Fig. 2: Characterization of BRIC in vitro and cultured cells.

a Schematic illustration of the domain arrangement of BRIC. b Bioluminescence spectra of BRIC in the presence of DTZ and indicated concentrations of free Ca²⁺. c Ca²⁺-dependency of BRIC bioluminescence at the peak emission wavelength (595 nm). n = 3 technical repeats. A one-site binding model was used to fit the data and derive the dissociation constant (K_d = 133 ± 24 nM). d Ratios of BRIC bioluminescence in the presence (39 μM) to the absence of Ca²⁺ across the indicated pH range. n = 3 technical repeats. e Representative pseudocolored bioluminescence images (left) and intensity traces (right) of histamine-induced Ca²⁺ dynamics in HeLa cells. Arrows indicate individual cells, and the colors of the arrows are identical to the colors of the intensity traces. The baselines of the intensity traces were corrected for monoexponential decay caused by substrate consumption. The experiment was repeated five times with similar results. Scale bar, 20 μm. f Representative fluorescence and bioluminescence images of BRIC- or BREP-expressing primary mouse neurons. High K⁺ (30 mM) was used to depolarize the neurons. Scale bar, 40 μm. g Quantification of bioluminescence intensity changes of neurons in response to high K⁺. The baselines were corrected using a monoexponential decay model. Data are presented as mean ± s.d. (n = 16 cells), and the P value was derived from unpaired two-tailed t-tests. The GraphPad Prism software does not provide extract P values below 0.0001. BL, bioluminescence. Arb. units, arbitrary units. Source data are provided as a Source Data file.