Molecular characterization, functional expression, and developmental profile of an ether à‐go‐go K+ channel in the tobacco hornworm Manduca sexta

Abstract

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.

Pharmacological Investigation of Protein Kinase C- and cGMP-Dependent Ion Channels in Cultured Olfactory Receptor Neurons of the Hawkmoth Manduca sexta

“…Because it was blocked by TEA and showed small, slowly activating outward and no inward currents, it seems to be a delayed rectifier potassium channel with slow kinetics. Whether this channel is encoded by the ether a-go-go (eag) potassium channel gene cloned from M. sexta ( Keyser et al 2003 ) remains to be examined.…”

Intracellular linkers are involved in Mg2+-dependent modulation of the Eag potassium channel

“…Other than affecting activation kinetics, the G297E and/or R363E mutations also led to changes in Eag channel inactivation, which is characteristic of Eag channels cloned from Drosophila and some other invertebrate species, but has not been observed in their mammalian homologs. 2,26,29,30 In the presence of 4 mM Mg 2+ , however, macroscopic currents of wild-type Eag channels did not exhibit inactivation at depolarization potentials up to +70 mV (Fig. 1A).…”

Peripheral regulation by ecdysteroids of olfactory responsiveness in male Egyptian cotton leaf worms, Spodoptera littoralis

“…Testosterone modulates an Ether à-go-go K þ channel in the repolarization phase. In M. sexta, steroid regulation has also been suggested for Ether à-go-go K þ channel expression (Keyser et al, 2003). In addition, depending on endogenous circadian rhythms of the moth's physiological state, Stengl (2010) described in a review the modulation role of another hormone, octopamine, on the second messenger levels in sensory neuron and the consequence on the pheromone detection and response kinetics of ORNs.…”