PRIMARY STRUCTURE AND FUNCTIONAL EXPRESSION OF A DROSOPHILA CYCLIC NUCLEOTIDE-GATED CHANNEL PRESENT IN EYES AND ANTENNAE

Cyclic nucleotide-gated (CNG) ion channels serve as downstream targets of signalling pathways in vertebrate photoreceptors and olfactory sen sory neurons. Whether CNG channels subserve similar functions in inver tebrate photoreception and olfaction is unknown. We have cloned genomi c DNA and cDNA encoding a cGMP-gated channel from Drosophila. The gene contains at least seven exons. Heterologous expression of cloned cDNA in both Xenopus oocytes and HEK 293 cells gives rise to functional io n channels. The Drosophila CNG channel is similar to 50-fold more sens itive to cGMP than to cAMP. The voltage dependence of blockage by diva lent cations is different compared with the CNG channel of rod photore ceptors, and the Ca2+ permeability is much larger. The channel mRNA is expressed in antennae and the visual system of Drosophila. It is prop osed that CNG channels are involved in transduction cascades of both i nvertebrate photoreceptors and olfactory sensillae.