Transient expression assay reveals kinetic difference in the proteolytic processing between Dronc proteins from the gypsy moth Lymantria dispar and the silkworm Bombyx mori.

Ld652Y cells from the gypsy moth, Lymantria dispar, are highly sensitive to apoptotic stimuli compared to BM-N cells from the silkworm, Bombyx mori, and undergo apoptosis upon infection with various nucleopolyhedroviruses (NPVs). We previously cloned and characterized Dronc homologues from L. dispar Ld652Y and B. mori BM-N cells and demonstrated that L. dispar Dronc (Ld-Dronc) undergoes proteolytic processing more rapidly and extensively than does B. mori Dronc (Bm-Dronc) upon infection with vAc?p35, a p35-defective Autographa californica multiple NPV. Here, we comparatively examined expression and proteolytic processing of the Ld- and Bm-Dronc proteins in the transient expression assays using three different insect cell lines, Ld652Y, BM-N and Spodoptera frugiperda Sf9. We demonstrate that even in the transient expression assays, Ld-Dronc undergoes proteolytic processing and activates caspase-3-like protease more rapidly and extensively than Bm-Dronc in a cell-line independent manner. These results indicate that intrinsic properties of Dronc are involved in the differing capacity of Ld652Y and BM-N cells to induce apoptosis in response to apoptotic stimuli, including NPV infection. [ABSTRACT FROM AUTHOR]