Rabies Virus Glycoprotein (RVG) Is a Trimeric Ligand for the N-terminal Cysteine-rich Domain of the Mammalian p75 Neurotrophin Receptor

Abstract

Rabies virus glycoprotein (RVG) is a trimeric and surface-exposed viral coat protein that has been shown to interact with the murine p75 neurotrophin receptor. We have investigated binding of RVG to p75 and describe several features that distinguish the p75-RVG interaction from conventional neurotrophin binding to p75. RVG binds mammalian but not avian p75 and does not bind to any of the Trk neurotrophin receptors. The mammalian p75 specificity of RVG binding may partly explain the phyletic specificity of rabies infection. Radioiodinated nerve growth factor (NGF) and RVG both bind to rat p75 but do not compete with each other's binding site. Although neurotrophins bind to the second and third cysteine-rich domains (CRD) of p75, RVG specifically interacts with high affinity (K d 30 -35 pM) with the first CRD (CRD1). Substitution of Gln 33 in p75-CRD1 by Glu completely abolishes RVG binding. Our data therefore firmly establish RVG as a trimeric high affinity ligand for a non-neurotrophin binding site on p75. Interestingly, the CRD1 in another TNF/NGF family receptor was recently shown to be involved in the binding of the herpes virus glycoprotein gD, suggesting that the CRD1 of TNF/NGF family members may be a widely used binding domain for viral glycoproteins. Rabies virus (RV)1 is a nonsegmented, negative strand RNA virus belonging to the genus Lyssavirus from the Rhabdoviridae (1). It is an enveloped virus with a single type I glycoprotein G (RVG) of 65 kDa inserted in its membrane. RVG is organized as a trimer and is responsible for the binding of the virus to the target cells and for the fusion between viral and cell membranes during the endocytosis of the virus. RV and other lyssaviruses are highly neurotropic and can cause fatal encephalomyelitis in mammals (2). Infection of both wild type and laboratory strains of RV is mainly targeted to neurons in vivo. In contrast in vitro infections with laboratory strains can target a range of cell types, and only wild type RV still shows specific neurotropism under these conditions. Specific interactions between RVG and neuronal cell surface molecules have been demonstrated (3), suggesting the existence of specific neuronal receptor(s). An expression cloning approach using soluble RVG to screen a neuroblastoma cell library led us to the identification of the murine p75 neurotrophin receptor as a candidate RVG receptor (4). Subsequent examination of six other lyssavirus genotypes revealed one additional viral glycoprotein (from European Bat lyssavirus 2) that can also bind p75 (5).The p75 neurotrophin receptor is highly conserved in vertebrates, and its expression is developmentally regulated (6, 7). During embryogenesis, p75 is present in neuronal as well as in non-neuronal cells, but in the adult its expression is essentially restricted to the peripheral and the central nervous system (8). p75 contains four cysteine-rich domains (CRD) in the N-terminal ectodomain and a type II death domain in its cytoplasmic C-terminal segment (8), both features characteristic of the...

The Rabies Virus Glycoprotein Receptor p75 NTR Is Not Essential for Rabies Virus Infection

“…Several strains of RV were used. Stocks of challenge virus standard (CVS) and mutants defective for p75 NTR binding derived from the CVS parental strain were prepared for infection as described previously (30). Briefly, viruses were propagated on BSR cells.…”

“…The virus pellet was then resuspended in a minimal volume, and aliquots were stored at Ϫ80°C. Viral titers were determined by plaque assay on BSR cells as described before (30).…”

“…Whereas neurotrophins bind to the second to fourth CRDs (2,21), we have previously shown that RVG binding occurs on the first CRD without competition for the neurotrophin binding site (30) Although RVG binds to p75 NTR , the role of this receptor for neuronal infection has been questioned, because RV infects and kills mutant mice lacking exon III of the p75 NTR gene (25). However, the significance of this finding is unclear, because these mice express the short splice variant of p75 NTR that contains CRD1 (53), which we have shown to be sufficient for RVG binding (30). Therefore, we revisited the question of the relative importance of p75 NTR for RV infection of primary neurons of the peripheral nervous system.…”

Detection of p75NTR Trimers: Implications for Receptor Stoichiometry and Activation

“…It has been proposed that p75 NTR homodimerizes by covalent and noncovalent interactions and that this assembly is required for intracellular adaptor recruitment and activation (Vilar et al, 2009b). However, a variety of molecular masses have been described for p75 NTR oligomers since its discovery (Puma et al, 1983;Grob et al, 1985;Langevin et al, 2002;Yaar et al, 2002;Sykes et al, 2012), leading to confusion in the field. Consequently, we decided to reevaluate p75 NTR oligomerization with a combination of biochemical techniques.…”

Perspectives in Diagnosis and Treatment of Rabies Viral Encephalitis: Insights from Pathogenesis

“…Cellular sialic acid, galactose, mannose and N-acetylglucosamine, and gangliosides, but not fucose, are shown to be involved in the binding of rabies virus to the host cells [38][39][40]. Variability in the receptors involved in viral entry could influence the IP, by altering the neuronal groups involved, and this mechanism needs to be evaluated as alternate therapeutic targets.…”