured using the two-microelectrode voltage clamp technique. Stimulation of alpha(1A)-receptors by applying 20 microM phenylephrine caused hERG current reduction due to a 9.6-mV shift of the activation curve towards more positive potentials. Simultaneous application of the alpha(1)-adrenoceptor antagonist prazosin (20 microM) prevented the activation shift. Inhibition of PKC (3 microM Ro-32-0432) or PKA (2.5 microM KT 5720) abolished the alpha-adrenergic activation shift, suggesting that PKC and PKA are required within the regulatory mechanism. The effect was still present when the PKA- and PKC-dependent phosphorylation sites in hERG were deleted by mutagenesis. In summary, cardiac repolarizing hERG/I(Kr) potassium currents are modulated by alpha(1A)-adrenoceptors via PKC and PKA independently of direct channel phosphorylation. This novel regulatory pathway of alpha1-adrenergic hERG current regulation provides a link between stress and ventricular arrhythmias, in particular in patients with heart disease.

DrugBank Data that Cites this Article

Drug Targets

Drug	Target	Kind	Organism	Pharmacological Action	Actions
Prazosin	Potassium voltage-gated channel subfamily H member 2	Protein	Humans	Unknown	Inhibitor	Details