Abstract
Proarrhythmic drugs induce long QT syndrome more frequently in women than men. The present study was designed to determine whether androgens regulate the function and expression of the human ether-á-go-go-related gene (HERG) encoded K+ channel, which is largely responsible for determining the QT interval. In a concentration-dependent manner (10(-9) to 10(-6) M for 24 h), 5alpha-dihydrotestosterone (5alpha-DHT) increased HERG protein abundance in HEK293 cells stably expressing HERG in the presence of coexpressed cardiac androgen receptor (AR) variant [N-terminal truncated isoform of AR (AR45)]. The elevation of HERG protein was seen in endoplasmic reticulum, Golgi, and plasma membrane without clear preferential colocalization. Coexpression of the more common form of the AR did not confer 5alpha-DHT augmentation of HERG protein. Proteasome inhibitors, N-acetyl-L-leucyl-L-leucyl-L-norleucinal and MG132 prevented the 5alpha-DHT- dependent enhancement of HERG, as did the lysosome inhibitor, bafilomycin A1. Consistently, the cycloheximide-based protein chase study showed that 5alpha-DHT prolonged HERG protein half-life. 5alpha-DHT/AR45 signaling induced phosphorylation of ERK1/2. Blockade of ERK1/2 with PD98059 and U0126 prevented the effect of androgen on HERG protein abundance. Functional studies showed that 5alpha-DHT treatment for 24 h increased HERG K+ current density in Chinese hamster ovary cells cotransfected with cDNAs of AR45 and HERG channels. Moreover, 5alpha-DHT also increased ether-á-go-go-related gene-encoded K+ channel protein abundance in isolated rabbit cardiac myocytes. In conclusion, these data provide evidence that stimulation of AR45 receptors by androgens up-regulates HERG K+ channel abundance and activity mainly through stabilizing HERG protein in an ERK1/2 dependent mechanism, and suggest a mechanism to explain the sex difference in the long QT syndrome.