Essential Structural Features of TNF-α Lectin-like Domain Derived Peptides for Activation of Amiloride-Sensitive Sodium Current in A549 Cells

The amiloride-sensitive epithelial sodium channel (ENaC) plays a prominent role in sodium uptake from alveolar fluid and is the major component in alveolar fluid clearance in normal and diseased lungs. The lectin-like domain of TNF-alpha has been shown to activate amiloride-sensitive sodium uptake in type II alveolar epithelial cells. Therefore, several synthetic peptides that mimic the lectin-like domain of TNF-alpha. (TIP) were synthesized and their ability to enhance sodium current through ENaC was studied in A549 cells with the patch clamp technique. Our data suggest that a free positively charged N-terminal amino group on residue I and/or a free negatively charged carboxyl group on residue 17 of the TIP peptide is essential for the ENaC-activating effect. Ventilation strategies apart, no standard treat neat exists for pulmonary permeability edema. Therefore, novel therapies activating sodium uptake from the alveolar fluid via ENaC could improve clinical outcome.