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Banerjee B, Medda BK, Zhang J, Tuchscherer V, Babygirija R, Kannampalli P, Sengupta JN, Shaker R. Prolonged esophageal acid exposures induce synaptic downscaling of cortical membrane AMPA receptor subunits in rats. Neurogastroenterol Motil 2016; 28:1356-69. [PMID: 27271201 PMCID: PMC5063079 DOI: 10.1111/nmo.12834] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/05/2016] [Accepted: 03/11/2016] [Indexed: 02/08/2023]
Abstract
BACKGROUND We recently reported the involvement of AMPA (α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid) receptor subunit upregulation and phosphorylation in the rostral cingulate cortex (rCC) as the underlying mechanism of acute esophageal acid-induced cortical sensitization. Based on these findings, we proposed to investigate whether prolonged esophageal acid exposures in rats exhibit homeostatic synaptic scaling through downregulation of AMPA receptor expression in rCC neurons. We intended to study further whether this compensatory mechanism is impaired when rats are pre-exposed to repeated esophageal acid exposures neonatally during neuronal development. METHODS Two different esophageal acid exposure protocols in rats were used. Since AMPA receptor trafficking and channel conductance depend on CaMKIIα-mediated phosphorylation of AMPA receptor subunits, we examined the effect of esophageal acid on CaMKIIα activation and AMPA receptor expression in synaptoneurosomes and membrane preparations from rCCs. KEY RESULTS In cortical membrane preparations, GluA1 and pGluA1Ser(831) expression were significantly downregulated following prolonged acid exposures in adult rats; this was accompanied by the significant downregulation of cortical membrane pCaMKIIα expression. No change in GluA1 and pGluA1Ser(831) expression was observed in rCC membrane preparations in rats pre-exposed to acid neonatally followed by adult rechallenge. CONCLUSIONS & INFERENCES This study along with our previous findings suggests that synaptic AMPA receptor subunits expression and phosphorylation may be involved bidirectionally in both esophageal acid-induced neuronal sensitization and acid-dependent homeostatic plasticity in cortical neurons. The impairment of homeostatic compensatory mechanism as observed following early-in-life acid exposure could be the underlying mechanism of heightening cortical sensitization and esophageal hypersensitivity in patients with gastroesophageal reflux disease.
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Affiliation(s)
- Banani Banerjee
- Gastroenterology & Hepatology, Department of Medicine, Medical College of Wisconsin, Milwaukee, WI, United States
| | - Bidyut K Medda
- Gastroenterology & Hepatology, Department of Medicine, Medical College of Wisconsin, Milwaukee, WI, United States
| | - Jian Zhang
- Gastroenterology & Hepatology, Department of Medicine, Medical College of Wisconsin, Milwaukee, WI, United States
| | | | - Reji Babygirija
- Gastroenterology & Hepatology, Department of Pediatrics, Medical College of Wisconsin, Milwaukee, WI, United States
| | - Pradeep Kannampalli
- Gastroenterology & Hepatology, Department of Medicine, Medical College of Wisconsin, Milwaukee, WI, United States
| | - Jyoti N. Sengupta
- Gastroenterology & Hepatology, Department of Medicine, Medical College of Wisconsin, Milwaukee, WI, United States
| | - Reza Shaker
- Gastroenterology & Hepatology, Department of Medicine, Medical College of Wisconsin, Milwaukee, WI, United States
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152
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De Jesús-Cortés H, Lu Y, Anderson RM, Khan MZ, Nath V, McDaniel L, Lutter M, Radley JJ, Pieper AA, Cui H. Loss of estrogen-related receptor alpha disrupts ventral-striatal synaptic function in female mice. Neuroscience 2016; 329:66-73. [PMID: 27155145 PMCID: PMC8916097 DOI: 10.1016/j.neuroscience.2016.04.054] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2016] [Revised: 04/09/2016] [Accepted: 04/29/2016] [Indexed: 10/21/2022]
Abstract
Eating disorders (EDs), including anorexia nervosa, bulimia nervosa and binge-ED, are mental illnesses characterized by high morbidity and mortality. While several studies have identified neural deficits in patients with EDs, the cellular and molecular basis of the underlying dysfunction has remained poorly understood. We previously identified a rare missense mutation in the transcription factor estrogen-related receptor alpha (ESRRA) associated with development of EDs. Because ventral-striatal signaling is related to the reward and motivation circuitry thought to underlie EDs, we performed functional and structural analysis of ventral-striatal synapses in Esrra-null mice. Esrra-null female, but not male, mice exhibit altered miniature excitatory postsynaptic currents on medium spiny neurons (MSNs) in the ventral striatum, including increased frequency, increased amplitude, and decreased paired pulse ratio. These electrophysiological measures are associated with structural and molecular changes in synapses of MSNs in the ventral striatum, including fewer pre-synaptic glutamatergic vesicles and enhanced GluR1 function. Neuronal Esrra is thus required for maintaining normal synaptic function in the ventral striatum, which may offer mechanistic insights into the behavioral deficits observed in Esrra-null mice.
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Affiliation(s)
- Héctor De Jesús-Cortés
- Department of Psychiatry, University of Iowa, Carver College of Medicine, Iowa City, IA, USA
| | - Yuan Lu
- Department of Psychiatry, University of Iowa, Carver College of Medicine, Iowa City, IA, USA
| | - Rachel M Anderson
- Department of Psychology, University of Iowa, Carver College of Medicine, Iowa City, IA, USA
| | - Michael Z Khan
- Department of Psychiatry, University of Iowa, Carver College of Medicine, Iowa City, IA, USA
| | - Varun Nath
- Department of Psychiatry, University of Iowa, Carver College of Medicine, Iowa City, IA, USA
| | - Latisha McDaniel
- Department of Psychiatry, University of Iowa, Carver College of Medicine, Iowa City, IA, USA
| | - Michael Lutter
- Department of Psychiatry, University of Iowa, Carver College of Medicine, Iowa City, IA, USA
| | - Jason J Radley
- Department of Psychology, University of Iowa, Carver College of Medicine, Iowa City, IA, USA
| | - Andrew A Pieper
- Department of Psychiatry, University of Iowa, Carver College of Medicine, Iowa City, IA, USA; Department of Neurology, University of Iowa, Carver College of Medicine, Iowa City, IA, USA; Free Radical & Radiation Biology Program, Department of Radiation Oncology Holden Comprehensive Cancer Center, University of Iowa, Carver College of Medicine, Iowa City, IA, USA
| | - Huxing Cui
- Department of Psychiatry, University of Iowa, Carver College of Medicine, Iowa City, IA, USA.
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153
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Abstract
Regulation of AMPA receptor (AMPAR) function is a fundamental mechanism controlling synaptic strength during long-term potentiation/depression and homeostatic scaling. AMPAR function and membrane trafficking is controlled by protein-protein interactions, as well as by posttranslational modifications. Phosphorylation of the GluA1 AMPAR subunit at S845 and S831 play especially important roles during synaptic plasticity. Recent controversy has emerged regarding the extent to which GluA1 phosphorylation may contribute to synaptic plasticity. Here we used a variety of methods to measure the population of phosphorylated GluA1-containing AMPARs in cultured primary neurons and mouse forebrain. Phosphorylated GluA1 represents large fractions from 12% to 50% of the total population under basal and stimulated conditions in vitro and in vivo. Furthermore, a large fraction of synapses are positive for phospho-GluA1-containing AMPARs. Our results support the large body of research indicating a prominent role of GluA1 phosphorylation in synaptic plasticity.
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154
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Li YL, Zhou J, Zhang H, Luo Y, Long LH, Hu ZL, Chen JG, Wang F, Wu PF. Hydrogen Sulfide Promotes Surface Insertion of Hippocampal AMPA Receptor GluR1 Subunit via Phosphorylating at Serine-831/Serine-845 Sites Through a Sulfhydration-Dependent Mechanism. CNS Neurosci Ther 2016; 22:789-98. [PMID: 27380893 DOI: 10.1111/cns.12585] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2016] [Revised: 05/13/2016] [Accepted: 06/10/2016] [Indexed: 12/14/2022] Open
Abstract
AIMS Hydrogen sulfide (H2 S) has been widely accepted as a gas neuromodulator to regulate synaptic function. Herein, we set out to determine the effect of H2 S on α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid receptor (AMPAR) and its mechanism. METHODS BS(3) protein cross-linking, Western blot, patch clamp, and biotin-switch assay. RESULTS Bath application of H2 S donor NaHS (50 and 100 μM) rapidly promoted surface insertion of hippocampal AMPAR GluR1 subunit. This effect can be abolished by dithiothreitol (DTT) and mimicked by Na2 S4 , indicating that a sulfhydration-dependent mechanism may be involved. NaHS increased APMAR-mediated EPSC and led to an elevation of GluR2-lacking AMPAR content. Notably, NaHS did not increase the sulfhydration of AMPAR subunits, but it significantly increased the phosphorylation of GluR1 at serine-831 and serine-845 sites. Postsynaptic signal pathways that control GluR1 phosphorylation, such as protein kinase A (PKA), protein kinase C, and calcium/calmodulin-dependent protein kinases II (CaMKII), were sulfhydrated, activated by NaHS, and these effects can be occluded by DTT. H2 S increased S-sulfhydration of protein phosphatase type 2A (PP2A), which may be partially involved in the activation of signal pathways. CONCLUSION Our data suggest that H2 S promotes surface insertion of AMPARs via phosphorylation of GluR1, which depends on a sulfhydration-mediated mechanism.
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Affiliation(s)
- Yuan-Long Li
- Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China
| | - Jun Zhou
- Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China
| | - Hai Zhang
- Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China
| | - Yi Luo
- Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China
| | - Li-Hong Long
- Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China.,Key Laboratory of Neurological Diseases (HUST), Ministry of Education of China, Wuhan, Hubei, China.,The Key Laboratory for Drug Target Researches and Pharmacodynamic Evaluation of Hubei Province, Wuhan, Hubei, China.,Laboratory of Neuropsychiatric Diseases, The Institute of Brain Research, Huazhong University of Science and Technology, Wuhan, Hubei, China
| | - Zhuang-Li Hu
- Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China.,Key Laboratory of Neurological Diseases (HUST), Ministry of Education of China, Wuhan, Hubei, China.,The Key Laboratory for Drug Target Researches and Pharmacodynamic Evaluation of Hubei Province, Wuhan, Hubei, China.,Laboratory of Neuropsychiatric Diseases, The Institute of Brain Research, Huazhong University of Science and Technology, Wuhan, Hubei, China
| | - Jian-Guo Chen
- Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China.,Key Laboratory of Neurological Diseases (HUST), Ministry of Education of China, Wuhan, Hubei, China.,The Key Laboratory for Drug Target Researches and Pharmacodynamic Evaluation of Hubei Province, Wuhan, Hubei, China.,Laboratory of Neuropsychiatric Diseases, The Institute of Brain Research, Huazhong University of Science and Technology, Wuhan, Hubei, China
| | - Fang Wang
- Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China.,Key Laboratory of Neurological Diseases (HUST), Ministry of Education of China, Wuhan, Hubei, China.,The Key Laboratory for Drug Target Researches and Pharmacodynamic Evaluation of Hubei Province, Wuhan, Hubei, China.,Laboratory of Neuropsychiatric Diseases, The Institute of Brain Research, Huazhong University of Science and Technology, Wuhan, Hubei, China
| | - Peng-Fei Wu
- Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China.,Key Laboratory of Neurological Diseases (HUST), Ministry of Education of China, Wuhan, Hubei, China.,The Key Laboratory for Drug Target Researches and Pharmacodynamic Evaluation of Hubei Province, Wuhan, Hubei, China.,Laboratory of Neuropsychiatric Diseases, The Institute of Brain Research, Huazhong University of Science and Technology, Wuhan, Hubei, China
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155
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Kim K, Saneyoshi T, Hosokawa T, Okamoto K, Hayashi Y. Interplay of enzymatic and structural functions of CaMKII in long-term potentiation. J Neurochem 2016; 139:959-972. [DOI: 10.1111/jnc.13672] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2016] [Revised: 05/09/2016] [Accepted: 05/10/2016] [Indexed: 12/17/2022]
Affiliation(s)
- Karam Kim
- Brain Science Institute; RIKEN; Wako Saitama Japan
| | | | | | - Kenichi Okamoto
- Lunenfeld-Tanenbaum Research Institute; Mount Sinai Hospital; Toronto ON Canada
- Department of Molecular Genetics; Faculty of Medicine; University of Toronto; Toronto ON Canada
| | - Yasunori Hayashi
- Brain Science Institute; RIKEN; Wako Saitama Japan
- Saitama University Brain Science Institute; Saitama University; Saitama Japan
- School of Life Science; South China Normal University; Guangzhou China
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156
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Pai YH, Lim CS, Park KA, Cho HS, Lee GS, Shin YS, Kim HW, Jeon BH, Yoon SH, Park JB. Facilitation of AMPA receptor-mediated steady-state current by extrasynaptic NMDA receptors in supraoptic magnocellular neurosecretory cells. THE KOREAN JOURNAL OF PHYSIOLOGY & PHARMACOLOGY : OFFICIAL JOURNAL OF THE KOREAN PHYSIOLOGICAL SOCIETY AND THE KOREAN SOCIETY OF PHARMACOLOGY 2016; 20:425-32. [PMID: 27382359 PMCID: PMC4930911 DOI: 10.4196/kjpp.2016.20.4.425] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/28/2016] [Revised: 06/06/2016] [Accepted: 06/09/2016] [Indexed: 01/02/2023]
Abstract
In addition to classical synaptic transmission, information is transmitted between cells via the activation of extrasynaptic receptors that generate persistent tonic current in the brain. While growing evidence supports the presence of tonic NMDA current (INMDA) generated by extrasynaptic NMDA receptors (eNMDARs), the functional significance of tonic INMDA in various brain regions remains poorly understood. Here, we demonstrate that activation of eNMDARs that generate INMDA facilitates the α-amino-3-hydroxy-5-methylisoxazole-4-proprionate receptor (AMPAR)-mediated steady-state current in supraoptic nucleus (SON) magnocellular neurosecretory cells (MNCs). In low-Mg2+ artificial cerebrospinal fluid (aCSF), glutamate induced an inward shift in Iholding (IGLU) at a holding potential (Vholding) of –70 mV which was partly blocked by an AMPAR antagonist, NBQX. NBQX-sensitive IGLU was observed even in normal aCSF at Vholding of –40 mV or –20 mV. IGLU was completely abolished by pretreatment with an NMDAR blocker, AP5, under all tested conditions. AMPA induced a reproducible inward shift in Iholding (IAMPA) in SON MNCs. Pretreatment with AP5 attenuated IAMPA amplitudes to ~60% of the control levels in low-Mg2+ aCSF, but not in normal aCSF at Vholding of –70 mV. IAMPA attenuation by AP5 was also prominent in normal aCSF at depolarized holding potentials. Memantine, an eNMDAR blocker, mimicked the AP5-induced IAMPA attenuation in SON MNCs. Finally, chronic dehydration did not affect IAMPA attenuation by AP5 in the neurons. These results suggest that tonic INMDA, mediated by eNMDAR, facilitates AMPAR function, changing the postsynaptic response to its agonists in normal and osmotically challenged SON MNCs.
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Affiliation(s)
- Yoon Hyoung Pai
- Department of Physiology, Brain Research Institute, School of Medicine, Chungnam National University, Daejeon 35015, Korea
| | - Chae Seong Lim
- Department of Anesthesiology & Pain Medicine, Brain Research Institute, School of Medicine, Chungnam National University, Daejeon 35015, Korea
| | - Kyung-Ah Park
- Department of Physiology, Brain Research Institute, School of Medicine, Chungnam National University, Daejeon 35015, Korea
| | - Hyun Sil Cho
- Department of Physiology, Brain Research Institute, School of Medicine, Chungnam National University, Daejeon 35015, Korea
| | - Gyu-Seung Lee
- Department of Physiology, Brain Research Institute, School of Medicine, Chungnam National University, Daejeon 35015, Korea
| | - Yong Sup Shin
- Department of Anesthesiology & Pain Medicine, Brain Research Institute, School of Medicine, Chungnam National University, Daejeon 35015, Korea
| | - Hyun-Woo Kim
- Department of Physiology, Brain Research Institute, School of Medicine, Chungnam National University, Daejeon 35015, Korea
| | - Byeong Hwa Jeon
- Department of Physiology, Brain Research Institute, School of Medicine, Chungnam National University, Daejeon 35015, Korea
| | - Seok Hwa Yoon
- Department of Anesthesiology & Pain Medicine, Brain Research Institute, School of Medicine, Chungnam National University, Daejeon 35015, Korea
| | - Jin Bong Park
- Department of Physiology, Brain Research Institute, School of Medicine, Chungnam National University, Daejeon 35015, Korea
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157
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Structural rearrangement of the intracellular domains during AMPA receptor activation. Proc Natl Acad Sci U S A 2016; 113:E3950-9. [PMID: 27313205 DOI: 10.1073/pnas.1601747113] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
α-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPARs) are ligand-gated ion channels that mediate the majority of fast excitatory neurotransmission in the central nervous system. Despite recent advances in structural studies of AMPARs, information about the specific conformational changes that underlie receptor function is lacking. Here, we used single and dual insertion of GFP variants at various positions in AMPAR subunits to enable measurements of conformational changes using fluorescence resonance energy transfer (FRET) in live cells. We produced dual CFP/YFP-tagged GluA2 subunit constructs that had normal activity and displayed intrareceptor FRET. We used fluorescence lifetime imaging microscopy (FLIM) in live HEK293 cells to determine distinct steady-state FRET efficiencies in the presence of different ligands, suggesting a dynamic picture of the resting state. Patch-clamp fluorometry of the double- and single-insert constructs showed that both the intracellular C-terminal domain (CTD) and the loop region between the M1 and M2 helices move during activation and the CTD is detached from the membrane. Our time-resolved measurements revealed unexpectedly complex fluorescence changes within these intracellular domains, providing clues as to how posttranslational modifications and receptor function interact.
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158
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Toussaint F, Charbel C, Allen BG, Ledoux J. Vascular CaMKII: heart and brain in your arteries. Am J Physiol Cell Physiol 2016; 311:C462-78. [PMID: 27306369 DOI: 10.1152/ajpcell.00341.2015] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2015] [Accepted: 06/14/2016] [Indexed: 01/02/2023]
Abstract
First characterized in neuronal tissues, the multifunctional calcium/calmodulin-dependent protein kinase II (CaMKII) is a key signaling component in several mammalian biological systems. Its unique capacity to integrate various Ca(2+) signals into different specific outcomes is a precious asset to excitable and nonexcitable cells. Numerous studies have reported roles and mechanisms involving CaMKII in brain and heart tissues. However, corresponding functions in vascular cell types (endothelium and vascular smooth muscle cells) remained largely unexplored until recently. Investigation of the intracellular Ca(2+) dynamics, their impact on vascular cell function, the regulatory processes involved and more recently the spatially restricted oscillatory Ca(2+) signals and microdomains triggered significant interest towards proteins like CaMKII. Heteromultimerization of CaMKII isoforms (four isoforms and several splice variants) expands this kinase's peculiar capacity to decipher Ca(2+) signals and initiate specific signaling processes, and thus controlling cellular functions. The physiological functions that rely on CaMKII are unsurprisingly diverse, ranging from regulating contractile state and cellular proliferation to Ca(2+) homeostasis and cellular permeability. This review will focus on emerging evidence of CaMKII as an essential component of the vascular system, with a focus on the kinase isoform/splice variants and cellular system studied.
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Affiliation(s)
- Fanny Toussaint
- Research Center, Montreal Heart Institute, Montreal, Quebec, Canada; Department of Molecular and Integrative Physiology, Université de Montréal, Montreal Quebec, Canada
| | - Chimène Charbel
- Research Center, Montreal Heart Institute, Montreal, Quebec, Canada; Department of Pharmacology, Université de Montréal, Montreal Quebec, Canada
| | - Bruce G Allen
- Research Center, Montreal Heart Institute, Montreal, Quebec, Canada; Department of Medicine, Université de Montréal, Montreal Quebec, Canada; and Department of Biochemistry and Molecular Medicine, Université de Montréal, Montreal Quebec, Canada
| | - Jonathan Ledoux
- Research Center, Montreal Heart Institute, Montreal, Quebec, Canada; Department of Medicine, Université de Montréal, Montreal Quebec, Canada; and
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159
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Calcium-Permeable AMPA Receptors Mediate the Induction of the Protein Kinase A-Dependent Component of Long-Term Potentiation in the Hippocampus. J Neurosci 2016; 36:622-31. [PMID: 26758849 DOI: 10.1523/jneurosci.3625-15.2016] [Citation(s) in RCA: 67] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
UNLABELLED Two forms of NMDA receptor (NMDAR)-dependent long-term potentiation (LTP) at hippocampal CA1 synapses can be distinguished based on their sensitivity to inhibitors of protein kinase A (PKA). The PKA-dependent form requires multiple episodes of high-frequency stimulation (HFS) or theta burst stimuli (TBS) with a spacing between episodes in the order of minutes. To investigate the mechanism by which spaced episodes induce the PKA-dependent form of LTP, we have compared, in interleaved experiments, spaced (s) and compressed (c) TBS protocols in the rat CA1 synapses. We find that LTP induced by sTBS, but not that induced by cTBS, involves the insertion of calcium-permeable (CP) AMPARs, as assessed using pharmacological and electrophysiological criteria. Furthermore, a single TBS when paired with rolipram [4-(3-(cyclopentyloxy)-4-methoxyphenyl)pyrrolidin-2-one], to activate PKA, generates an LTP that also involves the insertion of CP-AMPARs. These data demonstrate that the involvement of CP-AMPARs in LTP is critically determined by the timing of the induction trigger and is associated specifically with the PKA-dependent form of LTP. SIGNIFICANCE STATEMENT Long-term potentiation is a family of synaptic mechanisms that are believed to be important for learning and memory. Two of the most extensively studied forms are triggered by the synaptic activation of NMDA receptors and expressed by changes in AMPA receptor function. They can be distinguished on the basis of their requirement for activation of a protein kinase, PKA. We show that the PKA-dependent form also involves the transient insertion of calcium-permeable AMPA receptors. These results have implications for relating synaptic plasticity to learning and memory and suggest a specific linkage between PKA activation and the rapid synaptic insertion of calcium-permeable AMPA receptors during long-term potentiation.
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160
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Chen Y, Derkach VA, Smith PA. Loss of Ca(2+)-permeable AMPA receptors in synapses of tonic firing substantia gelatinosa neurons in the chronic constriction injury model of neuropathic pain. Exp Neurol 2016; 279:168-177. [PMID: 26948545 DOI: 10.1016/j.expneurol.2016.03.001] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2015] [Revised: 02/29/2016] [Accepted: 03/01/2016] [Indexed: 12/11/2022]
Abstract
Synapses transmitting nociceptive information in the spinal dorsal horn undergo enduring changes following peripheral nerve injury. Indeed, such injury alters the expression of the GluA2 subunit of glutamatergic AMPA receptors (AMPARs) in the substantia gelatinosa and this predicts altered channel conductance and calcium permeability, leading to an altered function of excitatory synapses. We therefore investigated the functional properties of synaptic AMPA receptors in rat substantia gelatinosa neurons following 10-20d chronic constriction injury (CCI) of the sciatic nerve; a model of neuropathic pain. We measured their single-channel conductance and sensitivity to a blocker of calcium permeable AMPA receptors (CP-AMPARs), IEM1460 (50μM). In putative inhibitory, tonic firing neurons, CCI reduced the average single-channel conductance of synaptic AMPAR from 14.4±3.5pS (n=12) to 9.2±1.0pS (n=10, p<0.05). IEM1460 also more effectively antagonized evoked, spontaneous and miniature EPSCs in tonic neurons from sham operated animals than in those from animals that had been subjected to CCI. By contrast, CCI did not change the effectiveness of IEM1460 in delay firing neurons although average single channel conductance was increased from 7.6±1.2pS (n=11) to 12.2±1.5pS (n=10, p<0.01). CCI thus elicits plastic changes in a specific set of glutamatergic synapses of substantia gelatinosa due to subunit recomposition and loss of GluA2-lacking CP-AMPAR. These insights reveal a molecular mechanism of nerve injury acting at synapses of inhibitory neurons to reduce their drive and therefore inhibitory tone in the spinal cord, therefore contributing to the central sensitization associated with neuropathic pain.
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Affiliation(s)
- Yishen Chen
- Department of Pharmacology and Neurosciences and Mental Health Institute, University of Alberta, Edmonton, AB T6G 2H7, Canada
| | - Victor A Derkach
- Department of Biochemistry, School of Medicine, University of Washington, Seattle, WA 98195-7350, USA; Howard Hughes Medical Institute, University of Washington, Seattle, WA 98195-7350, USA
| | - Peter A Smith
- Department of Pharmacology and Neurosciences and Mental Health Institute, University of Alberta, Edmonton, AB T6G 2H7, Canada.
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161
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Jiang L, Voulalas P, Ji Y, Masri R. Post-translational modification of cortical GluA receptors in rodents following spinal cord lesion. Neuroscience 2016; 316:122-9. [PMID: 26724583 PMCID: PMC4724505 DOI: 10.1016/j.neuroscience.2015.12.038] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2015] [Revised: 12/17/2015] [Accepted: 12/21/2015] [Indexed: 11/23/2022]
Abstract
Previous studies investigating the pathophysiology of neuropathic pain caused by injury to the spinal cord suggest that pain may result, at least in part, from maladaptive plasticity in the somatosensory cortex and associated pain networks. However, little is known about the molecular and cellular mechanisms leading to maladaptive plasticity in the cortex and how they contribute to the development of neuropathic pain. AMPA-type glutamate receptors (GluARs) mediate fast excitatory synaptic transmission in the mammalian brain and play an important role in pain processing. Here we used an electrolytic lesion model of spinal cord injury in animals to study the expression and phosphorylation of GluA1 and 2 in the primary somatosensory cortex (S1). Experiments in rats and mice revealed that maladaptive plasticity and hypersensitivity after spinal cord lesion (SCL) are associated with a reduction in the fraction of GluA1 subunits that are phosphorylated at serine 831 (S831) in the hindlimb representation of S1 (S1HL). Manipulations that reduce the fraction of phosphorylated S831 in S1HL of non-lesioned animals, including low-frequency electrical stimulation and viral-mediated gene transfer of mutant S831, were associated with the development of hypersensitivity. Taken together, these findings suggest that phosphorylation of GluA1 at S831 plays an important role in the development of hypersensitivity after SCL.
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Affiliation(s)
- L Jiang
- Department of Endodontics, Periodontics, and Prosthodontics, University of Maryland School of Dentistry, Baltimore, MD 21201, United States
| | - P Voulalas
- Department of Endodontics, Periodontics, and Prosthodontics, University of Maryland School of Dentistry, Baltimore, MD 21201, United States
| | - Y Ji
- Department of Endodontics, Periodontics, and Prosthodontics, University of Maryland School of Dentistry, Baltimore, MD 21201, United States
| | - R Masri
- Department of Endodontics, Periodontics, and Prosthodontics, University of Maryland School of Dentistry, Baltimore, MD 21201, United States; Department of Anatomy and Neurobiology, University of Maryland School of Medicine, Baltimore, MD 21201, United States.
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162
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Caudal D, Rame M, Jay TM, Godsil BP. Dynamic Regulation of AMPAR Phosphorylation In Vivo Following Acute Behavioral Stress. Cell Mol Neurobiol 2016; 36:1331-1342. [PMID: 26814839 DOI: 10.1007/s10571-016-0332-9] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2015] [Accepted: 07/31/2015] [Indexed: 12/20/2022]
Abstract
The tuning of glutamatergic transmission is an essential mechanism for neuronal communication. α-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPARs) are ionotropic glutamate receptors that mediate fast synaptic transmission. The phosphorylation states of specific serine residues on the GluA1 and GluA2 AMPAR subunits are considered critical post-translational modifications that regulate AMPAR activity and subcellular trafficking. While behavioral stress, via stress hormones, exerts specific alterations on such glutamatergic processes, there have been conflicting data concerning the influence of stress on AMPAR phosphorylation in different brain regions, and the post-stress signaling mechanisms mediating these processes are not well delineated. Here, we examined the dynamics of phosphorylation at three AMPAR serine residues (ser831-GluA1, ser845-GluA1, and ser880-GluA2) in four brain regions [amygdala, medial prefrontal cortex (mPFC), dorsal hippocampus, and ventral hippocampus] of the rat during the hour following behavioral stress. We also tested the impact of post-stress corticosteroid receptor blockade on AMPAR phosphorylation. Both GluA1 subunit residues exhibited elevated phosphorylation after stress, yet post-stress administration of corticosteroid receptor antagonists curtailed these effects only at ser831-GluA1. In contrast, ser880-GluA2 displayed a time-dependent tendency for early decreased phosphorylation (that was selectively augmented by mifepristone treatment in the amygdala and mPFC of stressed animals) followed by increased phosphorylation later on. These findings show that the in vivo regulation of AMPAR phosphorylation after stress is a dynamic and subunit-specific process, and they provide support for the hypothesis that corticosteroid receptors have an ongoing role in the regulation of ser831-GluA1 phosphorylation during the post-stress interval.
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Affiliation(s)
- Dorian Caudal
- Physiopathologie des Maladies Psychiatriques, UMR_S 894 Inserm, Centre de Psychiatrie et Neurosciences, 2ter rue d'Alesia, 75014, Paris, France.,Université Paris Descartes, Sorbonne Paris Cité, Paris, France
| | - Marion Rame
- Physiopathologie des Maladies Psychiatriques, UMR_S 894 Inserm, Centre de Psychiatrie et Neurosciences, 2ter rue d'Alesia, 75014, Paris, France
| | - Thérèse M Jay
- Physiopathologie des Maladies Psychiatriques, UMR_S 894 Inserm, Centre de Psychiatrie et Neurosciences, 2ter rue d'Alesia, 75014, Paris, France.,Université Paris Descartes, Sorbonne Paris Cité, Paris, France
| | - Bill P Godsil
- Physiopathologie des Maladies Psychiatriques, UMR_S 894 Inserm, Centre de Psychiatrie et Neurosciences, 2ter rue d'Alesia, 75014, Paris, France. .,Université Paris Descartes, Sorbonne Paris Cité, Paris, France.
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163
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The Ins and Outs of miRNA-Mediated Gene Silencing during Neuronal Synaptic Plasticity. Noncoding RNA 2016; 2:ncrna2010001. [PMID: 29657259 PMCID: PMC5831896 DOI: 10.3390/ncrna2010001] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2015] [Revised: 12/11/2015] [Accepted: 12/15/2015] [Indexed: 12/18/2022] Open
Abstract
Neuronal connections through specialized junctions, known as synapses, create circuits that underlie brain function. Synaptic plasticity, i.e., structural and functional changes to synapses, occurs in response to neuronal activity and is a critical regulator of various nervous system functions, including long-term memory formation. The discovery of mRNAs, miRNAs, ncRNAs, ribosomes, translational repressors, and other RNA binding proteins in dendritic spines allows individual synapses to alter their synaptic strength rapidly through regulation of local protein synthesis in response to different physiological stimuli. In this review, we discuss our understanding of a number of miRNAs, ncRNAs, and RNA binding proteins that are emerging as important regulators of synaptic plasticity, which play a critical role in memory, learning, and diseases that arise when neuronal circuits are impaired.
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164
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Lee K, Goodman L, Fourie C, Schenk S, Leitch B, Montgomery JM. AMPA Receptors as Therapeutic Targets for Neurological Disorders. ION CHANNELS AS THERAPEUTIC TARGETS, PART A 2016; 103:203-61. [DOI: 10.1016/bs.apcsb.2015.10.004] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
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165
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CaM Kinases: From Memories to Addiction. Trends Pharmacol Sci 2015; 37:153-166. [PMID: 26674562 DOI: 10.1016/j.tips.2015.11.001] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2015] [Revised: 10/30/2015] [Accepted: 11/02/2015] [Indexed: 12/29/2022]
Abstract
Drug addiction is a major psychiatric disorder with a neurobiological basis that is still insufficiently understood. Initially, non-addicted, controlled drug consumption and drug instrumentalization are established. They comprise highly systematic behaviours acquired by learning and the establishment of drug memories. Ca(2+)/calmodulin-dependent protein kinases (CaMKs) are important Ca(2+) sensors translating glutamatergic activation into synaptic plasticity during learning and memory formation. Here we review the role of CaMKs in the establishment of drug-related behaviours in animal models and in humans. Converging evidence now shows that CaMKs are a crucial mechanism of how addictive drugs induce synaptic plasticity and establish various types of drug memories. Thereby, CaMKs are not only molecular relays for glutamatergic activity but they also directly control dopaminergic and serotonergic activity in the mesolimbic reward system. They can now be considered as major molecular pathways translating normal memory formation into establishment of drug memories and possibly transition to drug addiction.
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166
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Fernández-Fernández D, Dorner-Ciossek C, Kroker KS, Rosenbrock H. Age-related synaptic dysfunction in Tg2576 mice starts as a failure in early long-term potentiation which develops into a full abolishment of late long-term potentiation. J Neurosci Res 2015; 94:266-81. [PMID: 26629777 DOI: 10.1002/jnr.23701] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2015] [Revised: 09/30/2015] [Accepted: 11/17/2015] [Indexed: 11/12/2022]
Abstract
Tg2576 mice are widely used to study amyloid-dependent synaptic dysfunction related to Alzheimer's disease. However, conflicting data have been reported for these mice with regard to basal transmission as well as the in vitro correlate of memory, long-term potentiation (LTP). Some studies show clear impairments, whereas others report no deficiency. The present study uses hippocampal slices from 3-, 10-, and 15-month-old wild-type (WT) and Tg2576 mice to evaluate synaptic function in each group, including experiments to investigate basal synaptic transmission, short- and long-term plasticity by inducing paired-pulse facilitation, and both early and late LTP. We show that synaptic function remains intact in hippocampal slices from Tg2576 mice at 3 months of age. However, both early and late LTP decline progressively during aging in these mice. This deterioration of synaptic plasticity starts affecting early LTP, ultimately leading to the abolishment of both forms of LTP in 15-month-old animals. In comparison, WT littermates display normal synaptic parameters during aging. Additional pharmacological investigation into the involvement of NMDA receptors and L-type voltage-gated calcium channels in LTP suggests a distinct mechanism of induction among age groups, demonstrating that both early and late LTP are differentially affected by these channels in Tg2576 mice during aging.
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Affiliation(s)
- Diego Fernández-Fernández
- Deparment of CNS Diseases Research, Boehringer Ingelheim Pharma GmbH & Co. KG, Biberach (Riss), Germany
| | - Cornelia Dorner-Ciossek
- Deparment of CNS Diseases Research, Boehringer Ingelheim Pharma GmbH & Co. KG, Biberach (Riss), Germany
| | - Katja S Kroker
- Deptartment of Drug Discovery Support, Boehringer Ingelheim Pharma GmbH & Co. KG, Biberach (Riss), Germany
| | - Holger Rosenbrock
- Deparment of CNS Diseases Research, Boehringer Ingelheim Pharma GmbH & Co. KG, Biberach (Riss), Germany
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167
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Oligodendrocytes Are Targets of HIV-1 Tat: NMDA and AMPA Receptor-Mediated Effects on Survival and Development. J Neurosci 2015; 35:11384-98. [PMID: 26269645 DOI: 10.1523/jneurosci.4740-14.2015] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
UNLABELLED Myelin pallor in HIV(+) individuals can occur very early during the disease process. While myelin damage might partly originate from HIV-induced vascular changes, the timing suggests that myelin and/or oligodendrocytes (OLs) may be directly affected. Histological (Golgi-Kopsch, electron microscopy) and biochemical studies have revealed an increased occurrence of abnormal OL/myelin morphology and dysregulated myelin protein expression in transgenic mice expressing the HIV-1 transactivator of transcription (Tat) protein. This suggests that viral proteins by themselves might cause OL injury. Since Tat interacts with NMDARs, we hypothesized that activation of NMDARs and subsequent disruption of cytoplasmic Ca(2+) ([Ca(2+)]i) homeostasis might be one cause of white matter injury after HIV infection. In culture, HIV-1 Tat caused concentration-dependent death of immature OLs, while more mature OLs remained alive but had reduced myelin-like membranes. Tat also induced [Ca(2+)]i increases and Thr-287 autophosphorylation of Ca(2+)/calmodulin-dependent protein kinase II β (CaMKIIβ) in OLs. Tat-induced [Ca(2+)]i was attenuated by the NMDAR antagonist MK801, and also by the AMPA/kainate receptor antagonist CNQX. Importantly, both MK801 and CNQX blocked Tat-induced death of immature OLs, but only MK801 reversed Tat effects on myelin-like membranes. These results suggest that OLs can be direct targets of HIV proteins released from infected cells. Although viability and membrane production are both affected by glutamatergic receptor-mediated Ca(2+) influx, and possibly the ensuing CaMKIIβ activation, the roles of AMPARs and NMDARs appear to be different and dependent on the stage of OL differentiation. SIGNIFICANCE STATEMENT Over 33 million individuals are currently infected by HIV. Among these individuals, ∼60% develop HIV-associated neurocognitive disorders. Myelin damage and white matter injury have been frequently reported in HIV patients but not extensively studied. Clinical studies using combined antiretroviral therapy (cART) together with adjunctive "anti-inflammatory" drugs show no improvement over cART alone, suggesting existence of injury mechanisms in addition to inflammation. In our studies, oligodendrocytes exhibited rapid increases in intracellular Ca(2+) level upon HIV-1 transactivator of transcription (Tat) exposure. Thus, immature and mature oligodendrocytes can be direct targets of Tat. Since ionotropic glutamate receptor antagonists can partially or fully reverse the detrimental effects of Tat, glutamate receptors could be a potential therapeutic target for white matter damage in HIV patients.
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168
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Scholl C, Kübert N, Muenz TS, Rössler W. CaMKII knockdown affects both early and late phases of olfactory long-term memory in the honeybee. ACTA ACUST UNITED AC 2015; 218:3788-96. [PMID: 26486369 DOI: 10.1242/jeb.124859] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2015] [Accepted: 10/01/2015] [Indexed: 12/11/2022]
Abstract
Honeybees are able to solve complex learning tasks and memorize learned information for long time periods. The molecular mechanisms mediating long-term memory (LTM) in the honeybee Apis mellifera are, to a large part, still unknown. We approached this question by investigating the potential function of the calcium/calmodulin-dependent protein kinase II (CaMKII), an enzyme known as a 'molecular memory switch' in vertebrates. CaMKII is able to switch to a calcium-independent constitutively active state, providing a mechanism for a molecular memory and has further been shown to play an essential role in structural synaptic plasticity. Using a combination of knockdown by RNA interference and pharmacological manipulation, we disrupted the function of CaMKII during olfactory learning and memory formation. We found that learning, memory acquisition and mid-term memory were not affected, but all manipulations consistently resulted in an impaired LTM. Both early LTM (24 h after learning) and late LTM (72 h after learning) were significantly disrupted, indicating the necessity of CaMKII in two successive stages of LTM formation in the honeybee.
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Affiliation(s)
- Christina Scholl
- Behavioral Physiology and Sociobiology (Zoology II), Biozentrum, University of Würzburg, Am Hubland, Würzburg 97074, Germany
| | - Natalie Kübert
- Behavioral Physiology and Sociobiology (Zoology II), Biozentrum, University of Würzburg, Am Hubland, Würzburg 97074, Germany
| | - Thomas S Muenz
- Behavioral Physiology and Sociobiology (Zoology II), Biozentrum, University of Würzburg, Am Hubland, Würzburg 97074, Germany
| | - Wolfgang Rössler
- Behavioral Physiology and Sociobiology (Zoology II), Biozentrum, University of Würzburg, Am Hubland, Würzburg 97074, Germany
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169
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Lussier MP, Sanz-Clemente A, Roche KW. Dynamic Regulation of N-Methyl-d-aspartate (NMDA) and α-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid (AMPA) Receptors by Posttranslational Modifications. J Biol Chem 2015; 290:28596-603. [PMID: 26453298 DOI: 10.1074/jbc.r115.652750] [Citation(s) in RCA: 121] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Many molecular mechanisms underlie the changes in synaptic glutamate receptor content that are required by neuronal networks to generate cellular correlates of learning and memory. During the last decade, posttranslational modifications have emerged as critical regulators of synaptic transmission and plasticity. Notably, phosphorylation, ubiquitination, and palmitoylation control the stability, trafficking, and synaptic expression of glutamate receptors in the central nervous system. In the current review, we will summarize some of the progress made by the neuroscience community regarding our understanding of phosphorylation, ubiquitination, and palmitoylation of the NMDA and AMPA subtypes of glutamate receptors.
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Affiliation(s)
- Marc P Lussier
- From the Département de Chimie, Université du Québec à Montréal, Montréal, Québec H3C 3P8, Canada
| | - Antonio Sanz-Clemente
- the Department of Pharmacology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611, and
| | - Katherine W Roche
- the Receptor Biology Section, NINDS, National Institutes of Health, Bethesda, Maryland 20892
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170
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Ma J, Duan Y, Qin Z, Wang J, Liu W, Xu M, Zhou S, Cao X. Overexpression of αCaMKII impairs behavioral flexibility and NMDAR-dependent long-term depression in the medial prefrontal cortex. Neuroscience 2015; 310:528-40. [PMID: 26415772 DOI: 10.1016/j.neuroscience.2015.09.051] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2015] [Revised: 09/02/2015] [Accepted: 09/20/2015] [Indexed: 01/24/2023]
Abstract
The medial prefrontal cortex (mPFC) participates in the behavioral flexibility. As a major downstream molecule in the NMDA receptor signaling, alpha-Ca(2+)/calmodulin-dependent protein kinase II (αCaMKII) is crucial for hippocampal long-term potentiation (LTP) and hippocampus-related memory. However, the role of αCaMKII in mPFC-related behavioral flexibility and mPFC synaptic plasticity remains elusive. In the present study, using chemical-genetic approaches to temporally up-regulate αCaMKII activity, we found that αCaMKII-F89G transgenic mice exhibited impaired behavioral flexibility in Y-water maze arm reversal task. Notably, in vitro electrophysiological analysis showed normal basal synaptic transmission, LTP and depotentiation, but selectively impaired NMDAR-dependent long-term depression (LTD) in the mPFC of αCaMKII-F89G transgenic mice. In accordance with the deficit in NMDAR-dependent LTD, αCaMKII-F89G transgenic mice exhibited impaired AMPAR internalization during NMDAR-dependent chemical LTD expression in the mPFC. Furthermore, the above deficits in behavioral flexibility, NMDAR-dependent LTD and AMPAR internalization could all be reversed by 1-naphthylmethyl (NM)-PP1, a specific inhibitor of exogenous αCaMKII-F89G activity. Taken together, our results for the first time indicate that αCaMKII overexpression in the forebrain impairs behavioral flexibility and NMDAR-dependent LTD in the mPFC, and supports the notion that there is a close relationship between NMDAR-dependent LTD and behavioral flexibility.
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Affiliation(s)
- J Ma
- Key Laboratory of Brain Functional Genomics (East China Normal University), Ministry of Education, Shanghai Key Laboratory of Brain Functional Genomics (East China Normal University), School of Life Sciences, East China Normal University, 3663 North Zhongshan Road, Shanghai 200062, China
| | - Y Duan
- Key Laboratory of Brain Functional Genomics (East China Normal University), Ministry of Education, Shanghai Key Laboratory of Brain Functional Genomics (East China Normal University), School of Life Sciences, East China Normal University, 3663 North Zhongshan Road, Shanghai 200062, China
| | - Z Qin
- Key Laboratory of Brain Functional Genomics (East China Normal University), Ministry of Education, Shanghai Key Laboratory of Brain Functional Genomics (East China Normal University), School of Life Sciences, East China Normal University, 3663 North Zhongshan Road, Shanghai 200062, China
| | - J Wang
- Key Laboratory of Brain Functional Genomics (East China Normal University), Ministry of Education, Shanghai Key Laboratory of Brain Functional Genomics (East China Normal University), School of Life Sciences, East China Normal University, 3663 North Zhongshan Road, Shanghai 200062, China
| | - W Liu
- Key Laboratory of Brain Functional Genomics (East China Normal University), Ministry of Education, Shanghai Key Laboratory of Brain Functional Genomics (East China Normal University), School of Life Sciences, East China Normal University, 3663 North Zhongshan Road, Shanghai 200062, China
| | - M Xu
- Key Laboratory of Brain Functional Genomics (East China Normal University), Ministry of Education, Shanghai Key Laboratory of Brain Functional Genomics (East China Normal University), School of Life Sciences, East China Normal University, 3663 North Zhongshan Road, Shanghai 200062, China
| | - S Zhou
- Key Laboratory of Brain Functional Genomics (East China Normal University), Ministry of Education, Shanghai Key Laboratory of Brain Functional Genomics (East China Normal University), School of Life Sciences, East China Normal University, 3663 North Zhongshan Road, Shanghai 200062, China
| | - X Cao
- Key Laboratory of Brain Functional Genomics (East China Normal University), Ministry of Education, Shanghai Key Laboratory of Brain Functional Genomics (East China Normal University), School of Life Sciences, East China Normal University, 3663 North Zhongshan Road, Shanghai 200062, China.
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171
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Agoglia AE, Holstein SE, Reid G, Hodge CW. CaMKIIα-GluA1 Activity Underlies Vulnerability to Adolescent Binge Alcohol Drinking. Alcohol Clin Exp Res 2015; 39:1680-90. [PMID: 26247621 DOI: 10.1111/acer.12819] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2015] [Accepted: 06/18/2015] [Indexed: 12/20/2022]
Abstract
BACKGROUND Binge drinking during adolescence is associated with increased risk for developing alcohol use disorders; however, the neural mechanisms underlying this liability are unclear. In this study, we sought to determine whether binge drinking alters expression or phosphorylation of 2 molecular mechanisms of neuroplasticity, calcium/calmodulin-dependent kinase II alpha (CaMKIIα) and the GluA1 subunit of AMPA receptors (AMPARs) in addiction-associated brain regions. We also asked whether activation of CaMKIIα-dependent AMPAR activity escalates binge-like drinking. METHODS To address these questions, CaMKIIαT286 and GluA1S831 protein phosphorylation and expression were assessed in the amygdala and striatum of adolescent and adult male C57BL/6J mice immediately after voluntary binge-like alcohol drinking (blood alcohol >80 mg/dl). In separate mice, effects of the CaMKIIα-dependent GluA1S831 phosphorylation (pGluA1S831 )-enhancing drug tianeptine were tested on binge-like alcohol consumption in both age groups. RESULTS Binge-like drinking decreased CaMKIIαT286 phosphorylation (pCaMKIIαT286 ) selectively in adolescent amygdala with no effect in adults. Alcohol also produced a trend for reduced pGluA1S831 expression in adolescent amygdala but differentially increased pGluA1S831 in adult amygdala. No effects were observed in the nucleus accumbens or dorsal striatum. Tianeptine increased binge-like alcohol consumption in adolescents but decreased alcohol consumption in adults. Sucrose consumption was similarly decreased by tianeptine pretreatment in both ages. CONCLUSIONS These data show that the adolescent and adult amygdalae are differentially sensitive to effects of binge-like alcohol drinking on plasticity-linked glutamate signaling molecules. Tianeptine-induced increases in binge-like drinking only in adolescents suggest that differential CaMKIIα-dependent AMPAR activation may underlie age-related escalation of binge drinking.
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Affiliation(s)
- Abigail E Agoglia
- Bowles Center for Alcohol Studies, University of North Carolina, Chapel Hill, Chapel Hill, North Carolina.,Curriculum in Neurobiology, University of North Carolina, Chapel Hill, Chapel Hill, North Carolina
| | - Sarah E Holstein
- Bowles Center for Alcohol Studies, University of North Carolina, Chapel Hill, Chapel Hill, North Carolina
| | - Grant Reid
- Bowles Center for Alcohol Studies, University of North Carolina, Chapel Hill, Chapel Hill, North Carolina
| | - Clyde W Hodge
- Bowles Center for Alcohol Studies, University of North Carolina, Chapel Hill, Chapel Hill, North Carolina.,Curriculum in Neurobiology, University of North Carolina, Chapel Hill, Chapel Hill, North Carolina.,Department of Psychiatry, University of North Carolina, Chapel Hill, Chapel Hill, North Carolina.,Department of Pharmacology, University of North Carolina, Chapel Hill, Chapel Hill, North Carolina
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172
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Activation of Phosphatidylinositol-Linked Dopamine Receptors Induces a Facilitation of Glutamate-Mediated Synaptic Transmission in the Lateral Entorhinal Cortex. PLoS One 2015; 10:e0131948. [PMID: 26133167 PMCID: PMC4489908 DOI: 10.1371/journal.pone.0131948] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2015] [Accepted: 06/08/2015] [Indexed: 11/19/2022] Open
Abstract
The lateral entorhinal cortex receives strong inputs from midbrain dopamine neurons that can modulate its sensory and mnemonic function. We have previously demonstrated that 1 µM dopamine facilitates synaptic transmission in layer II entorhinal cortex cells via activation of D1-like receptors, increased cAMP-PKA activity, and a resulting enhancement of AMPA-receptor mediated currents. The present study assessed the contribution of phosphatidylinositol (PI)-linked D1 receptors to the dopaminergic facilitation of transmission in layer II of the rat entorhinal cortex, and the involvement of phospholipase C activity and release of calcium from internal stores. Whole-cell patch-clamp recordings of glutamate-mediated evoked excitatory postsynaptic currents were obtained from pyramidal and fan cells. Activation of D1-like receptors using SKF38393, SKF83959, or 1 µM dopamine induced a reversible facilitation of EPSCs which was abolished by loading cells with either the phospholipase C inhibitor U-73122 or the Ca2+ chelator BAPTA. Neither the L-type voltage-gated Ca2+ channel blocker nifedipine, nor the L/N-type channel blocker cilnidipine, blocked the facilitation of synaptic currents. However, the facilitation was blocked by blocking Ca2+ release from internal stores via inositol 1,4,5-trisphosphate (InsP3) receptors or ryanodine receptors. Follow-up studies demonstrated that inhibiting CaMKII activity with KN-93 failed to block the facilitation, but that application of the protein kinase C inhibitor PKC(19-36) completely blocked the dopamine-induced facilitation. Overall, in addition to our previous report indicating a role for the cAMP-PKA pathway in dopamine-induced facilitation of synaptic transmission, we demonstrate here that the dopaminergic facilitation of synaptic responses in layer II entorhinal neurons also relies on a signaling cascade dependent on PI-linked D1 receptors, PLC, release of Ca2+ from internal stores, and PKC activation which is likely dependent upon both DAG and enhanced intracellular Ca2+. These signaling pathways may collaborate to enhance sensory and mnemonic function in the entorhinal cortex during tonic release of dopamine.
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173
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Ghafari M, Keihan Falsafi S, Höger H, Bennett KL, Lubec G. Identification of new phosphorylation sites of AMPA receptors in the rat hippocampus--A resource for neuroscience research. Proteomics Clin Appl 2015; 9:808-16. [PMID: 25656447 DOI: 10.1002/prca.201400057] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2014] [Revised: 10/16/2014] [Accepted: 02/03/2015] [Indexed: 12/14/2022]
Abstract
PURPOSE AMPA (alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid) receptors (AMPARs) are glutamate-gated ion channels that mediate the majority of fast excitatory synaptic transmissions in the mammalian brain. A series of phosphorylation sites have been predicted or identified and knowledge on phosphorylations is mandatory for understanding receptor biology and functions. EXPERIMENTAL DESIGN Immunoprecipitation from extracted hippocampal rat proteins was carried out using an antibody against the AMPAR GluA1 subunit, followed by identification of GluA1 and binding partners by MS. Bands from SDS-PAGE were picked, peptides were generated by trypsin and chymotrypsin digestion and identified by MS/MS (LTQ Orbitrap Velos). RESULTS Using Mascot as a search engine, phosphorylation sites S506, S645, S720, S849, S863, S895, T858, Y228, Y419, and T734 were found on GluA1; S357, S513, S656, S727, T243, T420, T741, Y 143, Y301,Y426 on GluA2; S301, S516, S657, S732, T222, and T746 were observed on GluA3; and S514, S653 was phosphorylated on GluA4. CONCLUSIONS AND CLINICAL RELEVANCE A series of additional protein modifications were observed and in particular, tyrosine and tryptophan nitrations on GluA1 were detected that may raise questions on additional regulation mechanisms for AMPARs in addition to phosphorylations. The findings are relevant for interpretation of previous work and design of future studies using AMPAR serving as a resource for neuroscience research and indeed, phosphorylations and PTMs per se would have to be respected when neuropathological and neurological disorders are being studied.
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Affiliation(s)
- Maryam Ghafari
- Department of Pediatrics, Medical University of Vienna, Vienna, Austria
| | | | - Harald Höger
- Core Unit of Biomedical Research, Division of Laboratory Animal Science and Genetics, Medical University of Vienna, Himberg, Austria
| | - Keiryn L Bennett
- CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences, Vienna, Austria
| | - Gert Lubec
- Department of Pediatrics, Medical University of Vienna, Vienna, Austria
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174
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Kabakov AY, Lisman JE. Catalytically Dead αCaMKII K42M Mutant Acts as a Dominant Negative in the Control of Synaptic Strength. PLoS One 2015; 10:e0123718. [PMID: 25905720 PMCID: PMC4408036 DOI: 10.1371/journal.pone.0123718] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2014] [Accepted: 03/05/2015] [Indexed: 01/17/2023] Open
Abstract
During long-term potentiation (LTP) of excitatory synapses, Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) is activated by Ca(2+) influx through NMDA receptors that potentiate AMPA receptor currents by insertion of additional GluR1-containing receptors at the synapse and by increasing AMPA channel conductance, as well as by stimulating structural changes. CaMKII is also involved in the maintenance of LTP and contributes to maintenance of behavioral sensitization by cocaine or amphetamine. Recent studies show that transient expression of catalytically dead αCaMKII K42M mutant after exposure to amphetamine persistently reverses the behavioral effects of the addiction. A suggested interpretation is that this mutant acts as a dominant negative in the control of synaptic strength, but this interpretation has not been physiologically tested. Here we investigate the effect of αCaMKII K42M mutant expressed in single CA1 pyramidal neurons on basal excitatory neurotransmission in cultured rat hippocampal organotypic slices. The mutant caused nearly 50% reduction in the basal CA3-CA1 transmission, while overexpression of the wild-type αCaMKII had no effect. This result is consistent with the dominant negative hypothesis, but there are complexities. We found that the decrease in basal transmission did not occur when activity in the slices was suppressed after transfection by TTX or when NMDA receptors were blocked by APV. Thus, the dominant negative effect requires neural activity for its expression.
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Affiliation(s)
- Anatoli Y. Kabakov
- Biology Department and Volen Center for Complex Systems, Brandeis University, Waltham, Massachusetts, United States of America
| | - John E. Lisman
- Biology Department and Volen Center for Complex Systems, Brandeis University, Waltham, Massachusetts, United States of America
- * E-mail:
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Viswaprakash N, Vaithianathan T, Viswaprakash A, Judd R, Parameshwaran K, Suppiramaniam V. Insulin treatment restores glutamate (α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid) receptor function in the hippocampus of diabetic rats. J Neurosci Res 2015; 93:1442-50. [PMID: 25807926 DOI: 10.1002/jnr.23589] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2014] [Revised: 12/22/2014] [Accepted: 02/26/2015] [Indexed: 11/10/2022]
Abstract
Type 1 diabetes is associated with cognitive dysfunction. Cognitive processing, particularly memory acquisition, depends on the regulated enhancement of expression and function of glutamate receptor subtypes in the hippocampus. Impairment of memory was been detected in rodent models of type 1 diabetes induced by streptozotocin (STZ). This study examines the functional properties of synaptic α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors and the expression of synaptic molecules that regulate glutamatergic synaptic transmission in the hippocampus of STZ-diabetic rats. The AMPA receptor-mediated miniature excitatory postsynaptic currents (mEPSCs) and single-channel properties of synaptosomal AMPA receptors were examined after 4 weeks of diabetes induction. Results show that amplitude and frequency of mEPSCs recorded from CA1 pyramidal neurons were decreased in diabetic rats. In addition, the single-channel properties of synaptic AMPA receptors from diabetic rat hippocampi were different from those of controls. These impairments in synaptic currents gated by AMPA receptors were accompanied by decreased protein levels of AMPA receptor subunit GluR1, the presynaptic protein synaptophysin, and the postsynaptic anchor protein postsynaptic density protein 95 in the hippocampus of diabetic rats. Neural cell adhesion molecule (NCAM), an extracellular matrix molecule abundantly expressed in the brain, and the polysialic acid (PSA) attached to NCAM were also downregulated in the hippocampus of diabetic rats. Insulin treatment, when initiated at the onset of diabetes induction, reduced these effects. These findings suggest that STZ-induced diabetes may result in functional deteriorations in glutamatergic synapses in the hippocampus of rats and that these effects may be reduced by insulin treatment.
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Affiliation(s)
- Nilmini Viswaprakash
- Department of Biomedical Sciences, College of Veterinary Medicine, Nursing and Allied Health, Tuskegee University, Tuskegee, Alabama
| | - Thirumalini Vaithianathan
- Department of Neurobiology and Behavior, Stony Brook University, Stony Brook, New York.,Department of Drug Discovery and Development, Harrison School of Pharmacy, Auburn University, Auburn, Alabama
| | - Ajitan Viswaprakash
- Biology Department and Spine Rehabilitation Center, University of Alabama-Birmingham, Birmingham, Alabama
| | - Robert Judd
- Department of Anatomy, Physiology and Pharmacology, College of Veterinary Medicine, Auburn University, Auburn, Alabama
| | - Kodeeswaran Parameshwaran
- Department of Drug Discovery and Development, Harrison School of Pharmacy, Auburn University, Auburn, Alabama.,Department of Biological and Environmental Sciences, Texas A&M University-Commerce, Commerce, Texas
| | - Vishnu Suppiramaniam
- Department of Drug Discovery and Development, Harrison School of Pharmacy, Auburn University, Auburn, Alabama
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176
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Abstract
Highlighted in this unit are issues that should be considered when recording glutamate receptors at the single-channel level, including some commonly encountered problems and their remedies. "UNIT 11.17, Single-Channel Analysis of Glutamate Receptors" describes analysis techniques used to characterize the recorded single-channel properties.
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Affiliation(s)
- Chris Shelley
- Department of Neuroscience, Physiology, and Pharmacology, University College London, London, WC1E 6BT, United Kingdom
- Present address: Department of Biology, Franklin and Marshall College, Lancaster, 17604, Pennsylvania
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177
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Gratacòs-Batlle E, Yefimenko N, Cascos-García H, Soto D. AMPAR interacting protein CPT1C enhances surface expression of GluA1-containing receptors. Front Cell Neurosci 2015; 8:469. [PMID: 25698923 PMCID: PMC4313699 DOI: 10.3389/fncel.2014.00469] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2014] [Accepted: 12/29/2014] [Indexed: 11/30/2022] Open
Abstract
AMPARs mediate the vast majority of fast excitatory synaptic transmission in the brain and their biophysical and trafficking properties depend on their subunit composition and on several posttranscriptional and posttranslational modifications. Additionally, in the brain AMPARs associate with auxiliary subunits, which modify the properties of the receptors. Despite the abundance of AMPAR partners, recent proteomic studies have revealed even more interacting proteins that could potentially be involved in AMPAR regulation. Amongst these, carnitine palmitoyltransferase 1C (CPT1C) has been demonstrated to form an integral part of native AMPAR complexes in brain tissue extracts. Thus, we aimed to investigate whether CPT1C might be able to modulate AMPAR function. Firstly, we confirmed that CPT1C is an interacting protein of AMPARs in heterologous expression systems. Secondly, CPT1C enhanced whole-cell currents of GluA1 homomeric and GluA1/GluA2 heteromeric receptors. However, CPT1C does not alter the biophysical properties of AMPARs and co-localization experiments revealed that AMPARs and CPT1C are not associated at the plasma membrane despite a strong level of co-localization at the intracellular level. We established that increased surface GluA1 receptor number was responsible for the enhanced AMPAR mediated currents in the presence of CPT1C. Additionally, we revealed that the palmitoylable residue C585 of GluA1 is important in the enhancement of AMPAR trafficking to the cell surface by CPT1C. Nevertheless, despite its potential as a depalmitoylating enzyme, CPT1C does not affect the palmitoylation state of GluA1. To sum up, this work suggests that CPT1C plays a role as a novel regulator of AMPAR surface expression in neurons. Fine modulation of AMPAR membrane trafficking is fundamental in normal synaptic activity and in plasticity processes and CPT1C is therefore a putative candidate to regulate neuronal AMPAR physiology.
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Affiliation(s)
- Esther Gratacòs-Batlle
- Laboratori de Neurobiologia, Area de Neurobiologia Cellular i Molecular, Institut d'Investigació Biomèdica de Bellvitge-IDIBELL L'Hospitalet de Llobregat, Spain ; Department of Pathology and Experimental Therapeutics, Faculty of Medicine, University of Barcelona L'Hospitalet de Llobregat, Spain
| | - Natalia Yefimenko
- Laboratori de Neurobiologia, Area de Neurobiologia Cellular i Molecular, Institut d'Investigació Biomèdica de Bellvitge-IDIBELL L'Hospitalet de Llobregat, Spain ; Department of Pathology and Experimental Therapeutics, Faculty of Medicine, University of Barcelona L'Hospitalet de Llobregat, Spain
| | - Helena Cascos-García
- Laboratori de Neurobiologia, Area de Neurobiologia Cellular i Molecular, Institut d'Investigació Biomèdica de Bellvitge-IDIBELL L'Hospitalet de Llobregat, Spain ; Department of Pathology and Experimental Therapeutics, Faculty of Medicine, University of Barcelona L'Hospitalet de Llobregat, Spain
| | - David Soto
- Laboratori de Neurobiologia, Area de Neurobiologia Cellular i Molecular, Institut d'Investigació Biomèdica de Bellvitge-IDIBELL L'Hospitalet de Llobregat, Spain ; Department of Pathology and Experimental Therapeutics, Faculty of Medicine, University of Barcelona L'Hospitalet de Llobregat, Spain
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178
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Garcia-Alvarez G, Lu B, Yap KAF, Wong LC, Thevathasan JV, Lim L, Ji F, Tan KW, Mancuso JJ, Tang W, Poon SY, Augustine GJ, Fivaz M. STIM2 regulates PKA-dependent phosphorylation and trafficking of AMPARs. Mol Biol Cell 2015; 26:1141-59. [PMID: 25609091 PMCID: PMC4357513 DOI: 10.1091/mbc.e14-07-1222] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
STIMs (STIM1 and STIM2 in mammals) are transmembrane proteins that reside in the endoplasmic reticulum and regulate store-operated Ca2+ entry. STIM2 mediates cAMP/PKA-dependent phosphorylation of the AMPA receptor subunit GluA1 in excitatory neurons. In addition, STIM2 promotes cAMP-dependent surface delivery of GluA1. STIMs (STIM1 and STIM2 in mammals) are transmembrane proteins that reside in the endoplasmic reticulum (ER) and regulate store-operated Ca2+ entry (SOCE). The function of STIMs in the brain is only beginning to be explored, and the relevance of SOCE in nerve cells is being debated. Here we identify STIM2 as a central organizer of excitatory synapses. STIM2, but not its paralogue STIM1, influences the formation of dendritic spines and shapes basal synaptic transmission in excitatory neurons. We further demonstrate that STIM2 is essential for cAMP/PKA-dependent phosphorylation of the AMPA receptor (AMPAR) subunit GluA1. cAMP triggers rapid migration of STIM2 to ER–plasma membrane (PM) contact sites, enhances recruitment of GluA1 to these ER-PM junctions, and promotes localization of STIM2 in dendritic spines. Both biochemical and imaging data suggest that STIM2 regulates GluA1 phosphorylation by coupling PKA to the AMPAR in a SOCE-independent manner. Consistent with a central role of STIM2 in regulating AMPAR phosphorylation, STIM2 promotes cAMP-dependent surface delivery of GluA1 through combined effects on exocytosis and endocytosis. Collectively our results point to a unique mechanism of synaptic plasticity driven by dynamic assembly of a STIM2 signaling complex at ER-PM contact sites.
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Affiliation(s)
- Gisela Garcia-Alvarez
- Program in Neuroscience and Behavioral Disorders, DUKE-NUS Graduate Medical School, Singapore 169857
| | - Bo Lu
- Program in Neuroscience and Behavioral Disorders, DUKE-NUS Graduate Medical School, Singapore 169857
| | - Kenrick An Fu Yap
- Program in Neuroscience and Behavioral Disorders, DUKE-NUS Graduate Medical School, Singapore 169857
| | - Loo Chin Wong
- Program in Neuroscience and Behavioral Disorders, DUKE-NUS Graduate Medical School, Singapore 169857
| | - Jervis Vermal Thevathasan
- Program in Neuroscience and Behavioral Disorders, DUKE-NUS Graduate Medical School, Singapore 169857
| | - Lynette Lim
- Program in Neuroscience and Behavioral Disorders, DUKE-NUS Graduate Medical School, Singapore 169857
| | - Fang Ji
- Program in Neuroscience and Behavioral Disorders, DUKE-NUS Graduate Medical School, Singapore 169857
| | - Kia Wee Tan
- Program in Neuroscience and Behavioral Disorders, DUKE-NUS Graduate Medical School, Singapore 169857
| | - James J Mancuso
- Program in Neuroscience and Behavioral Disorders, DUKE-NUS Graduate Medical School, Singapore 169857
| | - Willcyn Tang
- Program in Neuroscience and Behavioral Disorders, DUKE-NUS Graduate Medical School, Singapore 169857
| | - Shou Yu Poon
- Program in Neuroscience and Behavioral Disorders, DUKE-NUS Graduate Medical School, Singapore 169857
| | - George J Augustine
- Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore 637553 Center for Functional Connectomics, Korea Institute of Science and Technology, Seoul 136-791, Republic of Korea
| | - Marc Fivaz
- Program in Neuroscience and Behavioral Disorders, DUKE-NUS Graduate Medical School, Singapore 169857 Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 117597
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179
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Parihar VK, Allen BD, Tran KK, Chmielewski NN, Craver BM, Martirosian V, Morganti JM, Rosi S, Vlkolinsky R, Acharya MM, Nelson GA, Allen AR, Limoli CL. Targeted overexpression of mitochondrial catalase prevents radiation-induced cognitive dysfunction. Antioxid Redox Signal 2015; 22:78-91. [PMID: 24949841 PMCID: PMC4270160 DOI: 10.1089/ars.2014.5929] [Citation(s) in RCA: 68] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
AIMS Radiation-induced disruption of mitochondrial function can elevate oxidative stress and contribute to the metabolic perturbations believed to compromise the functionality of the central nervous system. To clarify the role of mitochondrial oxidative stress in mediating the adverse effects of radiation in the brain, we analyzed transgenic (mitochondrial catalase [MCAT]) mice that overexpress human catalase localized to the mitochondria. RESULTS Compared with wild-type (WT) controls, overexpression of the MCAT transgene significantly decreased cognitive dysfunction after proton irradiation. Significant improvements in behavioral performance found on novel object recognition and object recognition in place tasks were associated with a preservation of neuronal morphology. While the architecture of hippocampal CA1 neurons was significantly compromised in irradiated WT mice, the same neurons in MCAT mice did not exhibit extensive and significant radiation-induced reductions in dendritic complexity. Irradiated neurons from MCAT mice maintained dendritic branching and length compared with WT mice. Protected neuronal morphology in irradiated MCAT mice was also associated with a stabilization of radiation-induced variations in long-term potentiation. Stabilized synaptic activity in MCAT mice coincided with an altered composition of the synaptic AMPA receptor subunits GluR1/2. INNOVATION Our findings provide the first evidence that neurocognitive sequelae associated with radiation exposure can be reduced by overexpression of MCAT, operating through a mechanism involving the preservation of neuronal morphology. CONCLUSION Our article documents the neuroprotective properties of reducing mitochondrial reactive oxygen species through the targeted overexpression of catalase and how this ameliorates the adverse effects of proton irradiation in the brain.
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Affiliation(s)
- Vipan K. Parihar
- Department of Radiation Oncology, University of California, Irvine, Irvine, California
| | - Barrett D. Allen
- Department of Radiation Oncology, University of California, Irvine, Irvine, California
| | - Katherine K. Tran
- Department of Radiation Oncology, University of California, Irvine, Irvine, California
| | - Nicole N. Chmielewski
- Department of Radiation Oncology, University of California, Irvine, Irvine, California
| | - Brianna M. Craver
- Department of Radiation Oncology, University of California, Irvine, Irvine, California
| | - Vahan Martirosian
- Department of Radiation Oncology, University of California, Irvine, Irvine, California
| | - Josh M. Morganti
- Departments of Physical Therapy Rehabilitation Science and Neurological Surgery, University of California, San Francisco, San Francisco, California
| | - Susanna Rosi
- Departments of Physical Therapy Rehabilitation Science and Neurological Surgery, University of California, San Francisco, San Francisco, California
- Brain and Spinal Injury Center, University of California, San Francisco, San Francisco, California
| | - Roman Vlkolinsky
- Departments of Radiation Medicine and Basic Sciences, Loma Linda University, Loma Linda, California
| | - Munjal M. Acharya
- Department of Radiation Oncology, University of California, Irvine, Irvine, California
| | - Gregory A. Nelson
- Departments of Radiation Medicine and Basic Sciences, Loma Linda University, Loma Linda, California
| | - Antiño R. Allen
- Division of Radiation Health, University of Arkansas Medical School, Little Rock, Arkansas
| | - Charles L. Limoli
- Department of Radiation Oncology, University of California, Irvine, Irvine, California
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180
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Ménard C, Gaudreau P, Quirion R. Signaling pathways relevant to cognition-enhancing drug targets. Handb Exp Pharmacol 2015; 228:59-98. [PMID: 25977080 DOI: 10.1007/978-3-319-16522-6_3] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Aging is generally associated with a certain cognitive decline. However, individual differences exist. While age-related memory deficits can be observed in humans and rodents in the absence of pathological conditions, some individuals maintain intact cognitive functions up to an advanced age. The mechanisms underlying learning and memory processes involve the recruitment of multiple signaling pathways and gene expression, leading to adaptative neuronal plasticity and long-lasting changes in brain circuitry. This chapter summarizes the current understanding of how these signaling cascades could be modulated by cognition-enhancing agents favoring memory formation and successful aging. It focuses on data obtained in rodents, particularly in the rat as it is the most common animal model studied in this field. First, we will discuss the role of the excitatory neurotransmitter glutamate and its receptors, downstream signaling effectors [e.g., calcium/calmodulin-dependent protein kinase II (CaMKII), protein kinase C (PKC), extracellular signal-regulated kinases (ERK), mammalian target of rapamycin (mTOR), cAMP response element-binding protein (CREB)], associated immediate early gene (e.g., Homer 1a, Arc and Zif268), and growth factors [insulin-like growth factors (IGFs) and brain-derived neurotrophic factor (BDNF)] in synaptic plasticity and memory formation. Second, the impact of the cholinergic system and related modulators on memory will be briefly reviewed. Finally, since dynorphin neuropeptides have recently been associated with memory impairments in aging, it is proposed as an attractive target to develop novel cognition-enhancing agents.
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Affiliation(s)
- Caroline Ménard
- Douglas Mental Health University Institute, McGill University, Perry Pavilion, 6875 LaSalle Boulevard, Montreal, QC, Canada, H4H 1R3
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181
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Hosokawa T, Mitsushima D, Kaneko R, Hayashi Y. Stoichiometry and phosphoisotypes of hippocampal AMPA-type glutamate receptor phosphorylation. Neuron 2014; 85:60-67. [PMID: 25533481 DOI: 10.1016/j.neuron.2014.11.026] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/13/2014] [Indexed: 01/18/2023]
Abstract
It has been proposed that the AMPAR phosphorylation regulates trafficking and channel activity, thereby playing an important role in synaptic plasticity. However, the actual stoichiometry of phosphorylation, information critical to understand the role of phosphorylation, is not known because of the lack of appropriate techniques for measurement. Here, using Phos-tag SDS-PAGE, we estimated the proportion of phosphorylated AMPAR subunit GluA1. The level of phosphorylated GluA1 at S831 and S845, two major sites implicated in AMPAR regulation, is almost negligible. Less than 1% of GluA1 is phosphorylated at S831 and less than 0.1% at S845. Considering the number of AMPAR at each synapse, the majority of synapses do not contain any phosphorylated AMPAR. Also, we did not see evidence of GluA1 dually phosphorylated at S831 and S845. Neuronal stimulation and learning increased phosphorylation, but the proportion was still low. Our results impel us to reconsider the mechanisms underlying synaptic plasticity.
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Affiliation(s)
| | - Dai Mitsushima
- Department of Physiology, Yokohama City University Graduate School of Medicine, Yokohama, Kanagawa 236-0004, Japan; Department of Systems Neuroscience, Yamaguchi University Graduate School of Medicine, Ube, Yamaguchi 755-8505, Japan
| | - Rina Kaneko
- Brain Science Institute, RIKEN, Wako, Saitama 351-0198, Japan
| | - Yasunori Hayashi
- Brain Science Institute, RIKEN, Wako, Saitama 351-0198, Japan; Saitama University Brain Science Institute, Saitama University, Saitama 338-8570, Japan.
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182
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Lussier MP, Gu X, Lu W, Roche KW. Casein kinase 2 phosphorylates GluA1 and regulates its surface expression. Eur J Neurosci 2014; 39:1148-58. [PMID: 24712994 DOI: 10.1111/ejn.12494] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2013] [Revised: 12/17/2013] [Accepted: 01/02/2014] [Indexed: 11/30/2022]
Abstract
Controlling the density of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPARs) at synapses is essential for regulating the strength of excitatory neurotransmission. In particular, the phosphorylation of AMPARs is important for defining both synaptic expression and intracellular routing of receptors. Phosphorylation is a post-translational modification known to regulate many cellular events and the C-termini of glutamate receptors are important targets. Recently, the first intracellular loop1 region of the GluA1 subunit of AMPARs was reported to regulate synaptic targeting through phosphorylation of S567 by Ca2+ /calmodulin-dependent protein kinase II (CaMKII). Intriguingly, the loop1 region of all four AMPAR subunits contains many putative phosphorylation sites (S/T/Y), leaving the possibility that other kinases may regulate AMPAR surface expression via phosphorylation of the loop regions. To explore this hypothesis, we used in vitro phosphorylation assays with a small panel of purified kinases and found that casein kinase 2 (CK2) phosphorylates the GluA1 and GluA2 loop1 regions, but not GluA3 or GluA4. Interestingly, when we reduced the endogenous expression of CK2 using a specific short hairpin RNA against the regulatory subunit CK2β, we detected a reduction of GluA1 surface expression, whereas GluA2 was unchanged. Furthermore, we identified S579 of GluA1 as a substrate of CK2, and the expression of GluA1 phosphodeficient mutants in hippocampal neurons displayed reduced surface expression. Therefore, our study identifies CK2 as a regulator of GluA1 surface expression by phosphorylating the intracellular loop1 region.
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Affiliation(s)
- Marc P Lussier
- Receptor Biology Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, 20892, USA
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183
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Gan M, Jiang P, McLean P, Kanekiyo T, Bu G. Low-density lipoprotein receptor-related protein 1 (LRP1) regulates the stability and function of GluA1 α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptor in neurons. PLoS One 2014; 9:e113237. [PMID: 25500815 PMCID: PMC4264746 DOI: 10.1371/journal.pone.0113237] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2014] [Accepted: 10/23/2014] [Indexed: 11/18/2022] Open
Abstract
The low-density lipoprotein receptor-related protein 1 (LRP1) is a multifunctional endocytic receptor abundantly expressed in neurons. Increasing evidence demonstrates that LRP1 regulates synaptic integrity and function at the post synapses, at least partially by regulating glutamate receptors. The α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid receptors (AMPARs) are critical ionotropic glutamate receptors consisting of homotetramer or heterotetramer of GluA1-4 subunits and play an essential role in synaptic transmission and synaptic plasticity. Our previous work has shown that neuronal deletion of the Lrp1 gene in mice leads to decreased level of GluA1 and reduced long-term potentiation. To understand the underlying mechanism, we investigated the cellular and functional consequences of LRP1 deletion in primary neurons. Here, we show that LRP1 interacts with and regulates the cellular distribution and turnover of GluA1. LRP1 knockdown in mouse primary neurons led to accelerated turnover and decreased cell surface distribution of GluA1, which correspond to decreased phosphorylation of GluA1 at S845 and S831 sites. Decreased LRP1 expression also attenuated AMPA-evoked calcium influx and reduced GluA1-regulated neurite outgrowth and filopodia density. Our results reveal a novel mechanism by which LRP1 controls synaptic integrity and function, specifically by regulating GluA1 trafficking, phosphorylation and turnover. They further demonstrate that LRP1-GluA1 pathway may hold promises as a therapeutic target for restoring synaptic functions in neurodegenerative diseases.
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Affiliation(s)
- Ming Gan
- Department of Neuroscience, Mayo Clinic, Jacksonville, Florida, United States of America
| | - Peizhou Jiang
- Department of Neuroscience, Mayo Clinic, Jacksonville, Florida, United States of America
| | - Pamela McLean
- Department of Neuroscience, Mayo Clinic, Jacksonville, Florida, United States of America
| | - Takahisa Kanekiyo
- Department of Neuroscience, Mayo Clinic, Jacksonville, Florida, United States of America
| | - Guojun Bu
- Department of Neuroscience, Mayo Clinic, Jacksonville, Florida, United States of America; Fujian Provincial Key Laboratory of Neurodegenerative Disease and Aging Research, Institute of Neuroscience, College of Medicine, Xiamen University, Xiamen, China
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184
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Chater TE, Goda Y. The role of AMPA receptors in postsynaptic mechanisms of synaptic plasticity. Front Cell Neurosci 2014; 8:401. [PMID: 25505875 PMCID: PMC4245900 DOI: 10.3389/fncel.2014.00401] [Citation(s) in RCA: 209] [Impact Index Per Article: 20.9] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2014] [Accepted: 11/06/2014] [Indexed: 11/21/2022] Open
Abstract
In the mammalian central nervous system, excitatory glutamatergic synapses harness neurotransmission that is mediated by ion flow through α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPARs). AMPARs, which are enriched in the postsynaptic membrane on dendritic spines, are highly dynamic, and shuttle in and out of synapses in an activity-dependent manner. Changes in their number, subunit composition, phosphorylation state, and accessory proteins can all regulate AMPARs and thus modify synaptic strength and support cellular forms of learning. Furthermore, dysregulation of AMPAR plasticity has been implicated in various pathological states and has important consequences for mental health. Here we focus on the mechanisms that control AMPAR plasticity, drawing particularly from the extensive studies on hippocampal synapses, and highlight recent advances in the field along with considerations for future directions.
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Affiliation(s)
| | - Yukiko Goda
- RIKEN, Brain Science Institute Wako-shi, Japan
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185
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Diering GH, Gustina AS, Huganir RL. PKA-GluA1 coupling via AKAP5 controls AMPA receptor phosphorylation and cell-surface targeting during bidirectional homeostatic plasticity. Neuron 2014; 84:790-805. [PMID: 25451194 PMCID: PMC4254581 DOI: 10.1016/j.neuron.2014.09.024] [Citation(s) in RCA: 110] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/03/2014] [Indexed: 11/29/2022]
Abstract
Bidirectional synaptic plasticity occurs locally at individual synapses during long-term potentiation (LTP) or long-term depression (LTD), or globally during homeostatic scaling. LTP, LTD, and homeostatic scaling alter synaptic strength through changes in postsynaptic AMPA-type glutamate receptors (AMPARs), suggesting the existence of overlapping molecular mechanisms. Phosphorylation controls AMPAR trafficking during LTP/LTD. We addressed the role of AMPAR phosphorylation during homeostatic scaling. We observed bidirectional changes of the levels of phosphorylated GluA1 S845 during scaling, resulting from a loss of protein kinase A (PKA) from synapses during scaling down and enhanced activity of PKA in synapses during scaling up. Increased phosphorylation of S845 drove scaling up, while a knockin mutation of S845, or knockdown of the scaffold AKAP5, blocked scaling up. Finally, we show that AMPARs scale differentially based on their phosphorylation status at S845. These results show that rearrangement in PKA signaling controls AMPAR phosphorylation and surface targeting during homeostatic plasticity.
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Affiliation(s)
- Graham H Diering
- Department of Neuroscience and Howard Hughes Medical Institute, Johns Hopkins University School of Medicine, Hunterian 1001, 725 North Wolfe Street, Baltimore, MD 21205, USA
| | - Ahleah S Gustina
- Department of Neuroscience and Howard Hughes Medical Institute, Johns Hopkins University School of Medicine, Hunterian 1001, 725 North Wolfe Street, Baltimore, MD 21205, USA
| | - Richard L Huganir
- Department of Neuroscience and Howard Hughes Medical Institute, Johns Hopkins University School of Medicine, Hunterian 1001, 725 North Wolfe Street, Baltimore, MD 21205, USA.
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186
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He Y, Kulasiri D, Samarasinghe S. Modelling the dynamics of CaMKII-NMDAR complex related to memory formation in synapses: the possible roles of threonine 286 autophosphorylation of CaMKII in long term potentiation. J Theor Biol 2014; 365:403-19. [PMID: 25446714 DOI: 10.1016/j.jtbi.2014.11.001] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2014] [Revised: 10/31/2014] [Accepted: 11/03/2014] [Indexed: 10/24/2022]
Abstract
A synaptic protein, Ca(2+)/Calmodulin dependent protein kinase II (CaMKII), has complex state transitions and facilitates the emergence of long term potentiation (LTP), which is highly correlated to memory formation. Two of the state transitions are critical for LTP: (1) threonine 286 autophosphorylation of CaMKII; and (2) binding to N-methyl-d-aspartate receptor (NMDAR) in the postsynaptic density (PSD) to form CaMKII-NMDAR complex. Both of these state transitions retain the activity of CaMKII when the induction signal disappears which is very important for the long-lasting characteristics of LTP. However, the possible relationships between the state transitions in the emergence of LTP are not well understood. We develop a mathematical model of the formation of CaMKII-NMDAR complex with the full state transitions of CaMKII, including the autophosphorylation, based on ordinary differential equations. In addition, we formulate a probabilistic framework for the binding between CaMKII and NMDAR. The model gives accurate predictions of the behaviours of CaMKII in comparisons to the experimental observations. Using the model, we show that: (1) the formation of CaMKII-NMDAR complex is dependent not only on the binding affinity between CaMKII and NMDAR, but also on the translocation of CaMKII into PSD; and (2) the autophosphorylation is not a requirement for the formation of CaMKII-NMDAR complex, but is important for the rapid formation of CaMKII-NMDAR complex during LTP.
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Affiliation(s)
- Y He
- Centre for Advanced Computational Solutions (C-fACS), Department of Molecular Biosciences, Lincoln University, Christchurch, New Zealand
| | - D Kulasiri
- Centre for Advanced Computational Solutions (C-fACS), Department of Molecular Biosciences, Lincoln University, Christchurch, New Zealand.
| | - S Samarasinghe
- Centre for Advanced Computational Solutions (C-fACS), Department of Molecular Biosciences, Lincoln University, Christchurch, New Zealand
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187
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Conditional deletion of α-CaMKII impairs integration of adult-generated granule cells into dentate gyrus circuits and hippocampus-dependent learning. J Neurosci 2014; 34:11919-28. [PMID: 25186740 DOI: 10.1523/jneurosci.0652-14.2014] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
New granule cells are continuously integrated into hippocampal circuits throughout adulthood, and the fine-tuning of this process is likely important for efficient hippocampal function. During development, this integration process is critically regulated by the α-calcium/calmodulin-dependent protein kinase II (α-CaMKII), and here we ask whether this role is conserved in the adult brain. To do this, we developed a transgenic strategy to conditionally delete α-CaMKII from neural progenitor cells and their progeny in adult mice. First, we found that the selective deletion of α-CaMKII from newly generated dentate granule cells led to an increase in dendritic complexity. Second, α-CaMKII deletion led to a reduction in number of mature synapses and cell survival. Third, consistent with altered morphological and synaptic development, acquisition of one-trial contextual fear conditioning was impaired after deletion of α-CaMKII from newly generated dentate granule cells. Previous work in Xenopus identified α-CaMKII as playing a key role in the stabilization of dendritic and synaptic structure during development. The current study indicates that α-CaMKII plays a plays a similar, cell-autonomous role in the adult hippocampus and, in addition, reveals that the loss of α-CaMKII from adult-generated granule cells is associated with impaired hippocampus-dependent learning.
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188
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Olivito L, Saccone P, Perri V, Bachman JL, Fragapane P, Mele A, Huganir RL, De Leonibus E. Phosphorylation of the AMPA receptor GluA1 subunit regulates memory load capacity. Brain Struct Funct 2014; 221:591-603. [PMID: 25381005 PMCID: PMC4425615 DOI: 10.1007/s00429-014-0927-1] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2014] [Accepted: 10/17/2014] [Indexed: 01/13/2023]
Abstract
Memory capacity (MC) refers to the number of elements one can maintain for a short retention interval. The molecular mechanisms underlying MC are unexplored. We have recently reported that mice as well as humans have a limited MC, which is reduced by hippocampal lesions. Here, we addressed the molecular mechanisms supporting MC. GluA1 AMPA-receptors (AMPA-R) mediate the majority of fast excitatory synaptic transmission in the brain and are critically involved in memory. Phosphorylation of GluA1 at serine residues S831 and S845 is promoted by CaMKII and PKA, respectively, and regulates AMPA-R function in memory duration. We hypothesized that AMPA-R phosphorylation may also be a key plastic process for supporting MC because it occurs in a few minutes, and potentiates AMPA-R ion channel function. Here, we show that knock-in mutant mice that specifically lack both of S845 and S831 phosphorylation sites on the GluA1 subunit had reduced MC in two different behavioral tasks specifically designed to assess MC in mice. This demonstrated a causal link between AMPA-R phosphorylation and MC. We then showed that information load regulates AMPA-R phosphorylation within the hippocampus, and that an overload condition associated with impaired memory is paralleled by a lack of AMPA-R phosphorylation. Accordingly, we showed that in conditions of high load, but not of low load, the pharmacological inhibition of the NMDA–CaMKII–PKA pathways within the hippocampus prevents memory as well as associated AMPA-R phosphorylation. These data provide the first identified molecular mechanism that regulates MC.
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Affiliation(s)
- Laura Olivito
- Institute of Genetics and Biophysics, CNR, Via P. Castellino 111, 80131, Naples, Italy
| | - Paola Saccone
- Telethon Institute of Genetics and Medicine (TIGEM), Naples, Italy
| | - Valentina Perri
- Dipartimento di Biologia e Biotecnologie, Università degli Studi di Roma "La Sapienza", Rome, Italy
- Centro di Ricerca in Neurobiologia-D. Bovet, Università degli Studi di Roma "La Sapienza", Rome, Italy
| | - Julia L Bachman
- Department of Neuroscience and Howard Hughes Medical Institute, Johns Hopkins University School of Medicine, Hunterian 1001, 725 North Wolfe Street, Baltimore, MD, 21205, USA
| | - Paola Fragapane
- Istituto di Biologia e Patologia Molecolare, CNR, Rome, Italy
| | - Andrea Mele
- Dipartimento di Biologia e Biotecnologie, Università degli Studi di Roma "La Sapienza", Rome, Italy
- Centro di Ricerca in Neurobiologia-D. Bovet, Università degli Studi di Roma "La Sapienza", Rome, Italy
| | - Richard L Huganir
- Department of Neuroscience and Howard Hughes Medical Institute, Johns Hopkins University School of Medicine, Hunterian 1001, 725 North Wolfe Street, Baltimore, MD, 21205, USA
| | - Elvira De Leonibus
- Institute of Genetics and Biophysics, CNR, Via P. Castellino 111, 80131, Naples, Italy.
- Telethon Institute of Genetics and Medicine (TIGEM), Naples, Italy.
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189
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Van Hook MJ, Parmelee CM, Chen M, Cork KM, Curto C, Thoreson WB. Calmodulin enhances ribbon replenishment and shapes filtering of synaptic transmission by cone photoreceptors. ACTA ACUST UNITED AC 2014; 144:357-78. [PMID: 25311636 PMCID: PMC4210432 DOI: 10.1085/jgp.201411229] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
At the first synapse in the vertebrate visual pathway, light-evoked changes in photoreceptor membrane potential alter the rate of glutamate release onto second-order retinal neurons. This process depends on the synaptic ribbon, a specialized structure found at various sensory synapses, to provide a supply of primed vesicles for release. Calcium (Ca(2+)) accelerates the replenishment of vesicles at cone ribbon synapses, but the mechanisms underlying this acceleration and its functional implications for vision are unknown. We studied vesicle replenishment using paired whole-cell recordings of cones and postsynaptic neurons in tiger salamander retinas and found that it involves two kinetic mechanisms, the faster of which was diminished by calmodulin (CaM) inhibitors. We developed an analytical model that can be applied to both conventional and ribbon synapses and showed that vesicle resupply is limited by a simple time constant, τ = 1/(Dρδs), where D is the vesicle diffusion coefficient, δ is the vesicle diameter, ρ is the vesicle density, and s is the probability of vesicle attachment. The combination of electrophysiological measurements, modeling, and total internal reflection fluorescence microscopy of single synaptic vesicles suggested that CaM speeds replenishment by enhancing vesicle attachment to the ribbon. Using electroretinogram and whole-cell recordings of light responses, we found that enhanced replenishment improves the ability of cone synapses to signal darkness after brief flashes of light and enhances the amplitude of responses to higher-frequency stimuli. By accelerating the resupply of vesicles to the ribbon, CaM extends the temporal range of synaptic transmission, allowing cones to transmit higher-frequency visual information to downstream neurons. Thus, the ability of the visual system to encode time-varying stimuli is shaped by the dynamics of vesicle replenishment at photoreceptor synaptic ribbons.
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Affiliation(s)
- Matthew J Van Hook
- Department of Ophthalmology and Visual Sciences and Department of Pharmacology and Experimental Neuroscience, University of Nebraska Medical Center, Omaha, NE 68198
| | - Caitlyn M Parmelee
- Department of Mathematics, University of Nebraska-Lincoln, Lincoln, NE 68588
| | - Minghui Chen
- Department of Ophthalmology and Visual Sciences and Department of Pharmacology and Experimental Neuroscience, University of Nebraska Medical Center, Omaha, NE 68198 Department of Ophthalmology and Visual Sciences and Department of Pharmacology and Experimental Neuroscience, University of Nebraska Medical Center, Omaha, NE 68198
| | - Karlene M Cork
- Department of Ophthalmology and Visual Sciences and Department of Pharmacology and Experimental Neuroscience, University of Nebraska Medical Center, Omaha, NE 68198 Department of Ophthalmology and Visual Sciences and Department of Pharmacology and Experimental Neuroscience, University of Nebraska Medical Center, Omaha, NE 68198
| | - Carina Curto
- Department of Mathematics, University of Nebraska-Lincoln, Lincoln, NE 68588 Department of Mathematics, The Pennsylvania State University, University Park, State College, PA 16802
| | - Wallace B Thoreson
- Department of Ophthalmology and Visual Sciences and Department of Pharmacology and Experimental Neuroscience, University of Nebraska Medical Center, Omaha, NE 68198 Department of Ophthalmology and Visual Sciences and Department of Pharmacology and Experimental Neuroscience, University of Nebraska Medical Center, Omaha, NE 68198
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190
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Prolonged adenosine A1 receptor activation in hypoxia and pial vessel disruption focal cortical ischemia facilitates clathrin-mediated AMPA receptor endocytosis and long-lasting synaptic inhibition in rat hippocampal CA3-CA1 synapses: differential regulation of GluA2 and GluA1 subunits by p38 MAPK and JNK. J Neurosci 2014; 34:9621-43. [PMID: 25031403 DOI: 10.1523/jneurosci.3991-13.2014] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Activation of presynaptic adenosine A1 receptors (A1Rs) causes substantial synaptic depression during hypoxia/cerebral ischemia, but postsynaptic actions of A1Rs are less clear. We found that A1Rs and GluA2-containing AMPA receptors (AMPARs) form stable protein complexes from hippocampal brain homogenates and cultured hippocampal neurons from Sprague Dawley rats. In contrast, adenosine A2A receptors (A2ARs) did not coprecipitate or colocalize with GluA2-containing AMPARs. Prolonged stimulation of A1Rs with the agonist N(6)-cyclopentyladenosine (CPA) caused adenosine-induced persistent synaptic depression (APSD) in hippocampal brain slices, and APSD levels were blunted by inhibiting clathrin-mediated endocytosis of GluA2 subunits with the Tat-GluA2-3Y peptide. Using biotinylation and membrane fractionation assays, prolonged CPA incubation showed significant depletion of GluA2/GluA1 surface expression from hippocampal brain slices and cultured neurons. Tat-GluA2-3Y peptide or dynamin inhibitor Dynasore prevented CPA-induced GluA2/GluA1 internalization. Confocal imaging analysis confirmed that functional A1Rs, but not A2ARs, are required for clathrin-mediated AMPAR endocytosis in hippocampal neurons. Pharmacological inhibitors or shRNA knockdown of p38 MAPK and JNK prevented A1R-mediated internalization of GluA2 but not GluA1 subunits. Tat-GluA2-3Y peptide or A1R antagonist 8-cyclopentyl-1,3-dipropylxanthine also prevented hypoxia-mediated GluA2/GluA1 internalization. Finally, in a pial vessel disruption cortical stroke model, a unilateral cortical lesion compared with sham surgery reduced hippocampal GluA2, GluA1, and A1R surface expression and also caused synaptic depression in hippocampal slices that was consistent with AMPAR downregulation and decreased probability of transmitter release. Together, these results indicate a previously unknown mechanism for A1R-induced persistent synaptic depression involving clathrin-mediated GluA2 and GluA1 internalization that leads to hippocampal neurodegeneration after hypoxia/cerebral ischemia.
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191
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Mao LM, Jin DZ, Xue B, Chu XP, Wang JQ. Phosphorylation and regulation of glutamate receptors by CaMKII. SHENG LI XUE BAO : [ACTA PHYSIOLOGICA SINICA] 2014; 66:365-372. [PMID: 24964855 PMCID: PMC4435801] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Ca²⁺/calmodulin-dependent protein kinase II (CaMKII) is the most abundant kinase within excitatory synapses in the mammalian brain. It interacts with and phosphorylates a large number of synaptic proteins, including major ionotropic glutamate receptors (iGluRs) and group I metabotropic glutamate receptors (mGluRs), to constitutively and/or activity-dependently regulate trafficking, subsynaptic localization, and function of the receptors. Among iGluRs, the N-methyl-D-aspartate receptor (NMDAR) is a direct target of CaMKII. By directly binding to an intracellular C-terminal (CT) region of NMDAR GluN2B subunits, CaMKII phosphorylates a serine residue (S1303) in the GluN2B CT. CaMKII also phosphorylates a serine site (S831) in the CT of α-amino-3-hydroxy-5- methylisoxazole-4-propionic acid receptors. This phosphorylation enhances channel conductance and is critical for synaptic plasticity. In addition to iGluRs, CaMKII binds to the proximal CT region of mGluR1a, which enables the kinase to phosphorylate threonine 871. Agonist stimulation of mGluR1a triggers a CaMKII-mediated negative feedback to facilitate endocytosis and desensitization of the receptor. CaMKII also binds to the mGluR5 CT. This binding seems to anchor and accumulate inactive CaMKII at synaptic sites. Active CaMKII dissociates from mGluR5 and may then bind to adjacent GluN2B to mediate the mGluR5-NMDAR coupling. Together, glutamate receptors serve as direct substrates of CaMKII. By phosphorylating these receptors, CaMKII plays a central role in controlling the number and activity of the modified receptors and determining the strength of excitatory synaptic transmission.
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Affiliation(s)
- Li-Min Mao
- Department of Basic Medical Science, School of Medicine, University of Missouri-Kansas City, Kansas City, MO 64108, USA.
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192
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Castilho AF, Liberal JT, Baptista FI, Gaspar JM, Carvalho AL, Ambrósio AF. Diabetes causes transient changes in the composition and phosphorylation of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors and interaction with auxiliary proteins in the rat retina. Mol Vis 2014; 20:894-907. [PMID: 24966661 PMCID: PMC4067234] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2014] [Accepted: 06/19/2014] [Indexed: 11/03/2022] Open
Abstract
PURPOSE The impairment of glutamatergic neurotransmission has been associated with diabetic complications in the central nervous system, such as diabetic retinopathy. Here, we investigated the effect of elevated glucose exposure and diabetes on α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor composition, subunit phosphorylation, and the association of the GluA2 subunit with accessory proteins in the retina. METHODS The subunit composition of AMPA receptors and the association of the GluA2 subunit with modulatory proteins were evaluated with coimmunoprecipitation in retinal neural cell cultures and in the retina of experimentally induced-diabetic rats. The phosphorylation status of AMPA receptor subunits was evaluated with western blotting. RESULTS In retinal neural cell cultures, elevated glucose did not significantly alter the composition of AMPA receptors, namely, the interactions between the GluA1, GluA2, and GluA4 subunits, but reduced GluA2 association with GRIP1. Moreover, elevated glucose did not cause changes on the level of GluA1 phosphorylated at serine residues 831 and 845. Diabetes induced early transitory changes in the interaction between AMPA receptor subunits GluA1, GluA2, and GluA4. At 8 weeks of diabetes, the content of GluA1 phosphorylated at serine 831 or serine 845 in the retina increased, compared to age-matched controls. CONCLUSIONS Taken together, these results suggest that diabetes induces dynamic changes in AMPA receptor subunit composition, which could affect glutamatergic transmission in the rat retina.
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Affiliation(s)
- Aurea F. Castilho
- Centre of Ophthalmology and Vision Sciences, Institute for Biomedical Imaging and Life Sciences (IBILI), University of Coimbra, Coimbra, Portugal
| | - Joana T. Liberal
- Centre of Ophthalmology and Vision Sciences, Institute for Biomedical Imaging and Life Sciences (IBILI), University of Coimbra, Coimbra, Portugal
| | - Filipa I. Baptista
- Centre of Ophthalmology and Vision Sciences, Institute for Biomedical Imaging and Life Sciences (IBILI), University of Coimbra, Coimbra, Portugal
| | - Joana M. Gaspar
- Centre of Ophthalmology and Vision Sciences, Institute for Biomedical Imaging and Life Sciences (IBILI), University of Coimbra, Coimbra, Portugal,Center for Neuroscience and Cell Biology, University of Coimbra, Coimbra, Portugal
| | - Ana Luísa Carvalho
- Center for Neuroscience and Cell Biology, University of Coimbra, Coimbra, Portugal,Department of Life Sciences, University of Coimbra, Coimbra, Portugal
| | - António F. Ambrósio
- Centre of Ophthalmology and Vision Sciences, Institute for Biomedical Imaging and Life Sciences (IBILI), University of Coimbra, Coimbra, Portugal,Center for Neuroscience and Cell Biology, University of Coimbra, Coimbra, Portugal,AIBILI, Coimbra, Portugal
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193
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He Y, Kulasiri D, Samarasinghe S. Systems biology of synaptic plasticity: a review on N-methyl-D-aspartate receptor mediated biochemical pathways and related mathematical models. Biosystems 2014; 122:7-18. [PMID: 24929130 DOI: 10.1016/j.biosystems.2014.06.005] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2014] [Revised: 06/05/2014] [Accepted: 06/06/2014] [Indexed: 10/25/2022]
Abstract
Synaptic plasticity, an emergent property of synaptic networks, has shown strong correlation to one of the essential functions of the brain, memory formation. Through understanding synaptic plasticity, we hope to discover the modulators and mechanisms that trigger memory formation. In this paper, we first review the well understood modulators and mechanisms underlying N-methyl-D-aspartate receptor dependent synaptic plasticity, a major form of synaptic plasticity in hippocampus, and then comment on the key mathematical modelling approaches available in the literature to understand synaptic plasticity as the integration of the established functionalities of synaptic components.
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Affiliation(s)
- Y He
- Centre for Advanced Computational Solutions (C-fACS), Molecular Biosciences Department, Lincoln University, Christchurch, New Zealand
| | - D Kulasiri
- Centre for Advanced Computational Solutions (C-fACS), Molecular Biosciences Department, Lincoln University, Christchurch, New Zealand.
| | - S Samarasinghe
- Centre for Advanced Computational Solutions (C-fACS), Molecular Biosciences Department, Lincoln University, Christchurch, New Zealand
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194
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Fan X, Jin WY, Wang YT. The NMDA receptor complex: a multifunctional machine at the glutamatergic synapse. Front Cell Neurosci 2014; 8:160. [PMID: 24959120 PMCID: PMC4051310 DOI: 10.3389/fncel.2014.00160] [Citation(s) in RCA: 72] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2014] [Accepted: 05/26/2014] [Indexed: 01/11/2023] Open
Abstract
The N-methyl-D-aspartate receptors (NMDARs) are part of a large multiprotein complex at the glutamatergic synapse. The assembly of NMDARs with synaptic proteins offers a means to regulate NMDAR channel properties and receptor trafficking, and couples NMDAR activation to distinct intracellular signaling pathways, thus contributing to the versatility of NMDAR functions. Receptor-protein interactions at the synapse provide a dynamic and powerful mechanism for regulating synaptic efficacy, but can also contribute to NMDAR overactivation-induced excitotoxicity and cellular damage under pathological conditions. An emerging concept is that by understanding the mechanisms and functions of disease-specific protein-protein interactions in the NMDAR complex, we may be able to develop novel therapies based on protein-NMDAR interactions for the treatment of brain diseases in which NMDAR dysfunction is at the root of their pathogenesis.
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Affiliation(s)
- Xuelai Fan
- Brain Research Centre and Department of Medicine, Vancouver Coastal Health Research Institute, University of British Columbia Vancouver, BC, Canada
| | - Wu Yang Jin
- Brain Research Centre and Department of Medicine, Vancouver Coastal Health Research Institute, University of British Columbia Vancouver, BC, Canada
| | - Yu Tian Wang
- Brain Research Centre and Department of Medicine, Vancouver Coastal Health Research Institute, University of British Columbia Vancouver, BC, Canada
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195
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Mao LM, Hastings JM, Fibuch EE, Wang JQ. Propofol selectively alters GluA1 AMPA receptor phosphorylation in the hippocampus but not prefrontal cortex in young and aged mice. Eur J Pharmacol 2014; 738:237-44. [PMID: 24907515 DOI: 10.1016/j.ejphar.2014.05.053] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2014] [Revised: 05/27/2014] [Accepted: 05/28/2014] [Indexed: 10/25/2022]
Abstract
Propofol is a commonly used general anesthetic agent which has been previously shown to enhance the inhibitory GABAergic transmission in the central nervous system. In addition to the GABAergic element, the excitatory transmission may be another central molecular site impacted by propofol. Increasing evidence implies that the alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) receptor represents an excitatory amino acid receptor subtype subjected to the regulation by propofol. Indeed, in this study, we found that a single injection of propofol at an anesthetic dose increased AMPA receptor GluA1 subunit phosphorylation in young (2-3 months old) and aged (20-21 months old) mice in vivo. Propofol caused an increase in GluA1 phosphorylation in the hippocampus but not in the prefrontal cortex. The propofol effect was also site-selective as the drug elevated GluA1 phosphorylation at serine 831 (S831) but not serine 845. Interestingly, while propofol induced a moderate and transient increase in S831 phosphorylation in young mice, the drug caused a substantial and sustained S831 phosphorylation in aged animals. Total GluA1 abundance remained stable in the hippocampus and prefrontal cortex in both young and aged mice in response to propofol. These results provide evidence supporting the sensitivity of GluA1 AMPA receptors to propofol. A single dose of propofol was able to upregulate GluA1 phosphorylation in the confined hippocampus in an age-dependent manner.
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Affiliation(s)
- Li-Min Mao
- Department of Basic Medical Science, School of Medicine, University of Missouri-Kansas City, MO 64108, USA
| | - James M Hastings
- Department of Anesthesiology, School of Medicine, University of Missouri-Kansas City, Kansas City, MO 64108, USA
| | - Eugene E Fibuch
- Department of Anesthesiology, School of Medicine, University of Missouri-Kansas City, Kansas City, MO 64108, USA
| | - John Q Wang
- Department of Basic Medical Science, School of Medicine, University of Missouri-Kansas City, MO 64108, USA; Department of Anesthesiology, School of Medicine, University of Missouri-Kansas City, Kansas City, MO 64108, USA.
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196
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Wu A, Wang C, Niu L. Mechanism of inhibition of the GluA1 AMPA receptor channel opening by the 2,3-benzodiazepine compound GYKI 52466 and a N-methyl-carbamoyl derivative. Biochemistry 2014; 53:3033-41. [PMID: 24738995 PMCID: PMC4025570 DOI: 10.1021/bi5002079] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
![]()
2,3-Benzodiazepine derivatives, also
known as GYKI compounds, represent
a group of the most promising synthetic inhibitors of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic
acid (AMPA) receptors. Here we investigate the mechanism of inhibition
of the GluA1 channel opening and the site of inhibition by GYKI 52466
and its N-3 methyl-carbamoyl derivative, which we term as BDZ-f. GluA1 is a key AMPA receptor subunit involved in the
brain function. Excessive activity and elevated expression of GluA1,
however, has been implicated in a number of neurological disorders.
Using a laser-pulse photolysis technique, which provides ∼60
μs resolution, we measured the effect of these inhibitors on
the rate of GluA1 channel opening and the amplitude of the glutamate-induced
whole-cell current. We found that both compounds inhibit GluA1 channel
noncompetitively. Addition of an N-3 methyl-carbamoyl group to the
diazepine ring with the azomethine feature (i.e., GYKI 52466) improves
the potency of the resulting compound or BDZ-f without
changing the site of binding. This site, which we previously termed
as the “M” site on the GluA2 AMPA receptor subunit,
therefore favorably accommodates an N-3 acylating group. On the basis
of the magnitude of the inhibition constants for the same inhibitors
but different receptors, the “M” sites on GluA1 and
GuA2 are different. Overall, the “M” site or the binding
environment on GluA2 accommodates the same compounds better, or the
same inhibitors show stronger potency on GluA2, as we have reported
previously [Wang et al. (2011) 50, 7284−729321751782]. However, acylating
the N-3 position to occupy the N-3 side pocket of the “M”
site can significantly narrow the difference and improve the potency
of a resulting compound on GluA1.
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Affiliation(s)
- Andrew Wu
- Department of Chemistry, and Center for Neuroscience Research, University at Albany, SUNY , Albany, New York 12222, United States
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197
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Gray EE, Guglietta R, Khakh BS, O'Dell TJ. Inhibitory interactions between phosphorylation sites in the C terminus of α-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid-type glutamate receptor GluA1 subunits. J Biol Chem 2014; 289:14600-11. [PMID: 24706758 DOI: 10.1074/jbc.m114.553537] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
The C terminus of AMPA-type glutamate receptor (AMPAR) GluA1 subunits contains several phosphorylation sites that regulate AMPAR activity and trafficking at excitatory synapses. Although many of these sites have been extensively studied, little is known about the signaling mechanisms regulating GluA1 phosphorylation at Thr-840. Here, we report that neuronal depolarization in hippocampal slices induces a calcium and protein phosphatase 1/2A-dependent dephosphorylation of GluA1 at Thr-840 and a nearby site at Ser-845. Despite these similarities, inhibitors of NMDA-type glutamate receptors and protein phosphatase 2B prevented depolarization-induced Ser-845 dephosphorylation but had no effect on Thr-840 dephosphorylation. Instead, depolarization-induced Thr-840 dephosphorylation was prevented by blocking voltage-gated calcium channels, indicating that distinct Ca(2+) sources converge to regulate GluA1 dephosphorylation at Thr-840 and Ser-845 in separable ways. Results from immunoprecipitation/depletion assays indicate that Thr-840 phosphorylation inhibits protein kinase A (PKA)-mediated increases in Ser-845 phosphorylation. Consistent with this, PKA-mediated increases in AMPAR currents, which are dependent on Ser-845 phosphorylation, were inhibited in HEK-293 cells expressing a Thr-840 phosphomimetic version of GluA1. Conversely, mimicking Ser-845 phosphorylation inhibited protein kinase C phosphorylation of Thr-840 in vitro, and PKA activation inhibited Thr-840 phosphorylation in hippocampal slices. Together, the regulation of Thr-840 and Ser-845 phosphorylation by distinct sources of Ca(2+) influx and the presence of inhibitory interactions between these sites highlight a novel mechanism for conditional regulation of AMPAR phosphorylation and function.
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Affiliation(s)
- Erin E Gray
- From the Department of Physiology and Interdepartmental Ph.D. Program for Neuroscience at UCLA, and
| | - Ryan Guglietta
- From the Department of Physiology and Interdepartmental Ph.D. Program for Neuroscience at UCLA, and
| | - Baljit S Khakh
- From the Department of Physiology and Department of Neurobiology, David Geffen School of Medicine at UCLA
| | - Thomas J O'Dell
- From the Department of Physiology and UCLA Integrative Center for Learning and Memory, Los Angeles, California 90095
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198
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CaMKII activity in the ventral tegmental area gates cocaine-induced synaptic plasticity in the nucleus accumbens. Neuropsychopharmacology 2014; 39:989-99. [PMID: 24154664 PMCID: PMC3924533 DOI: 10.1038/npp.2013.299] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/22/2013] [Revised: 10/17/2013] [Accepted: 10/18/2013] [Indexed: 12/18/2022]
Abstract
Addictive drugs such as cocaine induce synaptic plasticity in discrete regions of the reward circuit. The aim of the present study is to investigate whether cocaine-evoked synaptic plasticity in the ventral tegmental area (VTA) and nucleus accumbens (NAc) is causally linked. Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) is a central regulator of long-term synaptic plasticity, learning, and drug addiction. We examined whether blocking CaMKII activity in the VTA affected cocaine conditioned place preference (CPP) and cocaine-evoked synaptic plasticity in its target brain region, the NAc. TatCN21 is a CaMKII inhibitory peptide that blocks both stimulated and autonomous CaMKII activity with high selectivity. We report that intra-VTA microinjections of tatCN21 before cocaine conditioning blocked the acquisition of cocaine CPP, whereas intra-VTA microinjections of tatCN21 before saline conditioning did not significantly affect cocaine CPP, suggesting that the CaMKII inhibitor blocks cocaine CPP through selective disruption of cocaine-cue-associated learning. Intra-VTA tatCN21 before cocaine conditioning blocked cocaine-evoked depression of excitatory synaptic transmission in the shell of the NAc slices ex vivo. In contrast, intra-VTA microinjection of tatCN21 just before the CPP test did not affect the expression of cocaine CPP and cocaine-induced synaptic plasticity in the NAc shell. These results suggest that CaMKII activity in the VTA governs cocaine-evoked synaptic plasticity in the NAc during the time window of cocaine conditioning.
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199
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Inhibition of AMPA receptors by polyamine toxins is regulated by agonist efficacy and stargazin. Neurochem Res 2014; 39:1906-13. [PMID: 24557991 DOI: 10.1007/s11064-014-1258-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2013] [Revised: 02/10/2014] [Accepted: 02/12/2014] [Indexed: 12/18/2022]
Abstract
The α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid receptors (AMPARs) are glutamate-gated cation channels mediating the majority of fast excitatory synaptic transmission in the central nervous system (CNS). Polyamine toxins derived from spiders and wasps are use- and voltage-dependent channel blockers of Ca(2+)-permeable AMPARs. Recent studies have suggested that AMPAR block by polyamine toxins is modulated by auxiliary subunits from the class of transmembrane AMPAR regulatory proteins (TARPs), which may have implications for their use as tool compounds in native systems. We have explored the effect of the TARP γ-2 (also known as stargazin) on the inhibitory potency of three structurally different polyamine toxins at Ca(2+)-permeable homomeric GluA1 AMPARs expressed in oocytes. We find that polyamine toxin IC50 is differentially affected by presence of stargazin depending on the efficacy of the agonists used to activate GluA1. Co-assembly of GluA1 receptors with stargazin increases the potency of the polyamine toxins when activated by the weak partial agonist kainate, but has no effect in presence of full-agonist L-glutamate (Glu) and partial agonist (RS)-willardiine.
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Pamenter ME, Carr JA, Go A, Fu Z, Reid SG, Powell FL. Glutamate receptors in the nucleus tractus solitarius contribute to ventilatory acclimatization to hypoxia in rat. J Physiol 2014; 592:1839-56. [PMID: 24492841 DOI: 10.1113/jphysiol.2013.268706] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
When exposed to a hypoxic environment the body's first response is a reflex increase in ventilation, termed the hypoxic ventilatory response (HVR). With chronic sustained hypoxia (CSH), such as during acclimatization to high altitude, an additional time-dependent increase in ventilation occurs, which increases the HVR. This secondary increase persists after exposure to CSH and involves plasticity within the circuits in the central nervous system that control breathing. Currently these mechanisms of HVR plasticity are unknown and we hypothesized that they involve glutamatergic synapses in the nucleus tractus solitarius (NTS), where afferent endings from arterial chemoreceptors terminate. To test this, we treated rats held in normoxia (CON) or 10% O2 (CSH) for 7 days and measured ventilation in conscious, unrestrained animals before and after microinjecting glutamate receptor agonists and antagonists into the NTS. In normoxia, AMPA increased ventilation 25% and 50% in CON and CSH, respectively, while NMDA doubled ventilation in both groups (P < 0.05). Specific AMPA and NMDA receptor antagonists (NBQX and MK801, respectively) abolished these effects. MK801 significantly decreased the HVR in CON rats, and completely blocked the acute HVR in CSH rats but had no effect on ventilation in normoxia. NBQX decreased ventilation whenever it was increased relative to normoxic controls; i.e. acute hypoxia in CON and CSH, and normoxia in CSH. These results support our hypothesis that glutamate receptors in the NTS contribute to plasticity in the HVR with CSH. The mechanism underlying this synaptic plasticity is probably glutamate receptor modification, as in CSH rats the expression of phosphorylated NR1 and GluR1 proteins in the NTS increased 35% and 70%, respectively, relative to that in CON rats.
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Affiliation(s)
- Matthew E Pamenter
- Division of Physiology, Department of Medicine, University of California San Diego, 9500 Gilman Dr., La Jolla, CA 92093-0623, USA.
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