TTF-1 regulates α₅nicotinic acetylcholine receptor (nAChR) subunits in proximal and distal lung epithelium

• Main Authors: Willnauer Charles P, Allison Camille H, Reynolds Paul R
• Format: Article
• Language: English
• Published: BMC 2010-12-01
• Series: Respiratory Research
• Online Access: http://respiratory-research.com/content/11/1/175

<p>Abstract</p> <p>Background</p> <p>Nicotinic acetylcholine receptors (nAChRs) are ligand-gated ion channels comprised of five similar subunits that influence signal transduction and cell turnover. α₅is a structural subunit detected in many non-neuronal tissues; however, its function during pulmonary development is unknown.</p> <p>Results</p> <p>α₅was 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, α₅expression was primarily observed in primitive airway epithelial cells while mesenchymal expression was faint and sporadic. α₅expression 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 α₅expression was almost undetectable in the proximal lung from PN4-PN10, but significant localization was again observed at PN20. Transcriptional control of α₅was determined by assessing the activity of reporters containing 2.0-kb and 850-bp of the mouse α₅promoter. Because perinatal expression of α₅was abundant in bronchiolar and alveolar epithelium, we assessed transcriptional control of α₅in 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 α₅transcription by acting on both the 2.0-kb and 850-bp α₅promoters. Site-directed mutagenesis revealed that TTF-1 activated α₅transcription by binding specific TTF-1 response elements. Exogenous TTF-1 also significantly induced α₅transcription.</p> <p>Conclusions</p> <p>These data demonstrate that α₅is specifically controlled in a temporal and spatial manner during pulmonary morphogenesis. Ongoing research may demonstrate that precise regulation of α₅is important during normal organogenesis and misexpression correlates with tobacco related lung disease.</p>