Improvement of calcium handling and changes in
calcium-release properties after mini- or full-length dystrophin forced
expression in cultured skeletal myotubes
Eric Marchand, Bruno Constantin, Haouaria Balghi,
Marie-Christine Claudepierre, Anne Cantereau, Christophe Magaud, Aklesso
Mouzou, Guy Raymond, Serge Braun, and Christian Cognard - FRANCE
Abstract
Dystrophin is a cytoskeletal protein
normally expressed underneath the sarcolemma of muscle fibers. The lack of
dystrophin in Duchenne muscular Dystrophy (DMD) muscles results in fiber
necrosis, which was proposed to be mediated by chronic calcium mishandling. The
extensive comparison of dystrophic cells from human or mdx mice with normal
muscles have suggested that the lack of dystrophin may alter the resting
calcium permeability and steady-state levels of calcium, but this latter
observation remains controversial. It is also not clear, whether calcium
mishandling is resulting from the dystrophic process or if dystrophin can
directly regulate calcium handling in muscle cells.This prompted us to
determine if transfection of full-length dystrophin or Becker Muscular
Dystrophy (BMD) minidystrophin, a candidate for viral-mediated gene therapy,
could change calcium handling properties. We took advantage of specific
properties of Sol8 cell line showing the absence of dystrophin expression
together with a drastic calcium mishandling. Here, we show that full-length
dystrophin allowed the recovery of a low resting intracellular-free calcium
concentration together with lower calcium transients. We also show for the
first time that stable expression of minidystrophin was able to restore normal
calcium handling in Sol8 myotubes through a better control of steady-state
levels, calcium transients, and subcellular calcium events. It suggests that
dystrophin could play a regulatory role on calcium homeostasis apparatus and
that functional links exist between calcium signaling and cytoskeleton.