Differential targeting of nNOS and AQP4 to dystrophin-deficient sarcolemma by membrane-directed alpha-dystrobrevin.
alpha-Dystrobrevin associates with and is a homologue of dystrophin, the protein linked to Duchenne and Becker muscular dystrophies. We used a transgenic approach to restore alpha-dystrobrevin to the sarcolemma in mice that lack dystrophin (mdx mice) to study two interrelated functions: (1) the ability of alpha-dystrobrevin to rescue components of the dystrophin complex in the absence of dystrophin and (2) the ability of sarcolemmal alpha-dystrobrevin to ameliorate the dystrophic phenotype. We generated transgenic mice expressing alpha-dystrobrevin-2a linked to a palmitoylation signal sequence and bred them onto the alpha-dystrobrevin-null and mdx backgrounds. Expression of palmitoylated alpha-dystrobrevin prevented the muscular dystrophy observed in the alpha-dystrobrevin-null mice, demonstrating that the altered form of alpha-dystrobrevin was functional. On the mdx background, the palmitoylated form of alpha-dystrobrevin was expressed on the sarcolemma but did not significantly ameliorate the muscular dystrophy phenotype. Palmitoylated dystrobrevin restored alpha-syntrophin and aquaporin-4 (AQP4) to the mdx sarcolemma but was unable to recruit beta-dystroglycan or the sarcoglycans. Despite restoration of sarcolemmal alpha-syntrophin, neuronal nitric oxide synthase (nNOS) was not localized to the sarcolemma, suggesting that nNOS requires both dystrophin and alpha-syntrophin for correct localization. Thus, although nNOS and AQP4 both require interaction with the PDZ domain of alpha-syntrophin for sarcolemmal association, their localization is regulated differentially.
Department of Physiology and Biophysics, University of Washington, Seattle, WA 98195, USA. Marva@u.washington.edu
Marvin E
ME
Adams
Yan
Y
Tesch
Justin M
JM
Percival
Douglas E
DE
Albrecht
Jay I
JI
Conhaim
Kendra
K
Anderson
Stanley C
SC
Froehner
D000818:Animals; D051401:Aquaporin 4 / Q000235:genetics*; D016189:Dystrophin / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D049029:Dystrophin-Associated Proteins / Q000235:genetics* / Q000378:metabolism; D054878:Lipoylation; D051379:Mice; D018101:Mice, Inbred mdx; D018345:Mice, Knockout; D008822:Mice, Transgenic; D008856:Microscopy, Fluorescence; D009132:Muscles / Q000378:metabolism / Q000473:pathology; D009137:Muscular Dystrophy, Animal / Q000235:genetics / Q000473:pathology; D009479:Neuropeptides / Q000235:genetics* / Q000378:metabolism; D052248:Nitric Oxide Synthase Type I / Q000235:genetics* / Q000378:metabolism; D054731:PDZ Domains; D011485:Protein Binding; D012508:Sarcolemma / Q000737:chemistry / Q000378:metabolism*
C496031:Aqp4 protein, mouse; D051401:Aquaporin 4; C098884:Dtna protein, mouse; D016189:Dystrophin; D049029:Dystrophin-Associated Proteins; D009479:Neuropeptides; C091824:syntrophin; D052248:Nitric Oxide Synthase Type I; C496321:Nos1 protein, mouse