Dystrophin Associates With Caveolae of Rat Cardiac Myocytes: Relationship to Dystroglycan

• Published in: Circulation research 2000-09, Vol.87 (6), p.480-488
• Main Authors: Doyle, Donald D, Goings, Gwen, Ambler, Judy Upshaw-Earley S. Kelly, Mondul, Alison, Palfrey, H Clive, Page, Ernest
• Format: Article
• Language: English
• Subjects: Animals; Biological and medical sciences; Caveolin 3; Caveolins; Cell Membrane - metabolism; Cell Membrane - ultrastructure; Cytoskeletal Proteins - metabolism; Dystroglycans; Dystrophin - metabolism; Fundamental and applied biological sciences. Psychology; Heart; Heart Atria - metabolism; Heart Atria - ultrastructure; Heart Ventricles - metabolism; Heart Ventricles - ultrastructure; In Vitro Techniques; Membrane Glycoproteins - metabolism; Membrane Proteins - metabolism; Microscopy, Confocal; Microscopy, Electron; Microscopy, Fluorescence; Myocardium - metabolism; Myocardium - ultrastructure; Organelles - metabolism; Organelles - ultrastructure; Precipitin Tests; Rats; Sarcolemma - metabolism; Sarcolemma - ultrastructure; Sheep; Vertebrates: cardiovascular system
• ISSN: 0009-7330; 1524-4571
• DOI: 10.1161/01.RES.87.6.480

The possibility of an interaction between the cytoskeletal protein dystrophin and cell surface caveolae in the mammalian myocardium was investigated by several techniques. Caveolin (cav)-3–enriched, detergent-insoluble membranes isolated from purified ventricular sarcolemma by density-gradient fractionation were found to contain dystrophin and dystroglycan. Further purification of cav-3–containing membranes by immunoprecipitation using anti–cav-3–coated magnetic beads yielded dystrophin but not always dystroglycan. Electron microscopic analysis of precipitated material revealed caveola-sized vesicular profiles that could be double-labeled with anti-dystrophin and anti–cav-3 antibodies. In contrast, immunoprecipitation of membranes with anti-dystrophin–coated beads yielded both cav-3 and dystroglycan. Electron microscopic analysis of this material showed heterogeneous membrane profiles, some of which could be decorated with anti–cav-3 antibodies. To confirm that dystrophin and cav-3 were closely associated in cardiac myocytes, we verified that dystrophin was also present in immunoprecipitated cav-3–containing membranes from detergent extracts, as well as in sonicated extracts of purified ventricular myocytes. Confocal immunofluorescence microscopy of ventricular and atrial cardiac myocytes showed that the cellular distributions of cav-3 and dystrophin partially overlapped. Immuno–electron micrographs of thin sections of rat atrial myocytes revealed a fraction of dystrophin molecules that are in apparently close apposition to caveolae. These results suggest that a subpopulation of dystrophin molecules interacts with cardiac myocyte caveolae in vivo and that some of the dystrophin is engaged in linking cav-3 with the dystroglycan complex.