cAMP-stimulated Na+ transport in H441 distal lung epithelial cells: role of PKA, phosphatidylinositol 3-kinase, and sgk1.
H441 cells, a bronchiolar epithelial cell line, develop a cAMP-regulated benzamil-sensitive Na+ transport pathway on permeable supports (Itani OA, Auerbach SD, Husted RF, Volk KA, Ageloff S, Knepper MA, Stokes JB, Thomas CP. Am J Physiol Lung Cell Mol Physiol 282: L631-L641, 2002). To understand the molecular basis for the stimulation of Na+ transport, we delineated the role of specific intracellular pathways and examined the effect of cAMP on alphabetagamma-epithelial Na+ channel (ENaC) and sgk1 expression. Na+ transport increases within 5 min of cAMP stimulation and is sustained for >24 h. The sustained effect of cAMP on Na+ transport is abolished by LY-294002, an inhibitor of phosphatidylinositol 3-kinase, by H89, an inhibitor of PKA, or by SB-202190, an inhibitor of p38 MAP kinase. The sustained effect of cAMP was associated with increases in alpha-ENaC mRNA and protein but without a detectable increase in betagamma-ENaC and sgk1. The early effect of cAMP on Na+ transport is brefeldin sensitive and is mediated via PKA. These results are consistent with a model where the early effect of cAMP is to increase trafficking of Na+ channels to the apical cell surface whereas the sustained effect requires the synthesis of alpha-ENaC.
Thomas
Christie P
CP
Department of Internal Medicine, University of Iowa College of Medicine, Iowa City, Iowa 52242, USA. christie-thomas@uiowa.edu
Campbell
Jason R
JR
Wright
Patrick J
PJ
Husted
Russell F
RF
D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D001692:Biological Transport / Q000187:drug effects; D002460:Cell Line; D002867:Chromones / Q000494:pharmacology; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000502:physiology*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D003907:Dexamethasone / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D053503:Epithelial Sodium Channels; D006801:Humans; D017874:Immediate-Early Proteins; D007700:Kinetics; D008168:Lung; D009025:Morpholines / Q000494:pharmacology; D009687:Nuclear Proteins / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D020545:Respiratory Mucosa / Q000187:drug effects / Q000502:physiology*; D012964:Sodium / Q000378:metabolism*; D015222:Sodium Channels / Q000502:physiology; D048051:p38 Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D000099184:Serum-Glucocorticoid Regulated Kinases
D015056:1-Methyl-3-isobutylxanthine; D002867:Chromones; D005576:Colforsin; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D003907:Dexamethasone; D004791:Enzyme Inhibitors; D053503:Epithelial Sodium Channels; D017874:Immediate-Early Proteins; D009025:Morpholines; D009687:Nuclear Proteins; D019869:Phosphatidylinositol 3-Kinases; D017346:Protein Serine-Threonine Kinases; D012964:Sodium; D015222:Sodium Channels; D048051:p38 Mitogen-Activated Protein Kinases; D000099184:Serum-Glucocorticoid Regulated Kinases; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one