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

ENaC-EGFP (enhanced green fluorescentprotein-tagged -subunit of the epithelial Na⁺ channel)stably transfected clonal lines derived from the A6 parental cell linewere used to study the physical mechanisms of insulin-stimulatedNa⁺ transport. Within 1 min of insulin stimulation, ENaCmigrates from a diffuse cytoplasmic localization to the apical andlateral membranes. Concurrently, after insulin stimulation,phosphatidylinositol 3-kinase (PI 3-kinase) is colocalized with ENaC onthe lateral but not apical membrane. An inhibitor of PI 3-kinase,LY-294002, does not inhibit ENaC/PI 3-kinase colocalization but doesalter the intracellular site of the colocalization, preventing thetranslocation of ENaC to the lateral and apical membranes. These datashow that insulin stimulation causes the migration of ENaC to thelateral and apical cell membranes and that this trafficking isdependent on PI 3-kinase activity.