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¹ University Lyon 1, CNRS, Laboratory of Integrative, Cellular and Molecular Physiology, Villeurbanne, F-69622, France

Caveolins are membrane scaffolding proteins that associate with and regulate a variety of signalling proteins, including ion channels. A deficiency in caveolin-3 (Cav-3), the major striated muscle isoform, is responsible for skeletal muscle disorders, such as limb-girdle muscular dystrophy 1C (LGMD 1C). The molecular mechanisms leading to the muscle wasting that characterizes this pathology are poorly understood. Here we show that a loss of Cav-3 induced by the expression of the LGMD 1C-associated mutant P104L (Cav-3^P104L) provokes a reduction by half of the maximal conductance of the voltage-dependent L-type Ca²⁺ channel in mouse primary cultured myotubes and fetal skeletal muscle fibres. Confocal immunomiscrocopy indicated a colocalization of Cav-3 and Ca_v1.1, the pore-forming subunit of the L-type Ca²⁺ channel, at the surface membrane and in the developing T-tubule network in control myotubes and fetal fibres. In myotubes expressing Cav-3^P104L, the loss of Cav-3 was accompanied by a 66% reduction in Ca_v1.1 mean labelling intensity. Our results suggest that Cav-3 is involved in L-type Ca²⁺ channel membrane function and localization in skeletal muscle cells and that an alteration of L-type Ca²⁺ channels could be involved in the physiopathological mechanisms of caveolinopathies.

(Received 2 November 2006; accepted after revision 18 February 2007; first published online 22 February 2007)
Corresponding author C. Berthier: Université Lyon 1, CNRS, Physiologie Intégrative, Cellulaire et Moléculaire, Villeurbanne, F-69622, France.  Email: christine.berthier{at}university-lyon1.fr

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