Ischemia-induced phosphorylation of initiation factor 2 in differentiated PC12 cells: role for initiation factor 2 phosphatase.

摘要: An in vitro model of ischemia was obtained by subjecting PC12 cells differentiated with nerve growth factor to a combination glucose deprivation plus anoxia. Immediately after the ischemic period, protein synthesis rate significantly inhibited (80%) and western blots cell extracts revealed significant accumulation phosphorylated eukaryotic initiation 2, alpha subunit, eIF2(alphaP) (42%). Upon recovery, levels returned control values 30 min, whereas still partially (33%) reached almost within 2 h. The activities mammalian eIF2alpha kinases, double-stranded RNA-activated kinase, GCN2 homologue, endoplasmic reticulum-resident were determined. None kinases studied showed increased activity as compared controls. Exposure cell-permeable inhibitors phosphatases 1 2A, calyculin A or tautomycin, induced dose- time-dependent eIF2(alphaP), mimicking an effect. Protein phosphatase activity, measured [(32)P]phosphorylase substrate, diminished during upon 30-min recovery. In addition, dephosphorylation lower cells, paralleling both greatest translational inhibition highest levels. endogenous from different sensitivity inhibitor fostriecin assays, inhibitor-2 effect being than cells. Together these results indicate that phosphatase, probably 1, is implicated ischemia-induced