Phosphorylation of Smac by JNK3 attenuates its interaction with XIAP.
Here we demonstrate that JNK3 can phosphorylate Smac. Smac phosphorylation attenuates its ability to activate apoptosome activity in HeLa S-100 cell lysates. Addition of the X-linked inhibitor of apoptosis protein (XIAP) to the S-100 markedly suppresses apoptosome activity, and this suppressive effect of XIAP is neutralized by adding unphosphorylated Smac, but not phosphorylated Smac. Furtherover, JNK3-mediated phosphorylation of Smac markedly attenuates the interaction between Smac and XIAP, as measured by BIACORE assays and non-denaturing gel shift assays. When JNK3 activity is down-regulated in etoposide-induced HeLa cells by transiently overexpressing a dominant negative version of JNK3 (DN-JNK3), the caspase-3 activity as well as PARP cleavages are markedly enhanced. And the interaction of Smac with XIAP also increases by down-regulating JNK3 activity under the same conditions. These results suggest that JNK3 activity can attenuate the progression of apoptosis through a novel mechanism of action, the down-regulation of interaction between Smac and XIAP.
Division of Pharmaceutical Biosciences, College of Pharmacy and the Research Institute for Pharmaceutical Sciences, Seoul National University, Seoul 151-742, Republic of Korea.
Byoung Duck
BD
Park
Young Mi
YM
Ham
Hyun Ji
HJ
Jeong
Seung Ju
SJ
Cho
Young Tae
YT
Je
Kyu Dong
KD
Yoo
Seung-Ki
SK
Lee
D017209:Apoptosis; D051017:Apoptosis Regulatory Proteins; D005047:Etoposide / Q000494:pharmacology; D006367:HeLa Cells; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism*; D024101:Mitochondrial Proteins / Q000378:metabolism*; D048057:Mitogen-Activated Protein Kinase 10 / Q000378:metabolism*; D048055:Mitogen-Activated Protein Kinase 8 / Q000378:metabolism; D010766:Phosphorylation; D051636:X-Linked Inhibitor of Apoptosis Protein / Q000378:metabolism*
D051017:Apoptosis Regulatory Proteins; C412403:DIABLO protein, human; D047908:Intracellular Signaling Peptides and Proteins; D024101:Mitochondrial Proteins; D051636:X-Linked Inhibitor of Apoptosis Protein; D005047:Etoposide; D048057:Mitogen-Activated Protein Kinase 10; D048055:Mitogen-Activated Protein Kinase 8