Differential Heparin Inhibition of Skeletal Muscle 
-Dystroglycan Binding to Laminins (*)
- ¶To whom correspondence should be addressed: Dept. of Physiology, University of Wisconsin, 120 Service Memorial Inst., 1300 University Ave., Madison, WI 53706. Tel.: 608-265-3419; Fax: 608-265-5512; :ervasti{at}facstaff.wisc.edu.
Abstract
The laminin binding properties of α-dystroglycan purified from rabbit skeletal muscle membranes were examined. In a solid
phase microtiter assay, 
I-laminin (laminin-1) bound to purified α-dystroglycan in a specific and saturable manner with a half-maximal concentration
of 8 nM. The binding of 
I-α-dystroglycan to native laminin and merosin (a mixture of laminin-2 and −4) was also compared using the solid phase assay.
The absolute binding of 
I-α-dystroglycan to laminin (6955 ± 250 cpm/well) was similar to that measured for merosin (7440 ± 970 cpm/well). However,
inclusion of 1 mg/ml heparin in the incubation medium inhibited 
I-α-dystroglycan binding to laminin by 84 ± 4.3% but inhibited 
I-α-dystroglycan binding to merosin by only 17 ± 5.2%. Similar results were obtained with heparan sulfate, while de-N-sulfated heparin, hyaluronic acid, and chondroitin sulfate had no differential effect. These results were confirmed by iodinated
laminin and merosin overlay of electrophoretically separated and blotted dystrophin-glycoprotein complex. In contrast to the
results obtained with skeletal muscle α-dystroglycan, both laminin and merosin binding to purified brain α-dystroglycan was
significantly inhibited by heparin. Our data support the possibility that one or more heparan sulfate proteoglycans may specifically
modulate the interaction of α-dystroglycan with different extracellular matrix proteins in skeletal muscle.
Footnotes
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↵§ Supported in part by an American Heart Association of Wisconsin predoctoral fellowship.
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↵* This study was funded by grants from the American Heart Association (Wisconsin affiliate) and the Muscular Dystrophy Association and by National Institutes of Health Grant AR42423 (to J. M. E.). 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.
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↵1 The abbreviations used are:
- TBS
-
Tris-buffered saline
- BSA
-
bovine serum albumin.
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- Received August 28, 1995.
- Revision received November 10, 1995.
- © 1996 by The American Society for Biochemistry and Molecular Biology, Inc.
