Mechanisms underlying glycosylation-mediated loss of ecotropic receptor function in murine MDTF cells and implications for receptor evolution

Abstract

A Mus dunni tail fibroblast (MDTF) cell line is highly resistant to infection by ecotropic Moloney murine leukemia virus (Mo-MLV). The cationic amino acid transporter type 1 (CAT1) paralogues of murine NIH 3T3 and MDTF cells (mCAT1 and dCAT1, respectively) contain two conserved N-linked glycosylation sites in the third extracellular loop (ECL3, the putative Mo-MLV binding site). Glycosylation of dCAT1 inhibits Mo-MLV infection, but that of mCAT1 does not. Compared with mCAT1, dCAT1 possesses an Ile-to-Val substitution at position 214 and a Gly insertion at position 236 in the ECL3. To determine the residues responsible for the loss of dCAT1 receptor function, mutants of mCAT1 were constructed. The mCAT1/insG receptor (with a Gly residue inserted at mCAT1 position 236) had greatly reduced Mo-MLV receptor function compared with mCAT1. Treatment of mCAT1/insG-expressing cells with tunicamycin, an N-linked glycosylation inhibitor, increased the transduction titre. In addition, the reduced susceptibility to Mo-MLV observed with mCAT1/insG-expressing cells correlated with impaired binding of Mo-MLV. These results show that a single amino acid insertion confers mCAT1 receptor properties on dCAT1 and provide an important insight into the co-evolution of virus-host interactions.

Infection of XC Cells by MLVs and Ebola Virus Is Endosome-Dependent but Acidification-Independent

“…The Eco-MLV vector bound to TE671/mCAT1 cells but not to TE671 cells (Fig. 9A), indicating that the binding is mCAT1-dependent, as previously reported in human NP2 cells [30]. Binding of the Eco-MLV vector to target cells was not suppressed by the inhibitors in XC (Fig.…”

“…The MLV vector binding assay was performed as reported previously [30], [47]. Target cells (1×10 6 ) were incubated with the MLV vector solution for 1 h at 4°C, and unbound vector particles were removed by two washes with PBS.…”

Susceptibility of muridae cell lines to ecotropic murine leukemia virus and the cationic amino acid transporter 1 viral receptor sequences: implications for evolution of the viral receptor

“…The longer insetion present in the hamster CAT1 compared to the rat protein may confer complete resistant of hamster cells to Eco-MLV infection. In addition, glycosylation of the Mus dunni CAT1 also inhibits Eco-MLV infection as a result of a one-amino acid insertion in the YGE virus-binding motif [4].…”

“…We have analyzed the viral receptors for ecotropic murine leukemia viruses (Eco-MLVs) in mouse (Mus musculus), rat (Ratus norvegicus), and Mus dunni cells as a model of receptor evolution that confers resistance to a virus infection [2][3][4].…”

A possible heterozygous advantage in muscular dystrophy

“…[10] In fact, glycosylation defects in fibroblasts are associated with resistance to murine leukaemia virus. [11] Those disorders that could be relevant in the present context include many haemorrhagic viral diseases in Central Africa, South America and India, which have been described in detail by Garrett [12] and Karlen. [13] These haemorrhagic diseases all present with internal bleeding, shock and the majority of patients succumb, though a few do survive.…”