Binding of the coronavirus mouse hepatitis virus A59 to its receptor expressed from a recombinant vaccinia virus depends on posttranslational processing of the receptor glycoprotein.
Recently, we showed that a murine member of the carcinoembryonic antigen family of glycoproteins serves as a cellular receptor (MHVR) for the coronavirus mouse hepatitis virus A59 (MHV-A59) (G. S. Dveksler, M. N. Pensiero, C. B. Cardellichio, R. K. Williams, G.-S. Jiang, K. V. Holmes, and C. W. Dieffenbach, J. Virol. 65:6881-6891, 1991; R. K. Williams, G.-S. Jiang, and K. V. Holmes, Proc. Natl. Acad. Sci. USA 88:5533-5536, 1991). To examine the role of posttranscriptional modification of MHVR on virus-receptor interactions, a vaccinia virus-based expression system was employed. Expression from the vaccinia virus recombinant (Vac-MHVR) in BHK-21 cells resulted in high levels of MHVR glycoprotein on the cell surface and made these cells susceptible to MHV-A59 infection. Nonglycosylated core MHVR proteins were made in Vac-MHVR-infected BHK-21 cells in the presence of tunicamycin by in vitro translation of MHVR mRNA in a rabbit reticulocyte cell-free system in the absence of microsomal membranes and by expression of an N-terminal deletion clone of MHVR lacking its signal peptide. These three nonglycosylated MHVR proteins were recognized by polyclonal antibody against affinity-purified receptor but did not bind antireceptor monoclonal antibody (MAb) CC1 or MHV-A59 virions. Partial glycosylation of MHVR, either expressed in Vac-MHVR-infected cells treated with monensin or synthesized by in vitro translation with microsomal membranes, restored both the MAb CC1- and the virus-binding activities of the MHVR glycoprotein. Deletion of 26 amino acids at the carboxyl terminus of MHVR resulted in a secreted protein which was able to bind MAb CC1 and MHV-A59. These results suggest that either a carbohydrate moiety is an element of the MHVR-binding site(s) for virus and MAb CC1 or a posttranslational membrane-associated process is required for functional conformation of the receptor glycoprotein.
Pensiero
M N
MN
Department of Pathology, Uniformed Services University of the Health Sciences, Bethesda, Maryland 20814-4799.
Dveksler
G S
GS
Cardellichio
C B
CB
Jiang
G S
GS
Elia
P E
PE
Dieffenbach
C W
CW
Holmes
K V
KV
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D004279:DNA, Viral; D015870:Gene Expression; D006023:Glycoproteins / Q000378:metabolism; D007150:Immunohistochemistry; D007700:Kinetics; D008969:Molecular Sequence Data; D006517:Murine hepatitis virus / Q000235:genetics / Q000378:metabolism*; D011499:Protein Processing, Post-Translational; D011991:Receptors, Virus / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D014616:Vaccinia virus / Q000235:genetics*
D004279:DNA, Viral; D006023:Glycoproteins; D011991:Receptors, Virus; D011994:Recombinant Proteins