This Article Full Text Full Text (PDF) All Versions of this Article: 2/5/540    most recent CIRCEP.109.872309v1 Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Permissions Google Scholar Articles by Vega, A. L. Articles by Makielski, J. C. PubMed PubMed Citation Articles by Vega, A. L. Articles by Makielski, J. C. Related Collections Clinical genetics Arrythmias-basic studies Functional genomics Ion channels/membrane transport Arrhythmias, clinical electrophysiology, drugs

Original Articles

Protein Kinase A-Dependent Biophysical Phenotype for V227F-KCNJ2 Mutation in Catecholaminergic Polymorphic Ventricular Tachycardia

Amanda L. Vega, PhD; David J. Tester, BS; Michael J. Ackerman, MD, PhD and Jonathan C. Makielski, MD

From the Departments of Medicine (Cardiovascular Medicine) and Physiology (J.C.M.), University of Wisconsin (A.L.V.), Madison, Wis; the Departments of Medicine, Pediatrics, and Molecular Pharmacology and Experimental Therapeutics/Divisions of Cardiovascular Diseases and Pediatric Cardiology (D.J.T., M.J.A.), Mayo Clinic, Rochester, Minn; and the Department of Physiology and Biophysics (A.L.V.), University of Washington, Seattle, Wash. Current address for Dr Vega is the Department of Physiology and Biophysics, University of Washington, Seattle, Wash.

Correspondence to Jonathan C. Makielski, MD, University of Wisconsin Hospital and Clinics, Division of Cardiovascular Medicine, H6/362 MC 3248, 600 Highland Ave, Madison, WI 53792. E-mail jcm{at}medicine.wisc.edu

Received April 10, 2009; accepted July 30, 2009.

Background— KCNJ2 encodes Kir2.1, a pore-forming subunit of the cardiac inward rectifier current, I_K1. KCNJ2 mutations are associated with Andersen-Tawil syndrome and catecholaminergic polymorphic ventricular tachycardia. The aim of this study was to characterize the biophysical and cellular phenotype of a KCNJ2 missense mutation, V227F, found in a patient with catecholaminergic polymorphic ventricular tachycardia.

Methods and Results— Kir2.1-wild-type (WT) and V227F channels were expressed individually and together in Cos-1 cells to measure I_K1 by voltage clamp. Unlike typical Andersen-Tawil syndrome-associated KCNJ2 mutations, which show dominant negative loss of function, Kir2.1WT+V227F coexpression yielded I_K1 indistinguishable from Kir2.1-WT under basal conditions. To simulate catecholamine activity, a protein kinase A (PKA)-stimulating cocktail composed of forskolin and 3-isobutyl-1-methylxanthine was used to increase PKA activity. This PKA-simulated catecholaminergic stimulation caused marked reduction of outward I_K1 compared with Kir2.1-WT. PKA-induced reduction in I_K1 was eliminated by mutating the phosphorylation site at serine 425 (S425N).

Conclusions— Heteromeric Kir2.1-V227F and WT channels showed an unusual latent loss of function biophysical phenotype that depended on PKA-dependent Kir2.1 phosphorylation. This biophysical phenotype, distinct from typical Andersen-Tawil syndrome mutations, suggests a specific mechanism for PKA-dependent I_K1 dysfunction for this KCNJ2 mutation, which correlates with adrenergic conditions underlying the clinical arrhythmia.

Key Words: K-channel • arrhythmia (mechanisms) • long QT syndrome • Andersen-Tawil syndrome • catecholaminergic polymorphic ventricular tachycardia

---

 

CLINICAL PERSPECTIVE

Guest Editor for this article was Douglas P. Zipes, MD.