A short caspase-3 isoform inhibits chemotherapy-induced apoptosis by blocking apoptosome assembly.
Alternative splicing of caspase-3 produces a short isoform caspase-3s that antagonizes caspase-3 apoptotic activity. However, the mechanism of apoptosis inhibition by caspase-3s remains unknown. Here we show that exogenous caspase-3 sensitizes MCF-7 and HBL100 breast cancers cells to chemotherapeutic treatments such as etoposide and methotrexate whereas co-transfection with caspase-3s strongly inhibits etoposide and methotrexate-induced apoptosis underlying thus the anti-apoptotic role of caspase-3s. In caspase-3 transfected cells, lamin-A and α-fodrin were cleaved when caspase-3 was activated by etoposide or methotrexate. When caspase-3s was co-transfected, this cleavage was strongly reduced. Depletion of caspase-3 by RNA interference in HBL100 containing endogenous caspase-3s caused reduction in etoposide and methotrexate-induced apoptosis, whereas the depletion of caspase-3s sensitized cells to chemotherapy. In the presence of caspase-3s, a lack of interaction between caspase-3 and caspase-9 was observed. Immunoprecipitation assays showed that caspase-3s binds the pro-forms of caspase-3. This result suggested that the absence of interaction with caspase-9 when both variants of caspase-3 are present contribute to block the apoptosome assembly and inhibit apoptosis. These data support that caspases-3s negatively interferes with caspase-3 activation and apoptosis in breast cancer, and that it can play key roles in the modulation of response to chemotherapeutic treatments.
Unit of Molecular Biology - Centre Georges François Leclerc, Dijon, France.
Frédérique
F
Végran
Romain
R
Boidot
Eric
E
Solary
Sarab
S
Lizard-Nacol
D000595:Amino Acid Sequence; D017209:Apoptosis / Q000187:drug effects*; D053478:Apoptosomes / Q000187:drug effects*; D001483:Base Sequence; D015153:Blotting, Western; D001943:Breast Neoplasms / Q000201:enzymology / Q000473:pathology; D053148:Caspase 3 / Q000737:chemistry / Q000378:metabolism*; D045744:Cell Line, Tumor; D017931:DNA Primers; D004789:Enzyme Activation; D006801:Humans; D007527:Isoenzymes / Q000737:chemistry / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D060888:Real-Time Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid
D053478:Apoptosomes; D017931:DNA Primers; D007527:Isoenzymes; D053148:Caspase 3