Molecular characterization, functional expression, and developmental profile of an ether à-go-go K+ channel in the tobacco hornworm Manduca sexta.
A very large number of evolutionarily conserved potassium channels have been identified but very little is known about their function or modulation in vivo. Metamorphosis of the tobacco hornworm, Manduca sexta, is a compelling model system for such studies because it permits analysis to be conducted at the level of identified neurons whose roles in simple behaviors and endocrine regulation are known. We present here the characterization of the first ion channel to be cloned from this animal. Partial genomic sequence for Manduca sexta ether à-go-go (Mseag) and a cDNA clone encoding the Mseag open reading frame were obtained. Genomic Southern analysis indicates that Manduca contains a single member of the eag subfamily per haploid genome. When expressed in Xenopus oocytes, MsEag channels conduct a voltage-dependent, K+ selective outward current with an inactivating component that closely resembles the Drosophila eag current. Mseag transcripts were restricted to the nervous system, adult antenna, and one set of larval skeletal muscles. Steroid hormonal regulation of Mseag expression is suggested by the temporal correlation of developmental changes in transcript expression with the changing steroid titers that promote metamorphosis. These results provide the foundation for functional and modulatory studies of the Eag family of K+ channels in Manduca, which will complement the genetic analysis in Drosophila.
Keyser
Matthew R
MR
Department of Biological Sciences, P.O. Box 413, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin 53201, USA.
Anson
Blake D
BD
Titus
Steven A
SA
Ganetzky
Barry
B
Witten
Jane L
JL
D000595:Amino Acid Sequence; D000818:Animals; D015139:Blotting, Southern; D004330:Drosophila; D000072237:ERG1 Potassium Channel; D004553:Electric Conductivity; D004594:Electrophysiology; D051638:Ether-A-Go-Go Potassium Channels; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects / Q000502:physiology; D015723:Gene Library; D015698:Genomic Library; D007814:Larva; D018402:Manduca; D008675:Metamorphosis, Biological; D018482:Muscle, Skeletal / Q000254:growth & development / Q000378:metabolism; D009420:Nervous System / Q000254:growth & development / Q000378:metabolism; D009865:Oocytes / Q000502:physiology; D011188:Potassium / Q000378:metabolism*; D015221:Potassium Channels / Q000096:biosynthesis / Q000235:genetics* / Q000502:physiology; D024642:Potassium Channels, Voltage-Gated; D012333:RNA, Messenger / Q000032:analysis; D011994:Recombinant Proteins / Q000096:biosynthesis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D020539:Sequence Analysis, Protein; D013045:Species Specificity; D013250:Steroid Hydroxylases / Q000494:pharmacology; D014982:Xenopus laevis
D000072237:ERG1 Potassium Channel; D051638:Ether-A-Go-Go Potassium Channels; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; D012333:RNA, Messenger; D011994:Recombinant Proteins; D013250:Steroid Hydroxylases; C050128:steroid (23R)-hydroxylase; D011188:Potassium