Figure 1.

Knockdown of MICU2 reduced mitochondrial Ca²⁺ uptake and decreased insulin secretion.MICU2 mRNA expression in INS-1 832/13 cells (A) and EndoC-βH1 cells (B) after treatment with scrambled or MICU2 siRNA. MICU2 protein expression (C) and quantification of Western blotting (D) in EndoC-βH1 cells. Mitochondrial Ca²⁺ ([Ca²⁺]_mito) determined by mito-case12 and Rhod2, respectively, in MICU2-silenced INS-1 832/13 (E and F) and EndoC-βH1 cells (G and H) after glucose stimulation. E and G show average traces while F and H show differences in maximal mitochondrial Ca²⁺ levels between control and MICU2-silenced cells. [Ca²⁺]_mito by mito-case12 and Rhod2, respectively, in MICU2-silenced INS-1 832/13 (I and J) and EndoC-βH1 cells (K and L) after stimulation with KCl; average traces (I and K) and differences in maximal [Ca²⁺]_mito (J and L) between control and MICU2-silenced cells are shown. Insulin secretion in INS-1 832/13 (M) and EndoC-βH1 cells (N); secretion after 1 h of incubation was normalized to levels in cells treated with scrambled siRNA at 2.8 mM of glucose. Data are from at least three independent experiments 72 h after addition of siRNA unless otherwise stated. Mean ± SEM are given. Comparisons were made with an unpaired two-tailed Student's t-test. ∗p < 0.05, ∗∗p < 0.01, ∗∗∗p < 0.001, and ∗∗∗∗p < 0.0001. See also Fig. S1.