ETHER-A-GO-GO ENCODES A VOLTAGE-GATED CHANNEL PERMEABLE TO K+ AND CA2+ AND MODULATED BY CAMP

THE Drosophila ether-a-go-go (eag) mutant is responsible for altered p otassium currents in excitable tissue1. These mutants exhibit spontane ous, repetitive firing of action potentials in the motor axons of larv al neuromuscular junctions2. The eag gene encodes a polypeptide3 that shares sequence similarities with several different ionic channel prot eins, including voltage-gated potassium channels-, an inward rectifier 4,5 as well as cyclic-nucleotide-gated channels6. These formal similar ities in the derived primary sequences indicate that eag polypeptides might express a new type of ion channel. Here we report the expression by eag RNA in Xenopus oocytes of such a channel which incorporates pr operties of both voltage- and ligand-gated channels. The permeability of these eag channels to potassium and calcium is dependent on voltage and cyclic AMP. The ability to mediate potassium-outward and calcium- inward currents endows this channel with properties likely to be impor tant in the modulation of synaptic efficiency in both central and peri pheral nervous systems.