Parkinson's disease (PD) is characterized by progressive midbrain dopaminergic neuron degeneration and the formation of intracellular protein aggregates, referred to as Lewy bodies. F-box only protein 7 (FBXO7) gene mutations are closely associated with progression of the autosomal recessive form of familial PD. FBXO7 encodes a component of Skp1, cullin, F-box ubiquitin ligase complexes; however, its cellular targets, including substrates and regulators, are not yet clarified. To identify potential substrates of FBXO7, we performed a yeast two-hybrid screen of a human fetal brain library and identified neurotrophin receptor-interacting MAGE protein (NRAGE) as a novel FBXO7-binding partner. We found that FBXO7 interacts with NRAGE and mediates Lys-63-linked poly-ubiquitination of NRAGE in mammalian cells. FBXO7 overexpression accelerates formation of NRAGE-TAK1-TAB1 complexes, whereas FBXO7 knockdown correspondingly decreases complex formation. In addition, BMP4 stimulation enhances NRAGE ubiquitination through FBXO7 and facilitates endogenous NRAGE-TAK1-TAB1 complex formation. Furthermore, FBXO7 positively regulates formation of the BMP receptor-NRAGE-TAK1-TAB1 complex, and up-regulates NF-κB activity. Taken together, our results suggest that FBXO7 affects BMP4-mediated signaling through proteasome-independent ubiquitination of NRAGE and augments formation of downstream signaling components.
Bibliographical noteFunding Information:
The authors thank H.J. Kuiken, C.Y. You, J.M. Verdi, and G. Takausu for providing plasmids and J.H. Lee for providing P19 cells. The authors also thank Y.J. Oh and Y.K. Jang for their helpful discussion and comments. This work was supported by the National Research Foundation of Korea (NRF) grants (2012R1A1A2021749 and 2007-0056092 to K.C.C.) funded by the Ministry of Science, ICT & Future Planning (MSIP), Republic of Korea. This work was also partially supported by grants from the Korea Healthcare Technology R&D Project, Ministry for Health and Welfare (A092004 and A111653 to K.C.C).
© Springer 2014.
All Science Journal Classification (ASJC) codes
- Molecular Medicine
- Molecular Biology
- Cellular and Molecular Neuroscience
- Cell Biology