Fig 7. The sensitivity to H₂O₂ correlates with the catalytic activity of the NUDT9 domain.

(A), Representative whole cell patch-clamp experiment showing the stimulation of the variant nvTRPM2-NUDenz-AIF with H₂O₂ (10 mM) applied to the bath at the time point indicated by an arrow. The intracellular Ca²⁺ concentration was adjusted to 1 μM. Similar results were obtained from 6 independent experiments. (B) Summary of calcium imaging experiments. Maximal increases in (Ca²⁺)i, as indicated by an increased F340/F380 ratio, were evoked by extracellular application of H₂O₂ (10 mM). The variants nvTRPM2-NUDenz and nvTRPM2-NUDenz-AIF were compared with mock-transfected cells. (C) Sketch of the NUDT9 enzyme variants (wild-type hNUDT9 enzyme, hNUDT9H domain, nvNUDT9H domain) used for co-expression experiments with nvTRPM2-ΔNUD. (D) Calcium imaging experiments in response to H₂O₂ (10 mM), performed on cells co-expressing nvTRPM2-ΔNUD and one of the enzyme variants depicted in panel C. Comparison was performed with mock-transfected cells and cells transfected with nvTRPM2-ΔNUD alone. Asterisks indicate significant differences (* P < 0.05; *** P < 0.001) evaluated with a one-way ANOVA and the Bonferroni correction. (n = 8–26). Error bars are s.e.