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)

Three distinct isozymes of a type II calcium/calmodulin-dependent protein kinase (CaM kinase II) from rat forebrain cytosol were separated using S-Sepharose cation-exchange resin. About 90% of the applied kinase activity was recovered in three protein peaks. Each isozymic form of the kinase was purified 200-300 fold by chromatography on S-Sepharose, calmodulin-affinity and gel filtration resins. All 3 forms of CaM kinase II had apparent molecular masses of 650-700 kDa, but contained variable proportions of 50 kDa and 58-60 kDa subunits. The molar ratios of the 50 kDa/58-60 kDa kinase subunits in each holoenzyme were determined by protein staining and [125I]calmodulin-binding studies and were approximately: 6/1, 3/1 and 1/1. The isozyme containing a 3/1 ratio of subunits corresponds to the predominant form of CaM kinase II in forebrain representing 70-80% of the total activity in cytosol, whereas the other forms each represent 5-10% of the total cytosolic activity. The substrate specificities and time courses of substrate phosphorylation for the isozymes were comparable. These studies provide a basis to examine regional, subcellular, and developmental differences in the isozymic forms of CaM kinase II which may subserve different neuronal functions.
 ...
PMID:Separation of isozymic forms of type II calcium/calmodulin-dependent protein kinase using cation-exchange chromatography. 255 71

Studies in the past several years have provided direct evidence that protein phosphorylation is involved in the regulation of neuronal function. Electrophysiological experiments have demonstrated that three distinct classes of protein kinases, i.e., cyclic AMP-dependent protein kinase, protein kinase C, and CaM kinase II, modulate physiological processes in neurons. Cyclic AMP-dependent protein kinase and kinase C have been shown to modify potassium and calcium channels, and CaM kinase II has been shown to enhance neurotransmitter release. A large number of substrates for these protein kinases have been found in neurons. In some cases (e.g., tyrosine hydroxylase, acetylcholine receptor, sodium channel) these proteins have a known function, whereas most of these proteins (e.g., synapsin I) had no known function when they were first identified as phosphoproteins. In the case of synapsin I, evidence now suggests that it regulates neurotransmitter release. These studies of synapsin I suggest that the characterization of previously unknown neuronal phosphoproteins will lead to the elucidation of previously unknown regulatory processes in neurons.
 ...
PMID:Protein phosphorylation and neuronal function. 258 86

Calcium- and calmodulin-dependent protein kinase activity was studied in pure neuronal and glial cultures. The addition of calcium and calmodulin stimulated 32P incorporation into several neuronal proteins including two in the 50- and 60-kilodalton (kD) region which comigrated with purified forebrain calmodulin kinase II subunits (CaM kinase II). In mature astrocytes, CaM kinase activity was also present, and was inhibited by trifluoroperazine and diazepam. Again in homogenates of these cells, two phosphoproteins of apparent molecular masses of 50 and 60 kD comigrated with purified CaM kinase. CaM kinase activity was absent in immature mixed glia and oligodendrocytes. The presence of CaM kinase in neurons and mature astrocytes was confirmed using monoclonal antibodies specific for the 50-kD subunit of the enzyme. No immunoreactivity was observed in oligodendrocytes. The presence of CaM kinase in astrocytes suggests a more ubiquitous role of this enzyme in regulating cellular processes than was previously recognized.
 ...
PMID:Calmodulin kinase II in pure cultured astrocytes. 282 89

A type II calmodulin-dependent protein kinase (CaM kinase II) has been characterized in the synaptic region and may mediate some of the effects of Ca2+ on neuronal excitability. The activity of CaM kinase II is inhibited by anticonvulsant compounds and may be the molecular basis of their neuro-modulatory effects. The direct injection of purified CaM kinase II into invertebrate neurons has demonstrated that this kinase can directly alter specific ion conductances and neuronal activity. A long-lasting decrease in CaM kinase II activity is associated with septal kindling, an experimental model of epilepsy and long-term memory. In summary, CaM kinase II appears to be a central mediator of the effects of Ca2+ on neuronal function. Further investigation of this enzyme and its effects on neuronal activity may provide a molecular insight into an endogenous mechanism for modulating some of the effects of Ca2+ on neuronal excitability and may increase our understanding of the complex regulatory mechanisms that underlie the pathogenesis of seizure discharge and its regulation by anticonvulsant compounds.
 ...
PMID:Molecular mechanisms of neuronal excitability: possible involvement of CaM kinase II in seizure activity. 282 86

A calcium/calmodulin-dependent protein kinase was partially purified from mouse brain cytosol and compared to a type II calcium/calmodulin-dependent protein kinase (CaM kinase II) previously purified from rat brain. The purification (approximately 200-fold) was followed by the ability of the kinase to phosphorylate the high molecular weight microtubule-associated protein, MAP-2. Approximately 40% of the mouse brain kinase was soluble, and it contained two subunits of 50 kD and 58-60 kD. Both subunits bound [125I]calmodulin in a calcium-dependent manner and demonstrated calmodulin-dependent autophosphorylation. The subunits from whole brain were present in a molar ratio of 3/1. The apparent Km values of the kinase for ATP and calmodulin were 17 microM and 55 nM respectively. The time course, substrate specificity, and subunit phosphopeptide maps were comparable to CaM kinase II from rat brain. Regional distribution studies indicate that the enzyme activity was enriched in hippocampus, cerebral cortex and corpus striatum, whereas activity in cerebellum and pons/medulla was approximately 10-fold lower. All of these characteristics were shared with the rat brain enzyme, indicating that the kinase in mouse brain was a type II calcium/calmodulin-dependent kinase. The mouse may be useful for examining the neuronal localization of CaM kinase II in different brain regions, since this model offers a variety of genetic mutants with well-defined lesions in specific neuronal populations.
 ...
PMID:Identification and regional distribution of a type II calcium/calmodulin-dependent kinase in mouse brain. 283 92

During pre- and postnatal development the dopamine-containing nigrostriatal afferents of the striatum are arranged as a conspicuous series of patches (the "dopamine islands"). The development of this dopamine island system, which metamorphoses in early postnatal life to the striosomal architecture of the adult, has recently received considerable attention, but the factors initiating and influencing maturation of this architecture are largely unknown. In an attempt to clarify the relationships between the onset of clustering of dopamine-containing afferents, the grouping of neurons within future striosomes and the maturation of synapses in the striatum, we compared the initial prenatal appearance and subsequent development of immunohistochemical markers for the dopamine-containing innervation [tyrosine hydroxylase (TH)-like immunoreactivity], for synaptic vesicles (SV48-like immunoreactivity), and for a phosphorylation-related enzyme Ca2+/calmodulin-dependent protein kinase type II (CaM kinase II-like immunoreactivity) that is expressed in virtually all striatal neurons by adulthood. Here we present evidence that during striatal ontogeny, both neurons and neuropil expressing CaM kinase II-like immunoreactivity and SV48-positive terminals form discrete patches that are in register with dopamine islands. It is CaM kinase II-positive elements, however, rather than the TH-positive island fibers (or SV48-positive synapses), that initially form overt clusters. Dopamine-containing fibers begin to innervate the striatal anlage just prior to embryonic day (E) 32. Their distribution follows the general lateral to medial developmental gradient characteristic of the striatum but is not yet distinctly islandic. At this time, CaM kinase II-like immunoreactivity was very weak or not present at all and SV48-like immunoreactivity was undetectable. By E36, CaM kinase II-positive neurons are visible in discrete patches of immunopositive neuropil, but only faint inhomogeneities are detectable in the distribution of TH-positive fibers and scarcely any SV48-like immunoreactivity can be seen. By E45, all 3 markers are focused in typical islandic patterns, and they remain so into the early postnatal period. These observations suggest a developmental sequence in which dopamine-containing fibers invade the striatal anlage prior to forming distinct islandic foci and prior to the maturational events signaled by the production of CaM kinase II within the neurons and neuropil of future striosomes.(ABSTRACT TRUNCATED AT 400 WORDS)
 ...
PMID:Expression of calcium/calmodulin-dependent protein kinase in relation to dopamine islands and synaptic maturation in the cat striatum. 284 20

The autophosphorylation of purified Ca2+/calmodulin-dependent protein kinase II (Ca2+/CaM kinase II) on a threonine-containing phosphopeptide common to both the alpha and beta subunits was previously shown to convert this enzyme into a catalytically active Ca2+-independent species. We now have examined the phosphorylation and activation of Ca2+/CaM kinase II in synaptosomes, a Ca2+-dependent neurosecretory system consisting of isolated nerve terminals. Synaptosomes were prelabeled with 32Pi and the alpha subunit of Ca2+/CaM kinase II was immunoprecipitated. Under basal incubation conditions the alpha subunit was phosphorylated. Depolarization of synaptosomes produced a rapid (2-5 s) Ca2+-dependent increase of about 50% in the state of phosphorylation of the alpha subunit. This was followed by a slower increase in the 32P content of the alpha subunit over the next 5 min of depolarization. The enhanced phosphorylation was characterized by an initial rise (2 s) and subsequent decrease (30 s) in the phosphothreonine content of the alpha subunit. In contrast, the phosphoserine content of the alpha subunit slowly increased during the course of depolarization. Thermolytic two-dimensional phosphopeptide maps of the alpha subunit demonstrated that depolarization stimulated the labeling of a phosphopeptide associated with autoactivation. In parallel experiments, unlabeled synaptosomes were depolarized, and lysates of these synaptosomes were assayed for Ca2+/CaM kinase II activity. Depolarization produced a rapid (less than or equal to 2 s) increase in Ca2+-independent Ca2+/CaM kinase II activity. This activity returned to basal levels by 60 s. Thus, depolarization of intact synaptosomes is associated with the transient phosphorylation of Ca2+/CaM kinase II on threonine residues, presumably involving an autophosphorylation mechanism and concomitantly the transient generation of the Ca2+-independent form of Ca2+/CaM kinase II.
 ...
PMID:Autophosphorylation and activation of Ca2+/calmodulin-dependent protein kinase II in intact nerve terminals. 284 57

Microtubule-associated protein 2 (MAP2) is an excellent substrate for both cyclic-AMP (cAMP)-dependent and Ca2+/calmodulin-dependent kinases. A recently purified cytosolic Ca2+/calmodulin-dependent kinase (now designated CaM kinase II) phosphorylates MAP2 as a major substrate. We now report that microtubule-associated cAMP-dependent and calmodulin-dependent protein kinases phosphorylate MAP2 on separate sites. Tryptic phosphopeptide digestion and two-dimensional phosphopeptide mapping revealed 11 major peptides phosphorylated by microtubule-associated cAMP-dependent kinase and five major peptide species phosphorylated by calmodulin-dependent kinase. All 11 of the cAMP-dependently phosphorylated peptides were phosphorylated on serine residues, whereas four of five major peptides phosphorylated by the calmodulin-dependent kinase were phosphorylated on threonine. Only one peptide spot phosphorylated by both kinases was indistinguishable by both migration and phosphoamino acid site. The results indicate that cAMP-dependent and calmodulin-dependent kinases may regulate microtubule and cytoskeletal dynamics by phosphorylation of MAP2 at distinct sites.
 ...
PMID:Phosphorylation of microtubule-associated protein 2 at distinct sites by calmodulin-dependent and cyclic-AMP-dependent kinases. 299 17

Polyclonal antibodies against Ca2+/calmodulin-dependent protein kinase II (CaM kinase II) of rat brain were prepared by immunizing rabbits and then purified by antigen-affinity column. The antibodies which recognized both subunits of the enzyme with Mrs 49K and 60K were used for the study on the distribution of CaM kinase II in formalin-fixed, paraffin-embedded tissues. In the brain, a light-microscopic study demonstrated strong immunoreactivity in neuronal somata and dendrites and weak immunoreactivity in nuclei. The densely stained regions included cerebral cortex, hippocampal formation, striatum, substantia nigra, and cerebellar cortex. In substantia nigra, neurites were stained, but not neuronal somata. Electron microscopy revealed that the immunoreactive product was highly concentrated at the postsynaptic densities. In addition to neurons, weak immunoreactivity was also demonstrated in glial cells, such as astrocytes and ependymal cells of ventricles and epithelial cells of choroid plexus. In other tissues, strong immunoreactivity was observed in the islet of pancreas and moderate immunoreactivity in skeletal muscle and kidney tubules. Immunoreactivity was demonstrated in all of the tissues tested. The results suggest that CaM kinase II is widely distributed in the tissues.
 ...
PMID:Immunohistochemical localization of Ca2+/calmodulin-dependent protein kinase II in rat brain and various tissues. 304 16

Calmodulin-dependent protein kinase II (CaM kinase II) is associated with microtubule preparations and phosphorylates several endogenous proteins including microtubule-associated protein 2, tubulin, and an 80,000-dalton protein doublet (pp80). We now report that pp80 is identical to synapsin I by all criteria studied including molecular weight, isoelectric point, phosphopeptide mapping of cAMP- and calmodulin-dependent phosphorylated protein, comigration with authentic synapsin I, and sensitivity to digestion with collagenase. Synapsin I and CaM kinase II were found in association with both microtubule preparations and preparations enriched in neurofilaments. Antibodies to synapsin I specifically labeled neurofilaments prepared in vitro. Immunocytochemical studies on rat brain tissue demonstrated synapsin I immunoreactivity specifically associated with the neuronal cytoskeleton as well as synaptic vesicles. The observed synapsin I staining on cytoskeletal elements was considerably diminished or abolished by the inclusion of Triton X-100 in the staining solutions. These results indicate that synapsin I is associated with the cytoskeleton and may be an important link between cytoskeletal elements as well as between the cytoskeleton and membrane.
 ...
PMID:Association of synapsin I with neuronal cytoskeleton. Identification in cytoskeletal preparations in vitro and immunocytochemical localization in brain of synapsin I. 308 74


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