Cell
Volume 117, Issue 7, 25 June 2004, Pages 953-964
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Article
Molecular Recognition by LARGE Is Essential for Expression of Functional Dystroglycan

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Abstract

Reduced ligand binding activity of α-dystroglycan is associated with muscle and central nervous system pathogenesis in a growing number of muscular dystrophies. Posttranslational processing of α-dystroglycan is generally accepted to be critical for the expression of functional dystroglycan. Here we show that both the N-terminal domain and a portion of the mucin-like domain of α-dystroglycan are essential for high-affinity laminin-receptor function. Posttranslational modification of α-dystroglycan by glycosyltransferase, LARGE, occurs within the mucin-like domain, but the N-terminal domain interacts with LARGE, defining an intracellular enzyme-substrate recognition motif necessary to initiate functional glycosylation. Gene replacement in dystroglycan-deficient muscle demonstrates that the dystroglycan C-terminal domain is sufficient only for dystrophin-glycoprotein complex assembly, but to prevent muscle degeneration the expression of a functional dystroglycan through LARGE recognition and glycosylation is required. Therefore, molecular recognition of dystroglycan by LARGE is a key determinant in the biosynthetic pathway to produce mature and functional dystroglycan.

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These authors contributed equally to this work.