Influenza virus M2 targets cystic fibrosis transmembrane conductance regulator for lysosomal degradation during viral infection

We sought to determine the mechanisms by which influenza infection of human epithelial cells decreases cystic fibrosis transmembrane conductance regulator (CFTR) expression and function. We infected human bronchial epithelial (NHBE) cells and murine nasal epithelial (MNE) cells with various strains of influenza A virus. Influenza infection significantly reduced CFTR short circuit currents (Isc) and protein levels at 8 hours postinfection. We then infected CFTR expressing human embryonic kidney (HEK)-293 cells (HEK-293 CFTRwt) with influenza virus encoding a green fluorescent protein (GFP) tag and performed whole-cell and cell-attached patch clamp recordings. Forskolin-stimulated, GlyH-101-sensitive CFTR conductances, and CFTR open probabilities were reduced by 80% in GFP-positive cells; Western blots also showed significant reduction in total and plasma membrane CFTR levels. Knockdown of the influenza matrix protein 2 (M2) with siRNA, or inhibition of its activity by amantadine, prevented the decrease in ...