Interactions of DNR1 with the apoptotic machinery of Drosophila melanogaster.
Caspases are crucial activators of apoptosis and NF-kappaB signaling in vertebrates and invertebrates. In Drosophila, the caspase-9 counterpart Dronc is essential for most apoptotic death, whereas the caspase-8 homolog Dredd activates NF-kappaB signaling in response to gram-negative bacterial infection. The mechanics of caspase regulation are conserved and include the activities of a family of inhibitor of apoptosis (IAP) proteins. The RING-domain-bearing protein Defense repressor 1 (Dnr1), blocks ectopic Dredd-mediated induction of an NF-kappaB reporter in the Drosophila S2 cell line. In this study, we present novel data indicating that Dnr1 impacts on Dronc-dependent regulation of the apoptotic program. We show that depletion of Dnr1 results in elevated Dronc protein levels, which translates to increased caspase activation and activity upon induction of apoptosis. Conversely, we demonstrate that overexpression of Dnr1 blocks apoptotic caspase activity and prevents induction of apoptosis in tissue culture assays. Furthermore, we show that Dnr1 overexpression significantly reduces Dronc protein levels and identify the domains of Dnr1 necessary for these effects. From these data, we propose that Dnr1 inhibits initiator caspases in S2 cells.
Primrose
David A
DA
Department of Medical Microbiology and Immunology, University of Alberta, Edmonton AB, T6G 2S2, Canada.
Chaudhry
Sidharth
S
Johnson
A George D
AG
Hrdlicka
Adam
A
Schindler
Anja
A
Tran
Dave
D
Foley
Edan
E
D000818:Animals; D017209:Apoptosis; D020169:Caspases / Q000032:analysis / Q000378:metabolism*; D002460:Cell Line; D029721:Drosophila Proteins / Q000032:analysis / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000166:cytology / Q000378:metabolism / Q000502:physiology*; D019085:Fluorescent Antibody Technique, Direct; D017930:Genes, Reporter; D051034:Inhibitor of Apoptosis Proteins / Q000032:analysis / Q000378:metabolism*; D008856:Microscopy, Fluorescence; D018715:Microscopy, Video; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism; D016133:Polymerase Chain Reaction; D017434:Protein Structure, Tertiary; D012097:Repressor Proteins / Q000032:analysis / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
D029721:Drosophila Proteins; D051034:Inhibitor of Apoptosis Proteins; D016328:NF-kappa B; D012097:Repressor Proteins; D020169:Caspases; C109171:drICE protein, Drosophila; C431887:dredd protein, Drosophila; C118731:dronc protein, Drosophila