D alpha3, a new functional alpha subunit of nicotinic acetylcholine receptors from Drosophila

• Published in: Journal of neurochemistry Vol. 71; no. 2; pp. 853 - 862
• Main Authors: Schulz, R, Sawruk, E, Mülhardt, C, Bertrand, S, Baumann, A, Phannavong, B, Betz, H, Bertrand, D, Gundelfinger, E D, Schmitt, B
• Format: Journal Article
• Language: English
• Published: England 01-08-1998
• Subjects: Amino Acid Sequence; Animals; Base Sequence; Chickens; Chromosome Mapping; Cloning, Molecular; DNA, Complementary; Drosophila - genetics; Drosophila Proteins; Electrophysiology; Evolution, Molecular; Gene Expression; Molecular Sequence Data; Oocytes - physiology; Receptors, Nicotinic - chemistry; Receptors, Nicotinic - genetics; RNA, Messenger - analysis; Transcription, Genetic; Xenopus
• ISSN: 0022-3042

Nicotinic acetylcholine (ACh) receptors (nAChRs) are important excitatory neurotransmitter receptors in the insect CNS. We have isolated and characterized the gene and the cDNA of a new nAChR subunit from Drosophila. The predicted mature nAChR protein consists of 773 amino acid residues and has the structural features of an ACh-binding alpha subunit. It was therefore named D alpha3, for Drosophila alpha-subunit 3. The d alpha3 gene maps to the X chromosome at position 7E. The properties of the D alpha3 protein were assessed by expression in Xenopus oocytes. D alpha3 did not form functional receptors on its own or in combination with any Drosophila beta-type nAChR subunit. Nondesensitizing ACh-evoked inward currents were observed when D alpha3 was coexpressed with the chick beta2 subunit. Half-maximal responses were at approximately 0.15 microM ACh with a Hill coefficient of approximately 1.5. The snake venom component alpha-bungarotoxin (100 nM) efficiently but reversibly blocked D alpha3/beta2 receptors, suggesting that D alpha3 may be a component of one of the previously described two classes of toxin binding sites in the Drosophila CNS.