¹Department of Anatomy and Neuroscience, Graduate School of Medicine, Osaka University. 2-2 Yamadaoka Suita, Osaka 565-0871, Japan

²Department of Cellular and Structural Biology, Graduate School of Biological Sciences, Nara Institute of Science and Technology, 8916-5 Takayama Ikoma, Nara 630-0101, Japan

³CREST of Japan Science and Technology Corporation (JST), 2-2 Yamadaoka Suita, Osaka 565-0871, Japan

Correspondence to: D Yui, Department of Anatomy and Neuroscience, Graduate School of Medicine, Osaka University, 2-2 Yamadaoka Suita, Osaka 565-0871, Japan; Email: yui@anat2.med.osaka-u.ac.jp

Bcl10 was identified as a candidate gene responsible for low grade B cell lymphomas of mucosa-associated lymphoid tissue. Overexpression of Bcl10 in cultured cells was reported to promote apoptosis, however, the mechanism of regulation of apoptosis mediated by Bcl10 has not been demonstrated. In the present study, we analysed the apoptosis signaling pathway mediated by Bcl10, focusing on phosphorylation of Bcl10 and the dynamic interaction with its binding partners during apoptosis. Previously, we have demonstrated that Bcl10 potentially interacts with the other apoptosis regulator, TNF receptor associated factor-2 (TRAF2) and inhibitor of apoptosis proteins (cIAPs). The present results showed that the complex formation of these molecules was regulated by phosphorylation of Bcl10, that is, phosphorylation of Bcl10 resulted in binding of Bcl10 to cIAPs and the dissociation of it from TRAF2. Moreover, hyperphosphorylation of Bcl10 enhanced apoptosis, suggesting that changes in the binding partners of Bcl10 were correlated to the promotion of apoptosis as mediated by Bcl10. Indeed, the mutant which was deleted from the binding site of Bcl10 for cIAPs, could not induce apoptosis. These findings indicate that Bcl10 is a mediator of apoptosis signaling, by switching over binding to cIAPs from TRAF2 through the events of Bcl10 phosphorylation. Oncogene (2001) 20, 4317-4323.

Bcl10; TRAF2; cIAPs; phosphorylation; apoptosis