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)

c-jun is a member of the family of immediate-early genes whose expression is induced by factors such as serum stimulation, phorbol ester, and differentiation signals. Here we show that increased Jun synthesis after serum stimulation is accompanied by a concomitant increase in phosphorylation. Several serine-threonine kinases were evaluated for their ability to phosphorylate Jun in vitro. p34cdc2, protein kinase C, casein kinase II, and pp44mapk phosphorylated Jun efficiently, whereas cyclic AMP-dependent protein kinase and glycogen synthase kinase III did not. The sites phosphorylated by p34cdc2 were similar to those phosphorylated in vivo after serum induction. The major sites of phosphorylation were mapped to serines 63, 73, and 246. Phosphorylation of full-length Jun with several kinases did not affect the DNA-binding activity of Jun homodimers or Fos-Jun heterodimers. Comparison of the DNA binding and in vitro transcription properties of wild-type and mutated proteins containing either alanine or aspartic acid residues in place of Ser-63, -73, and -246 revealed only minor differences among homodimeric complexes and no differences among Fos-Jun heterodimers. Thus, phosphorylation of Jun did not produce a significant change in dimerization, DNA-binding, or in vitro transcription activity. The regulatory role of phosphorylation in the modulation of Jun function is likely to be considerably more complex than previously suggested.
 ...
PMID:Jun is phosphorylated by several protein kinases at the same sites that are modified in serum-stimulated fibroblasts. 132 60

The nef gene product of the human immunodeficiency virus (HIV) is suggested to be a negative factor involved in down-regulating viral expression by a mechanism in which the correct conformation of the nef protein is essential. The nef protein expressed by vaccinia virus recombinants is phosphorylated by protein kinase C. We investigated the synthesis of the nef protein and its state of phosphorylation during HIV-1 infection of a T4 cell line (CEM cells). Maximum synthesis of viral proteins occurred 3 days after infection, when more than 90% of cells were producing viral proteins. The synthesis of the nef protein was detected in parallel with the env and gag proteins. As expected, the nef protein was myristylated but not phosphorylated, and its half-life was less than 1 h. By the use of the polymerase chain reaction technique, we isolated and sequenced the nef gene of this HIV-1 stock. Two significant mutations were observed. Firstly, threonine, at amino acid number 15, the site of phosphorylation by protein kinase C, was mutated into an alanine, and secondly aspartic acid of the tetrapeptide WRFD, which is probably involved in GTP binding, was mutated into an asparagine. The mutated nef gene was expressed in a vaccinia virus system, in which it was not phosphorylated and its half-life was dramatically reduced compared to the wild-type nef gene product. Furthermore, down-regulation of CD4 cell surface expression was no longer affected by the mutated nef gene. These results emphasize that phosphorylation of the nef protein provides an efficient test to monitor its biological activity.
 ...
PMID:Production of a non-functional nef protein in human immunodeficiency virus type 1-infected CEM cells. 197 71

A high Mr synthetase core complex isolated from higher eukaryotes contains aminoacyl-tRNA synthetases specific for arginine, aspartic acid, glutamic acid, glutamine, isoleucine, leucine, lysine, methionine, and proline. Previously, five of the synthetases were shown to be phosphorylated in reticulocytes, and the glutaminyl- and aspartyl-tRNA synthetases were shown to be selectively phosphorylated in response to 8-bromo cAMP (Pendergast, A. M., Venema, R. C., and Traugh, J. A. (1987) J. Biol. Chem. 262, 5939-5942). Exposure of reticulocytes to phorbol 12-myristate 13-acetate stimulates the selective phosphorylation of one synthetase in the complex, glutamyl-tRNA synthetase. Only the glutamyl-tRNA synthetase is modified to a significant extent when the purified complex is phosphorylated in vitro by protein kinase C; up to 0.7 mol of phosphate is incorporated per mol of synthetase. Two-dimensional phosphopeptide mapping shows a single tryptic phosphopeptide, which is identical for the enzyme modified in vitro by protein kinase C or in phorbol 12-myristate 13-acetate-stimulated cells. Phosphorylation in vivo is reproducibly accompanied by a 38 +/- 10% reduction in aminoacylation activity of partially purified glutamyl-tRNA synthetase assayed in vitro. Phosphorylation in vitro has no detectable effect on aminoacylation. This difference may be due to the absence of a required effector molecule which alters activity by interaction with the phosphorylated synthetase. Glutamyl-tRNA synthetase is one of a growing number of translational components, including initiation factors, which are coordinately modified by protein kinase C in response to phorbol 12-myristate 13-acetate.
 ...
PMID:Protein kinase C phosphorylates glutamyl-tRNA synthetase in rabbit reticulocytes stimulated by tumor promoting phorbol esters. 200 62

An altered protein expression of Ca(2+)-dependent protein kinase C (PKC) isoforms and a point mutation in the PKC alpha cDNA (position 908 of the nucleotide sequence, position 294 of the amino acid sequence, substitution of an aspartic acid by a glycine) have been previously described in a subpopulation of human pituitary tumors. In this work, we screened 16 thyroid tissue samples (four follicular adenomas, five colloid adenomas, three papillary carcinomas, one follicular carcinoma and three normal tissues adjacent to the tumors) for the presence of the PKC alpha point mutation and for PKC alpha, beta 1, beta 2, epsilon and delta protein expression. Screening for the presence of the PKC alpha mutant was performed by a subcloning technic. The polymerase chain reaction products were generated using reverse-transcribed cDNAs, subcloned and sequenced (10 clones were routinely sequenced). The PKC alpha point mutation at position 908 of the cDNA sequence was found in four out of the nine adenomas and in the follicular carcinoma. It was neither detected in the papillary carcinomas nor in the adjacent normal tissues (one was the adjacent normal tissue of the follicular carcinoma; in this sample, genomic DNA and cDNA were used to look for the presence of the mutant), demonstrating the somatic nature of this mutant. Western blot analysis of PKC isoforms showed that the expression of all isoforms was higher in the thyroid neoplasms as compared with their adjacent normal tissue (n = 3). It was also higher in the samples containing the PKC mutant (two follicular adenomas, two colloid adenomas and the follicular carcinoma) as compared with the tumors where it was not detected (three papillary carcinomas and five adenomas). Samples could be ordered according to their increasing PKC expression as follows: normal adjacent tissue < follicular adenomas without PKC alpha mutant < or = papillary carcinoma < follicular adenomas with PKC mutant < follicular carcinoma with PKC mutant. In conclusion, the discovery of the PKC alpha mutant in thyroid neoplasms demonstrates that this mutant is not particular to human pituitary tumors where it was originally detected. It is a somatic mutation and its presence is concomitant with high levels of all of the PKC isoforms analysed. The presence of the PKC mutant in thyroid neoplasms raises the question of its importance in thyroid tumorigenesis.
 ...
PMID:The natural protein kinase C alpha mutant is present in human thyroid neoplasms. 765 30

The effect of protein kinase C (PKC) on rapid N-type inactivation of K+ channels has not been reported previously. We found that PKC specifically eliminates rapid inactivation of a cloned human A-type K+ channel (hKv3.4), converting this channel from a rapidly inactivating A type to a noninactivating delayed rectifier type. Biochemical analysis showed that the N-terminal domain of hKv3.4 is phosphorylated in vitro by PKC, and mutagenesis experiments revealed that two serines within the inactivation gate at the N-terminus are sites of direct PKC action. Moreover, mutating one of these serines to aspartic acid mimics the action of PKC. Serine phosphorylation may thus prevent rapid inactivation by shielding basic residues known to be critical to the function of the inactivation gate. The regulatory mechanism reported here may have substantial effects on signal coding in the nervous system.
 ...
PMID:Elimination of rapid potassium channel inactivation by phosphorylation of the inactivation gate. 799 31

Cardiac ventricular myocytes from several species, including the guinea pig, possess a cAMP-dependent protein kinase A (PKA)-activated Cl- channel. In the present study, the properties of a protein kinase C (PKC)-activated Cl- current were studied in isolated guinea pig ventricular myocytes using the whole-cell arrangement of the patch-clamp technique. Intracellular dialysis of ventricular cells with PKC resulted in the activation of a large background current that displayed time-independent kinetics. In the presence of 146 mmol/L external Cl- and 71 mmol/L internal Cl-, the reversal potential (Erev) of the background current (-17 +/- 1 mV) was close to that of the Cl- equilibrium potential (-18 mV), and the current versus voltage relation for the current was outward rectifying in shape. When [Cl-]i or [Cl-]o was reduced by substitution of Cl- with aspartic acid, Erev for the background current shifted in a manner expected for a Cl(-)-selective channel. Based on Erev measurements, the permeability sequence for this PKC-activated Cl- channel was determined to be SCN- > I- > Br- congruent to Cl-. The PKC-activated Cl- current was not inhibited by the Cl- channel blocker 4,4'-dinitrostilbene-2,2'-disulfonic acid (100 mumol/L) but could be blocked by anthracene-9-carboxylic acid (1 mmol/L). Activation of the current was abolished in the presence of the PKC inhibitor staurosporine (2.5 mumol/L). Under conditions designed to cause a maximal activation of the Cl- channels by PKC, the addition of forskolin (1 mumol/L) to stimulate PKA caused only a slight further increase in the amplitude of the Cl- current. Thus, PKC activates a Cl- channel in guinea pig ventricular cells with properties similar but not identical to the PKA-activated channel.
 ...
PMID:Properties of a protein kinase C-activated chloride current in guinea pig ventricular myocytes. 826 85

We have reported previously that the human vitamin D receptor (hVDR) is selectively phosphorylated by protein kinase C-beta (PKC-beta), in vitro, on a serine residue in the sequence RRS51MKRK, which is located between the two zinc fingers of hVDR and is potentially important to its transacting function (Hsieh, J.-C., Jurutka, P.W., Galligan, M.A., Terpening, C.M., Haussler, C.A., Samuels, D.S., Shimizu, Y., Shimizu, N., and Haussler, M.R. (1991) Proc. Natl. Acad. Sci. U.S.A. 88, 9315-9319). In the present experiments we evaluated this phosphorylation event using a series of hVDR mutants in which serine 51 or its flanking residues were modified. Alteration of serine 51 to a non-phosphorylatable residue resulted in an approximately 60% reduction in basal hVDR phosphorylation in intact cells but did not diminish 1,25-dihydroxyvitamin D3-stimulated phosphorylation. Such mutations also abolished subsequent phosphorylation of immunoprecipitated hVDR by purified PKC-beta, in vitro, as did replacement of basic residues on either side of serine 51. Mutation of serine 51 to glycine (S51G) or to aspartic acid (S51D), as well as altering the basic residues flanking serine 51, abolished the interaction of hVDR with the vitamin D-responsive element (VDRE) as monitored by gel mobility shift analysis. Thus, we conclude that unmodified serine 51 and its surrounding basic residues are crucial not only for PKC-beta substrate recognition but also for the optimal VDRE binding of native hVDR. In transactivation assays, S51G and S51D possessed only 35 and 10% of wild-type hVDR activity, respectively. Mutation of serine 51 to threonine (S51T) restored phosphorylation by PKC-beta, in vitro, to about 40% of wild-type and transactivation to 45% of that of wild-type hVDR. Alteration of serine 51 to alanine, which is the residue in the corresponding position of the glucocorticoid, progesterone, mineral-ocorticoid, and androgen receptors, eliminated PKC-beta phosphorylation but completely preserved the specific DNA binding activity and transactivation capacity of hVDR. Thus, phosphorylation of hVDR at serine 51 is not required for either VDRE binding or transactivation. Finally, incubation of Escherichia coli-expressed hVDR with PKC-beta elicits marked phosphorylation of the receptor and significantly inhibits its ability to complex with the VDRE. We therefore speculate that posttranslational modification of hVDR at serine 51 may constitute a negative regulatory loop which could be operative when target cells are subject to PKC activation events.
 ...
PMID:Phosphorylation of the human vitamin D receptor by protein kinase C. Biochemical and functional evaluation of the serine 51 recognition site. 839 65

The effect of phorbol 12-myristate 13-acetate (PMA), a phorbol ester known to stimulate protein kinase C, on taurine transport was studied in the human colon carcinoma cell line HT-29. PMA (1 microM) was found to inhibit taurine uptake in confluent monolayers of this cell line by approximately 70% after pretreatment of the cells with the compound for 1 h (IC50 = 42.7 +/- 2.6 nM). The inhibitory effect of PMA on the taurine transporter could be confirmed by using beta-alanine, another substrate for the transporter. Kinetic analysis of taurine uptake indicated that the PMA effect was associated with a decrease in the maximal velocity (954 +/- 26 vs. 676 +/- 28 pmol.10 min-1.mg of protein-1) and an increase in the Michaelis-Menten constant (9.8 +/- 0.5 vs. 13.3 +/- 1.0 microM). The inhibition of taurine uptake could be blocked by cotreatment of the cultures with staurosporine, an inhibitor of protein kinase C. The inactive phorbol ester 4 alpha-phorbol 12,13-didecanoate had no effect. Treatment of the cells with PMA did not alter the uptake of leucine and lysine, stimulated the uptake of aspartic acid, and inhibited the uptake of proline. The PMA effect on taurine uptake was not prevented by cycloheximide, actinomycin D, colchicine, or cytochalasin D. Comparison of the taurine transport activity in HT-29 cells with that in Caco-2, another human colon carcinoma cell line, revealed that the latter cell line also expressed the taurine transporter but at a much reduced level (about one-fifth compared with HT-29).(ABSTRACT TRUNCATED AT 250 WORDS)
 ...
PMID:Regulation of taurine transport in human colon carcinoma cell lines (HT-29 and Caco-2) by protein kinase C. 849 20

These studies demonstrate that treatment of human U-937 cells with ionizing radiation (IR) is associated with activation of a cytoplasmic myelin basic protein (MBP) kinase. Characterization of the kinase by gel filtration and in-gel kinase assays support activation of a 40 kDa protein. Substrate and inhibitor studies further support the induction of protein kinase C (PKC)-like activity. The results of N-terminal amino acid sequencing of the purified protein demonstrate identity of the kinase with an internal region of PKC delta. Immunoblot analysis was used to confirm proteolytic cleavage of intact 78 kDa PKC delta in control cells to the 40 kDa C-terminal fragment after IR exposure. The finding that both IR-induced proteolytic activation of PKC delta and endonucleolytic DNA fragmentation are blocked by Bcl-2 and Bcl-xL supports an association with physiological cell death (PCD). Moreover, cleavage of PKC delta occurs adjacent to aspartic acid at a site (QDN) similar to that involved in proteolytic activation of interleukin-1 beta converting enzyme (ICE). The specific tetrapeptide ICE inhibitor (YVAD) blocked both proteolytic activation of PKC delta and internucleosomal DNA fragmentation in IR-treated cells. These findings demonstrate that PCD is associated with proteolytic activation of PKC delta by an ICE-like protease.
 ...
PMID:Proteolytic activation of protein kinase C delta by an ICE-like protease in apoptotic cells. 855 34

To assess the role of phosphorylation of the human multidrug resistance MDR1 gene product P-glycoprotein for its drug transport activity, phosphorylation sites within its linker region were subjected to mutational analysis. We constructed a 5A mutant, in which serines at positions 661, 667, 671, 675, and 683 were replaced by nonphosphorylatable alanine residues, and a 5D mutant carrying aspartic acid residues at the respective positions to mimic permanently phosphorylated serine residues. Transfection studies revealed that both mutants were targeted properly to the cell surface and conferred multidrug resistance by diminishing drug accumulation. In contrast to wild-type P-glycoprotein, the overexpressed 5A and the 5D mutants exhibited no detectable levels of phosphorylation, either in vivo following metabolic labeling of cells with [32P]orthophosphate or in vitro in phosphorylation assays with protein kinase C, cAMP-dependent protein kinase, or a P-glyco-protein-specific protein kinase purified from multidrug-resistant KB-V1 cells. These results reconfirm that the major P-glycoprotein phosphorylation sites are located within the linker region. Furthermore, the first direct evidence is provided that phosphorylation/dephosphorylation mechanisms do not play an essential role in the establishment of the multidrug resistance phenotype mediated by human P-glycoprotein.
 ...
PMID:Characterization of phosphorylation-defective mutants of human P-glycoprotein expressed in mammalian cells. 857 73


1 2 3 4 5 6 7 Next >>