Does the beta-adrenergic receptor function as a reovirus receptor?

A reovirus (type 3) receptor has previously been identified on the mouse thymoma R1.1 cell line and shown to be structurally similar to the mammalian beta-adrenergic receptor [M. S. Co, G. N. Gaulton, A. Tominaga, C.J. Homcy, B.N. Fields, and M.I. Greene (1985). Proc. Natl. Acad. Sci. USA 82, 5315-5318]. To determine whether beta-adrenergic receptors are universal recognition signals for reovirus binding, we studied the human epidermoid carcinoma cell line A431 which is known to possess large numbers of functional beta-adrenergic receptors and was found in the present study to be susceptible to reovirus infection. It was observed that unlike beta-adrenergic agonists, reovirus binding and internalization did not result in the triggering of cellular adenylate cyclase activity. The presence of reovirus also had no effect on cellular response to the agonist (-)-isoproterenol, nor on the binding of the hydrophilic antagonist [3H]CGP-12,177 to intact A431 cells. Furthermore, sequestration of beta-adrenergic receptors from the cell surface by (-)-isoproterenol had no effect on reovirus binding. Conversely, the binding of [3H]CGP-12,177 to cells with internalized reovirus receptors was found to be normal. These data strongly suggest that reovirus and beta-adrenergic receptors on A431 cells are distinct from each other. Similar observations were also made with the mouse L fibroblasts, with the exception that these cells appear to possess few functional beta-adrenergic receptors.