I-K) Mitochondrial Ca2+ was determined in WT and Mfn2 KO MEFs loaded with Rhod2. The effect of (I) caffeine-induced (20 mM), (J) IP3R activation with ATP-induced (100 μM) and (K) histamine-induced (100 μM) ER Ca2+ release on mitochondrial Ca2+ was measured (n= 30 cells from 3 independent experiments). Data are presented as mean ± SEM. 