Synemin

Synemin also knowns as desmuslin is a is_associated_with::protein that in humans is encoded by the SYNM is_associated_with::gene. Synemin is an is_associated_with::intermediate filament (IF) family member. IF proteins are is_associated_with::cytoskeletal proteins that confer resistance to mechanical stress and are encoded by a dispersed multigene family. This protein has been found to form a linkage between is_associated_with::desmin, which is a subunit of the IF network, and the is_associated_with::extracellular matrix, and provides an important structural support in muscle.

Function
Synemin is an is_associated_with::intermediate filament (IF) and, like other IFs, primarily functions to integrate mechanical stress and maintain structural integrity in eukaryotic cells. While it has been observed in a variety of cell types, it has been best studied in the is_associated_with::sarcomere of skeletal myocytes. It localizes at the Z-disk and has been shown to bind to α-dystrobrevin, is_associated_with::α-actinin, and is_associated_with::desmin to act as a mechanical linker in transmitting is_associated_with::force laterally throughout the tissue, especially between the contractile is_associated_with::myofibrils and extracellular matrix.

Properties
Synemin has properties very similar to the intermediate filament is_associated_with::syncoilin. In particular, it binds to α-dystrobrevin in the is_associated_with::dystrophin-associated protein complex to act as a mechanical "linker" between the myofibrillar network and the cell membrane.

Splice variants
Two is_associated_with::splice variant isoforms of synemin exist, α and β. Both isoforms have a very short N-terminal domain of 10 amino acids and a long C-terminal domain consisting of 1243 amino acids for the α isoform and 931 amino acids for the β isoform. An is_associated_with::intronic sequence of the synemin β isoform is used as a coding sequence for synemin α.

History
The origin of the synemin/desmuslin naming convention is quite complex. In 1980, synemin was first identified in avian is_associated_with::smooth muscle and was initially described as an IF-associated protein due to its colocalization and copurification with is_associated_with::desmin and is_associated_with::vimentin. Subsequent to the is_associated_with::cloning of chicken synemin, Mizuno and colleagues reported the cloning of a novel IF protein, human desmuslin, as an α-dystrobrevin-interacting protein. Sequence analysis showed that human desmuslin was 32% identical and 11% similar to the is_associated_with::amino acid sequence of chicken synemin, while the IF proteins is_associated_with::vimentin and is_associated_with::desmin are more than 80% identical across the same species. Although several parts were very similar between human desmuslin and chicken synemin, the low degree of conservation between these two proteins compared to other cloned IF proteins suggested that synemin was not the human desmuslin orthologue. In addition, unlike chicken synemin, in vitro is_associated_with::coimmunoprecipitation assays could not detect an interaction between human desmuslin and α-actinin. In 2001, Titeux and colleagues reported the cloning of the α and β splice-varying isoforms of human synemin and showed that β-synemin was identical to desmuslin.