The α7 Integrin as a Target Protein for Cell Surface Mono-ADP-Ribosylation in Muscle Cells

A membrane-associated arginine-specific mono-ADP-ribosyltransferase was purified 215,000-fold from rabbit skeletal muscle and its gene was isolated from a skeletal muscle cDNA library. The enzyme was a glycosylphosphatidyl-inositol-linked protein, present on the surface of differentiated skeletal muscle myoblasts (myotubes). Following incubation of cultured, intact myotubes with [adenylate-32P]NAD and analysis by SDS-PAGE, a major radiolabeled protein of 97/140 kDa (reduced/ nonreduced conditions) was observed. It was identified as integrin a 7 based on its size, binding to a laminin affinity column, immunoprecipitation with a monoclonal antibody, and partial amino acid sequencing.