scholarly journals Specific binding of 4-hydroxyestradiol to mouse uterine protein: evidence of a physiological role for 4-hydroxyestradiol

2005 ◽  
Vol 185 (2) ◽  
pp. 235-242 ◽  
Author(s):  
C S A Markides ◽  
J G Liehr
Keyword(s):  
Competitive Inhibition ◽  
Specific Binding ◽  
Physiological Role ◽  
Specific Protein ◽  
Selective Binding ◽  
First Order Kinetics ◽  
17Β Estradiol ◽  
The Difference ◽  
Old Mice

There are several indications of a possible physiological role for 4-hydroxyestradiol (4-OHE2) in hormone-responsive tissues. To examine a hormonal activity of 4-OHE2, we have studied the binding of 3H-labeled 4-OHE2 to mouse uterine cytosolic protein. In uteri of 3-week-old mice, total binding was 319.4 ± 13.9 fmol/mg protein. Binding in the presence of excess unlabeled 4-OHE2 dropped to 82.1 ± 1.7 fmol/mg protein, whereas 214.6 ± 9.4 fmol/mg protein bound while incubating in an excess of unlabeled 17β-estradiol (E2). The difference between the two binding values in the presence of excess steroid (132.5 ± 11.1 fmol/mg protein) is taken as selective binding of 4-OHE2 to a specific protein. In mice older than 4 weeks, the specific 4-OHE2 binding declined: 32.0 ± 4.0 fmol/mg protein at 8 weeks, 54.8 ± 6.3 fmol/mg protein at 12 weeks and 54.6 ± 5.2 fmol/mg protein at 9 months. Of other organs tested (liver, kidney, lung and whole brain) only lung showed significant selective binding of 4-OHE2. When E2-binding sites are blocked, binding follows first-order kinetics, yielding a dissociation constant (Kd) value of 11.8 ± 2.1 nM. The specific binding of 4-OHE2 was not inhibited by any other steroids or estrogen metabolites that were tested, except for 2-hydroxyestradiol (2-OHE2), which displayed competitive inhibition of 4-OHE2 binding with an inhibition constant (Ki) value of 98.2 ± 12.6 nM. These results lead us to conclude that 4-OHE2 binds to a specific binding protein, distinct and different from binding to estrogen receptors (ERα and ERβ). The physiological role of this binding remains to be elucidated.

On the Role of Transferrin in 67Ga Uptake by Tumor Cells

1988 ◽  
Vol 27 (04) ◽  
pp. 151-153
Author(s):  
P. Thouvenot ◽  
F. Brunotte ◽  
J. Robert ◽  
L. J. Anghileri
Keyword(s):  
Specific Binding ◽  
Subcellular Fractionation ◽  
Animal Blood ◽  
Tumor Bearing ◽  
Cell Structures ◽  
The Difference ◽  
Sarcoma Cells ◽  
In Vitro Uptake

In vitro uptake of 67Ga-citrate and 59Fe-citrate by DS sarcoma cells in the presence of tumor-bearing animal blood plasma showed a dramatic inhibition of both 67Ga and 59Fe uptakes: about ii/io of 67Ga and 1/5o of the 59Fe are taken up by the cells. Subcellular fractionation appears to indicate no specific binding to cell structures, and the difference of binding seems to be related to the transferrin chelation and transmembrane transport differences

Structure, Function, Involvement in Diseases and Targeting of 14-3-3 Proteins: An Update

2018 ◽  
Vol 25 (1) ◽  
pp. 5-21 ◽  
Author(s):  
Ylenia Cau ◽  
Daniela Valensin ◽  
Mattia Mori ◽  
Sara Draghi ◽  
Maurizio Botta
Keyword(s):  
Protein Interactions ◽  
Molecular Mechanisms ◽  
Physiological Role ◽  
Specific Protein ◽  
Protein Protein Interactions ◽  
Cellular Processes ◽  
Protein Partners ◽  
High Sequence Homology ◽  
Small Molecule Modulators

14-3-3 is a class of proteins able to interact with a multitude of targets by establishing protein-protein interactions (PPIs). They are usually found in all eukaryotes with a conserved secondary structure and high sequence homology among species. 14-3-3 proteins are involved in many physiological and pathological cellular processes either by triggering or interfering with the activity of specific protein partners. In the last years, the scientific community has collected many evidences on the role played by seven human 14-3-3 isoforms in cancer or neurodegenerative diseases. Indeed, these proteins regulate the molecular mechanisms associated to these diseases by interacting with (i) oncogenic and (ii) pro-apoptotic proteins and (iii) with proteins involved in Parkinson and Alzheimer diseases. The discovery of small molecule modulators of 14-3-3 PPIs could facilitate complete understanding of the physiological role of these proteins, and might offer valuable therapeutic approaches for these critical pathological states.

scholarly journals The Difference δ-Cells Make in Glucose Control

Physiology ◽  
2018 ◽  
Vol 33 (6) ◽  
pp. 403-411 ◽  
Author(s):  
Mark O. Huising ◽  
Talitha van der Meulen ◽  
Jessica L. Huang ◽  
Mohammad S. Pourhosseinzadeh ◽  
Glyn M. Noguchi
Keyword(s):  
Glucose Control ◽  
Feedback Loop ◽  
Physiological Role ◽  
Glucagon Secretion ◽  
Negative Feedback Loop ◽  
Β Cells ◽  
Insulin And Glucagon Secretion ◽  
The Difference ◽  
Delta Cells

The role of beta and α-cells to glucose control are established, but the physiological role of δ-cells is poorly understood. Delta-cells are ideally positioned within pancreatic islets to modulate insulin and glucagon secretion at their source. We review the evidence for a negative feedback loop between delta and β-cells that determines the blood glucose set point and suggest that local δ-cell-mediated feedback stabilizes glycemic control.

Immunomodulation by 17β-estradiol in bivalve hemocytes

2006 ◽  
Vol 291 (3) ◽  
pp. R664-R673 ◽  
Author(s):  
Laura Canesi ◽  
Caterina Ciacci ◽  
Lucia Cecilia Lorusso ◽  
Michele Betti ◽  
Tiziana Guarnieri ◽  
...  
Keyword(s):  
Kinase Inhibitors ◽  
Hydrolytic Enzymes ◽  
Physiological Role ◽  
Estrogen Receptor Α ◽  
Nitrite Accumulation ◽  
No Production ◽  
17Β Estradiol

In mammals, estrogens have dose- and cell-type-specific effects on immune cells and may act as pro- and anti-inflammatory stimuli, depending on the setting. In the bivalve mollusc Mytilus, the natural estrogen 17β-estradiol (E2) has been shown to affect neuroimmune functions. We have investigated the immunomodulatory role of E2 in Mytilus hemocytes, the cells responsible for the innate immune response. E2 at 5–25 nM rapidly stimulated phagocytosis and oxyradical production in vitro; higher concentrations of E2 inhibited phagocytosis. E2-induced oxidative burst was prevented by the nitric oxide (NO) synthase inhibitor NG-monomethyl-l-arginine and superoxide dismutase, indicating involvement of NO and O2−; NO production was confirmed by nitrite accumulation. The effects of E2 were prevented by the antiestrogen tamoxifen and by specific kinase inhibitors, indicating a receptor-mediated mechanism and involvement of p38 MAPK and PKC. E2 induced rapid and transient increases in the phosphorylation state of PKC, as well as of a aCREB-like (cAMP responsive element binding protein) transcription factor, as indicated by Western blot analysis with specific anti-phospho-antibodies. Localization of estrogen receptor-α- and -β-like proteins in hemocytes was investigated by immunofluorescence confocal microscopy. The effects of E2 on immune function were also investigated in vivo at 6 and 24 h in hemocytes of E2-injected mussels. E2 significantly affected hemocyte lysosomal membrane stability, phagocytosis, and extracellular release of hydrolytic enzymes: lower concentrations of E2 resulted in immunostimulation, and higher concentrations were inhibitory. Our data indicate that the physiological role of E2 in immunomodulation is conserved from invertebrates to mammals.

scholarly journals Activities and some properties of 5′-nucleotidase, adenosine kinase and adenosine deaminase in tissues from vertebrates and invertebrates in relation to the control of the concentration and the physiological role of adenosine

1978 ◽  
Vol 174 (3) ◽  
pp. 965-977 ◽  
Author(s):  
J R S Arch ◽  
E A Newsholme
Keyword(s):  
Adenosine Deaminase ◽  
Physiological Role ◽  
Adenosine Kinase ◽  
British Library ◽  
Adenosine Concentration ◽  
Effects Of Ph ◽  
The Difference ◽  
Low Activity

1. The maximal activities of 5′-nucleotidase, adenosine kinase and adenosine deaminase together with the Km values for their respective substrates were measured in muscle, nervous tissue and liver from a large range of animals to provide information on the mechanism of control of adenosine concentration in the tissues. 2. Detailed evidence that the methods used were optimal for the extraction and assay of these enzymes has been deposited as Supplementary Publication SUP 50088 (16pages) at the British Library Lending Division, Boston Spa, Wetherby, West Yorkshire LS23 7BQ, U.K.,from whom copies can be obtained on the terms indicated in Biochem. J. (1978), 169, 5. This evidence includes the effects of pH and temperature on the activities of the enzymes. 3. In many tissues, the activities of 5′-nucleotidase were considerably higher than the sum of the activities of adenosine kinase and deaminase, which suggests that the activity of the nucleotidase must be markedly inhibited in vivo so that adenosine does not accumulate. In the tissues in which comparison is possible, the Km of the nucleotidase is higher than the AMP content of the tissue, and since some of the latter may be bound within the cell, the low concentration of substrate may, in part, be responsible for a low activity in vivo. 4. In most tissues and animals investigated, the values of the Km of adenosine kinase for adenosine are between one and two orders of magnitude lower than those for the deaminase. It is suggested that 5′-nucleotidase and adenosine kinase are simultaneously active so that a substrate cycle between AMP and adenosine is produced: the difference in Km values between kinase and deaminase indicates that, via the cycle, small changes in activity of kinase or nucleotidase produce large changes in adenosine concentration. 5. The activities of adenosine kinase or deaminase from vertebrate muscles are inversely correlated with the activities of phosphorylase in these muscles. Since the magnitude of the latter activities are indicative of the anaerobic nature of muscles, this negative correlation supports the hypothesis that an important role of adenosine is the regulation of blood flow in the aerobic muscles.

scholarly journals Importance of experimental conditions in evaluating the malonyl-CoA sensitivity of liver carnitine acyltransferase. Studies with fed and starved rats

1981 ◽  
Vol 200 (2) ◽  
pp. 217-223 ◽  
Author(s):  
J D McGarry ◽  
D W Foster
Keyword(s):  
Fatty Acid ◽  
Fatty Acid Oxidation ◽  
Rat Liver ◽  
Competitive Inhibition ◽  
Physiological Role ◽  
Rat Liver Mitochondria ◽  
Acid Oxidation ◽  
Carnitine Acyltransferase ◽  
Malonyl Coa

The experiments reconfirm the powerful inhibitory effect of malonyl-CoA on carnitine acyltransferase I and fatty acid oxidation in rat liver mitochondria (Ki 1.5 microM). Sensitivity decreased with starvation (Ki after 18 h starvation 3.0 microM, and after 42 h 5.0 microM). Observations by Cook, Otto & Cornell [Biochem. J. (1980) 192, 955--958] and Ontko & Johns [Biochem. J. (1980) 192, 959--962] have cast doubt on the physiological role of malonyl-CoA in the regulation of hepatic fatty acid oxidation and ketogenesis. The high Ki values obtained in the cited studies are shown to be due to incubation conditions that cause substrate depletion, destruction of malonyl-CoA or generation of excessively high concentrations of unbound acyl-CoA (which offsets the competitive inhibition of malonyl-CoA towards carnitine acyltransferase I). The present results are entirely consistent with the postulated role of malonyl-CoA as the primary regulatory of fatty acid synthesis and oxidation in rat liver.

scholarly journals N6-methyladenosine (m6A) is an endogenous A3 adenosine receptor ligand

2020 ◽  
Author(s):  
Akiko Ogawa ◽  
Chisae Nagiri ◽  
Wataru Shihoya ◽  
Asuka Inoue ◽  
Kouki Kawakami ◽  
...  
Keyword(s):  
Specific Binding ◽  
Physiological Role ◽  
Modified Nucleosides ◽  
Epigenetic Mark ◽  
Type I ◽  
Rna Modifications ◽  
Adenosine A3 Receptor ◽  
A3 Adenosine Receptor ◽  
Shed Light

SUMMARYAbout 150 post-transcriptional RNA modifications have been identified in all kingdoms of life. During RNA catabolism, most modified nucleosides are resistant to degradation and are released into the extracellular space. In this study, we explored the physiological role of these extracellular modified nucleosides and found that N6-methyladenosine (m6A), widely known as an epigenetic mark in RNA, acts as a ligand for the adenosine A3 receptor, for which it has greater affinity than unmodified adenosine. Structural modeling defined the amino acids required for specific binding of m6A to the A3 receptor. m6A is dynamically released in response to cytotoxic stimuli and facilitates type I allergy. Our findings shed light on m6A as a signaling molecule with the ability to activate GPCRs, a previously unreported property of RNA modifications.

scholarly journals Pyruvate and ketone-body transport across the mitochondrial membrane. Exchange properties, pH-dependence and mechanism of the carrier

1978 ◽  
Vol 172 (3) ◽  
pp. 377-387 ◽  
Author(s):  
A P Halestrap
Keyword(s):  
Mitochondrial Membrane ◽  
Ketone Body ◽  
Ketone Bodies ◽  
Ph Dependence ◽  
Physiological Regulation ◽  
First Order Kinetics ◽  
Sh Group ◽  
Km Value ◽  
The Difference

The effects of exchangeable ions and pH on the efflux of pyruvate from preloaded mitochondria are reported. Efflux obeys first-order kinetics, and the stimulation of efflux by exchangeable ions such as acetoacetate and lactate obeys Michaelis–Menten kinetics. The apparent Km value +/- S.E. for acetoacetate was 0.56 +/- 0.14 mM (n = 5) and that for lactate 12.3 +/- 2.3 mM (n = 6). The Vmax. values +/- S.E. at 0 degrees C were 16.2 +/- 2.0 and 21.9 +/- 2.7 nmol/min per mg of protein. The exchange of a variety of other substituted monocarboxylates was also studied. Efflux was also stimulated by increasing the external pH. The data gave a pK for the transport process of 8.35 and a Vmax. of 3.31 +/- 0.14 nmol/min per mg. The similarity of the Vmax. values for various exchangeable ions but the difference of this from the Vmax. in the absence of exchangeable ions may indicate that transport of pyruvate occurs with H+ and not in exchange for an OH- ion. The inhibition of transport by alpha-cyano-4-hydroxycinnamate took several seconds to reach completion at 0 degrees C. It is proposed that inhibition occurs by binding to the substrate site and subsequent reaction with an -SH group on the inside of the membrane. The inhibitor can be displaced by substrates that can also enter the mitochondria independently of the carrier and so compete with the inhibitor for the substrate-binding site on the inside of the membrane. A mechanism for transport is proposed that invokes a transition state of pyruvate involving addition of an -SH group to the 2-carbon of pyruvate. Evidence is presented that suggests that ketone bodies may cross the mitochondrial membrane either on the carrier or by free diffusion. The physiological involvement of the carrier in ketone-body metabolism is discussed. The role of ketone bodies and pH in the physiological regulation of pyruvate transport is considered.

scholarly journals Comparative Study of Cyanobacterial and E. coli RNA Polymerases: Misincorporation, Abortive Transcription, and Dependence on Divalent Cations

2011 ◽  
Vol 2011 ◽  
pp. 1-11 ◽  
Author(s):  
Masahiko Imashimizu ◽  
Kan Tanaka ◽  
Nobuo Shimamoto
Keyword(s):  
Rna Polymerase ◽  
Divalent Cations ◽  
Physiological Role ◽  
Rna Polymerases ◽  
E Coli ◽  
Order Of Magnitude ◽  
Photosynthetic Machinery ◽  
The Difference ◽  
The Cost

If Mg2+ ion is replaced by Mn2+ ion, RNA polymerase tends to misincorporate noncognate nucleotide, which is thought to be one of the reasons for the toxicity of Mn2+ ion. Therefore, most cells have Mn2+ ion at low intracellular concentrations, but cyanobacteria need the ion at a millimolar concentration to maintain photosynthetic machinery. To analyse the mechanism for resistance against the abundant Mn2+ ion, we compared the properties of cyanobacterial and E. coli RNA polymerases. The cyanobacterial enzyme showed a lower level of abortive transcription and less misincorporation than the E. coli enzyme. Moreover, the cyanobacterial enzyme showed a slower rate of the whole elongation by an order of magnitude, paused more frequently, and cleaved its transcript faster in the absence of NTPs. In conclusion, cyanobacterial RNA polymerase maintains the fidelity of transcription against Mn2+ ion by deliberate incorporation of a nucleotide at the cost of the elongation rate. The cyanobacterial and the E. coli enzymes showed different sensitivities to Mg2+ ion, and the physiological role of the difference is also discussed.

Different modulation of aromatase activity in frog testis in vitro by ACE and ANG II

1999 ◽  
Vol 277 (5) ◽  
pp. R1261-R1267
Author(s):  
Antonino Miano ◽  
Anna Gobbetti ◽  
Massimo Zerani ◽  
Luana Quassinti ◽  
Ennio Maccari ◽  
...  
Keyword(s):  
Physiological Role ◽  
Rana Esculenta ◽  
Aromatase Activity ◽  
Ang Ii ◽  
Prostaglandin Production ◽  
Testicular Steroidogenesis ◽  
17Β Estradiol ◽  
Prereproductive Period

The aim of the present research was to study the role of angiotensin-converting enzyme (ACE) and ANG II in amphibian ( Rana esculenta) testicular steroidogenesis and prostaglandin production. Hormonal effects of ACE, ACE inhibitors, synthetic bullfrog ANG I, and [Val5]ANG II were determined in frog testis of prereproductive period. Production of 17β-estradiol, progesterone, androgens, and PGE2 and PGF2α was determined by incubating frog testes with ACE (2.5 mU/ml), captopril (0.1 mM), lisinopril (0.1 mM), [Val5]ANG II (1 μM), and synthetic bullfrog ANG I (1 μM). The analysis of the data showed an independent modulation of 17β-estradiol and androgen production by ACE and ANG II. The ACE pathway caused a decrease of 17β-estradiol production and an increase of androgen production in frog testes; on the other hand, the ANG II pathway increased 17β-estradiol production and decreased androgen production. The determination of testicular aromatase activity showed a positive regulation by ANG II and a negative regulation by ACE. As for prostaglandin production, only ANG II influenced PGF2α. These results suggest a new physiological role of ACE and ANG II in modulating steroidogenesis and prostaglandin production.

Sign in / Sign up

Export Citation Format

Share Document