Identification and Characterization of the Dystrophin Anchoring Site on -Dystroglycan

doi:10.1074/jbc.270.45.27305

Identification and Characterization of the Dystrophin Anchoring Site on -Dystroglycan (*)

From the (1) Howard Hughes Medical Institute and the
(2) Department of Physiology and Biophysics, University of Iowa College of Medicine, Iowa City, Iowa 52242 and the
(3) Department of Human Genetics and
(4) Human Genome Center, University of Michigan Medical School, Ann Arbor, Michigan 48109

^¶ Investigator of the Howard Hughes Medical Institute. To whom all correspondence should be addressed:
Howard Hughes Medical Institute, University of Iowa College of Medicine, 400 Eckstein Medical Research Bldg., Iowa City, Iowa 52242.
Tel.: 319-335-7867; Fax: 319-335-6957; kevin-campbell{at}uiowa.edu.

Abstract

Dystrophin, the product of the Duchenne muscular dystrophy gene, is tightly associated with the sarcolemmal membrane to a large glycoprotein complex. One function of the dystrophin-glycoprotein complex is to link the cytoskeleton to the extracellular matrix in skeletal muscle. However, the molecular interactions of dystrophin with the membrane components of the dystrophin-glycoprotein complex are still elusive. Here, we demonstrate and characterize a specific interaction between β-dystroglycan and dystrophin. We show that skeletal muscle and brain dystrophin as well as brain dystrophin isoforms specifically bind to β-dystroglycan. To localize and characterize the dystrophin and β-dystroglycan interaction domains, we reconstituted the interaction in vitro using dystrophin fusion proteins and in vitro translated β-dystroglycan. We demonstrated that the 15 C-terminal amino acids of β-dystroglycan constituted a unique binding site for the second half of the hinge 4 and the cysteine-rich domain of dystrophin (amino acids 3054-3271). This dystrophin binding site is located in a proline-rich environment of β-dystroglycan within amino acids 880-895. The identification of the interaction sites in dystrophin and β-dystroglycan provides further insight into the structure and the molecular organization of the dystrophin-glycoprotein complex at the sarcolemma membrane and will be helpful for studying the pathogenesis of Duchenne muscular dystrophy.

Footnotes

↵^§ Supported by a fellowship from the American Heart Association, Iowa Affiliate.
↵* This work was supported in part by the Muscular Dystrophy Association and Association Fran¸aise contre les Myopathies. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore by hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
↵¹ The abbreviations used are:

DGC

dystrophin-glycoprotein complex

GST

glutathione S-transferase

β-DGct

β-dystroglycan C terminus

PAGE

polyacrylamide gel electrophoresis.
- Received June 23, 1995.