Regulation of integrin α5β1 affinity during myogenic differentiation

Abstract

The antigen recognized by U1α, a monoclonal antibody to the α chain of a chicken integrin fibronectin receptor, was identified as α5. It identifies the same polypeptide as antisera raised to a sequence from the α5 cytoplasmic domain. The U1α antibody has the unusual functional property for α chain antibodies of enhancing the binding of α5β1 for its ligand fibronectin. U1α was used to examine the function of α5β1 during myogenic differentiation. As myogenic cells differentiated from replicating myoblasts to bipolar myocytes there was a decrease in their adhesion to the substrate caused by inactivation of α5β1, which could be reversed by treatment of the cells with U1α. The U1α induced increased adhesion to fibronectin but did not inhibit the differentiation process as measured by formation of myotubes. However, U1α did interfere with both cell migration and morphogenesis of myotubes. The resulting myotubes were smaller, more branched, and showed less regular alignment of nuclei. The results suggest that the ability of the cell to regulate α5β1 affinity is critical to myogenic morphogenesis. © 1995 by Academic Press, Inc.