Binding of transmissible gastroenteritis coronavirus to cell surface sialoglycoproteins.
The surface glycoprotein S of transmissible gastroenteritis virus (TGEV) has two binding activities. (i) Binding to porcine aminopeptidase N (pAPN) is essential for the initiation of infection. (ii) Binding to sialic acid residues on glycoproteins is dispensable for the infection of cultured cells but is required for enteropathogenicity. By comparing parental TGEV with mutant viruses deficient in the sialic acid binding activity, we determined the contributions of both binding activities to the attachment of TGEV to cultured cells. In the presence of a functional sialic acid binding activity, the amount of virus bound to two different porcine cell lines was increased sixfold compared to the binding of the mutant viruses. The attachment of parental virus was reduced to levels observed with the mutants when sialic acid containing inhibitors was present or when the cells were pretreated with neuraminidase. In virus overlay binding assays with immobilized cell surface proteins, the mutant virus only recognized pAPN. In addition, the parental virus bound to a high-molecular-mass sialoglycoprotein. The recognition of pAPN was sensitive to reducing conditions and was not dependent on sialic acid residues. On the other hand, binding to the sialic acid residues of the high-molecular-mass glycoprotein was observed regardless of whether the cellular proteins had been separated under reducing or nonreducing conditions. We propose that binding to a surface sialoglycoprotein is required for TGEV as a primary attachment site to initiate infection of intestinal cells. This concept is discussed in the context of other viruses that use two different receptors to infect cells.
Schwegmann-Wessels
Christel
C
Institut für Virologie, Tierärztliche Hochschule Hannover, 30559 Hannover, Germany.
Zimmer
Gert
G
Laude
Hubert
H
Enjuanes
Luis
L
Herrler
Georg
G
D000818:Animals; D018826:CD13 Antigens / Q000378:metabolism; D002460:Cell Line; D002462:Cell Membrane / Q000737:chemistry / Q000821:virology; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism; D011991:Receptors, Virus / Q000378:metabolism; D012795:Sialoglycoproteins / Q000737:chemistry / Q000378:metabolism*; D013552:Swine; D005760:Transmissible gastroenteritis virus / Q000235:genetics / Q000378:metabolism* / Q000472:pathogenicity
D008565:Membrane Proteins; D011991:Receptors, Virus; D012795:Sialoglycoproteins; D018826:CD13 Antigens