Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.11.13 (protein kinase C)
 49,245 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Synapsin I, a prominent phosphoprotein in nerve terminals, is proposed to modulate exocytosis by interaction with the cytoplasmic surface of small synaptic vesicles and cytoskeletal elements in a phosphorylation-dependent manner. Tetanus toxin (TeTx), a potent inhibitor of neurotransmitter release, attenuated the depolarization-stimulated increase in synapsin I phosphorylation in rat cortical particles and in synaptosomes. TeTx also markedly decreased the translocation of synapsin I from the small synaptic vesicles and the cytoskeleton into the cytosol, on depolarization of synaptosomes. The effect of TeTx on synapsin I phosphorylation was both time and TeTx concentration dependent and required active toxin. One- and two-dimensional peptide maps of synapsin I with V8 proteinase and trypsin, respectively, showed no differences in the relative phosphorylation of peptides for the control and TeTx-treated synaptosomes, suggesting that both the calmodulin- and the cyclic AMP-dependent kinases that label this protein are equally affected. Phosphorylation of synapsin IIb and the B-50 protein (GAP43), a known substrate of protein kinase C, was also inhibited by TeTx. TeTx affected only a limited number of phosphoproteins and the calcium-dependent decrease in dephosphin phosphorylation remained unaffected. In vitro phosphorylation of proteins in lysed synaptosomes was not influenced by prior TeTx treatment of the intact synaptosomes or by the addition of TeTx to lysates, suggesting that the effect of TeTx on protein phosphorylation was indirect. Our data demonstrate that TeTx inhibits neurotransmitter release, the phosphorylation of a select group of phosphoproteins in nerve terminals, and the translocation of synapsin I. These findings contribute to our understanding of the basic mechanism of TeTx action.
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PMID:Tetanus toxin inhibits depolarization-stimulated protein phosphorylation in rat cortical synaptosomes: effect on synapsin I phosphorylation and translocation. 132 20

The olfactory neuroepithelium exhibits neurogenesis throughout adult life, and in response to lesions, a phenomenon that distinguishes this neural tissue from the rest of the mammalian brain. The newly formed primary olfactory neurons elaborate axons into the olfactory bulb. Thus, denervation and subsequent reinnervation of olfactory bulb neurons may occur throughout life. This unique ability of the olfactory neuroepithelium to generate new neurons from a population of precursor cells present in the basal cell layer of this tissue makes it a valuable model in the study of neural development and regeneration. The molecular processes underlying the neurogenic properties of the olfactory neuroepithelium are poorly understood. Here we have reviewed our studies on the expression of B50/GAP43 during ontogeny of the olfactory system and following lesioning. This analysis includes the characterization of the expression of OMP, a protein expressed in mature olfactory neurons, as well as PKC and calmodulin. The latter two molecules are of particular interest to the function of B50/GAP43 since the degree of phosphorylation of B50/GAP43 appears to determine B50/GAP43's ability to bind calmodulin (see also Storm, chapter 4, this volume). In the mature olfactory epithelium B50/GAP43 expression is restricted to a subset of cells located in the basal region. Since the expression of B50/GAP43 is high in developing and regenerating nerve cells we are confident that the B50/GAP43 positive cells are new neurons derived from the stem cells in the basal region of the epithelium. B50/GAP43 is absent from the stem cells themselves and also from the mature OMP-expressing neurons. On the basis of the patterns of B50/GAP43 and OMP expression two stages could be discriminated in the regeneration of the olfactory epithelium. First, as an immediate response to lesioning a large population of B50/GAP43 positive, OMP negative neurons are formed. Subsequently, during the second stage, these newly formed differentiating neurons mature as evidenced by a decrease in B50/GAP43 and an increase in OMP expression. The second stage in the regeneration process is only manifested if the regenerating neurons can reach their target cells in the olfactory bulb. Hence, bulbectomy results in the arrest of the reconstituted olfactory epithelium in an immature state. The differential patterns of B50/GAP43 expression following peripheral lesioning and bulbectomy suggest the existence of a target derived signal molecule involved in the down-regulation of B50/GAP43 expression in olfactory neurons that have established synaptic contacts in the olfactory bulb (see also Willard, chapter 2, this volume, "the suppressor hypothesis").(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Regulation of gene expression in the olfactory neuroepithelium: a neurogenetic matrix. 183 74

Neuromodulin (also called GAP43, G50, F1, pp46), a neural-specific calmodulin binding protein, is a major protein kinase C substrate found in developing and regenerating neurons. Here, we report the immunocytochemical characterization of neuromodulin in cultured 0-2A bipotential glial precursor cells obtained from newborn rat brain. Neuromodulin is also present in oligodendrocytes and type 2 astrocytes (stellate-shaped astrocytes), which are both derived from the bipotential glial 0-2A progenitor cells, but is absent of type 1 astrocytes (flat protoplasmic astrocytes). These results support the hypothesis of a common cell lineage for neurons and bipotential 0-2A progenitor cells and suggest that neuromodulin plays a more general role in plasticity during development of the central nervous system. The expression of neuromodulin in secondary cultures of newborn rat oligodendrocytes and its absence in type 1 astrocytes was confirmed by Northern blot analysis of isolated total RNA from these different types of cells using a cDNA probe for the neuromodulin mRNA and by Western blot analysis of the cell extracts using polyclonal antibodies against neuromodulin. The properties of the neuromodulin protein in cultured oligodendrocytes and neuronal cells have been compared. Although neuromodulin in oligodendrocytes is soluble in 2.5% perchloric acid like the neuronal counterpart it migrates essentially as a single protein spot on two-dimensional gel electrophoresis whereas the neuronal antigen can be resolved into at least three distinct protein spots. To obtain precise alignments of the different neuromodulin spots from these two cell types, oligodendrocyte and neuronal cell extracts were mixed together and run on the same two-dimensional gel electrophoresis system. Oligodendroglial neuromodulin migrates with a pI identical to the basic forms of the neuronal protein in isoelectric focusing gel. However, the glial neuromodulin shows a slightly lower mobility in the second dimensional lithium dodecyl sulfate-PAGE than its neuronal counterpart. As measured by 32Pi incorporation, neuromodulin phosphorylation in oligodendrocytes is dramatically increased after short-term phorbol ester treatments, which activate protein kinase C, and is totally inhibited by long-term phorbol ester treatments, which downregulates protein kinase C, thus confirming its probable specific in vivo phosphorylation by protein kinase C. In primary cultures of neuronal cells, two of the three neuromodulin spots were observed to be phosphorylated with an apparent preferential phosphorylation of the more acid forms.
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PMID:Neuromodulin (GAP43): a neuronal protein kinase C substrate is also present in 0-2A glial cell lineage. Characterization of neuromodulin in secondary cultures of oligodendrocytes and comparison with the neuronal antigen. 217 Apr 23

To determine changes in the degree of phosphorylation of the protein kinase C substrate B-50 in vivo, a quantitative immunoprecipitation assay for B-50 (GAP43, F1, pp46) was developed. B-50 was phosphorylated in intact hippocampal slices with 32Pi or in synaptosomal plasma membranes with [gamma-32P]ATP. Phosphorylated B-50 was immunoprecipitated from slice homogenates or synaptosomal plasma membranes using polyclonal anti-B-50 antiserum. Proteins in the immunoprecipitate were separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and the incorporation of 32P into B-50 was quantified by densitometric scanning of the autoradiogram. Only a single 48-kilodalton phosphoband was detectable in the immunoprecipitate, but this band was absent when preimmune serum was used. The B-50 immunoprecipitation assay was quantitative under the following condition chosen, as (1) recovery of purified 32P-labelled B-50 added to slice homogenates or synaptosomal plasma membranes was greater than 95%; and (2) modulation of B-50 phosphorylation in synaptosomal plasma membranes with adrenocorticotrophic hormone, polymyxin B, or purified protein kinase C in the presence of phorbol diester resulted in EC50 values identical to those obtained without immunoprecipitation. With this immunoprecipitation assay we found that treatment of hippocampal slices with 4 beta-phorbol 12,13-dibutyrate stimulated B-50 phosphorylation, whereas 4 alpha-phorbol 12,13-didecanoate was inactive. Thus, we conclude that the B-50 immunoprecipitation assay is suitable to monitor changes in B-50 phosphorylation in intact neuronal tissue.
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PMID:Determination of changes in the phosphorylation state of the neuron-specific protein kinase C substrate B-50 (GAP43) by quantitative immunoprecipitation. 252 Nov 82

Although such solubility is uncommon among proteins generally, several bovine brain proteins were found to be soluble in 2.5% perchloric acid, and many of them were in vitro substrates for protein kinase C (Ca2+/phospholipid-dependent enzyme). Two of the perchloric acid-soluble brain proteins were purified, p43 and p17. P43 and p17 could be phosphorylated by protein kinase C only in the presence of Ca2+ and phospholipids and neither was a substrate for protein kinase II. P43 was subsequently identified as the neurospecific, calmodulin-binding protein, neuromodulin (also designated P-57, GAP43, B50, or F1) (Alexander, K. H., Wakim, B. T., Doyle, G. S., Walsh, K. A., and Storm, D. R. (1988) J. Biol. Chem. 263, 7544-7549). A rapid purification method for neuromodulin was developed taking advantage of its newly discovered property, solubility in 2.5% perchloric acid, and of its previously recognized calmodulin-binding property. Evidence was obtained that neuromodulin isolated from cytosolic extract exists as a mixture of molecular forms and that the Ca2+-binding S100 protein-beta discriminates among the different neuromodulin isoforms in forming covalent complexes via disulfide bridges; this discrimination may be explained by analogous differences observed between the NH2-terminal amino acid sequences of p57 and F1. Solubility in 2.5% perchloric acid was demonstrated for another rat brain protein kinase C substrate, p87. We suggest that perchloric acid solubility might be a common property of protein kinase C substrates.
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PMID:Protein kinase C substrates from bovine brain. Purification and characterization of neuromodulin, a neuron-specific calmodulin-binding protein. 252 87

Activation of protein kinase C (PKC) facilitates long-term potentiation (LTP), a model of memory, and increases its substrate protein F1 (aka GAP43) phosphorylation in direct relation to synaptic enhancement. Unsaturated fatty acids (c-FAs) which activate purified PKC, when injected into hippocampus, enhance LTP. To determine if dietary c-FAs could alter memory itself as well as brain PKC substrate (F1) metabolism, rats were maintained for 10 weeks on fatty acid diets enriched in mono-unsaturated oleic acid (OA; 20% olive oil, w/w), or a mono- and di-unsaturated mixture of oleate/linoleate (O/L; 20% corn oil), or a saturated fatty acid diet of laurate/myristate (L/M; 20% hydrogenated coconut oil). The O/L diet group was superior to the OA and L/M groups in spatial memory performance after the first two weeks of acquisition and in later achievement of criterion performance. The O/L diet had a significantly higher hippocampal protein F1 in vitro phosphorylation than in both the OA and L/M in trained and non-trained animals. Significantly, animals that made fewer errors showed higher F1 phosphorylation (r = -0.70). Diet both increases brain PKC substrate phosphorylation and enhances maze learning, confirming the feasibility of enhancing learning and memory by dietary regimens derived from basic neurochemical studies of synaptic plasticity.
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PMID:Dietary cis-fatty acids that increase protein F1 phosphorylation enhance spatial memory. 259 47

The neuron-specific phosphoprotein B-50 (Mr 48 kDa, isoelectric point, IEP, 4.5), which is identical to GAP43, is a member of a family of growth-associated proteins. Protein B-50 is a major phosphoprotein in nerve growth cones isolated from fetal rat brain. In a growth cone particulate fraction (GCp), endogenous B-50 phosphorylation is Ca2+-dependent and is unaffected by cAMP. Addition of purified protein kinase C (PKC) to GCP enhances B-50 phosphorylation. In heat-inactivated GCp, B-50 is one of the major substrates of purified PKC. Endogenous B-50 phosphorylation in GCP is stimulated in a dose-dependent manner by 4 beta-phorbol diesters, known to activate PKC, but not by the inactive 4 alpha-phorbol derivatives. In synaptic plasma membranes (SPM) isolated from adult rat brain, the degree of B-50 phosphorylation has been implicated in the modulation of receptor-mediated polyphosphoinositide (PPI) hydrolysis. In addition to B-50 and its kinase, PKC, the GCp fraction was also shown to contain all other components of such a modulatory system: the phosphatidylinositol 4-phosphate (PIP)-kinase, as shown on Western blots with affinity-purified IgGs against PIP-kinase, and the polyphosphoinosides, PIP and phosphatidylinositol 4,5-bisphosphate (PIP2), since the addition of gamma-32P-ATP to the GCp fraction not only results in B-50 phosphorylation but also in the labeling of phosphatidic acid (PA), PIP, and PIP2. ACTH1-24, which inhibits B-50 phosphorylation in the GCp fraction in a dose-dependent manner (IC50 = 5 x 10(-6) M), stimulates PIP2 labeling dose-dependently in the same preparation.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:B-50 phosphorylation and polyphosphoinositide metabolism in nerve growth cone membranes. 283 51

There is substantial evidence that protein kinases, through the phosphorylation of substrate proteins, play a significant role in information processing in the brain, including processes underlying memory formation. Inhibition of the activity of the cyclic-adenosine monophosphate-dependent protein kinase A by the highly specific inhibitor, halofantrine, resulted in impairment of memory formation in day-old chicks trained on a single-trial passive avoidance task. A dose of 9.6 ng/chick halofantrine induced amnesia at the beginning of a protein synthesis-dependent long-term memory stage, the last of three stages of memory postulated to underly memory formation in the chick following passive avoidance learning. The concentration of halofantrine required for 50% inhibition of chick brain protein kinase A was found to be similar to that observed for bovine heart and rat liver. The amnestic effect of halofantrine is tentatively attributed to interference with de novo protein synthesis necessary for long-term memory consolidation. Neither anthraquinone nor the anthraquinone derivative anthraflavic acid, which have little effect on protein kinase A activity, affected memory retention. On the other hand, two other anthraquinone derivatives, chrysophanic acid and purpurin, which inhibit PKA activity, at doses of 0.25 and 0.5 ng/chick also yielded retention deficits. In these cases, however, retention losses occurred earlier than observed with halofantrine, at about 30 min post-training. The earlier effects of these inhibitors may be due to the additional inhibitory action of these compounds on protein kinase C activity, which has been demonstrated in previous studies to be implicated, possibly through phosphorylation of the GAP43 phosphoprotein, in memory processing in the stage of memory immediately preceding the protein synthesis-dependent long-term stage.
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PMID:Inhibitors of cAMP-dependent protein kinase impair long-term memory formation in day-old chicks. 758 18

Protein F1/GAP43 is neuron-specific, associated with neurite outgrowth during development and a substrate for PKC. This protein is present in high levels in serotonergic neurons which in culture sprout in response to the glial-derived S100b, the beta-beta homodimer. As an initial step in determining whether S100b acts on F1/GAP43 we studied the regulation by S100b of PKC phosphorylation of F1/GAP43. Either the S100b or a mixture of S100a and S100b, both from a brain glial cell source, inhibited in vitro phosphorylation of purified F1/GAP43 by purified PKC in a dose-dependent manner. Using recombinant PKC subtypes, purified S100b preferentially inhibited the F1/GAP43 phosphorylation by the beta subtype. The IC50 of S100b for beta I and beta II PKC was 8 microM while for alpha and gamma PKC it was 64 microM. S100b inhibition was thus subtype-selective. Histone III-S phosphorylation by the four PKC subtypes was not inhibited by S100b. S100b inhibition was thus substrate-selective. Moreover, the effect of S100b on phosphorylation could not be explained by a direct inhibition of kinase activity. Together with earlier studies implicating a role for S100 in synaptic plasticity and neurite outgrowth, the present results suggest that S100b may regulate such functions through its inhibition of neuron-specific PKC substrate (F1/GAP43) phosphorylation. The regulation of this neuron-specific substrate phosphorylation by glial S100 suggests the potential for a novel neuro-glial interaction. Finally, the location of S100 gene on chromosome 21, trisomic in Down's syndrome, and over-expressed in this disorder, as well as in Alzheimer's disease, suggests a link to cognitive impairments in human.
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PMID:Glial-derived S100b protein selectively inhibits recombinant beta protein kinase C (PKC) phosphorylation of neuron-specific protein F1/GAP43. 816 23

A compromise or deregulation in signal transduction cascades could adversely affect cellular functions and possibly contribute to cell death. In recent years, it has become increasingly apparent that pronounced activation of neuronal signal transduction systems is a characteristic of AD brain. There is evidence that signal transduction systems play a role in the formation or development of these pathological features of AD. Aberrant activity and localization of components of signaling mechanisms (growth factors, their receptors, protein kinases, phosphoprotein phosphatases, and phosphoproteins) are closely associated with the intracellular accumulation of PHF, the extracellular deposition of amyloid, and the formation of neuritic plaques in AD brain. In particular, immunohistochemical studies reveal increased levels of neuronal staining for APP, possibly an important growth factor in AD, both in frontal cortex and hippocampus. Anti-APP immunostaining is also associated with the neuritic component of plaques. Additionally, PKC(beta II) immunostaining is increased in the neuronal cell body and neuropil of AD samples, particularly in association with plaques, suggesting a postsynaptic involvement of this enzyme. On the other hand, PKC(beta I) immunostaining is associated with axonal staining particularly in the sprouting neurites of plaques. Sprouting neuritic components of plaques are immunopositive with other growth-associated proteins, such as GAP43, MARCKS, and spectrin. Immunoreactivity of other members of signal transduction systems such as Fos and stathmin are all increased in AD hippocampal neurons. On the other hand, several protein kinases and phosphoproteins were immunolocalized to tangles. Thus, the hyperactivation and dysfunction of signal transduction systems could be involved in the pathogenesis of AD.
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PMID:Hyperactivation of signal transduction systems in Alzheimer's disease. 823 9


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