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M. Joe, H.-S. Kwon, S. Sohn, C. Kee, S. Tomarev; Identification and Characterization of Alpha-Syntrophin as a Novel Myocilin-Binding Protein. Invest. Ophthalmol. Vis. Sci. 2008;49(13):3813.
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MYOC, a causative gene for open-angle glaucoma, encodes a secreted glycoprotein of unknown function named myocilin. To elucidate possible function of myocilin, we studied its interaction with other proteins.
Human skeletal muscle cDNA library was used in yeast two-hybrid screen with myocilin with its signal sequence deleted as a bait. Results obtained in a yeast two-hybrid screen were confirmed by co-immunoprecipitation experiments using lysates of NIH 3T3 cell transiently transfected with myocilin constructs. Immunocytochemistry was used to determine the cellular localization of myocilin and alpha-syntrophin.
Yeast two-hybrid screen identified alpha-syntrophin as a protein interacting with myocilin, with the N-terminal part of myocilin being critical for this interaction. Since alpha-syntrophin was detected in NIH3T3 cells using antibodies against alpha-syntrophin, these cell were transiently transfected with different myocilin constructs and used in co-immunoprecipitation experiments. Full-length myocilin and the N-terminal part but not the C-terminal part of myocilin were co-immunoprecipitated with alpha-syntrophin. Expression of the full length and N-terminus myocilin dramatically increased the level of intracellular alpha-syntrophin. Expression of myocilin in NIH 3T3 cells led to re-distribution of alpha-syntrophin from plasma membrane to cytoplasm as shown by fluorescence microscopy.
.These findings indicate that alpha-syntrophin, a member of the dystrophin glycoprotein complex, is a binding partner of myocilin. Myocilin may have a role in the function of the dystrophin glycoprotein complex by regulating the stability and localization of alpha-syntrophin. Further studies of myocilin and alpha-syntrophin interaction may provide important clues of myocilin functions.
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