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)

The extracellular acidification rate of the human bone marrow cell line, TF-1, increases rapidly in response to a bolus of recombinant granulocyte-macrophage colony stimulating factor (GM-CSF). Extracellular acidification rates were measured using a silicon microphysiometer. This instrument contains micro-flow chambers equipped with potentiometric sensors to monitor pH. The cells are immobilized in a fibrin clot sandwiched between two porous polycarbonate membranes. The membranes are part of a disposable plastic "cell capsule" that fits into the microphysiometer flow chamber. The GM-CSF activated acidification burst is dose dependent and can be neutralized by pretreating the cytokine with anti-GM-CSF antibody. The acidification burst can be resolved kinetically into at least two components. A rapid component of the burst is due to activation of the sodium/proton antiporter as evidenced by its elimination in sodium-free medium and in the presence of amiloride. A slower component of the GM-CSF response is a consequence of increased glycolytic metabolism as demonstrated by its dependence on D-glucose as a medium nutrient. Okadaic acid (a phospho-serine/threonine phosphatase inhibitor), phorbol 12-myristate 13-acetate (PMA, a protein kinase C (PKC) activator), and ionomycin (a calcium ionophore) all produce metabolic bursts in TF-1 cells similar to the GM-CSF response. Pretreatment of TF-1 cells with PMA for 18 h resulted in loss of the GM-CSF acidification response. Although this treatment is reported to destroy protein kinase activity, we demonstrate here that it also down-regulates expression of high-affinity GM-CSF receptors on the surface of TF-1 cells. In addition, GM-CSF driven TF-1 cell proliferation was decreased after the 18 h PMA treatment. Short-term treatment with PMA (1-2 h) again resulted in loss of the GM-CSF acidification response, but without a decrease in expression of high-affinity GM-CSF receptors. Evidence for involvement of PKC in GM-CSF signal transduction was obtained using calphostin C, a specific inhibitor of PKC, which inhibited the GM-CSF metabolic burst at a subtoxic concentration. Genistein and herbimycin A, tyrosine kinase inhibitors, both inhibited the GM-CSF response of TF-1 cells, but only at levels high enough to also inhibit stimulation by PMA. These results indicate that GM-CSF activated extracellular acidification of TF-1 cells is caused by increases in sodium/proton antiporter activity and glycolysis, through protein kinase signalling pathways which can be both activated and down-regulated by PMA.
 ...
PMID:GM-CSF triggers a rapid, glucose dependent extracellular acidification by TF-1 cells: evidence for sodium/proton antiporter and PKC mediated activation of acid production. 767 63

Ligation of membrane immunoglobulin M (mIgM) receptor in the Ramos B-cell line induced tyrosine phosphorylation of several intracellular substrates, including the adaptor protein. Shc. Phosphorylated Shc could be seen to associate with Grb2 in a complex which included hSOS. Inasmuch as hSOS is involved in p21ras activation, we also demonstrated that mIgM ligation activated a Ras-dependent kinase cascade in which sequential activation of Raf-1 and MEK-1 culminates in the activation of p42 mitogen-activated protein (MAP) kinase (ERK-2). The tumour promoter and protein kinase C agonist, phorbol 12-myristate 13-acetate (PMA), also activated Raf-1, MEK-1, and MAP kinase in Ramos cells, but did not induce tyrosine phosphorylation of Shc or Shc/Grb2 association. Okadaic acid, another tumour promoter and serine/threonine phosphatase inhibitor, activated p42 MAP kinase without activating Raf-1 or MEK-1, suggesting the existence of a serine/threonine phosphatase which directly regulates MAP kinase activity.
 ...
PMID:The membrane immunoglobulin receptor utilizes a Shc/Grb2/hSOS complex for activation of the mitogen-activated protein kinase cascade in a B-cell line. 771 78

Stimulus-induced insulin secretion involves the activation of several protein kinases within the beta cell. Most prominent are protein kinase A, protein kinase C and calcium/calmodulin-dependent protein kinases. Protein kinase action is functionally antagonized by protein phosphatases. The four ubiquious serine/threonine protein phosphatases are termed PP-1, PP-2A, -2B and -2C. PP-1 and PP-2A are in vivo parts of major protein complexes. These complexes presumably regulate the phosphatase activity and direct the enzyme to its site of action. Therefore, PP-1 and -2A could play an important role in controlling intracellular signal transmission. Two different toxins, okadaic acid and calyculin A, both from marine invertebrates, were recently discovered and identified as potent and highly specific inhibitors of PP-1 and PP-2A. Both compounds emerged as very useful tools for studying intracellular phosphorylation events. We took advantage of these substances to investigate the significance of protein phosphatase action in stimulus-induced insulin secretion. To avoid major complexity, we confined our study to the cAMP and the phosphoinositide signal pathway. Okadaic acid alone evoked virtually no secretory response. cAMP-dependent secretion was markedly enhanced by 1 microM okadaic acid. The stimulatory effect of okadaic acid was strongly dependent on the concentration of cAMP analoga. In contrast, insulin release caused by the cholinergic agonist carbachol was not influenced by okadaic acid. Calyculin A (10 nM) slightly increased cAMP-induced secretion, but its high toxicity prohibited accurate interpretation of the data. Our findings support the idea that serine/threonine phosphatases act as important regulators in stimulus response coupling.(ABSTRACT TRUNCATED AT 250 WORDS)
 ...
PMID:Okadaic acid indicates a major function for protein phosphatases in stimulus-response coupling of RINm5F rat insulinoma cells. 781 3

Neonatal rat cortical astrocytes in primary culture synthesize and secrete nerve growth factor (NGF) in response to cytokines, growth factors, and activators of protein kinases. To further implicate a protein phosphorylation mechanism in the regulation of NGF expression, astrocytes were treated with okadaic acid and calyculin A, inhibitors of phosphoprotein phosphatases 1 and 2A. Okadaic acid dramatically increased both NGF mRNA content (50-fold) and NGF secretion (100-fold) in astrocytes, while calyculin A, which has a spectrum of phosphatase inhibitory activity different from okadaic acid, failed to augment NGF expression. The increased mRNA accumulation was due mainly to an increase (4-fold) in the half-life of the NGF mRNA following 9 or 24 h of treatment. Nuclear run-on assays indicated that okadaic acid also activated NGF gene transcription, which was preceded by an induction of c-fos and c-jun gene transcription. The induction of NGF expression by okadaic acid appeared independent from protein kinase C activity because down-regulating protein kinase C activity failed to decrease the okadaic acid stimulation. In contrast, interleukin-1 beta acted synergistically with okadaic acid to stimulate NGF secretion. The results indicate that okadaic acid profoundly stimulates NGF expression in astrocytes mainly by enhancing NGF mRNA stability and suggest important roles for phosphoprotein phosphatases in regulating NGF production.
 ...
PMID:Okadaic acid increases nerve growth factor secretion, mRNA stability, and gene transcription in primary cultures of cortical astrocytes. 789 Jul 29

alpha 1-Adrenergic (alpha 1-AR) agents stimulate NaCl(K) cotransport and phosphatidylinositol-4,5-bisphosphate [PtdIns(4,5)P2]-specific phospholipase C in human trachea and nasal polyp epithelial cells. One second messenger generated by PtdIns(4,5)P2 degradation is inositol trisphosphate. We now show that diglycerides (DG) are also generated during alpha 1-AR stimulation. In cells prelabeled with [3H]arachidonic acid, alpha 1-AR agents produced a biphasic DG generation in normal and cystic fibrosis (CF) cells that is blocked by pertussis toxin. The early DG peak closely paralleled PtdIns(4,5)P2 degradation, stimulation of cotransport by phorbol 12-myristate 13-acetate (PMA), and inhibition of cotransport by the protein kinase C (PKC) inhibitor staurosporine. This suggests that cotransporter activation requires PKC-protein phosphorylation. This possibility was tested using the protein phosphatase inhibitor okadaic acid. Okadaic acid elevated bumetanide-sensitive Cl efflux. Staurosporine also blocked > 63% of okadaic-acid-stimulated Cl transport. The late DG peak did not support hormone-stimulated cotransport. The results demonstrate that DGs are a pivotal link between alpha 1-AR stimulation and NaCl(K) cotransport activation with a role for PKC and protein phosphorylation. alpha 1-AR intracellular signaling mechanisms apparently operate normally in CF cells.
 ...
PMID:The role of protein kinase C in alpha-adrenergic regulation of NaCl(K) cotransport in human airway epithelial cells. 790 Aug 23

mRNA expression of the immediate-early gene NGFI-B was investigated in T cells during the G0/G1 transition as well as throughout the G1 phase. After stimulation of T lymphocytes with Con A or phorbol 12,13 dibutyrate (PDBu), NGFI-B gene expression showed an induction of at least sevenfold within 3 h of stimulation. Twenty-four h later, however, the level of NGFI-B transcripts had fallen to almost basal levels. Activation of the Ca2+ signaling pathway also produced an induction of this gene, although to a lesser extent than the one obtained after protein kinase C activation. Similar transient kinetics of NGFI-B mRNA were also observed after PDBu stimulation of G1 lymphoblasts. However, the induction of NGFI-B by IL-2 is dependent on the presence of cycloheximide. Con A-induced activation of NGFI-B gene expression was not overcome by cyclosporin A or by 8Br-cAMP, but was partially prevented by dexamethasone. In lymphoblasts, okadaic acid caused the induction of NGFI-B gene expression, indicating a role for the serine/threonine protein phosphatases PP1 and PP2A in the regulation of this gene in resting cells. Okadaic acid-induced NGFI-B transcripts were significantly more stable than PDBu-induced NGFI-B mRNA. Thus, the level of NGFI-B transcripts in T cells might be determined by the balance between the activities of several serine/threonine protein kinases and phosphatases. Together, these findings indicate that the transient induction of NGFI-B transcripts is associated with normal lymphocyte activation. Because the mRNA for NGFI-B codes for a zinc-finger DNA-binding protein, these results suggest that NGFI-B participates in transcriptional regulation during T cell activation.
 ...
PMID:Induction of NGFI-B gene expression during T cell activation. Role of protein phosphatases. 793 May 67

We previously reported that fetal calf serum-induced alkaline phosphatase activity is suppressed due to the activation of protein kinase C in osteoblast-like MC3T3-E1 cells (Miwa et al. (1991) Bone Miner. 14, 15-25; Kotoyori et al. (1994) Horm. Metab. Res. 26, 116-118). In the present study, we examined the effect of okadaic acid, a potent and specific inhibitor of protein phosphatase type 1 and 2A, on fetal calf serum-induced alkaline phosphatase activity in MC3T3-E1 cells. The pretreatment with okadaic acid enhanced the fetal calf serum-induced alkaline phosphatase activity in a dose-dependent manner in the range between 0.1 and 5 nM. 1-Norokadaone, a less potent analogue of okadaic acid, had little effect on the fetal calf serum-induced alkaline phosphatase activity. Okadaic acid partially reversed the suppression of fetal calf serum-induced alkaline phosphatase activity by 12-O-tetradecanoylphorbol-13-acetate, a protein kinase C activator. The effect of okadaic acid was dose-dependent in the range between 0.1 and 5 nM. The patterns of the dose-dependency of both okadaic acid effects on fetal calf serum-induced alkaline phosphatase activity and on the suppression by 12-O-tetradecanoylphorbol-13-acetate were similar. These results strongly suggest that protein phosphatase type 1 and/or 2A act as a regulator of alkaline phosphatase activity at a point downstream from protein kinase C in osteoblast-like cells.
 ...
PMID:Okadaic acid reverses the inhibitory effect of protein kinase C on alkaline phosphatase activity in osteoblast-like cells. 795 88

Many hormones regulate the rate of synthesis of phosphoenolpyruvate carboxykinase (PEPCK), the enzyme that governs the rate-limiting step in gluconeogenesis. In H4IIE rat hepatoma cells, glucocorticoids, retinoic acid and cyclic AMP (cAMP) increase PEPCK gene transcription whereas insulin and phorbol esters have the opposite effect. Insulin and phorbol esters are dominant as they prevent cAMP- and glucocorticoid-stimulated PEPCK gene transcription. In contrast, insulin and phorbol esters both stimulate transcription of gene 33 in the same H4IIE cells, with the same time course as seen for their inhibitory effect on PEPCK gene transcription. We now report that the protein phosphatase inhibitor, okadaic acid, mimics the action of insulin and phorbol esters on expression of both gene 33 and PEPCK gene in H4IIE cells. Okadaic acid stimulates gene 33 mRNA accumulation whereas it inhibits cAMP- and glucocorticoid-stimulated PEPCK mRNA accumulation. The effect of okadaic acid on the PEPCK gene is mediated through the PEPCK promoter as, in a cell line, HL1C, stably transfected with a PEPCK-chloramphenicol acetyltransferase (CAT) fusion gene, okadaic acid inhibits cAMP- and glucocorticoid-stimulated CAT expression. Desensitization of the protein kinase C pathway by exposure to phorbol 12-myristate 13-acetate for 16 h abolishes the subsequent action of the phorbol ester but does not markedly affect the inhibition of cAMP- and glucocorticoid-stimulated CAT expression by insulin or okadaic acid. Even though insulin and okadaic acid appear to repress PEPCK gene expression through a pathway initially distinct from that used by phorbol esters, transient-transfection studies show that the final target of the action of okadaic acid, insulin and phorbol ester is the same DNA element.
 ...
PMID:Comparison of the effects of insulin and okadaic acid on phosphoenolpyruvate carboxykinase gene expression. 798 Apr 40

To determine whether protein phosphatases can affect collagen synthesis, we examined the effect of okadaic acid, a potent specific inhibitor of protein phosphatases 1 and 2A, on collagen synthesis. Okadaic acid significantly decreased the [3H]proline incorporation into the collagenase-digestible protein and the percent collagen synthesis. These effects were synergistic with phorbol myristate acetate (PMA). The time course study showed that okadaic acid inhibited collagen synthesis after a 12 h treatment while PMA inhibited at 3 h. Down-regulation of protein kinase C by chronic treatment with PMA did not abrogate the okadaic acid-dependent inhibition. These results provide evidence for the involvement of protein phosphatases in the regulation of collagen synthesis.
 ...
PMID:Selective inhibition of collagen synthesis by okadaic acid in cultured human fibroblasts. 812 9

The insulin modulation of Na-H antiport in rat hepatocytes was studied using the fluorescent, pH-sensitive intracellular probe, 2',7' bis (carboxyethyl)-5(6)-carboxyfluorescein (BCECF). Our data show that insulin stimulates the Na-H antiport. The dose-response of insulin effect shows a behavior typical of other insulin responses: a maximum in the physiological range (1 nM) and smaller effects at higher and lower hormone concentrations. The time-course of activation is very fast at high hormone concentrations and slow, but reaching a higher value, for the physiological concentrations (0.26 +/- 0.05 and 0.18 +/- 0.022 pH units for 1 nM and 1 microM insulin respectively). The use of phorbol, 12-myristate, 13-acetate (PMA), a potent activator of protein kinase C and its inhibitor staurosporine, and the inhibitor of tyrosine kinase erbstatin analog, suggests that both protein kinase C and tyrosine kinase could be involved in the mechanism leading to Na-H antiport activation by insulin. We suggest that the activation of the antiport involves the two pathways depending on the hormone concentration. In particular, protein kinase C would mediate the effects of high hormone concentrations, acting as a growth factor, since staurosporine fully inhibited insulin 1 microM, but only partially 1 nM effects, and tyrosine kinase would mediate the effect of insulin 1 nM and only partially 1 microM. Okadaic acid 1 microM, a potent inhibitor of protein phosphatases, mimicked the hormone effects on the antiport and abolished the different time-course due to hormone concentration, suggesting a role of kinases and phosphatases in the signal transduction. The effect of all activators was abolished by amiloride analog, 5-(N-ethyl-N-isopropyl) amiloride (EIPA), confirming the specificity of these effects.
 ...
PMID:Modulation of the Na-H antiport by insulin: interplay between protein kinase C, tyrosine kinase, and protein phosphatases. 816 61


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>