Sarcomeric Alpha Actinin belongs to the spectrin superfamily, which includes spectrin, dystrophin, and their homologues and isoforms. It forms an anti-parallel rod-shaped dimer with one actin-binding domain at each end, bundling actin filaments in various cell types and cytoskeleton frameworks. In striated, cardiac, and smooth muscle cells, Sarcomeric Alpha Actinin is localized at the Z-disk and analogous dense bodies, where it forms a lattice-like structure and stabilizes the muscle contractile apparatus. Alpha Actinin functions as an actin crosslinker in muscle cells, anchoring actin filaments at the Z lines in striated muscles and dense bodies in smooth muscle cells. It plays a role in muscle contraction by interacting with the contractile machinery. In non-muscle cells, Sarcomeric Alpha Actinin is found along actin filaments and in adhesion sites, where it contributes to the organization of the cytoskeleton and cell adhesion. Sarcomeric Alpha Actinin is also implicated in autoimmune diseases, particularly systemic lupus erythematosus and autoimmune hepatitis, where it may serve as a target autoantigen.
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