Campos-Caro A, Smillie F I, Domínguez del Toro E, Rovira J C, Vicente-Agulló F, Chapuli J, Juíz J M, Sala S, Sala F, Ballesta J J, Criado M
Department of Neurochemistry, University of Alicante, Spain.
J Neurochem. 1997 Feb;68(2):488-97. doi: 10.1046/j.1471-4159.1997.68020488.x.
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.
来自牛肾上腺髓质嗜铬细胞的神经元烟碱型乙酰胆碱受体在触发儿茶酚胺分泌中起主要作用。在本研究中，对其组成亚基进行了表征。除了我们之前克隆的α3亚基外，通过对肾上腺髓质mRNA进行逆转录-聚合酶链反应分析，检测到α5和β4亚基的存在，但未检测到β2亚基。原位杂交表明，α3、α5和β4亚基在所有嗜铬细胞中共同表达。确定了α5和β4亚基的一级结构，并将亚基cRNA共注射到非洲爪蟾卵母细胞中获得了功能性受体。与其他含β4的烟碱型受体不同，由牛β4亚基形成的受体对激动剂金雀花碱不敏感。最后，我们对α3和α5亚基的基因间隔区进行了表征，α3和α5亚基与β4亚基一起在大鼠和鸡中形成一个基因簇。核糖核酸酶分析和重叠cDNA的存在表明，在牛基因组中，α3和α5基因在其3'端重叠。这一事实可能是由于聚腺苷酸化信号较弱导致转录终止效率低下所致。
