Wessner D R, Shick P C, Lu J H, Cardellichio C B, Gagneten S E, Beauchemin N, Holmes K V, Dveksler G S
Department of Pathology, Uniformed Services University of the Health Sciences, Bethesda, Maryland 20814, USA.
J Virol. 1998 Mar;72(3):1941-8. doi: 10.1128/JVI.72.3.1941-1948.1998.
The primary cellular receptor for mouse hepatitis virus (MHV), a murine coronavirus, is MHVR (also referred to as Bgp1a or C-CAM), a transmembrane glycoprotein with four immunoglobulin-like domains in the murine biliary glycoprotein (Bgp) subfamily of the carcinoembryonic antigen (CEA) family. Other murine glycoproteins in the Bgp subfamily, including Bgp1b and Bgp2, also can serve as MHV receptors when transfected into MHV-resistant cells. Previous studies have shown that the 108-amino-acid N-terminal domain of MHVR is essential for virus receptor activity and is the binding site for monoclonal antibody (MAb) CC1, an antireceptor MAb that blocks MHV infection in vivo and in vitro. To further elucidate the regions of MHVR required for virus receptor activity and MAb CC1 binding, we constructed chimeras between MHVR and other members of the CEA family and tested them for MHV strain A59 (MHV-A59) receptor activity and MAb CC1 binding activity. In addition, we used site-directed mutagenesis to introduce selected amino acid changes into the N-terminal domains of MHVR and these chimeras and tested the abilities of these mutant glycoproteins to bind MAb CC1 and to function as MHV receptors. Several recombinant glycoproteins exhibited virus receptor activity but did not bind MAb CC1, indicating that the virus and MAb binding sites on the N-terminal domain of MHVR are not identical. Analysis of the recombinant glycoproteins showed that a short region of MHVR, between amino acids 34 and 52, is critical for MHV-A59 receptor activity. Additional regions of the N-terminal variable domain and the constant domains, however, greatly affected receptor activity. Thus, the molecular context in which the amino acids critical for MHV-A59 receptor activity are found profoundly influences the virus receptor activity of the glycoprotein.
小鼠肝炎病毒（MHV，一种鼠冠状病毒）的主要细胞受体是MHVR（也称为Bgp1a或C-CAM），它是一种跨膜糖蛋白，在癌胚抗原（CEA）家族的鼠胆汁糖蛋白（Bgp）亚家族中具有四个免疫球蛋白样结构域。Bgp亚家族中的其他鼠糖蛋白，包括Bgp1b和Bgp2，当转染到对MHV有抗性的细胞中时，也可以作为MHV受体。先前的研究表明，MHVR的108个氨基酸的N末端结构域对于病毒受体活性至关重要，并且是单克隆抗体（MAb）CC1的结合位点，MAb CC1是一种抗受体单克隆抗体，可在体内和体外阻断MHV感染。为了进一步阐明MHVR中病毒受体活性和MAb CC1结合所需的区域，我们构建了MHVR与CEA家族其他成员之间的嵌合体，并测试了它们对MHV A59株（MHV-A59）的受体活性和MAb CC1结合活性。此外，我们使用定点诱变将选定的氨基酸变化引入MHVR和这些嵌合体的N末端结构域，并测试这些突变糖蛋白结合MAb CC1和作为MHV受体发挥功能的能力。几种重组糖蛋白表现出病毒受体活性，但不结合MAb CC1，这表明MHVR N末端结构域上的病毒和单克隆抗体结合位点不相同。对重组糖蛋白的分析表明，MHVR中氨基酸34至52之间的一个短区域对于MHV-A59受体活性至关重要。然而，N末端可变结构域和恒定结构域的其他区域对受体活性有很大影响。因此，发现对MHV-A59受体活性至关重要的氨基酸的分子背景深刻影响了糖蛋白的病毒受体活性。
