Involved in skeletal muscle regeneration, specifically at the onset of cell fusion. Also involved in macrophage-derived giant cells (MGC) and osteoclast formation from mononuclear precursors. Binds 1 zinc ion per subunit. Interacts with alpha-actinin-2 and with syndecans. Interacts with SH3PXD2A. Interacts with FST3. Interacts with RACK1; the interaction is required for PKC-dependent translocation of ADAM12 to the cell membrane (By similarity). Expressed during early developing mesenchymal cells that give rise to skeletal muscle, bones and visceral organs. Not expressed in adult normal muscle but expressed in regenerating muscle. At the onset of myoblast fusion. The first 30 amino acids of the cytoplasmic domain contain a major binding site to alpha-actinin-2. This interaction is necessary to promote muscle cell fusion. The cysteine-rich domain supports cell adhesion through syndecans and triggers signaling events that lead to beta-1 integrin-dependent cell spreading. In carcinoma cells the binding of this domain to syndecans does not allow the integrin-mediated cell spreading (By similarity). The conserved cysteine present in the cysteine-switch motif binds the catalytic zinc ion, thus inhibiting the enzyme. The dissociation of the cysteine from the zinc ion upon the activation-peptide release activates the enzyme. The precursor is cleaved by a furin endopeptidase. Marker of skeletal muscle regeneration.