Identification of a Novel Apoptosis Suppressor Gene from the Baculovirus Lymantria dispar Multicapsid Nucleopolyhedrovirus

Abstract

Ld652Y cells from

Novel Apoptosis Suppressor Apsup from the Baculovirus Lymantria dispar Multiple Nucleopolyhedrovirus Precludes Apoptosis by Preventing Proteolytic Processing of Initiator Caspase Dronc

“…The apsup-silenced Ld652Y cells underwent apoptosis accompanied by the activation of caspase-3-like protease upon infection with LdMNPV, whereas the egfp-silenced Ld652Y cells exhibited no detectable apoptotic morphology or caspase-3-like protease activity (data not shown) following LdMNPV infection and produced a number of polyhedra, in accordance with the previous results (10). Immunoblot analysis showed that cleaved Ld-Dronc was first detected in apsup-silenced Ld652Y cells at 24 h postinfection as a weak but clear band that increased in intensity at 48 and 72 h postinfection, whereas cleaved Ld-Dronc was not detected in egfp-silenced Ld652Y cells, even at 72 h postinfection (Fig.…”

“…Apsup was detected only in egfp-silenced LdMNPVinfected Ld652Y cells (Fig. 5B), similar to the results of a previous study (10). These results provide evidence that Apsup precludes apoptosis by preventing the proteolytic processing and activation of Ld-Dronc in LdMNPV-infected Ld652Y cells.…”

“…Among the insect cell lines examined to date, Ld652Y cells from the gypsy moth Lymantria dispar are particularly sensitive to apoptotic stimuli and undergo apoptosis upon infection with various nucleopolyhedroviruses (NPVs), including those from Bombyx mori, Hyphantria cunea, Orgyia pseudotsugata, Spodoptera exigua, and Spodoptera litura (7). Studies on the mechanisms of baculovirus-induced apoptosis collectively indicate that apoptosis is typically induced in insect cells upon baculovirus infection and that in cell lines permissive for productive baculovirus infection, virus-induced apoptosis is precluded by baculovirusencoded apoptosis suppressors (8)(9)(10). Thus, apoptosis suppressors are essential for baculoviruses to survive intracellular antiviral immunity of host cells.…”

“…Antibody against purified BmNPV polyhedrin was prepared in a rabbit as described previously (49,50). Preparation of polyclonal antibody against Apsup (Ld109) protein has been described previously (10). Horseradish peroxidase-conjugated goat anti-rabbit IgG and goat anti-mouse IgG (Zymed Laboratories) were used as the secondary antibodies.…”

“…Double-stranded RNAs (dsRNAs) against apsup and egfp were synthesized using a MEGAscript T7 kit (Ambion) as described previously (10,45). The synthesized dsRNA was introduced into Ld652Y cells by transfection.…”