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)

The JAR human placental choriocarcinoma cell line transports taurine, concentrating it over 1000-fold inside the cell. The transport system is energized by a Na+ gradient and exhibits an absolute requirement for Cl-. Neutral beta-amino acids such as beta-alanine and hypotaurine effectively compete with the system, whereas neutral alpha-amino acids such as alanine, leucine and alpha-aminoisobutyric acid do not. The transport system interacts with gamma-aminobutyric acid to an appreciable extent. Kinetic analysis reveals that the taurine transport system in this cell line is of a high-affinity and low-capacity type (apparent dissociation constant 2.3 +/- 0.3 microM; maximal velocity 88.5 +/- 5.0 pmol/3 min per mg of protein). Pretreatment of the JAR choriocarcinoma cells with phorbol 12-myristate 13-acetate results in the inhibition of the taurine transport system in a dose-dependent manner. The inhibition is blocked by co-treatment of the cells with staurosporine, an inhibitor of protein kinase C. The inactive phorbol ester, 4 alpha-phorbol 12,13-didecanoate, has no effect on the transport system. These data show that the choriocarcinoma cells express a taurine transporter with characteristics similar to those of the taurine transporter described in the normal human placenta, and that the activity of the transporter in these cells is under the regulatory control of protein kinase C.
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PMID:Transport of taurine and its regulation by protein kinase C in the JAR human placental choriocarcinoma cell line. 185 47

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)
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PMID:Regulation of taurine transport in human colon carcinoma cell lines (HT-29 and Caco-2) by protein kinase C. 849 20

Data describing characteristics of taurine transport system in human brain cells are not currently available. We have used GL15 cells, a cell line of human brain origin that keeps some properties of normal glial cells, to investigate these characteristics. The human glioma cell line GL15 was found to take up taurine. The uptake was strictly sodium-dependent. Replacement of NaCl with choline chloride almost totally abolished the uptake. There was also an anion requirement for the uptake system, and Cl- was the most potent among several monovalent anions tested. The uptake process was specific for beta-amino acids such as taurine, hypotaurine and beta-alanine. The kinetics of uptake were studied. Apparently, a single transport system with a K(m) of 8.95 +/- 0.26 microM was responsible for the uptake. A maximal velocity of 1.32 +/- 0.03 nmol/mg of protein/10 min was found. Stoichiometric analysis revealed that two Na+ and one Cl- ions were involved in the translocation of one taurine molecule. Phorbol 12-myristate 13-acetate (PMA), a potent stimulator of protein kinase C (PKC), inhibited taurine uptake. Maximal inhibition was obtained at 50 nM after 1 hr of treatment. This effect was prevented by pretreatment of the cells with chelerythrine, a potent and selective inhibitor of PKC. The transport of beta-alanine was inhibited to a comparative extent. The mechanism of this inhibition was not investigated, but it was found that this inhibitory effect was not prevented by cycloheximide, actinomycin D, colchicine or cytochalasin D, indicating that neither protein synthesis, nor microfilament function were involved. The effect of PMA was associated with an impairment of kinetic constants. It is concluded that human GL15 cells have a taurine transporter similar to that expressed in rodent glial cells, and that the activation of PKC can modulate the activity of this transporter.
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PMID:Characterization of taurine transport in human glioma GL15 cell line: regulation by protein kinase C. 868 95

The goal was to investigate the role of protein kinases in modulating taurine transporter activity in Xenopus laevis oocytes expressing the mouse retinal Na+/C-/taurine transporter. The currents generated by the taurine transporter were studied with a two-electrode voltage clamp and we recorded the maximal current (Imax), presteady-state charge transfer Q, and membrane capacitance Cm. 8-Br-cAMP, a membrane-permeable activator of the cAMP-dependent protein kinase (PKA), decreased Imax (41%), Q (41%) and Cm (10%). Similarly, 1 microM sn-1,2-dioctanoylglycerol (DOG), an activator of the Ca2+/diacylglycerol-dependent protein kinase (PKC), decreased Imax (56%), Q (37%), and Cm (9%). Calyculin A, a specific inhibitor of protein phosphatases 1 and 2A, also produced effects similar to those of 8-Br-cAMP and DOG, and decreased Imax (64 %), Q (38%), and Cm (10%). We conclude that the taurine transporter is regulated by activators of PKA and PKC, and regulation occurs largely by changes in the number of transporters in the plasma membrane.
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PMID:Regulation of the mouse retinal taurine transporter (TAUT) by protein kinases in Xenopus oocytes. 877 55

Phorbol myristate acetate (PMA), a protein kinase C (PKC) activator significantly decreased in a time- and dose-dependent manner taurine uptake by rat astroglial but not neuronal cells. The PMA-induced inhibition of taurine uptake by rat astrocytes was prevented by chelerythrine, a potent and selective inhibitor of PKC. The differential effect of PMA on rat neuronal and astroglial taurine transport was also obtained with the protein phosphatase inhibitor okadaic acid. This was not only the feature of rat cells since the same differential effects were obtained with human glioma GL15 and human neuroblastoma IMR32 cell lines. The results suggest that the neuronal and astroglial taurine transporter may be structurally different.
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PMID:Activation of protein kinase C down-regulates glial but not neuronal taurine uptake. 884 83

Activation of protein kinase C (PKC) by the active phorbol ester 12-myristate 13-acetate (PMA, 100 nM) or phorbol-12, 13-dibutyrate (100 nM) reduced taurine uptake by 80% in oocytes given injections with cRNA from and expressing the Madin-Darby canine kidney cell taurine transporter pNCT. Inhibition of PKC by calphostin C or staurosporine increased taurine uptake by 20% and 400%, respectively. The inhibitory effect of PMA on taurine uptake was blocked by calphostin C, a specific inhibitor of PKC. Modulation by PMA mainly affected the apparent affinity K(m) (from 5.6 microM to 18.1 microM) with minimal effect on the maximal velocity (25% decrease) of the transporter. A polyclonal antibody (AbS4) directed against a conserved intracellular segment (S4) of the Madin-Darby canine kidney cell taurine transporter enhanced taurine uptake by pNCT cRNA-treated oocytes. The effect of AbS4 was blocked by incubation with the corresponding peptide antigen. Preimmune IgG and peptide antigen had no effect on taurine transporter activity expressed in oocytes. Modulation seemed to occur through phosphorylation of a consensus PKC site located on segment S4 of the transporter, because downregulation of the transporter by PMA (100 nM) was abolished by preinjection of AbS4 (12 ng/ oocyte). In contrast, downregulation of the transporter by PMA could not be restored by AbS4 when pNCT-expressing oocytes were pretreated with PMA (50 nM). In conclusion, the peptide segment recognized by this antibody appears to participate directly in taurine transporter inactivation that is modulated by PKC phosphorylation.
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PMID:Role of conserved peptide in taurine transporter inactivation modulated by protein kinase C. 891 68

Studies have shown that the renal tubular epithelium adapts to alterations in the sulfur amino acid composition of the diet. The renal adaptive response has been described in man, mouse, rat, dog, and pig. The observed phenomenon involves increased or decreased initial rate activity of the NaCl-dependent taurine transporter at the brush border membrane surface of the proximal tubule following dietary manipulation of taurine. A cDNA encoding a taurine transporter has been isolated from LLC-PK1 cells, designated pTAUT, and its functional properties have been examined in Xenopus laevis oocytes. The nucleotide sequence of the clone predicts a 621-amino acid protein with about 90% homology to other cloned taurine transporter cDNAs. When expressed in oocytes the transporter displays a Km of 25 microM and is dependent on the presence of external sodium and chloride, characteristics similar to taurine uptake by LLC-PK1 cells. The abundance of pTAUT mRNA and protein were up-regulated in cells cultured in taurine-free medium as compared with cells cultured in medium containing 500 microM taurine. Activation of PKC by PMA had no effect on adaptive regulation of pTAUT mRNA and protein, indicating that down-regulation of LLC-PK1 cell taurine transport activity by PMA occurs at the post-translational level.
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PMID:Molecular cloning and functional expression of an LLC-PK1 cell taurine transporter that is adaptively regulated by taurine. 963 40

The influence of osmolarity and compatible organic osmolytes on the phosphorylation of the MAP-kinases Erk-1 and Erk-2 and on the expression of taurine transporter (TAUT) and lipopolysaccharide (LPS)-induced nitric oxide synthetase (iNOS) was studied in RAW 264.7 mouse macrophages. Hypoosmolarity (205 mosmol/l) but not hyperosmolarity (405 mosmol/l) or challenge of the cells with betaine or taurine increased phosphorylation of Erk-1 and Erk-2. Hypoosmotic Erk-phosphorylation was blocked by the MEK-inhibitor PD098059 but was resistant to depletion of extracellular calcium and to inhibition of PLC, PKC, erbstatin-sensitive tyrosine kinases and elevation of intracellular cAMP. Hyperosmolarity stimulated Na+-dependent taurine uptake and led to an increase of TAUT mRNA levels, whereas hypoosmotic exposure diminished both and induced a rapid efflux of the osmolyte from taurine-preloaded cells. The hyperosmotic elevation of TAUT mRNA levels was antagonized upon addition of taurine but not of betaine or myo-inositol. Hyperosmolarity increased the LPS-induced iNOS expression at the mRNA and the protein level. This was suppressed by betaine but not by taurine or myo-inositol. The osmotic regulation of taurine transport and iNOS expression appeared independent of the MEK-Erk pathway and the p38MAPK.
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PMID:Compatible organic osmolytes and osmotic modulation of inducible nitric oxide synthetase in RAW 264.7 mouse macrophages. 970 50

Previous studies have shown that the Madin-Darby canine kidney cell taurine transporter (pNCT) is downregulated by protein kinase C (PKC) activation. In this study, it is hypothesized that the highly conserved serine-322 (Ser-322) located in the fourth intracellular segment (S4) may play an important role in the function of taurine transporter, which is modulated by PKC phosphorylation. It is demonstrated that Ser-322 is the critical site of PKC phosphorylation, as determined by site-directed mutagenesis. When Ser-322 of pNCT was changed to alanine (S322A) and this mutant was evaluated in an oocyte expression system, taurine transport activity increased threefold compared with control (wild-type pNCT). Activation of PKC by the active phorbol ester 12-myristate 13-acetate did not influence taurine transport by mutant S322A. Kinetic analysis showed that the mutation of Ser-322 essentially changed the Vmax, rather than the Km, of the transporter. Mutation of all other PKC consensus sites did not affect transporter activity when expressed in the oocyte system. Western blot analysis showed that expression of taurine transporter protein was similar in oocytes injected with either wild-type or mutant pNCT cRNA, indicating that the enhanced taurine transport activity by mutant S322A was not caused by a greater amount of transporter expressed in the oocyte. Furthermore, this study demonstrated that the taurine transporter was phosphorylated after PKC activation, and this effect was not observed in mutant S322A. In conclusion, Ser-322 is critical in PKC regulation of taurine transporter activity. The steady-state taurine transporter activity is tightly controlled by endogenous PKC phosphorylation of Ser-322, which is located in the fourth intracellular segment of the taurine transporter.
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PMID:Ser-322 is a critical site for PKC regulation of the MDCK cell taurine transporter (pNCT). 1047 38

Cultured bovine aortic endothelial (BAE) cells expressed a Na(+)/Cl(-)-dependent taurine uptake activity that saturated with an apparent K(0.5) of approximately 4.9 microM for taurine and was inhibited by beta-alanine, guanidinoethane sulfonate, and homotaurine. We isolated a taurine transporter clone from a BAE cell cDNA library that revealed >91% sequence identity at the amino acid level to the previously cloned high-affinity mammalian taurine transporters. The biochemical and pharmacological properties of the bovine taurine transporter cDNA expressed in Xenopus oocyte was similar to those of the high-affinity taurine transporter. Surprisingly, F(-) blocked taurine uptake in BAE cells with an IC(50) of approximately 17.5 mM. The endogenous taurine uptake was also inhibited by the protein kinase C activator phorbol 12-myristate 13-acetate, but not by its inactive analog, 4 alpha-phorbol 12,13-didecanoate. The endogenous uptake was stimulated, however, by hypertonic stress and the increase was due to an increase in the V(max) of taurine uptake. Our results provide the first description of a molecular mechanism that may be responsible for maintaining the intracellular taurine content in the endothelial cells.
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PMID:Molecular characterization of taurine transport in bovine aortic endothelial cells. 1111 43


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