Assembly of the FKBP51–PHLPP2–AKT signaling complex in cerebral ischemia/reperfusion injury in rats

• IR injury induced assembly of FKBP51–PHLPP2–AKT signaling complex.
• PHLPP2 inhibition reduced the assembly of FKBP51–PHLPP–AKT signaling complex.
• PHLPP2 inhibition increased AKT phosphorylation after IR injury.
• PHLPP2 inhibition decreased JNKs phosphorylation after IR injury.
• PHLPP2 inhibition prevented against neuronal death after IR injury.

The imbalance of cell pro-death and pro-survival signaling pathways determines the neuronal fate during cerebral ischemia/reperfusion (I/R) injury. However, the biological mechanisms regulating the balance between activation of the pro-death or the pro-survival signaling pathways remain unclear. In this study, a rat model of I/R injury was established using four-vessel occlusion followed by different times of reperfusion. I/R injury did not affect the level of FK506 binding protein 51 (FKBP51), PH domain and leucine rich repeat protein phosphatases (PHLPP)-2, and AKT, but induced assembly of the FKBP51-PHLPP2-AKT signaling complex, as indicated by the enhancement of interactions among these compounds following reperfusion. Using an antisense oligonucleotide, PHLPP2 expression was effectively inhibited. Critically, the inhibition of PHLPP2 prohibited the interactions of FKBP51, PHLPP2 and AKT, reversed the decrease of p-AKT expression and increased the expression of p-JNKs and p-c-Jun elicited by I/R injury. In addition, PHLPP2 inhibition reversed I/R-injury-induced Caspase-3 cleavage and loss of pyramid neurons in the CA1 region of hippocampus. The results of the current study indicate that the assembly of the FKBP51-PHLPP2-AKT signaling complex plays a critical role in mediating cell death in I/R injury. The inhibition of PHLPP2 via antisense oligonucleotide treatment may be an effective method to prohibit the assembly of the FKBP51–PHLPP–AKT signaling complex, thus balancing the cell pro-survival and pro-death signaling pathways ultimately mitigating cell death in I/R injury.