Real-time three-dimensional imaging of lipid signal transduction: Apical membrane insertion of epithelial Na+ channels

Bonnie L. Blazer-Yost, Judith C. Vahle, Jason M. Byars, Robert Bacallao

Research output: Contribution to journalArticle

47 Citations (Scopus)

Abstract

In the distal tubule, Na+ resorption is mediated by epithelial Na+ channels (ENaC). Hormones such as aldosterone, vasopressin, and insulin modulate ENaC membrane targeting, assembly, and/or kinetic activity, thereby regulating salt and water homeostasis. Insulin binds to a receptor on the basal membrane to initiate a signal transduction cascade that rapidly results in an increase in apical membrane ENaC. Current models of this signaling pathway envision diffusion of signaling intermediates from the basal to the apical membrane. This necessitates diffusion of several high-molecular-weight signaling elements across a three-dimensional space. Transduction of the insulin signal involves the phosphoinositide pathway, but how and where this lipid-based signaling pathway controls ENaC activity is not known. We used tagged channels, biosensor lipid probes, and intravital imaging to investigate the role of lipids in insulin-stimulated Na+ flux. Insulin-stimulated delivery of intracellular ENaC to apical membranes was concurrent with plasma membrane-limited changes in lipid composition. Notably, in response to insulin, phosphatidylinositol 3,4,5-trisphosphate (PIP3) formed in the basolateral membrane, rapidly diffused within the bilayer, and crossed the tight junction to enter the apical membrane. This novel signaling pathway takes advantage of the fact that the lipids of the plasma membrane's inner leaflet are not constrained by the tight junction. Therefore, diffusion of PIP3 as a signal transduction intermediate occurs within a planar surface, thus facilitating swift responses and confining and controlling the signaling pathway.

Original languageEnglish
JournalAmerican Journal of Physiology - Cell Physiology
Volume287
Issue number6 56-6
DOIs
StatePublished - Dec 2004

Fingerprint

Epithelial Sodium Channels
Signal transduction
Three-Dimensional Imaging
Signal Transduction
Membranes
Lipids
Imaging techniques
Insulin
Tight Junctions
Cell membranes
Cell Membrane
Biosensing Techniques
Phosphatidylinositols
Aldosterone
Vasopressins
Biosensors
Homeostasis
Salts
Molecular Weight
Molecular weight

Keywords

  • Insulin-stimulated Na transport
  • Metabolic syndrome
  • Phosphatidylinositol 3,4,5-trisphosphate
  • Real-time confocal imaging

ASJC Scopus subject areas

  • Clinical Biochemistry
  • Cell Biology
  • Physiology

Cite this

Real-time three-dimensional imaging of lipid signal transduction : Apical membrane insertion of epithelial Na+ channels. / Blazer-Yost, Bonnie L.; Vahle, Judith C.; Byars, Jason M.; Bacallao, Robert.

In: American Journal of Physiology - Cell Physiology, Vol. 287, No. 6 56-6, 12.2004.

Research output: Contribution to journalArticle

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