151
|
Plasticity of first-order sensory synapses: interactions between homosynaptic long-term potentiation and heterosynaptically evoked dopaminergic potentiation. J Neurosci 1999. [PMID: 10024349 DOI: 10.1523/jneurosci.19-05-01620.1999] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Persistent potentiations of the chemical and electrotonic components of the eighth nerve (NVIII) EPSP recorded in vivo in the goldfish reticulospinal neuron, the Mauthner cell, can be evoked by afferent tetanization or local dendritic application of an endogenous transmitter, dopamine (3-hydroxytyramine). These modifications are attributable to the activation of distinct intracellular kinase cascades. Although dopamine-evoked potentiation (DEP) is mediated by the cAMP-dependent protein kinase (PKA), tetanization most likely activates a Ca2+-dependent protein kinase via an increased intracellular Ca2+ concentration. We present evidence that the eighth nerve tetanus that induces LTP does not act by triggering dopamine release, because it is evoked in the presence of a broad spectrum of dopamine antagonists. To test for interactions between these pathways, we applied the potentiating paradigms sequentially. When dopamine was applied first, tetanization produced additional potentiation of the mixed synaptic response, but when the sequence was reversed, DEP was occluded, indicating that the synapses potentiated by the two procedures belong to the same or overlapping populations. Experiments were conducted to determine interactions between the underlying regulatory mechanisms and the level of their convergence. Inhibiting PKA does not impede tetanus-induced LTP, and chelating postsynaptic Ca2+ with BAPTA does not block DEP, indicating that the initial steps of the induction processes are independent. Pharmacological and voltage-clamp analyses indicate that the two pathways converge on functional AMPA/kainate receptors for the chemically mediated EPSP and gap junctions for the electrotonic component or at intermediaries common to both pathways. A cellular model incorporating these interactions is proposed on the basis of differential modulation of synaptic responses via receptor-protein phosphorylation.
Collapse
|
152
|
Adenylyl cyclase activation modulates activity-dependent changes in synaptic strength and Ca2+/calmodulin-dependent kinase II autophosphorylation. J Neurosci 1999. [PMID: 10087064 DOI: 10.1523/jneurosci.19-07-02500.1999] [Citation(s) in RCA: 82] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Activation of the Ca2+- and calmodulin-dependent protein kinase II (CaMKII) and its conversion into a persistently activated form by autophosphorylation are thought to be crucial events underlying the induction of long-term potentiation (LTP) by increases in postsynaptic Ca2+. Because increases in Ca2+ can also activate protein phosphatases that oppose persistent CaMKII activation, LTP induction may also require activation of signaling pathways that suppress protein phosphatase activation. Because the adenylyl cyclase (AC)-protein kinase A signaling pathway may provide a mechanism for suppressing protein phosphatase activation, we investigated the effects of AC activators on activity-dependent changes in synaptic strength and on levels of autophosphorylated alphaCaMKII (Thr286). In the CA1 region of hippocampal slices, briefly elevating extracellular Ca2+ induced an activity-dependent, transient potentiation of synaptic transmission that could be converted into a persistent potentiation by the addition of phosphatase inhibitors or AC activators. To examine activity-dependent changes in alphaCaMKII autophosphorylation, we replaced electrical presynaptic fiber stimulation with an increase in extracellular K+ to achieve a more global synaptic activation during perfusion of high Ca2+ solutions. In the presence of the AC activator forskolin or the protein phosphatase inhibitor calyculin A, this treatment induced a LTP-like synaptic potentiation and a persistent increase in autophosphorylated alphaCaMKII levels. In the absence of forskolin or calyculin A, it had no lasting effect on synaptic strength and induced a persistent decrease in autophosphorylated alphaCaMKII levels. Our results suggest that AC activation facilitates LTP induction by suppressing protein phosphatases and enabling a persistent increase in the levels of autophosphorylated CaMKII.
Collapse
|
153
|
Nishizaki T, Matsuoka T, Nomura T, Enikolopov G, Sumikawa K. Arachidonic acid potentiates currents through Ca2+-permeable AMPA receptors by interacting with a CaMKII pathway. BRAIN RESEARCH. MOLECULAR BRAIN RESEARCH 1999; 67:184-9. [PMID: 10101246 DOI: 10.1016/s0169-328x(99)00042-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
The present study investigated the effect of arachidonic acid on the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors, presumably heteromeric receptors formed of GluR1, GluR2, and GluR3, expressed in Xenopus oocytes. Arachidonic acid (10 microM) potentiated currents through receptors expressing GluR1 and 3 (GluR1,3) to 170% of basal level during initial 20 min following application, being still evident at 60-min washing-out of the drug, while it never or little enhanced currents through receptors expressing GluR1 and 2 (GluR1,2) or GluR1, 2, and 3 (GluR1,2,3) (110% 30 min after treatment). The effect of arachidonic acid on GluR1,3 currents was not observed in Ca2+-free extracellular solution, and the potentiation was blocked by either KN-93, a selective Ca2+/calmodulin-dependent protein kinase II (CaMKII) inhibitor, or NP217, an active CaMKII inhibitor peptide, when co-expressed with the receptors. In contrast, the protein synthesis inhibitor, cycloheximide, the selective inhibitor of cAMP-dependent protein kinase (PKA), H-89, the selective inhibitors of protein kinase C (PKC), PKCI and GF109203X, the mitogen-activated protein (MAP) kinase kinase inhibitor, PD98059, or the inactive CaMKII inhibitors, KN-92 and NP218, had no effect on the currents. In the assay of intracellular calcium mobilizations, Ca2+ influx in response to receptor activation was greatest with receptors formed in oocytes expressing GluR1,3. The results of the present study indicate that arachidonic acid induces a long-lasting potentiation of GluR1,3 currents, possibly as a result of the interaction with a CaMKII pathway.
Collapse
Affiliation(s)
- T Nishizaki
- Department of Physiology, Kobe University School of Medicine, 7-5-1 Kusunoki-cho, Chuo-ku, Kobe 650-0017, Japan.
| | | | | | | | | |
Collapse
|
154
|
Shen K, Meyer T. Dynamic control of CaMKII translocation and localization in hippocampal neurons by NMDA receptor stimulation. Science 1999; 284:162-6. [PMID: 10102820 DOI: 10.1126/science.284.5411.162] [Citation(s) in RCA: 547] [Impact Index Per Article: 21.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Calcium-calmodulin-dependent protein kinase II (CaMKII) is thought to increase synaptic strength by phosphorylating postsynaptic density (PSD) ion channels and signaling proteins. It is shown that N-methyl-D-aspartate (NMDA) receptor stimulation reversibly translocates green fluorescent protein-tagged CaMKII from an F-actin-bound to a PSD-bound state. The translocation time was controlled by the ratio of expressed beta-CaMKII to alpha-CaMKII isoforms. Although F-actin dissociation into the cytosol required autophosphorylation of or calcium-calmodulin binding to beta-CaMKII, PSD translocation required binding of calcium-calmodulin to either the alpha- or beta-CaMKII subunits. Autophosphorylation of CaMKII indirectly prolongs its PSD localization by increasing the calmodulin-binding affinity.
Collapse
Affiliation(s)
- K Shen
- Department of Cell Biology and Department of Pharmacology and Cancer Biology, Box 3709, Duke University Medical Center, Durham, NC 27710, USA
| | | |
Collapse
|
155
|
Derkach V, Barria A, Soderling TR. Ca2+/calmodulin-kinase II enhances channel conductance of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate type glutamate receptors. Proc Natl Acad Sci U S A 1999; 96:3269-74. [PMID: 10077673 PMCID: PMC15931 DOI: 10.1073/pnas.96.6.3269] [Citation(s) in RCA: 644] [Impact Index Per Article: 25.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The ability of central glutamatergic synapses to change their strength in response to the intensity of synaptic input, which occurs, for example, in long-term potentiation (LTP), is thought to provide a cellular basis for memory formation and learning. LTP in the CA1 field of the hippocampus requires activation of Ca2+/calmodulin-kinase II (CaM-KII), which phosphorylates Ser-831 in the GluR1 subunit of the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate glutamate receptor (AMPA-R), and this activation/phosphorylation is thought to be a postsynaptic mechanism in LTP. In this study, we have identified a molecular mechanism by which CaM-KII potentiates AMPA-Rs. Coexpression in HEK-293 cells of activated CaM-KII with GluR1 did not affect the glutamate affinity of the receptor, the kinetics of desensitization and recovery, channel rectification, open probability, or gating. Single-channel recordings identified multiple conductance states for GluR1, and coexpression with CaM-KII or a mutation of Ser-831 to Asp increased the contribution of the higher conductance states. These results indicate that CaM-KII can mediate plasticity at glutamatergic synapses by increasing single-channel conductance of existing functional AMPA-Rs or by recruiting new high-conductance-state AMPA-Rs.
Collapse
Affiliation(s)
- V Derkach
- Vollum Institute, Oregon Health Sciences University, Portland, OR 97201, USA
| | | | | |
Collapse
|
156
|
Agonist-induced changes in substituted cysteine accessibility reveal dynamic extracellular structure of M3-M4 loop of glutamate receptor GluR6. J Neurosci 1999. [PMID: 9880585 DOI: 10.1523/jneurosci.19-02-00644.1999] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Recent evidence suggests that the transmembrane topology of ionotropic glutamate receptors differs from other members of the ligand-gated ion channel superfamily. However, the structure of the segment linking membrane domains M3 and M4 (the M3-M4 loop) remains controversial. Although various data indicate that this loop is extracellular, other results suggest that serine residues in this segment are sites of phosphorylation and channel modulation by intracellular protein kinases. To reconcile these data, we hypothesized that the M3-M4 loop structure is dynamic and, more specifically, that the portion containing putative phosphorylation sites may be translocated across the membrane to the cytoplasmic side during agonist binding. To test this hypothesis, we mutated Ser 684, a putative cAMP-dependent protein kinase site in the kainate-type glutamate receptor GluR6, to Cys. Results of biochemical and electrophysiological experiments are consistent with Cys 684 being accessible, in the unliganded state, from the extracellular side to modification by a Cys-specific biotinylating reagent followed by streptavidin (SA). Interestingly, our data suggest that this residue becomes inaccessible to the extracellular biotinylating reagent during agonist binding. However, we find it unlikely that Cys 684 undergoes membrane translocation, because the addition of SA to Cys-biotinylated GluR6(S684C) has no effect on peak glutamate-evoked current and only a small effect on macroscopic desensitization. We conclude that residue 684 in GluR6 is extracellular in the receptor-channel's closed, unliganded state and does not cross the membrane after agonist binding. However, an agonist-induced conformational change in the receptor substantially alters accessibility of position 684 to the extracellular environment.
Collapse
|
157
|
Borges K, Dingledine R. AMPA receptors: molecular and functional diversity. PROGRESS IN BRAIN RESEARCH 1999; 116:153-70. [PMID: 9932376 DOI: 10.1016/s0079-6123(08)60436-7] [Citation(s) in RCA: 87] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Affiliation(s)
- K Borges
- Department of Pharmacology, Emory University School of Medicine, Atlanta, GA 30322, USA.
| | | |
Collapse
|
158
|
Wenthold RJ, Roche KW. The organization and regulation of non-NMDA receptors in neurons. PROGRESS IN BRAIN RESEARCH 1999; 116:133-52. [PMID: 9932375 DOI: 10.1016/s0079-6123(08)60435-5] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Affiliation(s)
- R J Wenthold
- Laboratory of Neurochemistry, NIH, Bethesda, MD, USA.
| | | |
Collapse
|
159
|
Abstract
Synaptic NMDA-type glutamate receptors are anchored to the second of three PDZ (PSD-95/Discs large/ZO-1) domains in the postsynaptic density (PSD) protein PSD-95. Here, we report that citron, a protein target for the activated form of the small GTP-binding protein Rho, preferentially binds the third PDZ domain of PSD-95. In GABAergic neurons from the hippocampus, citron forms a complex with PSD-95 and is concentrated at the postsynaptic side of glutamatergic synapses. Citron is expressed only at low levels in glutamatergic neurons in the hippocampus and is not detectable at synapses onto these neurons. In contrast to citron, p135 SynGAP, an abundant synaptic Ras GTPase-activating protein that can bind to all three PDZ domains of PSD-95, and Ca2+/calmodulin-dependent protein kinase II (CaM kinase II) are concentrated postsynaptically at glutamatergic synapses on glutamatergic neurons. CaM kinase II is not expressed and p135 SynGAP is expressed in less than half of hippocampal GABAergic neurons. Segregation of citron into inhibitory neurons does not occur in other brain regions. For example, citron is expressed at high levels in most thalamic neurons, which are primarily glutamatergic and contain CaM kinase II. In several other brain regions, citron is present in a subset of neurons that can be either GABAergic or glutamatergic and can sometimes express CaM kinase II. Thus, in the hippocampus, signal transduction complexes associated with postsynaptic NMDA receptors are different in glutamatergic and GABAergic neurons and are specialized in a way that is specific to the hippocampus.
Collapse
|
160
|
Holohean AM, Hackman JC, Davidoff RA. Mechanisms involved in the metabotropic glutamate receptor-enhancement of NMDA-mediated motoneurone responses in frog spinal cord. Br J Pharmacol 1999; 126:333-41. [PMID: 10051153 PMCID: PMC1565774 DOI: 10.1038/sj.bjp.0702263] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
1. The metabotropic glutamate receptor (mGluR) agonist trans-(+/-)-1-amino-1,3-cyclopentanedicarboxylic acid (trans-ACPD) (10-100 microM) depolarized isolated frog spinal cord motoneurones, a process sensitive to kynurenate (1.0 mM) and tetrodotoxin (TTX) (0.783 microM). 2. In the presence of NMDA open channel blockers [Mg2+; (+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine hydrogen maleate (MK801); 3,5-dimethyl-1-adamantanamine hydrochloride (memantine)] and TTX, trans-ACPD significantly potentiated NMDA-induced motoneurone depolarizations, but not alpha-amino-3-hydroxy-5-methylisoxazole-4-proprionate (AMPA)- or kainate-induced depolarizations. 3. NMDA potentiation was blocked by (RS)-alpha-methyl-4-carboxyphenylglycine (MCPG) (240 microM), but not by alpha-methyl-(2S,3S,4S)-alpha-(carboxycyclopropyl)-glycine (MCCG) (290 microM) or by alpha-methyl-(S)-2-amino-4-phosphonobutyrate (L-MAP4) (250 microM), and was mimicked by 3,5-dihydroxyphenylglycine (DHPG) (30 microM), but not by L(+)-2-amino-4-phosphonobutyrate (L-AP4) (100 microM). Therefore, trans-ACPD's facilitatory effects appear to involve group I mGluRs. 4. Potentiation was prevented by the G-protein decoupling agent pertussis toxin (3-6 ng ml(-1), 36 h preincubation). The protein kinase C inhibitors staurosporine (2.0 microM) and N-(2-aminoethyl)-5-isoquinolinesulphonamide HCI (H9) (77 microM) did not significantly reduce enhanced NMDA responses. Protein kinase C activation with phorbol-12-myristate 13-acetate (5.0 microM) had no effect. 5. Intracellular Ca2+ depletion with thapsigargin (0.1 microM) (which inhibits Ca2+/ATPase), 1,2-bis(O-aminophenoxy)ethane-N,N,N',N'-tetracetic acid acetyl methyl ester (BAPTA-AM) (50 microM) (which buffers elevations of [Ca2+]i), and bathing spinal cords in nominally Ca2+-free medium all reduced trans-ACPD's effects. 6. The calmodulin antagonists N-(6-aminohexyl)-5-chloro-1-naphthalenesulphonamide (W7) (100 microM) and chlorpromazine (100 microM) diminished the potentiation. 7. In summary, group I mGluRs selectively facilitate NMDA-depolarization of frog motoneurones via a G-protein, a rise in [Ca2+]i from the presumed generation of phosphoinositides, binding of Ca2+ to calmodulin, and lessening of the Mg2+-produced channel block of the NMDA receptor.
Collapse
Affiliation(s)
- Alice M Holohean
- Neurophysiology Laboratory, Veterans Affairs Medical Center, PO Box 016960, University of Miami School of Medicine, Miami, Florida 33101, U.S.A
- Department of Neurology (D4-5), PO Box 016960, University of Miami School of Medicine, Miami, Florida 33101, U.S.A
| | - John C Hackman
- Neurophysiology Laboratory, Veterans Affairs Medical Center, PO Box 016960, University of Miami School of Medicine, Miami, Florida 33101, U.S.A
- Spinal Cord Pharmacology Laboratory, Veterans Affairs Medical Center, PO Box 016960, University of Miami School of Medicine, Miami, Florida 33101, U.S.A
- Department of Neurology (D4-5), PO Box 016960, University of Miami School of Medicine, Miami, Florida 33101, U.S.A
| | - Robert A Davidoff
- Neurophysiology Laboratory, Veterans Affairs Medical Center, PO Box 016960, University of Miami School of Medicine, Miami, Florida 33101, U.S.A
- Department of Neurology (D4-5), PO Box 016960, University of Miami School of Medicine, Miami, Florida 33101, U.S.A
- Author for correspondence: .
| |
Collapse
|
161
|
Yan Z, Hsieh-Wilson L, Feng J, Tomizawa K, Allen PB, Fienberg AA, Nairn AC, Greengard P. Protein phosphatase 1 modulation of neostriatal AMPA channels: regulation by DARPP-32 and spinophilin. Nat Neurosci 1999; 2:13-7. [PMID: 10195174 DOI: 10.1038/4516] [Citation(s) in RCA: 235] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Modulation of AMPA-type glutamate channels is important for synaptic plasticity. Here we provide physiological evidence that the activity of AMPA channels is regulated by protein phosphatase 1 (PP-1) in neostriatal neurons and identify two distinct molecular mechanisms of this regulation. One mechanism involves control of PP-1 catalytic activity by DARPP-32, a dopamine- and cAMP-regulated phosphoprotein highly enriched in neostriatum. The other involves binding of PP-1 to spinophilin, a protein that colocalizes PP-1 with AMPA receptors in postsynaptic densities. The results suggest that regulation of anchored PP-1 is important for AMPA-receptor-mediated synaptic transmission and plasticity.
Collapse
Affiliation(s)
- Z Yan
- Laboratory of Molecular and Cellular Neuroscience, Rockefeller University, New York, New York 10021, USA
| | | | | | | | | | | | | | | |
Collapse
|
162
|
Caputi A, Gardoni F, Cimino M, Pastorino L, Cattabeni F, Di Luca M. CaMKII-dependent phosphorylation of NR2A and NR2B is decreased in animals characterized by hippocampal damage and impaired LTP. Eur J Neurosci 1999; 11:141-8. [PMID: 9987018 DOI: 10.1046/j.1460-9568.1999.00414.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The calcium-calmodulin-dependent protein kinase II (CaMKII) subserves activity-dependent plasticity in central neurons. To examine in vivo the implication of CaMKII activity in synaptic plasticity, we used an animal model characterized by developmentally induced targeted neuronal ablation within the cortex and the hippocampus, and showing, at presynaptic level, molecular alterations leading to facilitation of glutamate release in hippocampal synapses (methylazoxymethanol-treated rats, MAM-rats). We report here that at the postsynaptic side, the activity of CaMKII is markedly decreased in MAM-rats when compared to controls, although the concentration of the enzyme in Post Synaptic Density (PSD) is not altered. This effect is confined to PSD-associated CaMKII, as enzyme activity tested in the soluble fraction is unchanged in MAM-rats. In addition, the decreased activity is not due to inhibition by autophosphorylation in specific sites within the calmodulin-binding domain, as preincubation with purified phosphatases 1 and 2A failed to restore CaMKII activity in PSD of MAM-rats. The CaMKII-dependent phosphorylation of NR2A/B subunits of NMDA receptor is lower in MAM-rats when compared to controls (51.77 +/- 7.39% of controls level), as revealed in back-phosphorylation experiments. In addition, a treatment able to restore long-term potentiation (LTP) in hippocampal slices from MAM-rats, e.g. exposure to D-serine, is able to restore CaMKII activity to the control value.
Collapse
Affiliation(s)
- A Caputi
- Institute of Pharmacological Sciences, University of Milano, Italy
| | | | | | | | | | | |
Collapse
|
163
|
Lee HK, Kameyama K, Huganir RL, Bear MF. NMDA induces long-term synaptic depression and dephosphorylation of the GluR1 subunit of AMPA receptors in hippocampus. Neuron 1998; 21:1151-62. [PMID: 9856470 DOI: 10.1016/s0896-6273(00)80632-7] [Citation(s) in RCA: 524] [Impact Index Per Article: 20.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Brief bath application of N-methyl-D-aspartate (NMDA) to hippocampal slices produces long-term synaptic depression (LTD) in CA1 that is (1) sensitive to postnatal age, (2) saturable, (3) induced postsynaptically, (4) reversible, and (5) not associated with a change in paired pulse facilitation. Chemically induced LTD (Chem-LTD) and homosynaptic LTD are mutually occluding, suggesting a common expression mechanism. Using phosphorylation site-specific antibodies, we found that induction of chem-LTD produces a persistent dephosphorylation of the GluR1 subunit of AMPA receptors at serine 845, a cAMP-dependent protein kinase (PKA) substrate, but not at serine 831, a substrate of protein kinase C (PKC) and calcium/calmodulin-dependent protein kinase II (CaMKII). These results suggest that dephosphorylation of AMPA receptors is an expression mechanism for LTD and indicate an unexpected role of PKA in the postsynaptic modulation of excitatory synaptic transmission.
Collapse
Affiliation(s)
- H K Lee
- Howard Hughes Medical Institute, Department of Neuroscience, Brown University, Providence, Rhode Island 02912, USA
| | | | | | | |
Collapse
|
164
|
Carroll RC, Nicoll RA, Malenka RC. Effects of PKA and PKC on miniature excitatory postsynaptic currents in CA1 pyramidal cells. J Neurophysiol 1998; 80:2797-800. [PMID: 9819284 DOI: 10.1152/jn.1998.80.5.2797] [Citation(s) in RCA: 76] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Protein kinases play an important role in controlling synaptic strength at excitatory synapses on CA1 pyramidal cells. We examined the effects of activating cAMP-dependent protein kinase or protein kinase C (PKC) on the frequency and amplitude of miniature excitatory postsynaptic currents (mEPSCs) with perforated patch recording techniques. Both forskolin and phorbol-12,13-dibutryate (PDBu) caused a large increase in mEPSC frequency, but only PDBu increased mEPSC amplitude, an effect that was not observed when standard whole cell recording was performed. These results support biochemical observations indicating that PKC, similar to calcium/calmodulin-dependent protein kinase II, has an important role in controlling synaptic strength via modulation of AMPA receptor function, potentially through the direct phosphorylation of the GluR1 subunit.
Collapse
Affiliation(s)
- R C Carroll
- Department of Psychiatry, University of California, San Francisco, California 94143, USA
| | | | | |
Collapse
|
165
|
Coomber CJ. Site-selective autophosphorylation of Ca2+/calmodulin-dependent protein kinase II as a synaptic encoding mechanism. Neural Comput 1998; 10:1653-78. [PMID: 9744891 DOI: 10.1162/089976698300017070] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
A detailed kinetic model of the Ca2+/calmodulin-dependent protein kinase II (CaMKII) is presented in which subunits undergo autophosphorylation at several sites in a manner that depends on the frequency and duration of Ca2+ spikes. It is shown that high-frequency stimulation causes autophosphorylation of the autonomy site (Thr286), and promotes persistent catalytic activity. On the other hand, low-frequency stimulation is shown to cause autophosphorylation of an inhibitory site (Thr306), which prevents subunit activation. This site-selective autophosphorylation provides the basis for a molecular switch. When activated by a strong stimulus, the switch remains on for many minutes, even in the presence of a CaMKII-specific phosphatase. However, prolonged low-frequency stimulation disables the switch, and influences the response to subsequent stimulation. It is conceivable that a regulatory mechanism such as this may permit CaMKII to mediate synaptic frequency encoding and thereby direct an appropriate change in synaptic efficacy. It is indicated how the behavior of the model may relate to the induction of long-term potentiation.
Collapse
Affiliation(s)
- C J Coomber
- School of Computing and Mathematics, Deakin University, Geelong, Victoria, Australia
| |
Collapse
|
166
|
Mitani A, Namba S, Ikemune K, Yanase H, Arai T, Kataoka K. Postischemic enhancements of N-methyl-D-aspartic acid (NMDA) and non-NMDA receptor-mediated responses in hippocampal CA1 pyramidal neurons. J Cereb Blood Flow Metab 1998; 18:1088-98. [PMID: 9778185 DOI: 10.1097/00004647-199810000-00005] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Glutamate receptor-mediated responses were investigated by using a whole-cell recording and an intracellular calcium ion ([Ca2+]i) imaging in gerbil postischemic hippocampal slices prepared at 1, 3, 6, 9, 12, and 24 hours after 5-minute ischemia. Bath application of N-methyl-D-aspartic acid (NMDA), alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA), and kainate showed that NMDA-, AMPA- and kainate-induced currents were enhanced in postischemic CA1 pyramidal neurons at 1 to 12 hours after 5-minute ischemia. NMDA and non-NMDA receptor-mediated excitatory postsynaptic currents (EPSC) were examined in postischemic CA1 pyramidal neurons at 3 hours after 5-minute ischemia to confirm whether synaptic responses are enhanced in the postischemic CA1 pyramidal neurons. The amplitudes of NMDA- and non-NMDA-receptor-mediated EPSC were enhanced in the postischemic CA1 pyramidal neurons. NMDA-, AMPA-, and kainate-induced [Ca2+]i elevations were also examined to determine whether the enhancement of currents is accompanied by the enhancement of [Ca2+]i elevation. The enhancements of NMDA-, AMPA-, and kainate-induced [Ca2+]i elevations were shown in the postischemic CA1. These results indicate that NMDA and non-NMDA receptor-mediated responses are persistently enhanced in the CA1 pyramidal neurons 1 to 12 hours after transient ischemia, and suggest that the enhancement of glutamate receptor-mediated responses may act as one of crucial factors in the pathologic mechanism responsible for leading postischemic CA1 pyramidal neurons to irreversible neuronal injury.
Collapse
Affiliation(s)
- A Mitani
- Department of Physiology, School of Medicine, Ehime University, Japan
| | | | | | | | | | | |
Collapse
|
167
|
CA1 Long-Term Potentiation Is Diminished but Present in Hippocampal Slices from α-CaMKII Mutant Mice. Learn Mem 1998. [DOI: 10.1101/lm.5.4.344] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Previous work has shown that mice missing the α-isoform of calcium–calmodulin-dependent protein kinase II (α-CaMKII) have a deficiency in CA1 hippocampal long-term potentiation (LTP). Follow-up studies on subsequent generations of these mutant mice in a novel inbred background by our laboratories have shown that whereas a deficiency in CA1 LTP is still present in α-CaMKII mutant mice, it is different both quantitatively and qualitatively from the deficiency first described. Mice of a mixed 129SvOla/SvJ;BALB/c;C57Bl/6 background derived from brother/sister mating of the α-CaMKII mutant line through multiple generations (>10) were produced by use of in vitro fertilization. Although LTP at 60 min post-tetanus was clearly deficient in these (−/−) α-CaMKII mice (42.6%, n = 33) compared with (+/+) α-CaMKII control animals (81.7%,n = 17), α-CaMKII mutant mice did show a significant level of LTP. The amount of LTP observed in α-CaMKII mutants was normally distributed, blocked by APV (2.7%, n = 8), and did not correlate with age. Although this supports a role for α-CaMKII in CA1 LTP, it also suggests that a form of α-CaMKII-independent LTP is present in mice that could be dependent on another kinase, such as the β-isoform of CaMKII. A significant difference in input/output curves was also observed between (−/−) α-CaMKII and (+/+) α-CaMKII animals, suggesting that differences in synaptic transmission may be contributing to the LTP deficit in mutant mice. However, tetani of increasing frequency (50, 100, and 200 Hz) did not reveal a higher threshold for potentiation in (−/−) α-CaMKII mice compared with (+/+) α-CaMKII controls.
Collapse
|
168
|
Shen K, Teruel MN, Subramanian K, Meyer T. CaMKIIbeta functions as an F-actin targeting module that localizes CaMKIIalpha/beta heterooligomers to dendritic spines. Neuron 1998; 21:593-606. [PMID: 9768845 DOI: 10.1016/s0896-6273(00)80569-3] [Citation(s) in RCA: 269] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Ca2+/calmodulin-dependent protein kinase II (CaMKII) is a serine/threonine protein kinase that regulates long-term potentiation and other forms of neuronal plasticity. Functional differences between the neuronal CaMKIIalpha and CaMKIIbeta isoforms are not yet known. Here, we use green fluorescent protein-tagged (GFP-tagged) CaMKII isoforms and show that CaMKIIbeta is bound to F-actin in dendritic spines and cell cortex while CaMKIIalpha is largely a cytosolic enzyme. When expressed together, the two isoforms form large heterooligomers, and a small fraction of CaMKIIbeta is sufficient to dock the predominant CaMKIIalpha to the actin cytoskeleton. Thus, CaMKIIbeta functions as a targeting module that localizes a much larger number of CaMKIIalpha isozymes to synaptic and cytoskeletal sites of action.
Collapse
Affiliation(s)
- K Shen
- Department of Cell Biology, Duke University Medical Center Durham, North Carolina 27710, USA
| | | | | | | |
Collapse
|
169
|
Strack S, Colbran RJ. Autophosphorylation-dependent targeting of calcium/ calmodulin-dependent protein kinase II by the NR2B subunit of the N-methyl- D-aspartate receptor. J Biol Chem 1998; 273:20689-92. [PMID: 9694809 DOI: 10.1074/jbc.273.33.20689] [Citation(s) in RCA: 374] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Activation and Thr286 autophosphorylation of calcium/calmodulindependent kinase II (CaMKII) following Ca2+ influx via N-methyl-D-aspartate (NMDA)-type glutamate receptors is essential for hippocampal long term potentiation (LTP), a widely investigated cellular model of learning and memory. Here, we show that NR2B, but not NR2A or NR1, subunits of NMDA receptors are responsible for autophosphorylation-dependent targeting of CaMKII. CaMKII and NMDA receptors colocalize in neuronal dendritic spines, and a CaMKII.NMDA receptor complex can be isolated from brain extracts. Autophosphorylation induces direct high-affinity binding of CaMKII to a 50 amino acid domain in the NR2B cytoplasmic tail; little or no binding is observed to NR2A and NR1 cytoplasmic tails. Specific colocalization of CaMKII with NR2B-containing NMDA receptors in transfected cells depends on receptor activation, Ca2+ influx, and Thr286 autophosphorylation. Translocation of CaMKII because of interaction with the NMDA receptor Ca2+ channel may potentiate kinase activity and provide exquisite spatial and temporal control of postsynaptic substrate phosphorylation.
Collapse
Affiliation(s)
- S Strack
- Department of Molecular Physiology and Biophysics and Center for Molecular Neuroscience, Vanderbilt University Medical Center, Nashville, Tennessee 37232-0615, USA
| | | |
Collapse
|
170
|
Cammarota M, Bernabeu R, Levi De Stein M, Izquierdo I, Medina JH. Learning-specific, time-dependent increases in hippocampal Ca2+/calmodulin-dependent protein kinase II activity and AMPA GluR1 subunit immunoreactivity. Eur J Neurosci 1998; 10:2669-76. [PMID: 9767396 DOI: 10.1046/j.1460-9568.1998.00254.x] [Citation(s) in RCA: 113] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Ca2+/calmodulin-dependent protein kinase II (CAMK II) and one of its target, alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA), glutamate receptors have been shown to participate in both long-term potentiation (LTP) in the hippocampus, and in spatial, as well as in a variety, of learning paradigms. Recently, we were able to demonstrate that the intrahippocampal infusion of a specific inhibitor of CAMK II (KN62) provoked full retrograde amnesia of an inhibitory avoidance learning in rats when given immediately, but not 120 or 240 min, after training. Furthermore, this task is accompanied by a rapid, selective and reversible increase in hippocampal [3H] AMPA receptor binding. Here we report the effect of this aversively motivated learning task on CAMK II activity, and AMPA GluR1 subunit phosphorylation and immunoreactivity in the hippocampus. One trial inhibitory avoidance training is associated with a learning-specific, time-dependent increase (25-78%) in both total and Ca2+-independent activities of CAMK II in the hippocampus of rats killed immediately (0 min), but not 120 min, after training. In addition, immunoblotting experiments showed an increment in the amount of the alpha-subunit of CAMK II at 0, 30 and 120 min after training. An increase in the in vitro phosphorylation of alpha- and beta-subunits of CAMK II was also observed in hippocampal synaptosomal membranes (SPM) of trained rats killed immediately and 30 min post-training. In addition, inhibitory avoidance is accompanied by a 20% increase in GluR1 phosphorylation and a 33% increase in GluR1 immunoreactivity 120 min after training. No significant changes were observed in shocked animals. Phosphorylation of hippocampal SPM from naive control animals in conditions suitable for CAMK II activation resulted in a large increase in the density of [3H] AMPA binding (+ 100%). Taken together, these findings confirm and extend previous data suggesting that CAMK II and AMPA glutamate receptors in the hippocampus participate in the early phase of memory formation of an inhibitory avoidance learning.
Collapse
Affiliation(s)
- M Cammarota
- Instituto de Biología Celular y Neurociencias 'Prof. Dr Eduardo de Robertis', Facultad de Medicina, Universidad de Buenos Aires, 1121 Buenos Aires, Argentina
| | | | | | | | | |
Collapse
|
171
|
Standley S, Baudry M. Rapid effects of kainate administration on alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptor properties in rat hippocampus. Exp Neurol 1998; 152:208-13. [PMID: 9710519 DOI: 10.1006/exnr.1998.6851] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We investigated changes in AMPA receptor properties in rat hippocampus 5 h after systemic kainate administration. Quantitative [3H]AMPA autoradiography and Western blot analysis of receptor subunits GluR1-3 in different subcellular fractions were used to evaluate possible alterations in binding characteristics and immunological properties of the receptors in synaptic and nonsynaptic fractions. Both ligand-binding and Western blots revealed significant changes in binding and immunological properties of nonsynaptic receptors but relatively smaller changes in synaptic receptors 5 h after kainate administration. GluR2/3 showed a greater relative change in the synaptic receptor population compared to GluR1, suggesting either a shift in subunit composition of AMPA receptors or the formation of a synaptic subpopulation of AMPA receptors with truncated C-terminal domain of GluR1 subunits. The effects of kainic acid were blocked by cycloheximide treatment indicating that the changes were due at least in part to increased synthesis of AMPA receptor subunits. The results indicate that excessive synaptic activity produces rapid changes in both synaptic and nonsynaptic AMPA receptor properties.
Collapse
Affiliation(s)
- S Standley
- Program in Neuroscience, University of Southern California, Los Angeles, California, 90089-2520, USA
| | | |
Collapse
|
172
|
Chabot C, Gagné J, Giguère C, Bernard J, Baudry M, Massicotte G. Bidirectional modulation of AMPA receptor properties by exogenous phospholipase A2 in the hippocampus. Hippocampus 1998; 8:299-309. [PMID: 9662143 DOI: 10.1002/(sici)1098-1063(1998)8:3<299::aid-hipo11>3.0.co;2-w] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The synaptic modifications underlying long-term potentiation (LTP) and long-term depression (LTD) of synaptic transmission in various brain structures may result from changes in the properties of the alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA) subtype of glutamate receptors. In the present study, we report that treatment of rat synaptoneurosomes with increasing concentrations of phospholipase A2 (PLA2) produces a biphasic effect on AMPA receptor binding, with low concentrations causing a decrease and high concentrations an increase in agonist binding. Analysis of the saturation kinetics of 3H-AMPA binding revealed that the biphasic effect of PLA2 was due to modifications in receptor affinity and not to changes in the maximum number of binding sites for AMPA receptors. The 12-lipoxygenase inhibitors preferentially reduced PLA2-induced decrease in AMPA binding and treatment of hippocampal synaptoneurosomes with arachidonic acid (AA) or 12-HPETE, the first metabolite generated from the hydrolysis of AA by 12-lipoxygenases, decreased 3H-AMPA binding. Moreover, electrophysiological experiments indicated that the 12-lipoxygenase inhibitor baicalein totally blocked LTD formation in area CA1 of hippocampal slices. The decrease in 3H-AMPA binding elicited by low concentrations of PLA2, as well as the level of LTD, were partially reduced by AA-861, a 5-lipoxygenase inhibitor, while the cyclooxygenase inhibitor indomethacin did not prevent LTD formation or the effects of PLA2 on 3H-AMPA binding. Our results provide evidence for a possible involvement of lipoxygenase metabolites in the regulation of AMPA receptor during synaptic depression. In addition, they strongly support the idea that the same biochemical pathway, i.e., NMDA receptor activation and endogenous PLA2 stimulation, may represent a common mechanism resulting in AMPA receptor alterations for both LTP and LTD formation.
Collapse
Affiliation(s)
- C Chabot
- Département de Chimie-Biologie, Université du Québec à Trois-Rivières, Canada
| | | | | | | | | | | |
Collapse
|
173
|
Papa M, Sergeant JA, Sadile AG. Reduced transduction mechanisms in the anterior accumbal interface of an animal model of Attention-Deficit Hyperactivity Disorder. Behav Brain Res 1998; 94:187-95. [PMID: 9708849 DOI: 10.1016/s0166-4328(97)00179-4] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The aim of this study was to map the neural substrates of attention-deficit hyperactivity disorder (ADHD) in the spontaneously hypertensive rat (SHR), which is thought to be a model for ADHD. To this aim, the Ca2+/calmodulin-dependent protein kinase II (CaMKII) and transcription factors (TF) were used as markers. The focus of interest was the nucleus accumbens complex (ACB) which is thought to be an interface between limbic and motor systems. Juvenile, male rats of the SHR line and Wistar-Kyoto (WKY) controls were perfused and the brains processed for immunocytochemistry for CaMKII and the TF peptides of the FOS, JUN-B and ZIF-268 families. The results revealed that: (i) in both groups there were more CaMKII-positive neurones in the shell than in the core of the ACB; (ii) SHR had a reduced number of CaMKII-positive elements in anterior portions of the shell; and (iii) SHR had a lower expression of peptide products of the FOS family (c-FOS, in particular) and ZIF-268. In addition, there was a lower expression of c-FOS and zif-268 in the core of the ACB in the SHR. In contrast, there was an increased basal level of JUN-B in the core of the ACB of SHR. The reduced number of CaMKII and TF-positive elements in the most rostral portions of the accumbal complex of SHR, associated to the higher number of binding sites for the DA D-1/D-5 subtype, appears as a discrete alteration in the prosomeric development of the anterior basal forebrain and could be the key to the understanding of ADHD.
Collapse
Affiliation(s)
- M Papa
- Institute of Human Anatomy, Second University of Naples, Italy
| | | | | |
Collapse
|
174
|
Bi R, Bi X, Baudry M. Phosphorylation regulates calpain-mediated truncation of glutamate ionotropic receptors. Brain Res 1998; 797:154-8. [PMID: 9630591 DOI: 10.1016/s0006-8993(98)00433-8] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Pre-incubation of synaptic membranes with phosphatase inhibitors significantly reduces the extent of calpain-mediated truncation of both GluR1 and NR2 subunits of AMPA and NMDA receptors, respectively. The same treatment did not modify calpain-mediated truncation of spectrin. These results might have important implications for mechanisms of synaptic plasticity as the balance of kinase/phosphatase activity and calpain has been proposed to regulate synaptic efficacy at glutamatergic synapses.
Collapse
Affiliation(s)
- R Bi
- Neuroscience Program, USC, Los Angeles, CA 90089-2520, USA
| | | | | |
Collapse
|
175
|
Coomber C. Current theories of neuronal information processing performed by Ca2+/calmodulin-dependent protein kinase II with support and insights from computer modelling and simulation. COMPUTERS & CHEMISTRY 1998; 22:251-63. [PMID: 9618904 DOI: 10.1016/s0097-8485(97)00002-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Ca2+/calmodulin-dependent protein kinase II (CaMKII) is concentrated in brain, and is particularly enriched in synaptic structures where it comprises 20-50% of all proteins. The abundant nature of CaMKII and its ability to phosphorylate a wide range of substrate proteins, including itself, earmarks it as a protein kinase that may have a vital role in neuronal information processing and memory. A computer model of CaMKII is investigated that incorporates recent findings about the geometrical arrangement of subunits, the mechanism of Ca(2+)-dependent subunit activation, and Ca(2+)-independent autophosphorylation. The model is framed as a system of nonlinear differential equations. It is demonstrated numerically that (1) CaMKII is tuned to be activated by stimulation protocols associated with the induction of long-term potentiation; (2) the observed slow dissociation of trapped Ca2+/calmodulin may require the autonomy site to be protected from dephosphorylation; and (3) Ca(2+)-independent kinase activity is expressed in a manner akin to a graded switch. The model validates current theories concerning how CaMKII may be a Ca2+ pulse frequency detector, a molecular switch, or a mediator of the threshold for long-term synaptic plasticity.
Collapse
Affiliation(s)
- C Coomber
- Faculty of Science and Technology, Deakin University, Geelong, Australia.
| |
Collapse
|
176
|
Yamauchi T, Yoshimura Y. Phosphorylation-dependent reversible translocation of Ca2+/calmodulin-dependent protein kinase II to the postsynaptic densities. Life Sci 1998; 62:1617-21. [PMID: 9585146 DOI: 10.1016/s0024-3205(98)00117-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The translocation of soluble Ca2+/calmodulin-dependent protein kinase II (CaM kinase II) to postsynaptic densities (PSDs) was investigated. When soluble CaM kinase II previously autophosphorylated was incubated with PSDs, the kinase was precipitated by centrifugation, indicating that the soluble kinase associated with PSDs and formed a PSD-CaM kinase II complex. Ca2+-independent activity generated by autophosphorylation of the kinase was retained in the complex. A number of PSD proteins were phosphorylated by the kinase associated with PSDs in both the absence and presence of Ca2+. When PSD-CaM kinase II complex was incubated at 30 degrees C, the enzyme was dephosphorylated and released from the complex. These results indicate that CaM kinase II reversibly translocates to PSDs in a phosphorylation-dependent manner.
Collapse
Affiliation(s)
- T Yamauchi
- Department of Biochemistry, Faculty of Pharmaceutical Sciences, The University of Tokushima, Japan
| | | |
Collapse
|
177
|
Ge Q, Feldman JL. AMPA receptor activation and phosphatase inhibition affect neonatal rat respiratory rhythm generation. J Physiol 1998; 509 ( Pt 1):255-66. [PMID: 9547398 PMCID: PMC2230945 DOI: 10.1111/j.1469-7793.1998.255bo.x] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
1. We investigated the role of alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA) receptors and their regulation in affecting respiratory-related neurones in a neonatal rat medullary slice that spontaneously generates respiratory-related rhythm and motor output in the hypoglossal (XII) nerve. 2. Bath application of the AMPA receptor antagonist 1-(4-aminophenyl)-4-methyl-7,8-methylenedioxy-5H-2, 3-benzodiazepine (GYKI) completely blocked XII nerve activity, as well as respiratory-related synaptic drives in neurones within the preBötzinger Complex (preBotC), site of rhythm generation in the slice. 3. Local application of GYKI to the preBötC blocked respiratory rhythm. Local application of AMPA to the preBötC increased rhythm frequency and depolarized respiratory-related neurones. 4. In the presence of tetrodotoxin (TTX), GYKI completely blocked the inward current induced by local application of AMPA, but not that induced by kainate. 5. Local application of okadaic acid, a membrane-permeable inhibitor of phosphatase 1 and 2A, to the preBotC increased the frequency of respiratory motor discharge. 6. Intracellular application of microcystin, a membrane-impermeable inhibitor of phosphatase 1 and 2A, enhanced endogenous inspiratory drive and exogenous AMPA-induced current (in the presence of TTX) in preBotC inspiratory neurones. Both the enhanced inspiratory drive and the increased AMPA-induced current were completely blocked by GYKI. 7. We suggest that AMPA receptor activation and AMPA receptor modulation by phosphorylation are crucial for the rhythm generation within the preBötC.
Collapse
Affiliation(s)
- Q Ge
- Department of Physiological Science, University of California, Los Angeles, CA 90095-1763, USA
| | | |
Collapse
|
178
|
Kennedy MB. Signal transduction molecules at the glutamatergic postsynaptic membrane. BRAIN RESEARCH. BRAIN RESEARCH REVIEWS 1998; 26:243-57. [PMID: 9651538 DOI: 10.1016/s0165-0173(97)00043-x] [Citation(s) in RCA: 152] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
We have applied techniques from modern molecular biology and biochemistry to unravel the complex molecular structure of the postsynaptic membrane at glutamatergic synapses in the central nervous system. We have characterized a set of new proteins that are constituents of the postsynaptic density, including PSD-95, densin-180, citron (a rho/rac effector protein), and synaptic gp130 Ras GAP (a new Ras GTPase-activating protein). The structure of PSD-95 revealed a new protein motif, the PDZ domain, that plays an important role in the assembly of signal transduction complexes at intercellular junctions. More recently, we have used new imaging tools to observe the dynamics of autophosphorylation of CaM kinase II in intact hippocampal tissue. We have been able to detect changes in the amount of autophosphorylated CaM kinase II in dendrites, individual synapses, and somas of hippocampal neurons following induction of long-term potentiation by tetanic stimulation. In addition, we have observed a specific increase in the concentration of CaM kinase II in dendrites of neurons receiving tetanic stimulation. This increase appears to be the result of dendritic synthesis of new protein. Over the next several years we will apply similar methods to study regulatory changes that occur at the molecular level in glutamatergic synapses in the CNS as the brain processes and stores new information.
Collapse
Affiliation(s)
- M B Kennedy
- Division of Biology 216-76, California Institute of Technology, Pasadena, CA 91125, USA.
| |
Collapse
|
179
|
Abstract
Gonadal steroid hormones may affect, simultaneously, a wide variety of neuronal targets, influencing the way the brain reacts to many external and internal stimuli. Some of the effects of these hormones are permanent, whereas others are short lasting and transitory. The ways gonadal steroids affect brain function are very versatile and encompass intracellular, as well as, membrane receptors. In some cases, these compounds can interact with several neurotransmitter systems and/or transcription factors modulating gene expression. Knowledge about the mechanisms implicated in steroid hormone action will facilitate the understanding of brain sexual dimorphism and how we react to the environment, to drugs, and to certain disease states.
Collapse
Affiliation(s)
- R Alonso
- Department of Physiology, Canarian University Hospital, University of La Laguna School of Medicine, Santa Cruz de Tenerife, Spain.
| | | |
Collapse
|
180
|
Kahn ES, Kinumi T, Tobin SL, Matsumoto H. Phosrestide-1, a peptide derived from the Drosophila photoreceptor protein phosrestin I, is a potent substrate for Ca2+/calmodulin-dependent protein kinase II from rat brain. Comp Biochem Physiol B Biochem Mol Biol 1998; 119:739-46. [PMID: 9787765 DOI: 10.1016/s0305-0491(98)00050-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Multifunctional Ca2+/calmodulin-dependent protein kinase type II (CaMK II) plays a crucial role in mediation of cellular responses to rising cytosolic Ca2+ levels. We find that the novel peptide substrate PGTIEKKRSNAMKKMKSIEQHR serves as a highly potent substrate for CaMK II enzymes purified from both Drosophila and rat. The peptide is derived from a photoreceptor-specific protein, phosrestin I, of the Drosophila compound eye and is designated as phosrestide-1. Using saturating substrate concentrations, the enzymes from both species transfer the gamma-phosphoryl group of ATP to phosrestide-1 at a level three to ten times greater than to the commercially available mammalian-derived CaMK II substrates, autocamtide-3 and syntide-2. This indicates a conservation of substrate preferences for CaMK II derived from distantly related species, a dipteran fly and a mammal. Although phosrestide-1 contains two potential serine residues for CaMK II phosphorylation, we find that only the C-terminal serine is phosphorylated by rat CaMK II. However, removal of the upstream sequence containing the N-terminal serine substantially reduced the potency of phosrestide-1 as a CaMK II substrate to a level comparable to that of syntide-2 or autocamtide-3. We also find that a peptide representing the N-terminal segment of phosrestide-1 does not inhibit either CaMK II. Therefore, the enhanced potency of phosrestide-1 as a CaMK II substrate is likely to be due to a preferred conformation of the peptide induced by the N-terminal segment rather than to a specific binding of the enzymes to the N-terminus of the peptide. To the best of our knowledge, phosrestide-1 is the first CaMK II substrate which is designed based on an invertebrate sequence. The high phosphorylation level of phosrestide-1 by CaMK II of mammalian origin may reflect highly conserved CaMK II signaling cascades between vertebrates and invertebrates.
Collapse
Affiliation(s)
- E S Kahn
- Department of Biochemistry and Molecular Biology, University of Oklahoma, Oklahoma City 73190, USA
| | | | | | | |
Collapse
|
181
|
Abstract
Recent work has shown that D1/D5 dopamine receptors can enhance long-term potentiation (LTP). We investigated whether D1/D5 receptors also affect depotentiation, the reversal of LTP by low-frequency stimulation. D1/D5 agonists greatly reduced depotentiation, an effect that was inhibited by a D1/D5 antagonist. The D1/D5 effect appears to be mediated by adenylyl cyclase (AC) and cAMP-dependent protein kinase (PKA), because it was mimicked by the AC activator forskolin and was inhibited by the AC and PKA inhibitors. In vivo studies show that dopamine is released when a reward occurs. Our results raise the possibility that the memory of events before reward might be retained selectively, because dopamine blocks their erasure.
Collapse
|
182
|
Tompa P, Friedrich P. Synaptic metaplasticity and the local charge effect in postsynaptic densities. Trends Neurosci 1998; 21:97-102. [PMID: 9530914 DOI: 10.1016/s0166-2236(97)01176-4] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Synaptic plasticity might be one of the elementary processes that underlies higher brain functions, such as learning and memory. Intriguingly, the capacity of a synapse for plastic changes itself displays marked variation or plasticity. This higher-order plasticity, or metaplasticity, appears to depend on the same macromolecules as plasticity, most notably the NMDA receptor and Ca2+/calmodulin kinase II; yet we do not understand metaplasticity in molecular terms. Metaplasticity has a feedback-inhibition character that confers stability to synaptic patterns, whereas in plasticity, the molecular events implicated tend to have an opposite effect. As a resolution to this difference, we suggest that metaplasticity be considered in a biophysical context. It has been shown that autophosphorylation of Ca2+/calmodulin kinase II in postsynaptic densities generates changes in the local electrostatic potential sufficient to affect the direction of synaptic plasticity. We propose that this finding could help explain both the puzzling abundance of Ca2+/calmodulin kinase II in the postsynaptic density and the metaplasticity of synaptic transmission.
Collapse
Affiliation(s)
- P Tompa
- Institute of Enzymology, Biological Research Center, Hungarian Academy of Sciences, Budapest
| | | |
Collapse
|
183
|
Michaelis EK. Molecular biology of glutamate receptors in the central nervous system and their role in excitotoxicity, oxidative stress and aging. Prog Neurobiol 1998; 54:369-415. [PMID: 9522394 DOI: 10.1016/s0301-0082(97)00055-5] [Citation(s) in RCA: 389] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Forty years of research into the function of L-glutamic acid as a neurotransmitter in the vertebrate central nervous system (CNS) have uncovered a tremendous complexity in the actions of this excitatory neurotransmitter and an equally great complexity in the molecular structures of the receptors activated by L-glutamate. L-Glutamate is the most widespread excitatory transmitter system in the vertebrate CNS and in addition to its actions as a synaptic transmitter it produces long-lasting changes in neuronal excitability, synaptic structure and function, neuronal migration during development, and neuronal viability. These effects are produced through the activation of two general classes of receptors, those that form ion channels or "ionotropic" and those that are linked to G-proteins or "metabotropic". The pharmacological and physiological characterization of these various forms over the past two decades has led to the definition of three forms of ionotropic receptors, the kainate (KA), AMPA, and NMDA receptors, and three groups of metabotropic receptors. Twenty-seven genes are now identified for specific subunits of these receptors and another five proteins are likely to function as receptor subunits or receptor associated proteins. The regulation of expression of these protein subunits, their localization in neuronal and glial membranes, and their role in determining the physiological properties of glutamate receptors is a fertile field of current investigations into the cell and molecular biology of these receptors. Both ionotropic and metabotropic receptors are linked to multiple intracellular messengers, such as Ca2+, cyclic AMP, reactive oxygen species, and initiate multiple signaling cascades that determine neuronal growth, differentiation and survival. These cascades of complex molecular events are presented in this review.
Collapse
Affiliation(s)
- E K Michaelis
- Department of Pharmacology and Toxicology, University of Kansas, Lawrence 66047, USA
| |
Collapse
|
184
|
Abstract
Over the last decade, a large body of information regarding the amino acid sequences and tertiary structures of many proteins has accumulated. Subtle similarities in sequence patterns identified between glutamate receptors and bacterial periplasmic substrate-binding proteins have suggested that structural kinship exists between these protein families. Many of the bacterial periplasmic binding proteins but none of the glutamate receptors have been crystallized so far. The following article reviews how the resemblance between these two protein families led to computer-assisted structural models of crucial elements involved in ligand binding by various glutamate receptors. A plausible dynamic model of the molecular mechanism of activation and desensitization of glutamate-receptor channels is also discussed.
Collapse
Affiliation(s)
- Y Paas
- Neurobiologie Moléculaire, UA CNRS D1284, Département des Biotechnologies, Institut Pasteur, Paris, France
| |
Collapse
|
185
|
Bi X, Standley S, Baudry M. Posttranslational regulation of ionotropic glutamate receptors and synaptic plasticity. INTERNATIONAL REVIEW OF NEUROBIOLOGY 1998; 42:227-84. [PMID: 9476175 DOI: 10.1016/s0074-7742(08)60612-1] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Affiliation(s)
- X Bi
- University of Southern California, Los Angeles 90089-2520, USA
| | | | | |
Collapse
|
186
|
Turrigiano GG, Leslie KR, Desai NS, Rutherford LC, Nelson SB. Activity-dependent scaling of quantal amplitude in neocortical neurons. Nature 1998; 391:892-6. [PMID: 9495341 DOI: 10.1038/36103] [Citation(s) in RCA: 1578] [Impact Index Per Article: 60.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Information is stored in neural circuits through long-lasting changes in synaptic strengths. Most studies of information storage have focused on mechanisms such as long-term potentiation and depression (LTP and LTD), in which synaptic strengths change in a synapse-specific manner. In contrast, little attention has been paid to mechanisms that regulate the total synaptic strength of a neuron. Here we describe a new form of synaptic plasticity that increases or decreases the strength of all of a neuron's synaptic inputs as a function of activity. Chronic blockade of cortical culture activity increased the amplitude of miniature excitatory postsynaptic currents (mEPSCs) without changing their kinetics. Conversely, blocking GABA (gamma-aminobutyric acid)-mediated inhibition initially raised firing rates, but over a 48-hour period mESPC amplitudes decreased and firing rates returned to close to control values. These changes were at least partly due to postsynaptic alterations in the response to glutamate, and apparently affected each synapse in proportion to its initial strength. Such 'synaptic scaling' may help to ensure that firing rates do not become saturated during developmental changes in the number and strength of synaptic inputs, as well as stabilizing synaptic strengths during Hebbian modification and facilitating competition between synapses.
Collapse
Affiliation(s)
- G G Turrigiano
- Department of Biology and Center for Complex Systems, Brandeis University, Waltham, Massachusetts 02254, USA.
| | | | | | | | | |
Collapse
|
187
|
Abstract
Altered calcium (Ca2+) homeostasis is thought to play a key role in aging and neuropathology resulting in memory deficits. Several forms of hippocampal synaptic plasticity are dependent on Ca2+, providing a potential link between altered Ca2+ homeostasis and memory deficits associated with aging. The current study reviews evidence for Ca2+ dysregulation during aging which could interact with Ca(2+)-dependent synaptic plasticity. The authors suggest that changes in Ca2+ regulation could adjust the thresholds for synaptic modification, favoring processes for depression of synaptic strength during aging.
Collapse
Affiliation(s)
- T C Foster
- Department of Psychology, University of Virginia, Charlottesville 22903, USA.
| | | |
Collapse
|
188
|
Tighilet B, Huntsman MM, Hashikawa T, Murray KD, Isackson PJ, Jones EG. Cell-specific expression of type II calcium/calmodulin-dependent protein kinase isoforms and glutamate receptors in normal and visually deprived lateral geniculate nucleus of monkeys. J Comp Neurol 1998; 390:278-96. [PMID: 9453671 DOI: 10.1002/(sici)1096-9861(19980112)390:2<278::aid-cne10>3.0.co;2-u] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
In situ hybridization histochemistry and immunocytochemistry were used to map distributions of cells expressing mRNAs encoding alpha, beta, gamma, and delta isoforms of type II calcium/calmodulin-dependent protein kinase (CaMKII), alpha-amino-3-hydroxy-5-methyl-4-isoxazoleproprionate (AMPA)/ kainate receptor subunits, (GluR1-7), and N-methyl-D-aspartate (NMDA) receptor subunits, NR1 and NR2A-D, or stained by subunit-specific immunocytochemistry in the dorsal lateral geniculate nuclei of macaque monkeys. Relationships of specific isoforms with particular glutamate receptor types may be important elements in neural plasticity. CaMKII-alpha is expressed only by neurons in the S laminae and interlaminar plexuses of the dorsal lateral geniculate nucleus, but may form part of a more widely distributed matrix of similar cells extending from the geniculate into adjacent nuclei. CaMKII-beta, -gamma, and -delta isoforms are expressed by all neurons in principal and S laminae and interlaminar plexuses. In principal laminae, they are down-regulated by monocular deprivation lasting 8-21 days. All glutamate receptor subunits are expressed by neurons in principal and S laminae and interlaminar plexuses. The AMPA/kainate subunits, GluR1, 2, 5, and 7, are expressed at low levels, although GluR1 immunostaining appears selectively to stain interneurons. GluR3 is expressed at weak, GluR 6 at moderate and GluR 4 at high levels. NMDA subunits, NR1 and NR2A, B, and D, are expressed at moderate to low levels. GluR4, GluR6 and NMDA subunits are down-regulated by visual deprivation. CaMKII-alpha expression is unique in comparison with other CaMKII isoforms which may, therefore, have more generalized roles in cell function. The results demonstrate that all of the isoforms are associated with NMDA receptors and with AMPA receptors enriched with GluR4 subunits, which implies high calcium permeability and rapid gating.
Collapse
Affiliation(s)
- B Tighilet
- Department of Anatomy and Neurobiology, University of California, Irvine 92697, USA
| | | | | | | | | | | |
Collapse
|
189
|
Abstract
Calcium-calmodulin-dependent protein kinase II (CaMKII) promotes the maturation of retinotectal glutamatergic synapses in Xenopus. Whether CaMKII activity also controls morphological maturation of optic tectal neurons was tested using in vivo time-lapse imaging of single neurons over periods of up to 5 days. Dendritic arbor elaboration slows with maturation, in correlation with the onset of CaMKII expression. Elevating CaMKII activity in young neurons by viral expression of constitutively active CaMKII slowed dendritic growth to a rate comparable to that of mature neurons. CaMKII overexpression stabilized dendritic structure in more mature neurons, whereas CaMKII inhibition increased their dendritic growth. Thus, endogenous CaMKII activity limits dendritic growth and stabilizes dendrites, and it may act as an activity-dependent mediator of neuronal maturation.
Collapse
Affiliation(s)
- G Y Wu
- Cold Spring Harbor Laboratory, 1 Bungtown Road, Cold Spring Harbor, NY 11724, USA
| | | |
Collapse
|
190
|
Abstract
A wide variety of mechanisms have been identified that can regulate the alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA)-receptor complex. Modulation has been shown to occur at the nucleic acid level via RNA editing and alternative splicing. At the posttranslational level, processes such as phosphorylation, glycosylation, chemical modification of reactive groups on the receptor proteins, interaction with a putative receptor-associated modulatory protein, and changes in the lipid environment have been reported to regulate receptor binding and function. In this review, we discuss general aspects of the cell biology, pharmacology, and function of AMPA receptors. In particular, we focus on some factors shown to modulate agonist binding and discuss possible molecular mechanisms underlying the regulation observed.
Collapse
Affiliation(s)
- K K Dev
- Department of Anatomy, University of Bristol, Medical School, UK
| | | |
Collapse
|
191
|
Murray KD, Hayes VY, Gall CM, Isackson PJ. Attenuation of the seizure-induced expression of BDNF mRNA in adult rat brain by an inhibitor of calcium/calmodulin-dependent protein kinases. Eur J Neurosci 1998; 10:377-87. [PMID: 9753146 DOI: 10.1046/j.1460-9568.1998.00019.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
We have examined the potential involvement of calcium/calmodulin-dependent protein kinases in the regulation of brain-derived neurotrophic factor mRNA in vivo following kainic acid (kainate)-induced seizure activity by in situ hybridization. KN-62, a specific inhibitor of calcium/calmodulin-dependent protein kinase type II and IV, blocked the characteristic induction of brain-derived neurotrophic factor mRNA seen following seizure activity. This blockade was specific to calcium/calmodulin-dependent protein kinase type II and IV as inhibitors of both protein kinase C and cAMP-dependent protein kinase had no effect. Inhibition of brain-derived neurotrophic factor mRNA increases varied between brain regions; an almost complete inhibition was seen throughout cortical regions, whereas only partial inhibitory effects were noted within hippocampus. A similar inhibition of increased c-fos mRNA was observed throughout cortical, hippocampal and diencephalic regions. The two predominant brain-derived neurotrophic factor transcripts induced by kainate, containing exons I or III, were differentially affected by KN-62. The cortical induction of exon I was blocked by KN-62, whereas exon III was not, providing additional evidence for the differential regulation of individual brain-derived neurotrophic factor transcripts and demonstrating that inhibition of brain-derived neurotrophic factor induction was not due to general blockade of seizure activity throughout the neocortex. These data implicate calcium/calmodulin-dependent protein kinase type II or IV in the regulation of brain-derived neurotrophic factor mRNA in vivo and suggest regionally specific mechanisms occur throughout the brain.
Collapse
Affiliation(s)
- K D Murray
- Department of Biochemistry and Molecular Biology, Mayo Clinic Jacksonville, FL 32224, USA.
| | | | | | | |
Collapse
|
192
|
Barria A, Derkach V, Soderling T. Identification of the Ca2+/calmodulin-dependent protein kinase II regulatory phosphorylation site in the alpha-amino-3-hydroxyl-5-methyl-4-isoxazole-propionate-type glutamate receptor. J Biol Chem 1997; 272:32727-30. [PMID: 9407043 DOI: 10.1074/jbc.272.52.32727] [Citation(s) in RCA: 318] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Ca2+/CaM-dependent protein kinase II (CaM-KII) can phosphorylate and potentiate responses of alpha-amino3-hydroxyl-5-methyl-4-isoxazole-propionate-type glutamate receptors in a number of systems, and recent studies implicate this mechanism in long term potentiation, a cellular model of learning and memory. In this study we have identified this CaM-KII regulatory site using deletion and site-specific mutants of glutamate receptor 1 (GluR1). Only mutations affecting Ser831 altered the 32P peptide maps of GluR1 from HEK-293 cells co-expressing an activated CaM-KII. Likewise, when CaM-KII was infused into cells expressing GluR1, the Ser831 to Ala mutant failed to show potentiation of the GluR1 current. The Ser831 site is specific to GluR1, and CaM-KII did not phosphorylate or potentiate current in cells expressing GluR2, emphasizing the importance of the GluR1 subunit in this regulatory mechanism. Because Ser831 has previously been identified as a protein kinase C phosphorylation site (Roche, K. W., O'Brien, R. J., Mammen, A. L., Bernhardt, J., and Huganir, R. L. (1996) Neuron 16, 1179-1188), this raises the possibility of synergistic interactions between CaM-KII and protein kinase C in regulating synaptic plasticity.
Collapse
Affiliation(s)
- A Barria
- Vollum Institute, Oregon Health Sciences University, Portland, Oregon 97201, USA
| | | | | |
Collapse
|
193
|
Mammen AL, Kameyama K, Roche KW, Huganir RL. Phosphorylation of the alpha-amino-3-hydroxy-5-methylisoxazole4-propionic acid receptor GluR1 subunit by calcium/calmodulin-dependent kinase II. J Biol Chem 1997; 272:32528-33. [PMID: 9405465 DOI: 10.1074/jbc.272.51.32528] [Citation(s) in RCA: 352] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Modulation of alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic Acid (AMPA) receptors in the brain by protein phosphorylation may play a crucial role in the regulation of synaptic plasticity. Previous studies have demonstrated that calmodulin (CaM) kinase II can phosphorylate and modulate AMPA receptors. However, the sites of CaM kinase phosphorylation have not been unequivocally identified. In the current study, we have generated two phosphorylation site-specific antibodies to analyze the phosphorylation of the glutamate receptor GluR1 subunit. These antibodies recognize GluR1 only when it is phosphorylated on serine residues 831 or 845. We have used these antibodies to demonstrate that serine 831 is specifically phosphorylated by CaM kinase II in transfected cells expressing GluR1 as well as in hippocampal slice preparations. Two-dimensional phosphopeptide mapping experiments indicate that Ser-831 is the major site of CaM kinase II phosphorylation on GluR1. In addition, treatment of hippocampal slice preparations with phorbol esters and forskolin increase the phosphorylation of serine 831 and 845, respectively, indicating that protein kinase C and protein kinase A phosphorylate these residues in hippocampal slices. These results identify the site of CaM kinase phosphorylation of the GluR1 subunit and demonstrate that GluR1 is multiply phosphorylated by protein kinase A, protein kinase C, and CaM kinase II in situ.
Collapse
Affiliation(s)
- A L Mammen
- Howard Hughes Medical Institute, Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
| | | | | | | |
Collapse
|
194
|
Hell JW. Phosphorylation of receptors and ion channels and their interaction with structural proteins. Neurochem Int 1997; 31:651-8. [PMID: 9364451 DOI: 10.1016/s0197-0186(97)00023-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Affiliation(s)
- J W Hell
- Department of Pharmacology, University of Wisconsin, Madison 53706-1532, USA
| |
Collapse
|
195
|
Shirke AM, Malinow R. Mechanisms of potentiation by calcium-calmodulin kinase II of postsynaptic sensitivity in rat hippocampal CA1 neurons. J Neurophysiol 1997; 78:2682-92. [PMID: 9356418 DOI: 10.1152/jn.1997.78.5.2682] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Mechanisms of potentiation by calcium-calmodulin kinase II of postsynaptic sensitivity in rat hippocampal CA1 neurons. J. Neurophysiol. 78: 2682-2692, 1997. Preactivated recombinant alpha-calcium-calmodulin dependent multifunctional protein kinase II (CaMKII*) was perfused internally into CA1 hippocampal slice neurons to test the effect on synaptic transmission and responses to exogenous application of glutamate analogues. After measurement of baseline transmission, internal perfusion of CaMKII* increased synaptic strength in rat hippocampal neurons and diminished the fraction of synaptic failures. After measurement of baseline responses to applied transmitter, CaMKII* perfusion potentiated responses to kainate but not responses to N-methyl--aspartate. Internal perfusion of CaMKII*potentiated the maximal effect of kainate. Potentiation by CaMKII* did not change the time course of responses to kainate, whereas increasing response size by pharmacologically manipulating desensitization or deactivation rate constants significantly altered the time course of responses. Nonstationary fluctuation analysis of responses to kainate showed a decrease in the coefficient of variation after potentiation by CaMKII*. These data support the hypothesis that CaMKII increases postsynaptic responsiveness by increasing the available number of active alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid/kainate channels and suggests that a similar process may occur during the expression of long-term potentiation.
Collapse
Affiliation(s)
- A M Shirke
- Department of Physiology and Biophysics, University of Iowa, Iowa City, Iowa 52242, USA
| | | |
Collapse
|
196
|
Izquierdo I, Medina JH. Memory formation: the sequence of biochemical events in the hippocampus and its connection to activity in other brain structures. Neurobiol Learn Mem 1997; 68:285-316. [PMID: 9398590 DOI: 10.1006/nlme.1997.3799] [Citation(s) in RCA: 683] [Impact Index Per Article: 25.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Recent data have demonstrated a biochemical sequence of events in the rat hippocampus that is necessary for memory formation of inhibitory avoidance behavior. The sequence initially involves the activation of three different types of glutamate receptors followed by changes in second messengers and biochemical cascades led by enhanced activity of protein kinases A, C, and G and calcium-calmodulin protein kinase II, followed by changes in glutamate receptor subunits and binding properties and increased expression of constitutive and inducible transcription factors. The biochemical events are regulated early after training by hormonal and neurohumoral mechanisms related to alertness, anxiety, and stress, and 3-6 h after training by pathways related to mood and affect. The early modulation is mediated locally by GABAergic, cholinergic, and noradrenergic synapses and by putative retrograde synaptic messengers, and extrinsically by the amygdala and possibly the medial septum, which handle emotional components of memories and are direct or indirect sites of action for several hormones and neurotransmitters. The late modulation relies on dopamine D1, beta-noradrenergic, and 5HT1A receptors in the hippocampus and dopaminergic, noradrenergic, and serotoninergic pathways. Evidence indicates that hippocampal activity mediated by glutamate AMPA receptors must persist during at least 3 h after training in order for memories to be consolidated. Probably, this activity is transmitted to other areas, including the source of the dopaminergic, noradrenergic, and serotoninergic pathways, and the entorhinal and posterior parietal cortex. The entorhinal and posterior parietal cortex participate in memory consolidation minutes after the hippocampal chain of events starts, in both cases through glutamate NMDA receptor-mediated processes, and their intervention is necessary in order to complete memory consolidation. The hippocampus, amygdala, entorhinal cortex, and parietal cortex are involved in retrieval in the first few days after training; at 30 days from training only the entorhinal and parietal cortex are involved, and at 60 days only the parietal cortex is necessary for retrieval. Based on observations on other forms of hippocampal plasticity and on memory formation in the chick brain, it is suggested that the hippocampal chain of events that underlies memory formation is linked to long-term storage elsewhere through activity-dependent changes in cell connectivity.
Collapse
Affiliation(s)
- I Izquierdo
- Departamento de Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
| | | |
Collapse
|
197
|
Yoshimura Y, Yamauchi T. Phosphorylation-dependent reversible association of Ca2+/calmodulin-dependent protein kinase II with the postsynaptic densities. J Biol Chem 1997; 272:26354-9. [PMID: 9334208 DOI: 10.1074/jbc.272.42.26354] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The association of soluble Ca2+/calmodulin-dependent protein kinase II (CaM kinase II) with postsynaptic densities (PSDs) was determined by activity assay, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and immunoblotting of the enzyme. Soluble CaM kinase II was autophosphorylated with ATP in the presence of Ca2+ and calmodulin, and then it was incubated with PSDs. Autophosphorylated CaM kinase II was precipitated with PSDs by centrifugation. The kinase that was not autophosphorylated did not precipitate with PSDs. These results indicate that the soluble previously autophosphorylated CaM kinase II associates with PSDs and forms PSD-CaM kinase II complex. A maximum of about 60 microg of soluble CaM kinase II bound to 1 mg of PSD protein under the experimental conditions. Ca2+-independent activity generated by autophosphorylation of the kinase was retained in the PSD-CaM kinase II complex. The CaM kinase II thus associated with PSDs phosphorylated a number of PSD proteins in both the absence and presence of Ca2+. When the CaM kinase II-PSD complex was incubated at 30 degrees C, its Ca2+-independent activity was gradually decreased. This decrease was correlated with dephosphorylation of the kinase and its release from PSD-CaM kinase II complex. These results indicate that CaM kinase II reversibly translocates to PSDs in a phosphorylation-dependent manner.
Collapse
Affiliation(s)
- Y Yoshimura
- Department of Biochemistry, Faculty of Pharmaceutical Sciences, The University of Tokushima, Shomachi 1, Tokushima 770, Japan
| | | |
Collapse
|
198
|
Gotter AL, Kaetzel MA, Dedman JR. A major second messenger mediator of Electrophorus electricus electric tissue is CaM kinase II. COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY. PART A, PHYSIOLOGY 1997; 118:81-91. [PMID: 9243814 DOI: 10.1016/s0300-9629(96)00411-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Electric tissue of the electric eel, Electrophorus electricus, has been used extensively as a model system for the study of excitable membrane biochemistry and electrophysiology. Membrane receptors, ion channels, and ATPases utilized by electrocytes are conserved in mammalian neurons and myocytes. In this study, we show that Ca2+ predominates as the major mediator of electric tissue phosphorylation relative to cyclic AMP and cyclic GMP-induced phosphorylation. Mastoparan, a calmodulin inhibitor peptide, and a peptide corresponding to the pseudosubstrate region of mammalian calmodulin-dependent protein kinase II (CaMKII (281-302)) attenuated Ca(2+)-dependent phosphorylation in a dose-dependent manner. These experiments demonstrated that calmodulin-dependent protein kinase II activity predominates in electric tissue. The Electrophorus kinase was purified by a novel affinity chromatography procedure utilizing Ca2+/calmodulin-dependent binding to the CaMKII (281-302) peptide coupled to Sepharose. The purified 51 kDa calmodulin-dependent protein kinase II demonstrated extensive autophosphorylation and exhibited a 3- to 4-fold increase in Ca(2+)-independent activity following autophosphorylation. Immunofluorescent localization experiments demonstrated calmodulin to be abundant in electrocytes, particularly subjacent to the plasma membrane. Calmodulin-dependent protein kinase II had a punctate distribution indicating that it may be compartmentalized by association with vesicles or the cytoskeleton. As the primary mediator of phosphorylation within electric tissue, CaM kinase II may be critical for the regulation of the specialized electrophysiological function of electrocytes.
Collapse
Affiliation(s)
- A L Gotter
- Department of Molecular and Cellular Physiology, University of Cincinnati College of Medicine, Ohio 45267-0576, USA
| | | | | |
Collapse
|
199
|
Postsynaptic inhibitors of calcium/calmodulin-dependent protein kinase type II block induction but not maintenance of pairing-induced long-term potentiation. J Neurosci 1997. [PMID: 9204920 DOI: 10.1523/jneurosci.17-14-05357.1997] [Citation(s) in RCA: 144] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The role of postsynaptic kinases in the induction and maintenance of long-term potentiation (LTP) was studied in the CA1 region of the rat hippocampal slice. A peptide inhibitor for the catalytic domain of calcium/calmodulin-dependent protein kinase type II (CaM-kinase) was applied through a perfused patch pipette. The inhibitor completely blocked both the short-term potentiation and LTP induced by a pairing protocol. This indicates that the kinase or kinases affected by the peptide are downstream from depolarization in the LTP cascade. The ability to block LTP required that measures be taken to interfere with degradation of the peptide kinase inhibitor by endogenous proteases; either addition of protease inhibitors or modifications of the peptide itself greatly enhanced the effectiveness of the peptide. Protease inhibitors by themselves or control peptide did not block LTP induction. To study the effect of kinase inhibitor on LTP maintenance, we induced LTP in one pathway. Subsequent introduction of the kinase inhibitor blocked the induction of LTP in a second pathway, but it did not affect maintenance of LTP in the first. The implications for the role of kinases in LTP maintenance are discussed.
Collapse
|
200
|
Visualization of the distribution of autophosphorylated calcium/calmodulin-dependent protein kinase II after tetanic stimulation in the CA1 area of the hippocampus. J Neurosci 1997. [PMID: 9204925 DOI: 10.1523/jneurosci.17-14-05416.1997] [Citation(s) in RCA: 168] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Autophosphorylation of calcium/calmodulin-dependent protein kinase II (CaMKII) at threonine-286 produces Ca2+-independent kinase activity and has been proposed to be involved in induction of long-term potentiation by tetanic stimulation in the hippocampus. We have used an immunocytochemical method to visualize and quantify the pattern of autophosphorylation of CaMKII in hippocampal slices after tetanization of the Schaffer collateral pathway. Thirty minutes after tetanic stimulation, autophosphorylated CaM kinase II (P-CaMKII) is significantly increased in area CA1 both in apical dendrites and in pyramidal cell somas. In apical dendrites, this increase is accompanied by an equally significant increase in staining for nonphosphorylated CaM kinase II. Thus, the increase in P-CaMKII appears to be secondary to an increase in the total amount of CaMKII. In neuronal somas, however, the increase in P-CaMKII is not accompanied by an increase in the total amount of CaMKII. We suggest that tetanic stimulation of the Schaffer collateral pathway may induce new synthesis of CaMKII molecules in the apical dendrites, which contain mRNA encoding its alpha-subunit. In neuronal somas, however, tetanic stimulation appears to result in long-lasting increases in P-CaMKII independent of an increase in the total amount of CaMKII. Our findings are consistent with a role for autophosphorylation of CaMKII in the induction and/or maintenance of long-term potentiation, but they indicate that the effects of tetanus on the kinase and its activity are not confined to synapses and may involve induction of new synthesis of kinase in dendrites as well as increases in the level of autophosphorylated kinase.
Collapse
|