Human ether-a-gogo related gene (HERG) K+ channels as pharmacological targets: present and future implications.

Electrophysiological and molecular biology techniques have widely expanded our knowledge of the diverse functions where K+ channels are implicated as potential and proven pharmacological targets. The aim of the present commentary is to review the recent progress in the understanding of the functional role of the K+ channels encoded by the human ether-a-gogo related gene (HERG), with particular emphasis on their direct pharmacological modulation by drugs, or on their regulation by pharmacologically relevant phenomena. About 3 years have passed since the cloning, expression, and description of the pathophysiological role of HERG K+ channels in human cardiac repolarization. Despite this short lapse of time, these K+ channels have already gained considerable attention as pharmacological targets. In fact, interference with HERG K+ channels seems to be the main mechanism explaining both the therapeutic actions of the class III antiarrhythmics and the potential cardiotoxicity of second-generation H1 receptor antagonists such as terfenadine and astemizole, as well as of psychotropic drugs such as some antidepressants and neuroleptics. It seems possible to anticipate that the main tasks for future investigation will be, on the one side, the better understanding of the intimate mechanism of action of HERG K+ channel-blocking drugs in order to elucidate the conditions regulating the delicate balance between antiarrhythmic and proarrhythmic potential and, on the other, to unravel the pathophysiological role of this K+ channel in the function of the brain and of other excitable tissues.