Integrin α3 subunit participates in myoblast adhesion and fusion in vitro

Satellite cells are myogenic precursor cells, participating in growth, and regeneration of skeletal muscles. The proteins that play a role in myogenesis are integrins. In this report, we show that the integrin alpha 3 subunit is expressed in quiescent satellite cells and activated myoblasts. We also find that in myoblasts the integrin alpha 3 subunit is localized at cell-cell and cell-extracellular matrix contacts. We notice that increase in protein and mRNA encoding the integrin alpha 3 subunit accompanies myoblast differentiation. Using double immunofluorescence and immunoprecipitation experiments, we demonstrate that the integrin alpha 3 subunit co-localizes with actin, and binds the integrin beta 1 subunit and ADAM12, suggesting that the complex alpha 3 beta 1/ADAM12 is probably involved in myoblast fusion. Importantly, overexpression of the full-length integrin alpha 3 subunit increases myoblast fusion whereas an antibody against its extracellular domain inhibits fusion. These data demonstrate that the integrin alpha 3 subunit may contribute to satellite cell activation and then myoblast adhesion and fusion.