Talk abstracts

Talk on Monday 03:15-03:30pm submitted by Eric Johnson

Proteomic analysis of the dystrophin-associated protein complex reveals differences between cardiac and skeletal muscle: implications for muscular dystrophies.

Eric K. Johnson (Ohio State Biochemistry Program, The Ohio State University), Liwen Zhang (Center for Biomedical EPR Spectroscopy and Imaging, The Ohio State University), Alistair Phillips (Department of Cardiothoracic Surgery, Nationwide Childrens Hospital), Marvin E. Adams, Stanley C. Froehner (Department of Physiology & Biophysics, University of Washington), Kari Green-Church (Center for Biomedical EPR Spectroscopy and Imaging, The Ohio State University), Federica Montanaro (Department of Pediatrics, The Ohio State University)

Abstract:
Dystrophin is a large cytoskeletal protein that localizes to the inner surface of the membrane of skeletal muscle fibers and cardiomyocytes. It is the central organizer of the dystrophin-associated protein complex (DAPC) that functions as a signaling complex and as a structural stabilizer of the striated muscle membrane.

Mutations in dystrophin result in skeletal muscle degeneration and cardiomyopathy leading to early mortality due to respiratory or heart failure. However, there is no correlation in the severity, age of onset, or progression of disease between skeletal and cardiac muscles. This suggests that the DAPC may differ in composition and therefore function between these two striated muscles. This is further supported by gene therapy studies utilizing micro and mini dystrophin constructs that fully rescue skeletal muscle function yet appear to lack domains required to fully restore cardiac function. Therefore, the identification of differences in DAPC composition between cardiac and skeletal muscle is highly relevant to our understanding of the molecular mechanisms that underlie heart failure and the development of effective therapeutics for muscular dystrophies.

To this end, we preformed a comprehensive comparison of all known members of the DAPC between cardiac and skeletal muscle. Because of its complexity, we chose to purify the DAPC from tissues by immunoprecipitation and subsequently identify all DAPC members simultaneously by Shotgun Proteomics. This approach revealed novel differences between mouse cardiac and skeletal muscle that primarily involve DAPC proteins known to mediate intracellular signaling. DAPC members unique to the mouse heart were confirmed in human cardiac biopsy samples, indicating conservation of cardiac-specific functions of dystrophin in the human. These differences could underlie the reported discrepancies in clinical presentation and response to treatment between cardiac and skeletal muscle.

Keywords: Proteomics, Dystrophy, Cardiomyopathy