Altered channel kinetics exhibited by PIEZO1 mutants. MA currents in HEK293 cells expressing wild-type or mutant PIEZO1 were examined using a whole-cell patch-clamp technique. (A) K1877del mutant. Left panel, representative traces of peak current amplitude of MA wild-type and PIEZO1-K1877del cells. Both faster channel kinetics and smaller peak current amplitude were observed for the K1877del mutant. Right panel, a comparison of averaged peak currents amplitude recorded at 6 μm from wild-type and K1877del mutant cells, with the K1877del mutant showing a significant decrease of peak current. (B) E2496ELE mutant. Representative traces of MA currents in wild-type (left) and PIEZO1-E2496ELE mutant (right) cells, as a function of depth of the indenting probe. The stimulus waveforms used in activation protocol are shown above the traces with the colors corresponding to each depth of indentation. The E2496ELE insertion mutant displayed increased inactivation rate compared with wild type. In addition, whereas wild-type channel inactivated completely, in 77% of records from the mutant, persistent mechanocurrent was observed, indicating incomplete channel closure. Bottom panel, a current recorded from an E2496ELE mutant at 11 µm displaying increased steady-state availability of the channel shown by the interruption in inactivating current. For presentation, a zoomed in view of the interrupted region is shown with the current peak cutoff.