Forskolin-induced cell shrinkage and apical translocation of functional enhanced green fluorescent protein-human alpha ENaC in H441 lung epithelial cell monolayers

Woollhead, A.M and Baines, D.L (2006) Forskolin-induced cell shrinkage and apical translocation of functional enhanced green fluorescent protein-human alpha ENaC in H441 lung epithelial cell monolayers Journal of Biological Chemistry, 281 (8). pp. 5158-5168. ISSN 1083-351X

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Official URL: http://dx.doi.org/10.1074/jbc.M509947200

Abstract

Elevation of intracellular cAMP increases fluid re-absorption in the lung by raising amiloride-sensitive Na+ transport through the apically localized epithelial, amiloride-sensitive Na+ channel (ENaC). However, the signaling pathways mediating this response are still not fully understood. We show that inhibition of protein-tyrosine kinase (PTK) with Genistein and protein kinase A (PKA) with KT5720, decreased forskolin-stimulated amiloride-sensitive short circuit current (Isc) across H441 adult human lung epithelial cell monolayers. KT5720 also decreased basal Isc. Stable expression of green fluorescent protein (GFP)-labeled human ENaC in H441 cells was used to investigate dynamic changes in the cellular localization of this protein in response to forskolin. Reverse transcription-PCR and immunoblotting analysis revealed two clones expressing a truncated (C3-5) and full-length (C3-3) EGFP-hENaC protein. Only the C3-3 clone displayed dome formation and exhibited a 50% increase in basal and forskolin-stimulated amiloride-sensitive Isc indicating that the full-length protein was required for functional activity. Apical surface biotinylation and real-time confocal microscopy demonstrated that EGFP-hENaC (C3-3) translocated to the apical membrane in response to forskolin in a Brefeldin A-sensitive manner. This effect was completely inhibited by Genistein but only partially inhibited by KT5720. Forskolin also induced a reduction in the height of cells within C3-3 monolayers, indicative of cell shrinkage. This effect was inhibited by KT5720 but not by Genistein or Brefeldin A. These data show that forskolin activates PKA-sensitive cell shrinkage in adult human H441 lung epithelial cell monolayers, which induces a PTK-sensitive translocation of EGFP-hENaC subunits to the apical membrane and increases amiloride-sensitive Na+ transport.

Item Type:Journal article
Subjects:C000 Biological and Biomedical Sciences
DOI (a stable link to the resource):10.1074/jbc.M509947200
Faculties:Faculty of Science and Engineering > School of Pharmacy and Biomolecular Sciences
ID Code:2705
Deposited By:editor spbs
Deposited On:15 Nov 2007
Last Modified:18 Jun 2010 12:33

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