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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have employed an acute explant system of the rat hypothalamus in vitro, as previously described, to examine the role of calcium and calmodulin in the release of corticotrophin-releasing hormone-41 (CRH-41). Release of CRH-41, as determined by radioimmunoassay, was stimulated in a dose-dependent manner by the membrane-depolarizing agents KCl and veratridine. Stimulation was also observed with the calcium ionophore A23187. The calcium channel blocker verapamil (1-100 mumol/l) inhibited both KCl- and veratridine-induced release in a dose-dependent manner (maximum inhibition of 75% and 60% respectively), thus providing further evidence that calcium entry is required for secretion of CRH-41 following membrane depolarization. Trifluoperazine (1-100 mumol/l), an inhibitor of calmodulin-calcium interaction, decreased both KCl- and veratridine-evoked CRH-41 secretion in a dose-dependent fashion (maximum inhibition of 50% and 30% respectively). Similarly, phenytoin, a calmodulin-dependent kinase inhibitor, in the concentration range of 1-100 mumol/l, also decreased depolarization-induced CRH-41 release in a dose-dependent manner. The basal release of CRH-41 was unaffected by either treatment. Finally, both calmodulin inhibitors (10 mumol/l) decreased CRH-41 release induced by the calcium ionophore A23187 (10 mumol/l). These data provide evidence for the role of calcium in membrane depolarization-induced stimulus-secretion coupling of rat hypothalamic CRH-41. Furthermore, inhibition of the stimulatory responses by two separate classes of calmodulin inhibitors suggests a role for calmodulin, at least in part, in this process.
J Mol Endocrinol 1991 Aug
PMID:Involvement of calmodulin in depolarization-induced release of corticotrophin-releasing hormone-41 from the rat hypothalamus in vitro. 189 43

Calcineurin was discovered as an inhibitor of calmodulin stimulated cyclic AMP phosphodiesterase and its ability to act as a calmodulin binding protein largely explains its inhibitory action on calmodulin regulated enzymes. Recent studies establish calcineurin as the enzyme protein phosphatase whose activity is regulated by calmodulin and a variety of divalent metals. In this work, we have investigated the effects of several agents including sulfhydryl agents, trifluoperazine (a calmodulin antagonist), PPi, NaF and orthovanadate and of tryptic proteolysis on the calcineurin inhibition of cyclic AMP phosphodiesterase (called inhibitory activity) and on protein phosphatase activity. Inhibitors for sulfhydryl groups (pHMB, NEM) inhibited phosphatase activity without any effect on the inhibitory activity. Dithioerythritol completely reversed the inhibition by pHMB. Limited proteolysis of calcineurin caused an activation of basal phosphatase activity with a complete loss of inhibitory activity. Phosphatase activity of the proteolyzed calcineurin was not stimulated by calmodulin. The presence of calmodulin along with calcineurin during tryptic digestion appeared to preserve the stimulation of phosphatase by Ca2(+)-calmodulin. [3H]-Trifluoperazine (TFP) was found to be incorporated irreversibly into calcineurin in the presence of ultraviolet light. This incorporation was evident into the A and B subunits of calcineurin. TFP-caused a decrease in the phosphatase activity and an increase in its inhibitory activity. [3H]-TFP incorporation into the A subunit was drastically decreased in the proteolyzed calcineurin. This was also true when the [3H]-TFP incorporated calcineurin was subjected to tryptic proteolysis. The incorporation into the B unit was essentially unaffected in the trypsinized calcineurin. Phosphatase activity was inhibited by orthovanadate, NaF, PPi, and EDTA. Inhibitions by these compounds were more pronounced when the phosphatase was determined in the presence of Ca2(+)-calmodulin than in their absence.
Mol Cell Biochem 1990 Sep 03
PMID:Effects of sulfhydryl agents, trifluoperazine, phosphatase inhibitors and tryptic proteolysis on calcineurin isolated from bovine cerebral cortex. 217 99

The kinetic properties and inhibitor sensitivity of human sperm phospholipase A2 (PLA2; EC 3.1.1.4) were studied. Phospholipase activity was isolated from human spermatozoa by acid extraction. Hydrolysis of dipalmitoyl phosphatidylcholine was specific to the sn-2 position. Activity was sensitive to product inhibition (60% inhibition by 0.1 mM lysophosphatidylcholine). The effects of Ca2+ and sodium deoxycholate on enzyme activity were biphasic; maximal activities were observed at 0.5 mM concentration of each agent. PLA2 was stimulated (135%) by 3% dimethylsulfoxide and was inhibited by elevated ionic strength (approximately 70% inhibition with either 0.2 M NaCl or 0.2 M KCl). Two molecular forms of PLA2 were kinetically distinguishable, one with an apparent Michaelis constant and maximal reaction velocity of 3.0 microM and 0.64 mlU/mg protein and the other with respective constants of 630 microM and 32.0 mlU/mg protein. Both forms of the enzyme were Ca2+ dependent and heat stable; however, the low-Km activity was less resistant to 60 degrees C preincubation at pH 7.5 (28% inactivation of low-Km activity after 45 min, as compared to no effect on high-Km activity). Quinacrine was a noncompetitive PLA2 inhibitor with Kis for low- and high-Km activities of 0.42 mM and 0.49 mM, respectively. Trifluoperazine (calmodulin antagonist) inhibited the high-Km activity noncompetitively (Ki = 87 microM) and the low-Km activity by a mechanism consistent with the removal of a nonessential activator. Dissociation and rate constants for inactivation of low- and high-Km activities by p-bromophenacyl bromide were 0.28 mM and 0.032 min-1, and 0.73 mM and 0.066 min-1, respectively. PLA2 was inhibited by p-nitrophenyl-p'-guanidinobenzoate, at higher concentrations (10(-4)-10(-3) M) than required to inhibit trypsinlike proteinases; p-aminobenzamidine, another potent trypsin/acrosin inhibitor, stimulated (approximately 40%) PLA2 at concentrations from 2-5 mM but inhibited PLA2 (40-50%) at a concentration of 10 mM. MnCl2 (5mM) inhibited low- and high-Km PLA2 activities by 77% and 76%, respectively. Quinacrine (0.4 mM), trifluoperazine (20 microM), p-bromophenacyl bromide (20 microM), and MnCl2 (5 mM) were tested as inhibitors of the ionophore A23187-induced human acrosome reaction. Inhibition was noted only with quinacrine (32%) and MnCl2 (93%). The effect of MnCl2 was restricted to an interaction with A23187, rather than with PLA2; p-Bromophenacyl bromide inhibited (P less than 0.05) PLA2 (29%) when added to intact spermatozoa but had no effect on the acrosome reaction. PLA2 inhibition was poorly correlated with the acrosome reaction.(ABSTRACT TRUNCATED AT 400 WORDS)
Mol Reprod Dev 1990 Dec
PMID:Characterization and inhibitor sensitivity of human sperm phospholipase A2: evidence against pivotal involvement of phospholipase A2 in the acrosome reaction. 226 93

Pharmacologic agents reported to inhibit prolactin secretion by GH3 pituitary cells were observed to inhibit protein synthesis by these cells in a Ca2+-dependent manner. The possibility that these substances exert their effects on protein synthesis by restricting intracellular Ca2+ availability was explored. Trifluoperazine and chlorpromazine at concentrations that inhibit amino acid incorporation reduced uptake of 45Ca2+ by intact cells approximately 30% under nondepolarizing conditions. Increased extracellular K+ (30 mM), which depolarizes the membrane and opens the voltage-dependent Ca2+ channel of GH3 cells, produced a 2-fold increase in 45Ca2+ uptake; phenothiazines fully suppressed this effect of K+. Nifedipine, verapamil, ergotamine, bromocriptine, (+)- and (-)-butaclamol, and calmidazolium were also effective in inhibiting 45Ca2+ uptake under depolarizing and nondepolarizing conditions. The membrane potential of either depolarized or nondepolarized cells, as determined by [3H]tetraphenylphosphonium+ distribution, was not affected significantly by secretory inhibitors. Increased extracellular K+ altered protein synthesis by GH3 cells in a biphasic manner. Amino acid incorporation by cells incubated at low extracellular Ca2+ concentrations was stimulated by K+, whereas incorporation by cells in high Ca2+ medium was inhibited by K+. Trifluoperazine, chlorpromazine, nifedipine, and bromocriptine suppressed both effects of K+ on protein synthesis. It is proposed that these antagonists of secretion inhibit protein synthesis by GH3 cells through blockade of voltage-dependent Ca2+ channels.
Mol Pharmacol 1986 Apr
PMID:Mechanisms of action of inhibitors of prolactin secretion in GH3 pituitary cells. II. Blockade of voltage-dependent Ca2+ channels. 242 34

Trifluoperazine (TFP) (50 mg/kg ip) administration to rats 6 or 10 hr after CCl4 (1 ml/kg ip in olive oil) significantly prevented liver necrosis but not fatty liver caused by the hepatotoxin at 24 hr as evidenced by either histology or electron microscopy. TFP given 6 hr after CCl4 significantly decreased the CCl4-induced increases in liver calcium content. TFP raised four to five times the liver glycogen content in control rats but was unable to modify decreased glycogen content of CCl4 poisoned animals. TFP administration increased phospholipid and protein synthesis as evidenced by studies on 32P incorporation into microsomal phospholipid and by experiments on [14C]leucine incorporation in microsomal protein fractions from control rat livers. No significant changes were observed in microsomal phospholipid degradation as studied by decay of label from 32P-prelabeled microsomal lipids or in increased protein degradation as evidenced by decay of label from [14C-guanidino]arginine-prelabeled microsomal proteins found in livers of control rats after TFP treatment. Electron microscopy observations of liver from control animals treated with TFP evidenced accumulation of glycogen in areas close to smooth endoplasmic reticulum (SER); large Golgi areas with an abundant number of lysosomes, and minor dilatation effects on the rough endoplasmic reticulum (RER) and nuclear membrane. Results suggest that TFP preventive effects might be due to the anticalmodulin actions of this drug.
Exp Mol Pathol 1988 Jun
PMID:Further studies on the late preventive effects of the anticalmodulin trifluoperazine on carbon tetrachloride-induced liver necrosis. 337 54

Post-transcriptional protein synthesis by GH3 cloned pituitary cells, which secrete prolactin and growth hormone, is dependent on Ca2+. The effects of antagonists of prolactin secretion were examined on overall protein synthesis in GH3 cells as a function of cellular Ca2+ depletion and restoration at varying concentrations of extracellular Ca2+. Leucine incorporation by Ca2+-depleted cells during short incubations was reduced by 80-90%. Trifluoperazine at micromolar concentrations inhibited leucine incorporation in a Ca2+-dependent manner. The extent of inhibition varied with extracellular Ca2+ concentration and was fully reversed at higher Ca2+ concentrations. Similar patterns of inhibition of leucine incorporation were observed with nifedipine, verapamil, calmidazolium, chlorpromazine, bromocriptine, ergotamine, and the (+)- and (-)-isomers of butaclamol, but dopamine, apomorphine, and chlorpromazine sulfoxide were not inhibitory. Muscarinic agonists decreased incorporation in a Ca2+-dependent manner, but lesser degrees of inhibition were obtained. Inhibitions were observed for a broad spectrum of polypeptide species, could not be explained by effects on Mg2+ availability or amino acid uptake, and were rapidly and fully reversed by Ca2+. Production of prolactin and growth hormone was decreased by secretory inhibitors to the same extent and with the same Ca2+ concentration dependence as was observed for inhibition of amino acid incorporation. It is proposed that these substances inhibit protein synthesis in GH3 cells through alterations in intracellular Ca2+ metabolism rather than through mechanisms mediated by calmodulin or dopamine receptors.
Mol Pharmacol 1986 Apr
PMID:Mechanisms of action of inhibitors of prolactin secretion in GH3 pituitary cells. I. Ca2+-dependent inhibition of amino acid incorporation. 370 60

Trifluoperazine and chlorpromazine inhibited in a dose-dependent manner the stimulation of glycogenolysis, gluconeogenesis, and ureogenesis due to alpha 1-adrenergic stimulation in rat hepatocytes. In contrast, the antipsychotic agents were unable to block the inhibition of adenylate cyclase due to alpha 2-adrenergic activation in hamster adipocytes. Binding experiments showed that trifluoperazine and chlorpromazine at low concentrations displaced tritiated dihydroergocryptine binding from rat liver membranes (alpha 1-adrenergic sites), whereas very large concentrations of the phenothiazine derivatives were required to displace dihydroergocryptine from hamster adipocyte membranes (alpha 2-adrenergic sites). It is concluded that chlorpromazine and trifluoperazine are much more potent at alpha 1- than at alpha 2-adrenergic receptors. The use of rat hepatocytes and hamster adipocytes to study the alpha-adrenergic subtype selectivity of drugs is proposed.
Mol Pharmacol 1983 Jan
PMID:Trifluoperazine and chlorpromazine antagonize alpha 1- but not alpha2- adrenergic effects. 613 46

A cal1-1 mutant of the yeast Saccharomyces cerevisiae showing Ca2+-dependent growth was isolated. Its growth continued exponentially in Ca2+-rich medium, but stopped in Ca2+-poor medium at 37 degrees C. Mg2+ ions could not replace Ca2+ ions. In Ca2+-poor medium, the mutant cells stopped growing homogeneously at the stage of cell division cycle with a tiny bud. The nucleus in these arrested cells was in the G2 stage, judging from observation after nuclear staining and determination of the DNA content. Trifluoperazine-dependent pseudorevertants, which could grow in the presence of 20 microM to 80 microM trifluoperazine in Ca2+-poor medium at 37 degrees C, were obtained from this cal1-1 mutant. The suppressor mutation, tfr1, itself conferred trifluoperazine resistance. Other calmodulin inhibitors structurally unrelated to trifluoperazine had similar effects to trifluoperazine on these pseudorevertants. These results suggest that Ca2+ ions and a calmodulin play important roles in the yeast cell division cycle at the stage of bud growth and nuclear division.
Mol Gen Genet 1984
PMID:Genetic study of the role of calcium ions in the cell division cycle of Saccharomyces cerevisiae: a calcium-dependent mutant and its trifluoperazine-dependent pseudorevertants. 636 73

The nature of the Ca2+ requirement of lymphocyte-mediated cytolysis (LMC) has been explored pharmacologically with a number of putative calmodulin antagonists. N-(6-Aminohexyl)-5-chloro-1-naphthalenesulfonamide (W-7), N-(6-aminohexyl)-1-naphthalenesulfonamide (W-5), trifluoperazine, and chlorpromazine were found to inhibit LMC (IC50 values = 8.9, approximately 50, 7.4, and 9.4 microM, respectively) at concentrations which were not detectably toxic to either the effector or the target cell. Pimozide inhibited LMC by 50% at 15 microM but caused a substantial decrease in lymphocyte ATP content and viability at this concentration. 1-[Bis(p-chlorophenyl)methyl]-3-[2,4-dichloro-beta-(2,4-dichlorobenzy loxy) phenethyl]imidazolium chloride (R 24 571, calmidazolium), which has been reported to be the most potent antagonist of isolated calmodulin, caused a marked decrease in lymphocyte ATP content and viability at concentrations greater than 4 microM and inhibited LMC only slightly at similar concentrations. Trifluoperazine sulfoxide and chlorpromazine sulfoxide were not inhibitory to LMC at less than or equal to 20 microM. LMC was inhibited in a sustained manner when cytolytic lymphocytes, but not target cells, were pretreated separately with W-7 or chlorpromazine at 37 degrees and were then washed free of exogenous drug prior to the start of the LMC assay. The above cellular effects of the calmodulin antagonists were reduced in magnitude when the serum concentration in the culture medium was increased (from 5% to 20%). The inhibition of LMC by micromolar concentrations of W-7, trifluoperazine, and chlorpromazine, as well as the relative inactivities of W-5 versus W-7 and of the sulfoxide derivatives of trifluoperazine and chlorpromazine, are consistent with calmodulin's being a lymphocyte receptor whose occupancy by Ca2+ is required for the performance of this cytolytic function. However, this conclusion must be tempered by the finding that even W-7, trifluoperazine, and chlorpromazine can exert nonspecific effects on the energy metabolism and viability of the cytolytic lymphocytes at concentrations of drug severalfold higher than those required to inhibit LMC.
Mol Pharmacol 1984 Sep
PMID:Effects of calmodulin antagonists on immune mouse lymphocytes. 648 75

In the insulin-secreting beta cell line RINm5F, sodium fluoride stimulated exocytosis in a concentration (5-15 mM)- and temperature-dependent manner. Depletion of aluminum with the chelator deferoxamine or addition of aluminum to the buffer failed to affect the NaF-stimulated insulin release. This suggests that stimulation of heterotrimeric G proteins or inhibition of phosphatases or other enzymes by fluoroaluminate, an analog of the phosphate moiety, is not involved in the insulinotropic action of NaF. Removal of extracellular Ca2+ suppressed the NaF-stimulated insulin release. However, nitrendipine, a blocker of L-type voltage-dependent Ca2+ channels, did not inhibit the NaF-stimulated insulin release and NaF did not cause any changes in the cytosolic free calcium concentration ([Ca2+]i). Decreasing [Ca2+]i with thapsigargin or increasing [Ca2+]i with ionomycin or a depolarizing concentration of KCl resulted in suppression or enhancement of NaF-stimulated insulin release, respectively. Furthermore, NaF enhanced Ca(2+)-induced insulin release in electrically permeabilized RINm5F cells. These findings indicate that the effect of NaF on exocytosis is dependent on [Ca2+]i, although NaF itself does not change [Ca2+]i. Inhibitors of protein kinase C, such as staurosporine and bisindolylmaleimide, in concentrations sufficient to block the effects of phorbol esters, did not attenuate the NaF-stimulated insulin release. Neither cellular cAMP content nor [3H]arachidonic acid release was increased by NaF. NaF-stimulated insulin release was synergistically enhanced by the activation of protein kinases A and C. Finally, trifluoperazine, an inhibitor of calmodulin and other Ca(2+)-binding proteins, inhibited the insulinotropic action of NaF in a concentration-dependent manner. Trifluoperazine (50 microM) and W-7 (100 microM) nullified the 10 mM NaF-stimulated insulin release. It is concluded that NaF evokes exocytosis by a novel mechanism of sensitization to Ca2+, possibly on a Ca(2+)-responsive protein that is sensitive to trifluoperazine and W-7, leading to exocytosis. Protein kinases A and C also act at this site or at a more distal point.
Mol Pharmacol 1995 Mar
PMID:Sodium fluoride stimulates exocytosis at a late site of calcium interaction in stimulus-secretion coupling: studies with the RINm5F beta cell line. 770 Feb 48


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