Spatial Relationship of the C-Terminal Domains of Dystrophin and ß-Dystroglycan in Cardiac Muscle Support a Direct Molecular Interaction at the Plasma Membrane Interface

From the National Heart and Lung Institute, Imperial College School of Medicine (S.S., S.R., N.J.S.), London, England, and the School of Neuroscience (M.J.C), University of Newcastle on Tyne (England).

Correspondence to Professor N.J. Severs, Department of Cardiac Medicine, National Heart and Lung Institute, Imperial College School of Medicine, Royal Brompton Hospital, Sydney St, London SW3 6NP, England. E-mail n.severs{at}ic.ac.uk

Abstract—Dystrophin and ß-dystroglycan are components of a complex of at least nine proteins (the dystrophin-glycoprotein complex) that physically link the membrane cytoskeleton in skeletal and cardiac muscle, through the plasma membrane, to the extracellular matrix. Mutations in the dystrophin gene, which result in an absence or a quantitative or qualitative alteration of dystrophin, cause a subset of familial dilated cardiomyopathies as well as Duchenne and Becker muscular dystrophy. Biochemical studies on isolated skeletal muscle molecules indicate that dystrophin is bound to the glycoprotein complex via ß-dystroglycan, with the C-terminus of ß-dystroglycan binding to the cysteine-rich domain and first half of the C-terminal domain of dystrophin. Ultrastructural labeling has demonstrated a close spatial relationship between dystrophin and ß-dystroglycan in intact skeletal muscle, but no previous ultrastructural labeling studies have examined the dystrophin/ß-dystroglycan interaction in cardiac muscle. In the present study, we have applied complementary immunoconfocal microscopy and double immunogold fracture-label, a freeze-fracture cytochemical technique that allows high-resolution visualization of labeled membrane components in thin section and in platinum-carbon replicas, to investigate the spatial relationship between dystrophin and ß-dystroglycan in rat cardiac muscle. When immunogold probes of two different sizes for the two proteins were used, "doublets" representing side-by-side antibody labeling were demonstrated in en face views at the level of the plasma membrane. The results support the conclusions that dystrophin and ß-dystroglycan directly interact at the cytoplasmic face of the rat cardiac muscle plasma membrane.

Key Words: dystrophin • ß-dystroglycan • cytoskeleton • freeze-fracture cytochemistry • confocal microscopy

This article has been cited by other articles:

				Y. Yue, Z. Li, S. Q. Harper, R. L. Davisson, J. S. Chamberlain, and D. Duan Microdystrophin Gene Therapy of Cardiomyopathy Restores Dystrophin-Glycoprotein Complex and Improves Sarcolemma Integrity in the Mdx Mouse Heart Circulation, September 30, 2003; 108(13): 1626 - 1632. [Abstract] [Full Text] [PDF]

				Y.-S. Ko, H.-I Yeh, S. Rothery, E. Dupont, S. R. Coppen, and N. J. Severs Connexin Make-up of Endothelial Gap Junctions in the Rat Pulmonary Artery as Revealed by Immunoconfocal Microscopy and Triple-label Immunogold Electron Microscopy J. Histochem. Cytochem., May 1, 1999; 47(5): 683 - 692. [Abstract] [Full Text]