Sf-Caspase-I [Spodoptera frugiperda (fall armyworm) caspase-1] is the most studied effector caspase of Lepidoptera and its activation may lead cells to apoptosis (programmed cell death) when under UV irradiation or baculovirus infection. In the present study, we repressed the expression of Sf-caspase-I in Sf9 (S. frugiperda 9) cells using constitutive RNA interference, and evaluated the effects of stress responses and the production of proteins in recombinant baculovirus-infected cells. The Sf-caspase-I-repressed stable cells, Sf9/pIBdsCasp-I and Sf9/pIBdsCasp-2, showed a significant increase in resistance to UV- and baculovirus-induced apoptosis. These cells produced higher levels of both intracellular (luciferase) and extracellular [SEAP (secreted alkaline phosphatase)] recombinant proteins than the parental cells when infected with recombinant baculovirus. Thus Sfcaspase-I-repressed stable cells have a greater ability to adapt to various culture conditions, and also to provide the benefits of high-level protein production.
