ISOLATION AND IDENTIFICATION OF A MU-CALPAIN-PROTEIN KINASE C-ALPHA COMPLEX IN SKELETAL-MUSCLE

A mu-calpain-PKC complex was isolated from rabbit skeletal muscle by u ltracentrifugation and by anion-exchange chromatography. The PKC assoc iated to mu-calpain was stimulated by calcium, phosphatidylserine and diacylglycerol, and corresponds to a conventional PKC (cPKC). This com plex presents an apparent molecular mass close to 190 kDa and is compo sed of one mu-calpain molecule and of one cPKC molecule. Using monoclo nal antibodies specific for the different cPKC isoforms, the isoenzyme associated to mu-calpain was identified as cPKC alpha. Immunofluoresc ence staining reveals a co-localization of mu-calpain and cPKC alpha o n the muscle fibre plasma membranes.