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

K(+)-induced depolarization of rat hippocampal slices resulted in significant increases in the phosphorylation state of myristoylated, alanine-rich C kinase substrate (MARCKS; also known as 87K, pp80) and neuromodulin [also known as growth associated protein 43 (GAP43), B50, F1] as determined by back-phosphorylation using protein kinase C. The effect of organic and inorganic Ca2+ antagonists on the phosphorylation of these major protein kinase C substrates in the rat hippocampus was studied to determine whether Ca2+ influx through L- or N-type voltage-sensitive Ca2+ channels was required for the phosphorylation changes observed. The depolarization-induced changes appeared to be dependent on extracellular Ca2+, based on evidence indicating that the chelation of extracellular Ca2+ with ethylene glycol-bis (beta-amino-ethyl ether)-N,N,N',N'-tetraacetic acid (EGTA) inhibited these changes. In addition, pretreatment of the slices with 500 microM Cd2+, but not 300 nM nimodipine, 10 microM omega-conotoxin GVIA or 10 microM MK-801, blocked the K(+)-induced change in phosphorylation. These results suggest that K(+)-induced changes in the phosphorylation of MARCKS and neuromodulin are mediated by Ca(2+)-dependent mechanisms other than, or in addition to, those sensitive to the organic Ca2+ channel antagonists employed.
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PMID:Effects of calcium channel antagonists on the phosphorylation of major protein kinase C substrates in the rat hippocampus. 836 41

Addition of bombesin to Swiss 3T3 cells causes a rapid and transient increase in the intracellular concentration of Ca2+ ([Ca2+]i), which is followed by desensitization to a subsequent addition of the peptide. The concentrations of bombesin used to study this acute cellular desensitization (0.1-0.5 nM) did not deplete the intracellular pool of Ca2+ released by inositol(1,4,5)trisphosphate, as shown by addition of vasopressin after consecutive additions of bombesin. Two lines of evidence support the conclusion that activation of protein kinase C (PKC) does not mediate the acute homologous desensitization of Ca2+ responses induced by bombesin. First, long-term treatment (48 h) of Swiss 3T3 cells with phorbol 12,13-dibutyrate (PDB) to deplete PKC did not prevent homologous desensitization. The responses to second additions of bombesin at 0.1, 0.25, and 0.5 nM were 42%, 26% and 11% of the initial responses, respectively. Second, the PKC inhibitor GF 109203X did not alter homologous desensitization at concentrations that completely prevented the inhibition of Ca2+ mobilization induced by PDB and blocked PDB-mediated phosphorylation of the prominent PKC substrate 80K/MARCKS. We conclude that acute homologous desensitization of Ca2+ responses induced by bombesin occurs through a PKC-independent mechanism.
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PMID:Homologous desensitization of bombesin-induced increases in intracellular Ca2+ in quiescent Swiss 3T3 cells involves a protein kinase C-independent mechanism. 839 79

The 43-kD growth-associated protein (GAP-43) is a major protein kinase C (PKC) substrate of growing axons, and of developing nerve terminals and glial cells. It is a highly hydrophilic protein associated with the cortical cytoskeleton and membranes. In neurons it is rapidly transported from the cell body to growth cones and nerve terminals, where it accumulates. To define the role of GAP-43 in neurite outgrowth, we analyzed neurite regeneration in cultured dorsal root ganglia (DRG) neurons that had been depleted of GAP-43 with any of three nonoverlapping antisense oligonucleotides. The GAP-43 depletion procedure was specific for this protein and an antisense oligonucleotide to the related PKC substrate MARCKS did not detectably affect GAP-43 immunoreactivity. We report that neurite outgrowth and morphology depended on the levels of GAP-43 in the neurons in a substrate-specific manner. When grown on a laminin substratum, GAP-43-depleted neurons extended longer, thinner and less branched neurites with strikingly smaller growth cones than their GAP-43-expressing counterparts. In contrast, suppression of GAP-43 expression prevented growth cone and neurite formation when DRG neurons were plated on poly-L-ornithine. These findings indicate that GAP-43 plays an important role in growth cone formation and neurite outgrowth. It may be involved in the potentiation of growth cone responses to external signals affecting process formation and guidance.
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PMID:Depletion of 43-kD growth-associated protein in primary sensory neurons leads to diminished formation and spreading of growth cones. 840 23

MARCKS is one of the major physiological substrates of PKC and was reported to be phosphorylated by PKC at 4 serine residues that are within the CaM-binding region (Graff et al., J. Biol. Chem. 264, 11912, 1989). Using MARCKS from rat brain and a synthetic peptide of 25 amino acids containing all 4 of the serine residues, we investigate the differences in phosphorylation by PKC isozymes I, II and III. Tryptic peptide analysis of PKC phosphorylated MARCKS or peptide, we found 32P was in peptides of (K)S152FK, (R)FS156FK and LS160GFS163FK. Further digestion of LSGFSFK with alpha-chymotrypsin revealed that 32P incorporation occurred only at Ser163 but not at Ser160. The initial rates and stoichiomatry of phosphorylation of Ser152 and Ser156 were twice as those of Ser163 using either one of the three PKC isozymes. These results indicate that in vitro, PKC phosphorylates MARCKS only at three sites, but not at Ser160 as that reported previously, and there was no preferential phosphorylation of MARCKS by either PKC isozyme I, II or III.
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PMID:Protein kinase C phosphorylates Ser152, Ser156 and Ser163 but not Ser160 of MARCKS in rat brain. 842 48

The intracellular signaling pathways used by cytokines to modulate the activity of immune effector cells have been the focus of intensive research. Cytokines interact with specific receptors on the plasma membrane, and this information is transduced into internal signals, often involving a cascade of kinases. These signals activate substrate proteins that serve as effectors within the cell. A number of protein kinase C substrates have been characterized. The function of one of these substrates, known as MARCKS (myristoylated alanine-rich C kinase substrate), appears to be important to the control of macrophage and neutrophil motility and may partially explain the modes of action of tumor necrosis factor and interleukin-8.
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PMID:How cytokines signal messages within cells. 843 16

Phorbol ester-inducible phosphorylation of MARCKS, the '80-kDa' substrate of protein kinase C, was undetectable in several phenotypically dominant, non-transformed revertants independently derived from the ras-transformed cell line NIH3T3 DT-ras. Extremely low expression of MARCKS protein accounted for this apparent lack of phosphorylation. MARCKS-encoding mRNA levels were correspondingly decreased relative to normal and ras-transformed cells in all four ras revertant cell lines studied: C-11 and F-2, derived by 5-azacytidine treatment and selection with ouabain; CHP 9CJ, derived by ethylmethane sulfonate mutagenesis and selection with cis-hydroxy-L-proline; and 12-V3, derived by transfection with the human Krev-1 gene. However, re-expression of MARCKS after transfection of a cloned MARCKS cDNA into the C-11 ras revertant cells was not sufficient to induce retransformation. In fact, no significant difference in sensitivity to mitogenic stimulation by phorbol esters was observed among several cell lines expressing widely varying levels of MARCKS. This evidence argues against a direct role for MARCKS in mitogenic signaling. However, the strong correlation between attenuation of MARCIS expression and phenotypically dominant ras reversion suggests that a common negative regulatory mechanism might be responsible for both effects, presenting a potentially useful strategy for identifying factors involved in transducing the ras signal.
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PMID:Severely decreased MARCKS expression correlates with ras reversion but not with mitogenic responsiveness. 843 59

An 80-kDa protein labeled with [3H]myristic acid in C6 glioma and N1E-115 neuroblastoma cells has been identified as the myristoylated alanine-rich C kinase substrate (MARCKS protein) on the basis of its calmodulin-binding, acidic nature, heat stability, and immunochemical properties. When C6 cells preincubated with [3H]myristate were treated with 200 nM 4 beta-12-O-tetradecanoylphorbol 13-acetate (beta-TPA), labeled MARCKS was rapidly increased in the soluble digitonin fraction (maximal, fivefold at 10 min) with a concomitant decrease in the Triton X-100-soluble membrane fraction. However, phosphorylation of this protein was increased in the presence of beta-TPA to a similar extent in both fractions (maximal, fourfold at 30 min). In contrast, beta-TPA-stimulated phosphorylation of MARCKS in N1E-115 cells was confined to the membrane fraction only and no change in the distribution of the myristoylated protein was noted relative to alpha-TPA controls. These results indicate that although phosphorylation of MARCKS by protein kinase C occurs in both cell lines, it is not directly associated with translocation from membrane to cytosol, which occurs in C6 cells only. The cell-specific translocation of MARCKS appears to correlate with previously demonstrated differential effects of phorbol esters on stimulation of phosphatidylcholine turnover in these two cell lines.
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PMID:Dissociation of phosphorylation and translocation of a myristoylated protein kinase C substrate (MARCKS protein) in C6 glioma and N1E-115 neuroblastoma cells. 845 32

A substrate protein of protein kinase C with an apparent molecular mass of 70 kDa has been purified from bovine brain. This protein shares several properties with a major substrate of protein kinase C (myristoylated alanine-rich C kinase substrate; MARCKS). It is heat-stable and copurifies with MARCKS during various steps (ammonium sulfate precipitation and gel filtration). However, its elution from a calmodulin affinity column is different from that of MARCKS. It can be eluted by high ionic strength in the presence of calcium, whereas MARCKS can be eluted only in the absence of calcium. Its earlier elution from a reversed phase column suggests that p70 is less hydrophobic than MARCKS. The electrospray mass spectrum revealed an actual mass of 31,550 +/- 6.5 Da, very far from the apparent molecular mass in SDS-polyacrylamide gel electrophoresis (70,000 Da). This mass is about 200 Da smaller than that of MARCKS determined by mass spectrometry analysis (Manenti, S., Sorokine, O., Van Dorsselaer, A., and Taniguchi, H. (1992) J. Biol. Chem. 267, 22310-22315), close to the value expected for the change due to N-terminal myristoylation (210 Da). N-terminal amino acid sequencing showed that the N terminus is not blocked, and the sequence found for the 10 first amino acids is identical to that deduced from the cDNA sequence of bovine MARCKS. These data clearly establish that this protein is a non-myristoylated form of MARCKS and that the absence of the myristoyl moiety at the N terminus lowers the affinity to calmodulin. The purification performed both from the membrane and the cytoplasmic fractions of bovine brain indicated that this non-myristoylated form represents 20-30% of the MARCKS protein in the cytoplasmic fraction, and less than 5% in the membrane one.
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PMID:Isolation of the non-myristoylated form of a major substrate of protein kinase C (MARCKS) from bovine brain. 846 17

The expression of the major protein kinase C (PKC) substrate, originally called "80K" for acidic SDS/PAGE-observed 80-kDa PKC substrate and now called "MARCKS" for myristoylated alanine-rich C kinase substrate, in Swiss 3T3 fibroblasts changes strikingly (15- to 22-fold) during transitions of cell growth. Quiescent cells in G0 express high levels of MARCKS mRNA and protein. However, plating these cells in fresh medium at low density to stimulate multiple rounds of cell division caused a striking down-regulation of MARCKS expression. The mRNA level declined to a minimum of 4.5% compared with quiescent control cells 6 hr after plating, and protein levels declined during the same period to 6.5% of the control value. This rapid down-regulation was independent of PKC activation and length of exposure to trypsin (1-10 min) but required plating in medium containing fresh serum. MARCKS mRNA and protein levels remained down-regulated for 3 days, during which time the cells were actively progressing through the cell cycle as judged by fluorescence-activated cell sorting analysis. However, on reaching quiescence, the expression of MARCKS mRNA and protein increased markedly. Furthermore, the rate of recovery of MARCKS mRNA and protein levels was shown to be dependent on the supply of serum-derived growth factors in the medium. Addition of hydroxyurea to arrest the cells in S phase or at the G1/S boundary rather than G0 completely prevented the recovery of MARCKS protein. The down-regulation of MARCKS following plating and its serum-dependent recovery was also demonstrated in tertiary cultures of mouse embryo fibroblasts. The results suggest that MARCKS may play a role in the regulation of entry and exit of cells from G0.
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PMID:Expression of the major protein kinase C substrate, the acidic 80-kilodalton myristoylated alanine-rich C kinase substrate, increases sharply when Swiss 3T3 cells move out of cycle and enter G0. 846 11

A major in vivo substrate of Ca(2+)-phospholipid-dependent protein kinase (MARCKS) shows phosphorylation-dependent translocation between the cytoplasmic and the membrane fractions. The mechanism of the translocation was studied with purified MARCKS and various membranes. MARCKS was found to bind to pure phospholipid membranes as well as to the synaptic vesicle membranes. Although the interaction of MARCKS with the latter was phosphorylation-dependent, phosphorylation by protein kinase C showed no significant effect on the binding to the phosphatidylcholine liposomes. However, when phosphatidylserine was included in the membranes, the association became phosphorylation-dependent. A synthetic phosphorylation domain peptide showed a similar phosphorylation-dependent interaction with the negatively charged liposomes. Phosphatidylserine but not phosphatidylcholine inhibited phosphorylation of MARCKS by protein kinase C. MARCKS seems to bind to the biomembranes through two binding sites: the N-terminal myristoyl moiety and the basic phosphorylation domain of amphiphilic nature. Phosphorylation of this domain lowers its affinity to phosphatidylserine and makes the whole molecule strongly negatively charged, which causes its dissociation from the membranes.
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PMID:Interaction of myristoylated alanine-rich protein kinase C substrate (MARCKS) with membrane phospholipids. 848 22


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