Proteolysis of ankyrin and Na+/K+-ATPase in postmortem rat brain: Is calpain involved?

Ankyrin links the fodrin-based cytoskeleton to membrane proteins such as Na+/K+-ATPase, thereby maintaining cellular integrity. Immunoblotting by antibody raised against erythrocyte ankyrin demonstrated the proteolysis of ankyrin, which was highly correlated with postmortem interval (0-24 h). Proteolysis in the postmortem brain generated the 160-kDa fragment with an identical size as the fragment formed after in vitro proteolysis by calpain. Although mu M Ca2+ induced the proteolysis in the homogenate, the presence of mu-calpain was not demonstrated by immunoblotting using the antibody that reacts with large subunits both of mu- and m-calpains. Na+/K+-ATPase was also proteolyzed in the postmortem brain. (C) 1997 Elsevier Science Ireland Ltd.