Regulation of expression of the reovirus receptor on differentiated HL60 cells

Measurement of bluetongue virus binding to a mammalian cell surface receptor by an in situ immune fluorescent staining technique

A quantifiable in situ immune fluorescent assay (IFA) was developed to measure bluetongue virus (BTV) binding to mammalian cells. The utility of the assay was demonstrated with both Chinese hamster ovary (CHO) and bovine pulmonary artery endothelial (CPAE) cells. Since heparin sulfate (HS) has been shown to function as a receptor for a number of viruses, its role as a receptor for BTV was evaluated with the in situ IFA. Binding of BTV to both CHO and CPAE cells was inhibited in a dose dependent manner by HS. In addition, HS deficient CHO cells showed greatly diminished binding of BTV when compared to the parental cell line. The IFA protocol will find application, as a non-isotopic, quantifiable technique, to study virus-cell receptor interactions. Information gained from such studies will expand our understanding of the early steps in virus replication.

Identification of bovine viral diarrhea virus receptor in different cell types

Anti-idiotypic antibodies (anti-ids) have been used successfully in studies on bovine viral diarrhea virus (BVDV) receptor(s) in our laboratory. The anti-ids specifically bound to cultured cells and identified a 50 kDa cellular membrane protein, which is thought to be a specific receptor for BVDV. In this study, flow cytometric analyses demonstrated that the anti-ids also specifically bound to different cell types, namely MDBK, EBK, BT, PK15, MA1O4, and Vero. Experiments on virus attachment and replication showed that BVDV adsorbed to all cells and replicated in them except monkey kidney cells MA 104 and Vero (non-permissive). Results from plaque reduction assays indicated that cellular membrane proteins from all cell lines competitively inhibited BVDV attachment to cultured MDBK cells, suggesting the presence of BVDV receptor on all cells. Immunoblotting of cell membrane proteins with the anti-ids revealed a 50 kDa protein in both permissive and nonpermissive cells. Subcloned or synchronized MDBK cells demonstrated no significant difference of binding with anti-ids as compared to normal cultured cells.

A p65/p95 neural surface receptor is expressed at the S-G2 phase of the cell cycle and defines distinct populations

A surface receptor complex of Mr approximately 65 000 (p65) and approximately 95 000 (p95) is expressed in cells of the central nervous system of mice. This receptor is recognized by monoclonal antibody 87.92.6 or by reovirus type 3 haemagglutinin as unnatural ligands. The p65/p95 receptor is expressed mostly in neural embryonic precursors undergoing proliferation, especially those in the S-G2 phase of the cell cycle. Receptor expression decreases progressively throughout embryogenesis to low but detectable levels in the adult brain. Biochemical characterization revealed that the neural p65/p95 receptor complex is indistinguishable from the p65/p95 receptor expressed in T cells, where receptor ligation leads to a mitogenic block. In neural and lymphoid tissues the p65/p95 receptor (or an associated protein) possesses a tyrosine kinase enzymatic activity. Receptor ligation in neural cells resulted in the rapid tyrosine phosphorylation of cellular proteins which are different from substrates phosphorylated in T cells. Differential substrate coupling to the receptor may account for differences in signal transduction and biology between neural cells and T cells. Further study of this receptor complex may help define important features of neural proliferation, differentiation and survival.