Calcium and the damage pathways in muscular dystrophyThis article is one of a selection of papers published in this special issue on Calcium Signaling.

Duchenne muscular dystrophy (DMD) is a severe muscle-wasting disease caused by the absence of the cytoskeletal protein dystrophin. Experiments on the mdx mouse, a model of DMD, have shown that mdx muscles are particularly susceptible to stretch-induced damage. In this review, we discuss evidence showing that a series of stretched contractions of mdx muscle fibres causes a prolonged increase in resting intracellular calcium concentration ([Ca 2+ ] i ). The rise in [Ca 2+ ] i is caused by Ca 2+ entry through a class of stretch-activated channels (SAC NSC ) for which one candidate gene is TRPC1. We review the evidence for activation of SAC NSC in muscle by reactive oxygen species (ROS) and suggest that stretch-induced ROS production is part of the pathway that triggers increased channel activity. When the TRPC1 gene was transfected into C2 myoblasts, expression occurred throughout the cell. Only when the TRPC1 gene was coexpressed with caveolin-3 did the TRPC1 protein express in the membrane. When TRPC1 was expressed in the membrane, it could be activated by ROS to produce Ca 2+ entry and this entry was inhibited by PP2, an inhibitor of src kinase. These results suggest that stretched contractions activate ROS production, which activates src kinase. Activity of this kinase causes opening of SAC NSC and allows Ca 2+ entry. This pathway appears to be a significant cause of muscle damage in DMD.