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)

Infection with enterotoxigenic Escherichia coli is a leading cause of traveler's diarrhea. Many enterotoxigenic E. coli strains produce heat-stable enterotoxin (ST), a peptide that binds to the intestinal receptor guanylyl cyclase C known as STaR. The toxin-receptor interaction elevates intracellular cGMP, which then activates apical chloride secretion, resulting in secretory diarrhea. In this report, we examine how the intracellular domains of STaR participate in the propagation and regulation of signaling. We show that STaR exists as an oligomer in both the presence and the absence of toxin. We also demonstrate that deletion of the intracellular kinase-homology domain produces a constitutively active mutant, suggesting that this domain subserves an autoinhibitory function. Finally, we constructed a point mutant within a highly conserved region of the cyclase domain that completely inactivates the catalytic activity of guanylyl cyclase. Cotransfection of this point mutant with wild-type receptor causes a dominant-negative effect on receptor activation. This suggests that interaction of receptor subunits is required for toxin-induced activation and that the cyclase domain is involved in this essential interaction. We propose that the binding of ST to STaR promotes a conformational change across the cell membrane. This removes the inhibitory effects of the kinase-homology domain and promotes an interaction between cyclase domains that leads to receptor activation. The data suggest a paradigm of signal transduction that may also be relevant to other members of the guanylyl cyclase receptor family.
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PMID:Regulation of cell signaling by the cytoplasmic domains of the heat-stable enterotoxin receptor: identification of autoinhibitory and activating motifs. 753 43

Phosphodiesterases (PDE) metabolize cyclic nucleotides limiting the effects of vasodilators such as prostacyclin and nitric oxide (NO). In this study, DNA microarray techniques were used to assess the impact of NO on expression of PDE genes in rat pulmonary arterial smooth muscle cells (rPASMC). Incubation of rPASMC with S-nitroso-l-glutathione (GSNO) increased expression of a PDE isoform that specifically metabolizes cAMP (PDE4B) in a dose- and time-dependent manner. GSNO increased PDE4B protein levels, and rolipram-inhibitable PDE activity was 2.3 +/- 1.0-fold greater in GSNO-treated rPASMC than in untreated cells. The soluble guanylate cyclase (sGC) inhibitor, 1H-[1,2,4]oxadiazolo[4,3,-a]quinoxalin-1-one, and the cAMP-dependent protein kinase inhibitor, H89, prevented induction of PDE4B gene expression by GSNO, but the protein kinase G (PKG) inhibitors, Rp-8-pCPT-cGMPs and KT-5823, did not. Incubation of rPASMC with IL-1beta and tumor necrosis factor-alpha induced PDE4B gene expression, an effect that was inhibited by l-N(6)-(1-iminoethyl)lysine, an antagonist of NO synthase 2 (NOS2). The GSNO-induced increase in PDE4B mRNA levels was blocked by actinomycin D but augmented by cycloheximide. Infection of rPASMC with an adenovirus specifying a dominant negative cAMP response element binding protein (CREB) mutant inhibited the GSNO-induced increase of PDE4B gene expression. These results suggest that exposure of rPASMC to NO induces expression of PDE4B via a mechanism that requires cGMP synthesis by sGC but not PKG. The GSNO-induced increase of PDE4B gene expression is CREB dependent. These findings demonstrate that NO increases expression of a cAMP-specific PDE and provide evidence for a novel "cross talk" mechanism between cGMP and cAMP signaling pathways.
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PMID:Nitric oxide induces phosphodiesterase 4B expression in rat pulmonary artery smooth muscle cells. 1629 53

Control of blood vessel tone is central to vascular homeostasis. Here we show that metabolism of tryptophan to kynurenine by indoleamine 2,3-dioxygenase (Ido) expressed in endothelial cells contributes to arterial vessel relaxation and the control of blood pressure. Infection of mice with malarial parasites (Plasmodium berghei) or induction of endotoxemia in mice led to endothelial expression of Ido, decreased plasma tryptophan concentration, increased kynurenine concentration and hypotension. Pharmacological inhibition of Ido increased blood pressure in systemically inflamed mice but not in mice deficient in Ido or interferon-gamma, which is required for Ido induction. Both tryptophan and kynurenine dilated preconstricted porcine coronary arteries; the dilating effect of tryptophan required the presence of active Ido and an intact endothelium, whereas the effect of kynurenine was endothelium independent. The arterial relaxation induced by kynurenine was mediated by activation of the adenylate and soluble guanylate cyclase pathways. Kynurenine administration decreased blood pressure in a dose-dependent manner in spontaneously hypertensive rats. Our results identify tryptophan metabolism by Ido as a new pathway contributing to the regulation of vascular tone.
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PMID:Kynurenine is an endothelium-derived relaxing factor produced during inflammation. 2020 9

Infection with enterotoxigenic Escherichia coli (ETEC) is a common cause of childhood diarrhea in low- and middle-income countries, as well as of diarrhea among travelers to these countries. In children, ETEC strains secreting the heat-stable toxin (ST) are the most pathogenic, and there are ongoing efforts to develop vaccines that target ST. One important challenge for ST vaccine development is to construct immunogens that do not elicit antibodies that cross-react with guanylin and uroguanylin, which are endogenous peptides involved in regulating the activity of the guanylate cyclase-C (GC-C) receptor. We immunized mice with both human ST (STh) and porcine ST (STp) chemically coupled to bovine serum albumin, and the resulting sera neutralized the toxic activities of both STh and STp. This suggests that a vaccine based on either ST variant can confer cross-protection. However, several anti-STh and anti-STp sera cross-reacted with the endogenous peptides, suggesting that the ST sequence must be altered to reduce the risk of unwanted cross-reactivity. Epitope mapping of four monoclonal anti-STh and six anti-STp antibodies, all of which neutralized both STh and STp, revealed that most epitopes appear to have at least one amino acid residue shared with guanylin or uroguanylin. Despite this, only one monoclonal antibody displayed demonstrable cross-reactivity to the endogenous peptides, suggesting that targeted mutations of a limited number of ST residues may be sufficient to obtain a safe ST-based vaccine.
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PMID:Immunizations with Enterotoxigenic Escherichia coli Heat-Stable Toxin Conjugates Engender Toxin-Neutralizing Antibodies in Mice That Also Cross-React with Guanylin and Uroguanylin. 3106 Nov 44