title: The Spodoptera frugiperda effector caspase Sf-caspase-1 becomes unstable following its activation.
abstract: Sf-caspase-1 is the principal effector caspase in Spodoptera frugiperda cells. Like the caspases in other organisms, Sf-caspase-1 is processed by upstream caspases to form an active heterotetramer composed of the p19 and p12 subunits. The regulation of active caspases is crucial for cellular viability. In mammal cells, the subunits and the active form of caspase-3 were rapidly degraded relative to its proenzyme form. In the present study, the S. frugiperda Sf9 cells were transiently transfected with plasmids encoding different fragments of Sf-caspase-1: the pro-Sf-caspase-1 (p37), a prodomain deleted fragment (p31), a fragment containing the large subunit and the prodomain (p25), the large subunit (p19), and the small subunit (p12). Flow cytometry and Western blot analysis revealed that p12, p19, and p25 were unstable in the transfected cells, in contrast to p37 and p31. Lactacystin, a proteasome inhibitor, increased the accumulation of the p19 and p12 subunits, suggesting that the degradation is performed by the ubiquitin-proteasome system. During the activation, the Sf-caspase-1 produces an intermediate form and then undergoes proteolytic processing to form active Sf-caspase-1. We found that both the active and the intermediate form were unstable, indicating that once activated or during its activation, the Sf-caspase-1 was unstable.
authors.affiliation: State Key Laboratory of Biocontrol, Sun Yat-sen University, Guangzhou, PR China.
authors.forename: Zhongfu
authors.initials: Z
authors.lastname: Ying
authors.forename: Ao
authors.initials: A
authors.lastname: Li
authors.forename: Zhaodan
authors.initials: Z
authors.lastname: Lu
authors.forename: Chunfeng
authors.initials: C
authors.lastname: Wu
authors.forename: Hanqi
authors.initials: H
authors.lastname: Yin
authors.forename: Meijin
authors.initials: M
authors.lastname: Yuan
authors.forename: Yi
authors.initials: Y
authors.lastname: Pang
mesh_terms: D000111:Acetylcysteine / Q000031:analogs & derivatives; D000818:Animals; D015153:Blotting, Western; D020169:Caspases / Q000378:metabolism*; D003001:Cloning, Molecular; D017931:DNA Primers / Q000235:genetics; D004789:Enzyme Activation / Q000502:physiology*; D004795:Enzyme Stability / Q000502:physiology; D005434:Flow Cytometry; D020287:In Situ Nick-End Labeling; D007211:Indoles; D016297:Mutagenesis, Site-Directed; D021122:Protein Subunits / Q000378:metabolism; D061987:Sf9 Cells; D018411:Spodoptera / Q000201:enzymology*
chemical_list: D017931:DNA Primers; D007211:Indoles; D021122:Protein Subunits; C067713:lactacystin; C007293:DAPI; D020169:Caspases; D000111:Acetylcysteine
keywords: Sf-caspase-1; lactacystin; ubiquitin-proteasome system