Truncated forms of glycoprotein D of herpes simplex virus 1 capable of blocking apoptosis and of low-efficiency entry into cells form a heterodimer dependent on the presence of a cysteine located in the shared transmembrane domains.
Earlier studies have shown that herpes simplex virus 1 (HSV-1) virions of mutant lacking glycoprotein D (gD) and made in either complementing (gD(-/+) stocks) or noncomplementing cells (gD(-/-) stocks) induce apoptosis. Subsequent studies have shown that apoptosis induced by gD(-/-) mutant virus stocks can be blocked by in trans delivery of viral genes that encode either intact gD or a mixture of two genes encoding the glycoprotein ectodomain plus transmembrane domain (gD-B) and transmembrane domain plus the cytoplasmic carboxyl terminus of the protein (gD-D), respectively. Since the presence of the transmembrane domains was critical for precluding apoptosis in the bipartite system, the question arose whether the two components, gD-B and gD-D, form a heterodimer mediated by an unpaired cysteine located in the transmembrane domain. We report the following. (i) The substitution of the unpaired cysteine with serine in either gD-B or gD-D truncated forms of gD disabled the ability of gD-D and gD-B to block apoptosis. (ii) Immunoprecipitation of gD-D coprecipitated gD-B only from lysates of cells transduced with gD-D and gD-B containing the cysteine in the transmembrane domains. Replacement of cysteine with serine ablated coprecipitation of the components. (ii) The mixture of gD-D and gD-B complemented at a low level gD(-/+) virions. We conclude that the gD-B and gD-D can form a heterodimer dependent on the presence of cysteines in the transmembrane domain and the heterodimer can substitute for intact gD but at a much reduced efficiency.
Zhou
Guoying
G
The Marjorie B. Kovler Viral Oncology Laboratories, The University of Chicago, Chicago, Illinois 60637, USA.
Roizman
Bernard
B
D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D016367:Baculoviridae / Q000235:genetics; D002460:Cell Line; D003545:Cysteine / Q000737:chemistry; D019281:Dimerization; D018259:Herpesvirus 1, Human / Q000472:pathogenicity*; D006801:Humans; D009154:Mutation; D018411:Spodoptera; D014759:Viral Envelope Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology
D014759:Viral Envelope Proteins; C040495:glycoprotein B, Simplexvirus; C039447:glycoprotein D, Human herpesvirus 1; D003545:Cysteine