Abstract 16839: The Outer Mitochondrial Membrane Protein, mitoNEET, Sustains Structure of Mitochondrial Cristae

Abstract

Background: Mitochondria are essential organelles with various functions, and change its network dynamically. The inner mitochondrial membrane (IMM) contains the cristae membrane (CM), which extends into mitochondrial matrix space. A loss of mitofilin, one of the main component of mitochondrial contact site and cristae organizing system (MICOS) complex in the IMM, has known to be unable to preserve CM structure, accompanied with lower membrane potential. And a disruption of mitoNEET, novel protein located in the outer mitochondrial membrane, has been shown to decrease mitochondrial membrane potential, however, the role of mitoNEET in structure of the CM has not been elucidated. Methods and Results: mitoNEET flox/flox mice were generated with lox-P and homologous recombination strategies. Cardiac-specific deletion of mitoNEET (mitoNEET-knockout) was achieved using αMHC-Cre. Transmission electron microscopy showed the mitochondria isolated from mitoNEET-knockout mice reduced number of cristae, loss of the cristae junctions, and accumulation of cristae stack. These mitochondria also exhibited a swollen morphology. ROS production from the mitochondria were higher in mitoNEET-knockout mice. Mitochondrial state 3 respirations were comparable between the groups, however, mitochondrial maximal capacity and reserve capacity in mitoNEET-knockout mice. Mitochondrial membrane potential measured by using cultured cells transfected with CISD1 , encoding mitoNEET, siRNA was decreased in this condition compared to scramble. Mass spectrometry analysis revealed that endogenous mitoNEET coprecipitated with endogenous mitofilin, which is known to be localized in the IMM and involved in CM structure. Echocardiography showed cardiac dysfunction in mitoNEET-knockout mice. Conclusions: The protein-protein interaction between mitoNEET and mitofilin may regulate CM structure through the maintenance of MICOS complex including mitofilin. The lack of this interaction could induce mitochondrial dysfunction, suggesting that mitoNEET play an important role in the regulation of mitochondrial function via mitochondrial morphology.