scholarly journals Expression and Characterization of a Soluble, Active Form of the Jaagsiekte Sheep Retrovirus Receptor, Hyal2

2005 ◽  
Vol 79 (1) ◽  
pp. 79-86 ◽  
Author(s):  
Vladimir Vigdorovich ◽  
Roland K. Strong ◽  
A. Dusty Miller
Keyword(s):  
Cell Surface ◽  
Expression System ◽  
Specific Interaction ◽  
Active Form ◽  
Soluble Form ◽  
Viral Inhibition ◽  
Virus Envelope ◽  
Critical Function ◽  
Jaagsiekte Sheep Retrovirus ◽  
Hyaluronidase Activity

ABSTRACT Retrovirus entry into cells is mediated by specific interactions between virus envelope glycoproteins and cell surface receptors. Many of these receptors contain multiple membrane-spanning regions, making their purification and study difficult. The jaagsiekte sheep retrovirus (JSRV) receptor, hyaluronidase 2 (Hyal2), is a glycosylphosphatidylinositol (GPI)-anchored molecule containing no peptide transmembrane regions, making it an attractive candidate for study of retrovirus entry. Further, the hyaluronidase activity reported for human Hyal2, combined with its broad expression pattern, may point to a critical function of Hyal2 in the turnover of hyaluronan, a major extracellular matrix component. Here we describe the properties of a soluble form of human Hyal2 (sHyal2) purified from a baculoviral expression system. sHyal2 is a 54-kDa monomer with weak hyaluronidase activity compared to that of the known hyaluronidase Spam1. In contrast to a previous report indicating that Hyal2 cleaved hyaluronan to a limit product of 20 kDa and was active only at acidic pH, we find that sHyal2 is capable of further degradation of hyaluronan and is active over a broad pH range, consistent with Hyal2 being active at the cell surface where it is normally localized. Interaction of sHyal2 with the JSRV envelope glycoprotein was analyzed by viral inhibition assays, showing >90% inhibition of transduction at 28 nM sHyal2, and by surface plasmon resonance, revealing a remarkably tight specific interaction with a dissociation constant (KD ) of 32 ± 1 pM. In contrast to results obtained with avian retroviruses, purified receptor was not capable of promoting transduction of cells that do not express the virus receptor.

scholarly journals Production and Characterization of a Soluble, Active Form of Tva, the Subgroup A Avian Sarcoma and Leukosis Virus Receptor

1999 ◽  
Vol 73 (4) ◽  
pp. 3054-3061 ◽  
Author(s):  
John W. Balliet ◽  
Joanne Berson ◽  
Celina M. D’Cruz ◽  
Julie Huang ◽  
Joanne Crane ◽  
...  
Keyword(s):  
Envelope Glycoprotein ◽  
Expression System ◽  
Active Form ◽  
Receptor Protein ◽  
Soluble Form ◽  
Stable Complex ◽  
Enzyme Linked Immunosorbent Assay ◽  
Apparent Dissociation Constant ◽  
Avian Sarcoma

ABSTRACT The receptor for the subgroup A avian sarcoma and leukosis viruses [ASLV(A)] is the cellular glycoprotein Tva. A soluble form of Tva, sTva, was produced and purified with a baculovirus expression system. Using this system, 7 to 10 mg of purified sTva per liter of cultured Sf9 cells was obtained. Characterization of the carbohydrate modification of sTva revealed that the three N glycosylation sites in sTva were differentially utilized; however, the O glycosylation common to Tva produced in mammalian and avian cells was not observed. Purified sTva demonstrates significant biological activity, specifically blocking infection of avian cells by ASLV(A) with a 90% inhibitory concentration of ∼25 pM. A quantitative enzyme-linked immunosorbent assay, developed to assess the binding of sTva to ASLV envelope glycoprotein, demonstrates that sTva has a high affinity for EnvA, with an apparent dissociation constant of approximately 0.3 nM. Once they are bound, a very stable complex is formed between EnvA and sTva, with an estimated complex half-life of 6 h. The soluble receptor protein described here represents a valuable tool for analysis of the receptor-envelope glycoprotein interaction and for structural analysis of Tva.

scholarly journals Efficient cell surface expression of class II MHC molecules in the absence of associated invariant chain.

1986 ◽  
Vol 164 (5) ◽  
pp. 1478-1489 ◽  
Author(s):  
J Miller ◽  
R N Germain
Keyword(s):  
Cell Surface ◽  
Intracellular Transport ◽  
Expression System ◽  
Specific Interaction ◽  
Surface Expression ◽  
Class Ii ◽  
Cell Surface Expression ◽  
Invariant Chain ◽  
3T3 Cells ◽  
Class Ii Alpha

The intracytoplasmic forms of class II (or Ia) major histocompatibility complex heterodimers are associated with a third glycoprotein, termed the invariant chain (Ii). This specific interaction has led to the view that Ii plays a necessary role in the assembly, intracellular transport, and/or membrane insertion of Ia molecules. To test this hypothesis directly, we have transfected complementary DNA clones that encode murine class II alpha and beta chains into cells that do not express any endogenous Ii messenger RNA (mRNA) (COS-7 and BALB/c 3T3 cells). After DNA-mediated gene transfer, significant cell surface expression of Ia was observed in transient expression assays using COS-7 cells and a stable expression system using BALB/c 3T3 cells. Furthermore, the total levels of class II alpha and beta mRNA were similar in Ii- cells (transfected BALB/c 3T3) and in Ii+ cells (B cell hybridoma) that expressed nearly identical amounts of surface Ia, suggesting that the efficiency of Ia expression was equivalent in the two cell types and, therefore, independent of Ii. These results indicate that the physiologic role for Ii is not simply to mediate membrane expression of Ia molecules, and that alternative hypotheses concerning the true function of this molecule need to be considered.

scholarly journals MMP-12, Secreted by Pro-Inflammatory Macrophages, Targets Endoglin in Human Macrophages and Endothelial Cells

2019 ◽  
Vol 20 (12) ◽  
pp. 3107 ◽  
Author(s):  
Mikel Aristorena ◽  
Eunate Gallardo-Vara ◽  
Matej Vicen ◽  
Mateo de Las Casas-Engel ◽  
Luisa Ojeda-Fernandez ◽  
...  
Keyword(s):  
Endothelial Cells ◽  
Cell Surface ◽  
Macrophage Polarization ◽  
Cell Surface Receptor ◽  
Soluble Form ◽  
Specific Marker ◽  
Good Resolution ◽  
Angiogenic Activity ◽  
Soluble Endoglin

Upon inflammation, monocyte-derived macrophages (MΦ) infiltrate blood vessels to regulate several processes involved in vascular pathophysiology. However, little is known about the mediators involved. Macrophage polarization is crucial for a fast and efficient initial response (GM-MΦ) and a good resolution (M-MΦ) of the inflammatory process. The functional activity of polarized MΦ is exerted mainly through their secretome, which can target other cell types, including endothelial cells. Endoglin (CD105) is a cell surface receptor expressed by endothelial cells and MΦ that is markedly upregulated in inflammation and critically involved in angiogenesis. In addition, a soluble form of endoglin with anti-angiogenic activity has been described in inflammation-associated pathologies. The aim of this work was to identify components of the MΦ secretome involved in the shedding of soluble endoglin. We find that the GM-MΦ secretome contains metalloprotease 12 (MMP-12), a GM-MΦ specific marker that may account for the anti-angiogenic activity of the GM-MΦ secretome. Cell surface endoglin is present in both GM-MΦ and M-MΦ, but soluble endoglin is only detected in GM-MΦ culture supernatants. Moreover, MMP-12 is responsible for the shedding of soluble endoglin in vitro and in vivo by targeting membrane-bound endoglin in both MΦ and endothelial cells. These data demonstrate a direct correlation between GM-MΦ polarization, MMP-12, and soluble endoglin expression and function. By targeting endothelial cells, MMP-12 may represent a novel mediator involved in vascular homeostasis.

scholarly journals Residues in domain III of the dengue virus envelope glycoprotein involved in cell-surface glycosaminoglycan binding

2012 ◽  
Vol 93 (1) ◽  
pp. 72-82 ◽  
Author(s):  
Daniel Watterson ◽  
Bostjan Kobe ◽  
Paul R. Young
Keyword(s):  
Cell Surface ◽  
Dengue Virus ◽  
Site Directed Mutagenesis ◽  
Cell Surface Receptor ◽  
Protein Fusion ◽  
Virus Envelope ◽  
Putative Receptor ◽  
E Protein ◽  
Surface Receptor ◽  
Domain Iii

The dengue virus (DENV) envelope (E) protein mediates virus entry into cells via interaction with a range of cell-surface receptor molecules. Cell-surface glycosaminoglycans (GAGs) have been shown to play an early role in this interaction, and charged oligosaccharides such as heparin bind to the E protein. We have examined this interaction using site-directed mutagenesis of a recombinant form of the putative receptor-binding domain III of the DENV-2E protein expressed as an MBP (maltose-binding protein)-fusion protein. Using an ELISA-based GAG-binding assay, cell-based binding analysis and antiviral-activity assays, we have identified two critical residues, K291 and K295, that are involved in GAG interactions. These studies have also demonstrated differential binding between mosquito and human cells.

scholarly journals CD28-independent, TRAF2-dependent Costimulation of Resting T Cells by 4-1BB Ligand

1998 ◽  
Vol 187 (11) ◽  
pp. 1849-1862 ◽  
Author(s):  
Katina Saoulli ◽  
Soo Young Lee ◽  
Jennifer L. Cannons ◽  
Wen Chen Yeh ◽  
Angela Santana ◽  
...  
Keyword(s):  
T Cells ◽  
T Cell ◽  
T Cell Activation ◽  
Cell Activation ◽  
Expression System ◽  
Baculovirus Expression System ◽  
Dominant Negative ◽  
Soluble Form ◽  
Tnf Receptor

4-1BB ligand (4-1BBL) is a member of the tumor necrosis factor (TNF) family expressed on activated antigen-presenting cells. Its receptor, 4-1BB, is a member of the TNF receptor family expressed on activated CD4 and CD8 T cells. We have produced a soluble form of 4-1BBL using the baculovirus expression system. When coimmobilized on plastic with anti-CD3, soluble 4-1BBL induces interleukin (IL)-2 production by resting CD28+ or CD28− T cells, indicating that 4-1BBL can function independently of other cell surface molecules, including CD28, in costimulation of resting T cell activation. At low concentrations of anti-CD3, 4-1BBL is inferior to anti-CD28 in T cell activation. However, when 4-1BB ligand is provided together with strong TCR signals, then 4-1BBL and anti-CD28 are equally potent in stimulation of IL-2 production by resting T cells. We find that TNF receptor–associated factor (TRAF)1 or TRAF2 associate with a glutathione S-transferase–4-1BB cytoplasmic domain fusion protein in vitro. In T cells, we find that association of TRAF1 and TRAF2 with 4-1BB requires 4-1BB cross-linking. In support of a functional role for TRAF2 in 4-1BB signaling, we find that resting T cells isolated from TRAF2-deficient mice or from mice expressing a dominant negative form of TRAF2 fail to augment IL-2 production in response to soluble 4-1BBL. Thus 4-1BB, via the TRAF2 molecule, can provide CD28-independent costimulatory signals to resting T cells.

Locomotory competence and laminin-specific cell surface binding sites are lost during myoblast differentiation

Development ◽  
1989 ◽  
Vol 105 (4) ◽  
pp. 795-802
Author(s):  
S.L. Goodman ◽  
R. Deutzmann ◽  
V. Nurcombe
Keyword(s):  
Cell Surface ◽  
Binding Sites ◽  
Radioligand Binding ◽  
Specific Interaction ◽  
Myoblast Differentiation ◽  
Specific Cell ◽  
Surface Binding ◽  
Cell Surface Binding ◽  
Locomotory Response ◽  
Specific Cell Surface

The specific interaction of embryonal cells with the extracellular matrix (ECM) is one of the principal forces influencing embryonal development (Hay, 1984; Trinkaus, 1984). We used a muscle satellite cell line (MM14dy) to determine the relationship between locomotory response to laminin and the expression of specific cell surface binding sites for it. Time lapse videomicroscopic analysis was used to study the locomotory response and radioligand binding assays and cell attachment assays were used to follow the expression levels of binding sites for laminin and its subfragments E8 and E1–4. We report here the novel finding that the ability of MM14dy to locomote over laminin diminishes and finally vanishes as the cells differentiate. The simultaneous drop in expression of binding sites for laminin is interpreted as being of potential significance during development and repair.

Cell surface heparan sulphate and adhesive property of sublines of rat ascites hepatoma AH7974

1988 ◽  
Vol 90 (4) ◽  
pp. 683-689 ◽  
Author(s):  
A. Kimura ◽  
T. Kawaguchi ◽  
T. Ono ◽  
A. Sakuma ◽  
Y. Yokoya ◽  
...  
Keyword(s):  
Cell Surface ◽  
Culture Medium ◽  
Heparan Sulphate ◽  
Soluble Form ◽  
Foetal Calf Serum ◽  
Serum Free Medium ◽  
Free Medium ◽  
Ascites Hepatoma ◽  
Serum Free ◽  
Rat Ascites Hepatoma

Two variants (74AD and 74FL) established from rat ascites hepatoma AH7974 were examined for the production of glycosaminoglycans in culture. There was no difference between the adhesive (74AD) and the floating (74FL) variants in quantity of glycosaminoglycans produced by their cultivation in minimum essential medium supplemented with 10% foetal calf serum. However, they were distinctly different in the distribution patterns of heparan sulphate. In 74FL, about 70% of total heparan sulphate was found in the culture medium in soluble form, whereas in 74AD, only 7% was found in the medium and the rest was in the cell-substratum complex. In a serum-free medium, 74AD cells grew without adhering to the substratum. After cultivation, more than 90% of total heparan sulphate was found in the cell-associated fractions and the rest in the substratum fractions. No heparan sulphate was detected in the culture medium. On the other hand, 74FL cells released heparan sulphate to the serum-free medium as much as to the serum-containing medium. The increase in amount of heparan sulphate in the culture medium of 74FL cells was supposed to be caused by failure of the cells to deposit heparan sulphate at the cell surface and not caused by increased production. Cell-substratum adhesion mechanisms involving cell surface heparan sulphate (heparan sulphate proteoglycan) and some serum intermediate(s) are discussed for 74AD cells.

A Recombinant Soluble Form of the Integrin IIbβ3 (GPIIb-IIIa) Assumes an Active, Ligand-Binding Conformation and Is Recognized by GPIIb-IIIa–Specific Monoclonal, Allo-, Auto-, and Drug-Dependent Platelet Antibodies

Blood ◽  
1998 ◽  
Vol 92 (6) ◽  
pp. 2053-2063 ◽  
Author(s):  
Julie A. Peterson ◽  
Gian P. Visentin ◽  
Peter J. Newman ◽  
Richard H. Aster
Keyword(s):  
Ligand Binding ◽  
Expression System ◽  
Site Directed Mutagenesis ◽  
High Yield ◽  
Soluble Form ◽  
Specific Antibodies ◽  
Binding Conformation ◽  
Active Ligand ◽  
Extracellular Region ◽  
Drug Dependent

Abstract The IIb-IIIa glycoprotein complex is a favored target for allo-, auto-, and drug-dependent antibodies associated with immune thrombocytopenia. A soluble, recombinant form of the GPIIb-IIIa heterodimer that could be produced in large quantities and maintained in solution without detergent could provide a useful experimental tool for the study of platelet-reactive antibodies, but previous attempts to produce such a construct have yielded only small quantities of the end product. Using a baculovirus expression system and the dual-promoter transfer vector P2Bac, we were able to express soluble GPIIb-IIIa complex (srGPIIb-IIIa) lacking cytoplasmic and transmembrane domains in quantities of about 1,000 μg/L, about 40 times greater than reported previously. The high yield achieved may be related to inclusion of the entire extracellular region of the GPIIb light chain in the construct. srGPIIb-IIIa reacts spontaneously with fibrinogen, and this interaction is totally inhibited by the peptide RGDS. Reactions of 24 GPIIb-IIIa–specific antibodies evaluated (12 monoclonal, 3 allo-specific, 3 auto-specific, and 6 drug-dependent) with srGPIIb-IIIa were indistinguishable from reactions with platelet GPIIb-IIIa. Thus, srGPIIb-IIIa spontaneously assumes an active, ligand-binding conformation and contains epitopes for all monoclonal and human antibodies tested to date. srGPIIb-IIIa can be produced in large quantities, can readily be modified by site-directed mutagenesis, and should facilitate identification of epitopes recognized by GPIIb-IIIa–specific antibodies, study of the mechanism(s) by which certain drugs promote antibody binding to GPIIb-IIIa in drug-induced thrombocytopenia and structure-function relationships of GPIIb-IIIa. © 1998 by The American Society of Hematology.

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