The ecotropic murine leukemia virus (E-
MuLV) receptor expressed on Mus dunni tail fibroblast (MDTF) cells is a receptor for all E-MuLVs with the notable of Moloney murine leukemia virus (Mo-MuLV). Substitution of
isoleucine for
valine at position 214 in the third extracellular region (the putative E-MuLV binding site) of the MDTF receptor molecule allows this molecule to function as a Mo-
MuLV receptor (M.V. Eiden, K. Farrell, J. Warsowe, L. A. Mahan, and C. A. Wilson, J. Virol. 67:4056-4061, 1993). We have now determined that treating MDTF cells with
tunicamycin, an inhibitor of N-linked glycosylation, also renders them susceptible to Mo-MuLV
infection. Two potential N-linked glycosylation sites are present in the third extracellular regions of both the NIH 3T3 and MDTF ecotropic receptors. The glycosylation site at position 229 of the MDTF receptor
cDNA was eliminated by substituting a
threonine codon for the
asparagine codon. Mo-MuLV-resistant human HOS cells, expressing this form of the receptor, are susceptible to Mo-MuLV
infection. Thus, our studies suggest that without a
glycan moiety at position 229, the
valine residue at 214 is no longer restrictive for Mo-MuLV
infection. BHK-21 and CHO K1 hamster cells also express glycosylation-inactivated forms of the ecotropic receptor. Sequence analysis of these receptors together with our analysis of MDTF receptor function suggests that a single
asparagine-linked glycosylation site is responsible for glycosylation inactivation of these receptors.