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Fig. 1 Functional screen for cardiac ion channels modulated by POPDC2 (A–D) Representative current traces of (A) HCN4, applying a voltage step from −30 mV to −120 mV within 6 s, from a holding potential of −30 mV, (B) Kv1.4, applying a voltage step from −80 mV to +40 mV within 2 s, from a holding potential of −80 mV, (C) Kv4.3, applying a voltage step from −80 mV to +40 mV within 2 s, from a holding potential of −80 mV or (D) Nav1.5, applying a voltage step from −80 mV to −20 mV within 50 ms, from a holding potential of −80 mV, expressed alone (black) or together with POPDC2 (blue) in Xenopus laevis oocytes. (E) Indicated cardiac channels or the Na+/K+ ATPase (Na/K) were expressed alone or together with POPDC2 in Xenopus oocytes and relative changes in current amplitudes by POPDC2 were plotted. Oocytes were stored in a storage solution lacking theophylline. The number of technical replicates (n) is indicated in parentheses. Data are presented as mean ± s.e.m. Significance was probed using a two-sided Student’s t-test. ∗∗∗, p < 0.001.