Modulation of Sp1 and Sp3 in lung epithelial cells regulates ClC-2 chloride channel expression.
ClC-2 is a pH- and voltage- activated chloride channel, which is highly expressed in fetal airways and downregulated at birth. The ClC-2 promoter contains consensus binding sites within the first 237 bp, which bind transcription factors Sp1 and Sp3(1). This study directly links Sp1 and Sp3 with ClC-2 protein expression by demonstrating: (i) induction of ClC-2 protein by transient overexpression of each transcription factor in adult rat Type II cells, which have low levels of ClC-2; and (ii) reduction of ClC-2 expression by incubation with a competitive inhibitor of Sp1 and Sp3 in fetal rat Type II cells, which have high levels of endogenous ClC-2. Endogenous fetal lung Sp1 is differentially expressed as two major species of 105 kD and 95 kD. Although low-level expression of Sp1 in adult cells is almost exclusively the 105-kD species, overexpression of Sp1 results in increased expression of the 95-kD band. These experiments suggest that the mechanism for postnatal reduction of ClC-2 expression in lung epithelia is based on decreased interaction of Sp1 and Sp3 with the ClC-2 promoter.[1]References
- Modulation of Sp1 and Sp3 in lung epithelial cells regulates ClC-2 chloride channel expression. Holmes, K.W., Hales, R., Chu, S., Maxwell, M.J., Mogayzel, P.J., Zeitlin, P.L. Am. J. Respir. Cell Mol. Biol. (2003) [Pubmed]
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