Key result
Double transgenic mice expressing both SUR1 and Kir6.2[ΔN30,K185Q] in the heart exhibited premature death and a constellation of arrhythmias compared to wild-type or single transgenic littermates.
Expression of hyperactive K(ATP) channels comprised of SUR1 and Kir6.2[DeltaN30,K185Q] in the heart is proarrhythmic and leads to premature death in mice.
May indicate proarrhythmic risk from cardiac KATP hyperactivity; hypothesis-generating and requires human validation.
Sarcolemmal ATP-sensitive potassium (K(ATP)) channels are activated after pathological depletion of intracellular ATP, unlike their pancreatic beta-cell counterparts, which dynamically regulate membrane excitability in response to changes in blood glucose. We recently engineered a series of transgenic (TG) mice overexpressing an ATP-insensitive inward rectifying K(+) channel protein (Kir)6.2 mutant (Kir6.2[DeltaN30,K185Q]) or the accessory sulfonylurea receptor (SUR)2A (FLAG-SUR2A) or SUR1 (FLAG-SUR1) subunits of the K(ATP) channel, under transcriptional control of the alpha-myosin heavy chain promoter. In the present study, we generated double transgenic (DTG) animals overexpressing both Kir6.2[DeltaN30,K185Q] and FLAG-SUR1 or FLAG-SUR2A and examined the effects on cardiac excitability in vivo. No animals expressing both FLAG-SUR1 and Kir6.2[DeltaN30,K185Q] transgenes at a high level were obtained. DTG mice expressing one transgene at a high level and the other at a lower level are born, but they die prematurely. Electrocardiographic analysis of both anesthetized and conscious animals revealed a constellation of arrhythmias in DTG animals, but not in wild-type or single TG littermates. The proarrhythmic effect of the transgene combination is intrinsic to the myocardium, since it persists in isolated hearts. Importantly, this effect is specific for SUR1-expressing DTG animals: DTG animals expressing both Kir6.2[DeltaN30,K185Q] and FLAG-SUR2A at high levels exhibit neither impaired survival nor increased arrhythmia frequency, even with both subunits expressed at high levels. In demonstrating the profound arrhythmic consequences of K(ATP) channels comprised of SUR1 and Kir6.2[DeltaN30,K185Q] in the myocardium specifically, the results highlight the critical differential activation of SUR1 versus SUR2A, and indicate that expression of hyperactive K(ATP) in the heart is likely to be proarrhythmic.
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Flagg et al. (2007) studied Arrhythmia susceptibility. Overexpression of both SUR1 and Kir6.2[ΔN30,K185Q] vs. Wild-type, single TG littermates, or SUR2A DTG mice was evaluated on Arrhythmias and premature death. Double transgenic mice expressing both SUR1 and Kir6.2[ΔN30,K185Q] in the heart exhibited premature death and a constellation of arrhythmias compared to wild-type or single transgenic littermates.
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