Arsenic trioxide induces a beclin-1-independent autophagic pathway via modulation of SnoN/SkiL expression in ovarian carcinoma cells.
Arsenic trioxide (As(2)O(3)), used to treat promyelocytic leukemia, triggers cell death through unknown mechanisms. To further our understanding of As(2)O(3)-induced death, we analyzed its effects on transforming growth factor-β (TGFβ) signaling mediators in ovarian cells. Dysregulated TGFβ signaling is a characteristic of ovarian cancers. As(2)O(3) reduced the protein expression of EVI1, TAK1, SMAD2/3, and TGFβRII while increasing SnoN/SkiL. EVI1 protein was modulated by treatment with the proteasome inhibitors, MG132 and PS-341/Velcade, suggesting that degradation occurs through the ubiquitin-proteasome pathway. The sensitivity of ovarian cells to As(2)O(3)-induced apoptosis correlated with expression of multidrug resistance protein 1. Interestingly, expression of SnoN was similar to LC3-II (autophagy marker), which increased with induction of cytoplasmic vacuolation preceding apoptosis. These vesicles were identified as autophagosomes based on transmission electron microscopy and immunofluorescence staining with EGFP-LC3. The addition of N-acetyl-L-cysteine (ROS scavenger) to As(2)O(3)-treated cells reversed changes in SnoN protein and the autophagic/apoptotic response. In contrast to beclin-1 knockdown, siRNA targeting ATG5, ATG7, and hVps34 markedly reduced autophagy in As(2)O(3)-treated ovarian carcinoma cells. Further, treatment with SnoN siRNA markedly decreased LC3-II levels and increased PARP degradation (an apoptosis marker). Collectively, these findings suggest that As(2)O(3) induces a beclin-1-independent autophagic pathway in ovarian carcinoma cells and implicates SnoN in promoting As(2)O(3)-mediated autophagic cell survival.
Department of Cell Biology, Microbiology, and Molecular Biology, University of South Florida, 4202 East Fowler Avenue, BSF218, Tampa, FL, USA.
D M
DM
Smith
S
S
Patel
F
F
Raffoul
E
E
Haller
G B
GB
Mills
M
M
Nanjundan
D000111:Acetylcysteine / Q000494:pharmacology; D051017:Apoptosis Regulatory Proteins / Q000235:genetics / Q000378:metabolism*; D000077237:Arsenic Trioxide; D001152:Arsenicals; D001343:Autophagy; D000071187:Autophagy-Related Protein 5; D000071193:Autophagy-Related Protein 7; D000071186:Beclin-1; D002277:Carcinoma / Q000378:metabolism*; D045744:Cell Line, Tumor; D005260:Female; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism*; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000378:metabolism; D010051:Ovarian Neoplasms / Q000378:metabolism*; D010087:Oxides / Q000633:toxicity*; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D015398:Signal Transduction; D016212:Transforming Growth Factor beta / Q000378:metabolism; D044764:Ubiquitin-Activating Enzymes / Q000235:genetics / Q000378:metabolism
D000111:Acetylcysteine; D051017:Apoptosis Regulatory Proteins; D000077237:Arsenic Trioxide; D001152:Arsenicals; D000071187:Autophagy-Related Protein 5; D000071193:Autophagy-Related Protein 7; D000071186:Beclin-1; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D008869:Microtubule-Associated Proteins; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D010087:Oxides; D011065:Poly(ADP-ribose) Polymerases; D011518:Proto-Oncogene Proteins; D034741:RNA, Small Interfering; D017382:Reactive Oxygen Species; D016212:Transforming Growth Factor beta; D044764:Ubiquitin-Activating Enzymes; C502778:ATG5 protein, human; C491997:BECN1 protein, human; C477012:MAP1LC3A protein, human; C060615:SKIL protein, human; C509349:ATG7 protein, human; C421109:multidrug resistance-associated protein 1