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Bolton SC, Thompson DH, Kinzer-Ursem TL. Methods optimization for the expression and purification of human calcium calmodulin-dependent protein kinase II alpha. PLoS One 2024; 19:e0285651. [PMID: 38180986 PMCID: PMC10769071 DOI: 10.1371/journal.pone.0285651] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2023] [Accepted: 07/18/2023] [Indexed: 01/07/2024] Open
Abstract
Calcium/calmodulin-dependent protein kinase II (CaMKII) is a complex multifunctional kinase that is highly expressed in central nervous tissues and plays a key regulatory role in the calcium signaling pathway. Despite over 30 years of recombinant expression and characterization studies, CaMKII continues to be investigated for its impact on signaling cooperativity and its ability to bind multiple substrates through its multimeric hub domain. Here we compare and optimize protocols for the generation of full-length wild-type human calcium/calmodulin-dependent protein kinase II alpha (CaMKIIα). Side-by-side comparison of expression and purification in both insect and bacterial systems shows that the insect expression method provides superior yields of the desired autoinhibited CaMKIIα holoenzymes. Utilizing baculovirus insect expression system tools, our results demonstrate a high yield method to produce homogenous, monodisperse CaMKII in its autoinhibited state suitable for biophysical analysis. Advantages and disadvantages of these two expression systems (baculovirus insect cell versus Escherichia coli expression) are discussed, as well as purification optimizations to maximize the enrichment of full-length CaMKII.
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Affiliation(s)
- Scott C. Bolton
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, Indiana, United States of America
- Department of Chemistry, Purdue University, West Lafayette, Indiana, United States of America
| | - David H. Thompson
- Department of Chemistry, Purdue University, West Lafayette, Indiana, United States of America
| | - Tamara L. Kinzer-Ursem
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, Indiana, United States of America
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2
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Nicoll RA, Schulman H. Synaptic memory and CaMKII. Physiol Rev 2023; 103:2877-2925. [PMID: 37290118 PMCID: PMC10642921 DOI: 10.1152/physrev.00034.2022] [Citation(s) in RCA: 22] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2022] [Revised: 04/26/2023] [Accepted: 04/30/2023] [Indexed: 06/10/2023] Open
Abstract
Ca2+/calmodulin-dependent protein kinase II (CaMKII) and long-term potentiation (LTP) were discovered within a decade of each other and have been inextricably intertwined ever since. However, like many marriages, it has had its up and downs. Based on the unique biochemical properties of CaMKII, it was proposed as a memory molecule before any physiological linkage was made to LTP. However, as reviewed here, the convincing linkage of CaMKII to synaptic physiology and behavior took many decades. New technologies were critical in this journey, including in vitro brain slices, mouse genetics, single-cell molecular genetics, pharmacological reagents, protein structure, and two-photon microscopy, as were new investigators attracted by the exciting challenge. This review tracks this journey and assesses the state of this marriage 40 years on. The collective literature impels us to propose a relatively simple model for synaptic memory involving the following steps that drive the process: 1) Ca2+ entry through N-methyl-d-aspartate (NMDA) receptors activates CaMKII. 2) CaMKII undergoes autophosphorylation resulting in constitutive, Ca2+-independent activity and exposure of a binding site for the NMDA receptor subunit GluN2B. 3) Active CaMKII translocates to the postsynaptic density (PSD) and binds to the cytoplasmic C-tail of GluN2B. 4) The CaMKII-GluN2B complex initiates a structural rearrangement of the PSD that may involve liquid-liquid phase separation. 5) This rearrangement involves the PSD-95 scaffolding protein, α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPARs), and their transmembrane AMPAR-regulatory protein (TARP) auxiliary subunits, resulting in an accumulation of AMPARs in the PSD that underlies synaptic potentiation. 6) The stability of the modified PSD is maintained by the stability of the CaMKII-GluN2B complex. 7) By a process of subunit exchange or interholoenzyme phosphorylation CaMKII maintains synaptic potentiation in the face of CaMKII protein turnover. There are many other important proteins that participate in enlargement of the synaptic spine or modulation of the steps that drive and maintain the potentiation. In this review we critically discuss the data underlying each of the steps. As will become clear, some of these steps are more firmly grounded than others, and we provide suggestions as to how the evidence supporting these steps can be strengthened or, based on the new data, be replaced. Although the journey has been a long one, the prospect of having a detailed cellular and molecular understanding of learning and memory is at hand.
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Affiliation(s)
- Roger A Nicoll
- Department of Cellular and Molecular Pharmacology, University of California at San Francisco, San Francisco, California, United States
| | - Howard Schulman
- Department of Neurobiology, Stanford University School of Medicine, Stanford, California, United States
- Panorama Research Institute, Sunnyvale, California, United States
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3
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Lučić I, Héluin L, Jiang PL, Castro Scalise AG, Wang C, Franz A, Heyd F, Wahl MC, Liu F, Plested AJR. CaMKII autophosphorylation can occur between holoenzymes without subunit exchange. eLife 2023; 12:e86090. [PMID: 37566455 PMCID: PMC10468207 DOI: 10.7554/elife.86090] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2023] [Accepted: 08/10/2023] [Indexed: 08/12/2023] Open
Abstract
The dodecameric protein kinase CaMKII is expressed throughout the body. The alpha isoform is responsible for synaptic plasticity and participates in memory through its phosphorylation of synaptic proteins. Its elaborate subunit organization and propensity for autophosphorylation allow it to preserve neuronal plasticity across space and time. The prevailing hypothesis for the spread of CaMKII activity, involving shuffling of subunits between activated and naive holoenzymes, is broadly termed subunit exchange. In contrast to the expectations of previous work, we found little evidence for subunit exchange upon activation, and no effect of restraining subunits to their parent holoenzymes. Rather, mass photometry, crosslinking mass spectrometry, single molecule TIRF microscopy and biochemical assays identify inter-holoenzyme phosphorylation (IHP) as the mechanism for spreading phosphorylation. The transient, activity-dependent formation of groups of holoenzymes is well suited to the speed of neuronal activity. Our results place fundamental limits on the activation mechanism of this kinase.
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Affiliation(s)
- Iva Lučić
- Institute of Biology, Cellular Biophysics, Humboldt Universität zu BerlinBerlinGermany
- Leibniz-Forschungsinstitut für Molekulare PharmakologieBerlinGermany
| | - Léonie Héluin
- Institute of Biology, Cellular Biophysics, Humboldt Universität zu BerlinBerlinGermany
- Leibniz-Forschungsinstitut für Molekulare PharmakologieBerlinGermany
| | - Pin-Lian Jiang
- Leibniz-Forschungsinstitut für Molekulare PharmakologieBerlinGermany
| | - Alejandro G Castro Scalise
- Institute of Biology, Cellular Biophysics, Humboldt Universität zu BerlinBerlinGermany
- Leibniz-Forschungsinstitut für Molekulare PharmakologieBerlinGermany
| | - Cong Wang
- Leibniz-Forschungsinstitut für Molekulare PharmakologieBerlinGermany
| | - Andreas Franz
- Institute of Chemistry and Biochemistry, Freie Universität BerlinBerlinGermany
| | - Florian Heyd
- Institute of Chemistry and Biochemistry, Freie Universität BerlinBerlinGermany
| | - Markus C Wahl
- Institute of Chemistry and Biochemistry, Freie Universität BerlinBerlinGermany
- Helmholtz-Zentrum Berlin für Materialien und Energie, Macromolecular CrystallographyBerlinGermany
| | - Fan Liu
- Leibniz-Forschungsinstitut für Molekulare PharmakologieBerlinGermany
- Charité-Universitätsmedizin BerlinBerlinGermany
| | - Andrew JR Plested
- Institute of Biology, Cellular Biophysics, Humboldt Universität zu BerlinBerlinGermany
- Leibniz-Forschungsinstitut für Molekulare PharmakologieBerlinGermany
- NeuroCure, Charité UniversitätsmedizinBerlinGermany
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4
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Griem-Krey N, Clarkson AN, Wellendorph P. CaMKIIα as a Promising Drug Target for Ischemic Grey Matter. Brain Sci 2022; 12:1639. [PMID: 36552099 PMCID: PMC9775128 DOI: 10.3390/brainsci12121639] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2022] [Revised: 11/26/2022] [Accepted: 11/28/2022] [Indexed: 12/02/2022] Open
Abstract
Ca2+/calmodulin-dependent protein kinase II (CaMKII) is a major mediator of Ca2+-dependent signaling pathways in various cell types throughout the body. Its neuronal isoform CaMKIIα (alpha) centrally integrates physiological but also pathological glutamate signals directly downstream of glutamate receptors and has thus emerged as a target for ischemic stroke. Previous studies provided evidence for the involvement of CaMKII activity in ischemic cell death by showing that CaMKII inhibition affords substantial neuroprotection. However, broad inhibition of this central kinase is challenging because various essential physiological processes like synaptic plasticity rely on intact CaMKII regulation. Thus, specific strategies for targeting CaMKII after ischemia are warranted which would ideally only interfere with pathological activity of CaMKII. This review highlights recent advances in the understanding of how ischemia affects CaMKII and how pathospecific pharmacological targeting of CaMKII signaling could be achieved. Specifically, we discuss direct targeting of CaMKII kinase activity with peptide inhibitors versus indirect targeting of the association (hub) domain of CaMKIIα with analogues of γ-hydroxybutyrate (GHB) as a potential way to achieve more specific pharmacological modulation of CaMKII activity after ischemia.
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Affiliation(s)
- Nane Griem-Krey
- Department of Drug Design and Pharmacology, University of Copenhagen, 2100 Copenhagen, Denmark
| | - Andrew N. Clarkson
- Department of Anatomy, Brain Health Research Centre and Brain Research New Zealand, University of Otago, Dunedin 9016, New Zealand
| | - Petrine Wellendorph
- Department of Drug Design and Pharmacology, University of Copenhagen, 2100 Copenhagen, Denmark
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5
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Buonarati OR, Miller AP, Coultrap SJ, Bayer KU, Reichow SL. Conserved and divergent features of neuronal CaMKII holoenzyme structure, function, and high-order assembly. Cell Rep 2021; 37:110168. [PMID: 34965414 PMCID: PMC8985225 DOI: 10.1016/j.celrep.2021.110168] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2021] [Revised: 08/30/2021] [Accepted: 12/03/2021] [Indexed: 11/23/2022] Open
Abstract
Neuronal CaMKII holoenzymes (α and β isoforms) enable molecular signal computation underlying learning and memory but also mediate excitotoxic neuronal death. Here, we provide a comparative analysis of these signaling devices, using single-particle electron microscopy (EM) in combination with biochemical and live-cell imaging studies. In the basal state, both isoforms assemble mainly as 12-mers (but also 14-mers and even 16-mers for the β isoform). CaMKIIα and β isoforms adopt an ensemble of extended activatable states (with average radius of 12.6 versus 16.8 nm, respectively), characterized by multiple transient intra- and inter-holoenzyme interactions associated with distinct functional properties. The extended state of CaMKIIβ allows direct resolution of intra-holoenzyme kinase domain dimers. These dimers could enable cooperative activation by calmodulin, which is observed for both isoforms. High-order CaMKII clustering mediated by inter-holoenzyme kinase domain dimerization is reduced for the β isoform for both basal and excitotoxicity-induced clusters, both in vitro and in neurons. The CaMKII holoenzyme enables neuronal signal computation. In a comparative structure-function analysis of the neuronal α and β isoforms, Buonarati et al. find evidence for kinase domain dimers within the holoenzyme that enable a cooperative activation mechanism in both isoforms and inter-holoenzyme interactions that enable high-order aggregate formation under ischemic conditions.
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Affiliation(s)
- Olivia R Buonarati
- Department of Pharmacology, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA
| | - Adam P Miller
- Department of Chemistry, Portland State University, Portland, OR 97201, USA
| | - Steven J Coultrap
- Department of Pharmacology, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA
| | - K Ulrich Bayer
- Department of Pharmacology, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA.
| | - Steve L Reichow
- Department of Chemistry, Portland State University, Portland, OR 97201, USA.
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6
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Tian Z, Song Y, Yao Y, Guo J, Gong Z, Wang Z. Genetic Etiology Shared by Multiple Sclerosis and Ischemic Stroke. Front Genet 2020; 11:646. [PMID: 32719717 PMCID: PMC7348066 DOI: 10.3389/fgene.2020.00646] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2019] [Accepted: 05/27/2020] [Indexed: 12/23/2022] Open
Abstract
Although dramatic progress has been achieved in the understanding and treatment of multiple sclerosis (MS) and ischemic stroke (IS), more precise and instructive support is required for further research. Recent large-scale genome-wide association studies (GWASs) have already revealed risk variants for IS and MS, but the common genetic etiology between MS and IS remains an unresolved issue. This research was designed to overlapping genes between MS and IS and unmask their transcriptional features. We designed a three-section analysis process. Firstly, we computed gene-based analyses of MS GWAS and IS GWAS data sets by VGEAS2. Secondly, overlapping genes of significance were identified in a meta-analysis using the Fisher’s procedure. Finally, we performed gene expression analyses to confirm transcriptional changes. We identified 24 shared genes with Bonferroni correction (Pcombined < 2.31E-04), and five (FOXP1, CAMK2G, CLEC2D, LBH, and SLC2A4RG) had significant expression differences in MS and IS gene expression omnibus data sets. These meaningful shared genes between IS and MS shed light on the underlying genetic etiologies shared by the diseases. Our results provide a basis for in-depth genomic studies of associations between MS and IS.
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Affiliation(s)
- Zhu Tian
- Department of Neurology, Tianjin First Central Hospital, Tianjin, China
| | - Yang Song
- Department of Neurology, Tianjin First Central Hospital, Tianjin, China
| | - Yang Yao
- Department of Neurology, Tianjin First Central Hospital, Tianjin, China
| | - Jie Guo
- Department of Neurology, Tianjin First Central Hospital, Tianjin, China
| | - Zhongying Gong
- Department of Neurology, Tianjin First Central Hospital, Tianjin, China
| | - Zhiyun Wang
- Department of Neurology, Tianjin First Central Hospital, Tianjin, China
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7
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Alishahi M, Ghaedrahmati F, Kolagar TA, Winlow W, Nikkar N, Farzaneh M, Khoshnam SE. Long non-coding RNAs and cell death following ischemic stroke. Metab Brain Dis 2019; 34:1243-1251. [PMID: 31055786 DOI: 10.1007/s11011-019-00423-2] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/23/2019] [Accepted: 04/21/2019] [Indexed: 01/02/2023]
Abstract
Stroke is a major cause of morbidity and mortality worldwide, and extensive efforts have focused on the improvement of therapeutic strategies to reduce cell death following ischemic stroke. Uncovering the cellular and molecular pathophysiological processes in ischemic stroke have been a top priority. Long noncoding RNAs (lncRNAs) are endogenous molecules that play key roles in the pathophysiology of cerebral ischemia, and involved in the neuronal cell death during ischemic stroke. In recent years, a bulk of aberrantly expressed lncRNAs have been screened out in ischemic stroke insulted animals. LncRNAs along with their targets could affect the genetic machinery at molecular levels, and exploring their functions and mechanisms may be a promising option for ischemic stroke treatment. In this review, we summarize the current knowledge for lncRNAs in ischemic stroke, focusing on the role of specific lncRNAs that may underlie cell death to find possible therapeutic targets.
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Affiliation(s)
- Masoumeh Alishahi
- Department of Biology, Tehran North Branch, Islamic Azad University, Tehran, Iran
| | - Farhoodeh Ghaedrahmati
- Department of Immunology, Medical School, Shiraz University of Medical Sciences, Shiraz, Iran
| | | | - William Winlow
- Dipartimento di Biologia, Università degli Studi di Napoli, Federico II, Via Cintia 26, 80126, Naples, Italy
- Honorary Research Fellow, Institute of Ageing and Chronic Diseases, University of Liverpool, The APEX building, 6 West Derby Street, Liverpool, L7 8TX, UK
| | - Negin Nikkar
- Department of Biology, Faculty of Sciences, Alzahra University, Tehran, Iran
| | - Maryam Farzaneh
- Department of Stem Cells and Developmental Biology, Cell Science Research Center, Royan Institute for Stem Cell Biology and Technology, ACECR, Tehran, Iran
| | - Seyed Esmaeil Khoshnam
- Physiology Research Center, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran.
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8
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Ye J, Das S, Roy A, Wei W, Huang H, Lorenz-Guertin JM, Xu Q, Jacob TC, Wang B, Sun D, Wang QJ. Ischemic Injury-Induced CaMKIIδ and CaMKIIγ Confer Neuroprotection Through the NF-κB Signaling Pathway. Mol Neurobiol 2018; 56:2123-2136. [PMID: 29992531 PMCID: PMC6394630 DOI: 10.1007/s12035-018-1198-2] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2018] [Accepted: 06/26/2018] [Indexed: 12/13/2022]
Abstract
Ca2+/calmodulin-dependent protein kinase II (CaMKII) has long been implicated in neuronal injury caused by acute ischemia/reperfusion (I/R). However, its precise role and regulatory mechanisms remain obscure. Here, we investigated the role of the CaMKII family in neuronal survival during I/R. Our data indicated that CAMK2D/CaMKIIδ and CAMK2G/CaMKIIγ were selectively upregulated in a time-dependent manner at both transcriptional and protein levels after acute ischemia. Overexpression of CaMKIIδ promoted neuronal survival, while their depletion exacerbated ischemic neuronal death. Similar to CaMKIIδ, knockdown of CAMKIIγ resulted in significant neuronal death after I/R. We further identified CaMKIIδ2 as the subtype that is selectively induced by I/R in primary neurons. The induction of CaMKIIδ was controlled in part by a pair of long non-coding RNAs (lncRNAs), C2dat1 and C2dat2. C2dat2, similar to C2dat1, was upregulated by I/R and cooperated with C2dat1 to modulate CaMKIIδ expression. Knockdown of C2dat1/2 blocked OGD/R-induced CaMKIIδ expression and decreased neuronal survival but did not affect the levels of CaMKIIγ, indicating specific targeting of CAMK2D by C2dat1/2. Mechanistically, I/R-induced CaMKIIδ and CaMKIIγ caused the upregulation of IKKα/β and further activation of the NF-κB signaling pathway to protect neurons from ischemic damage. Genetically, downregulating p65 subunit of NF-κB in mice increased I/R-induced neuronal death by blocking the activity of CaMKII/IKK/IκBα/NF-κB signaling axis. In summary, CaMKIIδ and CaMKIIγ are novel I/R-induced genes that promote neuronal survival during ischemic injury. The upregulation of these CaMKII kinases led to activation of the NF-κB signaling pathway, which protects neurons from ischemic damage.
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Affiliation(s)
- Jing Ye
- Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, E1354 BST, Pittsburgh, PA, 15261, USA.,Department of Anesthesiology, Nanfang Hospital, Southern Medical University, Guangzhou, People's Republic of China
| | - Sabyasachi Das
- Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, E1354 BST, Pittsburgh, PA, 15261, USA
| | - Adhiraj Roy
- Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, E1354 BST, Pittsburgh, PA, 15261, USA
| | - Wenzhong Wei
- Department of Orthopaedic Surgery, University of Pittsburgh, Pittsburgh, PA, USA
| | - Huachen Huang
- Department of Neurology, University of Pittsburgh, Pittsburgh, PA, USA.,Department of Neurology, The First affiliate Hospital, Harbin Medical University, Harbin, Heilongjiang, China
| | - Joshua Michael Lorenz-Guertin
- Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, E1354 BST, Pittsburgh, PA, 15261, USA
| | - Qian Xu
- China-UK-NYNU-RRes Joint Laboratory, Nanyang Normal University, Nanyang, People's Republic of China
| | - Tija C Jacob
- Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, E1354 BST, Pittsburgh, PA, 15261, USA
| | - Bing Wang
- Department of Orthopaedic Surgery, University of Pittsburgh, Pittsburgh, PA, USA
| | - Dandan Sun
- Department of Neurology, University of Pittsburgh, Pittsburgh, PA, USA
| | - Qiming Jane Wang
- Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, E1354 BST, Pittsburgh, PA, 15261, USA.
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Hoffman L, Li L, Alexov E, Sanabria H, Waxham MN. Cytoskeletal-like Filaments of Ca 2+-Calmodulin-Dependent Protein Kinase II Are Formed in a Regulated and Zn 2+-Dependent Manner. Biochemistry 2017; 56:2149-2160. [PMID: 28318265 DOI: 10.1021/acs.biochem.7b00028] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Ca2+-calmodulin-dependent protein kinase II (CaMKII) is highly abundant in neurons, where its concentration reaches that typically found for cytoskeletal proteins. Functional reasons for such a high concentration are not known, but given the multitude of known binding partners for CaMKII, a role as a scaffolding molecule has been proposed. In this report, we provide experimental evidence that demonstrates a novel structural role for CaMKII. We discovered that CaMKII forms filaments that can extend for several micrometers in the presence of certain divalent cations (Zn2+, Cd2+, and Cu2+) but not with others (Ca2+, Mg2+, Co2+, and Ni2+). Once formed, depleting the divalent ion concentration with chelators completely dissociated the filaments, and this process could be repeated by cyclic addition and removal of divalent ions. Using the crystal structure of the CaMKII holoenzyme, we computed an electrostatic potential map of the dodecameric complex to predict divalent ion binding sites. This analysis revealed a potential surface-exposed divalent ion binding site involving amino acids that also participate in calmodulin (CaM) binding and suggested CaM binding might inhibit formation of the filaments. As predicted, Ca2+/CaM binding both inhibited divalent ion-induced filament formation and could disassemble preformed filaments. Interestingly, CaMKII within the filaments retains the capacity to autophosphorylate; however, activity toward exogenous substrates is significantly decreased. Activity is restored upon filament disassembly. We compile our results with structural and mechanistic data from the literature to propose a model of Zn2+-mediated CaMKII filament formation, in which assembly and activity are further regulated by Ca2+/CaM.
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Affiliation(s)
- Laurel Hoffman
- Department of Neurobiology and Anatomy, McGovern Medical School, The University of Texas Health Science Center at Houston , 6431 Fannin, Room 7.254, MSB, Houston, Texas 77030, United States
| | - Lin Li
- Department of Physics and Astronomy, Clemson University , Clemson, South Carolina 29634-0978, United States
| | - Emil Alexov
- Department of Physics and Astronomy, Clemson University , Clemson, South Carolina 29634-0978, United States
| | - Hugo Sanabria
- Department of Physics and Astronomy, Clemson University , Clemson, South Carolina 29634-0978, United States
| | - M Neal Waxham
- Department of Neurobiology and Anatomy, McGovern Medical School, The University of Texas Health Science Center at Houston , 6431 Fannin, Room 7.254, MSB, Houston, Texas 77030, United States
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10
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Rostas JA, Hoffman A, Murtha LA, Pepperall D, McLeod DD, Dickson PW, Spratt NJ, Skelding KA. Ischaemia- and excitotoxicity-induced CaMKII-Mediated neuronal cell death: The relative roles of CaMKII autophosphorylation at T286 and T253. Neurochem Int 2017; 104:6-10. [DOI: 10.1016/j.neuint.2017.01.002] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2016] [Revised: 12/22/2016] [Accepted: 01/04/2017] [Indexed: 11/29/2022]
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11
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The role of Ca 2+-calmodulin stimulated protein kinase II in ischaemic stroke - A potential target for neuroprotective therapies. Neurochem Int 2017; 107:33-42. [PMID: 28153786 DOI: 10.1016/j.neuint.2017.01.012] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2016] [Revised: 01/17/2017] [Accepted: 01/24/2017] [Indexed: 01/26/2023]
Abstract
Studies in multiple experimental systems show that Ca2+-calmodulin stimulated protein kinase II (CaMKII) is a major mediator of ischaemia-induced cell death and suggest that CaMKII would be a good target for neuroprotective therapies in acute treatment of stroke. However, as CaMKII regulates many cellular processes in many tissues any clinical treatment involving the inhibition of CaMKII would need to be able to specifically target the functions of ischaemia-activated CaMKII. In this review we summarise new developments in our understanding of the molecular mechanisms involved in ischaemia-induced CaMKII-mediated cell death that have identified ways in which such specificity of CaMKII inhibition after stroke could be achieved. We also review the mechanisms and phases of tissue damage in ischaemic stroke to identify where and when CaMKII-mediated mechanisms may be involved.
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12
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Otmakhov N, Gorbacheva EV, Regmi S, Yasuda R, Hudmon A, Lisman J. Excitotoxic insult results in a long-lasting activation of CaMKIIα and mitochondrial damage in living hippocampal neurons. PLoS One 2015; 10:e0120881. [PMID: 25793533 PMCID: PMC4368532 DOI: 10.1371/journal.pone.0120881] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2014] [Accepted: 02/11/2015] [Indexed: 12/11/2022] Open
Abstract
Over-activation of excitatory NMDA receptors and the resulting Ca2+ overload is the main cause of neuronal toxicity during stroke. CaMKII becomes misregulated during such events. Biochemical studies show either a dramatic loss of CaMKII activity or its persistent autonomous activation after stroke, with both of these processes being implicated in cell toxicity. To complement the biochemical data, we monitored CaMKII activation in living hippocampal neurons in slice cultures using high spatial/temporal resolution two-photon imaging of the CaMKIIα FRET sensor, Camui. CaMKII activation state was estimated by measuring Camui fluorescence lifetime. Short NMDA insult resulted in Camui activation followed by a redistribution of its protein localization: an increase in spines, a decrease in dendritic shafts, and concentration into numerous clusters in the cell soma. Camui activation was either persistent (> 1-3 hours) or transient (~20 min) and, in general, correlated with its protein redistribution. After longer NMDA insult, however, Camui redistribution persisted longer than its activation, suggesting distinct regulation/phases of these processes. Mutational and pharmacological analysis suggested that persistent Camui activation was due to prolonged Ca2+ elevation, with little impact of autonomous states produced by T286 autophosphorylation and/or by C280/M281 oxidation. Cell injury was monitored using expressible mitochondrial marker mito-dsRed. Shortly after Camui activation and clustering, NMDA treatment resulted in mitochondrial swelling, with persistence of the swelling temporarily linked to the persistence of Camui activation. The results suggest that in living neurons excitotoxic insult produces long-lasting Ca2+-dependent active state of CaMKII temporarily linked to cell injury. CaMKII function, however, is to be restricted due to strong clustering. The study provides the first characterization of CaMKII activation dynamics in living neurons during excitotoxic insults.
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Affiliation(s)
- Nikolai Otmakhov
- Biology Department, Brandeis University, Waltham, Massachusetts, 02454, United States of America
- * E-mail:
| | - Elena V. Gorbacheva
- Biology Department, Brandeis University, Waltham, Massachusetts, 02454, United States of America
| | - Shaurav Regmi
- Biology Department, Brandeis University, Waltham, Massachusetts, 02454, United States of America
| | - Ryohei Yasuda
- Max Planck Florida Institute, One Max Planck Way, Jupiter, Florida, 33458, United States of America
| | - Andy Hudmon
- STARK Neuroscience Research Institute, Indiana University School of Medicine, 950 West Walnut Street, Research Building II, Room 480, Indianapolis, Indiana, 46202, United States of America
| | - John Lisman
- Biology Department, Brandeis University, Waltham, Massachusetts, 02454, United States of America
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Belzil C, Ramos T, Sanada K, Colicos MA, Nguyen MD. p600 stabilizes microtubules to prevent the aggregation of CaMKIIα during photoconductive stimulation. Cell Mol Biol Lett 2014; 19:381-92. [PMID: 25034033 PMCID: PMC6275876 DOI: 10.2478/s11658-014-0201-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2014] [Accepted: 07/07/2014] [Indexed: 11/21/2022] Open
Abstract
The large microtubule-associated/Ca(2+)-signalling protein p600 (also known as UBR4) is required for hippocampal neuronal survival upon Ca(2+) dyshomeostasis induced by glutamate treatment. During this process, p600 prevents aggregation of the Ca(2+)/calmodulin-dependent kinase IIα (CaMKIIα), a proxy of neuronal death, via direct binding to calmodulin in a microtubuleindependent manner. Using photoconductive stimulation coupled with live imaging of single neurons, we identified a distinct mechanism of prevention of CaMKIIα aggregation by p600. Upon direct depolarization, CaMKIIα translocates to microtubules. In the absence of p600, this translocation is interrupted in favour of a sustained self-aggregation that is prevented by the microtubule-stabilizing drug paclitaxel. Thus, during photoconductive stimulation, p600 prevents the aggregation of CaMKIIα by stabilizing microtubules. The effectiveness of this stabilization for preventing CaMKIIα aggregation during direct depolarization but not during glutamate treatment suggests a model wherein p600 has two modes of action depending on the source of cytosolic Ca(2+).
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Affiliation(s)
- Camille Belzil
- Hotchkiss Brain Institute, University of Calgary, Departments of Clinical Neurosciences, Cell Biology & Anatomy, Biochemistry & Molecular Biology, 3330 Hospital Drive NW, Calgary, Alberta Canada T2N 4N1
| | - Tim Ramos
- Hotchkiss Brain Institute, University of Calgary, Departments of Clinical Neurosciences, Cell Biology & Anatomy, Biochemistry & Molecular Biology, 3330 Hospital Drive NW, Calgary, Alberta Canada T2N 4N1
| | - Kamon Sanada
- Molecular Genetics Research Laboratory, Graduate School of Science, University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo, 113-0033 Japan
| | - Michael A. Colicos
- Hotchkiss Brain Institute, University of Calgary, Departments of Clinical Neurosciences, Cell Biology & Anatomy, Biochemistry & Molecular Biology, 3330 Hospital Drive NW, Calgary, Alberta Canada T2N 4N1
| | - Minh Dang Nguyen
- Hotchkiss Brain Institute, University of Calgary, Departments of Clinical Neurosciences, Cell Biology & Anatomy, Biochemistry & Molecular Biology, 3330 Hospital Drive NW, Calgary, Alberta Canada T2N 4N1
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14
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Quantitative estimates of the cytoplasmic, PSD, and NMDAR-bound pools of CaMKII in dendritic spines. Brain Res 2011; 1419:46-52. [PMID: 21925648 DOI: 10.1016/j.brainres.2011.08.051] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2011] [Revised: 08/17/2011] [Accepted: 08/19/2011] [Indexed: 02/02/2023]
Abstract
CaMKII plays a critical role in long-term potentiation (LTP). The kinase is a major component of the postsynaptic density (PSD); however, it is also contained in the spine cytoplasm. CaMKII can now be monitored optically in living neurons, and it is therefore important to understand the contribution of the PSD and cytoplasmic pools to optical signals. Here, we estimate the size of these pools under basal conditions. From EM immunolabeling data, we calculate that the PSD/cytoplasmic ratio is ~5%. A second independent estimate is derived from measurements indicating that the average mushroom spine PSD contains 90 to 240 holoenzymes. A cytoplasmic concentration of 16 μM (~2590 holoenzymes) in the spine can be estimated from the total measured CaMKII content of hippocampal tissue, the relative volume of different compartments, and the spine-dendrite ratio of CaMKII (2:1). These numbers yield a second estimate (6%) of the PSD/spine ratio in good agreement with the first. The CaMKII bound to the NMDAR is important because preventing the formation of this complex blocks LTP induction. We estimate that the percentage of spine CaMKII held active by binding to the NMDAR is ~0.2%. Implications of the high spine concentration of CaMKII (> 100 μM alpha subunits) and the small fraction within the PSD are discussed. Of particular note, the finding that the CaMKII signal in spines shows only transient activation (open state) after LTP induction is subject to the qualification that it does not reflect the small but important pool bound to the NMDAR.
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15
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O'Leary H, Liu WH, Rorabaugh JM, Coultrap SJ, Bayer KU. Nucleotides and phosphorylation bi-directionally modulate Ca2+/calmodulin-dependent protein kinase II (CaMKII) binding to the N-methyl-D-aspartate (NMDA) receptor subunit GluN2B. J Biol Chem 2011; 286:31272-81. [PMID: 21768120 DOI: 10.1074/jbc.m111.233668] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The Ca(2+)/calmodulin (CaM)-dependent protein kinase II (CaMKII) and the NMDA-type glutamate receptor are key regulators of synaptic plasticity underlying learning and memory. Direct binding of CaMKII to the NMDA receptor subunit GluN2B (formerly known as NR2B) (i) is induced by Ca(2+)/CaM but outlasts this initial Ca(2+)-stimulus, (ii) mediates CaMKII translocation to synapses, and (iii) regulates synaptic strength. CaMKII binds to GluN2B around S1303, the major CaMKII phosphorylation site on GluN2B. We show here that a phospho-mimetic S1303D mutation inhibited CaM-induced CaMKII binding to GluN2B in vitro, presenting a conundrum how binding can occur within cells, where high ATP concentration should promote S1303 phosphorylation. Surprisingly, addition of ATP actually enhanced the binding. Mutational analysis revealed that this positive net effect was caused by four modulatory effects of ATP, two positive (direct nucleotide binding and CaMKII T286 autophosphorylation) and two negative (GluN2B S1303 phosphorylation and CaMKII T305/6 autophosphorylation). Imaging showed positive regulation by nucleotide binding also within transfected HEK cells and neurons. In fact, nucleotide binding was a requirement for efficient CaMKII interaction with GluN2B in cells, while T286 autophosphorylation was not. Kinetic considerations support a model in which positive regulation by nucleotide binding and T286 autophosphorylation occurs faster than negative modulation by GluN2B S1303 and CaMKII T305/6 phosphorylation, allowing efficient CaMKII binding to GluN2B despite the inhibitory effects of the two slower reactions.
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Affiliation(s)
- Heather O'Leary
- Department of Pharmacology, School of Medicine, University of Colorado Denver, Aurora, Colorado 80045, USA
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16
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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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17
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Javid N, Vogtt K, Roy S, Hirst AR, Hoell A, Hamley IW, Ulijn RV, Sefcik J. Supramolecular Structures of Enzyme Clusters. J Phys Chem Lett 2011; 2:1395-1399. [PMID: 23795242 PMCID: PMC3688366 DOI: 10.1021/jz200446j] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2011] [Accepted: 05/18/2011] [Indexed: 05/10/2023]
Abstract
The structural characterization of subtilisin mesoscale clusters, which were previously shown to induce supramolecular order in biocatalytic self-assembly of Fmoc-dipeptides, was carried out by synchrotron small-angle X-ray, dynamic, and static light scattering measurements. Subtilisin molecules self-assemble to form supramolecular structures in phosphate buffer solutions. Structural arrangement of subtilisin clusters at 55 °C was found to vary systematically with increasing enzyme concentration. Static light scattering measurements showed the cluster structure to be consistent with a fractal-like arrangement, with fractal dimension varying from 1.8 to 2.6 with increasing concentration for low to moderate enzyme concentrations. This was followed by a structural transition around the enzyme concentration of 0.5 mg mL-1 to more compact structures with significantly slower relaxation dynamics, as evidenced by dynamic light scattering measurements. These concentration-dependent supramolecular enzyme clusters provide tunable templates for biocatalytic self-assembly.
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Affiliation(s)
- Nadeem Javid
- WestCHEM, Department of Pure & Applied Chemistry and Department of Chemical and Process Engineering, University of Strathclyde , Glasgow G1 1XJ, United Kingdom ; WestCHEM, Department of Pure & Applied Chemistry and Department of Chemical and Process Engineering, University of Strathclyde , Glasgow G1 1XJ, United Kingdom
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18
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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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19
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Vest RS, O'Leary H, Bayer KU. Differential regulation by ATP versus ADP further links CaMKII aggregation to ischemic conditions. FEBS Lett 2009; 583:3577-81. [PMID: 19840793 DOI: 10.1016/j.febslet.2009.10.028] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2009] [Revised: 09/24/2009] [Accepted: 10/13/2009] [Indexed: 10/20/2022]
Abstract
CaMKII, a major mediator of synaptic plasticity, forms extra-synaptic clusters under ischemic conditions. This study further supports self-aggregation of CaMKII holoenzymes as the underlying mechanism. Aggregation in vitro was promoted by mimicking ischemic conditions: low pH (6.8 or less), Ca(2+) (and calmodulin), and low ATP and/or high ADP concentration. Mutational analysis showed that high ATP prevented aggregation by a mechanism involving T286 auto-phosphorylation, and indicated requirement for nucleotide binding but not auto-phosphorylation also for extra-synaptic clustering within neurons. These results clarify a previously apparent paradox in the nucleotide and phosphorylation requirement of aggregation, and support a mechanism that involves inter-holoenzyme T286-region/T-site interaction.
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Affiliation(s)
- Rebekah S Vest
- Department of Pharmacology, University of Colorado Denver, Aurora, CO 80045, United States
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20
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A two-state model for Ca2+/CaM-dependent protein kinase II (αCaMKII) in response to persistent Ca2+ stimulation in hippocampal neurons. Cell Calcium 2008; 44:465-78. [DOI: 10.1016/j.ceca.2008.03.003] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2007] [Revised: 02/01/2008] [Accepted: 03/05/2008] [Indexed: 11/24/2022]
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21
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CaMKIIbeta binding to stable F-actin in vivo regulates F-actin filament stability. Proc Natl Acad Sci U S A 2008; 105:15791-6. [PMID: 18840684 DOI: 10.1073/pnas.0804399105] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Ca2(+)/calmodulin-dependent protein kinase II (CaMKII) is a serine/threonine kinase that is best known for its role in synaptic plasticity and memory. Multiple roles of CaMKII have been identified in the hippocampus, yet its role in developing neurons is less well understood. We show here that endogenous CaMKIIbeta, but not CaMKIIalpha, localized to prominent F-actin-rich structures at the soma in embryonic cortical neurons. Fluorescence recovery after photobleaching analyses of GFP-CaMKIIbeta binding interactions with F-actin in this CaMKIIalpha-free system indicated CaMKIIbeta binding depended upon a putative F-actin binding domain in the variable region of CaMKIIbeta. Furthermore, CaMKIIalpha decreased CaMKIIbeta binding to F-actin. We examined the interaction of CaMKIIbeta with stable and dynamic actin and show that CaMKIIbeta binding to F-actin was dramatically prolonged when F-actin was stabilized. CaMKIIbeta binding to stable F-actin was disrupted when it was bound by Ca2(+)/calmodulin or when it was highly phosphorylated, but not by kinase inactivity. Whereas CaMKIIbeta over-expression increased the prevalence of the F-actin-rich structures, disruption of CaMKIIbeta binding to F-actin reduced them. Taken together, these data suggest that CaMKIIbeta binding to stable F-actin is important for the in vivo maintenance of polymerized F-actin.
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22
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Shetty PK, Huang FL, Huang KP. Ischemia-elicited Oxidative Modulation of Ca2+/Calmodulin-dependent Protein Kinase II. J Biol Chem 2008; 283:5389-401. [DOI: 10.1074/jbc.m708479200] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
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23
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Munevar S, Gangopadhyay SS, Gallant C, Colombo B, Sellke FW, Morgan KG. CaMKIIT287 and T305 regulate history-dependent increases in alpha agonist-induced vascular tone. J Cell Mol Med 2007; 12:219-26. [PMID: 18088385 PMCID: PMC3823483 DOI: 10.1111/j.1582-4934.2007.00202.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
CaMKII is a calcium and calmodulin-activated kinase that has been shown to regulate learning and memory in the brain, and contractility in blood vessels. Following Ca activation, CaMKII autophosphorylates, gaining a calcium-independent autonomous activity that reflects a molecular memory of having previously come into contact with calcium. The present study addresses whether the molecular memory properties of CaMKII are involved in the modulation of sustained vascular tone. We demonstrate a history-dependence of α agonist-induced vascular tone and show that CaMKII activation in vascular cells is also history dependent. Autophosphorylation of Thr287, which is classically associated with autonomous activity, does not persist during tone maintenance after transient increases in intracellular calcium levels. However, we have found that another site, Thr305, known from in vitro studies to be inhibitory, is regulated by α agonists in that the inhibitory action is removed, thus leading to a delayed reactivation of CaMKII as measured by Thr287 phosphorylation. By the use of a small molecule CaMKII inhibitor (KN93) as well as a decoy peptide (autoinhibitory peptide; AIP) we show a cause and effect relationship between CaMKII reactivation and sustained vascular tone maintenance. Thus, it appears that a complex interplay between the regulation of Thr305 and Thr287 provides a novel mechanism by which a history-dependence is developed and contributes to a new facet of molecular memory for CaMKII of relevance to vascular tone maintenance.
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Affiliation(s)
- S Munevar
- Boston Biomedical Research Institute, Watertown, MA, USA
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24
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Suzuki T, Du F, Tian QB, Zhang J, Endo S. Ca2+/calmodulin-dependent protein kinase IIalpha clusters are associated with stable lipid rafts and their formation traps PSD-95. J Neurochem 2007; 104:596-610. [PMID: 18005004 DOI: 10.1111/j.1471-4159.2007.05035.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Relatively large number of post-synaptic density (PSD) proteins, including Ca2+/calmodulin-dependent protein kinase II (CaMKII), have the potential to associate with lipid rafts. We in this study demonstrate that the CaMKIIalpha clusters induced by ionomycin in human embryonic kidney 293 cells, as well as unclustered CaMKIIalpha (Du F., Saitoh F., Tian Q. B., Miyazawa S., Endo S. and Suzuki T, 2006, Biochem. Biophys. Res. Commun 347, 814-820), were associated with lipid rafts. The CaMKIIalpha clusters associated with lipid raft fraction became resistant to treatment with methyl-beta-cyclodextrin and subsequent cold Triton X-100, which suggests the stabilization of CaMKIIalpha cluster-associated lipid rafts. Next, we found that PSD-95, which is also a component of lipid raft fraction and does not interact directly with CaMKII, was trapped by stable CaMKIIalpha cluster-containing structure. Association of PSD-95 with CaMKIIalpha clusters was also observed in cultured neuronal cells. These results suggest the CaMKIIalpha clusters associated with the lipid rafts in the cytoplasmic region play a role in the assembly and stabilization of certain PSD proteins that have the potential to associate with lipid rafts.
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Affiliation(s)
- Tatsuo Suzuki
- Department of Neuroplasticity, Research Institute on Aging and Adaptation, Shinshu University Graduate School of Medicine, Matsumoto, Japan.
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25
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Tao-Cheng JH, Gallant PE, Brightman MW, Dosemeci A, Reese TS. Structural changes at synapses after delayed perfusion fixation in different regions of the mouse brain. J Comp Neurol 2007; 501:731-40. [PMID: 17299754 DOI: 10.1002/cne.21276] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
We recently showed by electron microscopy that the postsynaptic density (PSD) from hippocampal cultures undergoes rapid structural changes after ischemia-like conditions. Here we report that similar structural changes occur after delay in transcardial perfusion fixation of the mouse brain. Delay in perfusion fixation, a condition that mimics ischemic stress, resulted in 70%, 90%, and 23% increases in the thickness of PSDs from the hippocampus (CA1), cerebral cortex (layer III), and cerebellar cortex (Purkinje spines), respectively. In step with PSD thickening, the amount of PSD-associated alpha-calcium calmodulin-dependent protein kinase II (alpha- CaMKII) label increased more in cerebral cortical spines than in Purkinje spines. Although the Purkinje PSDs thickened only slightly after delayed fixation, they became highly curved, and many formed sub-PSD spheres approximately 80 nm in diameter that labeled for CaMKII. Delayed perfusion fixation also produced more cytoplamic CaMKII clusters ( approximately 110 nm in diameter) in the somas of pyramidal cells (from hippocampus and cerebral cortex) than in Purkinje cells. Thus a short delay in perfusion fixation produces cell-specific structural changes at PSDs and neuronal somas. Purkinje cells respond somewhat differently to delayed perfusion fixation, perhaps owing to their lower levels of CaMKII, and CaMKII binding proteins at PSDs. We present here a catalogue of structural changes that signal a perfusion fixation delay, thereby providing criteria by which to assess perfusion fixation quality in experimental structural studies of brain and to shed light on the subtle changes that occur in intact brain following metabolic stress.
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Affiliation(s)
- Jung-Hwa Tao-Cheng
- EM Facility, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892, USA
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26
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Hudmon A, Lebel E, Roy H, Sik A, Schulman H, Waxham MN, De Koninck P. A mechanism for Ca2+/calmodulin-dependent protein kinase II clustering at synaptic and nonsynaptic sites based on self-association. J Neurosci 2006; 25:6971-83. [PMID: 16049173 PMCID: PMC6724830 DOI: 10.1523/jneurosci.4698-04.2005] [Citation(s) in RCA: 130] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The activity of Ca2+/calmodulin-dependent protein kinase II (CaMKII) plays an integral role in regulating synaptic development and plasticity. We designed a live-cell-imaging approach to monitor an activity-dependent clustering of green fluorescent protein (GFP)-CaMKII holoenzymes, termed self-association, a process that we hypothesize contributes to the translocation of CaMKII to synaptic and nonsynaptic sites in activated neurons. We show that GFP-CaMKII self-association in human embryonic kidney 293 (HEK293) cells requires a catalytic domain and multimeric structure, requires Ca2+ stimulation and a functional Ca2+/CaM-binding domain, is regulated by cellular pH and Thr286 autophosphorylation, and has variable rates of dissociation depending on Ca2+ levels. Furthermore, we show that the same rules that govern CaMKII self-association in HEK293 cells apply for extrasynaptic and postsynaptic translocation of GFP-CaMKII in hippocampal neurons. Our data support a novel mechanism for targeting CaMKII to postsynaptic sites after neuronal activation. As such, CaMKII may form a scaffold that, in combination with other synaptic proteins, recruits and localizes additional proteins to the postsynaptic density. We discuss the potential function of CaMKII self-association as a tag of synaptic activity.
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Affiliation(s)
- Andy Hudmon
- Department of Neurobiology, Stanford University, Stanford, California 94305, USA
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27
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Tao-Cheng JH, Vinade L, Winters CA, Reese TS, Dosemeci A. Inhibition of phosphatase activity facilitates the formation and maintenance of NMDA-induced calcium/calmodulin-dependent protein kinase II clusters in hippocampal neurons. Neuroscience 2005; 130:651-6. [PMID: 15590149 DOI: 10.1016/j.neuroscience.2004.10.008] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/04/2004] [Indexed: 11/17/2022]
Abstract
The majority of hippocampal neurons in dissociated cultures and in intact brain exhibit clustering of calcium/calmodulin-dependent protein kinase II (CaMKII) into spherical structures with an average diameter of 110 nm when subjected to conditions that mimic ischemia and excitotoxicity [Neuroscience 106 (2001) 69]. Because clustering of CaMKII would reduce its effective concentration within the neuron, it may represent a cellular strategy to prevent excessive CaMKII-mediated phosphorylation during episodes of Ca2+ overload. Here we employ a relatively mild excitatory stimulus to promote sub-maximal clustering for the purpose of studying the conditions for the formation and disappearance of CaMKII clusters. Treatment with 30 microM N-methyl-D-aspartic acid (NMDA) for 2 min produced CaMKII clustering in approximately 15% of dissociated hippocampal neurons in culture, as observed by pre-embedding immunogold electron microscopy. These CaMKII clusters could be labeled with antibodies specific to the phospho form (Thr286) of CaMKII, suggesting that at least some of the CaMKII molecules in clusters are autophosphorylated. To test whether phosphorylation is involved in the formation and maintenance of CaMKII clusters, the phosphatase inhibitors calyculin A (5 nM) or okadaic acid (1 microM) were included in the incubation medium. With inhibitors more neurons exhibited CaMKII clusters in response to 2 min NMDA treatment. Furthermore, 5 min after the removal of NMDA and Ca2+, CaMKII clusters remained and could still be labeled with the phospho-specific antibody. In contrast, in the absence of phosphatase inhibitors, no clusters were detected 5 min after the removal of NMDA and Ca2+ from the medium. These results suggest that phosphatases type 1 and/or 2A regulate the formation and disappearance of CaMKII clusters.
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Affiliation(s)
- J-H Tao-Cheng
- NINDS Electron Microscopy Facility, NIH, Building 36, Room 2A21, Bethesda, MD 20892, USA.
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28
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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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29
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Colbran RJ. Targeting of calcium/calmodulin-dependent protein kinase II. Biochem J 2004; 378:1-16. [PMID: 14653781 PMCID: PMC1223945 DOI: 10.1042/bj20031547] [Citation(s) in RCA: 205] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2003] [Revised: 12/03/2003] [Accepted: 12/04/2003] [Indexed: 01/10/2023]
Abstract
Calcium/calmodulin-dependent protein kinase II (CaMKII) has diverse roles in virtually all cell types and it is regulated by a plethora of mechanisms. Local changes in Ca2+ concentration drive calmodulin binding and CaMKII activation. Activity is controlled further by autophosphorylation at multiple sites, which can generate an autonomously active form of the kinase (Thr286) or can block Ca2+/calmodulin binding (Thr305/306). The regulated actions of protein phosphatases at these sites also modulate downstream signalling from CaMKII. In addition, CaMKII targeting to specific subcellular microdomains appears to be necessary to account for the known signalling specificity, and targeting is regulated by Ca2+/calmodulin and autophosphorylation. The present review focuses on recent studies revealing the diversity of CaMKII interactions with proteins localized to neuronal dendrites. Interactions with various subunits of the NMDA (N-methyl-D-aspartate) subtype of glutamate receptor have attracted the most attention, but binding of CaMKII to cytoskeletal and several other regulatory proteins has also been reported. Recent reports describing the molecular basis of each interaction and their potential role in the normal regulation of synaptic transmission and in pathological situations are discussed. These studies have revealed fundamental regulatory mechanisms that are probably important for controlling CaMKII functions in many cell types.
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Affiliation(s)
- Roger J Colbran
- Department of Molecular Physiology and Biophysics, The Center for Molecular Neuroscience, Vanderbilt University School of Medicine, Nashville, TN 37232, USA.
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Distribution of postsynaptic density (PSD)-95 and Ca2+/calmodulin-dependent protein kinase II at the PSD. J Neurosci 2003. [PMID: 14657186 DOI: 10.1523/jneurosci.23-35-11270.2003] [Citation(s) in RCA: 145] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Postsynaptic densities (PSDs) contain proteins that regulate synaptic transmission. We determined the positions of calcium/calmodulin-dependent protein kinase II (CaMKII) and PSD-95 within the three-dimensional structure of isolated PSDs using immunogold labeling, rotary shadowing, and electron microscopic tomography. The results show that all PSDs contain a central mesh immediately underlying the postsynaptic membrane. Label for PSD-95 is found on both the cytoplasmic and cleft sides of this mesh, averaging 12 nm from the cleft side. All PSDs label for PSD-95. The properties of CaMKII labeling are quite different. Label is virtually absent on the cleft sides of PSDs, but can be heavy on the cytoplasmic side at a mean distance of 25 nm from the cleft. In tomograms, CaMKII holoenzymes can be visualized directly, appearing as labeled, tower-like structures reflecting the 20 nm diameter of the holoenzyme. These towers protrude from the cytoplasmic side of the central mesh. There appears to be a local organization of CaMKII, as judged by fact that the nearest-neighbor distances are nearly invariant over a wide range of labeling density for CaMKII. The average density of CaMKII holoenzymes is highly variable, ranging from zero to values approaching a tightly packed state. This variability is significantly higher than that for PSD-95 and is consistent with an information storage role for CaMKII.
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31
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Tao-Cheng JH, Vinade L, Pozzo-Miller LD, Reese TS, Dosemeci A. Calcium/calmodulin-dependent protein kinase II clusters in adult rat hippocampal slices. Neuroscience 2003; 115:435-40. [PMID: 12421609 DOI: 10.1016/s0306-4522(02)00451-7] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We have previously reported the formation of calcium/calmodulin-dependent protein kinase II (CaMKII) clusters approximately 110 nm in diameter in hippocampal neurons in culture and in the intact adult brain, under conditions that simulate ischemic stress and increase [Ca(2+)](i) [Dosemeci et al. (2000) J. Neurosci. 20, 3076-3084; Tao-Cheng et al. (2001) Neuroscience 106, 69-78]. These observations suggest that ischemia-like conditions that prevail during the dissection of brain tissue for the preparation of hippocampal slices could lead to the formation of CaMKII clusters. We now show by pre-embedding immuno-electron microscopy that, indeed, CaMKII clusters are present in the CA1 pyramidal neurons in hippocampal slices from adult rats fixed immediately after dissection, and that the number of CaMKII clusters increases with the delay time between decapitation and fixation. Moreover, CaMKII clusters are typically localized near the endoplasmic reticulum. When acute slices are allowed to recover in oxygenated medium for 2 h, CaMKII clusters mostly disappear, indicating that clustering is reversible. Also, the postsynaptic density, another site for CaMKII accumulation under excitatory conditions, becomes thinner upon recovery. Treatment of recovered slices with high potassium for 90 s causes the re-appearance of CaMKII clusters in nearly all CA1 pyramidal cells examined. On the other hand, when dissociated hippocampal neurons in primary culture are exposed to the same depolarizing conditions, only approximately 25% of neurons exhibit CaMKII clusters, indicating a difference in the susceptibility of the neurons in culture and in acute slices to excitatory stimuli. Altogether these observations indicate that the effect of CaMKII clustering should be considered when interpreting experimental results obtained with hippocampal slices.
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Affiliation(s)
- J-H Tao-Cheng
- Laboratory of Neurobiology, NINDS, NIH, Building 36, Room 2A21, Bethesda, MD 20892, USA.
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Hudmon A, Schulman H. Neuronal CA2+/calmodulin-dependent protein kinase II: the role of structure and autoregulation in cellular function. Annu Rev Biochem 2002; 71:473-510. [PMID: 12045104 DOI: 10.1146/annurev.biochem.71.110601.135410] [Citation(s) in RCA: 506] [Impact Index Per Article: 23.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Highly enriched in brain tissue and present throughout the body, Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) is central to the coordination and execution of Ca(2+) signal transduction. The substrates phosphorylated by CaMKII are implicated in homeostatic regulation of the cell, as well as in activity-dependent changes in neuronal function that appear to underlie complex cognitive and behavioral responses, including learning and memory. The architecture of CaMKII holoenzymes is unique in nature. The kinase functional domains (12 per holoenzyme) are attached by stalklike appendages to a gear-shaped core, grouped into two clusters of six. Each subunit contains a catalytic, an autoregulatory, and an association domain. Ca(2+)/calmodulin (CaM) binding disinhibits the autoregulatory domain, allowing autophosphorylation and complex changes in the enzyme's sensitivity to Ca(2+)/CaM, including the generation of Ca(2+)/CaM-independent activity, CaM trapping, and CaM capping. These processes confer a type of molecular memory to the autoregulation and activity of CaMKII. Its function is intimately shaped by its multimeric structure, autoregulation, isozymic type, and subcellular localization; these features and processes are discussed as they relate to known and potential cellular functions of this multifunctional protein kinase.
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Affiliation(s)
- Andy Hudmon
- Department of Neurobiology, Stanford University School of Medicine, 299 Campus Drive, Stanford, California 94305, USA.
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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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Bradshaw JM, Hudmon A, Schulman H. Chemical quenched flow kinetic studies indicate an intraholoenzyme autophosphorylation mechanism for Ca2+/calmodulin-dependent protein kinase II. J Biol Chem 2002; 277:20991-8. [PMID: 11925447 DOI: 10.1074/jbc.m202154200] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Autophosphorylation of alpha-Ca(2+)/calmodulin-dependent protein kinase II (CaM kinase II) at Thr-286 generates Ca(2+)-independent activity that outlasts the initial Ca(2+) stimulus. Previous studies suggested that this autophosphorylation occurs between subunits within each CaM kinase II holoenzyme. However, electron microscopy studies have questioned this mechanism because a large distance separates a kinase domain from its neighboring subunit. Moreover, the recently discovered ability of CaM kinase II holoenzymes to self-associate has raised questions about data interpretation in previous investigations of autophosphorylation. In this work, we characterize the mechanism of CaM kinase II autophosphorylation. To eliminate ambiguity arising from kinase aggregation, we used dynamic light scattering to establish the monodispersity of all enzyme solutions. We then found using chemical quenched flow kinetics that the autophosphorylation rate was independent of the CaM kinase II concentration, results corroborating intraholoenzyme activation. Experiments with a monomeric CaM kinase II showed that phosphorylation of this construct is intermolecular, supporting intersubunit phosphorylation within a holoenzyme. The autophosphorylation rate at 30 degrees C was approximately 12 s(-1), more than 10-fold faster than past estimates. The ability of CaM kinase II to autophosphorylate through an intraholoenzyme, intersubunit mechanism is likely central to its functions of decoding Ca(2+) spike frequency and providing a sustained response to Ca(2+) signals.
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Affiliation(s)
- J Michael Bradshaw
- Department of Neurobiology, Stanford University, Stanford, California 94305, USA
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Sathyanarayanan PV, Poovaiah BW. Autophosphorylation-dependent inactivation of plant chimeric calcium/calmodulin-dependent protein kinase. EUROPEAN JOURNAL OF BIOCHEMISTRY 2002; 269:2457-63. [PMID: 12027883 DOI: 10.1046/j.1432-1033.2002.02904.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Chimeric calcium/calmodulin dependent protein kinase (CCaMK) is characterized by the presence of a visinin-like Ca(2+)-binding domain unlike other known calmodulin- dependent kinases. Ca(2+)-Binding to the visinin-like domain leads to autophosphorylation and changes in the affinity for calmodulin [Sathyanarayanan P.V., Cremo C.R. & Poovaiah B.W. (2000) J. Biol. Chem. 275, 30417-30422]. Here, we report that the Ca(2+)-stimulated autophosphorylation of CCaMK results in time-dependent loss of enzyme activity. This time-dependent loss of activity or self-inactivation due to autophosphorylation is also dependent on reaction pH and ATP concentration. Inactivation of the enzyme resulted in the formation of a sedimentable enzyme due to self-association. Specifically, autophosphorylation in the presence of 200 microm ATP at pH 7.5 resulted in the formation of a sedimentable enzyme with a 33% loss in enzyme activity. Under similar conditions at pH 6.5, the enzyme lost 67% of its activity and at pH 8.5, 84% enzyme activity was lost. Furthermore, autophosphorylation at either acidic or alkaline reaction pH lead to the formation of a sedimentable enzyme. Transmission electron microscopic studies on autophosphorylated kinase revealed particles that clustered into branched complexes. The autophosphorylation of wild-type kinase in the presence of AMP-PNP (an unhydrolyzable ATP analog) or the autophosphorylation-site mutant, T267A, did not show formation of branched complexes under the electron microscope. Autophosphorylation- dependent self-inactivation may be a mechanism of modulating the signal transduction pathway mediated by CCaMK.
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Affiliation(s)
- P V Sathyanarayanan
- Laboratory of Plant Molecular Biology and Physiology, Department of Horticulture, Washington State University, Pullman, WA 99164-6414, USA
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Tao-Cheng JH, Vinade L, Smith C, Winters CA, Ward R, Brightman MW, Reese TS, Dosemeci A. Sustained elevation of calcium induces Ca(2+)/calmodulin-dependent protein kinase II clusters in hippocampal neurons. Neuroscience 2002; 106:69-78. [PMID: 11564417 DOI: 10.1016/s0306-4522(01)00262-7] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Treatment of cultured hippocampal neurons with the mitochondrial uncoupler carbonyl cyanide m-chlorophenylhydrazone (CCCP) in the absence of glucose mimics ischemic energy depletion and induces formation of Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) clusters, spherical structures with diameters of 75-175 nm [Dosemeci et al., J. Neurosci. 20 (2000) 3076-3084]. The demonstration that CaMKII clustering occurs in the intact, adult rat brain upon interruption of blood flow indicates that clustering is not confined to cell cultures. Application of N-methyl-D-aspartate (250 microM, 15 min) to hippocampal cultures also induces cluster formation, suggesting a role for Ca(2+). Indeed, intracellular Ca(2+) monitored with Fluo3-AM by confocal microscopy reaches a sustained high level within 5 min of CCCP treatment. The appearance of immunolabeled CaMKII clusters, detected by electron microscopy, follows the onset of the sustained increase in intracellular Ca(2+). Moreover, CaMKII does not cluster when the rise in intracellular Ca(2+) is prevented by the omission of extracellular Ca(2+) during CCCP treatment, confirming that clustering is Ca(2+)-dependent. A lag period of 1-2 min between the onset of high intracellular Ca(2+) levels and the formation of CaMKII clusters suggests that a sustained increase in Ca(2+) level is necessary for the clustering. CaMKII clusters disappear within 2 h of returning the cultures to normal incubation conditions, at which time no significant cell death is detected. These results indicate that pathological conditions that promote sustained episodes of Ca(2+) overload result in a transitory clustering of CaMKII into spherical structures. CaMKII clustering may represent a cellular defense mechanism to sequester a portion of the CaMKII pool, thereby preventing excessive protein phosphorylation.
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Affiliation(s)
- J H Tao-Cheng
- Laboratory of Neurobiology, NINDS, NIH, Bethesda, MD 20892, USA
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Bayer KU, Schulman H. Regulation of signal transduction by protein targeting: the case for CaMKII. Biochem Biophys Res Commun 2001; 289:917-23. [PMID: 11741277 DOI: 10.1006/bbrc.2001.6063] [Citation(s) in RCA: 90] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Protein targeting is increasingly being recognized as a mechanism to ensure speed and specificity of intracellular signal transduction in a variety of biological systems. Conceptually, this is of particular importance for second-messenger-regulated protein kinases with a broad spectrum of substrates, such as the serine/threonine protein kinases PKA, PKC, and CaMKII (cyclic-AMP-dependent protein kinase, Ca(2+)-phospholipid-dependent protein kinase, and Ca(2+)/calmodulin-dependent protein kinase II). The activating second messengers of these enzymes can be produced or released in response to a large variety of "upstream" signals, and they can, in turn, regulate a large variety of "downstream" proteins. Targeting, e.g., via anchoring proteins, can link certain incoming stimuli with specific outgoing signals by restricting the subcellular compartment at which activation and/or action of a signaling molecule can take place. Elegant research on PKA and PKC reinforced the biological importance of such mechanisms. We will focus here on CaMKII, as recent advances in the understanding of its targeting have some significant general implications for signal transduction. The interaction of CaMKII with the NMDA receptor, for instance, shows that a targeting protein can not only specify the subcellular localization of a signaling effector, but can also directly influence its regulation.
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Affiliation(s)
- K U Bayer
- Department of Neurobiology, Stanford University School of Medicine, Stanford, California 94305-5125, USA
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