SYNTHESIS AND PROCESSING OF THE EQUINE-HERPESVIRUS-1 GLYCOPROTEIN-M

In a previous report, the function of the equine herpesvirus 1 (EHV-1) glycoprotein M (gM) homolog was investigated. It was shown that EHV-1 gM is involved in both virus entry and direct cell-to-cell spread of Infection (N. Osterrieder at al, J. Virol. 70, 4110-4115, 1996). In th is study, experiments were conducted to analyze the synthesis, posttra nslational processing, and the putative ion channel function of EHV-1 gM. It was demonstrated that EHV-1 gM is synthesized as an M,44,000 po lypeptide, which is cotranslationally N-glycosylated to an M,46,000-48 ,000 glycoprotein. The M 46,000-48,000 gM moiety is processed to an M, 50,000-55,000 glycoprotein, which is resistant to treatment with endog lycosidase H, indicating that processing occurs in the Golgi network E HV-1 gM forms a dimer in infected cells and the virion, as was demonst rated by the presence of an M, 105,000-110,000 gM-containing band in e lectrophoretically separated lysates of infected cells and purified ex tracellular virions. The M, 105,000-110,000 protein band containing gM was also observed in lysates of cells that had been transfected with EHV-1 gM DNA. The translation of EHV-1 gM is initiated at the first in -frame methionine of the gM open reading frame as shown by transient t ransfection experiments of full-length gM and a truncated gM lacking t he aminoterminal 83 amino acids. Functional expression of EHV-1 gM in Xenopus laevis oocytes together with voltage-clamp analyses demonstrat ed that gM per se does not exhibit ion channel activity as had been sp eculated from the predicted structure of the polypeptide. (C) 1997 Aca demic Press.