Has an actin-binding and actin-bundling activity. Can induce the formation of F-actin networks in an isoform-specific manner. At the sarcomeric Z lines is proposed to act as adapter protein that links nascent myofibers to the sarcolemma via ZYX and may play a role in early assembly and stabilization of the Z lines. Involved in autophagosome formation. May play a role in chaperone-assisted selective autophagy (CASA) involved in Z lines maintenance in striated muscle under mechanical tension; may link the client-processing CASA chaperone machinery to a membrane-tethering and fusion complex providing autophagosome membranes. Involved in regulation of cell migration. May be a tumor suppressor.; [Isoform 1]: Involved in regulation of cell migration. Can induce formation of thick, irregular actin bundles in the cell body.; [Isoform 2]: Involved in regulation of cell migration. Can induce long, well-organized actin bundles frequently orientated in parallel along the long axis of the cell showing characteristics of contractile ventral stress fibers.; [Isoform 3]: Involved in regulation of cell migration. Can induce an amorphous actin meshwork throughout the cell body containing a mixture of long and short, randomly organized thick and thin actin bundles.; [Isoform 4]: Can induce long, well-organized actin bundles frequently orientated in parallel along the long axis of the cell showing characteristics of contractile ventral stress fibers.; [Isoform 5]: Involved in regulation of cell migration in part dependent on the Rho-ROCK cascade; can promote formation of nascent focal adhesions, actin bundles at the leading cell edge and lamellipodia. Can induce formation of thick, irregular actin bundles in the cell body; the induced actin network is associated with enhanced cell migration in vitro.