scholarly journals A non-olfactory shark adenosine receptor activates CFTR with unique pharmacology and structural features

2020 ◽  
Author(s):  
Sumeet Bhanot ◽  
Gabriele Hemminger ◽  
Stephen G. Aller ◽  
John N. Forrest
Keyword(s):  
Adenosine Receptor ◽  
Chloride Channel ◽  
Homology Model ◽  
Chloride Secretion ◽  
Structural Features ◽  
Rectal Gland ◽  
Pharmacological Profile ◽  
Current Voltage ◽  
Profile Characteristic

AbstractAdenosine receptors (ADORs) are G-protein coupled purinoceptors that have several functions including regulation of chloride secretion via CFTR in human airway and kidney. We cloned an ADOR from Squalus acanthias (shark) that likely regulates CFTR in the rectal gland. Phylogenic- and expression-analyses indicate that elasmobranch ADORs are non-olfactory, and appear to represent extant predecessors of mammalian ADORs. We therefore designate the shark ADOR as the A0 receptor. We co-expressed A0 with CFTR in Xenopus laevis oocytes and characterized the coupling of A0 to the chloride channel. Two electrode voltage clamping was performed and current-voltage (I-V) responses were recorded to monitor CFTR status. Only in A0- and CFTR-co-injected oocytes did adenosine analogs produce a significant dose-dependent activation of CFTR consistent with its electrophysiological signature. A pharmacological profile for A0 was obtained for ADOR agonists and antagonists that differed markedly from all mammalian ADOR subtypes (agonists: R-PIA > S-PIA > CGS21680 > CPA > 2ClADO > CV1808 = DPMA > NECA) and (antagonists: DPCPX > PD115199 > 8PT > CGC > CGS15943). Structures of human ADORs permitted a high-confidence homology model of the shark A0 core which revealed unique structural features of ancestral receptors. We conclude: (1) A0 is a novel and unique adenosine receptor ancestor by functional and structural criteria; (2) A0 likely activates CFTR in vivo and this receptor activates CFTR in oocytes indicating an evolutionary coupling between ADORs and chloride secretion; and (3) A0 appears to be a non-olfactory evolutionary ancestor of all four mammalian ADOR subtypes.Significance StatementWe have cloned and characterized an ancient adenosine receptor from sharks that is unlikely to be olfactory in function. The shark receptor, which we designate as A0, has a unique pharmacological profile, characteristic structural features, and is also highly likely to be the dominant ADOR regulator of the shark ancient ortholog of the Cystic Fibrosis chloride channel, called CFTR.

scholarly journals A non-olfactory shark adenosine receptor activates CFTR with unique pharmacology and structural features

2021 ◽  
Author(s):  
Sumeet Bhanot ◽  
Gabriele Hemminger ◽  
Cole L. Martin ◽  
Stephen G. Aller ◽  
John N. Forrest
Keyword(s):  
Adenosine Receptor ◽  
Homology Model ◽  
Chloride Secretion ◽  
Structural Features ◽  
Rectal Gland ◽  
Xenopus Laevis Oocytes ◽  
Current Voltage ◽  
Evolutionary Coupling ◽  
G Protein Coupled

Adenosine receptors (ADORs) are G-protein coupled purinoceptors that have several functions including regulation of chloride secretion via CFTR in human airway and kidney. We cloned an ADOR from Squalus acanthias (shark) that likely regulates CFTR in the rectal gland. Phylogenic- and expression- analyses indicate that elasmobranch ADORs are non-olfactory, and appear to represent extant predecessors of mammalian ADORs. We therefore designate the shark ADOR as the A0 receptor. We co-expressed A0 with CFTR in Xenopus laevis oocytes and characterized the coupling of A0 to the chloride channel. Two electrode voltage clamping was performed and current-voltage (I-V) responses were recorded to monitor CFTR status. Only in A0- and CFTR- co-injected oocytes did adenosine analogs produce a significant concentration-dependent activation of CFTR consistent with its electrophysiological signature. A pharmacological profile for A0 was obtained for ADOR agonists and antagonists that differed markedly from all mammalian ADOR subtypes (agonists: R-PIA > S-PIA > CGS21680 > CPA > 2ClADO > CV1808 = DPMA > NECA) and (antagonists: DPCPX > PD115199 > 8PT > CGC > CGS15943). Structures of human ADORs permitted a high-confidence homology model of the shark A0 core which revealed unique structural features of ancestral receptors. We conclude: (1) A0 is a novel and unique adenosine receptor ancestor by functional and structural criteria; (2) A0 likely activates CFTR in vivo and this receptor activates CFTR in oocytes indicating an evolutionary coupling between ADORs and chloride secretion; and (3) A0 appears to be a non-olfactory evolutionary ancestor of all four mammalian ADOR subtypes.

Primary role of volume expansion in stimulation of rectal gland function

1985 ◽  
Vol 248 (5) ◽  
pp. R638-R640 ◽  
Author(s):  
R. Solomon ◽  
M. Taylor ◽  
S. Sheth ◽  
P. Silva ◽  
F. H. Epstein
Keyword(s):  
Plasma Volume ◽  
Plasma Osmolality ◽  
Sodium Concentration ◽  
Chloride Secretion ◽  
Ringer Solution ◽  
Rectal Gland ◽  
Primary Role ◽  
Fourfold Increase ◽  
Gland Function

Chloride secretion by the in vivo rectal gland of the shark is stimulated by the intravascular infusion of salt solutions of varying osmolar and sodium concentration. In a cross-perfused and denervated rectal gland, the infusion of a small amount of a hypertonic salt solution raises plasma osmolality but does not increase plasma volume in the donor fish. Under these conditions, rectal gland chloride secretion is not stimulated. A subsequent infusion of isotonic shark Ringer solution increases plasma volume 50%, decreases plasma osmolality, and produces a fourfold increase in chloride secretion and a threefold decrease in vascular resistance within the gland. Both the vasodilatory and secretory responses also follow the infusion of a hypotonic shark Ringer solution. The data further support the hypothesis that the rectal gland of the shark is involved in the regulation of intravascular volume rather than in osmoregulation.

Atriopeptin stimulation of rectal gland function in Squalus acanthias

1985 ◽  
Vol 249 (3) ◽  
pp. R348-R354 ◽  
Author(s):  
R. Solomon ◽  
M. Taylor ◽  
D. Dorsey ◽  
P. Silva ◽  
F. H. Epstein
Keyword(s):  
Volume Expansion ◽  
Epithelial Transport ◽  
Extracellular Volume ◽  
Chloride Secretion ◽  
Hormonal Control ◽  
Rectal Gland ◽  
Gland Function ◽  
Stimulation Of

The rectal gland of the shark plays a significant role in the homeostasis of extracellular volume. Regulation of rectal gland function is under hormonal control, but the precise identity of the humoral mediator is unknown. Atriopeptin stimulates rectal gland chloride secretion in vivo. This stimulation of epithelial transport is accompanied by systemic and local hemodynamic effects. Atriopeptin also stimulates chloride secretion by the in vitro perfused rectal gland, an effect that is not accompanied by hemodynamic changes. Extracts of shark heart, but not muscle, brain, kidney, or intestine, contain a heat-stable trypsin-sensitive substance capable of in vitro stimulation of rectal gland chloride secretion. Electron micrographic analysis reveals multiple neurosecretory-like granules in atrial cardiocytes that are only rarely seen in ventricular cardiocytes. By using the in vitro perfused gland as a biologic assay, serum obtained after extracellular volume expansion reveals the presence of a rectal gland stimulatory factor that is not present in serum before expansion. These results are consistent with the hypothesis that atriopeptin is present in shark cardiocytes and is released during volume expansion. The atriopeptin stimulates rectal gland chloride secretion, providing a negative feedback mechanism for the regulation of extracellular volume.

In vivo effect of volume expansion on rectal gland function. II. Hemodynamic changes

1984 ◽  
Vol 246 (1) ◽  
pp. R67-R71
Author(s):  
R. J. Solomon ◽  
M. Taylor ◽  
R. Rosa ◽  
P. Silva ◽  
F. H. Epstein
Keyword(s):  
Blood Flow ◽  
Volume Expansion ◽  
Energy Requirement ◽  
Fluid Secretion ◽  
Chloride Secretion ◽  
Secretory Response ◽  
Rectal Gland ◽  
Oxygen Extraction Ratio ◽  
Humoral Factors

Intravascular volume expansion causes a 300% increase in the rate of fluid secretion from, and blood flow to, the in vivo rectal gland of the spiny dogfish Squalus acanthias. Similar increases are also observed in explanted rectal glands perfused through a catheter from the dorsal aorta of a volume-expanded dogfish. Stimulation of rectal gland secretion by volume expansion is not associated with a change in the ratio of chloride secreted to oxygen consumed by the rectal gland and the oxygen extraction ratio, suggesting that an increase in blood flow is necessary to support the increased rate of chloride secretion. Perfusion of the explanted gland with bumetanide (10(-4) M) completely inhibits the secretory response to volume expansion but does not prevent the increase in blood flow. Bumetanide also inhibits dibutyryl adenosine 3',5'-cyclic monophosphate- and theophylline-induced increases in chloride secretion but does not inhibit the hyperemic response. Somatostatin inhibits the secretory response of the explanted gland to volume expansion but does not prevent the increase in blood flow. Although an increase in blood flow is necessary to support the increased energy requirement of enhanced transport, the secretory response and the increase in blood flow appear to be independently regulated and mediated, at least in part, by humoral factors.

scholarly journals Mechanism and control of hyperosmotic NaCl-rich secretion by the rectal gland of Squalus acanthias

1983 ◽  
Vol 106 (1) ◽  
pp. 25-41 ◽  
Author(s):  
F. H. Epstein ◽  
J. S. Stoff ◽  
P. Silva
Keyword(s):  
Cyclic Amp ◽  
Chloride Secretion ◽  
Squalus Acanthias ◽  
Rectal Gland ◽  
Energetic Efficiency ◽  
Secondary Active Transport ◽  
Transport Pathway ◽  
Rectal Glands ◽  
And Control

Secretion of chloride from blood to lumen is accomplished in the rectal gland of elasmobranchs by a process of secondary active transport involving the co-transport of Cl- with Na+ across the basolateral membranes of rectal gland cells. Energy is provided by ATP via membrane Na-K-ATPase, which establishes an electrochemical gradient favouring Na+ influx into the cell. The involvement of K+ in the co-transport mechanism, so as to provide a ratio of 1 Na+:1 K+:2 Cl- entering the cell, would increase the energetic efficiency of the process, and is consistent with the Cl/O2 ration of 27–30 observed in secreting rectal glands. Secretion is stimulated by cyclic AMP (cAMP) and by vasoactive intestinal peptide (VIP) and adenosine, which activate adenylate cyclase. Activation of the gland in vivo probably occurs via VIP-secreting nerves as well as circulating agents; it is inhibited by somatostatin. Cyclic AMP probably stimulates chloride secretion by at least three mechanisms: (1) increasing chloride conductance across the luminal cell membrane, (2) enhancing the co-transport pathway for transmembrane movements of Na+, K+ and Cl- and (3) activating Na-K-ATPase.

In vivo effect of volume expansion on rectal gland function. I. Humoral factors

1984 ◽  
Vol 246 (1) ◽  
pp. R63-R66 ◽  
Author(s):  
R. Solomon ◽  
M. Taylor ◽  
J. S. Stoff ◽  
P. Silva ◽  
F. H. Epstein
Keyword(s):  
Volume Expansion ◽  
Chloride Secretion ◽  
Ringer Solution ◽  
Squalus Acanthias ◽  
Humoral Factor ◽  
Rectal Gland ◽  
Host Fish ◽  
Humoral Factors ◽  
Gland Function

The spiny dogfish Squalus acanthias responds to volume expansion by increasing the rate of chloride secretion by its rectal gland. The response is elicited by intravascular infusion of either isotonic shark Ringer solution, a 1 M hypertonic sodium chloride solution, or an isotonic hyponatremic solution containing equal volumes of shark Ringer solution and 10% mannitol. The effect of volume expansion was evoked in explanted glands connected to a host fish only by the arterial supply, indicating that the response is mediated by a humoral factor. The explanted gland responded to theophylline (2.5 X 10(-3) M) and adenosine 3',5'-cyclic monophosphate (5 X 10(-4) M) by increasing the rate of secretion of chloride by an amount similar to that induced by volume expansion of the perfusing fish. Theophylline at concentrations (10(-6) to 5 X 10(-5) M) that are known to inhibit the effect of adenosine in isolated perfused glands failed to inhibit the effect of volume expansion on explanted glands. Somatostatin (4.5 X 10(-6) M), which inhibits the effect of vasoactive intestinal peptide (VIP) in the isolated perfused gland, completely prevented the secretory response to volume expansion in explanted glands. Volume expansion is a major stimulus for chloride secretion by the rectal gland. The effect is mediated by a humoral factor that appears to be VIP.

Traceable Peptidic Ligands that Target Ghrelin Receptors

2020 ◽  
Vol 21 (10) ◽  
pp. 955-964 ◽  
Author(s):  
Mengjie Liu ◽  
John Wade ◽  
Mohammed Akhter Hossain
Keyword(s):  
In Vivo Imaging ◽  
Peptide Hormone ◽  
Structural Features ◽  
Pharmacological Properties ◽  
Imaging Studies ◽  
Cognate Receptor ◽  
Ghrelin Receptors ◽  
Biochemical Research

: Ghrelin is a 28-amino acid octanoylated peptide hormone that is implicated in many physiological and pathophysiological processes. Specific visualization of ghrelin and its cognate receptor using traceable ligands is crucial in elucidating the localization, functions, and expression pattern of the peptide’s signaling pathway. Here 12 representative radio- and fluorescently-labeled peptide-based ligands are reviewed for in vitro and in vivo imaging studies. In particular, the focus is on their structural features, pharmacological properties, and applications in further biochemical research.

Polyamines and Related Nitrogen Compounds in the Chemotherapy of Neglected Diseases Caused by Kinetoplastids

2018 ◽  
Vol 18 (5) ◽  
pp. 321-368 ◽  
Author(s):  
Juan A. Bisceglia ◽  
Maria C. Mollo ◽  
Nadia Gruber ◽  
Liliana R. Orelli
Keyword(s):  
Drug Targets ◽  
Redox Homeostasis ◽  
Cost Effective ◽  
Structural Features ◽  
Mammalian Host ◽  
Neglected Diseases ◽  
Nitrogen Compounds ◽  
Chemical Structures

Neglected diseases due to the parasitic protozoa Leishmania and Trypanosoma (kinetoplastids) affect millions of people worldwide, and the lack of suitable treatments has promoted an ongoing drug discovery effort to identify novel nontoxic and cost-effective chemotherapies. Polyamines are ubiquitous small organic molecules that play key roles in kinetoplastid parasites metabolism, redox homeostasis and in the normal progression of cell cycles, which differ from those found in the mammalian host. These features make polyamines attractive in terms of antiparasitic drug development. The present work provides a comprehensive insight on the use of polyamine derivatives and related nitrogen compounds in the chemotherapy of kinetoplastid diseases. The amount of literature on this subject is considerable, and a classification considering drug targets and chemical structures were made. Polyamines, aminoalcohols and basic heterocycles designed to target the relevant parasitic enzyme trypanothione reductase are discussed in the first section, followed by compounds directed to less common targets, like parasite SOD and the aminopurine P2 transporter. Finally, the third section comprises nitrogen compounds structurally derived from antimalaric agents. References on the chemical synthesis of the selected compounds are reported together with their in vivo and/or in vitro IC50 values, and structureactivity relationships within each group are analyzed. Some favourable structural features were identified from the SAR analyses comprising protonable sites, hydrophobic groups and optimum distances between them. The importance of certain pharmacophoric groups or amino acid residues in the bioactivity of polyamine derived compounds is also discussed.

scholarly journals Interaction of Lactoferrin with Unsaturated Fatty Acids: In Vitro and In Vivo Study of Human Lactoferrin/Oleic Acid Complex Cytotoxicity

Materials ◽  
2021 ◽  
Vol 14 (7) ◽  
pp. 1602
Author(s):  
Anna Elizarova ◽  
Alexey Sokolov ◽  
Valeria Kostevich ◽  
Ekaterina Kisseleva ◽  
Evgeny Zelenskiy ◽  
...  
Keyword(s):  
Oleic Acid ◽  
Structural Changes ◽  
Unsaturated Fatty Acids ◽  
Structural Features ◽  
Control Group ◽  
Acid Complex ◽  
Hepatoma 22A ◽  
Constitutive Parameters

As shown recently, oleic acid (OA) in complex with lactoferrin (LF) causes the death of cancer cells, but no mechanism(s) of that toxicity have been disclosed. In this study, constitutive parameters of the antitumor effect of LF/OA complex were explored. Complex LF/OA was prepared by titrating recombinant human LF with OA. Spectral analysis was used to assess possible structural changes of LF within its complex with OA. Structural features of apo-LF did not change within the complex LF:OA = 1:8, which was toxic for hepatoma 22a cells. Cytotoxicity of the complex LF:OA = 1:8 was tested in cultured hepatoma 22a cells and in fresh erythrocytes. Its anticancer activity was tested in mice carrying hepatoma 22a. In mice injected daily with LF-8OA, the same tumor grew significantly slower. In 20% of animals, the tumors completely resolved. LF alone was less efficient, i.e., the tumor growth index was 0.14 for LF-8OA and 0.63 for LF as compared with 1.0 in the control animals. The results of testing from 48 days after the tumor inoculation showed that the survival rate among LF-8OA-treated animals was 70%, contrary to 0% rate in the control group and among the LF-treated mice. Our data allow us to regard the complex of LF and OA as a promising tool for cancer treatment.

scholarly journals Rotavirus Infection Is Not Associated with Small Intestinal Fluid Secretion in the Adult Mouse

2006 ◽  
Vol 80 (22) ◽  
pp. 11355-11361 ◽  
Author(s):  
Shirin Kordasti ◽  
Claudia Istrate ◽  
Mahanez Banasaz ◽  
Martin Rottenberg ◽  
Henrik Sjövall ◽  
...  
Keyword(s):  
Fluid Secretion ◽  
Chloride Secretion ◽  
Potential Difference ◽  
Pathophysiological Mechanism ◽  
Rotavirus Infection ◽  
In Vivo Experiments ◽  
Adult Mice ◽  
Small Intestines

ABSTRACT In contrast to humans, adult but not infant small animals are resistant to rotavirus diarrhea. The pathophysiological mechanism behind this age-restricted diarrhea is currently unresolved, and this question was investigated by studying the secretory state of the small intestines of adult mice infected with rotavirus. Immunohistochemistry and histological examinations revealed that rotavirus (strain EDIM) infects all parts of the small intestines of adult mice, with significant numbers of infected cells in the ilea at 2 and 4 days postinfection. Furthermore, quantitative PCR revealed that 100-fold more viral RNA was produced in the ilea than in the jejuna or duodena of adult mice. In vitro perfusion experiments of the small intestine did not reveal any significant changes in net fluid secretion among mice infected for 3 days or 4 days or in those that were noninfected (37 ± 9 μl · h−1 · cm−1, 22 ± 13 μl · h−1 · cm−1, and 33 ± 6 μl · h−1 · cm−1, respectively) or in transmucosal potential difference (4.0 ± 0.3 mV versus 3.9 ± 0.4 mV), a marker for active chloride secretion, between control and rotavirus-infected mice. In vivo experiments also did not show any differences in potential difference between uninfected and infected small intestines. Furthermore, no significant differences in weight between infected and uninfected small intestines were found, nor were any differences in fecal output observed between infected and control mice. Altogether, these data suggest that rotavirus infection is not sufficient to stimulate chloride and water secretion from the small intestines of adult mice.

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