RACK1 promotes Bax oligomerization and dissociates the interaction of Bax and Bcl-XL.
Bax, a member of Bcl-2 family, plays an essential role in apoptotic pathways induced by a number of apoptotic stimulus. In a search for new potential binding partners of Bax, we identified the receptor for activated C-kinase 1 (RACK1) by a yeast two-hybrid assay. We demonstrated that RACK1 interacts with Bax through its BH3 domain both in vitro and in vivo. Using immunostaining and immunoprecipitation experiments, we found that RACK1 colocalizes with Bax oligomers and promotes Bax oligomerization both in vitro and in vivo. Furthermore, we observed that RACK1 also interacts with Bcl-XL, an anti-apoptotic protein associated with Bax. Interestingly, the Bcl-XL/Bax interaction is decreased when RACK1 is overexpressed, but is increased when RACK1 is depleted, suggesting RACK1 disrupts the association of Bax and Bcl-XL. In addition, we found that overexpression of RACK1 promotes UV-induced apoptosis, while knocking down RACK1 inhibits the effects. Together, these results indicate that RACK1 promotes apoptosis by promoting Bax oligomerization and dissociating the complex of Bax and Bcl-XL.
Wu
Yinyuan
Y
School of Medicine, Department of Biological Sciences and Biotechnology, State Key Laboratory of Biomembrane and Membrane Biotechnology, Tsinghua University, Beijing (100084), China.
Wang
Yinyin
Y
Sun
Yang
Y
Zhang
Liying
L
Wang
Dianjun
D
Ren
Fangli
F
Chang
Donald
D
Chang
Zhijie
Z
Jia
Baoqing
B
D017209:Apoptosis; D002460:Cell Line; D006801:Humans; D054730:Protein Interaction Domains and Motifs; D000075370:Receptors for Activated C Kinase; D011956:Receptors, Cell Surface / Q000032:analysis / Q000378:metabolism*; D014466:Ultraviolet Rays; D051028:bcl-2-Associated X Protein / Q000032:analysis / Q000737:chemistry / Q000378:metabolism*; D051020:bcl-X Protein / Q000378:metabolism*
D000075370:Receptors for Activated C Kinase; D011956:Receptors, Cell Surface; D051028:bcl-2-Associated X Protein; D051020:bcl-X Protein