Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:4.6.1.2 (guanylate cyclase)
 8,497 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Atrial natriuretic peptide (ANP) binds to the guanylyl cyclase-A (GC-A) receptor found in tissues such as the kidney and adrenal gland, resulting in marked elevations of the intracellular signaling molecule, cGMP. Here, GC-A is shown to exist as a phosphoprotein when expressed in human embryonic 293 cells. The 32P is principally associated with phosphoserine, with only trace amounts of phosphothreonine. The addition of ANP causes a time-dependent dephosphorylation of the receptor, as well as desensitization, which is not due to an ANP-mediated decrease in the amount of receptor protein. The mobility of GC-A on sodium dodecyl sulfate-polyacrylamide gel electrophoresis increases after treatment of cells with ANP, and protein phosphatase 2A induces the same mobility shift. The protein phosphatase also catalyzes dephosphorylation of GC-A, and this is directly correlated with decreases in ANP-stimulatable guanylyl cyclase activity. Okadaic acid, an inhibitor of protein phosphatase 2A, blocks both the dephosphorylation and the desensitization. Therefore, in contrast to many other cell surface receptors, GC-A is desensitized by ligand-induced dephosphorylation.
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PMID:Dephosphorylation of the guanylyl cyclase-A receptor causes desensitization. 135 76

We investigated whether calmodulin mediates the stimulating effect of Ca2+ on nitric oxide synthase in the cytosol of porcine aortic endothelial cells. Nitric oxide was quantified by activation of a purified soluble guanylate cyclase. The Ca2(+)-sensitivity of nitric oxide synthase was lost after anion exchange chromatography of the endothelial cytosol and could only be reconstituted by addition of calmodulin or heat-denatured endothelial cytosol. The Ca2(+)-dependent activation of nitric oxide synthase in the cytosol was inhibited by the calmodulin-binding peptides/proteins melittin, mastoparan, and calcineurin (IC50 450, 350 and 60 nM, respectively), but not by the calmodulin antagonist, calmidazolium. In contrast, Ca2(+)-calmodulin-reconstituted nitric oxide synthase was inhibited with similar potency by melittin and calmidazolium. The results suggest that the Ca2(+)-dependent activation of nitric oxide synthase in endothelial cells is mediated by calmodulin.
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PMID:Calcium-dependent nitric oxide synthesis in endothelial cytosol is mediated by calmodulin. 169 82

We investigated the molecular mechanisms whereby Ca2+ enters the endothelial cytosol and regulates endothelial nitric oxide synthesis L-arginine-dependent nitric oxide synthesis by isolated endothelial cytosol as quantified by activation of a purified soluble guanylate cyclase was concentration-dependently enhanced by free Ca2+ (EC50 0.3 microM). The Ca(2+)-dependent activation was inhibited by the calmodulin antagonists mastoparan, melittin, and calcineurin (IC50 450, 350, and 60 nM, respectively) in a calmodulin-reversible manner. After removal of endogenous calmodulin the Ca(2+)-dependency of endothelial NO synthase was lost, but could be reconstituted with exogenous calmodulin. The results indicate that Ca(2+)-calmodulin directly activates the endothelial nitric oxide synthase, thereby transducing agonist-induced increases in intracellular free Ca2+ concentration to nitric oxide formation from L-arginine, K(+)-induced depolarization of the endothelial cells markedly inhibited the sustained, but not initial phase of the intracellular Ca2+ response to bradykinin, indicating that K(+)-induced depolarization depresses the transmembrane Ca2+ influx. On the contrary, the K+ channel activator Hoe 234 which elicits hyperpolarization of the endothelial cell membrane, augmented the sustained phase of the agonist-induced intracellular Ca2+ signal, but not the resting intracellular Ca2+ level. The effects of K+ and Hoe 234 on the agonist-induced Ca(2+)-response were reflected by corresponding changes in agonist-induced EDRF/NO release. From these data, we suggest that the endothelial membrane potential may play an important role for the extent of agonist-induced Ca2+ influx and, thereby, the endothelial EDRF/NO synthesis.
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PMID:Cellular mechanisms controlling EDRF/NO formation in endothelial cells. 171 54

Protein phosphorylation has been recognized as a major mechanism by which cellular functions are controlled by neurotransmitters and hormones. In this review, applications of molecular biological techniques to the analyses of regulatory mechanisms of protein phosphorylation by four major second messengers, cAMP, cGMP, diacylglycerol, and Ca2+, are described. 1) Complementary DNA of the regulatory subunit of the cAMP-dependent protein kinase was cloned and expressed in E. coli. Point mutations were introduced in order to analyze functional domains of the subunit. 2) The soluble isoform of guanylate cyclase was purified, and a cDNA of its 70-KD subunit was cloned. Cyclic GMP binding to purified cGMP-dependent protein kinase was characterized using a rapid filtration assay. 3) Primary structure of the catalytic subunit of calmodulin-dependent protein phosphatase (calcineurin A) was determined and the presence of the second isoform of the enzyme was shown by the cDNA cloning technique. 4) The regulatory domain of the protein kinase C was expressed in E. coli. Analysis using site-directed mutagenesis revealed that a "zinc finger"-like structure is responsible for the binding of phorbol esters. In these studies, the molecular biological approach has proven to be useful for clarifying the molecular mechanisms of cellular signal transduction related to second messengers and protein phosphorylation.
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PMID:[Second messengers and protein phosphorylation in cellular signal transduction]. 222 19

Guanylate cyclase is dephosphorylated in response to the interaction of egg peptides with a spermatozoan surface receptor (Suzuki, N., Shimomura, H., Radany, E. W., Ramarao, C. S., Ward, G. E., Bentley, J. K., and Garbers, D. L. (1984) J. Biol. Chem. 259, 14874-14879). Here, the phosphorylated form of guanylate cyclase was purified to apparent homogeneity from detergent-solubilized spermatozoan membranes by the use of GTP-agarose, DEAE-Sephacel, and concanavalin A-Sepharose chromatography. To prevent dephosphorylation of the enzyme during purification, glycerol (35%) was required in all buffers. Following purification, a single protein-staining band of Mr 160,000 was obtained on sodium dodecyl sulfate-polyacrylamide gels. The final specific activity of the purified enzyme was 83 mumol of cyclic GMP formed/min/mg of protein at 30 degrees C, an activity 5-fold higher than that observed with the purified, dephosphorylated form of guanylate cyclase. A preparation containing protein phosphatase from spermatozoa, or highly purified alkaline phosphatase (from Escherichia coli), catalyzed the dephosphorylation of the enzyme; this resulted in a subsequent decrease in guanylate cyclase activity and a shift in the Mr from 160,000 to 150,000. The phosphate content of the high Mr form of the enzyme was 14.6 mol/mol protein whereas the phosphate content of the low Mr form was 1.6 mol/mol protein. All phosphate was localized on serine residues. The Mr 160,000 form of guanylate cyclase demonstrated positive cooperative kinetics with respect to MnGTP while the Mr 150,000 form displayed linear, Michaelis-Menten type kinetics. The phosphorylation state of the membrane form of guanylate cyclase, therefore, appears to dictate not only the absolute activity of the enzyme but also the degree of cooperative interaction between catalytic or GTP-binding sites.
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PMID:Purification and properties of the phosphorylated form of guanylate cyclase. 289 12

A complementary DNA clone corresponding to the 70 kDa subunit of soluble guanylate cyclase (EC 4.6.1.2) of rat lung has been isolated. The primary structure of the cDNA consisted of 3063 nucleotides including a 1857-nucleotide coding region for 619 amino acids, and the calculated molecular weight was 70476. Blot hybridization of total poly(A)+RNAs from rat tissues detected a mRNA of about 3.4 kilobases. The amount of mRNA was abundant in lung, cerebrum and cerebellum, moderate in heart and kidney, and low in liver and muscle. Southern blot analysis of high molecular weight genomic DNA from rat liver indicated the presence of one gene in the rat haploid genome. The amino acid sequence of the 70 kDa subunit has partial homology with particulate guanylate cyclase from sea-urchin sperm, and protein phosphatase inhibitor I.
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PMID:Molecular cloning of a cDNA coding for 70 kilodalton subunit of soluble guanylate cyclase from rat lung. 290 28

Estrogen-induced protein was purified from rat uteri and assayed for several enzymatic activities involved in the metabolism and action of cyclic nucleotides. No adenylate and guanylate cyclase (EC 4.6.1.1 and 4.6.1.2, respectively), protein kinase (EC 2.7.1.33), and cyclic nucleotide binding activities could be demonstrated in three independent preparations of the protein. However, all three preparations exhibited significant phosphoprotein phosphatase activity (EC 3.1.3.16) on phosphorylated protamine and histones F1. This activity is optimal at neutral pH, inhibited by Zn(++), and unaffected by cyclic AMP or cyclic GMP.
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PMID:Phosphoprotein phosphatase activity associated with estrogen-induced protein in rat uterus. 415 69

The need for nonshivering heat production, a principal function of brown adipose tissue, is accentuated in neonates. Accordingly, brown fat in the rat exhibits a very pronounced process of morphological and functional maturation perinatally, reaches a peak in its differentiation and heat-generating capacity within 1-2 weeks after birth, and undergoes involutive changes later in life. The later process of dedifferentiation can be either prevented or reversed by exposing the animals to cold ambient temperature for a prolonged period of time (cold acclimatization). The regulation of both the tissue maturation processes and the superimposed acute heat production are hormone mediated. Thus, the hormone receptor system within the adipocyte membrane and the sequence of molecular events interconnecting the initial hormonal stimulus with its final intracellular effect(s) are of considerable importance. The brown adipocytes of developing rats possess adrenoreceptors that can be pharmacologically classified as beta 1 (linked to adenylate cyclase) and alpha 2 (possibly linked to guanylate cyclase), multiple forms of cyclic nucleotide dependent and independent protein kinases, a protein kinase inhibitor, and at least two distinct phosphoprotein phosphatases associated with three phosphoprotein phosphatase modulators. The characteristics and developmental alterations of these regulatory components were studied in considerable detail by our group during the past decade. The results uncovered several target systems for ontogenic modifications of hormonal responses. Strong support was obtained for the hypothesis that protein phosphorylation and dephosphorylation is a major molecular mechanism involved in the regulation of both the brown adipocyte function and its proliferative activity during ontogenic development.
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PMID:Mechanisms of hormonal regulations in brown adipose tissue of developing rats. 614 37

The localization of cGMP, cGMP-dependent protein kinase, calmodulin and the calmodulin-binding protein calcineurin in Paramecium tetrauelia cells has been examined with immunocytochemical methods. These molecules appeared to be localized to a large extent in the cilia of this protozoan. To ascertain that antibodies had access to all cellular compartments we have used three different preparations for immunocytochemistry: (i) with 'whole cell' preparations immunofluorescent staining for the four molecules was mainly visible in the cilia; (ii) in 'deciliated' Paramecium, staining for cGMP and calmodulin was found in regular patterns on the cell surface most likely representing kinetosomes; (iii) using 'sectioned cells', additional cytoplasmic calmodulin appeared to be associated with glycogen particles as evidenced by the disappearance of the granular staining pattern after preincubation with alpha-amylase. In contrast, cGMP, cGMP-dependent protein kinase and calcineurin fluorescence was only very weak and diffuse in cell bodies. No nuclear fluorescence was detectable after staining with any of the antibodies. Because of the colocalization of cGMP, cGMP-dependent protein kinase, a guanylate cyclase-calmodulin-complex, and calcineurin in cilia from Paramecium, an involvement of these components in the regulation of ciliary activity is discussed.
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PMID:Immunocytochemical localization of cyclic GMP, cGMP-dependent protein kinase, calmodulin and calcineurin in Paramecium tetraurelia. 632 Nov 86

Attempts to activate partially purified preparations of the guanylyl cyclase-A (GC-A) receptor with atrial natriuretic peptide (ANP) have previously failed, leading to speculation that essential cofactors are lost during purification procedures. The receptor was modified to contain the FLAG epitope (DYKDDDDK), expressed in Sf9 cells, and purified to apparent homogeneity (4.3 mumol cyclic GMP formed/min/mg protein; 5.8 mmol 125I-ANP binding site/mg protein) by a combination of immunoaffinity, Q-Sepharose FF, and wheat germ agglutinin batch chromatography. High initial protein/detergent ratios, the presence of glycerol (40%), and the inclusion of protein phosphatase inhibitors in all buffers resulted in the purification of a receptor that continued to transduce the ANP/ATP activation signal. Both native and purified GC-A contained a single class of high affinity ANP binding sites (Kd = 60 pM) and an equivalent EC50 for ATP (0.3 mM). Positive cooperativity as a function of MnGTP was retained during purification. Thus, GC-A is capable of transducing a ligand binding signal in the absence of other proteins.
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PMID:The guanylyl cyclase-A receptor transduces an atrial natriuretic peptide/ATP activation signal in the absence of other proteins. 853 May 25


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