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Izmailov SA, Podkorytov IS, Skrynnikov NR. Simple MD-based model for oxidative folding of peptides and proteins. Sci Rep 2017; 7:9293. [PMID: 28839177 PMCID: PMC5570944 DOI: 10.1038/s41598-017-09229-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2016] [Accepted: 07/17/2017] [Indexed: 11/14/2022] Open
Abstract
Significant strides have been recently made to fold peptides and small proteins in silico using MD simulations. However, facilities are currently lacking to include disulfide bonding in the MD models of protein folding. To address this problem, we have developed a simple empirical protocol to model formation of disulfides, which is perturbation-free, retains the same speed as conventional MD simulations and allows one to control the reaction rate. The new protocol has been tested on 15-aminoacid peptide guanylin containing four cysteine residues; the net simulation time using Amber ff14SB force field was 61 μs. The resulting isomer distribution is in qualitative agreement with experiment, suggesting that oxidative folding of guanylin in vitro occurs under kinetic control. The highly stable conformation of the so-called isomer 2(B) has been obtained for full-length guanylin, which is significantly different from the poorly ordered structure of the truncated peptide PDB ID 1GNB. In addition, we have simulated oxidative folding of guanylin within the 94-aminoacid prohormone proguanylin. The obtained structure is in good agreement with the NMR coordinates 1O8R. The proposed modeling strategy can help to explore certain fundamental aspects of protein folding and is potentially relevant for manufacturing of synthetic peptides and recombinant proteins.
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Affiliation(s)
- Sergei A Izmailov
- Laboratory of Biomolecular NMR, St. Petersburg State University, St. Petersburg, 199034, Russia
| | - Ivan S Podkorytov
- Laboratory of Biomolecular NMR, St. Petersburg State University, St. Petersburg, 199034, Russia
| | - Nikolai R Skrynnikov
- Laboratory of Biomolecular NMR, St. Petersburg State University, St. Petersburg, 199034, Russia.
- Department of Chemistry, Purdue University, West Lafayette, IN, 47907, USA.
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2
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Brancale A, Shailubhai K, Ferla S, Ricci A, Bassetto M, Jacob GS. Therapeutically targeting guanylate cyclase-C: computational modeling of plecanatide, a uroguanylin analog. Pharmacol Res Perspect 2017; 5:e00295. [PMID: 28357122 PMCID: PMC5368960 DOI: 10.1002/prp2.295] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2016] [Revised: 11/23/2016] [Accepted: 11/30/2016] [Indexed: 12/20/2022] Open
Abstract
Plecanatide is a recently developed guanylate cyclase-C (GC-C) agonist and the first uroguanylin analog designed to treat chronic idiopathic constipation (CIC) and irritable bowel syndrome with constipation (IBS-C). GC-C receptors are found across the length of the intestines and are thought to play a key role in fluid regulation and electrolyte balance. Ligands of the GC-C receptor include endogenous agonists, uroguanylin and guanylin, as well as diarrheagenic, Escherichia coli heat-stable enterotoxins (ST). Plecanatide mimics uroguanylin in its 2 disulfide-bond structure and in its ability to activate GC-Cs in a pH-dependent manner, a feature associated with the presence of acid-sensing residues (Asp2 and Glu3). Linaclotide, a synthetic analog of STh (a 19 amino acid member of ST family), contains the enterotoxin's key structural elements, including the presence of three disulfide bonds. Linaclotide, like STh, activates GC-Cs in a pH-independent manner due to the absence of pH-sensing residues. In this study, molecular dynamics simulations compared the stability of plecanatide and linaclotide to STh. Three-dimensional structures of plecanatide at various protonation states (pH 2.0, 5.0, and 7.0) were simulated with GROMACS software. Deviations from ideal binding conformations were quantified using root mean square deviation values. Simulations of linaclotide revealed a rigid conformer most similar to STh. Plecanatide simulations retained the flexible, pH-dependent structure of uroguanylin. The most active conformers of plecanatide were found at pH 5.0, which is the pH found in the proximal small intestine. GC-C receptor activation in this region would stimulate intraluminal fluid secretion, potentially relieving symptoms associated with CIC and IBS-C.
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Affiliation(s)
- Andrea Brancale
- School of Pharmacy and Pharmaceutical Sciences Cardiff University Cardiff United Kingdom
| | | | - Salvatore Ferla
- School of Pharmacy and Pharmaceutical Sciences Cardiff University Cardiff United Kingdom
| | - Antonio Ricci
- School of Pharmacy and Pharmaceutical Sciences Cardiff University Cardiff United Kingdom
| | - Marcella Bassetto
- School of Pharmacy and Pharmaceutical Sciences Cardiff University Cardiff United Kingdom
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3
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Dubreuil JD, Isaacson RE, Schifferli DM. Animal Enterotoxigenic Escherichia coli. EcoSal Plus 2016; 7:10.1128/ecosalplus.ESP-0006-2016. [PMID: 27735786 PMCID: PMC5123703 DOI: 10.1128/ecosalplus.esp-0006-2016] [Citation(s) in RCA: 165] [Impact Index Per Article: 20.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2016] [Indexed: 12/13/2022]
Abstract
Enterotoxigenic Escherichia coli (ETEC) is the most common cause of E. coli diarrhea in farm animals. ETEC are characterized by the ability to produce two types of virulence factors: adhesins that promote binding to specific enterocyte receptors for intestinal colonization and enterotoxins responsible for fluid secretion. The best-characterized adhesins are expressed in the context of fimbriae, such as the F4 (also designated K88), F5 (K99), F6 (987P), F17, and F18 fimbriae. Once established in the animal small intestine, ETEC produce enterotoxin(s) that lead to diarrhea. The enterotoxins belong to two major classes: heat-labile toxins that consist of one active and five binding subunits (LT), and heat-stable toxins that are small polypeptides (STa, STb, and EAST1). This review describes the disease and pathogenesis of animal ETEC, the corresponding virulence genes and protein products of these bacteria, their regulation and targets in animal hosts, as well as mechanisms of action. Furthermore, vaccines, inhibitors, probiotics, and the identification of potential new targets by genomics are presented in the context of animal ETEC.
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Affiliation(s)
- J Daniel Dubreuil
- Faculté de Médecine Vétérinaire, Université de Montréal, Québec J2S 7C6, Canada
| | - Richard E Isaacson
- Department of Veterinary and Biomedical Sciences, University of Minnesota, St. Paul, MN 55108
| | - Dieter M Schifferli
- School of Veterinary Medicine, University of Pennsylvania, Philadelphia, PA 19104
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4
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Blomain ES, Lin JE, Kraft CL, Trela UT, Rock JM, Aing AS, Snook AE, Waldman SA. Translating colorectal cancer prevention through the guanylyl cyclase C signaling axis. Expert Rev Clin Pharmacol 2013; 6:557-64. [PMID: 23971873 PMCID: PMC4048542 DOI: 10.1586/17512433.2013.827406] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Colorectal cancer (CRC) is a major public health concern, ranking among the leading causes of cancer death in both men and women. Because of this continued burden there is a clear need for improved treatment, and more importantly prevention of this disease. In recent years there is significant evidence to support the hypothesis that guanylyl cyclase C (GCY2C) is a tumor suppressor in the intestine, and that the loss of hormone ligands for this receptor is an important step in the disease process. Thus, ligand replacement therapy has been proposed as a strategy to prevent CRC. Until recently this strategy was not clinically plausible; however, the recent regulatory approval of linaclotide (LINZESS™, Forest Laboratories and Ironwood Pharmaceuticals, Inc.), an oral GUCY2C ligand, has raised the possibility of utilizing this strategy clinically to prevent CRC.
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Affiliation(s)
- Erik Scott Blomain
- Department of Pharmacology and Experimental Therapeutics, Thomas Jefferson University, Philadelphia, Pennsylvania
| | - Jieru Egeria Lin
- Department of Pharmacology and Experimental Therapeutics, Thomas Jefferson University, Philadelphia, Pennsylvania
| | - Crystal Lynn Kraft
- Department of Pharmacology and Experimental Therapeutics, Thomas Jefferson University, Philadelphia, Pennsylvania
| | - Urszula Teresa Trela
- Department of Pharmacology and Experimental Therapeutics, Thomas Jefferson University, Philadelphia, Pennsylvania
| | - Justin Michael Rock
- Department of Pharmacology and Experimental Therapeutics, Thomas Jefferson University, Philadelphia, Pennsylvania
| | - Amanda Sue Aing
- Department of Pharmacology and Experimental Therapeutics, Thomas Jefferson University, Philadelphia, Pennsylvania
| | - Adam Eugene Snook
- Department of Pharmacology and Experimental Therapeutics, Thomas Jefferson University, Philadelphia, Pennsylvania
| | - Scott Arthur Waldman
- Department of Pharmacology and Experimental Therapeutics, Thomas Jefferson University, Philadelphia, Pennsylvania
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5
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Constella™(EU)-Linzess™(USA): the last milestone in the long journey of the peptide linaclotide and its implications for the future of peptide drugs. Future Med Chem 2013; 5:291-300. [PMID: 23464519 DOI: 10.4155/fmc.13.5] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Irritable bowel syndrome with constipation (IBS-C) and chronic idiopathic constipation (CIC) are highly prevalent gastrointestinal disorders associated with health, economical and social problems. Recently, after a long journey of preclinical studies and clinical trials, linaclotide, a first-in-class GC-C receptor peptide agonist, has received the approval in the USA and Europe for the treatment of IBS-C and CIC. This article provides an overview of clinical, economic and biological aspects of IBS-C and CIC and covers the current and emerging therapeutic agents for treating these conditions. Particularly, the pharmacodynamic and pharmacokinetic properties of linaclotide, a small, disulfide-rich peptide, and its implications in the future of peptide drug discovery and development are discussed.
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6
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Toriano R, Ozu M, Politi MT, Dorr RA, Curto MA, Capurro C. Uroguanylin Regulates Net Fluid Secretion via the NHE2 Isoform of the Na +/H + Exchanger in an Intestinal Cellular Model. Cell Physiol Biochem 2011; 28:733-42. [DOI: 10.1159/000335767] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/26/2011] [Indexed: 12/31/2022] Open
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7
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Li P, Lin JE, Schulz S, Pitari GM, Waldman SA. Can colorectal cancer be prevented or treated by oral hormone replacement therapy? Curr Mol Pharmacol 2010; 2:285-92. [PMID: 20021465 DOI: 10.2174/1874467210902030285] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Guanylyl cyclase C (GCC) is the receptor specifically expressed by intestinal cells for the paracrine hormones guanylin and uroguanylin and diarrheagenic bacterial heat-stable enterotoxins. This tissue-specific receptor coordinates lineage-dependent regulation of epithelial homeostasis, and its disruption contributes to intestinal tumorigenesis. It coordinates regenerative and metabolic circuits by restricting the cell cycle and proliferation and programming metabolic transitions central to organizing the dynamic crypt-surface axis. Further, mice deficient in GCC signaling are more susceptible to colon cancer induced by Apc mutations or the carcinogen azoxymethane. Moreover, guanylin and uroguanylin are gene products most commonly lost, early, in colon cancer in animals and humans. The role of GCC as a tumor suppressing receptor regulating proliferation and metabolism, together with the universal loss of guanylin and uroguanylin in tumorigenesis, suggests a model in which colorectal cancer is a paracrine hormone deficiency syndrome. In that context, activation of GCC reverses the tumorigenic phenotype by limiting growth of colorectal cancer cells by restricting progression through the G1/S transition and reprogramming metabolic circuits from glycolysis to oxidative phosphorylation, limiting bioenergetic support for rapid proliferation. These observations suggest a pathophysiological hypothesis in which GCC is a lineage-dependent tumor suppressing receptor coordinating proliferative homeostasis whose dysregulation through hormone loss contributes to neoplasia. The correlative therapeutic hypothesis suggests that colorectal cancer is a disease of hormone insufficiency that can be prevented or treated by oral supplementation with GCC ligands.
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Affiliation(s)
- P Li
- Department of Pharmacology and Experimental Therapeutics, Thomas Jefferson University, Philadelphia, PA 19107, USA.
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8
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Bharucha AE, Waldman SA. Taking a lesson from microbial diarrheagenesis in the management of chronic constipation. Gastroenterology 2010; 138:813-7. [PMID: 20114092 PMCID: PMC3141216 DOI: 10.1053/j.gastro.2010.01.022] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Affiliation(s)
- Adil E. Bharucha
- Clinical Enteric Neuroscience Translational and Epidemiological Research Program, Division of Gastroenterology and Hepatology, Mayo Clinic and Mayo Foundation, Rochester, MN, USA
| | - Scott A. Waldman
- Department of Pharmacology and Experimental Therapeutics, Thomas Jefferson University, Philadelphia, PA,To whom correspondences should be addressed: 132 South 10th Street, 1170 Main, Philadelphia, PA, 19107;
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9
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Li P, Lin JE, Marszlowicz GP, Valentino MA, Chang C, Schulz S, Pitari GM, Waldman SA. GCC signaling in colorectal cancer: Is colorectal cancer a paracrine deficiency syndrome? ACTA ACUST UNITED AC 2009; 22:313-8. [PMID: 19771320 DOI: 10.1358/dnp.2009.22.6.1395254] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Guanylyl cyclase C (GCC) is the receptor expressed by intestinal cells for the paracrine hormones guanylin and uroguanylin that coordinate mucosal homeostasis and its silencing contributes to intestinal transformation. It orchestrates proliferative and metabolic circuits by limiting the cell cycle and programming metabolic transitions central to regeneration along the crypt-villus axis. Mice deficient in GCC are more susceptible to colon cancer induced by germline mutations or carcinogens. Moreover, guanylin and uroguanylin are the most commonly lost gene products in colon cancer. The role of GCC as a tumor suppressor and the universal loss of its hormones in transformation suggest a paradigm in which colorectal cancer is a disease of paracrine hormone insufficiency. Indeed, GCC signaling reverses the tumorigenic phenotype of human colon cancer cells by regulating proliferation and metabolism. These data suggest a pathophysiological hypothesis in which GCC is a tumor suppressor coordinating proliferative homeostasis whose silencing through hormone loss initiates transformation. The correlative therapeutic hypothesis suggests that colorectal cancer is a disease of hormone insufficiency that can be prevented or treated by oral hormone replacement therapy employing GCC ligands.
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Affiliation(s)
- P Li
- Department of Pharmacology and Experimental Therapeutics, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, USA
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10
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Lessa LMA, Amorim JBO, Fonteles MC, Malnic G. Effect of renoguanylin on hydrogen/bicarbonate ion transport in rat renal tubules. ACTA ACUST UNITED AC 2009; 157:37-43. [PMID: 19540271 DOI: 10.1016/j.regpep.2009.06.005] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2008] [Revised: 03/26/2009] [Accepted: 06/03/2009] [Indexed: 12/28/2022]
Abstract
Renoguanylin (REN) is a recently described member of the guanylin family, which was first isolated from eels and is expressed in intestinal and specially kidney tissues. In the present work we evaluate the effects of REN on the mechanisms of hydrogen transport in rat renal tubules by the stationary microperfusion method. We evaluated the effect of 1 muM and 10 muM of renoguanylin (REN) on the reabsorption of bicarbonate in proximal and distal segments and found that there was a significant reduction in bicarbonate reabsorption. In proximal segments, REN promoted a significant effect at both 1 and 10 muM concentrations. Comparing control and REN concentration of 1 muM, JHCO(3)(-), nmol cm(-2) s(-1)-1,76+/-0,11(control)x1,29+/-0,08(REN 10 muM); P<0.05, was obtained. In distal segments the effect of both concentrations of REN was also effective, being significant e.g. at a concentration of 1 muM (JHCO(3)(-), nmol cm(-2) s(-)1-0.80+/-0.07(control)x0.60+/-0.06(REN 1 muM); P<0.05), although at a lower level than in the proximal tubule. Our results suggest that the action of REN on hydrogen transport involves the inhibition of Na(+)/H(+)exchanger and H(+)-ATPase in the luminal membrane of the perfused tubules by a PKG dependent pathway.
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Affiliation(s)
- L M A Lessa
- Dept. Physiology and Biophysics, Inst. of Biomedical Sciences, Univ. São Paulo, Av. Prof. Lineu Prestes 1524, 05508-900 São Paulo, Brazil
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11
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Lauber T, Tidten N, Matecko I, Zeeb M, Rösch P, Marx UC. Design and characterization of a soluble fragment of the extracellular ligand-binding domain of the peptide hormone receptor guanylyl cyclase-C. Protein Eng Des Sel 2008; 22:1-7. [PMID: 18987130 DOI: 10.1093/protein/gzn062] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The intestinal guanylyl cyclase-C (GC-C) was originally identified as an Escherichia coli heat-stable enterotoxin (STa) receptor. STa stimulates GC-C to much higher activity than the endogenous ligands guanylin and uroguanylin, causing severe diarrhea. To investigate the interactions of the endogenous and bacterial ligands with GC-C, we designed and characterized a soluble and properly folded fragment of the extracellular ligand-binding domain of GC-C. The membrane-bound guanylyl cyclases exhibit a single transmembrane spanning helix and a globularly folded extracellular ligand-binding domain that comprises about 410 of 1050 residues. Based on the crystal structure of the dimerized-binding domain of the guanylyl cyclase-coupled atrial natriuretic peptide receptor and a secondary structure-guided sequence alignment, we generated a model of the extracellular domain of GC-C comprised of two subdomains. Mapping of mutational and cross-link data onto this structural model restricts the ligand-binding region to the membrane proximal subdomain. We thus designed miniGC-C, a 197 amino acid fragment that mimics the ligand-binding membrane proximal subdomain. Cloning, expression and spectroscopic studies reveal miniGC-C to be a soluble and properly folded protein with a distinct secondary and tertiary structure. MiniGC-C binds STa with nanomolar affinity.
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Affiliation(s)
- T Lauber
- Lehrstuhl für Biopolymere and Forschungszentrum für Bio-Makromoleküle, Universität Bayreuth 95440, Bayreuth
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12
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Carvalho AF, Santos-Neto MS, Monteiro HSA, Freitas SM, Morhy L, Nascimento NRF, Fonteles MC. BTCI enhances guanylin-induced natriuresis and promotes renal glomerular and tubular effects. BRAZ J BIOL 2008; 68:149-54. [PMID: 18470390 DOI: 10.1590/s1519-69842008000100021] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2006] [Accepted: 07/19/2006] [Indexed: 11/22/2022] Open
Abstract
Guanylin and uroguanylin are small cysteine-rich peptides involved in the regulation of fluid and electrolyte homeostasis through binding and activation of guanylyl cyclases signaling molecules expressed in intestine and kidney. Guanylin is less potent than uroguanylin as a natriuretic agent and is degraded in vitro by chymotrypsin due to unique structural features in the bioactive moiety of the peptide. Thus, the aim of this study was to verify whether or not guanylin is degraded by chymotrypsin-like proteases present in the kidney brush-border membranes. The isolated perfused rat kidney assay was used in this regard. Guanylin (0.2 microM) induced no changes in kidney function. However, when pretreated by the black-eyed pea trypsin and chymotrypsin inhibitor (BTCI - 1.0 microM; guanylin - 0.2 microM) it promoted increases in urine flow (DeltaUF of 0.25 +/- 0.09 mL.g(-1)/min, P < 0.05) and Na+ excretion (% Delta ENa+ of 18.20 +/- 2.17, P < 0.05). BTCI (1.0 microM) also increased %ENa+ (from 22.8 +/- 1.30 to 34.4 +/- 3.48, P < 0.05, 90 minutes). Furthermore, BTCI (3.0 microM) induced increases in glomerular filtration rate (GFR; from 0.96 +/- 0.02 to 1.28 0.02 mL.g(-1)/min, P < 0.05, 60 minutes). The present paper strongly suggests that chymotrypsin-like proteases play a role in renal metabolism of guanylin and describes for the first time renal effects induced by a member of the Bowman-Birk family of protease inhibitors.
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Affiliation(s)
- A F Carvalho
- Instituto de Biomedicina, Universidade Federal do Ceará, Fortaleza, Ceará, Brazil
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Kloeters O, Friess H, Giese N, Buechler MW, Cetin Y, Kulaksiz H. Uroguanylin inhibits proliferation of pancreatic cancer cells. Scand J Gastroenterol 2008; 43:447-55. [PMID: 18365910 DOI: 10.1080/00365520701746378] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
OBJECTIVE The peptide hormones guanylin and uroguanylin and their receptor, guanylate cyclase C (GC-C), are expressed in pancreatic duct cells. In colon cancer, guanylin peptides are shown to exert strong anti-tumor activity through the GC-C pathway. The objective of this study was to analyze the role of guanylin and uroguanylin in human pancreatic cancer. MATERIAL AND METHODS Quantitative real-time polymerase chain reaction (QRT-PCR) was used to show the expression of guanylin, uroguanylin and GC-C in specimens of human pancreatic cancer, chronic pancreatitis donor and in pancreatic tumor cell lines. The presence of guanylins and GC-C in tumor cell lines and in pancreatic cancer tissues was shown by immunofluorescence and immunohistochemistry. The effect of guanylin and uroguanylin on cell cycle and cell death of pancreatic cancer cells was investigated by fluorescence activated cell sorter (FACS) analysis using annexin and propidium iodide. In addition, the growth inhibitory effect of guanylins on pancreatic cancer cells was assessed using the MTT assay. RESULTS Guanylin, uroguanylin and GC-C were expressed at mRNA and protein levels in pancreatic cancer and cancer cell lines. As shown by QRT-PCR, GC-C expression was significantly up-regulated in pancreatic cancer compared with that in healthy pancreatic tissues (p<0.00001) and chronic pancreatitis (p<0.05). Guanylin and uroguanylin were not up-regulated in pancreatic cancer. The MTT assay revealed significant inhibition of pancreatic cancer cell proliferation by uroguanylin in a dose-dependent fashion, whereas Panc1 and Capan1 cell lines were significantly inhibited already at the lowest uroguanylin concentration (2 nM, p<0.05). CONCLUSIONS Our data suggest therapeutic properties of uroguanylin in pancreatic cancer via GC-C-dependent mechanisms. In addition, determination of GC-C expression might be a useful marker for differentiation between pancreatic cancer and chronic pancreatitis.
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Affiliation(s)
- Oliver Kloeters
- Department of General Surgery, University of Heidelberg, Germany
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14
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Abstract
Ingestion of a salty meal induces secretion of guanylin (GN) and uroguanylin (UGN) into the intestinal lumen, where they inhibit Na+ absorption and induce Cl-, HCO3-, and water secretion. Simultaneously, these hormones stimulate renal electrolyte excretion by inducing natriuresis, kaliuresis, and diuresis. GN and UGN therefore participate in the prevention of hypernatremia and hypervolemia after salty meals. The signaling pathway of GN and UGN in the intestine is well known. They activate enterocytes via guanylate cyclase C (GC-C), which leads to cGMP-dependent inhibition of Na+/H+ exchange and activation of the cystic fibrosis transmembrane regulator. In GC-C-deficient mice, GN and UGN still produce renal natriuresis, kaliuresis, and diuresis, suggesting different signaling pathways in the kidney compared with the intestine. Signaling pathways for GN and UGN in the kidney differ along the various nephron segments. In proximal tubule cells, a cGMP- and GC-C-dependent signaling was demonstrated for both peptides. In addition, UGN activates a pertussis toxin-sensitive G-protein-coupled receptor. A similar dual signaling pathway is also known for atrial natriuretic peptide. Recently, a cGMP-independent signaling pathway for GN and UGN was also shown in principal cells of the human and mouse cortical collecting duct. Because GN and UGN activate different signaling pathways in specific organs and even within the kidney, this review focuses on more recent findings on cellular effects and signaling mechanisms of these peptides and their pathophysiologic implications in the intestine and the kidney.
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Affiliation(s)
- Aleksandra Sindić
- Universitätsklinikum Münster, Medizinische Klinik und Poliklinik D, Experimentelle Nephrologie, Domagkstrasse 3a, Münster 48149, Germany
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15
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Schulz A, Marx UC, Tidten N, Lauber T, Hidaka Y, Adermann K. Side chain contributions to the interconversion of the topological isomers of guanylin-like peptides. J Pept Sci 2005; 11:319-30. [PMID: 15635659 DOI: 10.1002/psc.625] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The peptide hormones guanylin and uroguanylin are ligands of the intestinal guanylyl cyclase-C (GC-C) that is involved in the regulation of epithelial water and electrolyte transport. The small peptides contain 15 and 16 amino acids, respectively, and two disulfide bonds with a 1-3/2-4 connectivity. This structural feature causes the unique existence of two topological isoforms for each peptide in an approximate 3:2 ratio, with only one of the isoforms exhibiting GC-C-activating potential. The two uroguanylin isomers can be separated by HPLC and are of sufficient stability to be studied separately at ambient temperatures while the two guanylin isomers are rapidly interconverting even at low temperatures. Both isomers show clearly distinguishable (1)H chemical shifts. To investigate the influence of certain amino acid side chains on this isomerism and interconversion kinetics, derivatives of guanylin and uroguanylin (L-alanine scan and chimeric peptides) were designed and synthesized by Fmoc solid-phase chemistry and compared by HPLC and 2D (1)H NMR spectroscopy. Amino acid residues with the most significant effects on the interconversion kinetics were predominantly identified in the COOH-terminal part of both peptides, whereas amino acids in the central part of the peptides only moderately affected the interconversion. Thus, the conformational conversion among the isomers of both peptides is under the control of a COOH-terminal sterical hindrance, providing a detailed model for this dynamic isomerism. Our results demonstrate that kinetic control of the interconversion process can be achieved by the introduction of side chains with a defined sterical profile at suitable sequence positions. This is of potential impact for the future development of GC-C peptide agonists and antagonists.
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Affiliation(s)
- Axel Schulz
- IPF PharmaCeuticals GmbH, Feodor-Lynen-Strasse 31, D-30625 Hannover, Germany.
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16
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Sindić A, Schlatter E. Mechanisms of actions of guanylin peptides in the kidney. Pflugers Arch 2005; 450:283-91. [PMID: 15952032 DOI: 10.1007/s00424-005-1464-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2005] [Accepted: 05/03/2005] [Indexed: 02/02/2023]
Abstract
After a salty meal, stimulation of salt excretion via the kidney is a possible mechanism to prevent hypernatremia and hypervolemia. Besides the well known hormonal regulators of salt and water excretion in the distal nephron, arginine vasopressin and aldosterone, guanylin (GN) peptides produced in the intestine were proposed to be intestinal natriuretic peptides. These peptides inhibit Na+ absorption in the intestine and induce natriuresis, kaliuresis and diuresis in the kidney. The signaling pathway of GN peptides in the intestine is well known. They activate enterocytes via guanylate cyclase C (GC-C) and increase the cellular concentration of cGMP which leads to secretion of Cl-, HCO3- and water into the intestinal lumen and to inhibition of Na+ absorption. Guanylin peptides are filtered in the glomerulus, and additionally synthesized and excreted by tubular cells. They activate receptors located in the luminal membrane of the tubular cells along the nephron. In GC-C deficient mice renal effects of GN peptides are retained. In human, rat, and opossum proximal tubule cells, a cGMP-dependent signaling was demonstrated, but in addition GN peptides apparently also activate a PT-sensitive G-protein coupled receptor. A similar dual signaling pathway is also known for other natriuretic peptides like atrial natriuretic peptide. A cGMP-independent signaling pathway of GN peptides is also shown for principal cells of the human cortical collecting duct where the final hormonal regulation of electrolyte homeostasis takes place. This review will focus on the current knowledge on renal actions of GN peptides and specifically address novel GC-C- and cGMP-independent signaling mechanisms.
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Affiliation(s)
- Aleksandra Sindić
- Medizinische Klinik und Poliklinik D, Experimentelle Nephrologie, Universitätsklinikum Münster, Domagkstrasse 3a, 48149 Münster, Germany
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17
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Sopory S, Kaur T, Visweswariah SS. The cGMP-binding, cGMP-specific phosphodiesterase (PDE5): intestinal cell expression, regulation and role in fluid secretion. Cell Signal 2005; 16:681-92. [PMID: 15093609 DOI: 10.1016/j.cellsig.2003.11.004] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2003] [Revised: 11/12/2003] [Accepted: 11/12/2003] [Indexed: 11/26/2022]
Abstract
The expression and regulation of the cGMP-binding, cGMP-specific phosphodiesterase, PDE5, was studied in intestinal cells. Both PDE5A1 and PDE5A2 splice forms were cloned from the cDNA prepared from human colonic T84 cells, and PDE5 activity was dependent on increases in intracellular cGMP levels which correlated with increased phosphorylation of the enzyme. PDE5 expression was monitored in different regions of the gastrointestinal tract and nearly 50% of the phosphodiesterase activity in the duodenum, jejunum, ileum and colon was inhibited by sildenafil citrate. Administration of the stable toxin to intestinal loops resulted in activation of PDE5. Inhibition of PDE5 by sildenafil citrate led to fluid accumulation in loops, suggesting a possible explanation for the side effect of diarrhoea observed in individuals administered sildenafil citrate. Our results therefore represent the first study on the expression and regulation of PDE5 in intestinal tissue, and indicate that mechanisms to control its activity may have important consequences in intestinal physiology.
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Affiliation(s)
- Shailaja Sopory
- Department of Molecular Reproduction, Development and Genetics, Indian Institute of Science, Malleswaram, Bangalore 560012, India
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18
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Carrithers SL, Ott CE, Hill MJ, Johnson BR, Cai W, Chang JJ, Shah RG, Sun C, Mann EA, Fonteles MC, Forte LR, Jackson BA, Giannella RA, Greenberg RN. Guanylin and uroguanylin induce natriuresis in mice lacking guanylyl cyclase-C receptor. Kidney Int 2004; 65:40-53. [PMID: 14675035 DOI: 10.1111/j.1523-1755.2004.00375.x] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
BACKGROUND Guanylin (GN) and uroguanylin (UGN) are intestinally derived peptide hormones that are similar in structure and activity to the diarrhea-causing Escherichia coli heat-stable enterotoxins (STa). These secretagogues have been shown to affect fluid, Na+, K+, and Cl- transport in both the intestine and kidney, presumably by intracellular cyclic guanosine monophosphate (cGMP)-dependent signal transduction. However, the in vivo consequences of GN, UGN, and STa on renal function and their mechanism of action have yet to be rigorously tested. METHODS We hypothesized that intravenous administration of GN, UGN, or STa would cause an increase in natriuresis in wild-type mice via cGMP and guanylyl cyclase-C (GC-C, Gucy2c), the only known receptor for these peptide-hormones, and that the peptide-induced natriuresis would be blunted in genetically altered mice devoid of GC-C receptors (GC-C(-/-) null). RESULTS In wild-type mice using a modified renal clearance model, GN, UGN, and STa elicited significant natriuresis, kaliuresis, and diuresis as well as increased urinary cGMP levels in a time- and dose-dependent fashion. Absolute and fractional urinary sodium excretion levels were greatest approximately 40 minutes following a bolus infusion with pharmacologic doses of these peptides. Unexpectedly, GC-C(-/-) null mice also responded to the GN peptides similarly to that observed in wild-type mice. Glomerular filtration rate (GFR), blood pressure, and plasma cGMP in the mice (wild-type or GC-C(-/-) null) did not significantly vary between the vehicle- and peptide-treatment groups. The effects of UGN may also influence long-term renal function due to down-regulation of the Na+/K+ ATPase gamma-subunit and the Cl- channel ClC-K2 by 60% and 75%, respectively, as assessed by differential display polymerase chain reaction (PCR) (DD-PCR) and Northern blot analysis of kidney mRNA from mice treated with UGN. CONCLUSION GN, UGN, and STa act on the mouse kidney, in part, through a cGMP-dependent, GC-C-independent mechanism, causing significant natriuresis by renal tubular processes. UGN may have further long-term effects on the kidney by altering the expression of such transport-associated proteins as Na+/K+ ATPase and ClC-K2.
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MESH Headings
- Animals
- Animals, Suckling
- Bacterial Toxins/metabolism
- Bacterial Toxins/pharmacology
- Blotting, Northern
- Enterotoxins/metabolism
- Enterotoxins/pharmacology
- Escherichia coli Proteins
- Gastrointestinal Hormones/metabolism
- Gastrointestinal Hormones/pharmacology
- Guanylate Cyclase/genetics
- Guanylate Cyclase/metabolism
- Injections, Intravenous
- Mice
- Mice, Inbred Strains
- Mice, Mutant Strains
- Natriuresis/drug effects
- Natriuresis/physiology
- Natriuretic Peptides
- Peptides/metabolism
- Peptides/pharmacology
- RNA, Messenger/analysis
- Receptors, Enterotoxin
- Receptors, Guanylate Cyclase-Coupled
- Receptors, Peptide/genetics
- Receptors, Peptide/metabolism
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Affiliation(s)
- Stephen L Carrithers
- Department of Internal Medicine, Division of Infectious Diseases, Lexington VA Medical Center and University of Kentucky, Lexington, Kentucky 40506, USA.
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19
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Abstract
Uroguanylin is a peptide hormone that regulates sodium excretion by the kidney when excess NaCl is consumed. A new study demonstrates that mice deficient in uroguanylin have blunted urinary sodium excretion responses to oral sodium loads in addition to elevated blood pressure (see related article beginning on page 1244). A physiological role for uroguanylin is discussed, linking the intestine and kidney in an endocrine axis for the maintenance of sodium balance.
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Affiliation(s)
- Leonard R Forte
- Medical Research Service, Truman Memorial Veterans Administration Hospital and Radiopharmaceutical Sciences Institute, Columbia, Missouri, USA.
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20
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Santos-Neto MS, Carrithers SL, Carvalho AF, Monteiro HSA, Greenberg RN, Forte LR, Fonteles MC. Guanylin and its lysine-containing analogue in the isolated perfused rat kidney: interaction with chymotrypsin inhibitor. PHARMACOLOGY & TOXICOLOGY 2003; 92:114-20. [PMID: 12753425 DOI: 10.1034/j.1600-0773.2003.920302.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Guanylin and uroguanylin are two novel peptides that activate membrane-bound guanylate cyclases found in the kidney and intestine, influencing fluid and electrolyte homeostasis by cyclic GMP. Their natriuretic and kaliuretic activities are well documented. Since guanylin is inactivated by chymotrypsin in vitro, experiments were designed to evaluate the role of chymotrypsin-like proteases in renal metabolism of guanylin. Using the isolated perfused rat kidney, guanylin and a recombinant derivative containing a lysine residue in the N-terminus of the native peptide was tested. There were three experimental groups. In the first group, lys-guanylin (0.1-2.5 microg/ml) was placed into perfusate reservoir. In the second group, chymostatin (6 microg/ml), a chymotrypsin inhibitor, was placed into solution. In the third group, after 30 min. of perfusion with chymostatin (6 microg/ml), guanylin (0.3 microg/ml) was placed into solution. A maximal decrease in fractional Na+ reabsorption (%TNa+) was achieved at 1.0 microg/ml of lys-guanylin (from 73.25+/-2.29 to 54.97+/-0.10, P<0.05). Lys-guanylin (1.0 microg/ml) also decreased fractional K+ reabsorption (%TK+) from 59.26+/-3.93 to 30.75+/-0.78 (P<0.05). Chymostatin had no detectable effects in electrolyte reabsorption in this assay. When introduced after chymostatin, guanylin lowered %TNa+ (from 81.2+/-1.86 to 72.6+/-2.45, P<0.05) and %TK+ (from 69.4+/-4.12 to 65.8+/-2.81, P<0.05). At this subthreshold concentration, guanylin alone lacks effects in %TNa+ or %TK+. Furthermore, the ability of both peptides to promote increases in intestinal fluid secretion was evaluated in the in vivo suckling mouse model. When administered per os, guanylin failed to stimulate intestinal secretion. When chymostatin was present in the test solution, guanylin induced intestinal secretion in this assay. In marked contrast, lys-guanylin alone induced diarrhoea in the suckling mouse. The present paper concludes that guanylin undergoes metabolism in target tissues such as the intestine and kidney and its lysine-containing analogue retains full biological activity.
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Affiliation(s)
- Messias S Santos-Neto
- Clinical Research Unit of Federal University of Ceara and Ceara State University, Fortaleza, Brazil
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21
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Wolfe HR, Waldman SA. A comparative molecular field analysis (COMFA) of the structural determinants of heat-stable enterotoxins mediating activation of guanylyl cyclase C. J Med Chem 2002; 45:1731-4. [PMID: 11931628 DOI: 10.1021/jm010208a] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The heat-stable enterotoxin binds to and activates guanylyl cyclase C (GC-C), regulating fluid and electrolyte secretion in intestinal epithelial cells. A COMFA model was developed to predict the primary interactions between GC-C agonists and their receptor. This model predicts that the amide backbone of Cys(5)-Cys(6)-Glu(7)-Leu(8), the beta carbon atoms of Cys(5)-Cys(6), and the side chains of Pro(12), Ala(13), and Ala(15) comprise the primary interactions of GC-C agonists with the receptor surface.
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Affiliation(s)
- Henry R Wolfe
- Targeted Diagnostics and Therapeutics, Inc., 1045 Andrew Drive, West Chester, Pennsylvania 19380, USA.
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22
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Abstract
Escherichia coli is the best-known member of the normal microbiota of the human intestine and a versatile gastrointestinal pathogen. The varieties of E. coli that cause diarrhea are classified into named pathotypes, including enterotoxigenic, enteroinvasive, enteropathogenic and enterohemorrhagic E. coli. Individual strains of each pathotype possess a distinct set of virulence-associated characteristics that determine the clinical, pathological and epidemiological features of the diseases they cause. In the present brief review, we summarize the key distinguishing features of the major pathotypes of diarrheagenic E. coli. Knowledge of the pathogenic mechanisms of these bacteria has led to the development of rational interventions for the treatment and prevention of E. coli-induced diarrhea. In addition, investigations into E. coli virulence are providing useful insights into the origins and evolution of bacterial pathogens more generally.
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Affiliation(s)
- Roy M Robins-Browne
- Department of Microbiology and Immunology, University of Melbourne, Victoria 3010, Australia.
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23
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Gali H, Sieckman GL, Hoffman TJ, Owen NK, Chin DT, Forte LR, Volkert WA. In vivo evaluation of an 111In-labeled ST-peptide analog for specific-targeting of human colon cancers. Nucl Med Biol 2001; 28:903-9. [PMID: 11711309 DOI: 10.1016/s0969-8051(01)00276-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
In vitro competitive binding studies of In-DOTA-NCS-6-Ahx-Phe(19)-ST[1-19] vs. 125I-Tyr(5)-6-Ahx-Phe(19)-ST[1-19] with guanylate cyclase -C (GC-C) receptors on human colon cancer LS-180 cells revealed an IC(50) value of 7.7 +/- 0.1.6 nM. The in vitro cellular residualization studies of the 111In-DOTA-NCS-ST peptide and GC-C receptor mediated stimulated cGMP production with LS-180 cells demonstrates that this peptide selectively binds to LS-180 cells in an agonistic fashion. In vivo biodistribution studies in LS-180 tumor bearing SCID mice demonstrates that the 111In-DOTA-NCS-ST peptide targets the tumor with a specific uptake of 0.94 +/- 0.31%ID/g at 1 hr p.i. and approximately 23% was retained by the tumor at 4 hrs p.i. The radioactivity cleared rapidly from the blood stream with 84.5 +/- 3.4%ID at 1h p.i. found in the urine. High activity in urine and kidney, and minimal activity in liver and intestines, demonstrates preferential clearance of the radioactivity through the renal/urinary pathway. The specific in vitro and in vivo accumulation of the radioactivity by LS-180 human colonic cancer cells highlights the potential of radiometallated-DOTA-ST analogs as diagnostic/therapeutic radiopharmaceuticals.
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Affiliation(s)
- H Gali
- Department of Radiology, University of Missouri-Columbia, Columbia, MO 65211, USA
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24
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Carrithers SL, Taylor B, Cai WY, Johnson BR, Ott CE, Greenberg RN, Jackson BA. Guanylyl cyclase-C receptor mRNA distribution along the rat nephron. REGULATORY PEPTIDES 2000; 95:65-74. [PMID: 11062334 DOI: 10.1016/s0167-0115(00)00139-7] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Guanylin (GN) and uroguanylin (UGN) are two recently identified peptides that have been shown to affect water and electrolyte transport in both the intestine and the kidney. Mechanistically, the effects of both peptides are thought to be mediated by intracellular cGMP which results from ligand binding to a plasma membrane guanylyl cyclase-C (GC-C) receptor. To date, the specific intrarenal site(s) of GN and UGN action have not been established. To begin to address this issue, the present studies utilized semi-quantitative RT-PCR to assess the distribution of GC-C mRNA in specific microdissected segments of the rat nephron. GC-C mRNA expression was highest in the cortical collecting tubule, followed by the proximal convoluted tubule, medullary thick ascending limb and collecting tubule, and thin limbs of Henle's loop. Expression levels were significantly lower in all other segments tested, including the glomerulus. The renal tubular expression pattern for cGMP-dependent protein kinase II (cGK-II) mRNA, which is activated in response to GN/UGN-dependent cGMP accumulation, was similar to that for GC-C. Notably, both GN and UGN mRNAs were also expressed along the nephron. The highest levels of expression for both peptides were detected in the medullary collecting tubule. Lower, but comparable levels of GN and UGN expression also occurred in the cortical collecting tubule, cortical and medullary thick ascending limb, and thin limbs of Henles loop. In the proximal convoluted tubule, GN mRNA expression was also quite high, while UGN mRNA was almost undetectable. The presence of renal GC-C and cGK-II in the kidney are consistent with a proposed endocrine function for GN and UGN. In addition however, the present data suggest that intrarenally synthesized GN and UGN may also contribute to the regulation of renal tubular transport.
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Affiliation(s)
- S L Carrithers
- Division of Infectious Diseases, University of Kentucky and Lexington Veterans Affairs Medical Center, Research Service 151-CDD, 1101 VA Drive, VAMC-D309, 40506, Lexington, KY, USA.
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25
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Abstract
Considerable progress has been made over the last decade in the understanding of mechanisms responsible for the ontogenetic changes of mammalian intestine. This review presents the current knowledge about the development of intestinal transport function in the context of intestinal mucosa ontogeny. The review predominantly focuses on signals that trigger and/or modulate the developmental changes of intestinal transport. After an overview of the proliferation and differentiation of intestinal mucosa, data about the bidirectional traffic (absorption and secretion) across the developing intestinal epithelium are presented. The largest part of the review is devoted to the description of developmental patterns concerning the absorption of nutrients, ions, water, vitamins, trace elements, and milk-borne biologically active substances. Furthermore, the review examines the development of intestinal secretion that has a variety of functions including maintenance of the fluidity of the intestinal content, lubrication of mucosal surface, and mucosal protection. The age-dependent shifts of absorption and secretion are the subject of integrated regulatory mechanisms, and hence, the input of hormonal, nervous, immune, and dietary signals is reviewed. Finally, the utilization of energy for transport processes in the developing intestine is highlighted, and the interactions between various sources of energy are discussed. The review ends with suggestions concerning possible directions of future research.
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Affiliation(s)
- J Pácha
- Institute of Physiology, Czech Academy of Sciences, Prague, Czech Republic.
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26
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Forte LR, London RM, Krause WJ, Freeman RH. Mechanisms of guanylin action via cyclic GMP in the kidney. Annu Rev Physiol 2000; 62:673-95. [PMID: 10845107 DOI: 10.1146/annurev.physiol.62.1.673] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Guanylin, uroguanylin, and lymphoguanylin are small peptides that activate cell-surface guanylate cyclase receptors and influence cellular function via intracellular cGMP. Guanylins activate two receptors, GC-C and OK-GC, which are expressed in intestine and/or kidney. Elevation of cGMP in the intestine elicits an increase in electrolyte and water secretion. Activation of renal receptors by uroguanylin stimulates urine flow and excretion of sodium, chloride, and potassium. Intracellular cGMP pathways for guanylins include activation of PKG-II and/or indirect stimulation of PKA-II. The result is activation of CFTR and/or C1C-2 channel proteins to enhance the electrogenic secretion of chloride and bicarbonate. Similar cellular mechanisms may be involved in the renal responses to guanylin peptides. Uroguanylin serves as an intestinal natriuretic hormone in postprandial states, thus linking the digestive and renal organ systems in a novel endocrine axis. Therefore, uroguanylin participates in the complex physiological processes underlying the saliuresis that is elicited by a salty meal.
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Affiliation(s)
- L R Forte
- Harry S. Truman Memorial Veterans Hospital, Columbia, Missouri.
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27
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Barrett KE, Keely SJ. Chloride secretion by the intestinal epithelium: molecular basis and regulatory aspects. Annu Rev Physiol 2000; 62:535-72. [PMID: 10845102 DOI: 10.1146/annurev.physiol.62.1.535] [Citation(s) in RCA: 368] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Chloride secretion is the major determinant of mucosal hydration throughout the gastrointestinal tract, and chloride transport is also pivotal in the regulation of fluid secretion by organs that drain into the intestine. Moreover, there are pathological consequences if chloride secretion is either reduced or increased such as in cystic fibrosis and secretory diarrhea, respectively. With the molecular cloning of many of the proteins and regulatory factors that make up the chloride secretory mechanism, there have been significant advances in our understanding of this process at the cellular level. Similarly, emerging data have clarified the intercellular relationships that govern the extent of chloride secretion. The goal of our article is to review this area of investigation, with an emphasis on recent developments and their implications for the physiology and pathophysiology of chloride transport.
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Affiliation(s)
- K E Barrett
- Department of Medicine, University of California, San Diego, School of Medicine, California 92103, USA.
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28
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Abstract
Enteric pathogens finely regulate the expression of virulence genes in reply to stimuli generated by the intestinal environment. This minireview focuses on recently discovered strategies developed by enteric bacteria to cause intestinal secretion through the elaboration of factors that share structure and function with specific host counterparts. Such bacterial antigens appear to interfere largely with the epithelial cell signalling that physiologically regulates the numerous and, as yet not fully elucidated, mechanisms controlling both the transcellular and the paracellular secretion pathways. Heat-stable enterotoxins (STs) elaborated by enterotoxigenic Escherichia coli and the enteroaggregative E. coli enterotoxin (EAST1) are both typical examples of enteric toxins that activate the transcellular secretion pathway by mimicking guanylin, the endogenous modulator of cGMP signalling. Alternative strategies have been developed by Salmonella to induce intestinal secretion through the elaboration of a factor (SopB) that resembles at least two of the host cell 4-phosphatases, enzymes that activate the Ca-dependent transcellular secretion pathway. Finally, Vibrio cholerae has developed innovative tactics to activate the paracellular secretion pathway through the elaboration of Zonula occludens toxin (Zot), a factor that mimics a recently described physiological modulator of intercellular tight junctions.
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Affiliation(s)
- S Uzzau
- Dipartimento di Scienze Biomediche, Sassari, Italy
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29
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Forte LR, London RM, Freeman RH, Krause WJ. Guanylin peptides: renal actions mediated by cyclic GMP. Am J Physiol Renal Physiol 2000; 278:F180-91. [PMID: 10662722 DOI: 10.1152/ajprenal.2000.278.2.f180] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The guanylin family of cGMP-regulating peptides has three subclasses of peptides containing either three intramolecular disulfides found in bacterial heat-stable enterotoxins (ST), or two disulfides observed in guanylin and uroguanylin, or a single disulfide exemplified by lymphoguanylin. These small, heat-stable peptides bind to and activate cell-surface receptors that have intrinsic guanylate cyclase (GC) activity. Two receptor GC signaling molecules have been identified that are highly expressed in the intestine (GC-C) and/or the kidney (OK-GC) and are selectively activated by the guanylin peptides. Stimulation of cGMP production in renal target cells by guanylin peptides in vivo or ex vivo elicits a long-lived diuresis, natriuresis, and kaliuresis. Activation of GC-C receptors in target cells of intestinal mucosa markedly stimulates the transepithelial secretion of Cl(-) and HCO(-)/(3), causing enhanced secretion of fluid and electrolytes into the intestinal lumen. Bacterial ST peptides act as mimics of guanylin and uroguanylin in the intestine, which provide a cellular mechanism underlying the diarrhea caused by ST-secreting strains of Escherichia coli. Uroguanylin and guanylin may participate in a novel endocrine axis linking the digestive system and kidney as a physiological mechanism that influences Na(+) homeostasis. Guanylin, uroguanylin, and/or lymphoguanylin may also serve within intrarenal signaling pathways controlling cGMP production in renal target cells. Thus we propose that guanylin regulatory peptides participate in a complex multifactorial biological process that evolved to regulate the urinary excretion of NaCl when dietary salt levels exceed the body's physiological requirements. This highly integrated and redundant mechanism allows the organism to maintain sodium balance by eliminating excess NaCl in the urine. Uroguanylin, in particular, may be a prototypical "intestinal natriuretic hormone."
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Affiliation(s)
- L R Forte
- Harry S. Truman Memorial Veterans' Hospital, School of Medicine, Missouri University, Columbia, Missouri 65212, USA.
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30
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Forte LR. Guanylin regulatory peptides: structures, biological activities mediated by cyclic GMP and pathobiology. REGULATORY PEPTIDES 1999; 81:25-39. [PMID: 10395405 DOI: 10.1016/s0167-0115(99)00033-6] [Citation(s) in RCA: 102] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The guanylin family of bioactive peptides consists of three endogenous peptides, including guanylin, uroguanylin and lymphoguanylin, and one exogenous peptide toxin produced by enteric bacteria. These small cysteine-rich peptides activate cell-surface receptors, which have intrinsic guanylate cyclase activity, thus modulating cellular function via the intracellular second messenger, cyclic GMP. Membrane guanylate cyclase-C is an intestinal receptor for guanylin and uroguanylin that is responsible for stimulation of Cl- and HCO3- secretion into the intestinal lumen. Guanylin and uroguanylin are produced within the intestinal mucosa to serve in a paracrine mechanism for regulation of intestinal fluid and electrolyte secretion. Enteric bacteria secrete peptide toxin mimics of uroguanylin and guanylin that activate the intestinal receptors in an uncontrolled fashion to produce secretory diarrhea. Opossum kidney guanylate cyclase is a key receptor in the kidney that may be responsible for the diuretic and natriuretic actions of uroguanylin in vivo. Uroguanylin serves in an endocrine axis linking the intestine and kidney where its natriuretic and diuretic actions contribute to the maintenance of Na+ balance following oral ingestion of NaCl. Lymphoguanylin is highly expressed in the kidney and myocardium where this unique peptide may act locally to regulate cyclic GMP levels in target cells. Lymphoguanylin is also produced in cells of the lymphoid-immune system where other physiological functions may be influenced by intracellular cyclic GMP. Observations of nature are providing insights into cellular mechanisms involving guanylin peptides in intestinal diseases such as colon cancer and diarrhea and in chronic renal diseases or cardiac disorders such as congestive heart failure where guanylin and/or uroguanylin levels in the circulation and/or urine are pathologically elevated. Guanylin peptides are clearly involved in the regulation of salt and water homeostasis, but new findings indicate that these novel peptides have diverse physiological roles in addition to those previously documented for control of intestinal and renal function.
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Affiliation(s)
- L R Forte
- The Harry S. Truman Memorial V.A. Hospital, Columbia, MO 65212, USA.
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31
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Hasegawa M, Kawano Y, Matsumoto Y, Hidaka Y, Fujii J, Taniguchi N, Wada A, Hirayama T, Shimonishi Y. Expression and characterization of the extracellular domain of guanylyl cyclase C from a baculovirus and Sf21 insect cells. Protein Expr Purif 1999; 15:271-81. [PMID: 10092487 DOI: 10.1006/prep.1998.1019] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Guanylyl cyclase (GC)-C, a single-transmembrane receptor protein for heat-stable enterotoxin, guanylin, and uroguanylin, and its N-terminal extracellular domain were prepared at a high level of expression from a system constructed of Sf21 insect cells and recombinant baculovirus. The recombinant GC-C, containing the complete sequence, retained its binding affinity to heat-stable enterotoxin with a KD value (6.2 x 10(-10) M) and cyclase catalytic activity at a level similar to those of GC-C expressed in mammalian cell lines, such as COS-7. The N-terminal extracellular domain was prepared in a form which contained the hexahistidine tail at its C-terminus and was purified as a homogenous protein by Con A and Ni-chelating affinity chromatography from the culture medium of the insect cells. The purified N-terminal extracellular domain of GC-C exhibited the high (KD = 4 x 10(-10) M) and low (KD = 7 x 10(-8) M) affinity sites in binding to heat-stable enterotoxin. These results clearly indicate that the N-terminal extracellular domain of GC-C possesses the same biochemical characteristics as the complete GC-C protein even in the membrane-free form. Moreover, the extracellular domain is able to form an oligomer in a ligand-dependent manner, suggesting that the N-terminal extracellular domains interact with one another in binding to ligands.
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Affiliation(s)
- M Hasegawa
- Institute for Protein Research, Osaka University, Yamadaoka 3-2, Suita, Osaka, 565, Japan
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32
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Fasano A. Cellular microbiology: can we learn cell physiology from microorganisms? THE AMERICAN JOURNAL OF PHYSIOLOGY 1999; 276:C765-76. [PMID: 10199806 DOI: 10.1152/ajpcell.1999.276.4.c765] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Cellular microbiology is a new discipline that is emerging at the interface between cell biology and microbiology. The application of molecular techniques to the study of bacterial pathogenesis has made possible discoveries that are changing the way scientists view the bacterium-host interaction. Today, research on the molecular basis of the pathogenesis of infective diarrheal diseases of necessity transcends established boundaries between cell biology, bacteriology, intestinal pathophysiology, and immunology. The use of microbial pathogens to address questions in cell physiology is just now yielding promising applications and striking results.
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Affiliation(s)
- A Fasano
- Department of Pediatrics and Physiology, and Gastrointestinal Pathophysiology Section, Center for Vaccine Development, University of Maryland, School of Medicine, Baltimore, Maryland 21201, USA.
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33
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Forte LR, Eber SL, Fan X, London RM, Wang Y, Rowland LM, Chin DT, Freeman RH, Krause WJ. Lymphoguanylin: cloning and characterization of a unique member of the guanylin peptide family. Endocrinology 1999; 140:1800-6. [PMID: 10098518 DOI: 10.1210/endo.140.4.6630] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Guanylin and uroguanylin are small peptides containing two disulfide bonds that activate membrane guanylate cyclase-receptors in the intestine, kidney and other epithelia. Hybridization assays with a uroguanylin complementary DNA (cDNA) detected uroguanylin-like messenger RNAs (mRNAs) in the opossum spleen and testis, but these transcripts are larger than uroguanylin mRNAs. RT of RNA from spleen to produce cDNAs for amplification in the PCR followed by cloning and sequencing revealed a novel lymphoid-derived cDNA containing an open reading frame encoding a 109-amino acid polypeptide. This protein shares 84% and 40% of its residues with preprouroguanylin and preproguanylin, respectively. A 15-amino acid, uroguanylin-like peptide occurs at the COOH-terminus of the precursor polypeptide. However, this peptide is unique in having only three cysteine residues. We named the gene and its peptide product lymphoguanylin because the source of the first cDNA isolated was spleen and its mRNA is expressed in all of the lymphoid tissues tested. A 15-amino acid form of lymphoguanylin containing a single disulfide bond was synthesized that activates the guanylate cyclase receptors of human T84 intestinal and opossum kidney (OK) cells, although with less potency than uroguanylin and guanylin. Northern and/or RT-PCR assays detected lymphoguanylin mRNA transcripts in many tissues and organs of opossums, including those within the lymphoid/immune, cardiovascular/renal, reproductive, and central nervous organ systems. Lymphoguanylin joins guanylin and uroguanylin in a growing family of peptide agonists that activate transmembrane guanylate cyclase receptors, thus influencing target cell function via the intracellular second messenger, cGMP.
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Affiliation(s)
- L R Forte
- Harry S. Truman Memorial Veterans' Hospital, Department of Pharmacology, School of Medicine, Missouri University, Columbia 65212, USA.
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Ieda H, Naruse S, Kitagawa M, Ishiguro H, Hayakawa T. Effects of guanylin and uroguanylin on rat jejunal fluid and electrolyte transport: comparison with heat-stable enterotoxin. REGULATORY PEPTIDES 1999; 79:165-71. [PMID: 10100931 DOI: 10.1016/s0167-0115(98)00162-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The effects of rat guanylin, human guanylin, human uroguanylin and STa on net fluid and electrolyte transport in the closed jejunal loop were compared in anesthetized rats. STa administered into the lumen caused a concentration-dependent (10(-8) to 10(-6) M) inhibition of net fluid and NaCl absorption in the jejunal loop. Uroguanylin had a similar but weaker effect than STa. Both rat and human guanylin inhibited fluid and NaCl absorption only at 10(-6) M. Their order of potency was STa > human uroguanylin > rat guanylin = human guanylin. Changing the luminal pH from 5 to 8 failed to affect the action of guanylin on fluid absorption. Both STa and uroguanylin, but not guanylin, increased the luminal pH by stimulating bicarbonate secretion. Pretreatment of the jejunal loop with guanylin (10(-6) M) 5 min before the instillation of STa (10(-7) M) significantly reduced the inhibitory effect of STa on fluid absorption. It is concluded that guanylin and uroguanylin administered into the rat jejunal lumen have an STa-like action on fluid and electrolyte transport. Guanylin may act as an endogenous antagonist of STa in the rat jejunum and prevent excessive fluid loss by STa.
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Affiliation(s)
- H Ieda
- Department of Internal Medicine II, Nagoya University School of Medicine, Japan
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Marx UC, Klodt J, Meyer M, Gerlach H, Rösch P, Forssmann WG, Adermann K. One peptide, two topologies: structure and interconversion dynamics of human uroguanylin isomers. THE JOURNAL OF PEPTIDE RESEARCH : OFFICIAL JOURNAL OF THE AMERICAN PEPTIDE SOCIETY 1998; 52:229-40. [PMID: 9774236 DOI: 10.1111/j.1399-3011.1998.tb01480.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The peptide hormone uroguanylin stimulates chloride secretion via activation of intestinal guanylyl cyclase C (GC-C). It is characterized by two disulfide bonds in a 1-3/2-4 pattern that causes the existence of two topological stereoisomers of which only one induces intracellular cGMP elevation. To obtain an unambiguous structure-function relationship of the isomers, we determined the solution structure of the separated uroguanylin isoforms using NMR spectroscopy. Both isomers adopt well-defined structures that correspond to those of the isomers of the related peptide guanylin. Furthermore, the structure of the GC-C-activating uroguanylin isomer A closely resembles the structure of the agonistic Escherichia coli heat-stable enterotoxin. Compared with guanylin isomers, the conformational interconversion of uroguanylin isomers is retarded significantly. As judged from chromatography and NMR spectroscopy, both uroguanylin isoforms are stable at low temperatures, but are subject to a slow pH-dependent mutual isomerization at 37 degrees C with an equilibrium isomer ratio of approximately 1:1. The conformational exchange is most likely under the sterical control of the carboxy-terminal leucine. These results imply that GC-C is activated by ligands exhibiting the molecular framework corresponding to the structure of uroguanylin isomer A.
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Affiliation(s)
- U C Marx
- Niedersächsisches Institut für Peptid-Forschung, Hannover, Germany
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36
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Fonteles MC, Greenberg RN, Monteiro HS, Currie MG, Forte LR. Natriuretic and kaliuretic activities of guanylin and uroguanylin in the isolated perfused rat kidney. THE AMERICAN JOURNAL OF PHYSIOLOGY 1998; 275:F191-7. [PMID: 9691007 DOI: 10.1152/ajprenal.1998.275.2.f191] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Guanylin and uroguanylin are novel peptides that activate membrane guanylate cyclases found in the kidney and intestine. We compared the effects of these peptides in the isolated perfused rat kidney. Both peptides are natriuretic and kaliuretic in this preparation. Uroguanylin (0.19-1.9 microM) increased glomerular filtration rate from 0.77 +/- 0.07 to 1.34 +/- 0.3 ml . g-1 . min-1 at the highest concentration. A maximal increase in Na+ excretion was achieved at 0. 66 microM uroguanylin, with a reduction in fractional Na+ reabsorption from 78.7 +/- 1.7 to 58.8 +/- 4.4%. The highest dose of uroguanylin increased kaliuresis by 50%. Osmolar clearance doubled at the highest concentration of uroguanylin tested (P < 0.05). Guanylin also elicited a natriuresis and kaliuresis but appeared to be less potent than uroguanylin. The highest concentration of guanylin (1.3 microM) decreased fractional Na+ reabsorption from 73. 9 +/- 2.4 to 64.5 +/- 4.0%, but lower doses were ineffective. Guanylin stimulated urine K+ excretion at the lowest concentration tested (0.33 microM) without any effect on Na+ excretion. These peptides may influence salt and water homeostasis by biological effects in the kidney that are mediated by the intracellular second messenger, cGMP.
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Affiliation(s)
- M C Fonteles
- Clinical Research Unit, Federal University of Ceara and Ceara State University, 60434 Fortaleza, Brazil
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37
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Affiliation(s)
- A Fasano
- Division of Pediatric Gastroenterology and Nutrition, Center for Vaccine Development, University of Maryland, School of Medicine, Baltimore 21201, USA
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John M, Wiedenmann B, Kruhøffer M, Adermann K, Ankorina-Stark I, Schlatter E, Ahnert-Hilger G, Forssmann WG, Kuhn M. Guanylin stimulates regulated secretion from human neuroendocrine pancreatic cells. Gastroenterology 1998; 114:791-7. [PMID: 9516400 DOI: 10.1016/s0016-5085(98)70593-1] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
BACKGROUND & AIMS Gastroenteropancreatic neuroendocrine cells secrete chemical messengers in a calcium-dependent fashion. So far, other second messenger systems involved in regulated secretion have gained little attention. The aim of this study was to characterize guanosine 3',5'-cyclic monophosphate (cGMP)-mediated vesicular secretion in pancreatic neuroendocrine cells. METHODS In a human pancreatic cell line, BON, cyclic nucleotide levels and chromogranin A release were monitored with specific immunoassays. Uptake and release of gamma-aminobutyric acid were measured. Intracellular Ca2+ concentration was monitored with fura-2. Guanylyl cyclase C was analyzed by reverse-transcription polymerase chain reaction. RESULTS Guanylin increased cGMP concentrations in BON cells via guanylyl cyclase C. Stimulation of the cGMP pathway by guanylin or Escherichia coli heat-stable enterotoxin increased the release of chromogranin A and gamma-aminobutyric acid from BON cells. This effect was mimicked by the cGMP analogue 8-bromo-cGMP. CONCLUSIONS Guanylin and STa stimulate the regulated secretion from BON cells via guanylyl cyclase C and cGMP. Our study yields novel information about secretory properties of guanylin, mediated via a signal transduction pathway, increasing cGMP and leading to regulated secretion of neuroendocrine cells.
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Affiliation(s)
- M John
- Department of Gastroenterology, Klinikum Benjamin Franklin, Freie Universität Berlin, Berlin, Germany
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Abstract
Escherichia coli is the predominant nonpathogenic facultative flora of the human intestine. Some E. coli strains, however, have developed the ability to cause disease of the gastrointestinal, urinary, or central nervous system in even the most robust human hosts. Diarrheagenic strains of E. coli can be divided into at least six different categories with corresponding distinct pathogenic schemes. Taken together, these organisms probably represent the most common cause of pediatric diarrhea worldwide. Several distinct clinical syndromes accompany infection with diarrheagenic E. coli categories, including traveler's diarrhea (enterotoxigenic E. coli), hemorrhagic colitis and hemolytic-uremic syndrome (enterohemorrhagic E. coli), persistent diarrhea (enteroaggregative E. coli), and watery diarrhea of infants (entero-pathogenic E. coli). This review discusses the current level of understanding of the pathogenesis of the diarrheagenic E. coli strains and describes how their pathogenic schemes underlie the clinical manifestations, diagnostic approach, and epidemiologic investigation of these important pathogens.
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Affiliation(s)
- J P Nataro
- Department of Medicine, University of Maryland School of Medicine, Baltimore 21201, USA.
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40
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Schulz S, Lopez MJ, Kuhn M, Garbers DL. Disruption of the guanylyl cyclase-C gene leads to a paradoxical phenotype of viable but heat-stable enterotoxin-resistant mice. J Clin Invest 1997; 100:1590-5. [PMID: 9294128 PMCID: PMC508341 DOI: 10.1172/jci119683] [Citation(s) in RCA: 126] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Heat-stable enterotoxins (STa), which cause an acute secretory diarrhea, have been suggested to mediate their actions through the guanylyl cyclase-C (GC-C) receptor. The GC-C gene was disrupted by insertion of neo into exon 1 and subsequent homologous recombination. GC-C null mice contained no detectable GC-C protein. Intestine mucosal guanylyl cyclase activity was approximately 16-fold higher in wild-type mice than in the GC-C null mice, and STa-stimulable guanylyl cyclase activity was absent in the null animals. Thus, GC-C is the major cyclase activity present in the intestine, and also completely accounts for the STa-induced elevations of cGMP. Gavage with STa resulted in marked fluid accumulation within the intestine of wild-type and heterozygous suckling mice, but GC-C null animals were resistant. In addition, infection with enterotoxigenic bacteria that produce STa led to diarrhea and death in wild-type and heterozygous mice, while the null mice were protected. Cholera toxin, in contrast, continued to cause diarrhea in GC-C null mice, demonstrating that the cAMP signaling pathway remained intact. Markedly different diets (high carbohydrate, fat, or protein) or the inclusion of high salt (K+, Na+) in the drinking water or diet also did not severely affect the null animals. Given that GC-C is a major intestinal receptor in all mammals, the pressure to retain a functional GC-C in the face of diarrhea-inflicted mortality remains unexplained. Therefore, GC-C likely provides a protective effect against stressors not yet tested, possibly pathogens other than noninvasive enterotoxigenic bacteria.
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MESH Headings
- Animals
- Animals, Newborn
- Blotting, Southern
- Blotting, Western
- Body Weight/drug effects
- Cells, Cultured
- Cholera Toxin/pharmacology
- Enterotoxins/pharmacology
- Escherichia coli/pathogenicity
- Food, Formulated
- Guanylate Cyclase/genetics
- Guanylate Cyclase/metabolism
- Guanylate Cyclase/physiology
- Intestinal Mucosa/enzymology
- Mice
- Mice, Inbred BALB C
- Mice, Inbred C57BL
- Receptors, Enterotoxin
- Receptors, Guanylate Cyclase-Coupled
- Receptors, Peptide/genetics
- Receptors, Peptide/physiology
- Sodium Chloride, Dietary/pharmacology
- Survival Rate
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Affiliation(s)
- S Schulz
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, Texas 75235-9050, USA
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41
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Klodt J, Kuhn M, Marx UC, Martin S, Rösch P, Forssmann WG, Adermann K. Synthesis, biological activity and isomerism of guanylate cyclase C-activating peptides guanylin and uroguanylin. THE JOURNAL OF PEPTIDE RESEARCH : OFFICIAL JOURNAL OF THE AMERICAN PEPTIDE SOCIETY 1997; 50:222-30. [PMID: 9309586 DOI: 10.1111/j.1399-3011.1997.tb01188.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Recently, the peptides guanylin and uroguanylin were identified as endogenous ligands of the membrane-bound guanylate cyclase C (GC-C) that is mainly expressed in the intestinal epithelium. In the present study, bioactive guanylin and uroguanylin have been prepared by solid-phase methodology using Fmoc/HBTU chemistry. The two disulfide bonds with relative 1/3 and 2/4 connectivity have been introduced selectively by air oxidation of thiol groups and iodine treatment of Cys(Acm) residues. Using this strategy, several sequential derivatives were prepared. Temperature-dependent HPLC characterization of the bioactive products revealed that guanylin-related peptides exist as a mixture of two compounds. The isoforms are interconverted within approximately 90 min, which prevents their separate characterization. This effect was not detected for uroguanylin-like peptides. Synthetic peptides were tested for their potential to activate GC-C in cultured human colon carcinoma cells (T84), known to express high levels of GC-C. The results obtained show that both disulfide bonds are necessary for GC-C activation. The presence of the amino-terminally neighboring residues of Cys104 for guanylin and Cys100 for uroguanylin has been found to be essential for GC-C stimulation. Unexpectedly, a hybrid peptide obtained from substitution of the central tripeptide AYA of guanylin by the tripeptide VNV of uroguanylin was not bioactive.
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Affiliation(s)
- J Klodt
- Niedersächsisches Institut für Peptid-Forschung (IPF), Hannover, Germany
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42
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Krause WJ, Freeman RH, Eber SL, Hamra FK, Currie MG, Forte LR. Guanylyl cyclase receptors and guanylin-like peptides in reptilian intestine. Gen Comp Endocrinol 1997; 107:229-39. [PMID: 9245531 DOI: 10.1006/gcen.1997.6921] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Receptors for guanylin and uroguanylin were identified on the mucosal surface of enterocytes lining the intestine of the bobtail skink (Tiliqua rugosa), king's skink (Egernia kingii), and knight anole (Anolis equestris) by receptor autoradiography using 125I-ST (Escherichia coli heat-stable enterotoxin) as the radioligand. Specific, high-affinity binding of 125I-ST to receptors was found on the microvillus border of enterocytes and little or no specific binding of 125I-ST was observed in other strata comprising the gut wall. The American alligator (Alligator mississippensis) also exhibited receptor binding, but unlike the other three species had relatively high levels of apparent nonspecific binding. A comparison of intestinal cGMP accumulation responses between the American alligator and the knight anole demonstrated a greater magnitude of cGMP responses to ST and guanylin in vitro in the knight anole relative to the tissue cGMP accumulation responses of alligators. Treatment with ST resulted in markedly greater tissue cGMP accumulation responses in both species compared to treatment with guanylin. To complete a paracrine signaling pathway in reptilian intestine, guanylin-like peptides that stimulated cGMP accumulation in human T84 intestinal cells were isolated from the intestinal mucosa of alligators. We conclude that functional receptor-guanylyl cyclases and one or more endogenous guanylin/uroguanylin-like peptides occur in the intestinal tract of reptiles as well as in the intestines of mammals and birds. Thus, higher vertebrates have a conserved signaling pathway that regulates intestinal function through the first-messenger peptides, guanylin and/or uroguanylin, and the intracellular second messenger, cGMP.
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Affiliation(s)
- W J Krause
- School of Medicine, University of Missouri, Columbia, Missouri, 65212, USA
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Sears CL, Kaper JB. Enteric bacterial toxins: mechanisms of action and linkage to intestinal secretion. Microbiol Rev 1996; 60:167-215. [PMID: 8852900 PMCID: PMC239424 DOI: 10.1128/mr.60.1.167-215.1996] [Citation(s) in RCA: 189] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Affiliation(s)
- C L Sears
- Division of Infectious Diseases, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
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Carrithers SL, Parkinson SJ, Goldstein SD, Park PK, Urbanski RW, Waldman SA. Escherichia coli heat-stable enterotoxin receptors. A novel marker for colorectal tumors. Dis Colon Rectum 1996; 39:171-81. [PMID: 8620784 DOI: 10.1007/bf02068072] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
PURPOSE Receptors for Escherichia coli heat-stable toxin (ST) are selectively expressed in membranes of intestinal mucosa cells and colon carcinoma cells in vitro, suggesting their use as a marker for colorectal tumors in vivo. The present studies examined the expression and function of ST receptors in normal human tissues and primary and metastatic colorectal tumors obtained from patients at surgery. METHODS Surgical specimens were obtained as follows: from normal colon; from primary adenocarcinomas from all anatomic divisions of the colon and rectum; from gallbladder, kidney, liver, lung, lymph node, ovary, peritoneum, stomach; and from colon carcinomas metastatic to liver, lung, lymph node, ovary, and peritoneum. Membranes prepared from these specimens were assessed for the presence and functional characteristics of ST receptors. RESULTS ST bound specifically to membranes from each division of normal colon and rectum and all primary and metastatic colorectal tumors examined. The affinity and density of ST receptors were similar in tumors of different grades and from various metastatic sites. ST-receptor interaction was coupled to activation of guanylyl cyclase in all normal samples of colon and rectum and all primary and metastatic colorectal tumors examined. In contrast, neither ST binding nor ST activation of guanylyl cyclase was detected in any extraintestinal tissues examined. CONCLUSIONS Functional ST receptors are expressed in normal colonic tissue and primary and metastatic colorectal tumors but not by extraintestinal tissues in humans. Expression of ST receptors does not vary as a function of the metastatic site or grade of these tumors. Receptors expressed by colorectal tumors retain their characteristic function, with binding of ST coupled to activation of guanylyl cyclase. These studies support the suggestion that ST receptors represent a specific marker for human colorectal tumors that may have use as a target for directing diagnostics and therapeutics to these tumors in vivo.
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Affiliation(s)
- S L Carrithers
- Department of Medicine, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, USA
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Li Z, Taylor-Blake B, Light AR, Goy MF. Guanylin, an endogenous ligand for C-type guanylate cyclase, is produced by goblet cells in the rat intestine. Gastroenterology 1995; 109:1863-75. [PMID: 7498651 DOI: 10.1016/0016-5085(95)90753-x] [Citation(s) in RCA: 53] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
BACKGROUND & AIMS Guanylin activates an intestinal guanylate cyclase (GCC) and stimulates electrolyte movement across the gut epithelium. Cells expressing guanylin messenger RNA have been localized to the epithelial cell layer of the intestine; however, the identity of the guanylin-producing cells has not been determined. The aim of this study was to identify cells that express guanylin in the rat intestine. METHODS Antibodies were raised against defined proguanylin epitopes, evaluated by Western blotting, and used for immunoperoxidase histochemistry. RESULTS Guanylin-like immunoreactivity was localized to a subset of goblet cells. In the small intestine, most, perhaps all, goblet cells in the villi were immunopositive, as were some goblet cells in upper crypts; however, goblet cells deep within crypts were unlabeled. In the colon, goblet cells clustered in the necks and around the openings of crypts were immunopositive, whereas (as in the small intestine) goblet cells in deeper crypt regions were unlabeled. In some animals, immunoreactive columnar epithelial cells were also observed in the colon (although such cells were not apparent in the small intestine). Relative labeling of columnar cells varied from animal to animal. CONCLUSIONS Guanylin is expressed in mature goblet cells. If secreted in conjunction with mucin, it could play a role in the hydration of mucus.
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Affiliation(s)
- Z Li
- Department of Physiology, University of North Carolina, Chapel Hill, USA
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Brandsch M, Ramamoorthy S, Marczin N, Catravas JD, Leibach JW, Ganapathy V, Leibach FH. Regulation of taurine transport by Escherichia coli heat-stable enterotoxin and guanylin in human intestinal cell lines. J Clin Invest 1995; 96:361-9. [PMID: 7615806 PMCID: PMC185208 DOI: 10.1172/jci118042] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
The human colon carcinoma cell lines Caco-2 and HT-29 take up taurine actively. Treatment of Caco-2 cells with Escherichia coli heat-stable enterotoxin (STa) or with guanylin inhibited taurine uptake by approximately 40%. In contrast, neither STa nor guanylin changed the uptake of taurine in HT-29 cells. The inhibition in Caco-2 cells was associated with a decrease in the maximal velocity as well as in the affinity of the transporter. STa caused a 21-fold increase in guanosine 3',5'-cyclic monophosphate (cGMP) levels in Caco-2 cells with no change in cAMP levels. Neither cGMP nor cAMP levels were affected by STa treatment in HT-29 cells. Experiments with protein kinase inhibitors suggested that protein kinase A may mediate the observed effects of STa on taurine uptake. In accordance with this suggestion, treatment of Caco-2 cells with cholera toxin, which elevated intracellular cAMP levels, was found to inhibit taurine uptake. The steady state levels of the taurine transporter mRNA transcripts were not altered as a result of STa treatment. Studies with Caco-2 cells grown on permeable filters revealed that STa acts from the apical side. The taurine uptake from the apical side was inhibited by STa, but the taurine uptake from the basolateral side remained unaffected. It is suggested that the activity of the intestinal taurine transporter may be regulated by protein kinase A at a posttranslational level and that the intestinal absorption of taurine may be impaired during infection with enterotoxigenic strains of E. coli.
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Affiliation(s)
- M Brandsch
- Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta 30912-2100, USA
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47
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Carrithers SL, Parkinson SJ, Goldstein S, Park P, Robertson DC, Waldman SA. Escherichia coli heat-stable toxin receptors in human colonic tumors. Gastroenterology 1994; 107:1653-61. [PMID: 7958675 DOI: 10.1016/0016-5085(94)90804-4] [Citation(s) in RCA: 70] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
BACKGROUND/AIMS Escherichia coli heat-stable enterotoxins (ST) are small peptides of 18 or 19 amino acids that bind to specific cell surface receptors located on the intestinal brush border and activate guanylate cyclase, resulting in an increase in the intracellular cyclic guanosine 3',5'-monophosphate content of the cell. The present study examined whether receptors for ST are expressed by primary and metastatic human colonic tumors in vivo. METHODS Plasma membranes prepared from surgical tissue samples from normal colon, liver and lung, primary colonic adenocarcinomas, and colon carcinomas metastatic to lung and liver were analyzed for the structural and functional characteristics of constituent ST receptors. RESULTS All primary and metastatic colonic tumors examined bound ST, showing receptors of high (pmol/L) and low (nmol/L) affinity with densities that were similar to those in normal colon. Also, affinity cross-linking of labeled ST to membranes showed similar binding proteins in primary and metastatic tumors and normal colon. ST binding and affinity-labeled proteins were not detected in normal extraintestinal tissues. Guanylate cyclase was activated by ST in membranes from all colonic tumors studied, with efficacies and potencies that were similar to those in normal colon. ST did not activate this enzyme in normal extraintestinal tissues. CONCLUSIONS Receptors for ST are expressed by primary and metastatic human colonic tumors in vivo, with structural and functional characteristics that are similar to those in normal human colon.
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Affiliation(s)
- S L Carrithers
- Department of Medicine, Thomas Jefferson University, Philadelphia, Pennsylvania
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48
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Kuhn M, Adermann K, Jähne J, Forssmann WG, Rechkemmer G. Segmental differences in the effects of guanylin and Escherichia coli heat-stable enterotoxin on Cl- secretion in human gut. J Physiol 1994; 479 ( Pt 3):433-40. [PMID: 7837099 PMCID: PMC1155761 DOI: 10.1113/jphysiol.1994.sp020307] [Citation(s) in RCA: 54] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
1. Mucosally added synthetic guanylin and Escherichia coli heat-stable enterotoxin (STa) increased short-circuit current (ISC) across isolated muscle-stripped human intestine in vitro. 2. Serosal bumetanide inhibited ISC responses indicating that guanylin and STa stimulate electrogenic chloride secretion. 3. ISC responses were markedly greater in the colon than in the jejunum. 4. Pretreatment with indomethacin did not significantly alter the effects of guanylin and STa. 5. Both peptides induced concentration-dependent increases in the cyclic GMP content of human intestinal mucosa in vitro; cyclic AMP levels remained unchanged. 6. In contrast to ISC responses, increases in cyclic GMP content induced by guanylin and STa were markedly greater in the jejunum than in the colon. 7. Sodium nitroprusside (SNP) but not human alpha-atrial natriuratic peptide (CDD/ANP(99-126)) increased chloride secretion in human intestine; both agents induced small increases in intestinal cyclic GMP content. 8. Guanylin, STa and the nitric oxide (NO) donor SNP increased electrogenic chloride secretion across human intestinal mucosa in vitro by stimulation of cyclic GMP. The discrepancy between the effects on chloride secretion and intracellular cyclic GMP content suggest different cellular action sites of guanylin and STa in human small and large intestine.
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Affiliation(s)
- M Kuhn
- Lower Saxony Institute for Peptide Research, Hannover, Germany
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