Abstract 19811: Interaction of hERG and Tara, a Potential Target for Long QT Syndrome
The human Ether-a-go-go Related Gene (hERG , or KCNH2 ) encodes the alpha subunit of cardiac IKr channels critical for ventricular repolarization. Long QT syndrome (LQTS) can arise from inherited mutations in hERG or by block of cardiac IKr by a wide range of drugs largely intended for other therapeutic targets. To identify novel proteins involved in hERG/IKr channel regulation, we screened a human heart library using a yeast two-hybrid assay and discovered a direct interaction between a C-terminal hERG protein fragment and the protein Trio associated repeat on actin (Tara). Tara is ubiquitously expressed and has been shown to directly bind Trio and F-actin, and to stabilize F-actin. Using co-immunoprecipitation, we confirmed association of hERG and Tara in a heterologous system and in canine ventricle. Two-electrode voltage clamp recordings in Xenopus oocytes revealed that Tara suppressed currents expressed from WT hERG by approximately 45% but had no significant effect on C-truncated hERG lacking the Tara binding region. This decrease in current was not attributable to a decrease in hERG protein synthesis or maturation as determined by western blot analysis. Five LQTS referral patients who were genotype-negative for known LQTS genes were found to harbor four Tara mutations that were absent in 200 reference alleles from healthy control patients, suggesting a possible role for Tara in LQTS pathogenesis. Functional analyses are under way to determine effects of Tara mutants on hERG current and thus infer the physiological role of hERG-Tara interactions.
- © 2010 by American Heart Association, Inc.