THE ALPHA-7-BETA-1 INTEGRIN MEDIATES ADHESION AND MIGRATION OF SKELETAL MYOBLASTS ON LAMININ

Many aspects of myogenesis are believed to be regulated by myoblast in teractions with specific components of the extracellular matrix. For e xample, laminin has been found to promote adhesion, migration, and pro liferation of mammalian myoblasts. Based on affinity chromatography, t he alpha 7 beta 1 integrin has been presumed to be the major receptor mediating myoblast interactions with laminin. We have prepared a monoc lonal antibody, O26, that specifically reacts with both the X1 and the X2 extracellular splice variants of the alpha 7 integrin chain. This antibody completely and selectively blocks adhesion and migration of r at L8E63 myoblasts on laminin-1, but not on fibronectin. In contrast, a polyclonal antibody to the fibronectin receptor, alpha 5 beta 1 inte grin, blocks myoblast adhesion on fibronectin, but not on laminin-1. T he alpha 7 beta 1 integrin also binds to a mixture of laminin-2 and la minin-4, the major laminin isoforms in developing and adult skeletal m uscle, but O26 is a much less potent inhibitor of myoblast adhesion on the laminin-2/4 mixture than on laminin-1, Based on affinity chromato graphy, we suggest that this may be due to higher affinity binding of alpha 7X1 to laminin-2/4 than to laminin-1. (C) 1997 Academic Press.