J Biol Chem. 2003 Sep 15 [Epub ahead of print].
Suen KC, Yu MS, So KF, Chang RC, Hugon J.
Department of Anatomy, The University of Hong Kong, Faculty of Medicine, Hong Kong, Hong Kong.
One of the hallmarks of Alzheimers disease (AD) is extracellular accumulation of senile plaques composed of aggregated beta-amyloid (Abeta) peptide. Treatment of cultured neurons with Abeta peptide induces neuronal death in which apoptosis is suggested to be one of the mechanisms. We have previously demonstrated that Abeta peptide induces activation of a double-stranded RNA-dependent serine/threonine protein kinase (PKR) and phosphorylation of eukaryotic initiation factor 2 alpha (eIF2alpha) in neurons in vitro.
Degenerating neurons in brain tissues from AD patients also displayed high immunoreactivity for phosphorylated PKR and eIF2alpha. Our previous data have also indicated that PKR plays a significant role in mediating Abeta peptide-induced neuronal death. Therefore, it is important to understand how PKR is activated by Abeta peptide. We report here that inhibition of caspase-3 activity reduces phosphorylation of PKR in neurons exposed to Abeta peptide and to a certain extent, cleavage of PKR and eIF2alpha, calcium release from the ER and activation of caspase-8 are the upstream signals modulating the caspase-3-mediated activation of PKR by Abeta peptide.
While in other systems HSP90 serves as a repressor for PKR, it is unlikely the candidate for caspase-3 to affect PKR activation after Abeta peptide exposure. Elucidation of the upstream pathways for PKR activation can help us to understand how this kinase participates in Abeta peptide neurotoxicity and to develop effective neuroprotective strategy.
PMID: 12975376 [PubMed – as supplied by publisher]