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)

K-252 compounds, which share a common polyaromatic aglycon structure, are rather general and potent inhibitors of various protein kinases, including protein kinase C and tyrosine-specific protein kinases, and possibly act by interfering at or near the ATP binding site. However, chemical modifications in their sugar moiety can result in high specificity of the inhibitory action and, furthermore, can induce other stimulatory and inhibitory effects on nerve cells. These compounds are of particular interest because, in intact cells, they inhibit the actions of NGF and other neurotrophins without diminishing comparable actions of other growth factors. This effect seems to reflect a direct inhibitory action on trk neurotrophin receptor proteins. At concentrations lower than those necessary to inhibit neurotrophin actions, K-252a and K-252b have been shown to potentiate the stimulatory effects of NT-3 on different neurons in culture and on PC12 cells. The structural requirements for this effect seem to be different from those for the inhibition of neurotrophin actions. These findings raise the possibility of development of compounds of high selectivity, able to inhibit or potentiate the transduction mechanisms of individual neurotrophins, and identify K-252a and K-252b as lead compounds for the development of such selective molecules. Specific inhibitors and stimulators of neurotrophins would be valuable tools to investigate biological functions of the neurotrophins in vitro and in vivo. Furthermore, it is possible that, in the future, highly selective drugs with agonistic or antagonistic actions on neurotrophin mechanisms could become therapeutically useful in the treatment of neurological disease and injury.
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PMID:K-252 compounds: modulators of neurotrophin signal transduction. 143 89

Both IGF-I and IGF-II peptides have been localized to specific brain regions. The distribution of IGF-I is homogeneous whereas IGF-II appears to be more local. Two species of IGF receptors are found in the CNS. The type II (m6P) is similar to that in the periphery, but the type I has nearly the same affinity for IGF-I and IGF-II. IGF-I has now been shown to provide cell growth and survival as well as stimulate neurite outgrowth. Dorsal root ganglia and sympathetic neurons are sensitive to IGF-II and the action may be additive with NGF. Cells other than neurites, such as oligodendrocytes respond to the IGFs as well as primary and transformed lines. The mechanism of action has not been resolved but IDG-II appears to act via G-protein coupled activation of protein kinase C. Interaction between various growth factors and the IGFs may be due to up or down-regulation of the receptor predicated by the non-homologous peptide.
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PMID:The effects of IGF-I and IGF-II on cell growth and differentiation in the central nervous system. 144 82

We have previously shown that after peripheral nerve lesion the synthesis of NGF is induced in cells of the nerve sheath (Heumann et al., 1987a). Further analysis led to the identification of growth factors and intracellular mechanisms responsible for this induction in sciatic fibroblasts (Lindholm et al., 1988; Hengerer et al., 1990). The present work aimed at the elucidation of the regulation of NGF synthesis in Schwann cells. A variety of cytokines and peptide growth factors, including interleukin-1 (IL-1) and platelet-derived growth factor (PDGF), which are known to increase NGF-mRNA in fibroblasts and astrocytes, failed to do so in Schwann cell cultures. Forskolin (FK), an activator of adenylate cyclase, increased the level of NGF-mRNA eightfold within 3 hr of incubation. The effect of FK on NGF-mRNA was mimicked by analogs of cAMP but not by dideoxyforskolin, an FK derivative not activating adenylate cyclase. Application of norepinephrine and isoproterenol also augmented the NGF-mRNA content. Pretreatment of Schwann cells with N-[2-(methylamino)ethyl]-5-isoquinoline sulfonamide dihydrochloride (H-8), an inhibitor of cyclic-nucleotide-dependent protein kinases, decreased both basal and elevated levels of NGF-mRNA. Ionomycin, a Ca2+ ionophore, and phorbol 12-myristate 13-acetate (TPA), an activator of protein kinase C, potentiated the effect of FK in an H-8-sensitive manner. We show that the action of FK is independent of changes in mRNA stability and of protein synthesis. Thus, in cultured Schwann cells upregulation of NGF-mRNA expression seems to be mainly achieved by a cAMP-triggered transcriptional activation of the NGF gene. Another striking difference between various glial cell types was revealed by application of transforming growth factor beta-1 (TGF-beta 1), which is the strongest inducer of NGF-mRNA in cultured astrocytes (Lindholm et al., 1990). Schwann cells responded to TGF-beta 1 by decreasing basal as well as FK-induced NGF-mRNA levels. Together with previously published work, our results show that cell-type-specific mechanisms not only account for the different control of NGF expression in neurons as compared to glial cells, but also reveal a surprising specificity of regulatory mechanisms in different non-neuronal cell types, even those derived from the same tissue such as fibroblasts and Schwann cells of peripheral nerves.
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PMID:Cell-type-specific regulation of nerve growth factor (NGF) synthesis in non-neuronal cells: comparison of Schwann cells with other cell types. 165 45

Agents that activate cAMP-dependent protein kinase (PKA) as well as agents that increase intracellular calcium induce the expression of certain immediate early genes (IEGs). Recently, it has been demonstrated that the same cis-acting element in the 5' region of the c-fos gene has the ability to mediate both cAMP- and calcium-induced c-fos expression in PC12 cells (Sheng, M., McFadden, G., and Greenberg, M. (1990) Neuron 4, 571-582). Here we demonstrate that both cAMP- and calcium-mediated induction of c-fos and egr1 are dependent on PKA activity. Addition of either depolarizing concentrations of KCl or the calcium ionophore, ionomycin, to PC12 cells increased the expression of both c-fos and egr1, but these inductions were dramatically reduced in three PKA-deficient cell lines, 123.7, AB.11, and A126-1B2. Furthermore, pretreatment of PC12 cells with 20 microM H89, a specific inhibitor of PKA, inhibited forskolin, dibutyryl cAMP, and KCl-induced c-fos and egr1 induction, while having no effect on NGF induction. Likewise, in the PKA-deficient cells, NGF or an activator of protein kinase C induced c-fos and egr1 normally. To determine if PKA deficiency modifies the ability of Ca2+ to activate calcium-dependent kinases, autophosphorylation of multifunctional Ca2+/calmodulin-dependent protein kinase (CaM kinase) in response to Ca2+ influx was determined. In parental PC12 cells, PC12 cells pretreated with H89, and PKA-deficient cell lines, CaM kinase was activated equivalently in response to KCl depolarization. These results suggest that PKA is not required for Ca(2+)-induced increase in CaM kinase activity and that the induction of IEGs in response to Ca2+ influx is PKA-dependent. Thus, the requirement for PKA resides at a point distal to the activation of calmodulin-dependent processes.
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PMID:Induction of immediate early genes by Ca2+ influx requires cAMP-dependent protein kinase in PC12 cells. 191 45

Local application of sphingosine (1-10 microM), an inhibitor of protein kinase C, to NGF-supplied, distal neurites of rat sympathetic neurons in compartmented cultures caused their retraction and/or degeneration within 24 hr. This effect was specific for distal neurites because sphingosine (even at 100 microM) applied to cell bodies and/or proximal neurites did not destroy these regions of the cells, and their distal neurites continued to elongate. However, effects of other agents suggest that the retraction/degeneration observed in distal neurites directly exposed to sphingosine is not mediated by inhibition of protein kinase C: application of staurosporine, another inhibitor of protein kinase C, to distal neurites did not cause retraction or degeneration; treatment of neurons for 24 or more hours with 2 microM phorbol 12-myristate 13-acetate (PMA), used to downregulate protein kinase C activity, slowed neurite extension about 50%, but did not cause degeneration; and neurons pretreated with PMA still displayed retraction/degeneration of neurites when they were subsequently exposed to sphingosine. Also, replacement of NGF supplied to distal neurites with anti-NGF IgG did not cause retraction/degeneration of neurites within 1 d, suggesting that the effect of sphingosine did not arise by interference with the action of NGF. The specificity of the sphingosine-induced retraction/degeneration for distal neurites suggests that this effect operates via specific mechanisms in distal neurites that can trigger their retraction/degeneration. Such mechanisms could play important roles in nerve growth inhibition, nerve fiber retraction, and degeneration that occur normally in the nervous system and in response to injury and disease. Also, the ability of neurites to grow in the presence of PMA suggests that neurite growth is not dependent upon the activity of protein kinase C. However, the reduced rate of neurite extension in the presence of PMA suggests that chronic PMA treatment may affect mechanism(s) that can modulate neurite growth.
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PMID:Effects of sphingosine, staurosporine, and phorbol ester on neurites of rat sympathetic neurons growing in compartmented cultures. 201 Aug 8

We investigated the intracellular signals underlying the neurotrophic response of adult bovine chromaffin cells to histamine and basic fibroblast growth factor (bFGF). Histamine produced significant neurite outgrowth within 48 hr, whereas the response to bFGF developed after 1 week. H7, a protein kinase C (PKC) inhibitor potentiated both the histamine and the bFGF responses, while another PKC antagonist, staurosporine, induced a rapid and efficient differentiation response when applied alone. These observations suggest that basal PKC activity is required for stabilization of the endocrine phenotype in these cells. They contrast with findings on NGF induction of neurite outgrowth in PC12 cells where PKC promotes differentiation, apparently by activating the fos/jun complex. Thus, we examined the role of c-fos in our model. Both histamine and bFGF induced c-fos gene expression transiently. To determine whether increased levels of c-fos oncoprotein were essential to the differentiation process, we used a hybrid arrest approach employing an innovative transfection technique applicable to primary culture systems. Transfection with plasmid pSVsof, producing antisense c-fos mRNA, reduced c-fos oncoprotein levels but did not diminish histamine-induced neurite outgrowth. We infer that histamine-induced differentiation in bovine chromaffin cells is independent of increased levels of c-fos oncoprotein.
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PMID:Differentiation to a neuronal phenotype in bovine chromaffin cells is repressed by protein kinase C and is not dependent on c-fos oncoproteins. 211 38

We have studied factors controlling message levels for the neuronal growth- and plasticity-associated protein, GAP-43. Following exposure of PC12 cells to various effectors, cytoplasmic RNA was isolated and analyzed by Northern transfer and autoradiography using a GAP-43 cDNA probe. Induction by NGF is apparent after 3 hr exposure and reaches maximal levels at 24 hr. Beyond 24 hr, levels remain constant in the continued presence of NGF. Induction is insensitive to variations in culture conditions, such as plating density or substrate, which influence NGF-induced neurite outgrowth. Other inducers, in order of decreasing efficacy, are FGF, dBcAMP, TPA, K+, and EGF. Insulin and retinoic acid are ineffective. Dexamethasone partially inhibited basal expression as well as induction by NGF, FGF, dBcAMP, and TPA. The methyltransferase inhibitor 5'-S-(2-methyl-propyl)adenosine completely inhibited induction by NGF, FGF, and dBcAMP. Inhibition of protein synthesis by cycloheximide partially decreased induction by NGF, FGF, and TPA but slightly enhanced dBcAMP induction. Complete down-regulation of protein kinase C by chronic TPA treatment completely eliminated the TPA response but slightly enhanced induction by NGF. These findings and the results of additivity experiments in which cells were stimulated with various combinations of NGF, dBcAMP and TPA suggest that NGF induction of GAP-43 RNA (1) does not involve activation of protein kinase C but (2) may be mediated partially via activation of protein kinase A.
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PMID:Factors influencing GAP-43 gene expression in PC12 pheochromocytoma cells. 213 63

The effect of protein kinase modulators on the ability of nerve and fibroblast growth factors to induce neurite outgrowth in pheochromocytoma PC12 cells was studied. The protein kinase inhibitor H7 increased the neurite-stimulating capacity of these factors. The effect of H7 was observed within 1 h and was dose-dependent. HA 1004, an inhibitor of cAMP- and cGMP-dependent protein kinases, did not affect the neurite-stimulating activity of NGF. Substances inhibiting protein kinase C, ganglioside GT1b and quercetin, acted in a similar way whereas sphingosine had an opposite effect.
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PMID:Effect of protein kinase modulators on the induction of morphological differentiation of pheochromocytoma PC12 cells by nerve and fibroblast growth factors. 215 22

Sensory neurons of the chick embryo are supported in culture by several neurotrophic factors, including the phorbol esters. Because phorbol esters are known to activate one of the second messengers, namely, protein kinase C, it was of interest to see if the neurotrophic action of phorbol 12,13-dibutyrate (PDB) was related to the activation of protein kinase C in sensory neurons. Sensory neurons were obtained from dorsal root ganglia of 10-day-old chick embryos and maintained in a serum-free medium for several days to quantify survival and analyze protein kinase C activity. PDB (30 nM) supported the survival of approximately 50% of the total number of neurons plated. This value was comparable to that supported by nerve growth factor (NGF; 40 ng/ml). If PDB and NGF were added together, there was no additive effect on the survival. The protein kinase C activity of the particulate and cytosolic fractions of sensory neurons supported by NGF for 3 days was 1.26 +/- 0.1 and 2.9 +/- 0.32 pmol/min/mg of protein, respectively. In contrast, neurons supported by PDB showed an approximately 500% increase in enzyme activity in their particulate fraction. The enzyme activity of the cytosolic fraction was decreased by approximately 40%. If NGF-supported neurons were treated with PDB (30 nM) for 15 min, protein kinase C activity increased greater than 400% in the particulate fraction, whereas an approximately 50% decrease was observed in the cytosolic fraction. The protein kinase C value, expressed as a ratio of the activities in the particulate to cytosol fractions, showed large increases after phorbol treatment.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Survival of chick embryonic sensory neurons in culture is supported by phorbol esters. 229 56

The rise of the NGF mRNA pool which takes place following exposure of L-929 fibroblasts to serum was prevented in the presence of 5 microM K-252a, a compound which inhibits several species of protein kinase activities. To characterize further this phenomenon, L-929 cells growing in a serum-free medium were exposed to cyclic nucleotide analogs, to a divalent cation ionophore or to the phorbol ester PMA. Only this latter compound induced an enhancement of the NGF mRNA pool, suggesting an involvement of protein kinase C in the upregulation of the NGF transcripts. The effects of PMA or serum also require a synthesis of protein since the level of NGF transcripts remained stable in the presence of cycloheximide.
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PMID:Phorbol 12-myristate 13-acetate (PMA) increases the expression of the nerve growth factor (NGF) gene in mouse L-929 fibroblasts. 231 11


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