Neuronal nicotinic acetylcholine receptors on bovine chromaffin cells: cloning, expression, and genomic organization of receptor subunits.
Neuronal nicotinic acetylcholine receptors from bovine adrenomedullary chromaffin cells play a primary role in triggering catecholamine secretion. In the present study, their constituent subunits were characterized. In addition to the alpha 3 subunit, which we have previously cloned, the presence of alpha 5 and beta 4 but not of beta 2 subunits was detected by reverse transcription-PCR analysis of mRNA from adrenal medulla. In situ hybridization indicated that alpha 3, alpha 5, and beta 4 subunits are coexpressed in all chromaffin cells. The primary structure of alpha 5 and beta 4 subunits was determined and functional receptors were obtained upon coinjection of subunit cRNAs into Xenopus oocytes. In contrast to other beta 4-containing nicotinic receptors, the ones formed by the bovine beta 4 subunit are insensitive to the agonist cytisine. Finally, we characterized the intergenic region of alpha 3 and alpha 5 subunits, which together with the beta 4 subunit, form a gene cluster in rats and chickens. RNase assays and the existence of overlapping cDNAs indicate that, in the bovine genome, the alpha 3 and alpha 5 genes overlap at their 3' ends. This fact is probably due to inefficient transcription termination, as a result of weak polyadenylation signals.
Campos-Caro
A
A
Department of Neurochemistry, University of Alicante, Spain.
Smillie
F I
FI
Domínguez del Toro
E
E
Rovira
J C
JC
Vicente-Agulló
F
F
Chapuli
J
J
Juíz
J M
JM
Sala
S
S
Sala
F
F
Ballesta
J J
JJ
Criado
M
M
D000818:Animals; D001483:Base Sequence; D002417:Cattle; D019439:Chromaffin Cells / Q000737:chemistry*; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000235:genetics; D005260:Female; D005786:Gene Expression Regulation / Q000502:physiology; D015723:Gene Library; D016678:Genome; D007438:Introns / Q000235:genetics; D008969:Molecular Sequence Data; D009474:Neurons / Q000737:chemistry; D009865:Oocytes / Q000502:physiology; D012333:RNA, Messenger / Q000032:analysis; D011978:Receptors, Nicotinic / Q000737:chemistry / Q000235:genetics*; D017386:Sequence Homology, Amino Acid; D014158:Transcription, Genetic / Q000502:physiology; D014981:Xenopus
D018076:DNA, Complementary; D012333:RNA, Messenger; D011978:Receptors, Nicotinic