© 2002 by European Society of Cardiology
Copyright © 2002, European Society of Cardiology
Cardiac-enriched LIM domain protein fhl2 is required to generate IKs in a heterologous system
aDepartment of Pharmacology, 561A PRB, Division of Clinical Pharmacology, Vanderbilt University School of Medicine, 532C Robinson Research Building, 23rd Avenue South at Pierce Avenue, Nashville, TN 37232-6602, USA
bDepartment of Anesthesiology, Vanderbilt University School of Medicine, Nashville, TN 37232-6602, USA
cDepartment of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN 37232-6602, USA
dDepartment of Medicine, Vanderbilt University School of Medicine, Nashville, TN 37232-6602, USA
* Corresponding author. Tel.: +1-615-936-2586; fax: +1-615-322-4707 sabina.kupershmidt{at}vanderbilt.edu
Objective: Co-expression of the KvLQT1 and minK potassium channel subunits is required to recapitulate IKs, the slow component of the cardiac delayed rectifier current, and mutations in either gene cause the congenital Long QT syndrome. It is becoming increasingly well-recognized that multiprotein channel complexes containing proteins capable of modulating channel function assemble at the plasma membrane. Thus, the aim of our study was to identify proteins involved in IKs modulation. Methods and results: Using a yeast-two-hybrid screen with the intracytoplasmic C-terminus of minK as bait, we identified the cardiac-enriched four-and-a-half LIM domain-containing protein (fhl2) as a potential minK partner. We show interaction between the two proteins in GST pulldown assays and demonstrate overlapping subcellular localization using immunocytochemistry of transfected cells supporting a potential interaction. At the functional level, expression of KvLQT1and minK in HEK cells, which lack endogenous fhl2 protein, generated IKs only when fhl2 was co-expressed. By contrast, in CHO-K1 cells, which express fhl2 endogenously, IKs was suppressed by anti-fhl2 antisense which did not affect the currents generated by KvLQT1alone. Conclusion: These data indicate that at least in heterologous cells, the generation of IKs requires fhl2 as an additional protein component.
KEYWORDS Arrhythmia (mechanisms); Ion channels; K-channel; Long QT syndrome; Ventricular arrhythmias
1 Present address: Department of Pharmacology, George Washington University, Washington, DC 20037, USA.
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