Hermsen B, Stetzer E, Thees R, Heiermann R, Schrattenholz A, Ebbinghaus U, Kretschmer A, Methfessel C, Reinhardt S, Maelicke A
Laboratory of Molecular Neurobiology, Institute of Physiological Chemistry and Pathobiochemistry, 6 Duesbergweg, Johannes-Gutenberg University Medical School, 55099 Mainz, Germany.
J Biol Chem. 1998 Jul 17;273(29):18394-404. doi: 10.1074/jbc.273.29.18394.
We have identified five cDNA clones that encode nicotinic acetylcholine receptor (nAChR) subunits expressed in the nervous system of the locust Locusta migratoria. Four of the subunits are ligand-binding alpha subunits, and the other is a structural beta subunit. The existence of at least one more nAChR gene, probably encoding a beta subunit, is indicated. Based on Northern analysis and in situ hybridization, the five subunit genes are expressed. localpha1, localpha3, and locbeta1 are the most abundant subunits and are expressed in similar areas of the head ganglia and retina of the adult locust. Because Loc<alpha3 binds alpha-bungarotoxin with high affinity, it may form a homomeric nAChR subtype such as the mammalian alpha7 nAChR. Localpha1 and Locbeta1 may then form the predominant heteromeric nAChR in the locust brain. localpha4 is mainly expressed in optic lobe ganglionic cells and localpha2 in peripherally located somata of mushroom body neurons. localpha3 mRNA was additionally detected in cells interspersed in the somatogastric epithelium of the locust embryo, suggesting that this isoform may also be involved in functions other than neuronal excitability. Transcription of all nAChR subunit genes begins approximately 3 days before hatching and continues throughout adult life. Electrophysiological recordings from head ganglionic neurons also indicate the existence of more than one functionally distinct nAChR subtype. Our results suggest the existence of several nAChR subtypes, at least some of them heteromeric, in this insect species.
我们已鉴定出五个编码烟碱型乙酰胆碱受体（nAChR）亚基的cDNA克隆，这些亚基在飞蝗Locusta migratoria的神经系统中表达。其中四个亚基是结合配体的α亚基，另一个是结构β亚基。这表明至少还存在一个可能编码β亚基的nAChR基因。基于Northern分析和原位杂交，这五个亚基基因均有表达。Locα1、Locα3和Locβ1是最丰富的亚基，在成年飞蝗的头部神经节和视网膜的相似区域表达。由于Locα3与α-银环蛇毒素具有高亲和力，它可能形成同聚体nAChR亚型，如哺乳动物的α7 nAChR。然后Locα1和Locβ1可能构成飞蝗脑中主要的异聚体nAChR。Locα4主要在视叶神经节细胞中表达，而Locα2在蘑菇体神经元外周的体细胞中表达。此外，在飞蝗胚胎体壁上皮中散布的细胞中检测到Locα3 mRNA，这表明该亚型可能还参与除神经元兴奋性之外的其他功能。所有nAChR亚基基因的转录大约在孵化前3天开始，并在成年期持续进行。对头部神经节神经元的电生理记录也表明存在不止一种功能不同的nAChR亚型。我们的结果表明，在这种昆虫物种中存在几种nAChR亚型，其中至少一些是异聚体。
