Whiting P J, Schoepfer R, Conroy W G, Gore M J, Keyser K T, Shimasaki S, Esch F, Lindstrom J M
Salk Institute for Biological Studies, San Diego, CA 92138.
Brain Res Mol Brain Res. 1991 Apr;10(1):61-70. doi: 10.1016/0169-328x(91)90057-5.
Neuronal nicotinic acetylcholine receptors (AChRs) are composed of two types of subunits: ACh-binding (termed alpha 2, alpha 3, alpha 4 ...) and structural (termed beta 2, beta 3, beta 4 ...). AChR subtypes composed of combinations of subunits of these two types encoded by several related genes are expressed in different parts of the nervous system, where they presumably serve different functional roles. Here we identify the ACh-binding subunit of the most prominent chicken brain AChR subtype by N-terminal amino acid sequence and show that it corresponds to the alpha 4 gene. Previously we identified the structural subunit for this AChR subtype from chicken brain as beta 2 by N-terminal amino acid sequence. Thus, this identifies both genes which encode subunits of the major nicotinic AChR subtype in avian brains. By immunoprecipitation, immunohistochemistry, and northern blot analysis we show that alpha 3 (or a very closely related sequence) is expressed at low levels in the brain and relatively high levels in the retina, while alpha 4 is expressed at high levels in the brain and lower levels in the retina. This differential expression indicates that alpha 3-containing 'ganglionic-type' AChRs may be an important AChR subtype in avian retina.
神经元烟碱型乙酰胆碱受体（AChRs）由两种亚基组成：乙酰胆碱结合亚基（称为α2、α3、α4……）和结构亚基（称为β2、β3、β4……）。由几个相关基因编码的这两种亚基组合而成的AChR亚型在神经系统的不同部位表达，推测它们在其中发挥不同的功能作用。在这里，我们通过N端氨基酸序列鉴定了鸡脑中最主要的AChR亚型的乙酰胆碱结合亚基，并表明它对应于α4基因。此前我们通过N端氨基酸序列鉴定出鸡脑该AChR亚型的结构亚基为β2。因此，这确定了编码禽类脑中主要烟碱型AChR亚型亚基的两个基因。通过免疫沉淀、免疫组织化学和Northern印迹分析，我们发现α3（或一个非常密切相关的序列）在脑中低水平表达，在视网膜中相对高水平表达，而α4在脑中高水平表达，在视网膜中低水平表达。这种差异表达表明含α3的“神经节型”AChRs可能是禽类视网膜中一种重要的AChR亚型。
