Pugh P C, Corriveau R A, Conroy W G, Berg D K
Department of Biology, University of California, San Diego, La Jolla 92093-0357, USA.
Mol Pharmacol. 1995 Apr;47(4):717-25.
Neuronal acetylcholine receptors (AChRs) that bind alpha-bungarotoxin (alpha Bgt) (alpha Bgt-AChRs) have previously been found to contain at least one of the alpha 7-alpha 9 gene products. No other gene products of the 11 neuronal AChR genes cloned to date from rat and/or chick have been identified in such receptors. Chick ciliary ganglia have about 20 fmol of alpha Bgt-AChRs that contain alpha 7 subunits and 5 fmol of synaptic-type AChRs that bind the monoclonal antibody (mAb) 35 and collectively contain alpha 3, beta 4, alpha 5, and, to a lesser extent, beta 2 subunits. Using a sensitive solid-phase immunoprecipitation assay, we show here that ciliary ganglia have about 1 fmol of novel putative AChRs that bind both alpha Bgt and mAb 35 but appear to lack all of the known neuronal AChR gene products in ciliary ganglia, including alpha 3, alpha 5, alpha 7, beta 2, and beta 4. The putative receptors are also unlikely to contain either alpha 8 or alpha 9 gene products, because of the known expression patterns of these gene products. Nonetheless, the component sediments at 10 S, as expected for neuronal AChRs, and has a nicotinic pharmacology similar but not identical to that of alpha 7-containing alpha Bgt-AChRs. The AChR alpha 1 gene product expressed in muscle is known to bind both alpha Bgt and mAb 35, and we show here that ciliary ganglia contain small amounts of alpha 1 transcript. The putative ciliary ganglion AChR defined by joint alpha Bgt and mAb 35 binding, however, does not appear to contain alpha 1 subunits. A similar component binding both mAb 35 and alpha Bgt can be detected in sympathetic ganglia and dorsal root ganglia but not in brain, spinal cord, or retina. The developmental time course of the component in ciliary ganglia is comparable to that of the alpha 7-containing alpha Bgt-AChRs. If the component is a functional AChR on ciliary ganglion neurons, as seems likely, it would represent the fourth AChR subtype produced by this population of cells. Our inability to identify subunits comprising the putative receptors raises the possibility that additional AChR genes remain to be cloned.
此前发现，能结合α-银环蛇毒素（αBgt）的神经元乙酰胆碱受体（AChRs）（αBgt-AChRs）至少含有α7-α9基因产物中的一种。在迄今从大鼠和/或鸡克隆的11种神经元AChR基因的其他基因产物中，尚未在这类受体中鉴定到。鸡睫状神经节含有约20飞摩尔能结合αBgt且含有α7亚基的AChRs，以及5飞摩尔能结合单克隆抗体（mAb）35的突触型AChRs，后者共同含有α3、β4、α5亚基，以及含量较少的β2亚基。利用一种灵敏的固相免疫沉淀测定法，我们在此表明，睫状神经节含有约1飞摩尔新型的假定AChRs，其能结合αBgt和mAb 35，但似乎缺乏睫状神经节中所有已知的神经元AChR基因产物，包括α3、α5、α7、β2和β4。由于这些基因产物已知的表达模式，这种假定的受体也不太可能含有α8或α9基因产物。尽管如此，该组分在10 S处沉降，这与神经元AChRs预期的情况相符，并且具有与含α7的αBgt-AChRs相似但不完全相同的烟碱药理学特性。已知在肌肉中表达的AChRα1基因产物能结合αBgt和mAb 35，我们在此表明，睫状神经节含有少量的α1转录本。然而，由αBgt和mAb 35共同结合所定义的假定睫状神经节AChR似乎不含有α1亚基。在交感神经节和背根神经节中可检测到一种类似的能结合mAb 35和αBgt的组分，但在脑、脊髓或视网膜中则检测不到。睫状神经节中该组分的发育时间进程与含α7的αBgt-AChRs的相似。如果该组分是睫状神经节神经元上的一种功能性AChR（似乎很有可能），那么它将代表这群细胞产生的第四种AChR亚型。我们无法鉴定构成假定受体的亚基，这增加了仍有待克隆其他AChR基因的可能性。
