DISTRIBUTION OF MU-CALPAIN PROENZYME IN THE BRAIN AND OTHER NEURAL TISSUES IN THE RAT

We raised antibodies against the acetyl N-terminal peptide of the huma n mu-calpain 80 kDa (80 K) subunit (N-acetyl SEEIITPVYCT-GVSAQVQKQRARE LG) in the rabbit. A specific antibody was purified using N-acetyl SEE IITPVYCTGVSAQVQKQ peptide-conjugated Sepharose 4B as an affinity gel s upport. Epitope analysis revealed that the purified antibody reacted o nly with the mu-calpain N-terminal peptides containing N-acetyl SEEIIT structure but no reactions occurred with other analogous peptides. We stern blot analysis showed that the antibody reacted with both human a nd rat- mu-calpain proenzymes but not with the activated calpains lack ing N-terminal peptide. Using this antibody we investigated immunohist ochemically the distribution of mu-calpain proenzyme in central and pe ripheral nervous systems as well as other non-neural tissues in the ra t. The proenzyme was detected mainly in neurons both in the central an d peripheral nervous tissues, but not in non-neural tissues except for red blood cells. Immunoreaction was stronger in the perikarya and/or in the nuclei than in the cytoplasm. Specificity of the antibody was v erified by an absorption test. In summary, the mu-calpain proenzyme is mainly distributed in the perikarya and/or nuclei of neurons. Our pre sent antibody specific to the N-terminus of the mu-calpain 80 K subuni t could serve as a useful tool to detect various functions of mu-calpa in as well as the damage in neurons caused by the enzyme.