Subcellular localization of guanylate cyclase

Challenging the Norm: The Unrecognized Impact of Soluble Guanylyl Cyclase Subunits in Cancer

Since the discovery of nitric oxide (NO), a long journey has led us to the present, during which much knowledge has been gained about its pathway members and their roles in physiological and various pathophysiological conditions. Soluble guanylyl cyclase (sGC), the main NO receptor composed of the sGCα1 and sGCβ1 subunits, has been one of the central figures in this narrative. However, the sGCα1 and sGCβ1 subunits remained obscured by the focus on sGC's enzymatic activity for many years. In this review, we restore the significance of the sGCα1 and sGCβ1 subunits by compiling and analyzing available but previously overlooked information regarding their roles beyond enzymatic activity. We delve into the basics of sGC expression regulation, from its transcriptional regulation to its interaction with proteins, placing particular emphasis on evidence thus far demonstrating the actions of each sGC subunit in different tumor models. Exploring the roles of sGC subunits in cancer offers a valuable opportunity to enhance our understanding of tumor biology and discover new therapeutic avenues.

Membrane guanylate cyclase is a beautiful signal transduction machine: overview

This article is a sequel to the four earlier comprehensive reviews which covered the field of membrane guanylate cyclase from its origin to the year 2002 (Sharma in Mol Cell Biochem 230:3-30, 2002) and then to the year 2004 (Duda et al. in Peptides 26:969-984, 2005); and of the Ca(2+)-modulated membrane guanylate cyclase to the year 1997 (Pugh et al. in Biosci Rep 17:429-473, 1997) and then to 2004 (Sharma et al. in Curr Top Biochem Res 6:111-144, 2004). This article contains three parts. The first part is "Historical"; it is brief, general, and freely borrowed from the earlier reviews, covering the field from its origin to the year 2004 (Sharma in Mol Cell Biochem, 230:3-30, 2002; Duda et al. in Peptides 26:969-984, 2005). The second part focuses on the "Ca(2+)-modulated ROS-GC membrane guanylate cyclase subfamily". It is divided into two sections. Section "Historical" and covers the area from its inception to the year 2004. It is also freely borrowed from an earlier review (Sharma et al. in Curr Top Biochem Res 6:111-144, 2004). Section "Ca(2+)-modulated ROS-GC membrane guanylate cyclase subfamily" covers the area from the year 2004 to May 2009. The objective is to focus on the chronological development, recognize major contributions of the original investigators, correct misplaced facts, and project on the future trend of the field of mammalian membrane guanylate cyclase. The third portion covers the present status and concludes with future directions in the field.

Cytochemical and biochemical observations on the alveolar guanylate cyclase of golden hamster lung

Particulate guanylate cyclase (GTP pyrophosphate-lyase (cyclizing] has been cytochemically evidentiated in the cells which make-up the lung air-blood barrier. The cytochemical procedure utilized demonstrates the presence of membrane-bound guanylate cyclase activity through precipitation of lead pyrophosphate in tissues incubated with GTP or with guanylyl imidodiphosphate. Electron microscopic examination reveals that guanylate cyclase (GC) is localized, as micropinocytic vesicles, within endothelial components of small blood vessels, in basal lamina and in the flat alveolar cells. The secretory alveolar cells also exhibit the positive GC reactivity in their peripheric cytoplasm and in their microvilli. The observations support that GC and cGMP are involved in cellular transport phenomena. The enzyme might play a role in the secretion process of surface active material. Positive staining has been found also in other types of cells, namely alveolar macrophages and fibroblasts. A biochemical evaluation of GC activity shows that about 30-40% of this activity is associated with the particulate fraction, which justifies its abundance in the cytochemical reports shown in the paper.

The effects of nitroprusside and putative agonists on guanylate cyclase activity in squid giant axons

cGMP content of axoplasm from the giant axon of Loligo forbesi was investigated after subjecting the axon to various treatments. Repetitive electrical stimulation or depolarisation by high K+ caused no change in cGMP content. Glutamate and serotonin were also without effect. The nicotinic agonist carbachol (100 microM) increased cGMP levels by 90% (n = 5). A large transient elevation of cGMP content was evoked by external nitroprusside (10 nM-20 microM in intact axons. Nitroprusside injected into both extruded axoplasm and intact axons also increased cGMP content, the stimulation being considerably higher in intact axons where the axolemma was also present. Nitroprusside was also active in axons where the soluble cytoplasmic components were washed out by internal perfusion.

Properties of digitonin-solubilized calmodulin-dependent guanylate cyclase from the plasma membranes of Tetrahymena pyriformis NT-1 cells

Calmodulin-dependent guanylate cyclase from Tetrahymena plasma membranes was solubilized in about a 22% yield by using digitonin in the presence of 0.2 mM CaCl2 and 20% glycerol. The detergent, when present in the assay at concentrations above 0.05%, diminished the basal and calmodulin-stimulated activity of the enzyme. Guanylate cyclase solubilized with digitonin was eluted from DEAE-cellulose with 200 mM KCl in a yield of 50%. Properties of the solubilized enzyme were similar to those of the native membrane-bound enzyme. The Kms for Mg-GTP and Mn-GTP were 140 and 30 microM, respectively. The enzyme required Mn2+ for maximum activity, the relative activity in the presence of Mg2+ being 30% of the activity with Mn2+. The solubilized enzyme retained the ability to be activated by calmodulin, with its extent being reduced as compared to the membrane-bound enzyme. The presence of a Ca2+-dependent calmodulin-binding site on the solubilized enzyme was shown by the Ca2+-dependent retention of the enzyme on a calmodulin-Sepharose-4B column.

Phospholipase A2 modulation of cyclic GMP metabolism: characteristics of guanylate cyclase activation

Characteristics of phospholipase A2 (PLA2) modulation of guanylate cyclase were evaluated. Addition of phospholipase A2 from Vipera russelli venom led to a significant increase in the activity of guanylate cyclase in various rat organs. The activation of the enzyme was selective and was only observed in the particulate fractions of tissue homogenate. The soluble guanylate cyclase from all the tissue tested exhibited lack of stimulation. The treatment of membranes with PLA2 resulted in solubilization of cyclase activity. The increase in enzyme by PLA2 was not altered by antioxidants or reducing agents. Addition of calcium ions led to further enhancement in PLA2-dependent increases in cyclic GMP formation. Peak calcium responses were observed in micromolar concentration ranges. These observations suggest a potential role for PLA2 and calcium ions in the hormonal regulation of cyclic GMP metabolism.

Ultracytochemical localization of guanylate cyclase activity in guinea-pig peritoneal macrophages under different physiological conditions

Guanylate cyclase activity was investigated in guinea-pig peritoneal macrophages under different physiological conditions (such as adhesion and phagocytosis) with an ultracytochemical method using guanylyl-imidodiphosphate as a substrate. The enzyme was detected on the perinuclear envelope, endoplasmic reticulum, Golgi complex and mitochondria of adherent and phagocytozing macrophages. No reaction product was present around phagocytozed polystyrene particles. The amount of final reaction product was increased by the addition of sodium azide to the incubation medium and no staining was observed when the substrate was omitted from the medium.

Highly purified particulate guanylate cyclase from rat lung: characterization and comparison with soluble guanylate cyclase

Guanylate cyclase was purified 1000-fold from washed rat lung particulate fractions to a final specific activity of 500 nmoles cyclic GMP produced/min/mg protein by a combination of detergent extraction and chromatography on concanavalin A-Sepharose, GTP-agarose, and blue agarose. Particulate guanylate cyclase has a molecular weight of 200 000 daltons, a Stokes radius of 48 A and a sedimentation coefficient of 9.4 while the soluble form has a molecular weight of 150 000 daltons, a Stokes radius of 44 A, and a sedimentation coefficient of 7.0. Whereas the particulate enzyme is a glycoprotein with a specific affinity for concanavalin A and wheat germ agglutinin, the soluble form of guanylate cyclase did not bind to these lectins. Purified particulate guanylate cyclase did not cross-react with a number of monoclonal antibodies generated to the soluble enzyme. While both forms of the enzyme could be regulated by the formation of mixed disulfides, the particulate enzyme was relatively insensitive to inhibition by cystine. With GTP as substrate both forms of the enzyme demonstrated typical kinetics, and with GTP analogues negative cooperativity was observed with both enzyme forms. These data support the suggestion that the two forms of guanylate cyclase possess similar catalytic sites, although their remaining structure is divergent, resulting in differences in subcellular distribution, physical characteristics, and antigenicity.

Cytochemical demonstration of guanylate cyclase activity in cardiac muscle. Preferential localization at sarcolemma and junctional sarcoplasmic reticulum

The localization of guanylate cyclase activity was cytochemically studied in heart tissue from guinea pig and pigeon. The method, based on a lead precipitation technique with GPPNHP as the substrate, was tested by quantitative biochemical analysis. The data obtained showed that in heart homogenates GPPNHP is an acceptable substrate for guanylate cyclase. The guanylate cyclase activity of glutaraldehyde prefixed heart tissue was also measured in the presence of 2 mM lead nitrate, in 30% of the untreated control hearts. The residual guanylate cyclase responded to the addition of sodium nitroprusside with a 7-fold increase in its activity. Furthermore, the guanylate cyclase requirement for Mn2+ ions was so changed by this activator that Mg2+ was as active as Mn2+. In heart muscle cells of guinea pigs and pigeons the plasma membrane of the sarcolemma and the junctional sarcoplasmic reticulum are the precipitation sites of the reaction product. In guinea pig hearts the T-tubule membranes were likewise covered with precipitates. Sodium nitroprusside stimulation of guanylate cyclase activity was indicated by increased precipitation and by shortening of the incubation time.

Antigenic conservation of brain guanylate cyclase during evolution

A comparative study of brain guanylate cyclase from different animal species (including man, bird, fish and amphibian) has been performed using a specific antibody directed against soluble rat brain guanylate cyclase. Analyses were performed on supernatant fractions by the double-immunodiffusion test, by the protein blotting technique after SDS-polyacrylamide gel electrophoresis and by analytical isoelectric focusing on agarose allowing specific immunodetection of isoelectric patterns. Membrane-bound guanylate cyclase from rat brain and soluble guanylate cyclase from several rat tissues cross-reacted with the antibody. All the brain enzymes tested were found to be identical by double-immunodiffusion. The electrophoretic and isoelectrophoretic profiles of the different brain guanylate cyclases were found to exhibit many common features with some differences between mammalian and non-mammalian enzymes. In human brain, guanylate cyclase has been localized in glial and neuronal cells by immunohistochemistry. The results demonstrate that guanylate cyclase has been well conserved during the course of evolution and are consistent with the involvement of guanylate cyclase and cyclic GMP in basic cellular function.

Inhibition of Escherichia coli heat-stable enterotoxin effects on intestinal guanylate cyclase and fluid secretion by quinacrine

Enterotoxigenic Escherichia coli may produce a heat-stable enterotoxin (ST) that causes diarrheal disease in humans and in animals ST activates particulate guanylate cyclase in intestinal mucosal cells and causes intestinal fluid secretion. In this study, we examined the effects of quinacrine on ST activation of guanylate cyclase and ST-mediated intestinal fluid secretion. Quinacrine significantly reduced ST activation of particulate guanylate cyclase in rat intestinal tissue. Additionally, quinacrine reduced ST-mediated fluid secretion in a rat intestinal loop assay (P less than 0.05). In the suckling mouse model, subcutaneous quinacrine (0.1 mumole/mouse) reduced ST-induced fluid secretion at a submaximally effective dose of the toxin, but it did not reduce ST-mediated fluid secretion at a near maximally effective dose. Quinacrine (0.1 mumole/mouse) did not significantly reduce intestinal fluid secretion induced by the analog of cyclic GMP, 8-bromo cyclic GMP. However, at a higher concentration of quinacrine (1 mumole/mouse), significant inhibition of 8-bromo cyclic GMP-induced secretion was observed. Inhibition by the antimalarial agent quinacrine of ST-induced fluid secretion, by a block prior to guanylate cyclase activation, suggests a possible role for a phospholipase early in the sequence of events of ST activation of guanylate cyclase. The results suggest that ST may activate membrane phospholipases prior to ST activation of guanylate cyclase.

Effects of Ca2+ and calmodulin on cyclic nucleotide metabolism in neurosecretosomes isolated from ox neurohypophyses

In neurosecretosomes, isolated from ox neurohypophyses, both guanylate and adenylate cyclase activity was shown to be predominantly membrane-bound. Membrane-bound adenylate cyclase was inhibited by increasing the ionized calcium concentration from 10(-7) M to 10(-5) M, but was stimulated by calmodulin in the presence of 10(-7) M and 10(-5) M ionized calcium. In contrast, neither calcium ions nor calmodulin affected the activity of membrane-bound guanylate cyclase. Soluble cyclic AMP and cyclic GMP phosphodiesterase activities increased with increasing ionized calcium concentration (10(-7) M to 10(-3) M). At 10(-7) M ionized calcium concentration, both soluble phosphodiesterase activities were stimulated by calmodulin. Both the membrane-bound phosphodiesterase activities were inhibited by a high ionized calcium concentration (10(-3) M) and not affected by calmodulin.

Catecholamine-sensitive guanylate cyclase from human caudate nucleus

Partial purification of soluble guanylate cyclase on DEAE-Sephacel yields two separate peaks of guanylate cyclase activity. After 10-fold purification of the soluble enzyme, guanylate cyclase is markedly inhibited by micromolar concentrations of dopamine (I50 = 0.2 microM). Dopamine inhibition is observed whether the reaction is conducted with Mn2+ or with Mg2+, under atmosphere or N2(g), and using enzyme from either peak from the DEAE-Sephacel column. Other catecholamines also inhibit partially purified guanylate cyclase with an order of potency at 1 microM of: dopamine = L-DOPA > norepinephrine = isoproterenol = adrenochrome > epinephrine. The structural requirements for inhibition are two free hydroxyl groups on the phenyl ring and an ethylamine side chain. Dopamine also inhibits the Triton X-100-solubilized microsomal guanylate cyclase after partial purification on DEAE-Sephacel. Neither chlorpromazine, propranolol, nor phentolamine at 20 microM effectively block the dopamine inhibition of partially purified soluble guanylate cyclase. Micromolar concentrations of the reducing agents dithiothreitol and glutathione also inhibit partially purified guanylate cyclase, but unlike these agents, catecholamines can inhibit whether added in the reduced or the oxidized forms. Inhibition of enzyme activity by micromolar concentrations of dopamine, adrenochrome, or dithiothreitol is rapidly reversed by dilution and the dopamine inhibition is competitive with MgGTP. Inhibition does not appear to involve covalent binding or to result from the ability of catecholamines to reduce the concentrations of oxygen or free radicals in solution.

Production and properties of antibody to soluble guanylate cyclase purified from bovine brain

Guanylate cyclase was purified 12,700-fold from bovine brain supernatant, and the purified enzyme exhibited essentially a single protein band on polyacrylamide gel electrophoresis. Repeated injection of the purified enzyme into rabbits produced an antibody to guanylate cyclase. The immunoglobulin G fraction from the immunized rabbit gave only one precipitin line against the purified guanylate cyclase and the crude supernatant of bovine brain on double immunodiffusion and immunoelectrophoreis. The antibody completely inhibited the soluble guanylate cyclase activity from bovine brain, various tissues of rat and mouse and neuroblastoma N1E 115 cells, whereas the Triton-dispersed particulate guanylate cyclase from these tissues was not inhibited by the antibody.

Cyclic GMP metabolism in psoriasis: activation of soluble epidermal guanylate cyclase by arachidonic acid and 12-hydroxy-5,8,10,14-eicosatetraenoic acid

Soluble guanylate cyclase activity was measured in normal and psoriatic human epidermis. The specific activity of guanylate cyclase was determined to be increased 10-fold and 3-fold in involved and uninvolved epidermis of psoriatics, respectively, compared to normal epidermis. Arachidonic acid (5 to 100 micrometers) or 12-hydroxy-5,8,10,14-eicosatetraenoic acid (HETE) (5 to 50 micrometers) stimulated guanylate cyclase activity from involved epidermis 2- to 3-fold and from uninvolved epidermis up to 2-fold, but these fatty acids had no effect on the activity of this cyclase from normal epidermis. These results indicate that there is an increase in the cGMP biosynthetic capacity of involved epidermis from psoriatics that derives from a markedly increased specific activity of guanylate cyclase and an alteration in a property of this enzyme activity which renders it responsive to fatty acids reported to accumulate in this lesion. These observations are consistent with the report that an elevated steady-state level of cGMP is one of the consequences of the strikingly altered metabolism of cGMP in psoriatic epidermis.

Manganese and magnesium dependent properties and inner plasma membrane surface localization of guanylate cyclase from murine plasmocytoma cells

The particulate fraction from murine plasmocytoma cells contained 90 per cent of the total guanylate cyclase activity. Triton X-100 produced a 6 fold stimulation of guanylate cyclase activity in plasma membrane enriched fractions obtained by zonal centrifugation. Isolated inside out (10) vesicles contained 9 times more activity than rightside out (RSO) vesicles. This difference was abolished by Triton X-100 treatment of the vesicles indicating that the catalytic site of guanylate cyclase is located on the inner face of the plasma membrane. Kinetic studies of membranous guanylate cyclase showed that optimal activity was found with manganese. Only 20 per cent of this activity was obtained with magnesium. The Km for GTP with magnesium (1.4 mM) was about 7 fold greater than with manganese (0.2 mM). Positive cooperativity was obtained in both cases and the Hill coefficients were 1.8 for manganese and 1.6 for magnesium. Physiological concentrations of ATP were found to inhibit both manganese and magnesium supported activities indicating a possible regulatory mechanism for this nucleotide in vivo.

Highly purified basal lateral plasma membranes from rat duodenum. Physical criteria for purity

Preparations of intestinal epithelial cell basal lateral plasma membranes were analyzed with free flow electrophoresis and density perturbation with digitonin. The initial basal lateral membrane preparations were obtained by equilibrium density gradient centrifugation after two different schemes of homogenization and differential sedimentation (A.K. Mircheff, C.H. van Os, and E.M. Wright. 1978. Membr. Biochem. 1:177, and A.K. Mircheff, S.D. Hanna, M.W. Walling, and E.M. Wright. 1979. Prep. Biochem. 9:33. In these preparations, Na,K-ATPase, a marker for the basal lateral mambrane, was purified 16- to 18-fold over the initial homogenate. The preparations were also enriched in NADPH-cytochrome c reductase, alkaline phosphatase, acid phosphatase, and galactosyltransferase. Both free-flow electrophoresis, which separates on the basis of surface charge, and density perturbation with digitonin, which depends on a specific interaction of digitonin with cholesterol-rich membranes, resolved the preparation into three populations of particles. The major population, which represented basal lateral membranes purified 20- to 32-fold with respect to the initial homogenate, contained Na,K-ATPase, alkaline phosphatase, adenylate cyclase, and acid phosphatase. A second population was defined by its content of NADPH-cytochrome c reductase, and the third was defined by its content of galactosyltransferase. Guanylate cyclase appeared to be partitioned between the Na,K-ATPase-rich and NADPH-cytochrome c reductase-rich populations. Galactosyltransferase is also present in fractions which contain the Na,K-ATPase-rich membranes, but the present data cannot exclude the possibility of spillover by the adjacent, galactosyltransferase-rich population. This work emphasizes the importance of multiple, physical criteria for purity in the isolation of subcellular components.

Characterization of rat testicular guanylate cyclase during development

The biochemical characteristics of rat testicular guanylate cyclase were investigated and the activity and subcellular distribution of the enzyme was determined during testicular development. Examination of the effects of metal ions, nucleotides, detergents and other in vitro activators on the activity of guanylate cyclase revealed that the testicular enzyme is similar in most respects to guanylate cyclase isolated from other mammalian tissues. Changes in the total activity of guanylate cyclase during testicular development paralleled changes in the tissue concentration of cyclic GMP; i.e. guanylate cyclase activity and tissue cyclic GMP were highest during the early stages of development. Subcellular fractionation revealed that the activity of the soluble form of guanylate cyclase was best correlated with tissue cyclic GMP. Biochemical analysis of the soluble enzyme prepared from testes of neonatal and adult rats did not reveal any significant differences in the characteristics of the enzyme during ontogeny with the exception of a 2.5 fold increase in V noted in the neonatal testis. The results of this study are consistent with a molecular mechanism that allows independent regulation of the different forms of guanylate cyclase.

Synthesis of adenosine 3',5'-monophosphate by guanylate cyclase, a new pathway for its formation

The 105 000 X g gupernatant fractions from homogenates of various rat tissues catalyzed the formation of both cyclic GMP and cyclic AMP from GTP and ATP, respectively. Generally cyclic AMP formation with crude or purified preparations of soluble guanylate cyclase was only observed when enzyme activity was increased with sodium azide, sodium nitroprusside, N-methyl-N'-nitro-N-nitrosoguanidine, sodium nitrite, nitric oxide gas, hydroxyl radical and sodium arachidonate. Sodium fluoride did not alter the formation of either cyclic nucleotide. After chromatography of supernatant preparations on Sephadex G-200 columns or polyacrylamide gel electrophoresis, the formation of cyclic AMP and cyclic GMP was catalyzed by similar fractions. These studies indicate that the properties of guanylate cyclase are altered with activation. Since the synthesis of cyclic AMP and cyclic GMP reported in this study appears to be catalyzed by the same protein, one of the properties of activated guanylate cyclase is its ability to catalyze the formation of cyclic AMP from ATP. The properties of this newly described pathway for cyclic AMP formation are quite different from those previously described for adenylate cyclase preparations. The physiological significance of this pathway for cyclic AMP formation is not known. However, these studies suggest that the effects of some agents and processes to increase cyclic AMP accumulation in tissue could result from the activation of either adenylate cyclase or guanylate cyclase.

Particulate guanylate cyclase of skeletal muscle: effects of Ca2+ and other divalent cations on enzyme activity

The properties of particulate guanylate cyclase (GTP pyrophosphate-lyase (cyclizing), EC 4.6.1.2) from purified rabbit skeletal muscle membrane fragments were studied. Four membrane fractions were prepared by sucrose gradient centrifugation and the fractions characterized by analysis of marker enzymes. Guanylate cyclase activity was highest in the fraction possessing enzymatic properties typical of sarcolemma, while fractions enriched with sarcoplasmic reticulum had lower activities. In the presence of suboptimal Mn2+ concentrations, Mg2+ stimulated particulate guanylate cyclase activity both before and after solubilization in 1% Triton X-100. Guanylate cyclase activity was biphasic in the presence of Ca2+. Increasing the Ca2+ concentration from 10(-8) to 10(-5) M decreased the specific activity. As the Ca2+ concentration was further increased to 5 . 10(-4) M enzyme activity again increased. After solubilization of the membranes in 1% Triton X-100, Ca2+ suppressed enzyme activity. Studies utilizing ionophore X537A indicated that the altered effect of Ca2+ upon the solubilized membranes was independent of asymmetric distribution of Ca2+ and Mg2+.

Subcellular distribution of nucleotide cyclases in rat intestinal epithelium

The subcellular distributions of adenylate cyclase and guanylate cyclase were determined for the mature enterocyte from the rat duodenum. Brush-border and basolateral membranes were prepared from isolated cells by an analytical isolation procedure, and multiple linear regression analysis was used to obtain a quantitative estimate of the distribution of recovered cyclase activities between the brush borders and basolateral membranes. Adenylate cyclase was largely confined to the basolateral surface of the epithelium, whereas guanylate cyclase was found on the brush-border and basolateral membrane fractions in the ratio 2.4:1. There was no evidence for the presence of nucleotide cyclases in the cytosol. Guanylate cyclase in both the brush-border and basolateral membranes was stimulated by epinephrine, insulin, and Triton X-100, but not by carbachol. Adenylate cyclase was not influenced by epinephrine, but was markedly stimulated by NaF and vasoactive intestinal peptide. These results are discussed in relation to the effects of hormones on transport across the small intestine.

Properties of guanylate cyclase in adult rat liver and several Morris hepatomas

Guanylate cyclase (GTP pyrophyosphate-lyase (cyclizing), EC 4.6.1.2) activity was examined in preparations from normal rat liver and a series of Morris hepatomas. Homogenate gyanylate cyclase activites were 3.2, 1.6 and 1.2 nmol cyclic GMP formed per min/g tissue ihe non-substrate analogs of IMP were weak inhibitors of this enzyme, GMP and four of its analogs had Ki values ranging from 30 to 80 muM. The GMP analogs (8-azaGMP, 7-deaza-8-azaGMP, 2'-dGMP and beta-D-arabinosylGMP) and GMP were competitive inhibitors with respect to GTP.