scholarly journals Kinetic analysis of transcellular passage of the cobalamin–transcobalamin complex in Caco-2 monolayers

2019 ◽  
Vol 30 (4) ◽  
pp. 467-477 ◽  
Author(s):  
Christian B. Juul ◽  
Sergey N. Fedosov ◽  
Ebba Nexo ◽  
Christian W. Heegaard
Keyword(s):  
Dissociation Constants ◽  
Cellular Transport ◽  
Dependent Manner ◽  
Animal Cells ◽  
Receptor Associated Protein ◽  
Ligand Free ◽  
Apparent Concentration ◽  
Ligand Interactions ◽  
Specific Receptors

We suggest a novel kinetic approach to quantifying receptor–ligand interactions via the cellular transport and/or accumulation of the ligand. The system of cobalamin (Cbl, vitamin B12) transport was used as a model, because Cbl is an obligatory cofactor, taken up by animal cells with the help of a transport protein and a membrane receptor. Bovine transcobalamin (bTC) stimulated the cellular accumulation and transcytosis of radioactive [57Co]Cbl in polarized monolayers of Caco-2 cells. The bovine protein was much more efficient than human TC. The transport was inhibited in a dose-dependent manner by the unlabeled bTC-Cbl complex, the ligand-free bTC, and the receptor-associated protein (RAP). This inhibition pattern implied the presence of a megalin-like receptor. Quantitative assessment of kinetic records by the suggested method revealed the apparent concentration of receptors in vitro (≈15 nM), as well as the dissociation constants of bTC–Cbl ( Kd = 13 nM) and RAP ( Kd = 1.3 nM). The data were used to estimate the effective luminal concentrations of TC-specific receptors in kidneys (3.8 µM) and intestine (50 nM), the tissues resembling polarized Caco-2 cells.

scholarly journals p180 Is Involved in the Interaction between the Endoplasmic Reticulum and Microtubules through a Novel Microtubule-binding and Bundling Domain

2007 ◽  
Vol 18 (10) ◽  
pp. 3741-3751 ◽  
Author(s):  
Kiyoko Ogawa-Goto ◽  
Keiko Tanaka ◽  
Tomonori Ueno ◽  
Keisuke Tanaka ◽  
Takeshi Kurata ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Mammalian Cells ◽  
Cultured Cells ◽  
Specific Interaction ◽  
Endoplasmic Reticulum Membrane ◽  
Dependent Manner ◽  
Small Interfering Rnas ◽  
Animal Cells ◽  
Microtubule Binding

p180 was originally reported as a ribosome-binding protein on the rough endoplasmic reticulum membrane, although its precise role in animal cells has not yet been elucidated. Here, we characterized a new function of human p180 as a microtubule-binding and -modulating protein. Overexpression of p180 in mammalian cells induced an elongated morphology and enhanced acetylated microtubules. Consistently, electron microscopic analysis clearly revealed microtubule bundles in p180-overexpressing cells. Targeted depletion of endogenous p180 by small interfering RNAs led to aberrant patterns of microtubules and endoplasmic reticulum in mammalian cells, suggesting a specific interaction between p180 and microtubules. In vitro sedimentation assays using recombinant polypeptides revealed that p180 bound to microtubules directly and possessed a novel microtubule-binding domain (designated MTB-1). MTB-1 consists of a predicted coiled-coil region and repeat domain, and strongly promoted bundle formation both in vitro and in vivo when expressed alone. Overexpression of p180 induced acetylated microtubules in cultured cells in an MTB-1-dependent manner. Thus, our data suggest that p180 mediates interactions between the endoplasmic reticulum and microtubules mainly through the novel microtubule-binding and -bundling domain MTB-1.

scholarly journals Aurora A activates D-TACC–Msps complexes exclusively at centrosomes to stabilize centrosomal microtubules

2005 ◽  
Vol 170 (7) ◽  
pp. 1039-1046 ◽  
Author(s):  
Teresa P. Barros ◽  
Kazuhisa Kinoshita ◽  
Anthony A. Hyman ◽  
Jordan W. Raff
Keyword(s):  
Drosophila Melanogaster ◽  
Coiled Coil ◽  
Mutant Form ◽  
Dependent Manner ◽  
Aurora A ◽  
Animal Cells

Centrosomes are the dominant sites of microtubule (MT) assembly during mitosis in animal cells, but it is unclear how this is achieved. Transforming acidic coiled coil (TACC) proteins stabilize MTs during mitosis by recruiting Minispindles (Msps)/XMAP215 proteins to centrosomes. TACC proteins can be phosphorylated in vitro by Aurora A kinases, but the significance of this remains unclear. We show that Drosophila melanogaster TACC (D-TACC) is phosphorylated on Ser863 exclusively at centrosomes during mitosis in an Aurora A–dependent manner. In embryos expressing only a mutant form of D-TACC that cannot be phosphorylated on Ser863 (GFP-S863L), spindle MTs are partially destabilized, whereas astral MTs are dramatically destabilized. GFP-S863L is concentrated at centrosomes and recruits Msps there but cannot associate with the minus ends of MTs. We propose that the centrosomal phosphorylation of D-TACC on Ser863 allows D-TACC–Msps complexes to stabilize the minus ends of centrosome-associated MTs. This may explain why centrosomes are such dominant sites of MT assembly during mitosis.

scholarly journals Serine threonine kinase receptor associated protein regulates early follicle development in the mouse ovary

Reproduction ◽  
2017 ◽  
Vol 153 (2) ◽  
pp. 221-231 ◽  
Author(s):  
Isam B Sharum ◽  
Sofia Granados-Aparici ◽  
Fiona C Warrander ◽  
Felicity P Tournant ◽  
Mark A Fenwick
Keyword(s):  
Molecular Mechanisms ◽  
Expression Profiles ◽  
Follicle Development ◽  
Dependent Manner ◽  
Mouse Ovary ◽  
Serine Threonine Kinase ◽  
Receptor Associated Protein ◽  
Smad Proteins ◽  
Different Populations

The molecular mechanisms involved in regulating the development of small, gonadotrophin-independent follicles are poorly understood; however, many studies have highlighted an essential role for TGFB ligands. Canonical TGFB signalling is dependent upon intracellular SMAD proteins that regulate transcription. STRAP has been identified in other tissues as an inhibitor of the TGFB–SMAD signalling pathway. Therefore, in this study we aimed to determine the expression and role of STRAP in the context of early follicle development. Using qPCR, Strap, Smad3 and Smad7 revealed similar expression profiles in immature ovaries from mice aged 4–16 days containing different populations of early growing follicles. STRAP and SMAD2/3 proteins co-localised in granulosa cells of small follicles using immunofluorescence. Using an established culture model, neonatal mouse ovary fragments with a high density of small non-growing follicles were used to examine the effects of Strap knockdown using siRNA and STRAP protein inhibition by immuno-neutralisation. Both interventions caused a reduction in the proportion of small, non-growing follicles and an increase in the proportion and size of growing follicles in comparison to untreated controls, suggesting inhibition of STRAP facilitates follicle activation. Recombinant STRAP protein had no effect on small, non-growing follicles, but increased the mean oocyte size of growing follicles in the neonatal ovary model and also promoted the growth of isolated preantral follicles in vitro. Overall findings indicate STRAP is expressed in the mouse ovary and is capable of regulating development of small follicles in a stage-dependent manner.

scholarly journals Cell-assembled extracellular matrix (CAM) sheet production: Translation from using human to large animal cells

2021 ◽  
Vol 12 ◽  
pp. 204173142097832
Author(s):  
Yoann Torres ◽  
Maude Gluais ◽  
Nicolas Da Silva ◽  
Sylvie Rey ◽  
Agathe Grémare ◽  
...  
Keyword(s):  
Extracellular Matrix ◽  
Species Differences ◽  
Human Fibroblasts ◽  
Growth Dynamics ◽  
Large Animal ◽  
Dependent Manner ◽  
Tissue Architecture ◽  
Animal Cells

We have created entirely biological tissue-engineered vascular grafts (TEVGs) using sheets of cell-assembled extracellular matrix (CAM) produced by human fibroblasts in vitro. A large animal TEVG would allow long-term pre-clinical studies in a clinically relevant setting (graft size and allogeneic setting). Therefore, canine, porcine, ovine, and human skin fibroblasts were compared for their ability to form CAM sheets. Serum sourcing greatly influenced CAM production in a species-dependent manner. Ovine cells produced the most homogenous and strongest animal CAM sheets but remained ≈3-fold weaker than human sheets despite variations of serum, ascorbate, insulin, or growth factor supplementations. Key differences in cell growth dynamics, tissue development, and tissue architecture and composition were observed between human and ovine. This study demonstrates critical species-to-species differences in fibroblast behavior and how they pose a challenge when attempting to substitute animal cells for human cells during the development of tissue-engineered constructs that require long-term cultures.

scholarly journals Abstract P-11: Microscale Thermophoresis of Mycobacterial Cytochrome P450 with Azole Drugs

2021 ◽  
Vol 11 (Suppl_1) ◽  
pp. S15-S16
Author(s):  
Ivan Kapranov ◽  
S Bukhdruker ◽  
M Karpova ◽  
Yulia Zagryadskaya ◽  
Ivan Okhrimenko ◽  
...  
Keyword(s):  
Cytochrome P450 ◽  
Unsaturated Fatty Acids ◽  
Dissociation Constants ◽  
Cytochromes P450 ◽  
Microscale Thermophoresis ◽  
Protein Ligand Interactions ◽  
Ligand Interactions ◽  
Cytochrome P450 Family ◽  
The Hill

Background: Cytochrome P450 family members are found in most organisms where they are involved in the metabolism and synthesis of steroids, bile acids, unsaturated fatty acids, phenolic metabolites as well as exogenic chemicals. Drugs targeting cytochrome P450 have been shown to inhibit the growth of Mycobacterium tuberculosis, the causative agent of one of the deadliest diseases – tuberculosis. Recently, we showed that CYP124, CYP125, and CYP142 can bind and metabolize a panel of human immunoactive oxysterols in vitro (Varaksa et al., 2021) and one of them (CYP124) can metabolize antituberculosis drugs (Bukhdruker et al., 2020). Thus, inhibition of cytochrome P450 is a promising strategy for the development of new anti-tubercular drugs. The existing methods used to assess protein-ligand interactions for cytochromes P450 (spectral titration and Surface Plasmon Resonance) have a number of limitations. In this regard, we used an alternative approach for this purposes – microscale thermophoresis (MST) which was not previously used for proteins of the cytochrome P450 superfamily Methods: Here we show that MST can be used to determine the micromolar-range dissociation constants (Kd) of membrane-associated mycobacterial cytochrome CYP124 with small-molecule azole drugs. CYP124 was fluorescently labeled with Cy3-NHS and MST curves were collected at Monolith NT.115 instrument (blue/green channel, NanoTemper Technologies) in presence of various concentrations of azole compounds: econazole, ketoconazole, itraconazole, and miconazole. The experimental results were approximated by the second-order bimolecular binding equation as well as by the Hill-Langmuir equation. Results: Therefore, MST is a valuable method for the assessment of cytochrome P450 binding to their ligands for cases when traditional approaches are not applicable. The binding regime of CYP124 with azole derivatives was characterized by the structure of the CYP124 complex with carbethoxyhexyl imidazole solved with ~1Å resolution.

CarR, a MarR-family regulator from Corynebacterium glutamicum, modulated antibiotic and aromatic compound resistance

2019 ◽  
Vol 476 (21) ◽  
pp. 3141-3159 ◽  
Author(s):  
Meiru Si ◽  
Can Chen ◽  
Zengfan Wei ◽  
Zhijin Gong ◽  
GuiZhi Li ◽  
...  
Keyword(s):  
Stress Response ◽  
Ligand Binding ◽  
Corynebacterium Glutamicum ◽  
Conformational Changes ◽  
Cysteine Oxidation ◽  
Transcriptional Regulatory ◽  
Ligand Free ◽  
Redox Sensing

Abstract MarR (multiple antibiotic resistance regulator) proteins are a family of transcriptional regulators that is prevalent in Corynebacterium glutamicum. Understanding the physiological and biochemical function of MarR homologs in C. glutamicum has focused on cysteine oxidation-based redox-sensing and substrate metabolism-involving regulators. In this study, we characterized the stress-related ligand-binding functions of the C. glutamicum MarR-type regulator CarR (C. glutamicum antibiotic-responding regulator). We demonstrate that CarR negatively regulates the expression of the carR (ncgl2886)–uspA (ncgl2887) operon and the adjacent, oppositely oriented gene ncgl2885, encoding the hypothetical deacylase DecE. We also show that CarR directly activates transcription of the ncgl2882–ncgl2884 operon, encoding the peptidoglycan synthesis operon (PSO) located upstream of carR in the opposite orientation. The addition of stress-associated ligands such as penicillin and streptomycin induced carR, uspA, decE, and PSO expression in vivo, as well as attenuated binding of CarR to operator DNA in vitro. Importantly, stress response-induced up-regulation of carR, uspA, and PSO gene expression correlated with cell resistance to β-lactam antibiotics and aromatic compounds. Six highly conserved residues in CarR were found to strongly influence its ligand binding and transcriptional regulatory properties. Collectively, the results indicate that the ligand binding of CarR induces its dissociation from the carR–uspA promoter to derepress carR and uspA transcription. Ligand-free CarR also activates PSO expression, which in turn contributes to C. glutamicum stress resistance. The outcomes indicate that the stress response mechanism of CarR in C. glutamicum occurs via ligand-induced conformational changes to the protein, not via cysteine oxidation-based thiol modifications.

Chlorobutanol, a Preservative of Desmopressin, Inhibits Human Platelet Aggregation and Release In Vitro

1990 ◽  
Vol 64 (03) ◽  
pp. 473-477 ◽  
Author(s):  
Shih-Luen Chen ◽  
Wu-Chang Yang ◽  
Tung-Po Huang ◽  
Shiang Wann ◽  
Che-ming Teng
Keyword(s):  
Arachidonic Acid ◽  
Platelet Aggregation ◽  
Atp Release ◽  
Free Calcium ◽  
Dependent Manner ◽  
Antiplatelet Effect ◽  
Human Platelet Aggregation ◽  
Acid Pathway ◽  
Arachidonic Acid Pathway

SummaryTherapeutic preparations of desmopressin for parenteral use contain the preservative chlorobutanol (5 mg/ml). We show here that chlorobutanol is a potent inhibitor of platelet aggregation and release. It exhibited a significant inhibitory activity toward several aggregation inducers in a concentration- and time-dependent manner. Thromboxane B2 formation, ATP release, and elevation of cytosolic free calcium caused by collagen, ADP, epinephrine, arachidonic acid and thrombin respectively were markedly inhibited by chlorobutanol. Chlorobutanol had no effect on elastase- treated platelets and its antiplatelet effect could be reversed. It is concluded that the antiplatelet effect of chlorobutanol is mainly due to its inhibition on the arachidonic acid pathway but it is unlikely to have a nonspecitic toxic effect. This antiplatelet effect of chlorobutanol suggests that desmopressin, when administered for improving hemostasis, should not contain chlorobutanol as a preservative.

Oxygenation of 18-hydroxycorticosterone as the final reaction for aldosterone biosynthesis

1984 ◽  
Vol 107 (3) ◽  
pp. 395-400 ◽  
Author(s):  
Itaru Kojima ◽  
Etsuro Ogata ◽  
Hiroshi Inano ◽  
Bun-ichi Tamaoki
Keyword(s):  
Carbon Monoxide ◽  
Hydroxysteroid Dehydrogenase ◽  
Dependent Manner ◽  
In Vitro Production ◽  
Mitochondrial Preparation ◽  
Final Reaction ◽  
Vitro Production ◽  
Dose Dependent ◽  
Cytochrome P 450

Abstract. Incubation of 18-hydroxycorticosterone with the sonicated mitochondrial preparation of bovine adrenal glomerulosa tissue leads to the production of aldosterone, as measured by radioimmunoassay. The in vitro production of aldosterone from 18-hydroxycorticosterone requires both molecular oxygen and NADPH, and is inhibited by carbon monoxide. Cytochrome P-450 inhibitors such as metyrapone, SU 8000. SU 10603, SKF 525A, amphenone B and spironolactone decrease the biosynthesis of aldosterone from 18-hydroxycorticosterone. These results support the conclusion that the final reaction in aldosterone synthesis from 18-hydroxycorticosterone is catalyzed by an oxygenase, but not by 18-hydroxysteroid dehydrogenase. By the same preparation, the production of [3H]aldosterone but not [3H]18-hydroxycorticosterone from [1,2-3H ]corticosterone is decreased in a dose-dependent manner by addition of non-radioactive 18-hydroxycorticosterone.

Sign in / Sign up

Export Citation Format

Share Document