Critical role of increased PTEN nuclear translocation in excitotoxic and ischemic neuronal injuries.

Stroke is the leading cause of disability in developed countries. However, no treatment is available beyond 3 h post-ictus. Here, we report that nuclear translocation of PTEN (phosphatase and tensin homolog deleted on chromosome TEN) is a delayed step causatively leading to excitotoxic (in vitro) and ischemic (in vivo) neuronal injuries. We found that excitotoxic stimulation of N-methyl-d-aspartate (NMDA) resulted in PTEN nuclear translocation in cultured neurons, a process requiring mono-ubiquitination at the lysine 13 residue (K13), as the translocation was prevented by mutation of K13 or a short interfering peptide (Tat-K13) that flanks the K13 residue. More importantly, using a rat model of focal ischemia, we demonstrated that systemic application of Tat-K13, even 6 h after stroke, not only reduced ischemia-induced PTEN nuclear translocation, but also strongly protected against ischemic brain damage. Our study suggests that inhibition of PTEN nuclear translocation may represent a novel after stroke therapy.