title: RhoB induces apoptosis via direct interaction with TNFAIP1 in HeLa cells.
abstract: RhoB, a tumor suppressor, has emerged as an interesting cancer target, and extensive studies aimed at understanding its role in apoptosis have been performed. In our study, we investigated the involvement of RhoB-interacting molecules in apoptosis. To identify RhoB-interacting proteins, we performed yeast-two hybrid screening assays using RhoB as a bait and isolated TNFAIP1, a TNFalpha-induced protein containing the BTB/POZ domain. The interaction between RhoB and TNFAIP1 was demonstrated in vivo through coimmunoprecipitation studies and in vitro binding assays. RFP-TNFAIP1 was found to be partially colocalized with EGFP-RhoB. The partial colocalization of RhoB and TNFAIP1 in endosomes suggests that RhoB-TNFAIP1 interactions may have a functional role in apoptosis. TNFAIP1 elicited proapoptotic activity, while simultaneous expression of RhoB and TNFAIP1 resulted in a dramatic increase in apoptosis in HeLa cells. Furthermore, knockdown of RhoB using siRNA clearly rescued cells from apoptosis induced by TNFAIP1. This finding suggests that interactions between RhoB and TNFAIP1 are crucial for induction of apoptosis in HeLa cells. The observation of increased SAPK/JNK phosphorylation in apoptotic cells and the finding that a JNK inhibitor suppressed apoptosis indicates that SAPK/JNK signaling may be involved in apoptosis induced by RhoB-TNFAIP1 interactions. In conclusion, we found that RhoB interacts with TNFAIP1 to regulate apoptosis via a SAPK/JNK-mediated signal transduction mechanism.
authors.affiliation: Department of Biological Science, KAIST, Daejeon 305-701, Korea.
authors.forename: Dong-Myung
authors.initials: DM
authors.lastname: Kim
authors.forename: Kyung-Sook
authors.initials: KS
authors.lastname: Chung
authors.forename: Shin-Jung
authors.initials: SJ
authors.lastname: Choi
authors.forename: Yu-Jin
authors.initials: YJ
authors.lastname: Jung
authors.forename: Song-Kyu
authors.initials: SK
authors.lastname: Park
authors.forename: Gyoon-Hee
authors.initials: GH
authors.lastname: Han
authors.forename: Jae-Seok
authors.initials: JS
authors.lastname: Ha
authors.forename: Kyung-Bin
authors.initials: KB
authors.lastname: Song
authors.forename: Nam-Song
authors.initials: NS
authors.lastname: Choi
authors.forename: Hwan-Mook
authors.initials: HM
authors.lastname: Kim
authors.forename: Misun
authors.initials: M
authors.lastname: Won
authors.forename: Yeon-Soo
authors.initials: YS
authors.lastname: Seo
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D017209:Apoptosis; D015153:Blotting, Western; D049109:Cell Proliferation; D005434:Flow Cytometry; D006367:HeLa Cells / Q000378:metabolism / Q000473:pathology; D006801:Humans; D047468:Immunoprecipitation; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D011506:Proteins / Q000378:metabolism*; D015398:Signal Transduction; D020798:Two-Hybrid System Techniques; D020743:rhoB GTP-Binding Protein / Q000378:metabolism*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D011506:Proteins; C115968:TNFAIP1 protein, human; D048031:JNK Mitogen-Activated Protein Kinases; D020743:rhoB GTP-Binding Protein