Protein kinase A and mitogen-activated protein kinase pathways mediate cAMP induction of α-epithelial Na+ channels (α-ENaC)

Shamimunisa B. Mustafa, Robert Castro, Alison J. Falck, Jean A. Petershack, Barbara M. Henson, Yvonne M. Mendoza, Ahsan Choudary, Steven R. Seidner

Research output: Contribution to journalArticlepeer-review

24 Scopus citations

Abstract

A major mechanism for Na+ transport across epithelia occurs through epithelial Na+ channels (ENaC). ENaC is a multimeric channel consisting of three subunits (α, β, and γ). The α-subunit is critical for ENaC function. In specific culture conditions, the rat submandibular gland epithelial cell line (SMG-C6) demonstrates minimal Na + transport properties and exposure to dibutyryl cAMP (DbcAMP) for up to 48 h caused an elevation of α-ENaC mRNA and protein expression and amiloride-sensitive short-circuit current (ISC). Here we examined the early signaling pathways evoked by DbcAMP which contribute to the eventual increase in Na+ transport. Treatment with either of the protein kinase A (PKA) inhibitors KT5720 or H-89 followed by exposure to 1 mM DbcAMP for 24 h markedly attenuated DbcAMP-induced α-ENaC protein formation and ISC. Exposure of SMG-C6 cells to 1 mM DbcAMP induced a rapid, transient phosphorylation of the cAMP response element binding protein (CREB). This response was attenuated in the presence of either KT5720 or H-89. Dominant-negative CREB decreased DbcAMP-induced α-ENaC expression. Suppression of the extracellular signal-regulated protein kinase (ERK 1,2) with PD98059 or the p38 mitogen-activated protein kinase (MAPK) pathway with SB203580 reduced DbcAMP-induced α-ENaC protein levels in SMG-C6 cells. DbcAMP-induced phosphorylation of CREB was markedly attenuated by PD98059 or SB203580. DbcAMP-induced activation of the either the p38 or the ERK 1,2 MAPK pathways was abolished by either of the PKA inhibitors, H-89 or KT5720. Cross talk between these signaling pathways induced by DbcAMP via the activation of CREB appears to contribute to increased levels of α-ENaC observed after 24 h of treatment in SMG-C6 epithelial cells.

Original languageEnglish (US)
Pages (from-to)101-110
Number of pages10
JournalJournal of Cellular Physiology
Volume215
Issue number1
DOIs
StatePublished - Apr 1 2008

ASJC Scopus subject areas

  • Physiology
  • Clinical Biochemistry
  • Cell Biology

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