The receptor for the subgroup A avian leukosis-sarcoma viruses binds to subgroup A but not to subgroup C envelope glycoprotein

Abstract

Susceptibility to infection by subgroup A ALSV is conferred on cells upon transfection with cDNAs encoding tva. The hypothesis that tva encodes a specific receptor for subgroup A ALSV predicts that the Tva protein should bind to subgroup A, but not to subgroup C, envelope glycoprotein. In this study, we examined this prediction by using several biochemical assays. We established stable NIH 3T3 cell lines expressing either Tva, the subgroup A envelope glycoprotein (Env-A), or the subgroup C envelope glycoprotein (Env-C) and used them in conjunction with soluble forms of these molecules to demonstrate specific binding. When cell lysates containing Tva were mixed with lysates of either Env-A or Env-C, an immunoprecipitable complex formed between Tva and Env-A but not between Tva and Env-C. A soluble, oligomeric form of Env-A, not Env-C, binds to cells expressing Tva. Reciprocally, a secreted form of Tva can bind to cells expressing Env-A but not to cells expressing Env-C. A specific and stable complex formed between soluble Env-A and secreted Tva as demonstrated by sucrose density gradient centrifugation. Thus, by three kinds of assays, Tva appears to bind specifically to Env-A, which is consistent with genetic evidence that

Identification of Key Residues in Subgroup A Avian Leukosis Virus Envelope Determining Receptor Binding Affinity and Infectivity of Cells Expressing Chicken or Quail Tva Receptor

“…Soluble forms of the Tva receptor specifically block ALV(A) infection (5,38,72) and induce conformational changes in the envelope glycoproteins similar to events thought to be required for membrane fusion (19,31,32,34). In this study, the binding affinities of both chicken and quail sTva-mIgG produced in chicken cells, for ALV(A) envelope glycoproteins expressed on the surface of infected chicken cells, were estimated to have apparent K d values of 0.51 and 0.31 nM, respectively ( Table 2).…”

“…at 39°C and 5% CO 2 . The generation of the 3T3pg950 cell line, an NIH 3T3 cell line stably transfected with the quail pg950 Tva receptor cDNA, was previously described (31). The 3T3pg950 cells were grown in Dulbecco's modified Eagle's medium supplemented with 10% calf serum (CS) (GIBCO/BRL), 250 g of G418 per ml (GIBCO/BRL), 100 U of penicillin per ml, and 100 g of streptomycin per ml at 37°C and 5% CO 2 .…”

“…Soluble forms of viral receptors are effective reagents for characterizing viral envelope glycoprotein-receptor interactions. Soluble forms of the quail Tva receptor are capable of inducing conformational changes in subgroup A envelope glycoproteins that may be similar to receptor-triggered events required for membrane fusion (19,31,32,34). A soluble receptor chimera consisting of the leader and first 6 amino acids of the quail Tva receptor fused to the extracellular region of the chicken Tva receptor efficiently and specifically blocked infection of ALV(A) (16).…”

Expanded Tropism and Altered Activation of a Retroviral Glycoprotein Resistant to an Entry Inhibitor Peptide

“…Plasmids and proteins. The ASLV-A envelope expression vector, pCB6-EnvA, has been described previously (18). Notable mutations identified by sequencing (see below) were subcloned from their TOPO vector into pCB6-EnvA using strategies particular to each mutation.…”

Inhibitors of SARS-CoV entry – Identification using an internally-controlled dual envelope pseudovirion assay

“…Pseudotyped viruses were generated from two plasmids, one encoding the envelope and the other encoding the viral backbone with a reporter gene. Plasmids encoding SARS-CoV spike glycoprotein, Ebola GP, vesicular stomatitis virus (VSV)-G, chikungunya virus (CHIKV), as well as MLV envelope, have been described (Gilbert et al, 1994;Salvador et al, 2009;Simmons et al, 2002Simmons et al, , 2004Simmons et al, , 2005. The Lassa GP gene was synthesized based on the sequence of strain GA391, and subcloned into pcDNA3.1.…”