Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.1.3.16 (calcineurin)
17,112 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Patients with non-insulin-dependent diabetes mellitus (NIDDM) had an impaired capability to activate exogenous ATP.Mg-dependent protein phosphatase in lymphocytes compared with nondiabetic subjects. More importantly, the impaired protein phosphatase activation in the lymphocytes of patients with NIDDM could be consistently and completely restored to normal by exogenous pure protein kinase FA (the activating factor of ATP.Mg-dependent protein phosphatase), indicating that the molecular mechanism for the impaired protein phosphatase activation in patients with NIDDM is due to a functional loss of kinase FA. By contrast, both NIDDM patients and nondiabetic subjects had similar levels of total cell proteins and spontaneously active protein phosphatase activity in their lymphocytes, indicating that the dysfunction of kinase FA in patients with NIDDM is very specific. Statistical analysis further revealed that the lymphocytes isolated from 21 nondiabetic subjects contained high levels of FA activity (148 +/- 22 mU/mg cell protein), whereas, the lymphocytes of 21 patients with NIDDM contained low levels of FA activity (50 +/- 22 mU/mg), indicating statistically significant differences in FA activity between diabetic patients and nondiabetic subjects. This is the first report providing initial evidence that patients with NIDDM may statistically have a common impairment in the protein phosphatase activation in their lymphocytes and that the molecular mechanism for this defect is due to a biochemical dysfunction of protein kinase FA, a biological mediator for both insulin and epidermal growth factor.
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PMID:Dysfunction of insulin mediator protein kinase FA in lymphocytes of patients with NIDDM. 130 56

The mitogen-activated protein (MAP) kinases, a family of 40-45-kDa kinases whose activation requires both tyrosine and threonine/serine phosphorylations, are suggested to play key roles in various phosphorylation cascades. A previous study of Krebs and co-workers (Ahn, N. G., Seger, R., Bratlien, R. L., Diltz, C. D., Tonks, N. K., and Krebs, E. G. (1991) J. Biol. Chem. 266, 4220-4227) detected an activity in epidermal growth factor (EGF)-stimulated 3T3 cells that can stimulate inactive MAP kinases. We observed this activity in rat 3Y1 cells treated with various mitogenic factors and in PC12 cells treated with nerve growth factor (NGF). Its kinetics of activation and deactivation following EGF or NGF stimulation roughly paralleled that of MAP kinase. The MAP kinase activator required the presence of ATP and a divalent cation such as Mn2+ and Mg2+ and was inactivated by phosphatase 2A treatment in vitro. This activator has been isolated from EGF-stimulated 3Y1 cells by sequential chromatography and identified as a 45-kDa monomeric protein. It was able to activate mammalian and Xenopus MAP kinases in vitro and was very similar to Xenopus M phase MAP kinase activating factor, which was purified previously from mature oocytes (Matsuda, S., Kosako, H., Takenaka, K., Moriyama, K., Sakai, H., Akiyama, T., Gotoh, Y., and Nishida, E. (1992) EMBO J. 11, 973-982), in terms of its functional, immunological, and physicochemical properties. Thus, the same or a similar upstream activating factor may function in mitogen-induced and M phase-promoting factor-induced MAP kinase activation pathways.
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PMID:A mitogen-activated protein (MAP) kinase activating factor in mammalian mitogen-stimulated cells is homologous to Xenopus M phase MAP kinase activator. 132 14

Extracellular signals that promote cell growth activate cascades of protein kinases. The kinases are dephosphorylated and deactivated by a single type-2A protein phosphatase. The catalytic subunit of type-2A protein phosphatase was phosphorylated by tyrosine-specific protein kinases. Phosphorylation was enhanced in the presence of the phosphatase inhibitor okadaic acid, consistent with an autodephosphorylation reaction. More than 90% of the activity of phosphatase 2A was lost when thioadenosine triphosphate was used to produce a thiophosphorylated protein resistant to autodephosphorylation. Phosphorylation in vitro occurred exclusively on Tyr307. Phosphorylation was catalyzed by p60v-src, p56lck, epidermal growth factor receptors, and insulin receptors. Transient deactivation of phosphatase 2A might enhance transmission of cellular signals through kinase cascades within cells.
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PMID:Regulation of protein serine-threonine phosphatase type-2A by tyrosine phosphorylation. 132 71

Growth factors regulate cellular proliferation and differentiation by activating plasma membrane tyrosine kinase receptors and triggering a cascade of events mediated by intracellular signaling proteins. The mechanism underlying growth factor modification of cellular functions, such as gap-junctional communication (gjc), has not been established clearly. Addition of epidermal growth factor (EGF) to T51B rat liver epithelial cells resulted in the rapid activation of EGF receptor tyrosine kinase activity followed by a transient dose-dependent disruption of gjc. This change did not result from the gross disturbance of membrane gap junction plaques as measured by immunofluorescence microscopy, but instead correlated with markedly elevated phosphorylation of the connexin43 (cx43) gap junction protein, a profound shift to predominantly phosphorylated forms of cx43, and the appearance of a novel phosphorylated cx43 protein. These changes in cx43 phosphorylation involved only serine residues. On restoration of gjc, these alterations in cx43 phosphorylation reverted to the pre-EGF treatment state. Both events were inhibited by the serine/threonine protein phosphatase inhibitor, okadaic acid. Therefore, unlike the case for pp60v-src, EGF-induced disruption of gjc is not associated with tyrosine phosphorylation of cx43, but instead may result from phosphorylation of cx43 by activated intracellular signaling serine protein kinase(s).
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PMID:Epidermal growth factor disrupts gap-junctional communication and induces phosphorylation of connexin43 on serine. 132 98

Okadaic acid, a phosphatase inhibitor from a marine organism, mimics tumor necrosis factor/interleukin-1 (TNF/IL-1) in inducing changes in early cellular protein phosphorylation. A total of approximately 116 proteins exhibit significant and concordant changes in phosphorylation or dephosphorylation within 15 min in human fibroblasts activated by either okadaic acid, TNF, or IL-1. The fidelity of this mimicry by okadaic acid extends to the phosphorylation of the 27 hsp complex, stathmin, eIF-4E, myosin light chain, nucleolin, epidermal growth factor receptor, and other cdc2-kinase substrates (c-abl, RB, and p53). The okadaic acid-induced pattern of protein phosphorylation is distinct from that observed in cells treated with phorbol 12-myristate 13-acetate or with ligands like epidermal growth factor, cyclic AMP agonists, bradykinin, or interferons. Like TNF, okadaic acid also induces the transcription of immediate early response genes like c-jun and Egr-1 as well as the interleukin-6 genes. The overall early effects of okadaic acid uniquely parallel those of TNF/IL-1 and not those of other cytokines or ligands. Regulation of protein phosphatase inhibition is discussed as a mechanism for TNF/IL-1 signal transduction.
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PMID:Okadaic acid mimics multiple changes in early protein phosphorylation and gene expression induced by tumor necrosis factor or interleukin-1. 137 Apr 82

Human prostatic acid phosphatase (PAcP) is a tissue-specific differentiation antigen and is the major phosphotyrosyl (p-tyr) protein phosphatase in normal differentiated prostate epithelial cells. In prostate carcinomas, cellular PAcP has a low expression. We examined the expression of cellular PAcP activity and its correlation with cell growth that may lead us to understand the role of tyrosine phosphorylation in human prostate cells. LNCaP cells, which expressed the highest cellular PAcP activity, had the slowest growth rate and the lowest p-tyr level among three human prostate carcinoma cell lines: LNCaP, DU145, and PC-3. This inverse correlation was further examined in LNCaP cells, since these cells remain hormone-sensitive. Androgen, a classical stimulator of prostate cells, stimulated the growth of LNCaP cells while cellular PAcP activity decreased and p-tyr levels increased. This phenomenon was also observed when cells were treated with epidermal growth factor and fetal bovine serum. Both epidermal growth factor and fetal bovine serum stimulated the growth of LNCaP cells whereas cellular PAcP activity decreased. Furthermore, when cell growth was arrested at low temperatures (23 degrees C), cellular PAcP activity was elevated. To establish the relationship of cellular PAcP activity with cell growth rate, we transfected a complementary DNA encoding the full length PAcP protein into another human prostate carcinoma line, PC-3, that lacks endogenous PAcP. Two stable transfectants, designated PC-18 and PC-416 cells, were obtained and shown to express PAcP mRNA transcribed from the transfected complementary DNA. The expression of PAcP activity in PC-416 cells, but not PC-18 cells, was associated with a lower p-tyr level and a slower growth rate than control cells transfected with the expression vector alone. In conclusion, in LNCaP cells, the stimulated cell growth is associated with an increased p-tyr level and a decreased cellular PAcP activity. In PAcP complementary DNA-transfected PC-416 cells, the low level of p-tyr corresponds to a slow growth rate.
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PMID:Expression of human prostatic acid phosphatase activity and the growth of prostate carcinoma cells. 138 Aug 86

PC12 pheochromocytoma cells contain at least two different and separable kinases that phosphorylate the S6 protein of the ribosomes. The activity of one of these S6 kinases is increased by treatment of the cells with nerve growth factor and of the other by treatment with epidermal growth factor. Okadaic acid increases the activity of the nerve growth factor-sensitive S6 kinase. The data suggest that the nerve growth factor-sensitive S6 kinase is activated by phosphorylation on serine or threonine residues and is inactivated by either phosphatase 1 or phosphatase 2A, probably the latter.
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PMID:Okadaic acid stimulates the activity of the nerve growth factor-sensitive S6 kinase of PC12 cells. 164 6

Okadaic acid, a potent tumor promoter and inhibitor of phosphoserine/threonine protein phosphatases 1 and 2A, produces a large increase in epidermal growth factor (EGF) receptor phosphorylation in several cell types. The increases are limited to phosphoserine and phosphothreonine residues. 12-O-Tetradecanoylphorbol-13-acetate (TPA), a distinct tumor promoter and protein kinase C activator, also induces serine/threonine phosphorylation of the EGF receptor and is known to modulate receptor functions. Comparison of okadaic acid and TPA influences on the EGF receptor show significant differences. Okadaic acid did not promote phosphorylation of Thr-654, a major site of TPA-induced phosphorylation. However, other sites of phosphorylation were similar for the two tumor promoters. In vitro experiments with purified protein phosphatase 2A demonstrate the insensitivity of Thr-654 phosphorylation, which regulates EGF receptor function, to dephosphorylation by this okadaic acid-sensitive protein phosphatase. In contrast to TPA, okadaic acid did not attenuate the tyrosine kinase activity or ligand binding capacity of the EGF receptor. However, okadaic acid did produce a decrease in EGF-stimulated inositol phosphate formation in a manner distinct from that of TPA.
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PMID:Okadaic acid-induced hyperphosphorylation of the epidermal growth factor receptor. Comparison with receptor phosphorylation and functions affected by another tumor promoter, 12-O-tetradecanoylphorbol-13-acetate. 165 56

Addition of tumor promoting phorbol esters, such as phorbol 12-myristate 13-acetate (PMA), to many cell lines results in a decrease of 125I-epidermal growth factor (EGF) binding and increased serine/threonine phosphorylation of the EGF receptor in a process termed transmodulation. It is, however, unclear whether or not receptor phosphorylation is causally related to the inhibition of high affinity EGF binding. We have investigated the significance of phosphorylation/dephosphorylation events in the mechanism of PMA-induced transmodulation using the adenylate cyclase activator cholera toxin and the serine/threonine protein phosphatase inhibitor okadaic acid. In Rat-1 fibroblasts treated at 37 degrees C, PMA induced a rapid decrease in EGF binding which persisted for 3 hours. In contrast, cells exposed to PMA in the presence of cholera toxin exhibited a marked recovery of binding within 60 minutes. The PMA-stimulated decrease in binding correlated with a rapid increase in the phosphorylation state of the EGF receptor. While phosphorylation of the receptor was sustained at an elevated level for at least three hours in cells receiving PMA alone, EGF receptor phosphorylation decreased between 1 and 3 hours in cells treated with PMA and cholera toxin. Furthermore, the cholera toxin-stimulated return of EGF binding was inhibited by treatment with the phosphatase inhibitor okadaic acid. These results suggest that a cholera toxin-activated phosphatase can increase binding capacity of the transmodulated EGF receptor in Rat-1 cells. Cholera toxin treatment elicited a qualitatively similar response in cells transmodulated by platelet-derived growth factor (PDGF). Okadaic acid antagonized the natural return of binding observed in cells stimulated with PDGF alone, indicating that a dephosphorylation event may be required for the recovery of normal EGF binding after receptor transmodulation.
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PMID:Regulation of the transmodulated epidermal growth factor receptor by cholera toxin and the protein phosphatase inhibitor okadaic acid. 165 15

The efficiency of efflux of rapidly labeled poly(A)-containing mRNA from isolated rat liver nuclei was found to be modulated by insulin and epidermal growth factor (EGF) in a biphasic but opposite way. At physiological concentrations (10 pM insulin and 1 pM EGF), maximal stimulation of the transport rate by insulin (to 137%) and maximal inhibition by EGF (to 69%) were obtained; at higher concentrations (greater than 100 pM and greater than 10 pM, respectively), the amount of poly(A)-containing mRNA released into the postnuclear supernatant was nearly identical with the level found in untreated nuclei (= 100%). Using mRNA entrapped into closed nuclear envelope (NE) vesicles as a model system, it was found that the modulation of nuclear efflux of mRNA by the two growth factors occurs at the level of translocation through the nuclear pore. The NE nucleoside-triphosphatase (NTPase) activity, which is thought to mediate nucleocytoplasmic transport of at least some mRNAs, responded to insulin and EGF in the same manner as the mRNA transport rate. The increase in NTPase activity caused by insulin and the decrease in NTPase activity caused by EGF were found to be due to changes of the maximal catalytic rate; the Michaelis constant of the enzyme remained almost constant. Investigating the effect of the two growth factors on transport of specific mRNAs, poly(A)-containing actin mRNA was found to display the same alteration in efflux rate as rapidly labeled, total poly(A)-containing mRNA. In contrast, efflux of histone H4 mRNA, which lacks a 3'-poly(A) sequence, decreased in response to insulin and reached minimum levels at the same concentration at which maximum levels of actin mRNA transport rate were obtained. Studying the mechanism of action of insulin and EGF on NE mRNA translocation system, insulin was found to cause an enhancement of NE-associated phosphoprotein phosphatase activity, resulting in a dephosphorylation of the NE poly(A) binding site (= mRNA carrier) and, hence, in a decrease in its affinity to poly(A) [the poly(A) binding affinity of the poly(A)-recognizing mRNA carrier within the envelope is increased after phosphorylation]. EGF, on the other hand, stimulated the protein kinase, which phosphorylates the carrier, and, hence increased the NE poly(A) binding affinity. Because the stage of phosphorylation of the mRNA carrier (which is coupled with the NTPase within the intact NE structure) is inversely correlated with the activity of the NTPase, an enhancement of poly(A)-containing mRNA transport rate by insulin and an inhibition by EGF are observed.
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PMID:Differential effect of insulin and epidermal growth factor on the mRNA translocation system and transport of specific poly(A+) mRNA and poly(A-) mRNA in isolated nuclei. 197 Sep 36


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