α-Synemin localizes to the M-band of the sarcomere through interaction with the M10 region of titin.

α-Synemin contains a unique 312 amino acid insert near the end of its C-terminal tail. Therefore we set out to determine if the insert is a site of protein-protein interaction that regulates the sub-cellular localization of this large isoform of synemin. Yeast-two hybrid analysis indicated that this region is a binding site for the M10 region of titin. This was confirmed with GST pull-down assays. Co-immunoprecipitation of endogenous proteins indicated close association of the two proteins in vivo and immunostaining of cardiomyocytes demonstrated co-localization of the proteins at the M-band of the sarcomere.