title: Dimer of arfaptin 2 regulates NF-κB signaling by interacting with IKKβ/NEMO and inhibiting IKKβ kinase activity.
abstract: IκB kinases (IKKs) are a therapeutic target due to their crucial roles in various biological processes, including the immune response, the stress response, and tumor development. IKKs integrate various upstream signals that activate NF-κB by phosphorylating IκB and also regulate many proteins related to cell growth and metabolism. Although they function as a heteromeric complex comprised of kinase subunits and an adaptor, these kinases produce distinct cellular responses by phosphorylating different target molecules, suggesting that they may also be regulated in a subtype-specific manner. In this study, arfaptin 2 was identified as an IKKβ-specific binding partner. Interestingly, arfaptin 2 also interacted with NEMO. Domain mapping studies revealed that the C-terminal region, including the IKKβ HLH domain and the first coiled-coil NEMO region were respectively required for interactions with the arfaptin 2 N-terminal flexible region. Overexpression of arfaptin 2 inhibited tumor necrosis factor (TNF)-α-stimulated nuclear factor-κB (NF-κB) signaling, whereas downregulation of arfaptin 2 by small interfering RNA enhanced NF-κB activity. Dimerization of arfaptin 2 through the Bin-Amphiphysin-Rvs domain may be essential to inhibit activation of NF-κB through multimodal interactions with IKKβs or IKKβ/NEMO, as ectopic expression of the arfaptin 2 fragment responsible for IKK interactions did not change TNFα-stimulated NF-κB activation. These data indicate that arfaptin 2 is the first molecule to regulate NF-κB signaling by interacting with the functional IKK complex but not by direct inhibiting IKKβ phosphorylation.
authors: Graduate School of Medicine, Korea University, 73 Inchon-ro, Seongbuk-gu, Seoul 136-705, Republic of Korea.
authors: Dong-Joo
authors: DJ
authors: You
authors: Graduate School of Medicine, Korea University, 73 Inchon-ro, Seongbuk-gu, Seoul 136-705, Republic of Korea.
authors: Cho Rong
authors: CR
authors: Park
authors: Graduate School of Medicine, Korea University, 73 Inchon-ro, Seongbuk-gu, Seoul 136-705, Republic of Korea.
authors: Michael
authors: M
authors: Furlong
authors: Samsung Biomedical Research Institute, 130 Samsung-ro, Yeongtong-gu, Suwon-si, Gyeonggi-do 433-803, Republic of Korea.
authors: Okjae
authors: O
authors: Koo
authors: Life Sciences Division, Korea Institute of Science and Technology, Seongbuk-gu, Seoul 136-791, Republic of Korea.
authors: Cheolju
authors: C
authors: Lee
authors: Transplantation Research Institute, Cancer Research Institute, Seoul National University, Yongun-dong, Jongno-gu, Seoul 110-799, Republic of Korea.
authors: Curie
authors: C
authors: Ahn
authors: Graduate School of Medicine, Korea University, 73 Inchon-ro, Seongbuk-gu, Seoul 136-705, Republic of Korea.
authors: Jae Young
authors: JY
authors: Seong
authors: Graduate School of Medicine, Korea University, 73 Inchon-ro, Seongbuk-gu, Seoul 136-705, Republic of Korea. Electronic address: hjibio@korea.ac.kr.
authors: Jong-Ik
authors: JI
authors: Hwang
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D019281:Dimerization; D057809:HEK293 Cells; D006801:Humans; D051550:I-kappa B Kinase / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000235:genetics; D015398:Signal Transduction / Q000502:physiology; D051996:Transcription Factor RelA / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism*
chemical_list: C101158:ARFIP2 protein, human; D048868:Adaptor Proteins, Signal Transducing; C491731:IKBKG protein, human; C498143:RELA protein, human; D034741:RNA, Small Interfering; D051996:Transcription Factor RelA; D014409:Tumor Necrosis Factor-alpha; D051550:I-kappa B Kinase
keywords: Arfaptin 2; BAR domain; IκB kinases; NF-κB; TNF-α