title: Dystrophins carrying spectrin-like repeats 16 and 17 anchor nNOS to the sarcolemma and enhance exercise performance in a mouse model of muscular dystrophy.
abstract: Sarcolemma-associated neuronal NOS (nNOS) plays a critical role in normal muscle physiology. In Duchenne muscular dystrophy (DMD), the loss of sarcolemmal nNOS leads to functional ischemia and muscle damage; however, the mechanism of nNOS subcellular localization remains incompletely understood. According to the prevailing model, nNOS is recruited to the sarcolemma by syntrophin, and in DMD this localization is altered. Intriguingly, the presence of syntrophin on the membrane does not always restore sarcolemmal nNOS. Thus, we wished to determine whether dystrophin functions in subcellular localization of nNOS and which regions may be necessary. Using in vivo transfection of dystrophin deletion constructs, we show that sarcolemmal targeting of nNOS was dependent on the spectrin-like repeats 16 and 17 (R16/17) within the rod domain. Treatment of mdx mice (a DMD model) with R16/17-containing synthetic dystrophin genes effectively ameliorated histological muscle pathology and improved muscle strength as well as exercise performance. Furthermore, sarcolemma-targeted nNOS attenuated alpha-adrenergic vasoconstriction in contracting muscle and improved muscle perfusion during exercise as measured by Doppler and microsphere circulation. In summary, we have identified the dystrophin spectrin-like repeats 16 and 17 as a novel scaffold for nNOS sarcolemmal targeting. These data suggest that muscular dystrophy gene therapies based on R16/17-containing dystrophins may yield better clinical outcomes than the current therapies.
authors.affiliation: Department of Molecular Microbiology and Immunology, University of Missouri, One Hospital Drive, Columbia, MO 65212, USA.
authors.forename: Yi
authors.initials: Y
authors.lastname: Lai
authors.forename: Gail D
authors.initials: GD
authors.lastname: Thomas
authors.forename: Yongping
authors.initials: Y
authors.lastname: Yue
authors.forename: Hsiao T
authors.initials: HT
authors.lastname: Yang
authors.forename: Dejia
authors.initials: D
authors.lastname: Li
authors.forename: Chun
authors.initials: C
authors.lastname: Long
authors.forename: Luke
authors.initials: L
authors.lastname: Judge
authors.forename: Brian
authors.initials: B
authors.lastname: Bostick
authors.forename: Jeffrey S
authors.initials: JS
authors.lastname: Chamberlain
authors.forename: Ronald L
authors.initials: RL
authors.lastname: Terjung
authors.forename: Dongsheng
authors.initials: D
authors.lastname: Duan
mesh_terms: D000818:Animals; D001665:Binding Sites; D016189:Dystrophin / Q000378:metabolism; D006801:Humans; D051379:Mice; D018101:Mice, Inbred mdx; D009119:Muscle Contraction; D009137:Muscular Dystrophy, Animal / Q000201:enzymology / Q000503:physiopathology*; D020388:Muscular Dystrophy, Duchenne / Q000201:enzymology / Q000503:physiopathology*; D009569:Nitric Oxide / Q000502:physiology*; D052248:Nitric Oxide Synthase Type I / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D010805:Physical Conditioning, Animal; D012508:Sarcolemma / Q000201:enzymology; D013049:Spectrin / Q000235:genetics; D014661:Vasoconstriction
chemical_list: D016189:Dystrophin; D013049:Spectrin; D009569:Nitric Oxide; D052248:Nitric Oxide Synthase Type I