Synemin May Function to Directly Link Muscle Cell Intermediate Filaments to Both Myofibrillar Z-lines and Costameres

• Published in: The Journal of biological chemistry Vol. 276; no. 34; pp. 32330 - 32337
• Main Authors: Bellin, R M, Huiatt, T W, Critchley, D R, Robson, R M
• Format: Journal Article
• Language: English
• Published: United States American Society for Biochemistry and Molecular Biology 24.08.2001
• Subjects: Animals; Birds; Blotting, Western; Intermediate Filament Proteins; Muscle Proteins - metabolism; Muscle Proteins - physiology; Muscle, Skeletal - metabolism; Muscle, Skeletal - physiology; Myofibrils - metabolism; Myofibrils - physiology; Two-Hybrid System Techniques; Vinculin - metabolism
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M104005200

Synemin is a large intermediate filament (IF) protein that has been identified in all types of muscle cells in association with desmin- and/or vimentin-containing IFs. Our previous studies (Bellin, R. M., Sernett, S. W., Becker, B., Ip, W., Huiatt, T. W., and Robson, R. M. (1999) J. Biol. Chem. 274, 29493–29499) demonstrated that synemin forms heteropolymeric IFs with major IF proteins and contains a binding site for the myofibrillar Z-line protein α-actinin. By utilizing blot overlay assays, we show herein that synemin also interacts with the costameric protein vinculin. Furthermore, extensive assays utilizing the Gal4 yeast two-hybrid system demonstrate interactions of synemin with desmin and vimentin and additionally define more precisely the protein subdomains involved in the synemin/α-actinin and synemin/vinculin interactions. The C-terminal ∼300-amino acid region of synemin binds to the N-terminal head and central rod domains of α-actinin and the ∼150-amino acid C-terminal tail of vinculin. Overall, these interactions indicate that synemin may anchor IFs to myofibrillar Z-lines via interactions with α-actinin and to costameres at the sarcolemma via interactions with vinculin and/or α-actinin. These linkages would enable the IFs to directly link all cellular myofibrils and to anchor the peripheral layer of myofibrils to the costameres.