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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    • "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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