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Rivera-Aponte DE, Melnik-Martínez KV, Malpica-Nieves CJ, Tejeda-Bayron F, Méndez-González MP, Skatchkov SN, Eaton MJ. Kir4.1 potassium channel regulation via microRNA-205 in astrocytes exposed to hyperglycemic conditions. Neuroreport 2020; 31:450-455. [PMID: 32168096 PMCID: PMC7127973 DOI: 10.1097/wnr.0000000000001427] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Protecting neurons from neurotoxicity is a job mainly performed by astrocytes through glutamate uptake and potassium buffering. These functions are aided principally by the Kir4.1 inwardly rectifying potassium channels located in the membrane of astrocytes. Astrocytes grown in hyperglycemic conditions have decreased levels of Kir4.1 potassium channels as well as impaired potassium and glutamate uptake. Previous studies performed in a human corneal epithelial cell injury model demonstrated a mechanism of regulation of Kir4.1 expression via the binding of microRNA-250 (miR-205) to the Kir4.1 3´ untranslated region. Our purpose is to test if astrocytes express miR-205 and elucidate its role in regulating Kir4.1 expression in astrocytes grown in hyperglycemic conditions. We used quantitative-PCR to assess the levels of miR-205 in astrocytes grown in high glucose (25 mM) medium compared to astrocytes grown in normal glucose (5 mM). We found that not only was miR-205 expressed in astrocytes grown in normal glucose, but its expression was increased up to six-fold in astrocytes grown in hyperglycemic conditions. Transfection of miR-205 mimic or inhibitor was performed to alter the levels of miR-205 in astrocytes followed by western blot to assess Kir4.1 channel levels in these cells. Astrocytes treated with miR-205 mimic had a 38.6% reduction of Kir4.1 protein levels compared to control (mock-transfected) cells. In contrast, astrocytes transfected with miR-205 inhibitor were significantly upregulated compared to mock by 47.4%. Taken together, our data indicate that miR-205 negatively regulates the expression of Kir4.1 in astrocytes grown in hyperglycemic conditions.
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Affiliation(s)
| | | | | | - Flavia Tejeda-Bayron
- Department of Biochemistry, Universidad Central del Caribe, Bayamón, Puerto Rico
| | - Miguel P. Méndez-González
- Department of Natural Sciences, University of Puerto Rico, Aguadilla, Puerto Rico
- Department of Sciences and Technology, Antilles Adventist University, Mayagüez, Puerto Rico
| | - Serguei N. Skatchkov
- Department of Biochemistry, Universidad Central del Caribe, Bayamón, Puerto Rico
- Department of Physiology, Universidad Central del Caribe, Bayamón, Puerto Rico
| | - Misty J. Eaton
- Department of Biochemistry, Universidad Central del Caribe, Bayamón, Puerto Rico
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Rivera-Pagán AF, Méndez-González MP, Rivera-Aponte DE, Malpica-Nieves CJ, Melnik-Martínez KV, Zayas-Santiago A, Maldonado-Martínez G, Shuba YM, Skatchkov SN, Eaton MJ. A-Kinase-Anchoring Protein (AKAP150) is expressed in Astrocytes and Upregulated in Response to Ischemia. Neuroscience 2018; 384:54-63. [PMID: 29800717 DOI: 10.1016/j.neuroscience.2018.05.019] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2018] [Revised: 05/11/2018] [Accepted: 05/14/2018] [Indexed: 10/16/2022]
Abstract
A-kinase-anchoring proteins, AKAPs, are scaffolding proteins that associate with kinases and phosphatases, and direct them to a specific submembrane site to coordinate signaling events. AKAP150, a rodent ortholog of human AKAP79, has been extensively studied in neurons, but very little is known about the localization and function of AKAP150 in astrocytes, the major cell type in brain. Thus, in this study, we assessed the localization of AKAP150 in astrocytes and elucidated its role during physiological and ischemic conditions. Herein, we demonstrate that AKAP150 is localized in astrocytes and is up-regulated during ischemia both in vitro and in vivo. Knock-down of AKAP150 by RNAi depolarizes the astrocytic membrane potential and substantially reduces by 80% the ability of astrocytes to take up extracellular potassium during ischemic conditions. Therefore, upregulation of AKAP150 during ischemia preserves potassium conductance and the associated hyperpolarized membrane potential of astrocytes; properties of astrocytes needed to maintain extracellular brain homeostasis. Taken together, these data suggest that AKAP150 may play a pivotal role in the neuroprotective mechanism of astrocytes during pathological conditions.
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Affiliation(s)
- Aixa F Rivera-Pagán
- Department of Biochemistry, Universidad Central del Caribe, Bayamón, PR, United States
| | - Miguel P Méndez-González
- Department of Biochemistry, Universidad Central del Caribe, Bayamón, PR, United States; University of Puerto Rico, Natural Sciences Department, Aguadilla, PR, United States
| | - David E Rivera-Aponte
- Department of Biochemistry, Universidad Central del Caribe, Bayamón, PR, United States
| | | | | | - Astrid Zayas-Santiago
- Department of Pathology and Laboratory Medicine, Universidad Central del Caribe, Bayamón, PR, United States
| | | | - Yaroslav M Shuba
- Bogomoletz Institute of Physiology and International Center of Molecular Physiology of the National Academy of Sciences of Ukraine, Kiev, Ukraine
| | - Serguei N Skatchkov
- Department of Biochemistry, Universidad Central del Caribe, Bayamón, PR, United States; Department of Physiology, Universidad Central del Caribe, Bayamón, PR, United States.
| | - Misty J Eaton
- Department of Biochemistry, Universidad Central del Caribe, Bayamón, PR, United States.
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Rivera-Pagán AF, Rivera-Aponte DE, Melnik-Martínez KV, Zayas-Santiago A, Kucheryavykh LY, Martins AH, Cubano LA, Skatchkov SN, Eaton MJ. 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. PLoS One 2015; 10:e0125195. [PMID: 25886567 PMCID: PMC4401746 DOI: 10.1371/journal.pone.0125195] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2014] [Accepted: 03/12/2015] [Indexed: 11/19/2022] Open
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.
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Affiliation(s)
- Aixa F. Rivera-Pagán
- Department of Biochemistry, Universidad Central del Caribe, Bayamón, Puerto Rico, United States of America
- * E-mail: (AFRP); (SNS)
| | - David E. Rivera-Aponte
- Department of Biochemistry, Universidad Central del Caribe, Bayamón, Puerto Rico, United States of America
| | - Katya V. Melnik-Martínez
- Department of Biochemistry, Universidad Central del Caribe, Bayamón, Puerto Rico, United States of America
| | - Astrid Zayas-Santiago
- Department of Physiology, Universidad Central del Caribe, Bayamón, Puerto Rico, United States of America
| | - Lilia Y. Kucheryavykh
- Department of Biochemistry, Universidad Central del Caribe, Bayamón, Puerto Rico, United States of America
| | - Antonio H. Martins
- Department of Biochemistry, Universidad Central del Caribe, Bayamón, Puerto Rico, United States of America
| | - Luis A. Cubano
- Departments of Anatomy and Cell Biology, Universidad Central del Caribe, Bayamón, Puerto Rico, United States of America
| | - Serguei N. Skatchkov
- Department of Biochemistry, Universidad Central del Caribe, Bayamón, Puerto Rico, United States of America
- Department of Physiology, Universidad Central del Caribe, Bayamón, Puerto Rico, United States of America
- * E-mail: (AFRP); (SNS)
| | - Misty J. Eaton
- Department of Biochemistry, Universidad Central del Caribe, Bayamón, Puerto Rico, United States of America
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