[Degradation of cytoskeletal proteins in cerebral ischemia]

Degradation of neurofilament (NF) triplet proteins (Mw 200,000 (NF200), Mw 150,000 (NF150), Mw 68,000 (NF68], high molecular weight microtubule-associated proteins (MAP1 and MAP2) and other cytoskeletal proteins in rat brain during ischemia was investigated by sodium dodecyl sulfate (SDS)-gel electrophoresis and immunoblot methods using anti-NF200 monoclonal antibody. Selective degradation of NF200 and NF150 was observed during the initial 10 to 15 minutes of ischemia: and the degradation of MAP1 and MAP2 during the initial 15 to 30 minutes of ischemia. These degradations suggest that the activation of a protease occurs at the very early stage of cerebral ischemia, which are the earliest irreversible neuronal changes ever to be reported. Effect of ischemia on polymerization of microtubule proteins was also investigated by turbidity assay. A rapid decrease of the ability of polymerizing microtubules was observed during the initial 5 minutes of ischemia. This loss of polymerization ability was apparently independent of the degradation of MAP1 and MAP2.