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Fig. 4 POPDC2 reduces Nav1.5 current amplitudes in a cAMP-dependent manner (A) POPDC2 modulation of Nav1.5 is cAMP-dependent. Representative current traces recorded by voltage steps to −20 mV. Oocytes were injected with 10 ng Nav1.5 alone or 10 ng Nav1.5 together with 5 ng POPDC2 (50%) or 10 ng POPDC2 (100%), and stored in ND96 solution with or without theophylline before voltage-clamp measurements in oocytes. Inset illustrates the applied voltage protocol. (B) Analyses of peak current amplitudes from experiments performed in (A), analyzed at −20 mV and normalized to Nav1.5. The number of technical replicates (n) is indicated in bar graphs. Data are presented as mean ± s.e.m. Significance was probed using a two-sided Student’s t-test. ∗, p < 0.05; ∗∗∗, p < 0.001. (C) Oocytes were injected as in (A-B) but incubated in a storage solution containing theophylline. Relative current amplitudes were analyzed at −20 mV and normalized to Nav1.5. The number of technical replicates is indicated in bar graphs. Data are presented as mean ± s.e.m. See also Figure S4.