Zelus B D, Wessner D R, Williams R K, Pensiero M N, Phibbs F T, deSouza M, Dveksler G S, Holmes K V
Department of Microbiology, University of Colorado Health Sciences Center, Denver, Colorado 80262, USA.
J Virol. 1998 Sep;72(9):7237-44. doi: 10.1128/JVI.72.9.7237-7244.1998.
Mouse hepatitis virus receptor (MHVR) is a murine biliary glycoprotein (Bgp1(a)). Purified, soluble MHVR expressed from a recombinant vaccinia virus neutralized the infectivity of the A59 strain of mouse hepatitis virus (MHV-A59) in a concentration-dependent manner. Several anchored murine Bgps in addition to MHVR can also function as MHV-A59 receptors when expressed at high levels in nonmurine cells. To investigate the interactions of these alternative MHVR glycoproteins with MHV, we expressed and purified to apparent homogeneity the extracellular domains of several murine Bgps as soluble, six-histidine-tagged glycoproteins, using a baculovirus expression system. These include MHVR isoforms containing four or two extracellular domains and the corresponding Bgp1(b) glycoproteins from MHV-resistant SJL/J mice, as well as Bgp2 and truncation mutants of MHVR and Bgp1(b) comprised of the first two immunoglobulin-like domains. The soluble four-domain MHVR glycoprotein (sMHVR[1-4]) had fourfold more MHV-A59 neutralizing activity than the corresponding soluble Bgp1(b) (sBgp1(b)) glycoprotein and at least 1,000-fold more neutralizing activity than sBgp2. Although virus binds to the N-terminal domain (domain 1), soluble truncation mutants of MHVR and Bgp1(b) containing only domains 1 and 2 bound virus poorly and had 10- and 300-fold less MHV-A59 neutralizing activity than the corresponding four-domain glycoproteins. In contrast, the soluble MHVR glycoprotein containing domains 1 and 4 (sMHVR[1,4]) had as much neutralizing activity as the four-domain glycoprotein, sMHVR[1-4]. Thus, the virus neutralizing activity of MHVR domain 1 appears to be enhanced by domain 4. The sBgp1(b)[1-4] glycoprotein had 500-fold less neutralizing activity for MHV-JHM than for MHV-A59. Thus, MHV strains with differences in S-glycoprotein sequence, tissue tropism, and virulence can differ in the ability to utilize the various murine Bgps as receptors.
小鼠肝炎病毒受体（MHVR）是一种小鼠胆汁糖蛋白（Bgp1(a)）。从重组痘苗病毒表达的纯化可溶性MHVR以浓度依赖的方式中和了小鼠肝炎病毒A59株（MHV-A59）的感染性。除了MHVR外，几种锚定的小鼠Bgp在非小鼠细胞中高水平表达时也可作为MHV-A59受体发挥作用。为了研究这些替代MHVR糖蛋白与MHV的相互作用，我们使用杆状病毒表达系统表达并纯化了几种小鼠Bgp的细胞外结构域，使其达到表观均一性，成为可溶性的、带有六个组氨酸标签的糖蛋白。这些包括含有四个或两个细胞外结构域的MHVR异构体以及来自MHV抗性SJL/J小鼠的相应Bgp1(b)糖蛋白，还有Bgp2以及由前两个免疫球蛋白样结构域组成的MHVR和Bgp1(b)的截短突变体。可溶性四结构域MHVR糖蛋白（sMHVR[1-4]）对MHV-A59的中和活性比相应的可溶性Bgp1(b)（sBgp1(b)）糖蛋白高四倍，比sBgp2高至少1000倍。尽管病毒与N端结构域（结构域1）结合，但仅含有结构域1和2的MHVR和Bgp1(b)的可溶性截短突变体与病毒结合较差，对MHV-A59的中和活性比相应的四结构域糖蛋白低10倍和300倍。相反，含有结构域1和4的可溶性MHVR糖蛋白（sMHVR[1,4]）具有与四结构域糖蛋白sMHVR[1-4]相同的中和活性。因此，结构域4似乎增强了MHVR结构域1的病毒中和活性。sBgp1(b)[1-4]糖蛋白对MHV-JHM的中和活性比对MHV-A59低500倍。因此，具有S糖蛋白序列、组织嗜性和毒力差异的MHV毒株在利用各种小鼠Bgp作为受体的能力上可能存在差异。
