J. Virol. doi:10.1128/JVI.01408-08
Copyright (c) 2008, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.
Efficient Subgroup C Avian Sarcoma And Leukosis Virus Receptor Activity Requires The IgV Domain Of The Tvc Receptor And Proper Display On The Cell Membrane
Audelia Munguia
and
Mark J. Federspiel*
Department of Molecular Medicine, Mayo Clinic, Rochester, MN 55905
* To whom correspondence should be addressed. Email:
federspiel.mark{at}mayo.edu.
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Abstract |
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We recently identified and cloned the receptor for ASLV(C) viruses, Tvc, a protein most closely related to mammalian butyrophilins, which are members of the immunoglobulin protein family. The extracellular domain of Tvc contains two immunoglobulin-like domains, IgV and IgC, which presumably each contain a disulfide bond important for native function of the protein. In this study, we have begun to identify the functional determinants of Tvc responsible for ASLV(C) receptor activity. We have found that the IgV domain of the Tvc receptor is responsible for interacting with the glycoprotein of ASLV(C). Additional experiments demonstrated that a domain was necessary as a spacer between the IgV and the membrane-spanning domain for efficient Tvc receptor activity, most likely to orient the IgV domain a proper distance from the cell membrane. The effects on ASLV(C) glycoprotein binding and infection efficiency were also studied by site-directed mutagenesis of the cysteine residues of Tvc as well as conserved amino acid residues of the IgV Tvc domain compared to other IgV domains. In this initial analysis of Tvc determinants important for interacting with ASLV(C) glycoproteins, at least two aromatic amino acid residues in the IgV domain of Tvc, Trp-48 and Tyr-105, were identified as critical for efficient ASLV(C) infection. Interestingly, one or more aromatic amino acid residues have been identified as critical determinants in the other ASLV(A-E) receptors for a proper interaction with ASLV glycoproteins. This suggests that the ASLV glycoproteins may share a common mechanism of receptor interaction with aromatic residue(s) on the receptor critical for the triggering conformational changes in SU that initiate the fusion process required for efficient virus infection.