Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.11.17 (CaMKII)
 4,029 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Our aim was to visualize the dynamic features of Ca2+/calmodulin-dependent protein kinase II (CaMKII) activity. In order to do so, we synthesized a new reagent by conjugating a fluoroprobe, 6-acryloyl-2-dimethylaminonaphthalene (acrylodan), to syntide 2, a specific peptide substrate for CaMKII. In cell-free conditions, the conjugate was found to be an effective indicator of calmodulin activation by Ca2+ and the subsequent activation of CaMKII. The reagent is cell-permeable and can stain living cells when bath-applied. Using this technique we were able to obtain fluorescence images of stained cells and analyse the dynamic features of CaMKII inside the cells by means of image processing. Regional heterogeneity of CaMKII activation in cultured hippocampal neurones was seen following L-glutamate administration.
 ...
PMID:Imaging of Ca2+/calmodulin-dependent protein kinase II activity in hippocampal neurones. 898 50

Brain synaptic junctions are marked by a prominent dense-staining structure, the postsynaptic density (PSD), embedded in the postsynaptic membrane. Isolated PSDs contain a complex mixture of proteins among which the most abundant are the alpha subunit of calcium/calmodulin-dependent kinase II (CaMK II alpha) the membrane cytoskeletal proteins actin and spectrin and receptors for both excitatory and inhibitory neurotransmitters. We have investigated the relationship of these proteins to the junctional structure by extracting isolated PSDs with lithium diiodosalicylate (LIS). This selectively solubilized actin and spectrin while other prominent PSD proteins, such as CaMK II alpha, the AMPA- and NMDA-type glutamate receptors and GABA receptors, were not extracted at all. Electron microscopy revealed that LIS treatment caused some fragmentation of PSDs but that their basic lattice-like structure remained intact. These observations suggest that PSD structure is organised at two levels; a core component containing CaMK II alpha and neurotransmitter receptors which we have previously described as the postsynaptic junctional lattice and a peripheral actin-associated component that draws the lattice components together into the complete PSD structure.
 ...
PMID:Role of actin in the organisation of brain postsynaptic densities. 903 39

We investigated the involvement of calmodulin and Ca2+/calmodulin-dependent protein kinase II (CaMKII) in the photic entrainment of circadian rhythms using calmodulin inhibitors such as calmidazolium (CMZ) and trifluoperazine (TFP), and a CaMKII inhibitor, KN-62, in rats. Fos expression in the suprachiasmatic nucleus (SCN) of rats induced by photic stimulation (300 lux, 1 h) during the early subjective night of the rats was inhibited by treatment with CMZ (10 mg/kg i.p.) or TFP (20 mg/kg i.p.) 30 min before photic stimulation. With respect to the neuronal firing rate in the rat SCN slice, KN-62 and CMZ application during the early subjective night attenuated the glutamate (10 microM)-induced phase shift. The present results suggest that calmodulin and CaMKII are involved in the photic entrainment mechanism in the rodent SCN.
 ...
PMID:The involvement of calmodulin and Ca2+/calmodulin-dependent protein kinase II in the circadian rhythms controlled by the suprachiasmatic nucleus. 917 55

Long-term depression (LTD) of synaptic strength is induced by glutamate-triggered increases in postsynaptic [Ca2+], through either influx or release from intracellular stores. Induction of LTD has also been reported to require release of Ca2+ from presynaptic stores and activation of presynaptic Ca2+/calmodulin-dependent protein kinase II. This finding leads to the hypothesis that the intercellular messenger nitric oxide (NO) may be a means by which postsynaptic Ca2+ triggers changes expressing LTD in presynaptic terminals. We report that bath application of the oxadiazoloquinoxalone derivative ODQ (4 microM), a selective inhibitor of NO-sensitive guanylyl cyclase (NOGC), markedly attenuated (90%) the magnitude of LTD induced by low-frequency stimulation (LFS; 1 Hz/15 min) of Schaffer collateral-CA1 synapses in hippocampal slices in vitro. Both the NO donor S-nitroso-N-acetylpenicillamine (100 microM) and the membrane-permeant cyclic guanine 3',5'-monophosphate (cGMP) analogue 8-(-4-chlorophenylthio) guanosine (8-pCPT)-cGMP (50 microM) enhanced the magnitude of LTD, which is consistent with he hypothesis that activation of NOGC plays a role in the induction of LTD. Nicotinamide (20 mM), an inhibitor of NO-activated ADP ribosyltransferase, did not impair the induction of LTD. In contrast to de novo LTD, the reversal of long-term potentiation by LFS (depotentiation) was only partially blocked (55%) by ODQ, and heterosynaptic LTD was not impaired at all, suggesting that there are both NOGC-dependent and -independent forms of LTD. Because postsynaptic intracellular infusion of ODQ (500 microM) failed to block the induction of LTD, we conclude that activation of presynaptic NOGC is a necessary step in the induction of an NOGC-dependent component of LTD.
 ...
PMID:Nitric-oxide-guanylyl-cyclase-dependent and -independent components of multiple forms of long-term synaptic depression. 922 26

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.
 ...
PMID:Mechanisms of potentiation by calcium-calmodulin kinase II of postsynaptic sensitivity in rat hippocampal CA1 neurons. 935 18

Aberrant phosphorylation of neurofilaments, similar to that occurring in various motor neuron diseases, is produced in cultured motor neurons by activation of protein kinase C (PKC). Following exposure to synthetic diacylglycerol, persistent change in the phosphorylation state of C-terminal domains of neurofilament proteins was detected by increased perikaryal immunoreactivity with the antibody SMI34; this antibody recognizes NF-M/NF-H when C-terminal KSP repeat domains are highly phosphorylated. SMI34 labeling of perikarya and dendrites was prevented by pretreatment with either the NMDA receptor antagonist APV or by the Ca2+/calmodulin-dependent protein kinase (CaMK) inhibitor KN-62, but not by antagonists of AMPA/kainate or metabotropic glutamate receptors or by inhibitors of arachidonic acid metabolic pathways. Thus, activation of PKC may induce neurofilament phosphorylation in motor neurons by acting in cooperation with stimulation of NMDA receptors and activation of CaMK. These mechanisms may be relevant to motor neuron disease and other neuronal injuries in which increased PKC activity has been measured.
 ...
PMID:Activation of NMDA receptors and Ca2+/calmodulin-dependent protein kinase participate in phosphorylation of neurofilaments induced by protein kinase C. 940 13

Using the patch-clamp technique, we studied the effect of intracellular Ca2+ on Cl- current gated by type A gamma-aminobutyric acid receptors (GABAA) in mouse cortical neurons. When the rapid Ca2+ chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA) was in the pipette solution, the GABA-activated Cl- current amplitude decreased over time to 49 +/- 7% of control. In contrast, equimolar replacement of BAPTA with ethylenebis(oxonitrilo)tetraacetate (EGTA) caused a 60 +/- 10% increase in GABA current. An increased intracellular Ca2+ concentration caused a transient augmentation of the GABA current. This effect of Ca2+ was concentration dependent (10 nM to 34 muM). Ca2+ increased the amplitude of the current by enhancing the maximal response to GABA rather than by changing the affinity of the receptor to GABA (EC50 = 5 +/- 0.4 muM vs. 7 +/- 0.3 muM). Both calmodulin (CaM) and a CaM kinase II inhibitor (200 muM) blocked the potentiating effect of Ca2+ suggesting that it was mediated by activation of CaM kinase II. We found that regulation of GABAA receptors by intracellular Ca2+ in cortical neurons has important physiological implications since the potentiating effect of increasing the intracellular Ca2+ on responses to GABA was mimicked by activating excitatory receptors with 100 muM N-methyl-D-aspartate (NMDA). These findings suggest that modulation of GABAA receptor activity by glutamate may be brought about via changes in intracellular Ca2+.
 ...
PMID:Effects of intracellular calcium on GABAA receptors in mouse cortical neurons. 942 94

GluR2 is the regulatory subunit in the AMPA family of glutamate receptors (GluRs) in that its presence inhibits calcium flux and dominates the current/ voltage characteristics of AMPA receptors. Studies from other laboratories have shown that GABAergic interneurons have a lower ratio of GluR2/GluR1 mRNA than pyramidal cells as well as possessing AMPA receptors that have a higher relative permeability to calcium. We hypothesized that such differences might be related to differences in the subunit stoichiometry at the AMPA synapses in each cell class, and used a GluR2-specific monoclonal antibody in a double-label immunogold protocol with anti-GABA and anti-CaM kinase II to compare the GluR2 representation at asymmetric synapses in GABA neurons to that of pyramidal cells in rat CA1. Virtually all CA1 pyramidal cells as well as the majority of GABAergic interneurons were GluR2 positive. EM immunogold labeling also showed that GABAergic interneurons had distinctive ultrastructural features and contained GluR2 in both their soma and their dendrites, as did the spines and shafts of pyramidal cells. GluR2 immunoreactivity was frequently preferentially located at asymmetric synapses on both pyramidal cell spines and shafts as well as the dendritic processes and soma of GABAergic interneurons. However, the labeled synapses on GABAergic neurons had a significantly lower number of immunogold particles than those on pyramidal cells. In fact, 90% of the labeled asymmetric synapses on GABAergic cells had one to three gold particles, whereas greater than 70% of the labeled asymmetric synapses on pyramidal cells had four or more gold particles associated with the synapse. These data suggest that while both cell classes contain GluR2, they differ in the relative representation of GluR2 at their AMPA synapses, such that GABAergic neurons might possess AMPA receptors with higher calcium permeability on average than pyramidal cells. Such differences in subunit representation at AMPA-receptor-mediated synapses would not only lead to differences in calcium permeability and functional characteristics across these two cell classes, but might also be relevant to the hippocampal patterns of selective vulnerability with respect to excitotoxicity and neurodegeneration.
 ...
PMID:Synaptic distribution of GluR2 in hippocampal GABAergic interneurons and pyramidal cells: a double-label immunogold analysis. 951 19

Findings in vivo and in culture suggest that neuronal activity selectively regulates GABA(A) receptor delta subunit mRNA expression in cerebellar granule neurons. For example, the onset of delta subunit mRNA expression during postnatal maturation coincides with innervation. Furthermore, depolarizing conditions (25 mM KCl) in culture initiate and maintain increases in the delta subunit transcript level. We have now examined whether similar changes in delta subunit mRNA expression occur in cultured neurons after activation of glutamate receptors of the NMDA subtype, an event that mimics granule neuron depolarization by mossy fiber innervation in vivo. Our studies demonstrate that addition of 50 microM NMDA to cultured rat granule neurons maintained in defined, serum-free medium specifically initiates delta subunit transcript expression. Whereas the level of the delta subunit mRNA is increased fourfold by this treatment, levels of other GABA(A) receptor subunit transcripts are not significantly changed. The level of the delta subunit transcript is further increased when NMDA receptor activation is enhanced by maintaining neurons in a Mg2+-free medium to alleviate Mg2+ blockade of the receptor channel. The NMDA-induced elevation in delta subunit transcript expression involves activation of a Ca2+/calmodulin-dependent protein kinase pathway. These findings suggest that activation of an excitatory pathway may regulate the expression of an inhibitory receptor phenotype in cerebellar granule neurons in vivo.
 ...
PMID:NMDA receptor stimulation selectively initiates GABA(A) receptor delta subunit mRNA expression in cultured rat cerebellar granule neurons. 957 74

The distribution of Ca2+/calmodulin-dependent protein kinase II (CaM kinase II) alpha and beta isoforms in the brainstem of adult rats was investigated using an immunohistochemical method with two monoclonal antibodies which specifically recognize the alpha and beta isoform, respectively. We found that these isoforms were differentially expressed by neurons in the substantia nigra, red nucleus, dorsal cochlear nucleus, pontine nuclei and inferior olivary nucleus. Neurons in the inferior olivary nucleus express the alpha isoform, but not the beta isoform. In contrast, neurons in the substantia nigra, red nucleus and pontine nuclei were immunostained with the beta antibody, but not with the alpha antibody. In the dorsal cochlear nucleus, neurons in layers I and II were alpha-immunopositive, whereas neurons in layers III and IV were beta-immunopositive. Therefore, the distribution of the CaM kinase II alpha-immunopositive neurons is completely different from that of CaM kinase II beta-immunopositive neurons. Next we examined the possible coexistence of CaM kinase II alpha isoform and glutamate or that of CaM kinase II beta isoform and glutamic acid decarboxylase (GAD) in the single neuron by double immunofluorescence labelling using a pair of anti-alpha and anti-glutamate antibodies, or a pair of anti-beta and anti-GAD antibodies. The results indicated that neurons expressing anti-alpha immunoreactivity were also immunopositive against anti-glutamate antibody, and neurons expressing beta isoform were also immunopositive against anti-GAD antibody, suggesting that alpha-immunopositive neurons are classified as excitatory-type neurons, and on the contrary, beta-immunopositive neurons are classified as inhibitory-type neurons. In conclusion, the present study confirmed that alpha- and beta-isoforms of CaM kinase II are differentially expressed in the nuclei of the brainstem and have different roles.
 ...
PMID:Regional differences between the immunohistochemical distribution of Ca2+/calmodulin-dependent protein kinase II alpha and beta isoforms in the brainstem of the rat. 959 59


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>