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Abstract
Biological supramolecular assemblies, such as phospholipid bilayer membranes, have been used to demonstrate signal processing via short-term synaptic plasticity (STP) in the form of paired pulse facilitation and depression, emulating the brain's efficiency and flexible cognitive capabilities. However, STP memory in lipid bilayers is volatile and cannot be stored or accessed over relevant periods of time, a key requirement for learning. Using droplet interface bilayers (DIBs) composed of lipids, water and hexadecane, and an electrical stimulation training protocol featuring repetitive sinusoidal voltage cycling, we show that DIBs displaying memcapacitive properties can also exhibit persistent synaptic plasticity in the form of long-term potentiation (LTP) associated with capacitive energy storage in the phospholipid bilayer. The time scales for the physical changes associated with the LTP range between minutes and hours, and are substantially longer than previous STP studies, where stored energy dissipated after only a few seconds. STP behavior is the result of reversible changes in bilayer area and thickness. On the other hand, LTP is the result of additional molecular and structural changes to the zwitterionic lipid headgroups and the dielectric properties of the lipid bilayer that result from the buildup of an increasingly asymmetric charge distribution at the bilayer interfaces.
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2
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Vigil FA, Giese KP. Calcium/calmodulin-dependent kinase II and memory destabilization: a new role in memory maintenance. J Neurochem 2018; 147:12-23. [PMID: 29704430 PMCID: PMC6221169 DOI: 10.1111/jnc.14454] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2018] [Revised: 03/28/2018] [Accepted: 04/17/2018] [Indexed: 02/03/2023]
Abstract
In this review, we discuss the poorly explored role of calcium/calmodulin-dependent protein kinase II (CaMKII) in memory maintenance, and its influence on memory destabilization. After a brief review on CaMKII and memory destabilization, we present critical pieces of evidence suggesting that CaMKII activity increases retrieval-induced memory destabilization. We then proceed to propose two potential molecular pathways to explain the association between CaMKII activation and increased memory destabilization. This review will pinpoint gaps in our knowledge and discuss some 'controversial' observations, establishing the basis for new experiments on the role of CaMKII in memory reconsolidation. The role of CaMKII in memory destabilization is of great clinical relevance. Still, because of the lack of scientific literature on the subject, more basic science research is necessary to pursue this pathway as a clinical tool.
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Affiliation(s)
- Fabio Antonio Vigil
- Department of Cell and Integrative PhysiologyThe University of Texas Health San Antonio8403, Floyd Curl DriveSan AntonioTX 78229USA
| | - Karl Peter Giese
- Department of Basic and Clinical NeuroscienceKing's College London125 Coldharbour LaneLondonSE5 9NUUK
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3
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Sweatt JD. Neural plasticity and behavior - sixty years of conceptual advances. J Neurochem 2016; 139 Suppl 2:179-199. [PMID: 26875778 DOI: 10.1111/jnc.13580] [Citation(s) in RCA: 187] [Impact Index Per Article: 23.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2015] [Revised: 01/19/2016] [Accepted: 02/09/2016] [Indexed: 02/06/2023]
Abstract
This brief review summarizes 60 years of conceptual advances that have demonstrated a role for active changes in neuronal connectivity as a controller of behavior and behavioral change. Seminal studies in the first phase of the six-decade span of this review firmly established the cellular basis of behavior - a concept that we take for granted now, but which was an open question at the time. Hebbian plasticity, including long-term potentiation and long-term depression, was then discovered as being important for local circuit refinement in the context of memory formation and behavioral change and stabilization in the mammalian central nervous system. Direct demonstration of plasticity of neuronal circuit function in vivo, for example, hippocampal neurons forming place cell firing patterns, extended this concept. However, additional neurophysiologic and computational studies demonstrated that circuit development and stabilization additionally relies on non-Hebbian, homoeostatic, forms of plasticity, such as synaptic scaling and control of membrane intrinsic properties. Activity-dependent neurodevelopment was found to be associated with cell-wide adjustments in post-synaptic receptor density, and found to occur in conjunction with synaptic pruning. Pioneering cellular neurophysiologic studies demonstrated the critical roles of transmembrane signal transduction, NMDA receptor regulation, regulation of neural membrane biophysical properties, and back-propagating action potential in critical time-dependent coincidence detection in behavior-modifying circuits. Concerning the molecular mechanisms underlying these processes, regulation of gene transcription was found to serve as a bridge between experience and behavioral change, closing the 'nature versus nurture' divide. Both active DNA (de)methylation and regulation of chromatin structure have been validated as crucial regulators of gene transcription during learning. The discovery of protein synthesis dependence on the acquisition of behavioral change was an influential discovery in the neurochemistry of behavioral modification. Higher order cognitive functions such as decision making and spatial and language learning were also discovered to hinge on neural plasticity mechanisms. The role of disruption of these processes in intellectual disabilities, memory disorders, and drug addiction has recently been clarified based on modern genetic techniques, including in the human. The area of neural plasticity and behavior has seen tremendous advances over the last six decades, with many of those advances being specifically in the neurochemistry domain. This review provides an overview of the progress in the area of neuroplasticity and behavior over the life-span of the Journal of Neurochemistry. To organize the broad literature base, the review collates progress into fifteen broad categories identified as 'conceptual advances', as viewed by the author. The fifteen areas are delineated in the figure above. This article is part of the 60th Anniversary special issue.
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Affiliation(s)
- J David Sweatt
- Department of Neurobiology, Evelyn F. McKnight Brain Institute and Civitan International Research Center, University of Alabama at Birmingham, Birmingham, Alabama, USA.
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4
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Gu W, Fukuda T, Isaji T, Hang Q, Lee HH, Sakai S, Morise J, Mitoma J, Higashi H, Taniguchi N, Yawo H, Oka S, Gu J. Loss of α1,6-Fucosyltransferase Decreases Hippocampal Long Term Potentiation: IMPLICATIONS FOR CORE FUCOSYLATION IN THE REGULATION OF AMPA RECEPTOR HETEROMERIZATION AND CELLULAR SIGNALING. J Biol Chem 2015; 290:17566-75. [PMID: 25979332 DOI: 10.1074/jbc.m114.579938] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2014] [Indexed: 01/01/2023] Open
Abstract
Core fucosylation is catalyzed by α1,6-fucosyltransferase (FUT8), which transfers a fucose residue to the innermost GlcNAc residue via α1,6-linkage on N-glycans in mammals. We previously reported that Fut8-knock-out (Fut8(-/-)) mice showed a schizophrenia-like phenotype and a decrease in working memory. To understand the underlying molecular mechanism, we analyzed early form long term potentiation (E-LTP), which is closely related to learning and memory in the hippocampus. The scale of E-LTP induced by high frequency stimulation was significantly decreased in Fut8(-/-) mice. Tetraethylammonium-induced LTP showed no significant differences, suggesting that the decline in E-LTP was caused by postsynaptic events. Unexpectedly, the phosphorylation levels of calcium/calmodulin-dependent protein kinase II (CaMKII), an important mediator of learning and memory in postsynapses, were greatly increased in Fut8(-/-) mice. The expression levels of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionate receptors (AMPARs) in the postsynaptic density were enhanced in Fut8(-/-) mice, although there were no significant differences in the total expression levels, implicating that AMPARs without core fucosylation might exist in an active state. The activation of AMPARs was further confirmed by Fura-2 calcium imaging using primary cultured neurons. Taken together, loss of core fucosylation on AMPARs enhanced their heteromerization, which increase sensitivity for postsynaptic depolarization and persistently activate N-methyl-d-aspartate receptors as well as Ca(2+) influx and CaMKII and then impair LTP.
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Affiliation(s)
- Wei Gu
- From the Division of Regulatory Glycobiology and
| | | | - Tomoya Isaji
- From the Division of Regulatory Glycobiology and
| | - Qinglei Hang
- From the Division of Regulatory Glycobiology and
| | - Ho-hsun Lee
- From the Division of Regulatory Glycobiology and
| | - Seiichiro Sakai
- the Graduate School of Life Sciences, Tohoku University, Sendai, Miyagi, 980-8577
| | - Jyoji Morise
- the Department of Biological Chemistry, Human Health Sciences, Graduate School of Medicine, Kyoto University, Kyoto, 606-8507, and
| | - Junya Mitoma
- the Division of Glyco-Signal Research, Tohoku Pharmaceutical University, Sendai, Miyagi, 981-8558
| | - Hideyoshi Higashi
- the Division of Glyco-Signal Research, Tohoku Pharmaceutical University, Sendai, Miyagi, 981-8558
| | | | - Hiromu Yawo
- the Graduate School of Life Sciences, Tohoku University, Sendai, Miyagi, 980-8577
| | - Shogo Oka
- the Department of Biological Chemistry, Human Health Sciences, Graduate School of Medicine, Kyoto University, Kyoto, 606-8507, and
| | - Jianguo Gu
- From the Division of Regulatory Glycobiology and
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5
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Baucum AJ, Shonesy BC, Rose KL, Colbran RJ. Quantitative proteomics analysis of CaMKII phosphorylation and the CaMKII interactome in the mouse forebrain. ACS Chem Neurosci 2015; 6:615-31. [PMID: 25650780 PMCID: PMC4609176 DOI: 10.1021/cn500337u] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Ca(2+)/calmodulin-dependent protein kinase IIα (CaMKIIα) autophosphorylation at Thr286 and Thr305/Thr306 regulates kinase activity and modulates subcellular targeting and is critical for normal synaptic plasticity and learning and memory. Here, a mass spectrometry-based approach was used to identify Ca(2+)-dependent and -independent in vitro autophosphorylation sites in recombinant CaMKIIα and CaMKIIβ. CaMKII holoenzymes were then immunoprecipitated from subcellular fractions of forebrains isolated from either wild-type (WT) mice or mice with a Thr286 to Ala knock-in mutation of CaMKIIα (T286A-KI mice) and analyzed using the same approach in order to characterize in vivo phosphorylation sites in both CaMKII isoforms and identify CaMKII-associated proteins (CaMKAPs). A total of six and seven autophosphorylation sites in CaMKIIα and CaMKIIβ, respectively, were detected in WT mice. Thr286-phosphorylated CaMKIIα and Thr287-phosphorylated CaMKIIβ were selectively enriched in WT Triton-insoluble (synaptic) fractions compared to Triton-soluble (membrane) and cytosolic fractions. In contrast, Thr306-phosphorylated CaMKIIα and Ser315- and Thr320/Thr321-phosphorylated CaMKIIβ were selectively enriched in WT cytosolic fractions. The T286A-KI mutation significantly reduced levels of phosphorylation of CaMKIIα at Ser275 across all subcellular fractions and of cytosolic CaMKIIβ at Ser315 and Thr320/Thr321. Significantly more CaMKAPs coprecipitated with WT CaMKII holoenzymes in the synaptic fraction compared to that in the membrane fraction, with functions including scaffolding, microtubule organization, actin organization, ribosomal function, vesicle trafficking, and others. The T286A-KI mutation altered the interactions of multiple CaMKAPs with CaMKII, including several proteins linked to autism spectrum disorders. These data identify CaMKII isoform phosphorylation sites and a network of synaptic protein interactions that are sensitive to the abrogation of Thr286 autophosphorylation of CaMKIIα, likely contributing to the diverse synaptic and behavioral deficits of T286A-KI mice.
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Affiliation(s)
- Anthony J Baucum
- ⊥Department of Biology and Stark Neurosciences Research Institute, Indiana University-Purdue University Indianapolis, Indianapolis, Indiana 46202, United States
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6
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Galván EJ, Pérez-Rosello T, Gómez-Lira G, Lara E, Gutiérrez R, Barrionuevo G. Synapse-specific compartmentalization of signaling cascades for LTP induction in CA3 interneurons. Neuroscience 2015; 290:332-45. [PMID: 25637803 DOI: 10.1016/j.neuroscience.2015.01.024] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2014] [Revised: 01/15/2015] [Accepted: 01/15/2015] [Indexed: 11/28/2022]
Abstract
Inhibitory interneurons with somata in strata radiatum and lacunosum-molecular (SR/L-M) of hippocampal area CA3 receive excitatory input from pyramidal cells via the recurrent collaterals (RCs), and the dentate gyrus granule cells via the mossy fibers (MFs). Here we demonstrate that Hebbian long-term potentiation (LTP) at RC synapses on SR/L-M interneurons requires the concomitant activation of calcium-impermeable AMPARs (CI-AMPARs) and N-methyl-d-aspartate receptors (NMDARs). RC LTP was prevented by voltage clamping the postsynaptic cell during high-frequency stimulation (HFS; 3 trains of 100 pulses delivered at 100 Hz every 10s), with intracellular injections of the Ca(2+) chelator BAPTA (20mM), and with the NMDAR antagonist D-AP5. In separate experiments, RC and MF inputs converging onto the same interneuron were sequentially activated. We found that RC LTP induction was blocked by inhibitors of the calcium/calmodulin-dependent protein kinase II (CaMKII; KN-62, 10 μM or KN-93, 10 μM) but MF LTP was CaMKII independent. Conversely, the application of the protein kinase A (PKA) activators forskolin/IBMX (50 μM/25 μM) potentiated MF EPSPs but not RC EPSPs. Together these data indicate that the aspiny dendrites of SR/L-M interneurons compartmentalize synapse-specific Ca(2+) signaling required for LTP induction at RC and MF synapses. We also show that the two signal transduction cascades converge to activate a common effector, protein kinase C (PKC). Specifically, LTP at RC and MF synapses on the same SR/LM interneuron was blocked by postsynaptic injections of chelerythrine (10 μM). These data indicate that both forms of LTP share a common mechanism involving PKC-dependent signaling modulation.
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Affiliation(s)
- E J Galván
- Departamento de Farmacobiología, Cinvestav Sede Sur, México City, Mexico.
| | - T Pérez-Rosello
- Department of Physiology, Northwestern University, Chicago, IL, USA
| | - G Gómez-Lira
- Departamento de Farmacobiología, Cinvestav Sede Sur, México City, Mexico
| | - E Lara
- Departamento de Farmacobiología, Cinvestav Sede Sur, México City, Mexico
| | - R Gutiérrez
- Departamento de Farmacobiología, Cinvestav Sede Sur, México City, Mexico
| | - G Barrionuevo
- Department of Neuroscience, University of Pittsburgh, Pittsburgh, PA, USA
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7
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Michalski PJ. The delicate bistability of CaMKII. Biophys J 2014; 105:794-806. [PMID: 23931327 DOI: 10.1016/j.bpj.2013.06.038] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2013] [Revised: 06/13/2013] [Accepted: 06/25/2013] [Indexed: 01/08/2023] Open
Abstract
Calcium/calmodulin-dependent protein kinase II (CaMKII) is a synaptic, autophosphorylating kinase that is essential for learning and memory. Previous models have suggested that CaMKII functions as a bistable switch that could be the molecular correlate of long-term memory, but experiments have failed to validate these predictions. These models involved significant approximations to overcome the combinatorial complexity inherent in a multisubunit, multistate system. Here, we develop a stochastic particle-based model of CaMKII activation and dynamics that overcomes combinatorial complexity without significant approximations. We report four major findings. First, the CaMKII model system is never bistable at resting calcium concentrations, which suggests that CaMKII activity does not function as the biochemical switch underlying long-term memory. Second, the steady-state activation curves are either laserlike or steplike. Both are characterized by a well-defined threshold for activation, which suggests that thresholding is a robust feature of this system. Third, transiently activated CaMKII can maintain its activity over the time course of many experiments, and such slow deactivation may account for the few reports of bistability in the literature. And fourth, under in vivo conditions, increases in phosphatase activity can increase CaMKII activity. This is a surprising and counterintuitive effect, as dephosphorylation is generally associated with CaMKII deactivation.
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Affiliation(s)
- P J Michalski
- Richard D. Berlin Center for Cell Analysis and Modeling, University of Connecticut Health Center, Farmington, Connecticut, USA.
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8
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Gomez-Monterrey I, Sala M, Rusciano MR, Monaco S, Maione AS, Iaccarino G, Tortorella P, D'Ursi AM, Scrima M, Carotenuto A, De Rosa G, Bertamino A, Vernieri E, Grieco P, Novellino E, Illario M, Campiglia P. Characterization of a selective CaMKII peptide inhibitor. Eur J Med Chem 2013; 62:425-34. [PMID: 23395965 DOI: 10.1016/j.ejmech.2012.12.053] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2012] [Revised: 12/11/2012] [Accepted: 12/13/2012] [Indexed: 11/19/2022]
Abstract
Analogs of potent CaMKinase II inhibitor, CaM-KNtide, were prepared to explore new structural requirements for the inhibitory activity. The full potency of CaMKII inhibition by CaM-KIINα is contained within a minimal region of 19 amino acids. Here, analysis of the homologous CaM-KIINβ showed that a 17 mer peptide (CN17β) was the shortest sequence that still retained useful inhibitory potency. Ala substitution of almost any residue of CN17β dramatically reduced potency, except for substitution of P3, R14, and V16. Fusion with the tat sequence generated the cell-penetrating inhibitor version tat-5. This tat-5 fusion peptide maintained selectivity for CaMKII over CaMKI and CaMKIV, and appeared to slightly further enhance potency (IC50 ∼30 nM). Within a breast cancer cell line and in primary human fibroblasts, tat-5 inhibited the Erk signaling pathway and proliferation without any measurable cytotoxicity. Structural analysis of CN17β by CD and NMR indicated an α-helix conformation in the Leu6-Arg11 segment well overlapping with the crystal structure of 21-residue segment of CaM-KNtide bound to the kinase domain of CaMKII.
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Affiliation(s)
- Isabel Gomez-Monterrey
- Depart. of Pharmaceutical and Toxicological Chemistry, University of Naples Federico II, Naples, Italy
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9
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Selective kinase inhibitors as tools for neuroscience research. Neuropharmacology 2012; 63:1227-37. [DOI: 10.1016/j.neuropharm.2012.07.024] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2012] [Revised: 07/06/2012] [Accepted: 07/11/2012] [Indexed: 01/02/2023]
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10
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Abstract
Cardiac myocyte function is dependent on the synchronized movements of Ca(2+) into and out of the cell, as well as between the cytosol and sarcoplasmic reticulum. These movements determine cardiac rhythm and regulate excitation-contraction coupling. Ca(2+) cycling is mediated by a number of critical Ca(2+)-handling proteins and transporters, such as L-type Ca(2+) channels (LTCCs) and sodium/calcium exchangers in the sarcolemma, and sarcoplasmic/endoplasmic reticulum calcium ATPase 2a (SERCA2a), ryanodine receptors, and cardiac phospholamban in the sarcoplasmic reticulum. The entry of Ca(2+) into the cytosol through LTCCs activates the release of Ca(2+) from the sarcoplasmic reticulum through ryanodine receptor channels and initiates myocyte contraction, whereas SERCA2a and cardiac phospholamban have a key role in sarcoplasmic reticulum Ca(2+) sequesteration and myocyte relaxation. Excitation-contraction coupling is regulated by phosphorylation of Ca(2+)-handling proteins. Abnormalities in sarcoplasmic reticulum Ca(2+) cycling are hallmarks of heart failure and contribute to the pathophysiology and progression of this disease. Correcting impaired intracellular Ca(2+) cycling is a promising new approach for the treatment of heart failure. Novel therapeutic strategies that enhance myocyte Ca(2+) homeostasis could prevent and reverse adverse cardiac remodeling and improve clinical outcomes in patients with heart failure.
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11
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Viggiano A, Serù R, Damiano S, De Luca B, Santillo M, Mondola P. Inhibition of long-term potentiation by CuZn superoxide dismutase injection in rat dentate gyrus: involvement of muscarinic M1 receptor. J Cell Physiol 2012; 227:3111-5. [PMID: 22015651 DOI: 10.1002/jcp.23062] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Long-term potentiation (LTP) and long-term depression represent important processes that modulate synaptic transmission that carries out a key role in neural mechanisms of memory. Many studies give strong evidences on a role of the reactive oxygen species in the induction of LTP in CA1 region of hippocampal slices that was inhibited by adding the scavenger enzyme superoxide dismutase (SOD1). Previous data showed that SOD1 is secreted by many cellular lines, including neuroblastoma SK-N-BE cells through microvesicles by an ATP-dependent mechanism; moreover, it has been shown that SOD1 interacts with human neuroblastoma cell membranes increasing intracellular calcium levels via a phospholipase C-protein kinase C pathway activation. The aim of this study was to investigate the effect of intracerebral injection of SOD1 or the inactive form of enzyme (ApoSOD) on the modulation of synaptic transmission in dentate gyrus of the hippocampus in urethane anesthetized rats. The results of the present research showed that intracerebral injection of SOD1 and ApoSOD in the dentate gyrus of the rat hippocampal formation inhibits LTP induced by high-frequency stimulation of the perforant path. This result cannot be only explained by the dismutation of oxygen radical induced by SOD1 since also ApoSOD, that lacks the enzymatic activity, carries out the same inhibitory effect on LTP induction.
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Affiliation(s)
- A Viggiano
- Department of Experimental Medicine, Section of Human Physiology, Second University of Naples, Naples, Italy
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12
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Coultrap SJ, Bayer KU. CaMKII regulation in information processing and storage. Trends Neurosci 2012; 35:607-18. [PMID: 22717267 DOI: 10.1016/j.tins.2012.05.003] [Citation(s) in RCA: 246] [Impact Index Per Article: 20.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2012] [Revised: 05/07/2012] [Accepted: 05/11/2012] [Indexed: 11/29/2022]
Abstract
The Ca(2+)/Calmodulin(CaM)-dependent protein kinase II (CaMKII) is activated by Ca(2+)/CaM, but becomes partially autonomous (Ca(2+)-independent) upon autophosphorylation at T286. This hallmark feature of CaMKII regulation provides a form of molecular memory and is indeed important in long-term potentiation (LTP) of excitatory synapse strength and memory formation. However, emerging evidence supports a direct role in information processing, while storage of synaptic information may instead be mediated by regulated interaction of CaMKII with the NMDA receptor (NMDAR) complex. These and other CaMKII regulation mechanisms are discussed here in the context of the kinase structure and their impact on postsynaptic functions. Recent findings also implicate CaMKII in long-term depression (LTD), as well as functional roles at inhibitory synapses, lending renewed emphasis on better understanding the spatiotemporal control of CaMKII regulation.
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Affiliation(s)
- Steven J Coultrap
- Department of Pharmacology, University of Colorado Denver School of Medicine, Aurora, CO 80045, USA
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13
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Abstract
Synaptic plasticity, or changes in synaptic strength, is thought to underlie learning and memory. Imaging studies, mainly in brain slices, have revealed that long-term synaptic plasticity of excitatory synapses in hippocampal neurons is coupled with structural plasticity of dendritic spines, which is thought to be essential for inducing and regulating functional plasticity. Using pharmacological and genetic manipulation, the signalling network underlying structural plasticity has been extensively studied. Furthermore, the recent advent of fluorescence resonance energy transfer (FRET) imaging techniques has provided a readout of the dynamics of signal transduction in dendritic spines undergoing structural plasticity. These studies reveal the signalling pathways relaying Ca2+ to the functional and structural plasticity of dendritic spines.
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Affiliation(s)
- Michael Patterson
- Department of Neurobiology, Howard Hughes Medical Institute, Duke University Medical Center, Durham, NC 27710, USA
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14
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Network, cellular, and molecular mechanisms underlying long-term memory formation. Curr Top Behav Neurosci 2012; 15:73-115. [PMID: 22976275 DOI: 10.1007/7854_2012_229] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The neural network stores information through activity-dependent synaptic plasticity that occurs in populations of neurons. Persistent forms of synaptic plasticity may account for long-term memory storage, and the most salient forms are the changes in the structure of synapses. The theory proposes that encoding should use a sparse code and evidence suggests that this can be achieved through offline reactivation or by sparse initial recruitment of the network units. This idea implies that in some cases the neurons that underwent structural synaptic plasticity might be a subpopulation of those originally recruited; However, it is not yet clear whether all the neurons recruited during acquisition are the ones that underwent persistent forms of synaptic plasticity and responsible for memory retrieval. To determine which neural units underlie long-term memory storage, we need to characterize which are the persistent forms of synaptic plasticity occurring in these neural ensembles and the best hints so far are the molecular signals underlying structural modifications of the synapses. Structural synaptic plasticity can be achieved by the activity of various signal transduction pathways, including the NMDA-CaMKII and ACh-MAPK. These pathways converge with the Rho family of GTPases and the consequent ERK 1/2 activation, which regulates multiple cellular functions such as protein translation, protein trafficking, and gene transcription. The most detailed explanation may come from models that allow us to determine the contribution of each piece of this fascinating puzzle that is the neuron and the neural network.
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15
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Abstract
Ischemic insults on neurons trigger excessive, pathological glutamate release that causes Ca²⁺ overload resulting in neuronal cell death (excitotoxicity). The Ca²⁺/calmodulin (CaM)-dependent protein kinase II (CaMKII) is a major mediator of physiological excitatory glutamate signals underlying neuronal plasticity and learning. Glutamate stimuli trigger autophosphorylation of CaMKII at T286, a process that makes the kinase "autonomous" (partially active independent from Ca²⁺ stimulation) and that is required for forms of synaptic plasticity. Recent studies suggested autonomous CaMKII activity also as potential drug target for post-insult neuroprotection, both after glutamate insults in neuronal cultures and after focal cerebral ischemia in vivo. However, CaMKII and other members of the CaM kinase family have been implicated in regulation of both neuronal death and survival. Here, we discuss past findings and possible mechanisms of CaM kinase functions in excitotoxicity and cerebral ischemia, with a focus on CaMKII and its regulation.
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16
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Analysis of CaM-kinase signaling in cells. Cell Calcium 2011; 50:1-8. [PMID: 21529938 DOI: 10.1016/j.ceca.2011.02.007] [Citation(s) in RCA: 91] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2010] [Revised: 02/15/2011] [Accepted: 02/17/2011] [Indexed: 12/18/2022]
Abstract
A change in intracellular free calcium is a common signaling mechanism that modulates a wide array of physiological processes in most cells. Responses to increased intracellular Ca(2+) are often mediated by the ubiquitous protein calmodulin (CaM) that upon binding Ca(2+) can interact with and alter the functionality of numerous proteins including a family of protein kinases referred to as CaM-kinases (CaMKs). Of particular interest are multifunctional CaMKs, such as CaMKI, CaMKII, CaMKIV and CaMKK, that can phosphorylate multiple downstream targets. This review will outline several protocols we have used to identify which members and/or isoforms of this CaMK family mediate specific cellular responses with a focus on studies in neurons. Many previous studies have relied on a single approach such as pharmacological inhibitors or transfected dominant-negative kinase constructs. Since each of these protocols has its limitations, that will be discussed, we emphasize the necessity to use multiple, independent approaches in mapping out cellular signaling pathways.
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17
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Brooks IM, Tavalin SJ. Ca2+/calmodulin-dependent protein kinase II inhibitors disrupt AKAP79-dependent PKC signaling to GluA1 AMPA receptors. J Biol Chem 2010; 286:6697-706. [PMID: 21156788 DOI: 10.1074/jbc.m110.183558] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
GluA1 (formerly GluR1) AMPA receptor subunit phosphorylation at Ser-831 is an early biochemical marker for long-term potentiation and learning. This site is a substrate for Ca(2+)/calmodulin (CaM)-dependent protein kinase II (CaMKII) and protein kinase C (PKC). By directing PKC to GluA1, A-kinase anchoring protein 79 (AKAP79) facilitates Ser-831 phosphorylation and makes PKC a more potent regulator of GluA1 than CaMKII. PKC and CaM bind to residues 31-52 of AKAP79 in a competitive manner. Here, we demonstrate that common CaMKII inhibitors alter PKC and CaM interactions with AKAP79(31-52). Most notably, the classical CaMKII inhibitors KN-93 and KN-62 potently enhanced the association of CaM to AKAP79(31-52) in the absence (apoCaM) but not the presence of Ca(2+). In contrast, apoCaM association to AKAP79(31-52) was unaffected by the control compound KN-92 or a mechanistically distinct CaMKII inhibitor (CaMKIINtide). In vitro studies demonstrated that KN-62 and KN-93, but not the other compounds, led to apoCaM-dependent displacement of PKC from AKAP79(31-52). In the absence of CaMKII activation, complementary cellular studies revealed that KN-62 and KN-93, but not KN-92 or CaMKIINtide, inhibited PKC-mediated phosphorylation of GluA1 in hippocampal neurons as well as AKAP79-dependent PKC-mediated augmentation of recombinant GluA1 currents. Buffering cellular CaM attenuated the ability of KN-62 and KN-93 to inhibit AKAP79-anchored PKC regulation of GluA1. Therefore, by favoring apoCaM binding to AKAP79, KN-62 and KN-93 derail the ability of AKAP79 to efficiently recruit PKC for regulation of GluA1. Thus, AKAP79 endows PKC with a pharmacological profile that overlaps with CaMKII.
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Affiliation(s)
- Ian M Brooks
- Department of Pharmacology, University of Tennessee Health Science Center, Memphis, Tennessee 38163, USA
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Tang J, Bouyer P, Mykoniatis A, Buschmann M, Matlin KS, Matthews JB. Activated PKC{delta} and PKC{epsilon} inhibit epithelial chloride secretion response to cAMP via inducing internalization of the Na+-K+-2Cl- cotransporter NKCC1. J Biol Chem 2010; 285:34072-85. [PMID: 20732874 DOI: 10.1074/jbc.m110.137380] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
The basolateral Na(+)-K(+)-2Cl(-) cotransporter (NKCC1) is a key determinant of transepithelial chloride secretion and dysregulation of chloride secretion is a common feature of many diseases including secretory diarrhea. We have previously shown that activation of protein kinase C (PKC) markedly reduces transepithelial chloride secretion in human colonic T84 cells, which correlates with both functional inhibition and loss of the NKCC1 surface expression. In the present study, we defined the specific roles of PKC isoforms in regulating epithelial NKCC1 and chloride secretion utilizing adenoviral vectors that express shRNAs targeting human PKC isoforms (α, δ, ε) (shPKCs) or LacZ (shLacZ, non-targeting control). After 72 h of adenoviral transduction, protein levels of the PKC isoforms in shPKCs-T84 cells were decreased by ∼90% compared with the shLacZ-control. Activation of PKCs by phorbol 12-myristate 13-acetate (PMA) caused a redistribution of NKCC1 immunostaining from the basolateral membrane to intracellular vesicles in both shLacZ- and shPKCα-T84 cells, whereas the effect of PMA was not observed in shPKCδ- and shPKCε- cells. These results were further confirmed by basolateral surface biotinylation. Furthermore, activation of PKCs by PMA inhibited cAMP-stimulated chloride secretion in the uninfected, shLacZ- and shPKCα-T84 monolayers, but the inhibitory effect was significantly attenuated in shPKCδ- and shPKCε-T84 monolayers. In conclusion, the activated novel isoforms PKCδ or PKCε, but not the conventional isoform PKCα, inhibits transepithelial chloride secretion through inducing internalization of the basolateral surface NKCC1. Our study reveals that the novel PKC isoform-regulated NKCC1 surface expression plays an important role in the regulation of chloride secretion.
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Affiliation(s)
- Jun Tang
- Department of Surgery, The University of Chicago, Chicago, Illinois 60637, USA
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Vest RS, O'Leary H, Coultrap SJ, Kindy MS, Bayer KU. Effective post-insult neuroprotection by a novel Ca(2+)/ calmodulin-dependent protein kinase II (CaMKII) inhibitor. J Biol Chem 2010; 285:20675-82. [PMID: 20424167 DOI: 10.1074/jbc.m109.088617] [Citation(s) in RCA: 93] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Ca(2+)/calmodulin (CaM)-dependent protein kinase II (CaMKII) is a major mediator of physiological glutamate signaling involved in higher brain functions. Here, we show CaMKII involvement in pathological glutamate signaling relevant in stroke. The novel inhibitor tatCN21 was neuroprotective even when added hours after glutamate insults. By contrast, the "traditional" inhibitor KN93 attenuated excitotoxicity only when present during the insult. Both inhibitors efficiently blocked Ca(2+)/CaM-stimulated CaMKII activity, CaMKII interaction with NR2B and aggregation of CaMKII holoenzymes. However, only tatCN21 but not KN93 blocked the Ca(2+)-independent "autonomous" activity generated by Thr-286 autophosphorylation, the hallmark feature of CaMKII regulation. Mutational analysis further validated autonomous CaMKII activity as the drug target crucial for post-insult neuroprotection. Overexpression of CaMKII wild type but not the autonomy-deficient T286A mutant significantly increased glutamate-induced neuronal death. Maybe most importantly, tatCN21 also significantly reduced infarct size in a mouse stroke model (middle cerebral arterial occlusion) when injected (1 mg/kg intravenously) 1 h after onset of arterial occlusion. Together, these data demonstrate that inhibition of autonomous CaMKII activity provides a promising therapeutic avenue for post-insult neuro-protection after stroke.
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Affiliation(s)
- Rebekah S Vest
- Department of Pharmacology, University of Colorado Denver School of Medicine, Aurora, CO 80045, USA
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20
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Wittkop L, Schwarz A, Cassany A, Grün-Bernhard S, Delaleau M, Rabe B, Cazenave C, Gerlich W, Glebe D, Kann M. Inhibition of protein kinase C phosphorylation of hepatitis B virus capsids inhibits virion formation and causes intracellular capsid accumulation. Cell Microbiol 2010; 12:962-75. [PMID: 20109160 DOI: 10.1111/j.1462-5822.2010.01444.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Capsids of hepatitis B virus and other hepadnaviruses contain a cellular protein kinase, which phosphorylates the capsid protein. Some phosphorylation sites are shown to be essential for distinct steps of viral replication as pregenome packaging or plus strand DNA synthesis. Although different protein kinases have been reported to phosphorylate the capsid protein, varying experimental approaches do not allow direct comparison. Furthermore, the activity of a specific protein kinase has not yet been correlated to steps in the hepadnaviral life cycle. In this study we show that capsids from various sources encapsidate active protein kinase Calpha, irrespective of hepatitis B virus genotype and host cell. Treatment of a virion expressing cell line with a pseudosubstrate inhibitor showed that inhibition of protein kinase C phosphorylation did not affect genome maturation but resulted in capsid accumulation and inhibited virion release to the medium. Our results imply that different protein kinases have distinct functions within the hepadnaviral life cycle.
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Affiliation(s)
- Linda Wittkop
- Institute of Medical Virology, Justus Liebig University, Frankfurter Strasse 107, D-35392 Giessen, Germany
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21
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Bittins CM, Eichler TW, Gerdes HH. Expression of the dominant-negative tail of myosin Va enhances exocytosis of large dense core vesicles in neurons. Cell Mol Neurobiol 2009; 29:597-608. [PMID: 19214741 DOI: 10.1007/s10571-009-9352-z] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2008] [Accepted: 01/13/2009] [Indexed: 12/11/2022]
Abstract
Regulated exocytosis of secretory vesicles is a fundamental process in neurotransmission and the release of hormones and growth factors. The F-actin-binding motor protein myosin Va was recently shown to be involved in exocytosis of peptide-containing large dense core vesicles of neuroendocrine cells. It has not previously been discussed whether it plays a similar role in neurons. We performed live-cell imaging of cultured hippocampal neurons to measure the exocytosis of large dense core vesicles containing fluorescently labelled neuropeptide Y. To address the role of myosin Va in this process, neurons were transfected with the dominant-negative tail domain of myosin Va (myosinVa-tail). Under control conditions, about 0.75% of the labelled large dense core vesicles underwent exocytosis during 5 min of stimulation. This value was doubled to 1.80% of the vesicles when myosinVa-tail was expressed. Depolymerization of F-actin using latrunculin B resulted in a similar increase in exocytosis in both control and myosinVa-tail expressing cells. Interestingly, the increase in exocytosis caused by myosinVa-tail expression was completely abolished in the presence of KN-62, an inhibitor of calcium-calmodulin-dependent kinase II. We suggest that myosinVa-tail causes the liberation of large dense core vesicles from the actin cytoskeleton, leading to an increase in exocytosis in the cultured hippocampal neurons.
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22
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Wang W, Rupasinghe SG, Schuler MA, Gonzalez de Mejia E. Identification and characterization of topoisomerase II inhibitory peptides from soy protein hydrolysates. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2008; 56:6267-6277. [PMID: 18593177 DOI: 10.1021/jf8005195] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Topoisomerases are targets of several anticancer agents because their inhibition impedes the processes of cell proliferation and differentiation in carcinogenesis. With very limited information available on the inhibitory activities of peptides derived from dietary proteins, the objectives of this study were to employ co-immunoprecipitation to identify inhibitory peptides in soy protein hydrolysates in a single step and to investigate their molecular interactions with topoisomerase II. For this, soy protein isolates were subjected to simulated gastrointestinal digestion with pepsin and pancreatin, and the human topoisomerase II inhibitory peptides were co-immunoprecipitated and identified on a CapLC- Micromass Q-TOF Ultima API system. The inhibitory activity of these peptides from soy isolates toward topoisomerase II was confirmed using three synthetic peptides, FEITPEKNPQ, IETWNPNNKP,and VFDGEL, which have IC 50 values of 2.4, 4.0, and 7.9 mM, respectively. The molecular interactions of these peptides evaluated by molecular docking revealed interaction energies with the topoisomerase II C-terminal domain (CTD) (-186 to -398 kcal/mol) that were smaller than for the ATPase domain (-169 to -357 kcal/mol) and that correlated well with our experimental IC 50 values ( R (2) = 0.99). In conclusion, three peptides released from in vitro gastrointestinal enzyme digestion of soy proteins inhibited human topoisomerase II activity through binding to the active site of the CTD domain.
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Affiliation(s)
- Wenyi Wang
- Department of Food Science and Human Nutrition and Department of Cell and Developmental Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
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23
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Vest RS, Davies KD, O'Leary H, Port JD, Bayer KU. Dual mechanism of a natural CaMKII inhibitor. Mol Biol Cell 2007; 18:5024-33. [PMID: 17942605 DOI: 10.1091/mbc.e07-02-0185] [Citation(s) in RCA: 147] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Ca(2+)/calmodulin (CaM)-dependent protein kinase II (CaMKII) is a major mediator of cellular Ca(2+) signaling. Several inhibitors are commonly used to study CaMKII function, but these inhibitors all lack specificity. CaM-KIIN is a natural, specific CaMKII inhibitor protein. CN21 (derived from CaM-KIIN amino acids 43-63) showed full specificity and potency of CaMKII inhibition. CNs completely blocked Ca(2+)-stimulated and autonomous substrate phosphorylation by CaMKII and autophosphorylation at T305. However, T286 autophosphorylation (the autophosphorylation generating autonomous activity) was only mildly affected. Two mechanisms can explain this unusual differential inhibitor effect. First, CNs inhibited activity by interacting with the CaMKII T-site (and thereby also interfered with NMDA-type glutamate receptor binding to the T-site). Because of this, the CaMKII region surrounding T286 competed with CNs for T-site interaction, whereas other substrates did not. Second, the intersubunit T286 autophosphorylation requires CaM binding both to the "kinase" and the "substrate" subunit. CNs dramatically decreased CaM dissociation, thus facilitating the ability of CaM to make T286 accessible for phosphorylation. Tat-fusion made CN21 cell penetrating, as demonstrated by a strong inhibition of filopodia motility in neurons and insulin secrection from isolated Langerhans' islets. These results reveal the inhibitory mechanism of CaM-KIIN and establish a powerful new tool for dissecting CaMKII function.
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Affiliation(s)
- Rebekah S Vest
- Department of Pharmacology, University of Colorado Denver-School of Medicine, Aurora, CO 80045, USA
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24
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Abstract
Protein kinase Cs (PKCs) are implicated in many forms of synaptic plasticity. However, the specific isoform(s) of PKC that underlie(s) these events are often not known. We have used Aplysia as a model system in order to investigate the isoform specificity of PKC actions due to the presence of fewer isoforms and a large number of documented physiological roles for PKC in synaptic plasticity in this system. In particular, we have shown that distinct isoforms mediate distinct types of synaptic plasticity induced by the same neurotransmitter: The novel calcium-independent PKC Apl II is required for actions mediated by serotonin (5-HT) alone, while the classical calcium-dependent PKC Apl I is required for actions mediated when 5-HT is coupled to activity. We will discuss the reasons for PKC isoform specificity, assess the tools used to uncover isoform specificity, and discuss the implications of isoform specificity for understanding the roles of PKC in regulating synaptic plasticity.
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Affiliation(s)
- Wayne S Sossin
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada.
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25
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McNamara RK, Ostrander M, Abplanalp W, Richtand NM, Benoit SC, Clegg DJ. Modulation of phosphoinositide-protein kinase C signal transduction by omega-3 fatty acids: implications for the pathophysiology and treatment of recurrent neuropsychiatric illness. Prostaglandins Leukot Essent Fatty Acids 2006; 75:237-57. [PMID: 16935483 DOI: 10.1016/j.plefa.2006.07.009] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The phosphoinositide (PI)-protein kinase C (PKC) signal transduction pathway is initiated by pre- and postsynaptic Galphaq-coupled receptors, and regulates several clinically relevant neurochemical events, including neurotransmitter release efficacy, monoamine receptor function and trafficking, monoamine transporter function and trafficking, axonal myelination, and gene expression. Mounting evidence for PI-PKC signaling hyperactivity in the peripheral (platelets) and central (premortem and postmortem brain) tissues of patients with schizophrenia, bipolar disorder, and major depressive disorder, coupled with evidence that PI-PKC signal transduction is down-regulated in rat brain following chronic, but not acute, treatment with antipsychotic, mood-stabilizer, and antidepressant medications, suggest that PI-PKC hyperactivity is central to an underlying pathophysiology. Evidence that membrane omega-3 fatty acids act as endogenous antagonists of the PI-PKC signal transduction pathway, coupled with evidence that omega-3 fatty acid deficiency is observed in peripheral and central tissues of patients with schizophrenia, bipolar disorder, and major depressive disorder, support the hypothesis that omega-3 fatty acid deficiency may contribute to elevated PI-PKC activity in these illnesses. The data reviewed in this paper outline a potential molecular mechanism by which omega-3 fatty acids could contribute to the pathophysiology and treatment of recurrent neuropsychiatric illness.
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Affiliation(s)
- Robert K McNamara
- Department of Psychiatry, University of Cincinnati College of Medicine, Cincinnati, OH 45267-0559, USA.
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26
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Boehm J, Kang MG, Johnson RC, Esteban J, Huganir RL, Malinow R. Synaptic Incorporation of AMPA Receptors during LTP Is Controlled by a PKC Phosphorylation Site on GluR1. Neuron 2006; 51:213-25. [PMID: 16846856 DOI: 10.1016/j.neuron.2006.06.013] [Citation(s) in RCA: 284] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2005] [Revised: 05/08/2006] [Accepted: 06/16/2006] [Indexed: 11/17/2022]
Abstract
Incorporation of GluR1-containing AMPA receptors into synapses is essential to several forms of neural plasticity, including long-term potentiation (LTP). Numerous signaling pathways that trigger this process have been identified, but the direct modifications of GluR1 that control its incorporation into synapses are unclear. Here, we show that phosphorylation of GluR1 by PKC at a highly conserved serine 818 residue is increased during LTP and critical for LTP expression. GluR1 is phosphorylated by PKC at this site in vitro and in vivo. In addition, acute phosphorylation at GluR1 S818 by PKC, as well as a phosphomimetic mutation, promotes GluR1 synaptic incorporation. Conversely, preventing GluR1 S818 phosphorylation reduces LTP and blocks PKC-driven synaptic incorporation of GluR1. We conclude that the phosphorylation of GluR1 S818 by PKC is a critical event in the plasticity-driven synaptic incorporation of AMPA receptors.
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Affiliation(s)
- Jannic Boehm
- Cold Spring Harbor Laboratory, 1 Bungtown Road, Cold Spring Harbor, New York 11724, USA
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27
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Hussain RJ, Stumpo DJ, Blackshear PJ, Lenox RH, Abel T, McNamara RK. Myristoylated alanine rich C kinase substrate (MARCKS) heterozygous mutant mice exhibit deficits in hippocampal mossy fiber-CA3 long-term potentiation. Hippocampus 2006; 16:495-503. [PMID: 16572394 PMCID: PMC2914311 DOI: 10.1002/hipo.20177] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The myristoylated alanine-rich C kinase substrate (MARCKS) is a primary protein kinase C (PKC) substrate in brain thought to transduce PKC signaling into alterations in the filamentous (F) actin cytoskeleton. Within the adult hippocampus, MARCKS is highly expressed in the dentate gyrus (DG)-CA3 mossy fiber pathway, but is expressed at low levels in the CA3-CA1 Schaffer collateral-CA1 pathway. We have previously demonstrated that 50% reductions in MARCKS expression in heterozygous Marcks mutant mice produce robust deficits in spatial reversal learning, but not contextual fear conditioning, suggesting that only specific aspects of hippocampal function are impaired by reduction in MARCKS expression. To further elucidate the role of MARCKS in hippocampal synaptic plasticity, in the present study we examined basal synaptic transmission, paired-pulse facilitation, post-tetanic potentiation, and long-term potentiation (LTP) in the hippocampal mossy fiber-CA3 and Schaffer collateral-CA1 pathways of heterozygous Marcks mutant and wild-type mice. We found that LTP is significantly impaired in the mossy fiber-CA3 pathway, but not in the Schaffer collateral-CA1 pathway, in heterozygous Marcks mutant mice, whereas basal synaptic transmission, paired-pulse facilitation, and post-tetanic potentiation are unaffected in both pathways. These findings indicate that a 50% reduction in MARCKS expression impairs processes required for long-term, but not short-term, synaptic plasticity in the mossy fiber-CA3 pathway. The implications of these findings for the role of the mossy fiber-CA3 pathway in hippocampus-dependent learning processes are discussed.
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Affiliation(s)
- Rifat J. Hussain
- Department of Psychiatry, University of Pennsylvania School of Medicine, Clinical Research Building, Philadelphia, Pennsylvania
| | - Deborah J. Stumpo
- National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina
| | - Perry J. Blackshear
- National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina
| | - Robert H. Lenox
- Department of Psychiatry, University of Pennsylvania School of Medicine, Clinical Research Building, Philadelphia, Pennsylvania
| | - Ted Abel
- Department of Biology, 319 Leidy Labs, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Robert K. McNamara
- Department of Psychiatry, University of Cincinnati College of Medicine, Medical Science Building, Cincinnati, Ohio
- Correspondence to: Robert K. McNamara, Ph.D., Department of Psychiatry, University of Cincinnati College of Medicine, 231 Albert Sabin Way, Cincinnati, OH 45267-0559.
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28
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Aussedat B, Sagan S, Chassaing G, Bolbach G, Burlina F. Quantification of the efficiency of cargo delivery by peptidic and pseudo-peptidic Trojan carriers using MALDI-TOF mass spectrometry. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2006; 1758:375-83. [PMID: 16494839 DOI: 10.1016/j.bbamem.2006.01.012] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/06/2005] [Revised: 01/11/2006] [Accepted: 01/13/2006] [Indexed: 11/20/2022]
Abstract
We have measured the efficiencies of two novel pseudo-peptidic carriers and various cell-penetrating peptides (Penetratin, (Arg)9 and the third helix of the homeodomain of Knotted-1) to deliver the same cargo inside cells. The cargo that was studied corresponds to the pseudo-substrate of protein kinase C. Cargo delivery was quantified using a recent method based on isotope labeling and MALDI-TOF MS. Results of cargo delivery were compared to the amounts of free CPP internalized inside cells. The third helix of Knotted gave the best results concerning free CPP cellular uptake. It was also found to be the most efficient carrier. This peptide thus emerges as a new CPP with very promising properties.
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Affiliation(s)
- Baptiste Aussedat
- Université Pierre et Marie Curie-Paris6, boite 45, 4 place Jussieu, 75252 Paris cedex 05, France
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29
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Shalin SC, Egli R, Birnbaum SG, Roth TL, Levenson JM, Sweatt JD. Signal transduction mechanisms in memory disorders. PROGRESS IN BRAIN RESEARCH 2006; 157:25-41. [PMID: 17167902 DOI: 10.1016/s0079-6123(06)57003-7] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
This chapter explores some of the molecular events contributing to memory formation and how, when these events malfunction, disturbances in memory occur. After a brief discussion of signaling in the hippocampus, we will explore the topics of human mental retardation syndromes that involve disruption of these processes, including Angelman syndrome (AS), Neurofibromatosis 1 (NF1)-associated learning disorders, Coffin-Lowry syndrome (CLS), Rubinstein-Taybi syndrome (RTS), and Rett syndrome (RTT).
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Affiliation(s)
- Sara C Shalin
- Department of Neuroscience, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA
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30
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Hussain RJ, Carpenter DO. A comparison of the roles of protein kinase C in long-term potentiation in rat hippocampal areas CA1 and CA3. Cell Mol Neurobiol 2005; 25:649-61. [PMID: 16075383 DOI: 10.1007/s10571-005-4045-8] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2003] [Accepted: 12/10/2003] [Indexed: 10/25/2022]
Abstract
1. Using agonists and antagonists with specificity toward various isozymes, we have examined the role of protein kinase C (PKC) in long-term potentiation (LTP) in rat hippocampal areas CA1 and CA3. 2. Agonists (indolactum V but not phorbol ester) and antagonists (sphingosine, staurosporine, chelerytherene) acting at all PKC isozymes reduce or block LTP induction at both sites. 3. However ingenol, a relatively specific agonist at the delta and epsilon isozymes, blocks LTP in the MF-CA3 pathway, but not in the SC-CA1 pathway. 4. Go6976, a relatively specific antagonist of the alpha and beta isozymes, blocks LTP in the SC-CA1 pathway at both ages tested (30- and 60-day-old animals), but blocks LTP in the MF-CA3 in 60 but not 30-day-old animals. 5. Our studies indicate that different PKC isozymes are crucial to LTP induction in these two areas of hippocampus, and that there are development changes in the profile of isozymes.
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Affiliation(s)
- Rifat J Hussain
- Department of Environmental Health & Toxicology, School of Public Health, University at Albany, One University Place A217, Rensselaer, New York 12144-3456, USA
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31
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Bogoyevitch MA, Barr RK, Ketterman AJ. Peptide inhibitors of protein kinases-discovery, characterisation and use. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2005; 1754:79-99. [PMID: 16182621 DOI: 10.1016/j.bbapap.2005.07.025] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/19/2005] [Revised: 07/26/2005] [Accepted: 07/28/2005] [Indexed: 12/20/2022]
Abstract
Protein kinases are now the second largest group of drug targets, and most protein kinase inhibitors in clinical development are directed towards the ATP-binding site. However, these inhibitors must compete with high intracellular ATP concentrations and they must discriminate between the ATP-binding sites of all protein kinases as well the other proteins that also utilise ATP. It would therefore be beneficial to target sites on protein kinases other than the ATP-binding site. This review describes the discovery, characterisation and use of peptide inhibitors of protein kinases. In many cases, the development of these peptides has resulted from an understanding of the specific protein-binding partners for a particular protein kinase. In addition, novel peptide sequences have been discovered in library screening approaches and have provided new leads in the discovery and/or design of peptide inhibitors of protein kinases. These approaches are therefore providing exciting new opportunities in the development of ATP non-competitive inhibitors of protein kinases.
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Affiliation(s)
- Marie A Bogoyevitch
- Cell Signalling Laboratory, Biochemistry and Molecular Biology (M310), School of Biomedical, Biomolecular and Chemical Sciences, University of Western Australia, 35 Stirling Highway, Crawley, Western Australia 6009, Australia.
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32
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Lengyel I, Voss K, Cammarota M, Bradshaw K, Brent V, Murphy KPSJ, Giese KP, Rostas JAP, Bliss TVP. Autonomous activity of CaMKII is only transiently increased following the induction of long-term potentiation in the rat hippocampus. Eur J Neurosci 2005; 20:3063-72. [PMID: 15579161 DOI: 10.1111/j.1460-9568.2004.03748.x] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A major role has been postulated for a maintained increase in the autonomous activity of CaMKII in the expression of long-term potentiation (LTP). However, attempts to inhibit the expression of LTP with CaMKII inhibitors have yielded inconsistent results. Here we compare the changes in CaMKII autonomous activity and phosphorylation at Thr286 of alphaCaMKII in rat hippocampal slices using chemical or tetanic stimulation to produce either LTP or short-term potentiation (STP). Tetanus-induced LTP in area CA1 requires CaMKII activation and Thr286 phosphorylation of alphaCaMKII, but we did not observe an increase in autonomous activity. Next we induced LTP by 10 min exposure to 25 mM tetraethyl-ammonium (TEA) or 5 min exposure to 41 mM potassium (K) after pretreatment with calyculin A. Exposure to K alone produced STP. These protocols allowed us to monitor temporal changes in autonomous activity during and after exposure to the potentiating chemical stimulus. In chemically induced LTP, autonomous activity was maximally increased within 30 s whereas this increase was significantly delayed in STP. However, in both LTP and STP the two-fold increase in autonomous activity measured immediately after stimulation was short-lived, returning to baseline within 2-5 min after re-exposure to normal ACSF. In LTP, but not in STP, the phosphorylation of alphaCaMKII at Thr286 persisted for at least 60 min after stimulation. These results confirm that LTP is associated with a maintained increase in autophosphorylation at Thr286 but indicate that a persistent increase in the autonomous activity of CaMKII is not required for the expression of LTP.
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Affiliation(s)
- I Lengyel
- Department of Biochemistry, Biological Research Centre, Szeged, Hungary, H-6726
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Miller S, Yasuda M, Coats JK, Jones Y, Martone ME, Mayford M. Disruption of dendritic translation of CaMKIIalpha impairs stabilization of synaptic plasticity and memory consolidation. Neuron 2002; 36:507-19. [PMID: 12408852 DOI: 10.1016/s0896-6273(02)00978-9] [Citation(s) in RCA: 389] [Impact Index Per Article: 17.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Local protein translation in dendrites could be a means for delivering synaptic proteins to their sites of action, perhaps in a spatially regulated fashion that could contribute to plasticity. To directly test the functional role of dendritic translation of calcium/calmodulin-dependent protein kinase IIalpha (CaMKIIalpha) in vivo, we mutated the endogenous gene to disrupt the dendritic localization signal in the mRNA. In this mutant mouse, the protein-coding region of CaMKIIalpha is intact, but mRNA is restricted to the soma. Removal of dendritic mRNA produced a dramatic reduction of CaMKIIalpha in postsynaptic densities (PSDs), a reduction in late-phase long-term potentiation (LTP), and impairments in spatial memory, associative fear conditioning, and object recognition memory. These results demonstrate that local translation is important for synaptic delivery of the kinase and that local translation contributes to synaptic and behavioral plasticity.
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Affiliation(s)
- Stephan Miller
- Department of Cell Biology and Institute for Childhood and Neglected Diseases, The Scripps Research Institute, 10550 North Torrey Pines Road, ICND 202, La Jolla, CA 92037, USA.
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34
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Abstract
Calcium (Ca) is the key regulator of cardiac contraction during excitation-contraction (E-C) coupling. However, differences exist between the amount of Ca being transported into the myocytes upon electrical stimulation as compared to Ca released from the sarcoplasmic reticulum (SR). Moreover, alterations in E-C coupling occur in cardiac hypertrophy and heart failure. In addition to the direct effects of Ca on the myofilaments, Ca plays a pivotal role in activation of a number of Ca-dependent proteins or second messengers, which can modulate E-C coupling. Of these proteins, calmodulin (CaM) and Ca-CaM-dependent kinase II (CaMKII) are of special interest in the heart because of their role of modulating Ca influx, SR Ca release, and SR Ca uptake during E-C coupling. Indeed, CaM and CaMKII may be associated with some ion channels and Ca transporters and both can modulate acute cellular Ca handling. In addition to the changes in Ca, CaM and CaMKII signals from beat-to-beat, changes may occur on a longer time scale. These may occur over seconds to minutes involving phosphorylation/dephosphorylation reactions, and even a longer time frame in altering gene transcription (excitation-transcription (E-T) coupling) in hypertrophic signaling and heart failure. Here we review the classical role of Ca in E-C coupling and extend this view to the role of the Ca-dependent proteins CaM and CaMKII in modulating E-C coupling and their contribution to E-T coupling.
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Affiliation(s)
- Lars S Maier
- Department of Physiology, Stritch School of Medicine, Loyola University-Chicago, 2160 South First Avenue, Chicago, IL 60153, USA
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35
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Hudmon A, Schulman H. Structure-function of the multifunctional Ca2+/calmodulin-dependent protein kinase II. Biochem J 2002; 364:593-611. [PMID: 11931644 PMCID: PMC1222606 DOI: 10.1042/bj20020228] [Citation(s) in RCA: 441] [Impact Index Per Article: 20.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2002] [Revised: 03/20/2002] [Accepted: 04/04/2002] [Indexed: 11/17/2022]
Abstract
Ca2+/calmodulin (CaM)-dependent protein kinase (CaMKII) is a ubiquitous mediator of Ca2+-linked signalling that phosphorylates a wide range of substrates to co-ordinate and regulate Ca2+-mediated alterations in cellular function. The transmission of information by the kinase from extracellular stimuli and the intracellular Ca2+ rise is not passive. Rather, its multimeric structure and autoregulation enable this enzyme to participate actively in the sensitivity, timing and location of its action. CaMKII can: (i) be activated in a Ca2+-spike frequency-dependent manner; (ii) become independent of its initial Ca2+/CaM activators; and (iii) undergo a 'molecular switch-like' behaviour, which is crucial for certain forms of learning and memory. CaMKII is derived from a family of four homologous but distinct genes, with over 30 alternatively spliced isoforms described at present. These isoforms possess diverse developmental and anatomical expression patterns, as well as subcellular localization. Six independent catalytic/autoregulatory domains are connected by a narrow stalk-like appendage to each hexameric ring within the dodecameric structure. Ca2+/CaM binding activates the enzyme by disinhibiting the autoregulatory domain; this process initiates an intra-holoenzyme autophosphorylation reaction that induces complex changes in the enzyme's sensitivity to Ca2+/CaM, including the generation of Ca2+/CaM-independent (autonomous) activity and marked increase in affinity for CaM. The role of CaMKII in Ca2+ signal transduction is shaped by its autoregulation, isoenzymic type and subcellular localization. The molecular determinants and mechanisms producing these processes are discussed as they relate to the structure-function of this multifunctional protein kinase.
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Affiliation(s)
- Andy Hudmon
- Department of Neurobiology, Fairchild Bldg, D217 299 Campus Drive, Stanford University Medical School, Stanford, CA 94305-5125, USA.
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36
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Priming of long-term potentiation in mouse hippocampus by corticotropin-releasing factor and acute stress: implications for hippocampus-dependent learning. J Neurosci 2002. [PMID: 11978854 DOI: 10.1523/jneurosci.22-09-03788.2002] [Citation(s) in RCA: 161] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
In the present experiments, we characterized the action of human/rat corticotropin-releasing factor (h/rCRF) and acute stress (1 hr of immobilization) on hippocampus-dependent learning and on synaptic plasticity in the mouse hippocampus. We first showed that h/rCRF application and acute stress facilitated (primed) long-term potentiation of population spikes (PS-LTP) in the mouse hippocampus and enhanced context-dependent fear conditioning. Both the priming of PS-LTP and the improvement of context-dependent fear conditioning were prevented by the CRF receptor antagonist [Glu(11,16)]astressin. PS-LTP priming and improved learning were also reduced by the protein kinase C inhibitor bisindolylmaleimide I. Acute stress induced the activation of Ca2+/calmodulin-dependent kinase II (CaMKII) 2 hr after the end of the stress session. The CaMKII inhibitor KN-62 antagonized the stress-mediated learning enhancement, however, with no effect on PS-LTP persistence. Thus, long-lasting increased neuronal excitability as reflected in PS-LTP priming appeared to be essential for the enhancement of learning in view of the observation that inhibition of PS-LTP priming was associated with impaired learning. Conversely, it was demonstrated that inhibition of CaMKII activity reduced contextual fear conditioning without affecting PS-LTP priming. This observation suggests that priming of PS-LTP and activation of CaMKII represent two essential mechanisms that may contribute independently to long-term memory.
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37
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Zhang J, Li N, Yu J, Zhang W, Cao X. Molecular cloning and characterization of a novel calcium/calmodulin-dependent protein kinase II inhibitor from human dendritic cells. Biochem Biophys Res Commun 2001; 285:229-34. [PMID: 11444830 DOI: 10.1006/bbrc.2001.5175] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Calcium/calmodulin-dependent protein kinase II (CaMKII) is a widely distributed protein kinase that regulates numerous physiological functions. Inhibitors of CaMKII are useful tools for investigating the CaMKII functions. Here we identified a novel CaMKII inhibitor protein (CaM-KIIN) from the human dendritic cell cDNA library by large-scale random sequencing. Human CaM-KIIN contains 79 amino acids, which shares 98% identity and 98% positives with rat CaMKII inhibitor protein beta and 65% identity and 78% positives with rat CaMKII inhibitor alpha. Human CaM-KIIN mRNA expression was detectable in various tissues and cell lines by Northern blot and RT-PCR. To investigate its biological functions, full-length human CaM-KIIN was overexpressed in colon adenocarcinoma LoVo cells. When expressed in LoVo cells, it could inhibit cell proliferation, block cell growth, and decrease the viable cell number. These results characterize a potential cellular inhibitor protein of CaMKII that plays an important role in the regulation of cell growth.
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Affiliation(s)
- J Zhang
- Department of Clinical Laboratory, Changzheng Hospital, Shanghai 200003, People's Republic of China
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38
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Chang BH, Mukherji S, Soderling TR. Calcium/calmodulin-dependent protein kinase II inhibitor protein: localization of isoforms in rat brain. Neuroscience 2001; 102:767-77. [PMID: 11182241 DOI: 10.1016/s0306-4522(00)00520-0] [Citation(s) in RCA: 81] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
A second isoform of Ca2+/calmodulin-dependent-kinase II inhibitor protein (CaM-KIIN) has been identified using the yeast two-hybrid screen. The 1.8kb message encodes a 78 residue CaM-KIINalpha that is 65% identical in its putative open-reading frame and 95% identical in its inhibitory domain to the previously characterized CaM-KIINbeta. CaM-KIINalpha exhibits inhibitory properties towards recombinant mouse CaM-kinase IIalpha indistinguishable from CaM-KIINbeta. The 27 amino acid inhibitory peptide (CaM-KIINtide) derived from CaM-KIIN has the ability to inhibit brain CaM-kinase II activity from multiple organisms including rat, Drosophila and goldfish. Northern analysis of various rat tissues indicates that CaM-KIINalpha is specific to brain whereas CaM-KIINbeta message is also present in testis. In situ hybridization shows a general distribution of both isoforms in rat brain with stronger localization of CaM-KIINbeta in cerebellum and hindbrain and CaM-KIINalpha in frontal cortex, hippocampus and inferior colliculus. An antibody that recognizes both isoforms shows a distribution of CaM-KIIN in rat brain that correlates with immunoreactivity of CaM-kinase II. In cultured mature hippocampal neurons, CaM-KIIN is present in cell bodies and dendrites but, unlike CaM-kinase II, does not display punctate staining at synapses. These results suggest a localized function for CaM-KIIN in inhibiting specialized pools of CaM-kinase II.
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Affiliation(s)
- B H Chang
- Vollum Institute, Oregon Health Sciences University, 3181 SW Sam Jackson Park Road, Portland, OR 97201, USA
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39
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Mirnikjoo B, Brown SE, Kim HF, Marangell LB, Sweatt JD, Weeber EJ. Protein kinase inhibition by omega-3 fatty acids. J Biol Chem 2001; 276:10888-96. [PMID: 11152679 DOI: 10.1074/jbc.m008150200] [Citation(s) in RCA: 107] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Recent data suggest that omega-3 fatty acids may be effective in epilepsy, cardiovascular disorders, arthritis, and as mood stabilizers for bipolar disorder; however, the mechanism of action of these compounds is unknown. Based on earlier studies implicating omega-3 fatty acids as inhibitors of protein kinase C activity in intact cells, we hypothesized that omega-3 fatty acids may act through direct inhibition of second messenger-regulated kinases and sought to determine whether the omega-3 double bond might uniquely confer pharmacologic efficacy and potency for fatty acids of this type. In our studies we observed that omega-3 fatty acids inhibited the in vitro activities of cAMP-dependent protein kinase, protein kinase C, Ca(2+)/calmodulin-dependent protein kinase II, and the mitogen-activated protein kinase (MAPK). Our results with a series of long-chain fatty acid structural homologs suggest an important role for the omega-3 double bond in conferring inhibitory efficacy. To assess whether omega-3 fatty acids were capable of inhibiting protein kinases in living neurons, we evaluated their effect on signal transduction pathways in the hippocampus. We found that omega-3 fatty acids could prevent serotonin receptor-induced MAPK activation in hippocampal slice preparations. In addition, we evaluated the effect of omega-3 fatty acids on hippocampal long-term potentiation, a form of synaptic plasticity known to be dependent on protein kinase activation. We observed that omega-3 fatty acids blocked long-term potentiation induction without inhibiting basal synaptic transmission. Overall, our results from both in vitro and live cell preparations suggest that inhibition of second messenger-regulated protein kinases is one locus of action of omega-3 fatty acids.
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Affiliation(s)
- B Mirnikjoo
- Division of Neuroscience, Department of Psychiatry and Behavioral Sciences, Baylor College of Medicine, Houston, Texas 77030, USA
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40
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Chen HX, Otmakhov N, Strack S, Colbran RJ, Lisman JE. Is persistent activity of calcium/calmodulin-dependent kinase required for the maintenance of LTP? J Neurophysiol 2001; 85:1368-76. [PMID: 11287461 DOI: 10.1152/jn.2001.85.4.1368] [Citation(s) in RCA: 101] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Calcium/calmodulin-dependent protein kinase II (CaMKII) is concentrated in the postsynaptic density (PSD) and plays an important role in the induction of long-term potentiation (LTP). Because this kinase is persistently activated after the induction, its activity could also be important for LTP maintenance. Experimental tests of this hypothesis, however, have given conflicting results. In this paper we further explore the role of postsynaptic CaMKII in induction and maintenance of LTP. Postsynaptic application of a CaMKII inhibitor [autocamtide-3 derived peptide inhibitor (AC3-I), 2 mM] blocked LTP induction but had no detectable affect on N-methyl-D-aspartate (NMDA)-mediated synaptic transmission, indicating that the primary function of CaMKII in LTP is downstream from NMDA channel function. We next explored various methodological factors that could account for conflicting results on the effect of CaMKII inhibitors on LTP maintenance. In contrast to our previous work, we now carried out experiments at higher temperature (33 degrees C), used slices from adult animals, and induced LTP using a tetanic stimulation. However, we still found that LTP maintenance was not affected by postsynaptic application of AC3-I. Furthermore the inhibitor did not block LTP maintenance under conditions designed to enhance the Ca(2+)-dependent activity of protein phosphatases 1 and 2B (elevated Ca(2+), calmodulin, and an inhibitor of protein kinase A). We also tested the possibility that CaMKII inhibitor might not be able to affect CaMKII once it was inserted into the PSD. In whole-brain extracts, AC3-I blocked autophosphorylation of both soluble and particulate/PSD CaMKII with similar potencies although the potency of the inhibitor toward other CaMKII substrates varied. Thus we were unable to demonstrate a functional role of persistent Ca(2+)-independent CaMKII activity in LTP maintenance. Possible explanations of the data are discussed.
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Affiliation(s)
- H X Chen
- Volen Center for Complex Systems, Brandeis University, Waltham, Massachusetts 02454, USA
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41
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Long-term potentiation induced by theta frequency stimulation is regulated by a protein phosphatase-1-operated gate. J Neurosci 2001. [PMID: 11050107 DOI: 10.1523/jneurosci.20-21-07880.2000] [Citation(s) in RCA: 67] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Long-term potentiation (LTP) can be induced in the Schaffer collateral-->CA1 synapse of hippocampus by stimulation in the theta frequency range (5-12 Hz), an effect that depends on activation of the cAMP pathway. We investigated the mechanisms of the cAMP contribution to this form of LTP in the rat hippocampal slice preparation. theta pulse stimulation (TPS; 150 stimuli at 10 Hz) by itself did not induce LTP, but the addition of either the beta-adrenergic agonist isoproterenol or the cAMP analog 8-bromo-cAMP (8-Br-cAMP) enabled TPS-induced LTP. The isoproterenol effect was blocked by postsynaptic inhibition of cAMP-dependent protein kinase. Several lines of evidence indicated that cAMP enabled LTP by blocking postsynaptic protein phosphatase-1 (PP1). Activators of the cAMP pathway reduced PP1 activity in the CA1 region and increased the active form of inhibitor-1, an endogenous inhibitor of PP1. Postsynaptic injection of activated inhibitor-1 mimicked the LTP-enabling effect of cAMP pathway stimulation. TPS evoked complex spiking when isoproterenol was present. However, complex spiking was not sufficient to enable TPS-induced LTP, which additionally required the inhibition of postsynaptic PP1. PP1 inhibition seems to promote the activation of Ca(2+)/calmodulin-dependent protein kinase (CaMKII), because (1) a CaMKII inhibitor blocked the induction of LTP by TPS paired with either isoproterenol or activated inhibitor-1 and (2) CaMKII in area CA1 was activated by the combination of TPS and 8-Br-cAMP but not by either stimulus alone. These results indicate that the cAMP pathway enables TPS-induced LTP by inhibiting PP1, thereby enhancing Ca(2+)-independent CaMKII activity.
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42
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Lengyel I, Cammarota M, Brent VA, Rostas JA. Autonomous activity and autophosphorylation of CAMPK-II in rat hippocampal slices: effects of tissue preparation. J Neurochem 2001; 76:149-54. [PMID: 11145987 DOI: 10.1046/j.1471-4159.2001.00058.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Measurement of the proportion of calcium/calmodulin-stimulated protein kinase II (CaMPK-II) that is autonomously active or phosphorylated on Thr(286) is thought to provide an index of the degree to which CaMPK-II in a tissue has been activated. We have examined how various ways of handling hippocampal tissue can alter these properties. Both autonomous activity and phospho-Thr(286) content was high in freshly dissected hippocampus or freshly cut hippocampal slices. After incubation of hippocampal slices in artificial cerebrospinal fluid for 120 min, both properties of CaMPK-II decreased to a steady state level. Freeze-thaw or cutting the equilibrated slices could rapidly increase both autonomous activity and phospho-Thr(286) immunoreactivity of CaMPK-II. These increases were comparable to changes induced by experimental treatment. Therefore, our results suggest that considerable care needs to be taken over the way in which hippocampal slices are handled.
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Affiliation(s)
- I Lengyel
- The Neuroscience Group, Faculty of Medicine and Health Sciences, University of Newcastle, Callaghan, NSW, Australia
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43
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Daw MI, Chittajallu R, Bortolotto ZA, Dev KK, Duprat F, Henley JM, Collingridge GL, Isaac JT. PDZ proteins interacting with C-terminal GluR2/3 are involved in a PKC-dependent regulation of AMPA receptors at hippocampal synapses. Neuron 2000; 28:873-86. [PMID: 11163273 DOI: 10.1016/s0896-6273(00)00160-4] [Citation(s) in RCA: 274] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
We investigated the role of PDZ proteins (GRIP, ABP, and PICK1) interacting with the C-terminal GluR2 by infusing a ct-GluR2 peptide ("pep2-SVKI") into CA1 pyramidal neurons in hippocampal slices using whole-cell recordings. Pep2-SVKI, but not a control or PICK1 selective peptide, caused AMPAR-mediated EPSC amplitude to increase in approximately one-third of control neurons and in most neurons following the prior induction of LTD. Pep2-SVKI also blocked LTD; however, this occurred in all neurons. A PKC inhibitor prevented these effects of pep2-SVKI on synaptic transmission and LTD. We propose a model in which the maintenance of LTD involves the binding of AMPARs to PDZ proteins to prevent their reinsertion. We also present evidence that PKC regulates AMPAR reinsertion during dedepression.
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Affiliation(s)
- M I Daw
- MRC Centre for Synaptic Plasticity, Department of Anatomy, University of Bristol, University Walk, BS8 1TD, Bristol, United Kingdom
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44
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Brown GP, Blitzer RD, Connor JH, Wong T, Shenolikar S, Iyengar R, Landau EM. Long-term potentiation induced by theta frequency stimulation is regulated by a protein phosphatase-1-operated gate. J Neurosci 2000; 20:7880-7. [PMID: 11050107 PMCID: PMC6772713] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/18/2023] Open
Abstract
Long-term potentiation (LTP) can be induced in the Schaffer collateral-->CA1 synapse of hippocampus by stimulation in the theta frequency range (5-12 Hz), an effect that depends on activation of the cAMP pathway. We investigated the mechanisms of the cAMP contribution to this form of LTP in the rat hippocampal slice preparation. theta pulse stimulation (TPS; 150 stimuli at 10 Hz) by itself did not induce LTP, but the addition of either the beta-adrenergic agonist isoproterenol or the cAMP analog 8-bromo-cAMP (8-Br-cAMP) enabled TPS-induced LTP. The isoproterenol effect was blocked by postsynaptic inhibition of cAMP-dependent protein kinase. Several lines of evidence indicated that cAMP enabled LTP by blocking postsynaptic protein phosphatase-1 (PP1). Activators of the cAMP pathway reduced PP1 activity in the CA1 region and increased the active form of inhibitor-1, an endogenous inhibitor of PP1. Postsynaptic injection of activated inhibitor-1 mimicked the LTP-enabling effect of cAMP pathway stimulation. TPS evoked complex spiking when isoproterenol was present. However, complex spiking was not sufficient to enable TPS-induced LTP, which additionally required the inhibition of postsynaptic PP1. PP1 inhibition seems to promote the activation of Ca(2+)/calmodulin-dependent protein kinase (CaMKII), because (1) a CaMKII inhibitor blocked the induction of LTP by TPS paired with either isoproterenol or activated inhibitor-1 and (2) CaMKII in area CA1 was activated by the combination of TPS and 8-Br-cAMP but not by either stimulus alone. These results indicate that the cAMP pathway enables TPS-induced LTP by inhibiting PP1, thereby enhancing Ca(2+)-independent CaMKII activity.
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Affiliation(s)
- G P Brown
- Departments of Pharmacology and Psychiatry, Mount Sinai School of Medicine, New York, New York 10029, USA
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45
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Bortolotto ZA, Collingridge GL. A role for protein kinase C in a form of metaplasticity that regulates the induction of long-term potentiation at CA1 synapses of the adult rat hippocampus. Eur J Neurosci 2000; 12:4055-62. [PMID: 11069602 DOI: 10.1046/j.1460-9568.2000.00291.x] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The possibility that protein kinase C (PKC) is involved in the induction of N-methyl-D-aspartate (NMDA) receptor-dependent long-term potentiation (LTP) at CA1 synapses in the hippocampus has been the subject of considerable investigation. However, many of the conclusions have been drawn from the use of relatively nonspecific PKC inhibitors. In the present study we have examined the role of PKC in tetanus-induced LTP of AMPA receptor-mediated synaptic transmission in hippocampal slices obtained from adult rats. In particular, we have investigated the possible role of PKC in a molecular switch process that is triggered by the synaptic activation of metabotropic glutamate receptors and regulates the induction of LTP. We find that the three PKC inhibitors examined, chelerythrine, Ro-31-8220 and Gö 6983, all block the setting of the molecular switch at concentrations consistent with inhibition of PKC. In contrast, these inhibitors are without affect on the induction of LTP, even when applied in very much higher concentrations. A PKA inhibitor, Rp-cAMPS, had no effect on either process. We suggest that neither PKC nor PKA is required to induce LTP at this synapse. However, PKC is involved in the regulation of LTP induction, via the molecular switch process.
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Affiliation(s)
- Z A Bortolotto
- MRC Centre for Synaptic Plasticity, Department of Anatomy, School of Medical Sciences, University of Bristol, Bristol, BS8 1TD, UK
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46
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Abstract
The protein kinase C family of enzymes has been implicated in synaptic plasticity and memory in a wide range of animal species, but to date little information has been available concerning specific roles for individual isoforms of this category of kinases. To investigate the role of the beta isoform of PKC in mammalian learning, we characterized mice deficient in the PKC beta gene using anatomical, biochemical, physiological, and behavioral approaches. In our studies we observed that PKC beta was predominantly expressed in the neocortex, in area CA1 of the hippocampus, and in the basolateral nucleus of the amygdala. Mice deficient in PKC beta showed normal brain anatomy and normal hippocampal synaptic transmission, paired pulse facilitation, and long-term potentiation and normal sensory and motor responses. The PKC beta knock-out animals exhibited a loss of learning, however; they suffered deficits in both cued and contextual fear conditioning. The PKC expression pattern and behavioral phenotype in the PKC beta knock-out animals indicate a critical role for the beta isoform of PKC in learning-related signal transduction mechanisms, potentially in the basolateral nucleus of the amygdala.
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47
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Weeber EJ, Atkins CM, Selcher JC, Varga AW, Mirnikjoo B, Paylor R, Leitges M, Sweatt JD. A role for the beta isoform of protein kinase C in fear conditioning. J Neurosci 2000; 20:5906-14. [PMID: 10934237 PMCID: PMC6772611] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/17/2023] Open
Abstract
The protein kinase C family of enzymes has been implicated in synaptic plasticity and memory in a wide range of animal species, but to date little information has been available concerning specific roles for individual isoforms of this category of kinases. To investigate the role of the beta isoform of PKC in mammalian learning, we characterized mice deficient in the PKC beta gene using anatomical, biochemical, physiological, and behavioral approaches. In our studies we observed that PKC beta was predominantly expressed in the neocortex, in area CA1 of the hippocampus, and in the basolateral nucleus of the amygdala. Mice deficient in PKC beta showed normal brain anatomy and normal hippocampal synaptic transmission, paired pulse facilitation, and long-term potentiation and normal sensory and motor responses. The PKC beta knock-out animals exhibited a loss of learning, however; they suffered deficits in both cued and contextual fear conditioning. The PKC expression pattern and behavioral phenotype in the PKC beta knock-out animals indicate a critical role for the beta isoform of PKC in learning-related signal transduction mechanisms, potentially in the basolateral nucleus of the amygdala.
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Affiliation(s)
- E J Weeber
- Division of Neuroscience, Baylor College of Medicine, Houston, Texas 77030, USA
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48
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Walaas SI, Sefland I. Modulation of calcium-evoked [3H]noradrenaline release from permeabilized cerebrocortical synaptosomes by the MARCKS protein, calmodulin and the actin cytoskeleton. Neurochem Int 2000; 36:581-93. [PMID: 10771116 DOI: 10.1016/s0197-0186(99)00159-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
In order to examine intracellular modulation of CNS catecholamine release, cerebrocortical synaptosomes were prelabeled with [3H]noradrenaline and permeabilized with streptolysin-O in the absence or presence of Ca(2+). Plasma membrane permeabilization allowed efflux of cytosol and left a compartmentalized pool of [3H]noradrenaline intact, approximately 10% of which was released by addition of 10(-5) M Ca(2+). Addition of activators or inhibitors of protein kinase C, as well as inhibitors of Ca(2+)-calmodulin kinase II or calcineurin, failed to change Ca(2+)-induced noradrenaline release. Evoked release from permeabilized synaptosomes deficient in the vesicle-associated phosphoprotein synapsin I was also unchanged. In contrast, addition of a synthetic 'active domain' peptide from the myristoylated, alanine-rich C-kinase substrate (MARCKS) protein increased, while addition of calmodulin decreased Ca(2+)-induced release from the permeabilized synaptosomes, the latter effect being reversed by a peptide inhibitor of calcineurin. Moreover, addition of the actin-destabilizing agent DNase I, as well as antibodies to MARCKS, appeared to increase spontaneous, Ca(2+)-independent release from noradrenergic vesicles. These results indicate that the MARCKS protein may modulate release from permeabilized noradrenergic synaptosomes, possibly by modulating calmodulin levels and/or the actin cytoskeleton.
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Affiliation(s)
- S I Walaas
- Neurochemical Laboratory, Institute of Basic Medical Sciences, University of Oslo, P.O. Box 1115-Blindern, N-0317, Oslo, Norway.
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49
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Affiliation(s)
- J D Sweatt
- Division of Neuroscience, Baylor College of Medicine, Houston, Texas 77030, USA
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50
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Pereda AE, Bell TD, Chang BH, Czernik AJ, Nairn AC, Soderling TR, Faber DS. Ca2+/calmodulin-dependent kinase II mediates simultaneous enhancement of gap-junctional conductance and glutamatergic transmission. Proc Natl Acad Sci U S A 1998; 95:13272-7. [PMID: 9789078 PMCID: PMC23780 DOI: 10.1073/pnas.95.22.13272] [Citation(s) in RCA: 132] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
While chemical synapses are very plastic and modifiable by defined activity patterns, gap junctions, which mediate electrical transmission, have been classically perceived as passive intercellular channels. Excitatory transmission between auditory afferents and the goldfish Mauthner cell is mediated by coexisting gap junctions and glutamatergic synapses. Although an increased intracellular Ca2+ concentration is expected to reduce gap junctional conductance, both components of the synaptic response were instead enhanced by postsynaptic increases in Ca2+ concentration, produced by patterned synaptic activity or intradendritic Ca2+ injections. The synaptically induced potentiations were blocked by intradendritic injection of KN-93, a Ca2+/calmodulin-dependent kinase (CaM-K) inhibitor, or CaM-KIINtide, a potent and specific peptide inhibitor of CaM-KII, whereas the responses were potentiated by injection of an activated form of CaM-KII. The striking similarities of the mechanisms reported here with those proposed for long-term potentiation of mammalian glutamatergic synapses suggest that gap junctions are also similarly regulated and indicate a primary role for CaM-KII in shaping and regulating interneuronal communication, regardless of its modality.
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Affiliation(s)
- A E Pereda
- Allegheny University of the Health Sciences, Philadelphia, PA 19129, USA.
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