Phosphorylation of the I-Ks channel complex inhibits drug block - Novel mechanism underlying variable antiarrhythmic drug actions

Article

关键词: POTASSIUM CHANNEL;    CHROMANOL 293B;    MODULATION;    MYOCYTES;    REQUIREMENT;    HEART;   

DOI  :  10.1161/01.CIR.0000082708.86266.B8

来源: SCIE

【 摘 要 】

Background-I-Ks, an important repolarizing current in heart, is an antiarrhythmic drug target and is markedly increased by activation of protein kinase A (PKA; eg, by beta-adrenergic stimulation). Because beta-adrenergic stimulation is a frequent trigger of arrhythmias, we hypothesized that PKA stimulation inhibits drug block. Methods and Results-CHO cells were transfected with KCNQ1 cDNA ( encoding the pore-forming subunit) with or without the ancillary subunit KCNE1. IC50 for quinidine block of basal I-Ks was 5.8 +/- 1.2 mumol/L, versus 19.9 +/- 3.2 mumol/L (P < 0.01) for PKA-stimulated current. A similar >3-fold shift was apparent in the absence of KCNE1 and with the I-Ks-specific blocker chromanol 293B. The first current recorded after channels were held at rest and exposed to the drug was reduced approximate to40%, and further depolarizations increased the block with a time constant (tau) of 181 +/- 27 seconds. By contrast, PKA-stimulated channels displayed a <5% first-pulse block and much slower block development (τ = 405 +/- 85 seconds). Alanine substitution at 3 potential PKA target sites (S27, S468, and T470) generated an I-Ks that did not increase with PKA stimulation; this mutant retained wild-type drug sensitivity that was unaffected by PKA. Conclusions-Activation of this key intracellular signaling pathway blunts drug block. The onset of block and the data with the PKA-resistant mutant support the concept that phosphorylation of the KCNQ1 subunit directly modulates drug access to a binding site on the channel. These data identify a novel mechanism for modulation of drug-channel interactions that may be especially important during β-adrenergic stimulation.

【 授权许可】

Free