Identification of protein phosphatase 1 in synaptic junctions: dephosphorylation of endogenous calmodulin-dependent kinase II and synapse-enriched phosphoproteins

Shields, SM; Ingebritsen, TS; Kelly, PT

doi:10.1523/jneurosci.05-12-03414.1985

Cited by 163 publications

(98 citation statements)

References 8 publications

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“…Data presented thus far suggest that PP2A is a major CaMKII phosphatase in rat forebrain, in contrast to previous studies using isolated PSDs (Shields et al, 1985;Dosemeci and Reese, 1993). Because PSD-associated CaMKII may be functionally distinct from the soluble enzyme, PSD-associated protein phosphatases were investigated further.…”

Section: Dephosphorylation Of Camkii In Rat Forebrain Psdsmentioning

confidence: 84%

Differential Inactivation of Postsynaptic Density‐Associated and Soluble Ca²⁺/Calmodulin‐Dependent Protein Kinase II by Protein Phosphatases 1 and 2A

Strack¹,

Barban²,

Wadzinski

et al. 1997

Journal of Neurochemistry

285

207

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Autophosphorylation of Ca2/calmodulin-dependent protein kinase II (CaMKII) at Thr286 generates Ca2~-independent activity. As an initial step toward understanding CaMKII inactivation, protein phosphatase classes (PP1, PP2A, PP2B, or PP2C) responsible for dephosphorylation of Thr286 in rat forebrain subcellular fractions were identified using phosphatase inhibitors/activators, by fractionation using ion exchange chromatography and by immunoblotting. PP2A-like enzymes account for >70% of activity toward exogenous soluble Thr286-autophosphorylated CaMKIl in crude cytosol, membrane, and cytoskeletal extracts; PP1 and PP2C account for the remaining activity. CaMKII is present in particulate fractions, specifically associated with postsynaptic densities (PSD5); each protein phosphatase is also present in isolated PSD5, but only PP1 is enriched during PSO isolation. When isolated PSDs dephosphorylated exogenous soluble Thr286-autophosphorylated CaMKll, PP2A again made the major contribution. However, CaMKII endogenous to PSDs (32P autophosphorylated in the presence of Ca 2+/calmodu tin) was predominantly dephosphorylated by PP1. In addition, dephosphorylation of soluble and PSD-associated CaMKII in whole forebrain extracts was catalyzed predominantly by PP2A and PP1, respectively. Thus, soluble and PSD-associated forms of CaMKII appear to be dephosphorylated by distinct enzymes, suggesting that Ca2-independent activity of CaMKII is differentially regulated by protein phosphatases in distinct subcellular compartments. Key Words: Protein kinaseProtein phosphatase-Calmodulin -Postsynaptic density-Synaptic plasticity.

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Section: Dephosphorylation Of Camkii In Rat Forebrain Psdsmentioning

confidence: 84%

Differential Inactivation of Postsynaptic Density‐Associated and Soluble Ca²⁺/Calmodulin‐Dependent Protein Kinase II by Protein Phosphatases 1 and 2A

Strack¹,

Barban²,

Wadzinski

et al. 1997

Journal of Neurochemistry

285

207

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“…In addition, PKA activity can be decreased by Ca-dependent activation of phosphodiesterase (PDE). The resulting low PKA activity is accompanied by a disinhibition of PP1, which dephosphorylates CaMKII (Shenolikar and Narin 1991;Shields et al 1985), NMDAR (Westphal et al 1999), and glutamate receptor type 1 (GluR1) subunit of AMPA receptors (Lee et al 2000) to promote depotentiation.…”

Section: Discussionmentioning

confidence: 99%

“…Calcineurin then can inactivate inhibitor protein 1 (I-1), the endogenous inhibitor of serine/threonine protein phosphatase-1 (PP1); this allows the activation of PP1 (Oliver and Shenolikar 1998). PP1 dephosphorylates Ca 2ϩ /CaM protein kinase II (CaMKII) and other proteins, including glutamate receptors (Shenolikar and Nairn 1991;Shields et al 1985), to promote LTD.…”

Section: Introductionmentioning

confidence: 99%

Protein Phosphatases Mediate Depotentiation Induced by High-Intensity Theta-Burst Stimulation

Kang-Park¹,

Sarda²,

Jones³

et al. 2003

Journal of Neurophysiology

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Wilson. Protein phosphatases mediate depotentiation induced by highintensity theta-burst stimulation. J Neurophysiol 89: 684 -690, 2003; 10.1152/jn.01041.2001. We have previously reported that varying stimulus intensity produces qualitatively different types of synaptic plasticity in area CA1 of hippocampal slices: brief low-intensity (LI) theta-burst (TB) stimuli induce long-term potentiation (LTP), but if the stimulus intensity is increased (to mimic conditions that may exist during seizures), LTP is not induced; instead, high-intensity (HI) TB stimuli erase previously induced LTP ("TB depotentiation"). We now have explored the mechanisms underlying TB depotentiation using extracellular field recordings with pharmacological manipulations. We found that TB depotentiation was blocked by okadaic acid and calyculin A (inhibitors of serine/threonine protein phosphatases PP1 and PP2A), FK506 (a specific blocker of calcineurin, a Ca 2ϩ /calmodulin (CaM) protein phosphatase), and 8-Br-cAMP (an activator of protein kinase A) with 3-isobutyl-1-methylxanthine (IBMX, a phosphodiesterase inhibitor). These results suggest that protein phosphatase pathways are involved in the TB depotentiation similar to other type of down-regulating synaptic plasticity such as low-frequency stimulation (LFS)-induced long-term depression (LTD) and depotentiation in the rat hippocampus. However, TB depotentiation and LFS depotentiation could have differential functional significance.

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“…Similar data were obtained in four or five independent experiments. previous reports that dephosphorylation of CaMKII endogenous to PSDs is catalyzed by PP1 (29,31,32); however, CaMKII endogenous to isolated PSDs (i.e. in vivo translocated CaMKII) may represent a modified form of the kinase (46), possibly due to post-mortem ischemic conditions (11,47).…”

Section: Fig 2 Dephosphorylation Of [T286-p]camkii␣mentioning

confidence: 93%

Translocation of Autophosphorylated Calcium/Calmodulin-dependent Protein Kinase II to the Postsynaptic Density

Strack

Choi

Lovinger

et al. 1997

Journal of Biological Chemistry

280

236

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Calcium/calmodulin-dependent protein kinase II (CaMKII) undergoes calcium-dependent autophosphorylation, generating a calcium-independent form that may serve as a molecular substrate for memory. Here we show that calcium-independent CaMKII specifically binds to isolated postsynaptic densities (PSDs), leading to enhanced phosphorylation of many PSD proteins including the ␣-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid (AMPA)-type glutamate receptor. Furthermore, binding to PSDs changes CaMKII from a substrate for protein phosphatase 2A to a protein phosphatase 1 substrate. Translocation of CaMKII to PSDs occurs in hippocampal slices following treatments that induce CaMKII autophosphorylation and a form of long term potentiation. Thus, synaptic activation leads to accumulation of autophosphorylated, activated CaMKII in the PSD. This increases substrate phosphorylation and affects regulation of the kinase by protein phosphatases, which may contribute to enhancement of synaptic strength.CaMKII 1 isoforms comprise a family of broad specificity, calcium-activated kinases (1, 2). The ␣ and ␤ isoforms are abundantly expressed in the brain, with ␣ making up as much as 2% of total protein in certain brain regions (3). CaMKII is particularly enriched in PSDs (4, 5), cytoskeletal specializations apposed to the postsynaptic membrane of excitatory synapses that are thought to be scaffolds for neurotransmitter receptors, ion channels, and their postsynaptic modulators and effectors (reviewed in Refs. 6 and 7). Earlier reports suggested that CaMKII␣ constitutes as much as 50% of total PSD protein (8 -10), but PSDs prepared from rapidly homogenized brains are only 2-3-fold enriched in CaMKII␣ compared with whole forebrain extracts (3,11). CaMKII␣ knockout mice show impaired hippocampal long term potentiation, a cellular model for learning and memory (12). Conversely, introduction of CaMKII␣ into neurons augments postsynaptic responses and occludes further electrically induced long term potentiation (13,14).CaMKII␣ undergoes calcium/calmodulin-dependent autophosphorylation on Thr 286 in its regulatory domain, rendering the kinase partially calcium-independent (1, 2). This reaction has been proposed as a "molecular switch," translating transient calcium elevation into prolonged kinase activity (15, 16), which becomes subject to regulation by protein phosphatases. (19).Isolation of PSDs-PSDs were prepared from adult rat forebrains flash frozen within 45 s of euthanasia by detergent lysis of synaptosomes (20) except that 1 mM dithiothreitol, 1 mM phenylmethylsulfonyl fluoride, 1 mM benzamidine, and 10 g/ml leupeptin were included in all buffers. Synaptosomes were lysed in 1% (v/v) Triton X-100 and 150 mM KCl, and a second subsequent sucrose gradient was omitted because it yielded no further purification. PSDs displayed typical "donut" morphology by video-enhanced differential-interference contrast microscopy (21). PSDs prepared in the absence or the presence of the protein phosphatase inhibitor microcystin-LR (1 M) contained ...

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Identification of protein phosphatase 1 in synaptic junctions: dephosphorylation of endogenous calmodulin-dependent kinase II and synapse-enriched phosphoproteins

Abstract: A calcium/calmodulin-dependent protein kinase termed CaM-kinase

Cited by 163 publications

References 8 publications

Differential Inactivation of Postsynaptic Density‐Associated and Soluble Ca²⁺/Calmodulin‐Dependent Protein Kinase II by Protein Phosphatases 1 and 2A

Differential Inactivation of Postsynaptic Density‐Associated and Soluble Ca²⁺/Calmodulin‐Dependent Protein Kinase II by Protein Phosphatases 1 and 2A

Protein Phosphatases Mediate Depotentiation Induced by High-Intensity Theta-Burst Stimulation

Translocation of Autophosphorylated Calcium/Calmodulin-dependent Protein Kinase II to the Postsynaptic Density

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Identification of protein phosphatase 1 in synaptic junctions: dephosphorylation of endogenous calmodulin-dependent kinase II and synapse-enriched phosphoproteins

Abstract: A calcium/calmodulin-dependent protein kinase termed CaM-kinase

Cited by 163 publications

References 8 publications

Differential Inactivation of Postsynaptic Density‐Associated and Soluble Ca2+/Calmodulin‐Dependent Protein Kinase II by Protein Phosphatases 1 and 2A

Differential Inactivation of Postsynaptic Density‐Associated and Soluble Ca2+/Calmodulin‐Dependent Protein Kinase II by Protein Phosphatases 1 and 2A

Protein Phosphatases Mediate Depotentiation Induced by High-Intensity Theta-Burst Stimulation

Translocation of Autophosphorylated Calcium/Calmodulin-dependent Protein Kinase II to the Postsynaptic Density

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Differential Inactivation of Postsynaptic Density‐Associated and Soluble Ca²⁺/Calmodulin‐Dependent Protein Kinase II by Protein Phosphatases 1 and 2A

Differential Inactivation of Postsynaptic Density‐Associated and Soluble Ca²⁺/Calmodulin‐Dependent Protein Kinase II by Protein Phosphatases 1 and 2A