Preconditioning-Activated AKT Controls Neuronal Tolerance to Ischemia through the MDM2-p53 Pathway.

Emilia Barrio,Juan P Bolaños,Angeles Almeida,Cristina Rodríguez,Irene Sánchez-Morán,Rebeca Vecino,Maria Delgado-Esteban,Alberto Suárez-Pindado

doi:10.3390/ijms22147275

Abstract

One of the most important mechanisms of preconditioning-mediated neuroprotection is the attenuation of cell apoptosis, inducing brain tolerance after a subsequent injurious ischemia. In this context, the antiapoptotic PI3K/AKT signaling pathway plays a key role by regulating cell differentiation and survival. Active AKT is known to increase the expression of murine double minute-2 (MDM2), an E3-ubiquitin ligase that destabilizes p53 to promote the survival of cancer cells. In neurons, we recently showed that the MDM2–p53 interaction is potentiated by pharmacological preconditioning, based on subtoxic stimulation of NMDA glutamate receptor, which prevents ischemia-induced neuronal apoptosis. However, whether this mechanism contributes to the neuronal tolerance during ischemic preconditioning (IPC) is unknown. Here, we show that IPC induced PI3K-mediated phosphorylation of AKT at Ser473, which in turn phosphorylated MDM2 at Ser166. This phosphorylation triggered the nuclear stabilization of MDM2, leading to p53 destabilization, thus preventing neuronal apoptosis upon an ischemic insult. Inhibition of the PI3K/AKT pathway with wortmannin or by AKT silencing induced the accumulation of cytosolic MDM2, abrogating IPC-induced neuroprotection. Thus, IPC enhances the activation of PI3K/AKT signaling pathway and promotes neuronal tolerance by controlling the MDM2–p53 interaction. Our findings provide a new mechanistic pathway involved in IPC-induced neuroprotection via modulation of AKT signaling, suggesting that AKT is a potential therapeutic target against ischemic injury.

Highlights

In humans, the existence of transient ischemic attack (TIA) has been revealed as an endogenous preconditioned state with benefits of functional outcome in stroke patients [1,2,3]
We previously described the impact of murine double minute-2 (MDM2)–p53 interaction on neuronal susceptibility to ischemia [34] and ischemic tolerance (IT) [33]
We explored the potential role of AKT on ischemic preconditioning (IPC)-mediated neuroprotection as a candidate to be involved in the MDM2–p53 pathway

Summary

Introduction

The existence of transient ischemic attack (TIA) has been revealed as an endogenous preconditioned state with benefits of functional outcome in stroke patients [1,2,3]. Evidence shows that IPC-promoted neuroprotection depends on transcription, translation, and post-translational mechanisms, which alters the function of key proteins after ischemia [6,7,8,9,10,11]. In the last two decades, apoptotic neuronal cell death has positioned itself as an essential mechanism involved in cerebral ischemic injury [14,15,16]. In this sense, protein kinase B or AKT, a serine/threonine kinase that requires a functional phosphoinositide kinase (PI3K) to be activated, has been considered as an essential target for neuroprotective therapies after ischemia [17,18]. AKT activation may contribute to the induction of IT in the brain [25], the exact mechanism involving its IPC-mediated activation remains elusive

Methods

Results

Conclusion