T. Hayashi et al., Phosphorylation of retinoblastoma protein in rat brain after transient middle cerebral artery occlusion, NEUROP AP N, 26(4), 2000, pp. 390-397
Although mature neurones do not replicate genomic DNA, some cell cycle-rela
ted kinases are aberrantly activated in neurones after ischaemia. As hyperp
hosphorylation of retinoblastoma (Rb) protein is the common pathway in mito
tic signal cascade, this study investigated the phosphorylation state of th
e Rb protein as well as its mRNA level in rat brain after transient middle
cerebral artery (MCA) occlusion. Immunohistochemical analysis revealed that
neurones in the sham-operated brain expressed Rb protein without the hyper
phosphorylated form. Immunoreactivity for the hyperphosphorylated form of R
b protein progressively increased from 1 h to 3 days after ischaemia in neu
rones in the MCA territory. Western blot analysis demonstrated similar chan
ge. However, reverse transcription-polymerase chain reaction study revealed
that Rb showed no definite change at the mRNA level. These results suggest
that Rb protein is progressively hyperphosphorylated in the brain after is
chaemia, which may activate apoptotic mechanisms in neuronal cells of the b
rain after ischaemia.