Preservation of GABA(A) Receptor Function by PTEN Inhibition Protects Against Neuronal Death in Ischemic Stroke

Division of Fundamental Neurobiology, Toronto Western Research Institute, University Health Network, Toronto, Canada.
Stroke (Impact Factor: 5.72). 04/2010; 41(5):1018-26. DOI: 10.1161/STROKEAHA.110.579011
Source: PubMed


Downregulation of the tumor suppressor, phosphatase and tensin homolog deleted on chromosome 10 (PTEN), is thought to be a novel neuroprotective strategy in ischemic stroke, but the underlying mechanisms remain unclear. In this study, we aimed to validate the use of PTEN regulation of gamma-aminobutyric acid subtype A receptors (GABA(A)Rs) as a molecular target for the treatment of ischemic stroke. Because suppression of GABA(A)Rs contributes to ischemic neuron death, describing the intracellular signaling that interacts with GABA(A)Rs in ischemic neurons would provide a molecular basis for novel stroke therapies.
We measured surface GABA(A)R expression by immunocytochemical labeling and surface protein biotinylation assay. Knockdown and overexpression approaches were used to test the effects of PTEN on the expression and function of GABA(A)Rs. Neuronal death was detected in both in vitro and in vivo stroke models.
The knockdown and overexpression approaches provided the first evidence that PTEN negatively regulated membrane expression and function of GABA(A)Rs in rat hippocampal neurons. Importantly, we demonstrated that a PTEN inhibitor prevented the reduction of surface GABA(A)Rs in injured hippocampal neurons subjected to oxygen-glucose deprivation, an in vitro insult that mimics ischemic injury, whereas a GABA(A)R antagonist significantly reduced this PTEN inhibitor-induced neuroprotection in both the in vitro and in vivo ischemic stroke models.
Our study provides direct evidence that downregulation of PTEN protects against ischemic neuron death by preserving GABA(A)R function. Targeting this pathway may be an effective strategy for development of selective, potent stroke treatments.

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    • "The γ-aminobutyric acid receptor subunit alpha-1 (GABAAR1 or GABRA1), which mediates post-synaptic transmission in the vertebrate CNS, presented an early down-regulation and late up-regulation with the onset of clinical signs. The differential expression of GABRA1 is associated with the modulation of the phosphatase and tensin homolog (PTEN), a synaptic signaling protein [67] and arrestin-b1 (ARRB1), both of which activate the PI3K pathway, leading to the regulation of GABRA1 membrane expression and function [68], [69]. ARRB1, NSF, PICK1 and GRIPAP1 were related to the endocytosis/recycling process of other neurotransmitter receptors (GPCRs or AMPARs) [56], [70], [71], [72]. "
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    ABSTRACT: Recent outbreaks of Chikungunya virus (CHIKV) infection have been characterized by an increasing number of severe cases with atypical manifestations including neurological complications. In parallel, the risk map of CHIKV outbreaks has expanded because of improved vector competence. These features make CHIKV infection a major public health concern that requires a better understanding of the underlying physiopathological processes for the development of antiviral strategies to protect individuals from severe disease. To decipher the mechanisms of CHIKV infection in the nervous system, a kinetic analysis on the host proteome modifications in the brain of CHIKV-infected mice sampled before and after the onset of clinical symptoms was performed. The combination of 2D-DIGE and iTRAQ proteomic approaches, followed by mass spectrometry protein identification revealed 177 significantly differentially expressed proteins. This kinetic analysis revealed a dramatic down-regulation of proteins before the appearance of the clinical symptoms followed by the increased expression of most of these proteins in the acute symptomatic phase. Bioinformatic analyses of the protein datasets enabled the identification of the major biological processes that were altered during the time course of CHIKV infection, such as integrin signaling and cytoskeleton dynamics, endosome machinery and receptor recycling related to virus transport and synapse function, regulation of gene expression, and the ubiquitin-proteasome pathway. These results reveal the putative mechanisms associated with severe CHIKV infection-mediated neurological disease and highlight the potential markers or targets that can be used to develop diagnostic and/or antiviral tools.
    PLoS ONE 03/2014; 9(3):e91397. DOI:10.1371/journal.pone.0091397 · 3.23 Impact Factor
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    • "It may be that cerebral ischemia/hypoxia represents a unique physiological context that accelerates PTEN-mediated signaling for cell survival (Ning et al., 2004). Nonetheless, our evidence demonstrating that Pten is not degraded in the cytoplasm but is imported into the nucleus for neuron survival presents a conceptual challenge to the existing dogma of promoting Pten inhibition for the treatment of stroke (Ning et al., 2004; Hong et al., 2006; Liu et al., 2010). Our findings also provide the first in vivo example of an acute stimulus that can regulate nuclear trafficking of Pten. "
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    ABSTRACT: PTEN (phosphatase and tensin homologue deleted on chromosome TEN) is the major negative regulator of phosphatidylinositol 3-kinase signaling and has cell-specific functions including tumor suppression. Nuclear localization of PTEN is vital for tumor suppression; however, outside of cancer, the molecular and physiological events driving PTEN nuclear entry are unknown. In this paper, we demonstrate that cytoplasmic Pten was translocated into the nuclei of neurons after cerebral ischemia in mice. Critically, this transport event was dependent on a surge in the Nedd4 family-interacting protein 1 (Ndfip1), as neurons in Ndfip1-deficient mice failed to import Pten. Ndfip1 binds to Pten, resulting in enhanced ubiquitination by Nedd4 E3 ubiquitin ligases. In vitro, Ndfip1 overexpression increased the rate of Pten nuclear import detected by photobleaching experiments, whereas Ndfip1(-/-) fibroblasts showed negligible transport rates. In vivo, Ndfip1 mutant mice suffered larger infarct sizes associated with suppressed phosphorylated Akt activation. Our findings provide the first physiological example of when and why transient shuttling of nuclear Pten occurs and how this process is critical for neuron survival.
    The Journal of Cell Biology 01/2012; 196(1):29-36. DOI:10.1083/jcb.201105009 · 9.83 Impact Factor
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    ABSTRACT: PTEN (phosphatase and tensin homologue deleted in chromosome 10) was first identified as a candidate tumour suppressor gene located on chromosome 10q23. It is considered as one of the most frequently mutated genes in human malignancies. Emerging evidence shows that the biological function of PTEN extends beyond its tumour suppressor activity. In the central nervous system PTEN is a crucial regulator of neuronal development, neuronal survival, axonal regeneration and synaptic plasticity. Furthermore, PTEN has been linked to the pathogenesis of neurodegenerative disorders such as Alzheimer’s disease, Parkinson’s disease and amyotrophic lateral sclerosis. Recently increased attention has been focused on PTEN as a potential target for the treatment of brain injury and neurodegeneration. In this review we discuss the essential functions of PTEN in the central nervous system and its involvement in neurodegeneration.
    06/2012; 3(2). DOI:10.2478/s13380-012-0018-9
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