Synemin may function to directly link muscle cell intermediate filaments to both myofibrillar Z-lines and costameres.
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 alpha-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/alpha-actinin and synemin/vinculin interactions. The C-terminal approximately 300-amino acid region of synemin binds to the N-terminal head and central rod domains of alpha-actinin and the approximately 150-amino acid C-terminal tail of vinculin. Overall, these interactions indicate that synemin may anchor IFs to myofibrillar Z-lines via interactions with alpha-actinin and to costameres at the sarcolemma via interactions with vinculin and/or alpha-actinin. These linkages would enable the IFs to directly link all cellular myofibrils and to anchor the peripheral layer of myofibrils to the costameres.
Bellin
R M
RM
Muscle Biology Group, Department of Biochemistry, Iowa State University, Ames, Iowa 50011-3260, USA.
Huiatt
T W
TW
Critchley
D R
DR
Robson
R M
RM
D000818:Animals; D001717:Birds; D015153:Blotting, Western; D007381:Intermediate Filament Proteins; D009124:Muscle Proteins / Q000378:metabolism / Q000502:physiology*; D018482:Muscle, Skeletal / Q000378:metabolism / Q000502:physiology; D009210:Myofibrils / Q000378:metabolism / Q000502:physiology*; D020798:Two-Hybrid System Techniques; D016596:Vinculin / Q000378:metabolism
D007381:Intermediate Filament Proteins; D009124:Muscle Proteins; C430456:desmuslin; D016596:Vinculin