Journal of Biological Chemistry
Volume 279, Issue 12, 19 March 2004, Pages 10946-10954
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Glycobiology and Extracellular Matrices
Molecular Dissection of the α-Dystroglycan- and Integrin-binding Sites within the Globular Domain of Human Laminin-10*

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The adhesive interactions of cells with laminins are mediated by integrins and non-integrin-type receptors such as α-dystroglycan and syndecans. Laminins bind to these receptors at the C-terminal globular domain of their α chains, but the regions recognized by these receptors have not been mapped precisely. In this study, we sought to locate the binding sites of laminin-10 (α5β1γ1) for α3β1 and α6β1 integrins and α-dystroglycan through the production of a series of recombinant laminin-10 proteins with deletions of the LG (laminin G-like) modules within the globular domain. We found that deletion of the LG4–5 modules did not compromise the binding of laminin-10 to α3β1 and α6β1 integrins but completely abrogated its binding to α-dystroglycan. Further deletion up to the LG3 module resulted in loss of its binding to the integrins, underlining the importance of LG3 for integrin binding by laminin-10. When expressed individually as fusion proteins with glutathione S-transferase or the N-terminal 70-kDa region of fibronectin, only LG4 was capable of binding to α-dystroglycan, whereas neither LG3 nor any of the other LG modules retained the ability to bind to the integrins. Site-directed mutagenesis of the LG3 and LG4 modules indicated that Asp-3198 in the LG3 module is involved in the integrin binding by laminin-10, whereas multiple basic amino acid residues in the putative loop regions are involved synergistically in the α-dystroglycan binding by the LG4 module.

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*

This work was supported by special coordination funds and grants-in-aid from the Ministry of Education, Science, Sports, and Culture of Japan (to K. S.) and the Muscular Dystrophy Association (to A. C. C. and J. M. E.). The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.