Identification of a cyclic nucleotide- and voltage-activated ion channel from insect antennae

From an antennal cDNA library of Heliothis virescens a clone has been isola ted encoding a polypeptide of 678 amino acids. Data base comparisons and pr imary structure analysis of the deduced protein sequence (HvCNG) indicated significant homology to cyclic nucleotide and voltage-activated ion channel s including six putative membrane spanning domains, a putative cyclic nucle otide binding site, a pore region and a voltage-sensor motif. Heterologous expression of the cloned cDNA in Sf9 cells resulted in a polypeptide of the predicted molecular mass. Patch clamp analysis allowed to record the activ ity of the identified HvCNG channels; they were activated by cAMP but also by hyperpolarization. The channel displayed in potassium solution a conduct ance of 30 pS; the ion selectivity was calculated as P-K/P-Na approximate t o 3. Northern blot analysis revealed that the channel is highly expressed i n the antennae; weaker signal were detected in heads and legs. In situ hybr idization of tissue sections through the antennae showed a spatial distribu tion of reactive cells; they are located beneath sensillar hairs. Thus, a n ovel channel type has been identified which may play an important role in a ntennal cells. (C) 1999 Elsevier Science Ltd. All rights reserved.