Fig. 1: Mitochondrial TCA cycle enzymes translocate to the nucleus upon doxorubicin treatment.

a, b Confocal microscopy images of hiPSC-derived cardiomyocytes treated with 1 µM doxorubicin for 6 or 24 h (DRN) or DMSO (control). The cells were stained with anti-isocitrate dehydrogenase (IDH-2) (a) or anti-citrate synthase (CS) (b) and detected with a secondary antibody conjugated with Alexa 594. Cells were stained with CoxIV and Troponin-T (TnT) as markers for mitochondria and cardiomyocytes, respectively. The signals from CoxIV and TnT were detected with secondary antibodies conjugated with Alexa-633 and Alexa-488, respectively. Scale bar: 20 µm. c–f 3-dimensional reconstituted z-stack images of control (c, e) and doxorubicin-treated cells (d, f) stained for MDH-2 (c, d) and IDH-2 (e, f), CoxIV, and TnT. Scale bar: 10 µm. g Immunoblots demonstrating the nuclear localization of IDH-3, PDH-E1, and MDH-2 in the nuclear fraction from cells treated with doxorubicin (DRN) for 6 or 24 h or from DMSO-treated control cells. TnT and Kir2.1 were probed to rule out the contamination of cytoplasmic fractions, and CoxIV was used as a mitochondrial marker in the isolated nuclear lysate. Whole-cell lysates from untreated cells were used as another control. h, i Immunostained images of cardiomyocytes isolated from mice treated with vehicle (h) or doxorubicin (i) for 72 h, cells stained for IDH-2, CoxIV, and TnT. Scale bar: 10 µm; images are represented along with the three-dimensional reconstruction of z-stack images.