Department of Physiology and Developmental Biology, Brigham Young University, Provo, UT 84602, USA.
Respir Res. 2010 Dec 9;11(1):175. doi: 10.1186/1465-9921-11-175.
Nicotinic acetylcholine receptors (nAChRs) are ligand-gated ion channels comprised of five similar subunits that influence signal transduction and cell turnover. α5 is a structural subunit detected in many non-neuronal tissues; however, its function during pulmonary development is unknown.
α5 was assessed by immunohistochemistry and RT-PCR in mouse lungs from embryonic day (E)13.5 to post-natal day (PN)20. From E13.5 to E18.5, α5 expression was primarily observed in primitive airway epithelial cells while mesenchymal expression was faint and sporadic. α5 expression was detected throughout the proximal lung at PN1 and extensively expressed in the peripheral lung at PN4, an early stage of murine alveologenesis. An interesting shift occurred wherein α5 expression was almost undetectable in the proximal lung from PN4-PN10, but significant localization was again observed at PN20. Transcriptional control of α5 was determined by assessing the activity of reporters containing 2.0-kb and 850-bp of the mouse α5 promoter. Because perinatal expression of α5 was abundant in bronchiolar and alveolar epithelium, we assessed transcriptional control of α5 in Beas2B cells, a human bronchiolar epithelial cell line, and A-549 cells, an alveolar type II cell-like human epithelial cell line. Thyroid Transcription Factor-1 (TTF-1), a key transcription regulator of pulmonary morphogenesis, significantly increased α5 transcription by acting on both the 2.0-kb and 850-bp α5 promoters. Site-directed mutagenesis revealed that TTF-1 activated α5 transcription by binding specific TTF-1 response elements. Exogenous TTF-1 also significantly induced α5 transcription.
These data demonstrate that α5 is specifically controlled in a temporal and spatial manner during pulmonary morphogenesis. Ongoing research may demonstrate that precise regulation of α5 is important during normal organogenesis and misexpression correlates with tobacco related lung disease.
烟碱型乙酰胆碱受体（nAChRs）是由五个相似亚基组成的配体门控离子通道，影响信号转导和细胞更替。α5 是在许多非神经元组织中检测到的结构亚基；然而，其在肺发育过程中的功能尚不清楚。
通过免疫组织化学和 RT-PCR 评估了从胚胎第 13.5 天（E）到出生后第 20 天（PN）的小鼠肺中的α5。从 E13.5 到 E18.5，α5 表达主要在原始气道上皮细胞中观察到，而间充质表达微弱且分散。α5 表达在 PN1 时可在近端肺中检测到，并在 PN4 时在周围肺中广泛表达，这是小鼠肺泡发生的早期阶段。有趣的转变是，α5 表达在 PN4-PN10 的近端肺中几乎无法检测到，但在 PN20 时又再次观察到显著的定位。通过评估包含小鼠α5 启动子 2.0-kb 和 850-bp 的报告基因的活性来确定α5 的转录控制。由于α5 在细支气管和肺泡上皮中的围产期表达丰富，我们评估了甲状腺转录因子-1（TTF-1），一种肺形态发生的关键转录调节因子，在 Beas2B 细胞（一种人细支气管上皮细胞系）和 A-549 细胞（一种肺泡 II 型细胞样人上皮细胞系）中对α5 转录的转录控制。显著增加了 2.0-kb 和 850-bp α5 启动子的α5 转录。位点定向突变揭示 TTF-1 通过结合特定的 TTF-1 反应元件激活α5 转录。外源性 TTF-1 也显著诱导了α5 转录。
这些数据表明，α5 在肺形态发生过程中以时空方式受到特异性控制。正在进行的研究可能表明，α5 的精确调节在正常器官发生过程中很重要，并且错误表达与烟草相关的肺部疾病相关。
