Structure and assembly of the dystrophin glycoprotein complex

Abstract

The dystrophin glycoprotein complex (DGC) has a crucial role in maintaining cell membrane stability and integrity by connecting the intracellular cytoskeleton with the surrounding extracellular matrix1, 2–3. Dysfunction of dystrophin and its associated proteins results in muscular dystrophy, a disorder characterized by progressive muscle weakness and degeneration4,5. Despite the important roles of the DGC in physiology and pathology, its structural details remain largely unknown, hindering a comprehensive understanding of its assembly and function. Here we isolated the native DGC from mouse skeletal muscle and obtained its high-resolution structure. Our findings unveil a markedly divergent structure from the previous model of DGC assembly. Specifically, on the extracellular side, β-, γ- and δ-sarcoglycans co-fold to form a specialized, extracellular tower-like structure, which has a central role in complex assembly by providing binding sites for α-sarcoglycan and dystroglycan. In the transmembrane region, sarcoglycans and sarcospan flank and stabilize the single transmembrane helix of dystroglycan, rather than forming a subcomplex as previously proposed6, 7–8. On the intracellular side, sarcoglycans and dystroglycan engage in assembly with the dystrophin–dystrobrevin subcomplex through extensive interaction with the ZZ domain of dystrophin. Collectively, these findings enhance our understanding of the structural linkage across the cell membrane and provide a foundation for the molecular interpretation of many muscular dystrophy-related mutations.