Plasmids and transfection

HA_hNKAa1_mMaple3, a N-terminal fusion protein of hemagglutinin and mMaple3 [24] to human Na,K-ATPase α1 was synthesized by GenScript. hNKAa1_SEP, a superecliptic pHluorin (W317-SEP-L318)—human Na,K-ATPase α1 fusion protein, was cloned as previously described [25]. Mock transfection were performed using Syntaxin-TC, a plasmid encoding for a plasma membrane anchor, linker and a tetracysteine motif for FlAsH binding. Syntaxin-TC was synthesized by GenScript. All transfections were performed using lipofectamine LTX (Life Technologies) with 2 μg DNA following recommended protocols by the provider.