Effect of R347 mutations on the PIP₂ modulation of Elk1. (A) R347E on cell currents recorded in response to 1-s voltage steps (−120 to 60 mV in 20-mV increments) from a holding potential of −100 mV. Insets show normalized currents at 20 mV from a patch on cell (black), excised (red), and plus 10 µM PIP₂ (blue). (B) τ_act(10 µM PIP₂)/τ_act(Ctrl) at various voltages for R347E (n = 9) and WT (n = 18). ***, P < 0.001; t test. (C) Normalized tail currents recorded at −100 mV after a 1-s prepulse to 60 mV, comparing R347E to WT on cell (top) and R347E excised before and after 10 µM PIP₂ application (bottom). (D–F) Repeat of A–C for R347C (n = 8); *, P < 0.05; t test. (G) G-V mode shift measured as in Fig. 2 (A and B) for R347 mutants compared with WT on cell, excised, and plus 10 µM PIP₂ (n reported in Table 2; *, P < 0.05; ***, P < 0.001; t test). (H and I) G-V curves for R347E and R347C on cell (black), excised (red), and plus 10 µM PIP₂ (blue) recorded from a −100-mV holding potential. V₅₀, s, and n numbers are reported for each plot in Table 1, and corresponding WT G-V curves are shown with dotted lines for comparison. All data are presented as mean ± SEM.