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© The Rockefeller University Press, 0022-1295/1998//583/ $5.00
Journal of General Physiology, Volume 111, Number 4, 1998

Article

Characterization of Ether-à-go-go Channels Present in Photoreceptors Reveals Similarity to IKx, a K+ Current in Rod Inner Segments

Stephan Frings*, Nicole Brüll*, Claudia Dzeja*, Albert Angele*, Volker Hagen{ddagger}, U. Benjamin Kaupp*, and Arnd Baumann*

From the * Institut für Biologische Informationsverarbeitung, Forschungszentrum Jülich, D-52425 Jülich, Germany; and {ddagger} Forschungsinstitut für Molekulare Pharmakologie, D-10315 Berlin, Germany

In this study, we describe two splice variants of an ether-à-go-go (EAG) K+ channel cloned from bovine retina: bEAG1 and bEAG2. The bEAG2 polypeptide contains an additional insertion of 27 amino acids in the extracellular linker between transmembrane segments S3 and S4. The heterologously expressed splice variants differ in their activation kinetics and are differently modulated by extracellular Mg2+. Cooperativity of modulation by Mg2+ suggests that each subunit of the putative tetrameric channel binds a Mg2+ ion. The channels are neither permeable to Ca2+ ions nor modulated by cyclic nucleotides. In situ hybridization localizes channel transcripts to photoreceptors and retinal ganglion cells. Comparison of EAG currents with IKx, a noninactivating K+ current in the inner segment of rod photoreceptors, reveals an intriguing similarity, suggesting that EAG polypeptides are involved in the formation of Kx channels.

Key Words: ether-à-go-go • retina • potassium channel • cyclic nucleotides

Address correspondence to Dr. A. Baumann, IBI, Forschungszentrum Jülich, 52425 Jülich, Germany. Fax: 49 2461/61-4216; E-mail: baumann{at}ibi.ibi.kfa-juelich.de


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