Freeze-fracture replica immunolabelling reveals caveolin-1 in the human cardiomyocyte plasma membrane.

Mutations in or ablation of the gene encoding caveolin-3, a protein of muscle cell caveolae, result in forms of muscular dystrophy and cardiomyopathy. Another member of the caveolin gene family, caveolin-1, is widely considered not to be expressed in myocytes, yet ablation of the gene encoding this protein in mice also results in cardiomyopathy. By applying the high-resolution electron-microscopical imaging technique of freeze-fracture replica immunolabelling, we report here evidence that caveolin-1 is expressed in human cardiac myocytes, localized to both caveolae and non-caveolar domains in the plasma membrane. Disorders of the myocyte resulting from defects in caveolin-1 may thus arise directly, at the level of the myocyte, rather than via other cell types as previously proposed.