Insulin-stimulated trafficking of ENaC in renal cells requires PI 3-kinase activity

1 Department of Biology, Indiana University-Purdue University at Indianapolis, Indianapolis 46202; and 2 Therapeutic Area Discovery Research and Chemistry Information Technology and 3 Cardiovascular Research, Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana 46285 ENaC-EGFP (enhanced green fluorescent protein-tagged -subunit of the epithelial Na + channel) stably transfected clonal lines derived from the A6 parental cell line were used to study the physical mechanisms of insulin-stimulated Na + transport. Within 1 min of insulin stimulation, ENaC migrates from a diffuse cytoplasmic localization to the apical and lateral membranes. Concurrently, after insulin stimulation, phosphatidylinositol 3-kinase (PI 3-kinase) is colocalized with ENaC on the lateral but not apical membrane. An inhibitor of PI 3-kinase, LY-294002, does not inhibit ENaC/PI 3-kinase colocalization but does alter the intracellular site of the colocalization, preventing the translocation of ENaC to the lateral and apical membranes. These data show that insulin stimulation causes the migration of ENaC to the lateral and apical cell membranes and that this trafficking is dependent on PI 3-kinase activity. epithelial sodium channels; phosphatidylinositol 3,4,5-bisphosphate; phosphatidylinositol 3-kinase; phosphoinositide pathway; transepithelial signal transduction; sodium transport