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

The priming effect of LHRH in vitro (which results in increased responsiveness of gonadotropes to both LHRH receptor-mediated and receptor-independent stimuli) is brought about by an unknown mechanism. The present results indicate that induction of the LHRH priming effect is inhibited in a concentration-dependent manner by the protein kinase C (PKC) inhibitors staurosporine, K252a, H7 and by the novel highly-selective PKC inhibitor, Ro 31-8220. In contrast, a range of other compounds that are relatively selective inhibitors of other kinases such as tyrosine kinases and Ca2+/calmodulin-dependent kinases were unable to prevent priming. The PKC inhibitors prevented priming without affecting initial LHRH-induced gonadotropin secretion. Thus, the priming-elicited increment in secretion was selectively removed, restoring hormone release to the level measured during an initial response to LHRH. Similar results were obtained on different days of the estrous cycle where the magnitude of the priming effect varies. Experiments on the time course of PKC inhibitor action revealed that the critical period was in the induction of the priming effect, not its expression. The PKC inhibitors had neither acute nor delayed effects on gonadotropin secretion induced by ionomycin. Staurosporine, K252a and Ro 31-8220 inhibited LHRH priming with identical potencies to their inhibition of phorbol ester-induced gonadotropin secretion. The reduced potency of H7 seen on LHRH priming compared to phorbol ester-induced gonadotropin release parallels results seen with this inhibitor on phorbol ester-induced secretion of growth hormone (Johnson and Mitchell (1989) Biochem. Soc. Trans. 17, 751-752) and on the pharmacological characteristics of PKCs partially purified from anterior pituitary tissue. In all aspects of this study, effects on luteinizing hormone (LH) and follicle-stimulating hormone (FSH) secretion appeared to be entirely similar.
Mol Cell Endocrinol 1992 Jun
PMID:The priming effect of luteinizing hormone-releasing hormone (LHRH) but not LHRH-induced gonadotropin release, can be prevented by certain protein kinase C inhibitors. 163 16

The effect of regucalcin, a calcium-binding protein isolated from rat liver cytosol, on Ca2+ transport in rat liver nuclei was investigated. Ca2+ uptake and release were determined with a Ca2+ electrode. Ca2+ uptake increased dependent on adenosine triphosphate (ATP; 0.5-2.0 mM), while the uptake was negligible in the presence of 2 mM ADP or AMP. Regucalcin (0.5-2.0 microM) had no effect on Ca2+ uptake following addition of 2.0 mM ATP. Meanwhile, Ca2+, which accumulated in the nuclei during 10 min after ATP addition, was significantly released by the addition of regucalcin. This release was dose-dependent (0.1-2.0 microM). Vanadate (100 microM) and guanosine triphosphate (100 microM) did not cause a significant release of Ca2+ from the nuclei. Trifluoroperazine (TFP; 50 microM), an antagonist of calmodulin, significantly increased Ca2+ release from the nuclei. The presence of regucalcin (0.5 microM) further enhanced the TFP effect. These results indicate that regucalcin stimulates Ca2+ release from liver nuclei, and that the effect is not influenced by calmodulin antagonist. The finding suggests that regucalcin can regulate the Ca2+ transport system in rat liver nuclei.
Mol Cell Biochem 1992 Jul 06
PMID:Effect of calcium-binding protein regucalcin on Ca2+ transport system in rat liver nuclei: stimulation of Ca2+ release. 164 Sep 37

Saccharomyces cerevisiae genomic clones that encode calmodulin-binding proteins were isolated by screening a lambda gt11 expression library using 125I-labeled calmodulin as probe. Among the cloned yeast genes, we found two closely related genes (CMP1 and CMP2) that encode proteins homologous to the catalytic subunit of phosphoprotein phosphatase. The presumed CMP1 protein (62,999 Da) and CMP2 protein (68,496 Da) contain a 23 amino acid sequence very similar to those identified as calmodulin-binding sites in many calmodulin-regulated proteins. The yeast genes encode proteins especially homologous to the catalytic subunit of mammalian phosphoprotein phosphatase type 2B (calcineurin). The products of the CMP1 and CMP2 genes were identified by immunoblot analysis of cell extracts as proteins of 62,000 and 64,000 Da, respectively. Gene disruption experiments demonstrated that elimination of either or both of these genes had no effect on cell viability, indicating that these genes are not essential for normal cell growth.
Mol Gen Genet 1991 May
PMID:The Saccharomyces cerevisiae genes (CMP1 and CMP2) encoding calmodulin-binding proteins homologous to the catalytic subunit of mammalian protein phosphatase 2B. 164 87

A calmodulin (CaM) cDNA was isolated by differential hybridization screening of a lambda gt10 library prepared from rat olfactory mucosa. This cDNA fragment, containing most of the open reading frame of the rat CaMI gene, was subcloned and used to characterize steady-state expression of CaM mRNA in rat olfactory neuroepithelium and bulb. Within the bulb mitral cells are the primary neuronal population expressing CaM mRNA. The major CaM mRNA expressed in the olfactory mucosa is 1.7 kb with smaller contributions from mRNAs of 4.0 and 1.4 kb. CaM mRNA was primarily associated with the olfactory neurons and, despite the cellular complexity of the tissue and the known involvement of CaM in diverse cellular processes, was only minimally evident in sustentacular cells, gland cells or respiratory epithelium. Following bulbectomy CaM mRNA declines in the olfactory neuroepithelium as does olfactory marker protein (OMP) mRNA. In contrast to the latter, CaM mRNA makes a partial recovery by one month after surgery. These results, coupled with those from in situ hybridization, indicate that CaM mRNA is expressed in both mature and immature olfactory neurons. The program regulating CaM gene expression in olfactory neurons is distinct from those controlling expression of B50/GAP43 in immature, or OMP in mature, neurons respectively.
Brain Res Mol Brain Res 1991 Apr
PMID:Expression of calmodulin mRNA in rat olfactory neuroepithelium. 164 79

The major phosphoproteins observed after lysis of synaptosomes and incubation in the presence of [gamma-32P]ATP and calmodulin are the autophosphorylated 50-kDa and 60-kDa subunits of calmodulin-stimulated protein kinase II (CMK II). However, when intact synaptosomes are preincubated with 32Pi, these subunits are hardly labeled even after depolarization. The aim of this study was to determine the extent to which methodological factors contribute to this discrepancy. The distribution of CMK II between the outside and the inside of synaptosomes was determined by incubating intact and lysed synaptosomes with [gamma-32P]ATP. Some 38% of the 50-kDa subunit was found on the inside of synaptosomes, and at this location it would be accessible to ATP generated within synaptosomes during the preincubation with 32Pi and could be autophosphorylated. The rest (62%) was on the outside of the synaptosomes, presumably associated with postsynaptic densities, where it could not be autophosphorylated. The effect of preincubation at 37 degrees C on CMK II autophosphorylation was determined by incubating intact synaptosomes for 45 min. This reduced calmodulin-stimulated autophosphorylation of the 50-kDa subunit in lysed synaptosomes by 38% and in intact synaptosomes by 29%. Thus, 9% of the 50-kDa autophosphorylation activity within synaptosomes was lost by thermal inactivation during preincubation. The extent of this loss of activity depended on the synaptosomal protein concentration during preincubation. CMK II activity against its major endogenous substrate synapsin I and an exogenous peptide substrate was also decreased by preincubation. The effect of the ionic environment on CMK II autophosphorylation was determined by incubating lysed synaptosomes with [gamma-32P]ATP in the absence or presence of ions at concentrations that mimic the extra or intracellular environment.(ABSTRACT TRUNCATED AT 250 WORDS)
J Mol Neurosci 1991
PMID:Autophosphorylation of calmodulin-stimulated protein kinase II in intact synaptosomes. 164 12

Vascular smooth muscle intracellular pH is maintained by the Na+/H+ and Cl-/HCO3- antiporters. The Na+/H+ exchanger is a major route of H+ extrusion in most eukaryotic cells and is present in vascular smooth muscle cells in a similar capacity. It extrudes H+ into the extracellular space in exchange for Na+. The Cl-/HCO3- exchanger plays an analogous role to lower the pH of vascular smooth muscle cells when increases in intracellular pH occur. Its activity has also been demonstrated in A7r5 and A10 vascular smooth muscle cells. The Na+/H+ exchanger is regulated by a number of agents which act through inositol trisphosphate/diacylglycerol, to stimulate the antiporter. Calcium-calmodulin dependent protein kinase may also activate the antiporter in vivo. Phosphorylation of the Cl-/HCO3- exchanger has also been observed but its physiological role is not known. Both these antiporters exist in the plasma membrane as integral proteins with free acidic cytoplasmic termini. These regions may be important in 'sensing' changes in intracellular pH, to which these antiporters respond.
Mol Cell Biochem 1991 Apr 10
PMID:The role of ion antiporters in the maintenance of intracellular pH in rat vascular smooth muscle cells. 165 79

DEAE-cellulose column chromatography of Neurospora crassa soluble mycelial extracts leads to the resolution of three major protein kinase activity peaks designated PKI, PKII, and PKIII. PKII activity is stimulated by Ca2+ and Neurospora or brain calmodulin. Maximal stimulation was observed at 2 microM-free Ca2+ and 1 microgram/ml of the modulator. The stimulatory effect of the Ca(2+)-calmodulin complex was blocked by EGTA and by some calmodulin antagonists such as phenothiazine drugs or compound 48/80. PKII phosphorylates different proteins, among which histone II-A at a low concentration and CDPKS, the synthetic peptide specific for Ca(2+-)-calmodulin dependent protein kinase, are the best substrates. Some phosphorylation can be detected in the absence of any exogenous acceptor. PKII activity assayed in the presence of histone II-A or in the absence of exogenous phosphate acceptor (autophosphorylation) co-elute in a DEAE-cellulose column at 0.28 NaCl. As result of the autophosphorylation reaction of the purified enzyme a main phosphorylated component of 70 kDa was resolved by SDS-polyacrylamide gel electrophoresis. It is possible that this component is an active part of this enzyme.
Mol Cell Biochem 1991 Apr 10
PMID:Ca2+ calmodulin-dependent protein kinase activity in the ascomycetes Neurospora crassa. 165 80

A nucleoside triphosphatase (NTPase) activity appeared to be associated with a highly purified nuclear preparation from rat cardiac ventricles. Different nucleoside triphosphates (UTP greater than GTP greater than ITP greater than CTP) supported this enzymic activity, which was stimulated by Mg2+ but not by Ca2+. The nuclear NTPase activity could be down regulated by endogenous phosphorylation of a 55,000 Mr protein. Maximal phosphorylation of the 55,000 Mr protein occurred in the presence of Mg(2+)-ATP. Addition of cAMP, cGMP, Ca2+, Ca2+/phospholipid, Ca2+/calmodulin, and catalytic subunit of cAMP-dependent protein kinase was not associated with any further phosphorylation of the 55,000 Mr protein. However, in the presence of Ca2+/calmodulin or the catalytic subunit of the cAMP-dependent protein kinase additional proteins became phosphorylated, but these had no effect on the Mg(2+)-NTPase activity. These results indicate that a protein with Mr 55,000 may be involved in the regulation the Mg(2+)-NTPase activity associated with rat cardiac nuclei.
Mol Cell Biochem 1991 Apr 10
PMID:Regulation of rat cardiac nuclei-associated Mg(2+)-NTPase by phosphorylation. 165 81

Hormone-sensitive adenylyl cyclase is a model system for the study of receptor-mediated signal transduction. It is comprised of three types of components: 1) receptors for hormones that regulate cyclic AMP (cAMP) synthesis, 2) regulatory GTP binding proteins (G proteins), and 3) the family of enzymes, the adenylyl cyclases. Concentrations of cAMP are altered by at least 35 different stimulatory or inhibitory hormones and neurotransmitters. Other signalling pathways may also influence cAMP production through regulation of particular adenylyl cyclase subtypes. The second messenger, cAMP propagates the hormone signal through the effects of cAMP-dependent protein kinase. While structural information on the adenylyl cyclases is limited, a cDNA clone for a calmodulin-sensitive form of bovine brain adenylyl cyclase has been isolated. The amino acid sequence encoded by the Type I cDNA is approximately 40% identical to those specified by three other adenylyl cyclase cDNAs that have been cloned subsequently. This degree of structural variation implies that there must be functional differences between the adenylyl cyclases.
Mol Cell Biochem
PMID:The adenylyl cyclase family. 165 97

The effect of regucalcin, a calcium-binding protein isolated from rat liver cytosol, on Ca2+/calmodulin-dependent cyclic nucleotide (AMP) phosphodiesterase activity in rat liver cytosol was investigated. The addition of Ca2+ (50 microM) and calmodulin 160 U/ml in the enzyme reaction mixture caused a significant increase in cyclic AMP phosphodiesterase activity. This increase was inhibited by the presence of regucalcin (0.5-3.0 microM); the inhibitory effect was complete at 1.0 microM. Regucalcin (1.0 microM) did not have an appreciable effect on basal activity without Ca2+ and calmodulin. The inhibitory effect of regucalcin was still evident even at several fold higher concentrations of calmodulin (160-480 U/ml). However, regucalcin (1.0 microM) did not inhibit Ca2+/calmodulin-dependent cyclic AMP phosphodiesterase activity in the presence of 100 and 200 microM Ca2+ added. Meanwhile, Cd2+ (25-100 microM)-induced decrease in Ca2+/calmodulin-dependent cyclic AMP phosphodiesterase activity was not reversed by the presence of regucalcin (1.0 microM). The present results suggest that regucalcin can regulate Ca2+/calmodulin-dependent cyclic AMP phosphodiesterase activity due to binding Ca2+ in liver cells.
Mol Cell Biochem 1991 Jul 24
PMID:Inhibitory effect of calcium-binding protein regucalcin on Ca2+/calmodulin-dependent cyclic nucleotide phosphodiesterase activity in rat liver cytosol. 165 6


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