The 22.5kDa spectrin-binding domain of ankyrinR binds spectrin with high affinity and changes the spectrin distribution in cells in vivo

2008 ◽  
Vol 60 (2) ◽  
pp. 157-164 ◽  
Author(s):  
Adam Kolondra ◽  
Michal Grzybek ◽  
Anna Chorzalska ◽  
Aleksander F. Sikorski
Keyword(s):  
Binding Domain ◽  
High Affinity ◽  
In Cells

scholarly journals Calculating metalation in cells reveals CobW acquires CoII for vitamin B12 biosynthesis upon binding nucleotide

2020 ◽  
Author(s):  
Tessa R. Young ◽  
Maria Alessandra Martini ◽  
Deenah Osman ◽  
Richard J. Morton ◽  
Evelyne Deery ◽  
...  
Keyword(s):  
Vitamin B12 ◽  
Vitamin B ◽  
Free Energies ◽  
High Affinity ◽  
High Affinity Site ◽  
Metal Sensors ◽  
Intracellular Milieu ◽  
In Cells

Protein metal-occupancy (metalation) in vivo has been elusive. Here we develop a metalation-calculator which accounts for inter-metal competition and changing metal-availabilities inside cells. The calculations are based on available free-energies of metals determined from the responses of metal sensors. We use the calculator to understand the function and mechanism of CobW, a predicted CoII-chaperone for vitamin B12. CobW is calculated to acquire negligible metal alone: But, upon binding nucleotide (GTP) and MgII, CobW assembles a high-affinity site that can obtain CoII or ZnII from the intracellular milieu. In idealised cells with sensors at the mid-points of their responses, competition within the cytosol enables CoII to outcompete ZnII for binding CobW. Thus, CoII is the cognate metal. However, after growth in different [CoII], CoII-occupancy ranges from 10 to 97% which matches CobW-dependent B12 synthesis. The calculator reveals how CobW acquires its metal and is made available for use with other proteins.

Phosphorylation of MAP4 affects microtubule properties and cell cycle progression

2001 ◽  
Vol 114 (15) ◽  
pp. 2879-2887 ◽  
Author(s):  
Winston Chang ◽  
Dorota Gruber ◽  
Sripriya Chari ◽  
Hidefumi Kitazawa ◽  
Yuko Hamazumi ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Cell Cycle Progression ◽  
Binding Domain ◽  
Proliferating Cells ◽  
Cycle Progression ◽  
Microtubule Binding ◽  
Microtubule Binding Domain ◽  
In Cells

In human cells, MAP4, a microtubule-associated protein ubiquitously expressed in proliferating cells, has been shown to undergo in vivo phosphorylation. Two phosphorylation sites, serines 696 and 787, lie within the proline-rich region of its microtubule-binding domain. To test the hypothesis that phosphorylation at these sites influences microtubule properties or cell cycle progression, we prepared stable cell lines that inducibly express versions of MAP4 in which phosphorylation of these two serines was prevented by their replacement with alanine, lysine, or glutamate residues (AA-, KK-, or EE-MAP4). All non-phosphorylatable mutant forms of MAP4 expressed in mouse Ltk- cells were localized to MT arrays that were unremarkable in appearance. Expression of non-phosphorylatable mutants of MAP4 did not affect cell doubling time; however, expression of some mutants altered progression into or through cell division. Interactions of mutant MAP4 with MTs were examined in vitro. KK mutant MAP4 bound MTs more avidly than its wild-type counterpart, WT-MAP4. In vivo MT polymer also differed among the mutants: MTs in cells expressing the KK- and AA-MAP4 forms were more resistant to nocodazole depolymerization than those in cells expressing EE- or WT-MAP4 forms. Our results demonstrate that phosphorylation alters MAP4 properties and suggest a raison d'être for phosphorylation of the MAP4 microtubule-binding domain during cell cycle progression.

scholarly journals 684 A low affinity bivalent mesothelin-binding MATCH4 multispecific T cell engager increases cytotoxic selectivity for high mesothelin expressing cells

2020 ◽  
Vol 8 (Suppl 3) ◽  
pp. A723-A723
Author(s):  
Bithi Chatterjee ◽  
Alexandre Simonin ◽  
Daniel Snell ◽  
Tea Gunde ◽  
Christian Hess ◽  
...  
Keyword(s):  
T Cell ◽  
Tumor Cell ◽  
Cancer Cells ◽  
Normal Tissue ◽  
Binding Domain ◽  
High Affinity ◽  
Tumor Associated Antigen ◽  
Low Levels

BackgroundThe effective treatment of solid tumors remains an unmet medical need. Several concepts exist to treat malignancies, including antibody-drug or -immunotoxin conjugates, immune checkpoint inhibition, CAR- T cells, as well as bispecific T cell engagers. CD3-based T cell engagers are highly potent therapeutic molecules with T cell cytotoxicity activities in the picomolar range. Alongside this highly potent anti-tumor activity is the risk of on-target off-tumor effects due to low levels of expression of the target antigen in normal tissue, as has been observed for the tumor-associated antigen mesothelin (MSLN).MethodsLow-affinity antibody fragments to the tumor-associated antigen MSLN were generated, and a multispecific MATCH4 molecule was constructed containing bivalent low-affinity MSLN binding domains, a CD3 binding domain, and a serum albumin-binding domain for half-life extension. This molecule was tested in a cytotoxicity assay using human PBMCs co-cultured with H226 or MeT-5A cells, which express high or low levels of MSLN, respectively. The MeT-5A line, derived from mesothelial cells in the pleural fluid of non-cancerous individuals, represents normal MSLN-expressing cells. Soluble MSLN was added to determine effects on cytotoxicity. In vivo xenograft mouse studies were conducted using a tumor cell/PBMC co-implantation model, followed by regular dosing with molecules of interest.ResultsHere we report the design and the promising preclinical activity of the MATCH4 molecule in vitro and in vivo. We demonstrate that the low-affinity bivalent MSLN T cell engager has increased in vitro potency in T cell activation and tumor cell killing, as compared to a high-affinity monovalent counterpart on high MSLN expressing cells. We also demonstrate that the activity on low MSLN expressing cells is reduced for the low-affinity bivalent compared to the high affinity monovalent molecule. Because soluble MSLN is shed from cancer cells into cancer patient serum, we also demonstrate that up to 500 ng/mL of soluble MSLN does not interfere with the cytotoxic activity of the low affinity bivalent T cell engager, compared to the effects of soluble MSLN on a high affinity monovalent T cell engager. Importantly, we demonstrate in vivo that the low-affinity bivalent molecule significantly inhibits tumor growth in a dose-dependent manner.ConclusionsCollectively, these data demonstrate anti-tumor efficacy by this novel multispecific low affinity bivalent T cell engager. These data indicate the potential of this molecule to increase the therapeutic window by reducing safety concerns on normal tissue where MSLN expression is low, and yet increase cytotoxicity to MSLN-expressing cancer cells.

scholarly journals A Novel Nanobody Targeting Middle East Respiratory Syndrome Coronavirus (MERS-CoV) Receptor-Binding Domain Has Potent Cross-Neutralizing Activity and Protective Efficacy against MERS-CoV

2018 ◽  
Vol 92 (18) ◽  
Author(s):  
Guangyu Zhao ◽  
Lei He ◽  
Shihui Sun ◽  
Hongjie Qiu ◽  
Wanbo Tai ◽  
...  
Keyword(s):  
Receptor Binding ◽  
Broad Spectrum ◽  
Half Life ◽  
Cost Effective ◽  
Binding Domain ◽  
Humanized Mice ◽  
Receptor Binding Domain ◽  
Neutralizing Activity ◽  
High Affinity

ABSTRACT The newly emerged Middle East respiratory syndrome coronavirus (MERS-CoV) continues to infect humans and camels, calling for efficient, cost-effective, and broad-spectrum strategies to control its spread. Nanobodies (Nbs) are single-domain antibodies derived from camelids and sharks and are potentially cost-effective antivirals with small size and great expression yield. In this study, we developed a novel neutralizing Nb (NbMS10) and its human-Fc-fused version (NbMS10-Fc), both of which target the MERS-CoV spike protein receptor-binding domain (RBD). We further tested their receptor-binding affinity, recognizing epitopes, cross-neutralizing activity, half-life, and efficacy against MERS-CoV infection. Both Nbs can be expressed in yeasts with high yield, bind to MERS-CoV RBD with high affinity, and block the binding of MERS-CoV RBD to the MERS-CoV receptor. The binding site of the Nbs on the RBD was mapped to be around residue Asp539, which is part of a conserved conformational epitope at the receptor-binding interface. NbMS10 and NbMS10-Fc maintained strong cross-neutralizing activity against divergent MERS-CoV strains isolated from humans and camels. Particularly, NbMS10-Fc had significantly extended half-life in vivo; a single-dose treatment of NbMS10-Fc exhibited high prophylactic and therapeutic efficacy by completely protecting humanized mice from lethal MERS-CoV challenge. Overall, this study proves the feasibility of producing cost-effective, potent, and broad-spectrum Nbs against MERS-CoV and has produced Nbs with great potentials as anti-MERS-CoV therapeutics. IMPORTANCE Therapeutic development is critical for preventing and treating continual MERS-CoV infections in humans and camels. Because of their small size, nanobodies (Nbs) have advantages as antiviral therapeutics (e.g., high expression yield and robustness for storage and transportation) and also potential limitations (e.g., low antigen-binding affinity and fast renal clearance). Here, we have developed novel Nbs that specifically target the receptor-binding domain (RBD) of MERS-CoV spike protein. They bind to a conserved site on MERS-CoV RBD with high affinity, blocking RBD's binding to MERS-CoV receptor. Through engineering a C-terminal human Fc tag, the in vivo half-life of the Nbs is significantly extended. Moreover, the Nbs can potently cross-neutralize the infections of diverse MERS-CoV strains isolated from humans and camels. The Fc-tagged Nb also completely protects humanized mice from lethal MERS-CoV challenge. Taken together, our study has discovered novel Nbs that hold promise as potent, cost-effective, and broad-spectrum anti-MERS-CoV therapeutic agents.

Effect of Some Metabolic Inhibitors on Vinblastine-Induced Ribosomal-Granular Material Complexes

1971 ◽  
Vol 29 ◽  
pp. 548-549
Author(s):  
Awtar Krishan ◽  
Dora Hsu
Keyword(s):  
Granular Material ◽  
Rna Synthesis ◽  
Culture Medium ◽  
Actinomycin D ◽  
Metabolic Inhibitors ◽  
Protein And Rna Synthesis ◽  
Apparent Reduction ◽  
Plant Alkaloids ◽  
In Cells

Cells exposed to antitumor plant alkaloids, vinblastine and vincristine sulfate have large proteinacious crystals and complexes of ribosomes, helical polyribosomes and electron-dense granular material (ribosomal complexes) in their cytoplasm, Binding of H3-colchicine by the in vivo crystals shows that they contain microtubular proteins. Association of ribosomal complexes with the crystals suggests that these structures may be interrelated.In the present study cultured human leukemic lymphoblasts (CCRF-CEM), were incubated with protein and RNA-synthesis inhibitors, p. fluorophenylalanine, puromycin, cycloheximide or actinomycin-D before the addition of crystal-inducing doses of vinblastine to the culture medium. None of these compounds could completely prevent the formation of the ribosomal complexes or the crystals. However, in cells pre-incubated with puromycin, cycloheximide, or actinomycin-D, a reduction in the number and size of the ribosomal complexes was seen. Large helical polyribosomes were absent in the ribosomal complexes of cells treated with puromycin, while in cells exposed to cycloheximide, there was an apparent reduction in the number of ribosomes associated with the ribosomal complexes (Fig. 2).

Effects of Heparin Oligosaccharides with High Affinity for Antithrombin III in Experimental Venous Thrombosis

1982 ◽  
Vol 47 (03) ◽  
pp. 244-248 ◽  
Author(s):  
D P Thomas ◽  
Rosemary E Merton ◽  
T W Barrowcliffe ◽  
L Thunberg ◽  
U Lindahl
Keyword(s):  
Antithrombin Iii ◽  
Specific Activity ◽  
High Specific Activity ◽  
Factor Xa ◽  
Blood Levels ◽  
Thrombin Time ◽  
High Affinity ◽  
Very High

SummaryThe in vitro and in vivo characteristics of two oligosaccharide heparin fragments have been compared to those of unfractionated mucosal heparin. A decasaccharide fragment had essentially no activity by APTT or calcium thrombin time assays in vitro, but possessed very high specific activity by anti-Factor Xa assays. When injected into rabbits at doses of up to 80 ¼g/kg, this fragment was relatively ineffective in impairing stasis thrombosis despite producing high blood levels by anti-Xa assays. A 16-18 monosaccharide fragment had even higher specific activity (almost 2000 iu/mg) by chromogenic substrate anti-Xa assay, with minimal activity by APTT. When injected in vivo, this fragment gave low blood levels by APTT, very high anti-Xa levels, and was more effective in preventing thrombosis than the decasaccharide fragment. However, in comparison with unfractionated heparin, the 16-18 monosaccharide fragment was only partially effective in preventing thrombosis, despite producing much higher blood levels by anti-Xa assays.It is concluded that the high-affinity binding of a heparin fragment to antithrombin III does not by itself impair venous thrombogenesis, and that the anti-Factor Xa activity of heparin is only a partial expression of its therapeutic potential.

Biologic Aspects of Expression of Stably Integrated Transgenes in Cells of the Skin In Vitro and In Vivo

1999 ◽  
Vol 111 (3) ◽  
pp. 198-205 ◽  
Author(s):  
Gerald G. Krueger ◽  
Jeffery R. Morgan ◽  
Marta J. Petersen
Keyword(s):  
In Cells

A High-Affinity Human Antibody That Targets Tumoral Blood Vessels

Blood ◽  
1999 ◽  
Vol 94 (1) ◽  
pp. 192-198 ◽  
Author(s):  
Lorenzo Tarli ◽  
Enrica Balza ◽  
Francesca Viti ◽  
Laura Borsi ◽  
Patrizia Castellani ◽  
...  
Keyword(s):  
Blood Vessels ◽  
Small Cell Lung Carcinoma ◽  
Antibody Fragment ◽  
Human Colon ◽  
Experimental Models ◽  
Human Antibody ◽  
Cell Lung Carcinoma ◽  
High Affinity ◽  
Biodistribution Studies

Angiogenesis is a characteristic feature of many aggressive tumors and of other relevant disorders. Molecules capable of specifically binding to new-forming blood vessels, but not to mature vessels, could be used as selective vehicles and would, therefore, open diagnostic and therapeutic opportunities. We have studied the distribution of the ED-B oncofetal domain of fibronectin, a marker of angiogenesis, in four different tumor animal models: the F9 murine teratocarcinoma, SKMEL-28 human melanoma, N592 human small cell lung carcinoma, and C51 human colon carcinoma. In all of these experimental models we observed accumulation of the fibronectin isoform containing the ED-B domain around neovascular structures when the tumors were in the exponentially growing phase, but not in the slow-growing phase. Then we performed biodistribution studies in mice bearing a subcutaneously implanted F9 murine teratocarcinoma, using a high-affinity human antibody fragment (L19) directed against the ED-B domain of fibronectin. Radiolabeled L19, but not an irrelevant anti-lysozyme antibody fragment (D1.3), efficiently localizes in the tumoral vessels. The maximal dose of L19 accumulated in the tumor was observed 3 hours after injection (8.2% injected dose per gram). By virtue of the rapid clearance of the antibody fragment from the circulation, tumor-to-blood ratios of 1.9, 3.7, and 11.8 were obtained at 3, 5, and 24 hours, respectively. The tumor-targeting performance of L19 was not dose-dependent in the 0.7 to 10 μg range of injected antibody. The integral of the radioactivity localized in tumoral vessels over 24 hours was greater than 70-fold higher than the integral of the radioactivity in blood over the same time period, normalized per gram of tissue or fluid. These findings quantitatively show that new-forming blood vessels can selectively be targeted in vivo using specific antibodies, and suggest that L19 may be of clinical utility for the immunoscintigraphic detection of angiogenesis in patients.

scholarly journals 1592U89, a novel carbocyclic nucleoside analog with potent, selective anti-human immunodeficiency virus activity.

1997 ◽  
Vol 41 (5) ◽  
pp. 1082-1093 ◽  
Author(s):  
S M Daluge ◽  
S S Good ◽  
M B Faletto ◽  
W H Miller ◽  
M H St Clair ◽  
...  
Keyword(s):  
Human Immunodeficiency Virus ◽  
Oral Bioavailability ◽  
Human Peripheral Blood ◽  
Cross Resistance ◽  
Immunodeficiency Virus ◽  
Carbocyclic Nucleoside ◽  
Hiv 1 ◽  
In Cells

1592U89, (-)-(1S,4R)-4-[2-amino-6-(cyclopropylamino)-9H-purin-9-yl]-2-cyclo pentene-1-methanol, is a carbocyclic nucleoside with a unique biological profile giving potent, selective anti-human immunodeficiency virus (HIV) activity. 1592U89 was selected after evaluation of a wide variety of analogs containing a cyclopentene substitution for the 2'-deoxyriboside of natural deoxynucleosides, optimizing in vitro anti-HIV potency, oral bioavailability, and central nervous system (CNS) penetration. 1592U89 was equivalent in potency to 3'-azido-3'-deoxythymidine (AZT) in human peripheral blood lymphocyte (PBL) cultures against clinical isolates of HIV type 1 (HIV-1) from antiretroviral drug-naive patients (average 50% inhibitory concentration [IC50], 0.26 microM for 1592U89 and 0.23 microM for AZT). 1592U89 showed minimal cross-resistance (approximately twofold) with AZT and other approved HIV reverse transcriptase (RT) inhibitors. 1592U89 was synergistic in combination with AZT, the nonnucleoside RT inhibitor nevirapine, and the protease inhibitor 141W94 in MT4 cells against HIV-1 (IIIB). 1592U89 was anabolized intracellularly to its 5'-monophosphate in CD4+ CEM cells and in PBLs, but the di- and triphosphates of 1592U89 were not detected. The only triphosphate found in cells incubated with 1592U89 was that of the guanine analog (-)-carbovir (CBV). However, the in vivo pharmacokinetic, distribution, and toxicological profiles of 1592U89 were distinct from and improved over those of CBV, probably because CBV itself was not appreciably formed from 1592U89 in cells or animals (<2%). The 5'-triphosphate of CBV was a potent, selective inhibitor of HIV-1 RT, with Ki values for DNA polymerases (alpha, beta, gamma, and epsilon which were 90-, 2,900-, 1,200-, and 1,900-fold greater, respectively, than for RT (Ki, 21 nM). 1592U89 was relatively nontoxic to human bone marrow progenitors erythroid burst-forming unit and granulocyte-macrophage CFU (IC50s, 110 microM) and human leukemic and liver tumor cell lines. 1592U89 had excellent oral bioavailability (105% in the rat) and penetrated the CNS (rat brain and monkey cerebrospinal fluid) as well as AZT. Having demonstrated an excellent preclinical profile, 1592U89 has progressed to clinical evaluation in HIV-infected patients.

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