Abstract-Cardiac I Kr is a critical repolarizing current in the heart and a target for inherited and acquired long-QT syndrome (LQTS). Biochemical and functional studies have demonstrated that I Kr channels are heteromers composed of both hERG 1a and 1b subunits, yet our current understanding of I Kr functional properties derives primarily from studies of homooligomers of the original hERG 1a isolate. Here, we examine currents produced by hERG 1a and 1a/1b channels expressed in HEK-293 cells at near-physiological temperatures. We find that heteromeric hERG 1a/1b currents are much larger than hERG 1a currents and conduct 80% more charge during an action potential. This surprising difference corresponds to a 2-fold increase in the apparent rates of activation and recovery from inactivation, thus reducing rectification and facilitating current rebound during repolarization. Kinetic modeling shows these gating differences account quantitatively for the differences in current amplitude between the 2 channel types. Drug sensitivity was also different. Compared to homomeric 1a channels, heteromeric 1a/1b channels were inhibited by E-4031 with a slower time course and a corresponding 4-fold shift in the IC 50 . The importance of hERG 1b in vivo is supported by the identification of a 1b-specific A8V missense mutation in 1/269 unrelated genotype-negative LQTS patients that was absent in 400 control alleles. Mutant 1bA8V expressed alone or with hERG 1a in HEK-293 cells dramatically reduced 1b protein levels. Thus, mutations specifically disrupting hERG 1b function are expected to reduce cardiac I Kr and enhance drug sensitivity, and represent a potential mechanism underlying inherited or acquired LQTS. (Circ Res. 2008;103:e81-e95.)Key Words: Kv11.1 Ⅲ KCNH2 Ⅲ ether-à-go-go Ⅲ arrhythmia Ⅲ potassium channels C ardiac I Kr is a potassium current contributing to ventricular repolarization in mammalian heart. 1,2 The molecular basis of cardiac I Kr was first elucidated when its unique biophysical and pharmacological properties were largely reproduced by heterologous expression of the hERG1 gene (human ether-à-go-go-related gene) (or KCNH2). 3,4 Together with the discovery of KCNH2 mutations as the pathogenic substrate in families with type 2 long-QT syndrome (LQTS), 5 these studies explained the underlying cause of disease as a loss of cardiac I Kr . They also identified hERG 1 channels as a molecular target for acquired LQTS, a much more prevalent form of the disease arising from I Kr block primarily by drugs intended for other therapeutic targets. 6 In either manifestation, LQTS is characterized by prolonged ventricular action potentials and a susceptibility to potentially life-threatening arrhythmias known as torsades de pointes (TdP). 7 Our understanding of how I Kr contributes to ventricular repolarization is based primarily on heterologous expression of the originally identified hERG 1a subunit. 3,4,8,9 Like other voltage-gated potassium channels, hERG 1a channels activate and inactivate on depolarization. However, b...

Background: Nothing is known regarding the anti-apoptotic effect of HO-1 on hCSCs. Results: HO-1 expression induced by CoPP enhances hCSC survival through activation of the ERK/NRF2 signaling pathway and cytokine release. Conclusion: CoPP is a cytoprotective agent that could improve the efficacy of CSC-based therapies for heart disease. Significance: Strategies to enhance donor cell survival would have enormous therapeutic implications for patients with ischemic heart disease.

The in vivo studies of myocardial infarct using c-kit+/Lin− cardiac stem cells (CSCs) are still in the early stage with margin or no beneficial effects for cardiac function. One of the potential reasons may be related to the absence of fully understanding the properties of these cells both in vitro and in vivo. In the present study, we aimed to systematically examine how CSCs adapted to in vitro cell processes and whether there is any cell contamination after long-term culture. Human CSCs were enzymatically isolated from the atrial appendages of patients. The fixed tissue sections, freshly isolated or cultured CSCs were then used for identification of c-kit+/Lin− cells, detection of cell contamination, or differentiation of cardiac lineages. By specific antibody staining, we demonstrated that tissue sections from atrial appendages contained less than 0.036% c-kit+/Lin− cells. For the first time, we noted that without magnetic activated cell sorting (MACS), the percentages of c-kit+/Lin− cells gradually increased up to ∼40% during continuously culture between passage 2 to 8, but could not exceed >80% unless c-kit MACS was carried out. The resulting c-kit+/Lin− cells were negative for CD34, CD45, CD133, and Lin markers, but positive for KDR and CD31 in few patients after c-kit MACS. Lin depletion seemed unnecessary for enrichment of c-kit+/Lin− cell population. Following induced differentiation, c-kit+/Lin− CSCs demonstrated strong differentiation towards cardiomyocytes but less towards smooth and endothelial cells. We concluded that by using an enzymatic dissociation method, a large number, or higher percentage, of relative pure human CSCs with stable expression of c-kit+ could be obtained from atrial appendage specimens within ∼4 weeks following c-kit MACS without Lin depletion. This simple but cost-effective approach can be used to obtain enough numbers of stably-expressed c-kit+/Lin− cells for clinical trials in repairing myocardial infarction.

Zika virus (ZIKV) is a mosquito-borne positive-sense single-stranded RNA virus in the family of Flaviviridae. Unlike other flaviviruses, ZIKV infection of pregnant women may result in birth defects in their newborns, such as microcephaly or vision problem. ZIKV is known to antagonize the interferon (IFN) production in infected cells. However, the exact mechanism of this interference is not fully understood. Here, we demonstrate that NS5 protein of ZIKV MR766 strain antagonizes IFN production through inhibiting the activation of TANK-binding kinase 1 (TBK1), which phosphorylates the transcription activator IFN regulatory factor 3 (IRF3). Mechanistically, NS5 interacts with the ubiquitin-like domain of TBK1 and results in less complex of TBK1 and TNF (tumor necrosis factor) receptor-associated factor 6 (TRAF6), leading to dampened TBK1 activation and IRF3 phosphorylation. Our study provides insights into the mechanism of ZIKV evasion of IFN-mediated innate immunity.