Transgenic overexpression of caveolin-3 in the heart induces a cardiomyopathic phenotype.

Caveolins are structural protein components of caveolar membrane domains. Caveolin-3, a muscle-specific member of the caveolin family, is expressed in skeletal muscle tissue and in the heart. The multiple roles that caveolin-3 plays in cellular physiology are becoming more apparent. We have shown that lack of caveolin-3 expression in skeletal muscle resembles limb-girdle muscular dystrophy-1C. In contrast, we have demonstrated that overexpression of caveolin-3 in skeletal muscle tissue promotes defects similar to those seen in Duchenne muscular dystrophy (DMD). Thus, a tight regulation of caveolin-3 expression is fundamental for normal muscle functions. Since caveolin-3 is also endogenously expressed in cardiac myocytes, and cardiomyopathies are observed in DMD patients, we looked at the effects of overexpression of caveolin-3 on cardiac structure and function by characterizing caveolin-3 transgenic mice. Our results indicate that overexpression of caveolin-3 causes severe cardiac tissue degeneration, fibrosis and a reduction in cardiac functions. We also show that dystrophin and its associated glycoproteins are down-regulated in caveolin-3 transgenic heart. In addition, we demonstrate that the activity of nitric oxide synthase (NOS) is down-regulated by high levels of caveolin-3 in the heart. Taken together, these results indicate that overexpression of caveolin-3 is sufficient to induce severe cardiomyopathy. In addition, these findings suggest that caveolin-3 transgenic mice may represent a valid mouse model for studying the molecular mechanisms underlying cardiomyopathies associated with Duchenne muscular dystrophy.