Aceylated Cyclophilin D Regulates Mitochondrial Function in the Developing Mouse Heart

Abstract

Mitochondria provide energy in form of ATP in mature eukaryotic cells. However, it is not clear, when and how during the embryonic cardiac development, mitochondria become able to regulate oxidative phosphorylation (OXPHOS) and prevent opening of the permeability transition pore (mPTP). Maturation of heart mitochondria is regulated by the activity of acetylated cyclophilin D (CypD). Cardiac tissue homogenates or isolated mitochondria ranging in age from embryonic (E) day 9.5 to adult wild-type mice were used to measure oxygen consumption, the expression of proteins of the electron transport chain and their assembly into supercomplexes was followed by denaturing and native electrophoresis. The expression of CypD and its acetylation status was assessed by western blotting and densitometry. n the heart of mouse embryos at E 9.5 mitochondrial electron transport chain (ETC) activity and OXPHOS are not coupled (respiratory control ratio (RCR) 1.48 ± 0.17, n=9). Addition of 1 µM cyclosporin A, an inhibitor of CypD D and the mPTP acutely increases the RCR to 3.69 ± 0.59 n=5). At E13.5, the end of the embryonic period in the mouse, OXPHOS is coupled and not significantly different from the adult heart. The enzymatic activity of the ETC complexes I, II, III and V increases significantly from E9.5 to the adult heart and the assembly of mitochondrial supercomplexes begins at about E13.5. Similarly, the expression of CypD increases as the heart matures. However, the detection of acetylated CypD decreases and the ratio of acetylated CypD to the total expressed CypD decreases from 1.1 ± 0.16 (n=3) at E9.5 to 0.54 ± 0.06 (n=3) in the adult heart. The activity of acetylated CypD regulates maturation of mitochondrial function in the developing heart.