F-actin cross-linking protein which is thought to anchor actin to a variety of intracellular structures. This is a bundling protein. Homodimer; antiparallel. Interacts with Smn; the interaction occurs in adult thoracic tissues. Colocalizes with Smn at the Z-line of indirect flight muscles. Experimental confirmation may be lacking for some isoforms. Larval muscle isoform is expressed in the larval body wall, adult muscles of the head and abdomen and supercontractile muscles of the larva and adult. Adult muscle isoform accumulates within adult fibrillar and tubular muscles. Larval muscle isoform is found in the larvae and adults, the adult muscle isoform in adults only. Belongs to the alpha-actinin family.