Regulation of the ClC-2 lung epithelial chloride channel by glycosylation of SP1.
Chloride channel-2 (ClC-2) is a pH- and voltage-activated chloride channel that is highly expressed in mammalian fetal airway epithelia during the period of maximal fluid secretion. A high level of luminal ClC-2 protein expression is maintained by the SP1 transcription factor until SP1 and ClC-2 decline rapidly at birth. Using fetal (preII-19) and adult (L2) rat lung Type 2 cell lines, we demonstrate that the active higher-molecular-weight 105-kD isoform of SP1 is phosphorylated and glycosylated. Exposure of either cell line to high-dose glutamine is sufficient to induce glycosylation of SP1 and to induce and maintain ClC-2. Exposure to tunicamycin to inhibit SP1 glycosylation reduces ClC-2 expression. We also demonstrate that in vivo ClC-2 expression is similarly regulated. SP1 from 6-wk-old murine lung (high ClC-2 expression) is hyperphosphorylated and hyperglycosylated compared with SP1 from 16-wk-old lung (low ClC-2 expression). Our results support the hypothesis that glycosylation of SP1 produces the 105-kD isoform of SP1 and is involved in regulating ClC-2 gene expression.
Vij
Neeraj
N
Eudowood Division of Pediatric Respiratory Sciences, Department of Pediatrics, The Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA.
Zeitlin
Pamela L
PL
D000818:Animals; D000090007:CLC-2 Chloride Channels; D002460:Cell Line; D018118:Chloride Channels / Q000235:genetics / Q000378:metabolism*; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects; D005973:Glutamine / Q000494:pharmacology; D006031:Glycosylation; D008168:Lung / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D011499:Protein Processing, Post-Translational; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D020545:Respiratory Mucosa / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism; D016329:Sp1 Transcription Factor / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic; D014162:Transfection; D014415:Tunicamycin / Q000494:pharmacology
D000090007:CLC-2 Chloride Channels; D018118:Chloride Channels; C000715428:Clcn2 protein, mouse; C000715429:Clcn2 protein, rat; D012333:RNA, Messenger; D016329:Sp1 Transcription Factor; D005973:Glutamine; D014415:Tunicamycin