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Trovò L, Kouvaros S, Schwenk J, Fernandez-Fernandez D, Fritzius T, Rem PD, Früh S, Gassmann M, Fakler B, Bischofberger J, Bettler B. Synaptotagmin-11 facilitates assembly of a presynaptic signaling complex in post-Golgi cargo vesicles. EMBO Rep 2024; 25:2610-2634. [PMID: 38698221 PMCID: PMC11169412 DOI: 10.1038/s44319-024-00147-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2023] [Revised: 04/11/2024] [Accepted: 04/12/2024] [Indexed: 05/05/2024] Open
Abstract
GABAB receptors (GBRs), the G protein-coupled receptors for GABA, regulate synaptic transmission throughout the brain. A main synaptic function of GBRs is the gating of Cav2.2-type Ca2+ channels. However, the cellular compartment where stable GBR/Cav2.2 signaling complexes form remains unknown. In this study, we demonstrate that the vesicular protein synaptotagmin-11 (Syt11) binds to both the auxiliary GBR subunit KCTD16 and Cav2.2 channels. Through these dual interactions, Syt11 recruits GBRs and Cav2.2 channels to post-Golgi vesicles, thus facilitating assembly of GBR/Cav2.2 signaling complexes. In addition, Syt11 stabilizes GBRs and Cav2.2 channels at the neuronal plasma membrane by inhibiting constitutive internalization. Neurons of Syt11 knockout mice exhibit deficits in presynaptic GBRs and Cav2.2 channels, reduced neurotransmitter release, and decreased GBR-mediated presynaptic inhibition, highlighting the critical role of Syt11 in the assembly and stable expression of GBR/Cav2.2 complexes. These findings support that Syt11 acts as a vesicular scaffold protein, aiding in the assembly of signaling complexes from low-abundance components within transport vesicles. This mechanism enables insertion of pre-assembled functional signaling units into the synaptic membrane.
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Affiliation(s)
- Luca Trovò
- Department of Biomedicine, University of Basel, Basel, Switzerland
| | | | - Jochen Schwenk
- Institute of Physiology, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | | | | | | | - Simon Früh
- Department of Biomedicine, University of Basel, Basel, Switzerland
| | - Martin Gassmann
- Department of Biomedicine, University of Basel, Basel, Switzerland
| | - Bernd Fakler
- Institute of Physiology, Faculty of Medicine, University of Freiburg, Freiburg, Germany
- CIBSS Center for Integrative Biological Signalling Studies, University of Freiburg, Freiburg, Germany
- Center for Basics in NeuroModulation, Freiburg, Germany
| | | | - Bernhard Bettler
- Department of Biomedicine, University of Basel, Basel, Switzerland.
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2
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Hleihil M, Benke D. Restoring GABA B receptor expression in the ventral tegmental area of methamphetamine addicted mice inhibits locomotor sensitization and drug seeking behavior. Front Mol Neurosci 2024; 17:1347228. [PMID: 38384279 PMCID: PMC10879384 DOI: 10.3389/fnmol.2024.1347228] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2023] [Accepted: 01/15/2024] [Indexed: 02/23/2024] Open
Abstract
Repeated exposure to psychostimulants such as methamphetamine (METH) induces neuronal adaptations in the mesocorticolimbic dopamine system, including the ventral tegmental area (VTA). These changes lead to persistently enhanced neuronal activity causing increased dopamine release and addictive phenotypes. A factor contributing to increased dopaminergic activity in this system appears to be reduced GABAB receptor-mediated neuronal inhibition in the VTA. Dephosphorylation of serine 783 (Ser783) of the GABAB2 subunit by protein phosphatase 2A (PP2A) appears to trigger the downregulation GABAB receptors in psychostimulant-addicted rodents. Therefore, preventing the interaction of GABAB receptors with PP2A using an interfering peptide is a promising strategy to restore GABAB receptor-mediated neuronal inhibition. We have previously developed an interfering peptide (PP2A-Pep) that inhibits the GABAB receptors/PP2A interaction and thereby restores receptor expression under pathological conditions. Here, we tested the hypothesis that restoration of GABAB receptor expression in the VTA of METH addicted mice reduce addictive phenotypes. We found that the expression of GABAB receptors was significantly reduced in the VTA and nucleus accumbens but not in the hippocampus and somatosensory cortex of METH-addicted mice. Infusion of PP2A-Pep into the VTA of METH-addicted mice restored GABAB receptor expression in the VTA and inhibited METH-induced locomotor sensitization as assessed in the open field test. Moreover, administration of PP2A-Pep into the VTA also reduced drug seeking behavior in the conditioned place preference test. These observations underscore the importance of VTA GABAB receptors in controlling addictive phenotypes. Furthermore, this study illustrates the value of interfering peptides targeting diseases-related protein-protein interactions as an alternative approach for a potential development of selective therapeutic interventions.
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Affiliation(s)
- Mohammad Hleihil
- Institute of Pharmacology and Toxicology, University of Zurich, Zürich, Switzerland
| | - Dietmar Benke
- Institute of Pharmacology and Toxicology, University of Zurich, Zürich, Switzerland
- Neuroscience Center Zurich, University and ETH Zurich, Zürich, Switzerland
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3
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Bhat MA, Hleihil M, Benke D. Restoration of GABA B receptor expression in cerebral ischemia: a promising novel neuroprotective strategy. Neural Regen Res 2023; 18:2659-2660. [PMID: 37449610 DOI: 10.4103/1673-5374.373704] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/18/2023] Open
Affiliation(s)
- Musadiq A Bhat
- Institute of Pharmacology and Toxicology, University of Zurich, Zurich, Switzerland
| | - Mohammad Hleihil
- Institute of Pharmacology and Toxicology, University of Zurich, Zurich, Switzerland
| | - Dietmar Benke
- Institute of Pharmacology and Toxicology, University of Zurich, Zurich, Switzerland
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4
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Bhat MA, Grampp T, Benke D. ERK1/2-Dependent Phosphorylation of GABA B1(S867/T872), Controlled by CaMKIIβ, Is Required for GABA B Receptor Degradation under Physiological and Pathological Conditions. Int J Mol Sci 2023; 24:13436. [PMID: 37686242 PMCID: PMC10488028 DOI: 10.3390/ijms241713436] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2023] [Revised: 08/28/2023] [Accepted: 08/29/2023] [Indexed: 09/10/2023] Open
Abstract
GABAB receptor-mediated inhibition is indispensable for maintaining a healthy neuronal excitation/inhibition balance. Many neurological diseases are associated with a disturbed excitation/inhibition balance and downregulation of GABAB receptors due to enhanced sorting of the receptors to lysosomal degradation. A key event triggering the downregulation of the receptors is the phosphorylation of S867 in the GABAB1 subunit mediated by CaMKIIβ. Interestingly, close to S867 in GABAB1 exists another phosphorylation site, T872. Therefore, the question arose as to whether phosphorylation of T872 is involved in downregulating the receptors and whether phosphorylation of this site is also mediated by CaMKIIβ or by another protein kinase. Here, we show that mutational inactivation of T872 in GABAB1 prevented the degradation of the receptors in cultured neurons. We found that, in addition to CaMKIIβ, also ERK1/2 is involved in the degradation pathway of GABAB receptors under physiological and ischemic conditions. In contrast to our previous view, CaMKIIβ does not appear to directly phosphorylate S867. Instead, the data support a mechanism in which CaMKIIβ activates ERK1/2, which then phosphorylates S867 and T872 in GABAB1. Blocking ERK activity after subjecting neurons to ischemic stress completely restored downregulated GABAB receptor expression to normal levels. Thus, preventing ERK1/2-mediated phosphorylation of S867/T872 in GABAB1 is an opportunity to inhibit the pathological downregulation of the receptors after ischemic stress and is expected to restore a healthy neuronal excitation/inhibition balance.
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Affiliation(s)
- Musadiq A. Bhat
- Institute of Pharmacology and Toxicology, University of Zurich, 8057 Zurich, Switzerland; (M.A.B.); (T.G.)
| | - Thomas Grampp
- Institute of Pharmacology and Toxicology, University of Zurich, 8057 Zurich, Switzerland; (M.A.B.); (T.G.)
| | - Dietmar Benke
- Institute of Pharmacology and Toxicology, University of Zurich, 8057 Zurich, Switzerland; (M.A.B.); (T.G.)
- Neuroscience Center Zurich, University of Zurich and ETH Zurich, 8057 Zurich, Switzerland
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5
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Dergunova LV, Filippenkov IB, Limborska SA, Myasoedov NF. Neuroprotective Peptides and New Strategies for Ischemic Stroke Drug Discoveries. Genes (Basel) 2023; 14:genes14050953. [PMID: 37239313 DOI: 10.3390/genes14050953] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2023] [Revised: 04/15/2023] [Accepted: 04/20/2023] [Indexed: 05/28/2023] Open
Abstract
Ischemic stroke continues to be one of the leading causes of death and disability in the adult population worldwide. The currently used pharmacological methods for the treatment of ischemic stroke are not effective enough and require the search for new tools and approaches to identify therapeutic targets and potential neuroprotectors. Today, in the development of neuroprotective drugs for the treatment of stroke, special attention is paid to peptides. Namely, peptide action is aimed at blocking the cascade of pathological processes caused by a decrease in blood flow to the brain tissues. Different groups of peptides have therapeutic potential in ischemia. Among them are small interfering peptides that block protein-protein interactions, cationic arginine-rich peptides with a combination of various neuroprotective properties, shuttle peptides that ensure the permeability of neuroprotectors through the blood-brain barrier, and synthetic peptides that mimic natural regulatory peptides and hormones. In this review, we consider the latest achievements and trends in the development of new biologically active peptides, as well as the role of transcriptomic analysis in identifying the molecular mechanisms of action of potential drugs aimed at the treatment of ischemic stroke.
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Affiliation(s)
- Lyudmila V Dergunova
- Institute of Molecular Genetics, National Research Center "Kurchatov Institute", Kurchatov Sq. 2, 123182 Moscow, Russia
| | - Ivan B Filippenkov
- Institute of Molecular Genetics, National Research Center "Kurchatov Institute", Kurchatov Sq. 2, 123182 Moscow, Russia
| | - Svetlana A Limborska
- Institute of Molecular Genetics, National Research Center "Kurchatov Institute", Kurchatov Sq. 2, 123182 Moscow, Russia
| | - Nikolay F Myasoedov
- Institute of Molecular Genetics, National Research Center "Kurchatov Institute", Kurchatov Sq. 2, 123182 Moscow, Russia
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6
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Lu MF, Fu Q, Qiu TY, Yang JH, Peng QH, Hu ZZ. The CaMKII-dependent phosphorylation of GABA B receptors in the nucleus accumbens was involved in cocaine-induced behavioral sensitization in rats. CNS Neurosci Ther 2023; 29:1345-1356. [PMID: 36756679 PMCID: PMC10068462 DOI: 10.1111/cns.14107] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2022] [Revised: 01/16/2023] [Accepted: 01/18/2023] [Indexed: 02/10/2023] Open
Abstract
BACKGROUND Previous studies have established that the regulation of prolonged, distal neuronal inhibition by the GABAB heteroreceptor (GABAB R) is determined by its stability, and hence residence time, on the plasma membrane. AIMS Here, we show that GABAB R in the nucleus accumbens (NAc) of rats affects the development of cocaine-induced behavioral sensitization by mediating its perinucleus internalization and membrane expression. MATERIALS & METHODS By immunofluorescent labeling, flow cytometry analysis, Co-immunoprecipitation and open field test, we measured the role of Ca2+ /calmodulin-dependent protein kinase II (CaMKII) to the control of GABAB R membrane anchoring and cocaine induced-behavioral sensitization. RESULTS Repeated cocaine treatment in rats (15 mg/kg) significantly decreases membrane levels of GABAB1 R and GABAB2 R in the NAc after day 3, 5 and 7. The membrane fluorescence and protein levels of GABAB R was also decreased in NAc GAD67 + neurons post cocaine (1 μM) treatment after 5 min. Moreover, the majority of internalized GABAB1 Rs exhibited perinuclear localization, a decrease in GABAB1 R-pHluroin signals was observed in cocaine-treated NAc neurons. By contrast, membrane expression of phosphorylated CaMKII (pCaMKII) post cocaine treatment was significantly increased after day 1, 3, 5 and 7. Baclofen blocked the cocaine induced behavioral sensitization via inhibition of cocaine enhanced-pCaMKII-GABAB1 R interaction. CONCLUSION These findings reveal a new mechanism by which pCaMKII-GABAB R signaling can promote psychostimulant-induced behavioral sensitization.
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Affiliation(s)
- Ming F Lu
- Department of Pathophysiology, College of Basic Medicine, Nanchang University, Nanchang, Jiangxi, China.,Jiangxi Province Key Laboratory of Tumor Pathogens and Molecular Pathology, Department of Pathology, Schools of Basic Medical Sciences and Pharmaceutical Sciences, Nanchang University, Nanchang, Jiangxi, China
| | - Qiang Fu
- Department of Respiration, Department Two, Jiangxi Provincial People's Hospital, Nanchang, Jiangxi, China
| | - Tian Y Qiu
- Department of Pathophysiology, College of Basic Medicine, Nanchang University, Nanchang, Jiangxi, China.,Jiangxi Province Key Laboratory of Tumor Pathogens and Molecular Pathology, Department of Pathology, Schools of Basic Medical Sciences and Pharmaceutical Sciences, Nanchang University, Nanchang, Jiangxi, China
| | - Jian H Yang
- Department of Physiology, College of Basic Medicine, Nanchang University, Nanchang, Jiangxi, China
| | - Qing H Peng
- Department of Anesthesiology, The First Affiliated Hospital, Nanchang University, Nanchang, Jiangxi, China
| | - Zhen Z Hu
- Department of Pathophysiology, College of Basic Medicine, Nanchang University, Nanchang, Jiangxi, China.,Jiangxi Province Key Laboratory of Tumor Pathogens and Molecular Pathology, Department of Pathology, Schools of Basic Medical Sciences and Pharmaceutical Sciences, Nanchang University, Nanchang, Jiangxi, China
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7
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Hleihil M, Balakrishnan K, Benke D. Protein phosphatase 2A regulation of GABAB receptors normalizes ischemia-induced aberrant receptor trafficking and provides neuroprotection. Front Mol Neurosci 2022; 15:1015906. [PMID: 36311027 PMCID: PMC9607930 DOI: 10.3389/fnmol.2022.1015906] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2022] [Accepted: 09/26/2022] [Indexed: 11/13/2022] Open
Abstract
One major factor regulating the strength of GABAB receptor signaling and thereby neuronal excitability is the dynamic control of their cell surface expression. GABAB receptors are constitutively internalized and recycled back to the plasma membrane to maintain a stable number of receptors at cell surface for appropriate signaling. Protein phosphatase 2A (PP2A) dependent dephosphorylation of serine 783 (S783) in the GABAB2 subunit is a key event for downregulating GABAB receptor cell surface expression particularly under conditions associated with excitotoxicity. Here, we investigated the role of PP2A in regulating GABAB receptor cell surface expression under physiological and excitotoxic conditions. For this purpose, we developed an interfering peptide (PP2A-Pep) that inhibits the interaction of GABAB receptors with PP2A. Using cultured cortical neurons, we found that PP2A downregulates GABAB receptor cell surface expression by inhibiting recycling of the receptors and thereby promoting degradation of the receptors. Inhibition of the GABAB receptor/PP2A interaction by PP2A-Pep in cultured cortical neurons restored GABAB receptor cell surface expression after excitotoxic stress and inhibited progressing neuronal death even when added 48 h after the insult. To explore the therapeutic potential of PP2A-Pep, we further analyzed effect of PP2A-Pep in the middle cerebral artery occlusion (MCAO) mouse model of cerebral ischemia. Incubation of brain slices prepared from MCAO-treated mice with PP2A-Pep restored normal GABAB receptor expression and GABAB receptor-mediated inhibition, reduced ischemic-induced overexcitability of neurons, and prevented neuronal death in the ischemic penumbra. This data illustrates the crucial role of regulating GABAB receptor phosphorylation by PP2A for controlling neuronal inhibition and excitability. The results further suggest that interfering with the GABAB receptor/PP2A interaction is a promising strategy for the development of specific therapeutic interventions to treat neurological diseases associated with a disturbed excitation/inhibition balance and downregulation of GABAB receptors.
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Affiliation(s)
- Mohammad Hleihil
- Institute of Pharmacology and Toxicology, University of Zurich, Zurich, Switzerland
- Neuroscience Center Zurich, University of Zurich and ETH Zürich, Zurich, Switzerland
| | - Karthik Balakrishnan
- Institute of Pharmacology and Toxicology, University of Zurich, Zurich, Switzerland
| | - Dietmar Benke
- Institute of Pharmacology and Toxicology, University of Zurich, Zurich, Switzerland
- Neuroscience Center Zurich, University of Zurich and ETH Zürich, Zurich, Switzerland
- Drug Discovery Network Zurich, Zurich, Switzerland
- *Correspondence: Dietmar Benke,
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8
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Balakrishnan K, Hleihil M, Bhat MA, Ganley RP, Vaas M, Klohs J, Zeilhofer HU, Benke D. Targeting the interaction of GABA B receptors with CaMKII with an interfering peptide restores receptor expression after cerebral ischemia and inhibits progressive neuronal death in mouse brain cells and slices. Brain Pathol 2022; 33:e13099. [PMID: 35698024 PMCID: PMC9836377 DOI: 10.1111/bpa.13099] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2022] [Accepted: 05/29/2022] [Indexed: 01/21/2023] Open
Abstract
Cerebral ischemia is the leading cause for long-term disability and mortality in adults due to massive neuronal death. Currently, there is no pharmacological treatment available to limit progressive neuronal death after stroke. A major mechanism causing ischemia-induced neuronal death is the excessive release of glutamate and the associated overexcitation of neurons (excitotoxicity). Normally, GABAB receptors control neuronal excitability in the brain via prolonged inhibition. However, excitotoxic conditions rapidly downregulate GABAB receptors via a CaMKII-mediated mechanism and thereby diminish adequate inhibition that could counteract neuronal overexcitation and neuronal death. To prevent the deleterious downregulation of GABAB receptors, we developed a cell-penetrating synthetic peptide (R1-Pep) that inhibits the interaction of GABAB receptors with CaMKII. Administration of this peptide to cultured cortical neurons exposed to excitotoxic conditions restored cell surface expression and function of GABAB receptors. R1-Pep did not affect CaMKII expression or activity but prevented its T286 autophosphorylation that renders it autonomously and persistently active. Moreover, R1-Pep counteracted the aberrant downregulation of G protein-coupled inwardly rectifying K+ channels and the upregulation of N-type voltage-gated Ca2+ channels, the main effectors of GABAB receptors. The restoration of GABAB receptors activated the Akt survival pathway and inhibited excitotoxic neuronal death with a wide time window in cultured neurons. Restoration of GABAB receptors and neuroprotective activity of R1-Pep was verified by using brain slices prepared from mice after middle cerebral artery occlusion (MCAO). Treatment with R1-Pep restored normal GABAB receptor expression and GABA receptor-mediated K+ channel currents. This reduced MCAO-induced neuronal excitability and inhibited neuronal death. These results support the hypothesis that restoration of GABAB receptor expression under excitatory conditions provides neuroprotection and might be the basis for the development of a selective intervention to inhibit progressive neuronal death after ischemic stroke.
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Affiliation(s)
- Karthik Balakrishnan
- Institute of Pharmacology and Toxicology, University of ZurichZurichSwitzerland,Neuroscience Center ZurichUniversity of Zurich and ETH ZurichZurichSwitzerland,Present address:
Dewpoint Therapeutics GMBHDresdenGermany
| | - Mohammad Hleihil
- Institute of Pharmacology and Toxicology, University of ZurichZurichSwitzerland,Neuroscience Center ZurichUniversity of Zurich and ETH ZurichZurichSwitzerland
| | - Musadiq A. Bhat
- Institute of Pharmacology and Toxicology, University of ZurichZurichSwitzerland
| | - Robert P. Ganley
- Institute of Pharmacology and Toxicology, University of ZurichZurichSwitzerland
| | - Markus Vaas
- Institute of Pharmacology and Toxicology, University of ZurichZurichSwitzerland,Present address:
Clinical Trial Center ZurichUniversity Hospital of ZurichZurichSwitzerland
| | - Jan Klohs
- Neuroscience Center ZurichUniversity of Zurich and ETH ZurichZurichSwitzerland,Institute for Biomedical Engineering, University of Zurich and ETH ZurichZurichSwitzerland
| | - Hanns Ulrich Zeilhofer
- Institute of Pharmacology and Toxicology, University of ZurichZurichSwitzerland,Neuroscience Center ZurichUniversity of Zurich and ETH ZurichZurichSwitzerland,Drug Discovery Network ZurichZurichSwitzerland,Institute of Pharmaceutical Sciences, ETH ZurichZurichSwitzerland
| | - Dietmar Benke
- Institute of Pharmacology and Toxicology, University of ZurichZurichSwitzerland,Neuroscience Center ZurichUniversity of Zurich and ETH ZurichZurichSwitzerland,Drug Discovery Network ZurichZurichSwitzerland
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9
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Abstract
A substantial fraction of the human population suffers from chronic pain states, which often cannot be sufficiently treated with existing drugs. This calls for alternative targets and strategies for the development of novel analgesics. There is substantial evidence that the G protein-coupled GABAB receptor is involved in the processing of pain signals and thus has long been considered a valuable target for the generation of analgesics to treat chronic pain. In this review, the contribution of GABAB receptors to the generation and modulation of pain signals, their involvement in chronic pain states as well as their target suitability for the development of novel analgesics is discussed.
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Affiliation(s)
- Dietmar Benke
- Institute of Pharmacology and Toxicology, University of Zurich, Zurich, Switzerland.
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10
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Abstract
In 1959, E. G. Gray described two different types of synapses in the brain for the first time: symmetric and asymmetric. Later on, symmetric synapses were associated with inhibitory terminals, and asymmetric synapses to excitatory signaling. The balance between these two systems is critical to maintain a correct brain function. Likewise, the modulation of both types of synapses is also important to maintain a healthy equilibrium. Cerebral circuitry responds differently depending on the type of damage and the timeline of the injury. For example, promoting symmetric signaling following ischemic damage is beneficial only during the acute phase; afterwards, it further increases the initial damage. Synapses can be also altered by players not directly related to them; the chronic and long-term neurodegeneration mediated by tau proteins primarily targets asymmetric synapses by decreasing neuronal plasticity and functionality. Dopamine represents the main modulating system within the central nervous system. Indeed, the death of midbrain dopaminergic neurons impairs locomotion, underlying the devastating Parkinson’s disease. Herein, we will review studies on symmetric and asymmetric synapses plasticity after three different stressors: symmetric signaling under acute damage—ischemic stroke; asymmetric signaling under chronic and long-term neurodegeneration—Alzheimer’s disease; symmetric and asymmetric synapses without modulation—Parkinson’s disease.
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11
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Hleihil M, Vaas M, Bhat MA, Balakrishnan K, Benke D. Sustained Baclofen-Induced Activation of GABA B Receptors After Cerebral Ischemia Restores Receptor Expression and Function and Limits Progressing Loss of Neurons. Front Mol Neurosci 2021; 14:726133. [PMID: 34539344 PMCID: PMC8440977 DOI: 10.3389/fnmol.2021.726133] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2021] [Accepted: 08/12/2021] [Indexed: 11/13/2022] Open
Abstract
One important function of GABAB receptors is the control of neuronal activity to prevent overexcitation and thereby excitotoxic death, which is a hallmark of cerebral ischemia. Consequently, sustained activation of GABAB receptors with the selective agonist baclofen provides neuroprotection in in vitro and in vivo models of cerebral ischemia. However, excitotoxic conditions severely downregulate the receptors, which would compromise the neuroprotective effectiveness of baclofen. On the other hand, recent work suggests that sustained activation of GABAB receptors stabilizes receptor expression. Therefore, we addressed the question whether sustained activation of GABAB receptors reduces downregulation of the receptor under excitotoxic conditions and thereby preserves GABAB receptor-mediated inhibition. In cultured neurons subjected to oxygen and glucose deprivation (OGD), to mimic cerebral ischemia, GABAB receptors were severely downregulated. Treatment of the cultures with baclofen after OGD restored GABAB receptor expression and reduced loss of neurons. Restoration of GABAB receptors was due to enhanced fast recycling of the receptors, which reduced OGD-induced sorting of the receptors to lysosomal degradation. Utilizing the middle cerebral artery occlusion (MCAO) mouse model of cerebral ischemia, we verified the severe downregulation of GABAB receptors in the affected cortex and a partial restoration of the receptors after systemic injection of baclofen. Restored receptor expression recovered GABAB receptor-mediated currents, normalized the enhanced neuronal excitability observed after MCAO and limited progressive loss of neurons. These results suggest that baclofen-induced restoration of GABAB receptors provides the basis for the neuroprotective activity of baclofen after an ischemic insult. Since GABAB receptors regulate multiple beneficial pathways, they are promising targets for a neuroprotective strategy in acute cerebral ischemia.
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Affiliation(s)
- Mohammad Hleihil
- Institute of Pharmacology and Toxicology, University Zurich, Zurich, Switzerland.,Neuroscience Center Zurich, ETH Zurich, University of Zurich, Zurich, Switzerland
| | - Markus Vaas
- Institute of Pharmacology and Toxicology, University Zurich, Zurich, Switzerland
| | - Musadiq A Bhat
- Institute of Pharmacology and Toxicology, University Zurich, Zurich, Switzerland
| | - Karthik Balakrishnan
- Institute of Pharmacology and Toxicology, University Zurich, Zurich, Switzerland
| | - Dietmar Benke
- Institute of Pharmacology and Toxicology, University Zurich, Zurich, Switzerland.,Neuroscience Center Zurich, ETH Zurich, University of Zurich, Zurich, Switzerland
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12
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Armbrust F, Bickenbach K, Koudelka T, Tholey A, Pietrzik C, Becker-Pauly C. Phosphorylation of meprin β controls its cell surface abundance and subsequently diminishes ectodomain shedding. FASEB J 2021; 35:e21677. [PMID: 34125978 DOI: 10.1096/fj.202100271r] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2021] [Revised: 04/24/2021] [Accepted: 05/04/2021] [Indexed: 12/18/2022]
Abstract
Meprin β is a zinc-dependent metalloprotease exhibiting a unique cleavage specificity with strong preference for acidic amino acids at the cleavage site. Proteomic studies revealed a diverse substrate pool of meprin β including the interleukin-6 receptor (IL-6R) and the amyloid precursor protein (APP). Dysregulation of meprin β is often associated with pathological conditions such as chronic inflammation, fibrosis, or Alzheimer's disease (AD). The extracellular regulation of meprin β including interactors, sheddases, and activators has been intensively investigated while intracellular regulation has been barely addressed in the literature. This study aimed to analyze C-terminal phosphorylation of meprin β with regard to cell surface expression and proteolytic activity. By immunoprecipitation of endogenous meprin β from the colon cancer cell line Colo320 and subsequent LC-MS analysis, we identified several phosphorylation sites in its C-terminal region. Here, T694 in the C-terminus of meprin β was the most preferred residue after phorbol 12-myristate 13-acetate (PMA) stimulation. We further demonstrated the role of protein kinase C (PKC) isoforms for meprin β phosphorylation and identified the involvement of PKC-α and PKC-β. As a result of phosphorylation, the meprin β activity at the cell surface is reduced and, consequently, the extent of substrate cleavage is diminished. Our data indicate that this decrease of the surface activity is caused by the internalization and degradation of meprin β.
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Affiliation(s)
- Fred Armbrust
- Biochemical Institute, Unit for Degradomics of the Protease Web, University of Kiel, Kiel, Germany
| | - Kira Bickenbach
- Biochemical Institute, Unit for Degradomics of the Protease Web, University of Kiel, Kiel, Germany
| | - Tomas Koudelka
- Systematic Proteomics & Bioanalytics, Institute for Experimental Medicine, University of Kiel, Kiel, Germany
| | - Andreas Tholey
- Systematic Proteomics & Bioanalytics, Institute for Experimental Medicine, University of Kiel, Kiel, Germany
| | - Claus Pietrzik
- Institute for Pathobiochemistry, University Medical Center of the Johannes Gutenberg-University Mainz, Mainz, Germany
| | - Christoph Becker-Pauly
- Biochemical Institute, Unit for Degradomics of the Protease Web, University of Kiel, Kiel, Germany
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13
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Gould NR, Williams KM, Joca HC, Torre OM, Lyons JS, Leser JM, Srikanth MP, Hughes M, Khairallah RJ, Feldman RA, Ward CW, Stains JP. Disparate bone anabolic cues activate bone formation by regulating the rapid lysosomal degradation of sclerostin protein. eLife 2021; 10:e64393. [PMID: 33779549 PMCID: PMC8032393 DOI: 10.7554/elife.64393] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2020] [Accepted: 03/26/2021] [Indexed: 02/06/2023] Open
Abstract
The downregulation of sclerostin in osteocytes mediates bone formation in response to mechanical cues and parathyroid hormone (PTH). To date, the regulation of sclerostin has been attributed exclusively to the transcriptional downregulation of the Sost gene hours after stimulation. Using mouse models and rodent cell lines, we describe the rapid, minute-scale post-translational degradation of sclerostin protein by the lysosome following mechanical load and PTH. We present a model, integrating both new and established mechanically and hormonally activated effectors into the regulated degradation of sclerostin by lysosomes. Using a mouse forelimb mechanical loading model, we find transient inhibition of lysosomal degradation or the upstream mechano-signaling pathway controlling sclerostin abundance impairs subsequent load-induced bone formation by preventing sclerostin degradation. We also link dysfunctional lysosomes to aberrant sclerostin regulation using human Gaucher disease iPSCs. These results reveal how bone anabolic cues post-translationally regulate sclerostin abundance in osteocytes to regulate bone formation.
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Affiliation(s)
- Nicole R Gould
- Department of Orthopaedics, University of Maryland School of MedicineBaltimoreUnited States
| | - Katrina M Williams
- Department of Orthopaedics, University of Maryland School of MedicineBaltimoreUnited States
| | - Humberto C Joca
- Center for Biomedical Engineering and Technology, University of Maryland School of MedicineBaltimoreUnited States
| | - Olivia M Torre
- Department of Orthopaedics, University of Maryland School of MedicineBaltimoreUnited States
| | - James S Lyons
- Department of Orthopaedics, University of Maryland School of MedicineBaltimoreUnited States
| | - Jenna M Leser
- Department of Orthopaedics, University of Maryland School of MedicineBaltimoreUnited States
| | - Manasa P Srikanth
- Department of Microbiology and Immunology, University of Maryland School of MedicineBaltimoreUnited States
| | - Marcus Hughes
- Department of Orthopaedics, University of Maryland School of MedicineBaltimoreUnited States
| | | | - Ricardo A Feldman
- Department of Microbiology and Immunology, University of Maryland School of MedicineBaltimoreUnited States
| | - Christopher W Ward
- Department of Orthopaedics, University of Maryland School of MedicineBaltimoreUnited States
| | - Joseph P Stains
- Department of Orthopaedics, University of Maryland School of MedicineBaltimoreUnited States
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14
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Sun Y, He Y, Yang L, Liang D, Shi W, Zhu X, Jiang Y, Ou C. Manganese induced nervous injury by α-synuclein accumulation via ATP-sensitive K(+) channels and GABA receptors. Toxicol Lett 2020; 332:164-170. [PMID: 32659473 DOI: 10.1016/j.toxlet.2020.07.008] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2020] [Revised: 06/27/2020] [Accepted: 07/06/2020] [Indexed: 02/06/2023]
Abstract
Manganese (Mn) is an environmental pollutant having a toxic effect on Parkinson's disease, with significant damage seen in the neurons of basal ganglia. Hence, Mn pollution is a public health concern. A Sprague-Dawley rat model was used to determine the damage to basal nuclei, and the effect of Mn intake was detected using the Morris water maze test and transmission electron microscopy. The SH-SY5Y cell line was exposed to Mn, and downstream signaling was assessed to determine the mechanism of toxicity. Mn exposure injured neurons, repressing GABAAR receptors and inducing GABABR receptors. The synergistic effect of the GABABR receptor and Kir6.1-SUR1 or Kir6.2-SUR1 was found to be one of the potential factors for the secretion of α-synuclein. The accumulation of α-synuclein regulated downstream factors calmodulin (CAM) cAMP response element-binding protein (CREB), thereby impairing learning and memory. Other genes downstream of CREB, rather than the feedback regulation of CREB, and brain-derived neurotrophic factor might also be involved.
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Affiliation(s)
- Yi Sun
- Department of Toxicology, School of Public Health, Guilin Medical University, Guilin 541004, China
| | - Yonghua He
- Department of Toxicology, School of Public Health, Guilin Medical University, Guilin 541004, China
| | - Lin Yang
- Department of Toxicology, School of Public Health, Guilin Medical University, Guilin 541004, China
| | - Dan Liang
- Department of Toxicology, School of Public Health, Guilin Medical University, Guilin 541004, China
| | - Wenxiang Shi
- Department of Toxicology, School of Public Health, Guilin Medical University, Guilin 541004, China
| | - Xiaonian Zhu
- Department of Toxicology, School of Public Health, Guilin Medical University, Guilin 541004, China
| | - Yueming Jiang
- Department of Toxicology, School of Public Health, Guangxi Medical University, Naning 530021, China
| | - Chaoyan Ou
- Department of Toxicology, School of Public Health, Guilin Medical University, Guilin 541004, China.
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15
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Mechanisms and Regulation of Neuronal GABA B Receptor-Dependent Signaling. Curr Top Behav Neurosci 2020; 52:39-79. [PMID: 32808092 DOI: 10.1007/7854_2020_129] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
γ-Aminobutyric acid B receptors (GABABRs) are broadly expressed throughout the central nervous system where they play an important role in regulating neuronal excitability and synaptic transmission. GABABRs are G protein-coupled receptors that mediate slow and sustained inhibitory actions via modulation of several downstream effector enzymes and ion channels. GABABRs are obligate heterodimers that associate with diverse arrays of proteins to form modular complexes that carry out distinct physiological functions. GABABR-dependent signaling is fine-tuned and regulated through a multitude of mechanisms that are relevant to physiological and pathophysiological states. This review summarizes the current knowledge on GABABR signal transduction and discusses key factors that influence the strength and sensitivity of GABABR-dependent signaling in neurons.
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16
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Li X, Liao Y, Dong Y, Li S, Wang F, Wu R, Yuan Z, Cheng J. Mib2 Deficiency Inhibits Microglial Activation and Alleviates Ischemia-Induced Brain Injury. Aging Dis 2020; 11:523-535. [PMID: 32489699 PMCID: PMC7220279 DOI: 10.14336/ad.2019.0807] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2019] [Accepted: 08/07/2019] [Indexed: 12/20/2022] Open
Abstract
Neuroinflammation plays a critical role in ischemia-induced brain injury. Mib2, an E3 ubiquitin ligase, has been reported to regulate Notch signaling and participate in the peripheral immune system. However, the roles of Mib2 in the nervous system are not well characterized. In this study, we show that Mib2 is involved in lipopolysaccharide (LPS)- and oxygen-glucose deprivation (OGD)-induced microglial activation. Mechanistically, Mib2 interacts with the IKK complex and regulates the activation of NF-κB signaling, thus modulating Notch1 transcription in the microglia. Furthermore, we generated a microglia-specific Mib2 knockout mice and found that microglia-specific deletion of Mib2 significantly alleviates ischemia-induced neuroinflammation and brain injury. Taken together, our results reveal a critical role of Mib2 in microglial activation and ischemia-induced brain injury, thus providing a potential target for the treatment of stroke.
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Affiliation(s)
- Xiaoheng Li
- 1Beijing Institute for Brain Disorders, Capital Medical University, Beijing, China
| | - Yajin Liao
- 2The Brain Science Center, Beijing Institute of Basic Medical Sciences, Beijing, China.,3Center on Translational Neuroscience, College of Life & Environmental Science, Minzu University of China, Beijing, China
| | - Yuan Dong
- 4Department of Biochemistry, Medical College, Qingdao University, Qingdao, Shandong, China
| | - Shuoshuo Li
- 5The State Key Laboratory of Brain and Cognitive Sciences, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
| | - Fengchao Wang
- 6National Institute of Biological Sciences, Beijing, China
| | - Rong Wu
- 2The Brain Science Center, Beijing Institute of Basic Medical Sciences, Beijing, China
| | - Zengqiang Yuan
- 1Beijing Institute for Brain Disorders, Capital Medical University, Beijing, China.,2The Brain Science Center, Beijing Institute of Basic Medical Sciences, Beijing, China
| | - Jinbo Cheng
- 2The Brain Science Center, Beijing Institute of Basic Medical Sciences, Beijing, China.,3Center on Translational Neuroscience, College of Life & Environmental Science, Minzu University of China, Beijing, China
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17
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Direct Interaction of PP2A Phosphatase with GABA B Receptors Alters Functional Signaling. J Neurosci 2020; 40:2808-2816. [PMID: 32111696 PMCID: PMC7117905 DOI: 10.1523/jneurosci.2654-19.2020] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2019] [Revised: 01/02/2020] [Accepted: 02/18/2020] [Indexed: 01/16/2023] Open
Abstract
Addictive drugs usurp the brain's intrinsic mechanism for reward, leading to compulsive and destructive behaviors. In the ventral tegmental area (VTA), the center of the brain's reward circuit, GABAergic neurons control the excitability of dopamine (DA) projection neurons and are the site of initial psychostimulant-dependent changes in signaling. Previous work established that cocaine/methamphetamine exposure increases protein phosphatase 2A (PP2A) activity, which dephosphorylates the GABABR2 subunit, promotes internalization of the GABAB receptor (GABABR) and leads to smaller GABABR-activated G-protein-gated inwardly rectifying potassium (GIRK) currents in VTA GABA neurons. How the actions of PP2A become selective for a particular signaling pathway is poorly understood. Here, we demonstrate that PP2A can associate directly with a short peptide sequence in the C terminal domain of the GABABR1 subunit, and that GABABRs and PP2A are in close proximity in rodent neurons (mouse/rat; mixed sexes). We show that this PP2A-GABABR interaction can be regulated by intracellular Ca2+ Finally, a peptide that potentially reduces recruitment of PP2A to GABABRs and thereby limits receptor dephosphorylation increases the magnitude of baclofen-induced GIRK currents. Thus, limiting PP2A-dependent dephosphorylation of GABABRs may be a useful strategy to increase receptor signaling for treating diseases.SIGNIFICANCE STATEMENT Dysregulation of GABAB receptors (GABABRs) underlies altered neurotransmission in many neurological disorders. Protein phosphatase 2A (PP2A) is involved in dephosphorylating and subsequent internalization of GABABRs in models of addiction and depression. Here, we provide new evidence that PP2A B55 regulatory subunit interacts directly with a small region of the C-terminal domain of the GABABR1 subunit, and that this interaction is sensitive to intracellular Ca2+ We demonstrate that a short peptide corresponding to the PP2A interaction site on GABABR1 competes for PP2A binding, enhances phosphorylation GABABR2 S783, and affects functional signaling through GIRK channels. Our study highlights how targeting PP2A dependent dephosphorylation of GABABRs may provide a specific strategy to modulate GABABR signaling in disease conditions.
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18
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Dubovyk V, Manahan-Vaughan D. Distinct Time-Course of Alterations of Groups I and II Metabotropic Glutamate Receptor and GABAergic Receptor Expression Along the Dorsoventral Hippocampal Axis in an Animal Model of Psychosis. Front Behav Neurosci 2019; 13:98. [PMID: 31139061 PMCID: PMC6519509 DOI: 10.3389/fnbeh.2019.00098] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2018] [Accepted: 04/23/2019] [Indexed: 01/13/2023] Open
Abstract
Psychosis is a clinical state that encompasses a range of abnormal conditions, including distortions in sensory information processing and the resultant delusional thinking, emotional discordance and cognitive impairments. Upon developing this condition, the rate at which cognitive and behavioral deteriorations progress steadily increases suggesting an active contribution of the first psychotic event to the progression of structural and functional abnormalities and disease establishment in diagnosed patients. Changes in GABAergic and glutamatergic function, or expression, in the hippocampus have been proposed as a key factor in the pathophysiology of psychosis. However, little is known as to the time-point of onset of putative changes, to what extent they are progressive, and their relation to disease stabilization. Here, we characterized the expression and distribution patterns of groups I and II metabotropic glutamate (mGlu) receptors and GABA receptors 1 week and 3 months after systemic treatment with an N-methyl-D-aspartate receptor (NMDAR) antagonist (MK801) that is used to model a psychosis-like state in adult rats. We found an early alteration in the expression of mGlu1, mGlu2/3, and GABAB receptors across the hippocampal dorsoventral and transverse axes. This expanded to include an up-regulation of mGlu5 levels across the entire CA1 region and a reduction in GABAB expression, as well as GAD67-positive interneurons particularly in the dorsal hippocampus that appeared 3 months after treatment. Our findings indicate that a reduction of excitability may occur in the hippocampus soon after first-episode psychosis. This changes, over time, into increased excitability. These hippocampus-specific alterations are likely to contribute to the pathophysiology and stabilization of psychosis.
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Affiliation(s)
- Valentyna Dubovyk
- Department of Neurophysiology, Medical Faculty, Ruhr-University Bochum, Bochum, Germany.,International Graduate School of Neuroscience, Ruhr-University Bochum, Bochum, Germany
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19
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TERUNUMA M. Diversity of structure and function of GABA B receptors: a complexity of GABA B-mediated signaling. PROCEEDINGS OF THE JAPAN ACADEMY. SERIES B, PHYSICAL AND BIOLOGICAL SCIENCES 2018; 94:390-411. [PMID: 30541966 PMCID: PMC6374141 DOI: 10.2183/pjab.94.026] [Citation(s) in RCA: 71] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/01/2018] [Accepted: 10/09/2018] [Indexed: 05/24/2023]
Abstract
γ-aminobutyric acid type B (GABAB) receptors are broadly expressed in the nervous system and play an important role in neuronal excitability. GABAB receptors are G protein-coupled receptors that mediate slow and prolonged inhibitory action, via activation of Gαi/o-type proteins. GABAB receptors mediate their inhibitory action through activating inwardly rectifying K+ channels, inactivating voltage-gated Ca2+ channels, and inhibiting adenylate cyclase. Functional GABAB receptors are obligate heterodimers formed by the co-assembly of R1 and R2 subunits. It is well established that GABAB receptors interact not only with G proteins and effectors but also with various proteins. This review summarizes the structure, subunit isoforms, and function of GABAB receptors, and discusses the complexity of GABAB receptors, including how receptors are localized in specific subcellular compartments, the mechanism regulating cell surface expression and mobility of the receptors, and the diversity of receptor signaling through receptor crosstalk and interacting proteins.
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Affiliation(s)
- Miho TERUNUMA
- Division of Oral Biochemistry, Graduate School of Medical and Dental Sciences, Niigata University, Niigata, Japan
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