Figure 2Effect of cl-HK2pep on cellular Ca2+ dynamics ER Ca2+ levels are measured by the FRET-based, D4ER fluorescent probe expressed in the lumen of ER (A) Data information: Experiments throughout the Figure are carried out on HeLa cells; cl-SCRpep, negative control of cl-HK2pep (2 μM each). Effect of cl-HK2pep on IP3 levels. IP3 levels are assessed with the GFP-PHD probe; histamine (100μM) is used as a positive control for IP3 generation; data are reported as mean of fluorescent signals±SEM (n=3 independent experiments; B) Data information: Experiments throughout the Figure are carried out on HeLa cells; cl-SCRpep, negative control of cl-HK2pep (2 μM each). Xe-C is Xestospongin C, which selectively inhibits IP3R at the 5 μM concentration used here [ Effect of cl-HK2pep on cellular Ca2+ dynamics changes in mitochondrial Ca2+ levels are recorded (C; scale bar: 20µm) Data information: Experiments throughout the Figure are carried out on HeLa cells; cl-SCRpep, negative control of cl-HK2pep (2 μM each). Effect of cl-HK2pep on cellular Ca2+ dynamics changes in mitochondrial Ca2+ levels are recorded and quantified using the GCAMP6f sensor (in D, as mean of 475/410 nm ratio; signal±SEM of at least 5 independent experiments and more than 20 cells analized) Data information: Experiments throughout the Figure are carried out on HeLa cells; cl-SCRpep, negative control of cl-HK2pep (2 μM each). Xe-C is Xestospongin C, which selectively inhibits IP3R at the 5 μM concentration used here Effect of cl-HK2pep on cellular Ca2+ dynamics (E) as percentage of cells with increased Ca2+ in mitochondria, with a threshold 475/410 ratio for positivity >3; baseline mean ratio=1.84±0.54) Data information: Experiments throughout the Figure are carried out on HeLa cells; cl-SCRpep, negative control of cl-HK2pep (2 μM each). Xe-C is Xestospongin C, which selectively inhibits IP3R at the 5 μM concentration used here [ Effect of cl-HK2pep on cellular Ca2+ dynamics with mitochondria-targeted aequorin (F, where data are reported as mean of [Ca2+]±SEM of 3 independent experimental days). Data information: Experiments throughout the Figure are carried out on HeLa cells; cl-SCRpep, negative control of cl-HK2pep (2 μM each). Effect of cl-HK2pep treatment on mitochondrial membrane potential assessed with the TMRM probe. Kinetic experiments (G, single cell analysis, n=216 cells analyzed in at least 10 independent experiments Effect of cl-HK2pep treatment on mitochondrial membrane potential assessed with the TMRM probe. Kinetic experiments H, representative field; scale bar: 20µm) Data information: Experiments throughout the Figure are carried out on HeLa cells; cl-SCRpep, negative control of cl-HK2pep (2 μM each). Where indicated, cells are kept in Ca2+ free medium plus 500 µM EGTA with or without 10 µM BAPTA-AM Effect of cl-HK2pep treatment on mitochondrial membrane potential assessed with the TMRM probe. quantified (I and J; TMRM fluorescence is normalized to initial value and expressed in percentage for each time point, with a depolarization threshold placed at 40% of initial value). Data information: Experiments throughout the Figure are carried out on HeLa cells; cl-SCRpep, negative control of cl-HK2pep (2 μM each). Where indicated, cells are kept in Ca2+ free medium plus 500 µM EGTA with or without 10 µM BAPTA-AM; Xe-C is Xestospongin C, which selectively inhibits IP3R at the 5 μM concentration used here