Up-Regulation of TREK-2 Potassium Channels in Cultured Astrocytes Requires De Novo Protein Synthesis: Relevance to Localization of TREK-2 Channels in Astrocytes after Transient Cerebral Ischemia

Abstract

Excitotoxicity due to glutamate receptor over-activation is one of the key mediators of neuronal death after an ischemic insult. Therefore, a major function of astrocytes is to maintain low extracellular levels of glutamate. The ability of astrocytic glutamate transporters to regulate the extracellular glutamate concentration depends upon the hyperpolarized membrane potential of astrocytes conferred by the presence of K+ channels in their membranes. We have previously shown that TREK-2 potassium channels in cultured astrocytes are up-regulated by ischemia and may support glutamate clearance by astrocytes during ischemia. Thus, herein we determine the mechanism leading to this up-regulation and assess the localization of TREK-2 channels in astrocytes after transient middle cerebral artery occlusion. By using a cell surface biotinylation assay we confirmed that functional TREK-2 protein is up-regulated in the astrocytic membrane after ischemic conditions. Using real time RT-PCR, we determined that the levels of TREK-2 mRNA were not increased in response to ischemic conditions. By using Western blot and a variety of protein synthesis inhibitors, we demonstrated that the increase of TREK-2 protein expression requires De novo protein synthesis, while protein degradation pathways do not contribute to TREK-2 up-regulation after ischemic conditions. Immunohistochemical studies revealed TREK-2 localization in astrocytes together with increased expression of the selective glial marker, glial fibrillary acidic protein, in brain 24 hours after transient middle cerebral occlusion. Our data indicate that functional TREK-2 channels are up-regulated in the astrocytic membrane during ischemia through a mechanism requiring De novo protein synthesis. This study provides important information about the mechanisms underlying TREK-2 regulation, which has profound implications in neurological diseases such as ischemia where astrocytes play an important role.

Intersubunit Concerted Cooperative and cis-Type Mechanisms Modulate Allosteric Gating in Two-Pore-Domain Potassium Channel TREK-2

“…Activating TREK-2 leads to GABAnergic and noradrenergic inhibition of neuronal excitability in the entorhinal cortex, which is regarded as the gateway to the hippocampus and thus is essential for learning and memory (Deng et al, 2009 ; Xiao et al, 2009 ). In response to ischemia, TREK-2 expression is up-regulated in the astrocytic membrane (Rivera-Pagán et al, 2015 ), cortical and hippocampal neurons (Li et al, 2005 ). Therefore, TREK-2 has been implicated to be a new potential therapeutic target for treating neuropathic pain, mood disorders and ischemia.…”

Astrocytic AEG‐1 regulates expression of TREK‐1 under acute hypoxia

“…AEG‐1 causes glutamate excitotoxicity in the brain by downregulating expression of EAAT2, which disturbs extracellular glutamate uptake in astrocytes . However, we showed here that AEG‐1 mediates hypoxia‐induced TREK‐1 expression and may act as a neuroprotector by promoting K + buffering.…”

Retrieval of germinal zone neural stem cells from the cerebrospinal fluid of premature infants with intraventricular hemorrhage

“…DLK1 is developmentally expressed in NSCs in the GEs and maybe involved in the regulation of the stem cell pool 56 . On the other hand, TREK2 ( KCNK10 ) a potassium channel that has been reported to be expressed by the ependymal cells 57 and upregulated together with GFAP under ischemic conditions in astrocytes 58 was transcriptionally downregulated in sorted Gz‐NSCs, yet the protein was maintained. Collectively these data provide a distinctive Gz‐NSC signature that is not dependent on the contribution of more differentiated cell types or contaminating lineages in the starting samples.…”