title: Dystrophin contains multiple independent membrane-binding domains.
abstract: Dystrophin is a large sub-sarcolemmal protein. Its absence leads to Duchenne muscular dystrophy (DMD). Binding to the sarcolemma is essential for dystrophin to protect muscle from contraction-induced injury. It has long been thought that membrane binding of dystrophin depends on its cysteine-rich (CR) domain. Here, we provide in vivo evidence suggesting that dystrophin contains three additional membrane-binding domains including spectrin-like repeats (R)1-3, R10-12 and C-terminus (CT). To systematically study dystrophin membrane binding, we split full-length dystrophin into ten fragments and examined subcellular localizations of each fragment by adeno-associated virus-mediated gene transfer. In skeletal muscle, R1-3, CR domain and CT were exclusively localized at the sarcolemma. R10-12 showed both cytosolic and sarcolemmal localization. Importantly, the CR-independent membrane binding was conserved in murine and canine muscles. A critical function of the CR-mediated membrane interaction is the assembly of the dystrophin-associated glycoprotein complex (DGC). While R1-3 and R10-12 did not restore the DGC, surprisingly, CT alone was sufficient to establish the DGC at the sarcolemma. Additional studies suggest that R1-3 and CT also bind to the sarcolemma in the heart, though relatively weak. Taken together, our study provides the first conclusive in vivo evidence that dystrophin contains multiple independent membrane-binding domains. These structurally and functionally distinctive membrane-binding domains provide a molecular framework for dystrophin to function as a shock absorber and signaling hub. Our results not only shed critical light on dystrophin biology and DMD pathogenesis, but also provide a foundation for rationally engineering minimized dystrophins for DMD gene therapy.
authors.affiliation: Department of Molecular Microbiology and Immunology, School of Medicine.
authors.forename: Junling
authors.initials: J
authors.lastname: Zhao
authors.affiliation: Department of Molecular Microbiology and Immunology, School of Medicine.
authors.forename: Kasun
authors.initials: K
authors.lastname: Kodippili
authors.affiliation: Department of Molecular Microbiology and Immunology, School of Medicine.
authors.forename: Yongping
authors.initials: Y
authors.lastname: Yue
authors.affiliation: Department of Molecular Microbiology and Immunology, School of Medicine.|National Center for Advancing Translational Sciences, NIH, Rockville, MD, USA.
authors.forename: Chady H
authors.initials: CH
authors.lastname: Hakim
authors.affiliation: Department of Molecular Microbiology and Immunology, School of Medicine.
authors.forename: Lakmini
authors.initials: L
authors.lastname: Wasala
authors.affiliation: Department of Molecular Microbiology and Immunology, School of Medicine.
authors.forename: Xiufang
authors.initials: X
authors.lastname: Pan
authors.affiliation: Department of Molecular Microbiology and Immunology, School of Medicine.
authors.forename: Keqing
authors.initials: K
authors.lastname: Zhang
authors.affiliation: National Center for Advancing Translational Sciences, NIH, Rockville, MD, USA.
authors.forename: Nora N
authors.initials: NN
authors.lastname: Yang
authors.affiliation: Department of Molecular Microbiology and Immunology, School of Medicine duand@health.missouri.edu laiy@health.missouri.edu.|Department of Neurology, School of Medicine.|Department of Bioengineering.|Department of Biomedical Sciences, College of Veterinary Medicine, University of Missouri, Columbia, MO, USA.
authors.forename: Dongsheng
authors.initials: D
authors.lastname: Duan
authors.affiliation: Department of Molecular Microbiology and Immunology, School of Medicine duand@health.missouri.edu laiy@health.missouri.edu.
authors.forename: Yi
authors.initials: Y
authors.lastname: Lai
mesh_terms: D000818:Animals; D001665:Binding Sites; D017124:Conserved Sequence; D003600:Cytosol / Q000378:metabolism; D004285:Dogs; D016189:Dystrophin / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D006023:Glycoproteins / Q000378:metabolism*; D006801:Humans; D051379:Mice; D018101:Mice, Inbred mdx; D009137:Muscular Dystrophy, Animal / Q000378:metabolism*; D009206:Myocardium / Q000378:metabolism*; D000072417:Protein Domains; D012508:Sarcolemma / Q000378:metabolism
chemical_list: C484258:DMD protein, human; D016189:Dystrophin; D006023:Glycoproteins