title: Ubiquitination and degradation of the hominoid-specific oncoprotein TBC1D3 is mediated by CUL7 E3 ligase.
abstract: Expression of the hominoid-specific TBC1D3 oncoprotein enhances growth factor receptor signaling and subsequently promotes cellular proliferation and survival. Here we report that TBC1D3 is degraded in response to growth factor signaling, suggesting that TBC1D3 expression is regulated by a growth factor-driven negative feedback loop. To gain a better understanding of how TBC1D3 is regulated, we studied the effects of growth factor receptor signaling on TBC1D3 post-translational processing and turnover. Using a yeast two-hybrid screen, we identified CUL7, the scaffolding subunit of the CUL7 E3 ligase complex, as a TBC1D3-interacting protein. We show that CUL7 E3 ligase ubiquitinates TBC1D3 in response to serum stimulation. Moreover, TBC1D3 recruits F-box 8 (Fbw8), the substrate recognition domain of CUL7 E3 ligase, in pull-down experiments and in an in vitro assay. Importantly, alkaline phosphatase treatment of TBC1D3 suppresses its ability to recruit Fbw8, indicating that TBC1D3 phosphorylation is critical for its ubiquitination and degradation. We conclude that serum- and growth factor-stimulated TBC1D3 ubiquitination and degradation are regulated by its interaction with CUL7-Fbw8.
authors.affiliation: Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri, United States of America.
authors.forename: Chen
authors.initials: C
authors.lastname: Kong
authors.forename: Dmitri
authors.initials: D
authors.lastname: Samovski
authors.forename: Priya
authors.initials: P
authors.lastname: Srikanth
authors.forename: Marisa J
authors.initials: MJ
authors.lastname: Wainszelbaum
authors.forename: Audra J
authors.initials: AJ
authors.lastname: Charron
authors.forename: Jialiu
authors.initials: J
authors.lastname: Liu
authors.forename: Jeffrey J
authors.initials: JJ
authors.lastname: Lange
authors.forename: Pin-I
authors.initials: PI
authors.lastname: Chen
authors.forename: Zhen-Qiang
authors.initials: ZQ
authors.lastname: Pan
authors.forename: Xiong
authors.initials: X
authors.lastname: Su
authors.forename: Philip D
authors.initials: PD
authors.lastname: Stahl
mesh_terms: D044842:Cullin Proteins / Q000378:metabolism*; D044783:F-Box Proteins / Q000378:metabolism*; D020690:GTPase-Activating Proteins / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000502:physiology; D007976:Leupeptins / Q000494:pharmacology; D010766:Phosphorylation; D061988:Proteasome Inhibitors / Q000494:pharmacology; D011485:Protein Binding; D011499:Protein Processing, Post-Translational; D059748:Proteolysis; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D020798:Two-Hybrid System Techniques; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism; D054875:Ubiquitination
chemical_list: C506299:CUL7 protein, human; D044842:Cullin Proteins; D044783:F-Box Proteins; C526069:FBXW8 protein, human; D020690:GTPase-Activating Proteins; D036341:Intercellular Signaling Peptides and Proteins; D007976:Leupeptins; D061988:Proteasome Inhibitors; D011518:Proto-Oncogene Proteins; C467563:TBC1D3 protein, human; D044767:Ubiquitin-Protein Ligases; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde