Overexpression of the Large-Conductance, Ca2+-Activated K+ (BK) Channel Shortens Action Potential Duration in HL-1 Cardiomyocytes.
Ontology highlight
ABSTRACT: Long QT syndrome is characterized by a prolongation of the interval between the Q wave and the T wave on the electrocardiogram. This abnormality reflects a prolongation of the ventricular action potential caused by a number of genetic mutations or a variety of drugs. Since effective treatments are unavailable, we explored the possibility of using cardiac expression of the large-conductance, Ca2+-activated K+ (BK) channel to shorten action potential duration (APD). We hypothesized that expression of the pore-forming ? subunit of human BK channels (hBK?) in HL-1 cells would shorten action potential duration in this mouse atrial cell line. Expression of hBK? had minimal effects on expression levels of other ion channels with the exception of a small but significant reduction in Kv11.1. Patch-clamped hBK? expressing HL-1 cells exhibited an outward voltage- and Ca2+-sensitive K+ current, which was inhibited by the BK channel blocker iberiotoxin (100 nM). This BK current phenotype was not detected in untransfected HL-1 cells or in HL-1 null cells sham-transfected with an empty vector. Importantly, APD in hBK?-expressing HL-1 cells averaged 14.3 ± 2.8 ms (n = 10), which represented a 53% reduction in APD compared to HL-1 null cells lacking BK? expression. APD in the latter cells averaged 31.0 ± 5.1 ms (n = 13). The shortened APD in hBK?-expressing cells was restored to normal duration by 100 nM iberiotoxin, suggesting that a repolarizing K+ current attributed to BK channels accounted for action potential shortening. These findings provide initial proof-of-concept that the introduction of hBK? channels into a cardiac cell line can shorten APD, and raise the possibility that gene-based interventions to increase hBK? channels in cardiac cells may hold promise as a therapeutic strategy for long QT syndrome.
SUBMITTER: Stimers JR
PROVIDER: S-EPMC4474436 | biostudies-literature | 2015
REPOSITORIES: biostudies-literature
ACCESS DATA
