PTEN S-nitrosylation correlates with protein degradation. (A) Effects of various neurotoxins on the steady-state protein level of PTEN 4 h after treatments. N = 6 experiments. (B) Cycloheximide-chase experiment on PTEN stability. PRCN cells were incubated with 50 μg/ml cycloheximide (CHX) for the indicated times in the presence or absence of glutamate (200 μM). Cells were simultaneously treated with glutamate and cycloheximide. Two groups of neurons were also co-treated with glutamate and 25 μM MG132. Cells lysates were then prepared for Western blot analysis of steady-state levels of PTEN. (C) Glutamate-induced reduction of PTEN can be rescued by l-NMMA (1 mM) and MG132 (25 μM) pretreatment for 5 and 1 h, respectively, as examined by three independent experiments.