Identification of an acetylation-dependant Ku70/FLIP complex that regulates FLIP expression and HDAC inhibitor-induced apoptosis.
FLIP is a potential anti-cancer therapeutic target that inhibits apoptosis by blocking caspase 8 activation by death receptors. We report a novel interaction between FLIP and the DNA repair protein Ku70 that regulates FLIP protein stability by inhibiting its polyubiquitination. Furthermore, we found that the histone deacetylase (HDAC) inhibitor Vorinostat (SAHA) enhances the acetylation of Ku70, thereby disrupting the FLIP/Ku70 complex and triggering FLIP polyubiquitination and degradation by the proteasome. Using in vitro and in vivo colorectal cancer models, we further demonstrated that SAHA-induced apoptosis is dependant on FLIP downregulation and caspase 8 activation. In addition, an HDAC6-specific inhibitor Tubacin recapitulated the effects of SAHA, suggesting that HDAC6 is a key regulator of Ku70 acetylation and FLIP protein stability. Thus, HDAC inhibitors with anti-HDAC6 activity act as efficient post-transcriptional suppressors of FLIP expression and may, therefore, effectively act as 'FLIP inhibitors'.
Centre for Cancer Research and Cell Biology, School of Medicine, Dentistry and Biomedical Science, Queen's University Belfast, Northern Ireland, UK.
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E
Kerr
C
C
Holohan
K M
KM
McLaughlin
J
J
Majkut
S
S
Dolan
K
K
Redmond
J
J
Riley
K
K
McLaughlin
I
I
Stasik
M
M
Crudden
S
S
Van Schaeybroeck
C
C
Fenning
R
R
O'Connor
P
P
Kiely
M
M
Sgobba
D
D
Haigh
P G
PG
Johnston
D B
DB
Longley
D000107:Acetylation; D000595:Amino Acid Sequence; D000818:Animals; D034961:Antigens, Nuclear / Q000235:genetics / Q000378:metabolism*; D017209:Apoptosis / Q000187:drug effects*; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D053181:Caspase 8 / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D015536:Down-Regulation; D005260:Female; D045325:HCT116 Cells; D019073:HT29 Cells; D000073864:Histone Deacetylase 6; D056572:Histone Deacetylase Inhibitors / Q000494:pharmacology*; D006655:Histone Deacetylases / Q000378:metabolism; D006801:Humans; D006877:Hydroxamic Acids / Q000494:pharmacology; D000072200:Ku Autoantigen; D051379:Mice; D008807:Mice, Inbred BALB C; D011499:Protein Processing, Post-Translational; D034741:RNA, Small Interfering / Q000008:administration & dosage / Q000235:genetics; D014162:Transfection; D000077337:Vorinostat
D034961:Antigens, Nuclear; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; D004268:DNA-Binding Proteins; D056572:Histone Deacetylase Inhibitors; D006877:Hydroxamic Acids; D034741:RNA, Small Interfering; D000077337:Vorinostat; C505530:CASP8 protein, human; D053181:Caspase 8; C433811:HDAC6 protein, human; D000073864:Histone Deacetylase 6; D006655:Histone Deacetylases; C000606509:Xrcc6 protein, human; C000606510:Xrcc6 protein, mouse; D000072200:Ku Autoantigen