Duchenne muscular dystrophy is associated with the inhibition of calcium uniport in mitochondria and an increased sensitivity of the organelles to the calcium-induced permeability transition

Abstract

Duchenne muscular dystrophy (DMD) is characterized by a pronounced and progressive degradation of the structure of skeletal muscles, which decreases their strength and lowers endurance of the organism. At muscular dystrophy, mitochondria are known to undergo significant functional changes, which is manifested in a decreased efficiency of oxidative phosphorylation and impaired energy metabolism of the cell. It is believed that the DMD-induced functional changes of mitochondria are mainly associated with the dysregulation of Ca2+ homeostasis. This work examines the kinetic parameters of Ca2+ transport and the opening of the Ca2+-dependent MPT pore in the skeletal-muscle mitochondria of the dystrophin-deficient C57BL/10ScSn-mdx mice. As compared to the organelles of wild-type animals, skeletal-muscle mitochondria of mdx mice have been found to be much less efficient in respect to Ca2+ uniport, with the kinetics of Na+-dependent Ca2+ efflux not changing. The data obtained indicate that the decreased rate of Ca2+ uniport in the mitochondria of mdx mice may be associated with the increased level of the dominant negative subunit of Ca2+ uniporter (MCUb). The experiments have also shown that in mdx mice, skeletal-muscle mitochondria have low resistance to the induction of MPT, which may be related to a significantly increased expression of adenylate translocator (ANT2), a possible structural element of the MPT pore. The paper discusses how changes in the expression of calcium uniporter and putative components of the MPT pore caused by the development of DMD can affect Ca2+ homeostasis of skeletal-muscle mitochondria.