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Fbx8 makes Arf6 refractory to function via ubiquitination.

ABSTRACT: The small GTP-binding protein Arf6 regulates membrane remodeling at cell peripheries and plays crucial roles in higher orders of cellular functions including tumor invasion. Here we show that Fbx8, an F-box protein bearing the Sec7 domain, mediates ubiquitination of Arf6. This ubiquitination did not appear to be linked to immediate proteasomal degradation of Arf6, whereas Fbx8 knockdown caused hyperactivation of Arf6. Expression of Fbx8 protein was substantially lost in several breast tumor cell lines, in which Arf6 activity is pivotal for their invasion. Forced expression of Fbx8 in these cells suppressed their Arf6 activities and invasive activities, in which the F-box and Sec7 domains of Fbx8 are required. Together with the possible mechanism as to how Fbx8-mediated ubiquitination interferes with the functions of Arf6, we propose that Fbx8 provides a novel suppressive control of Arf6 activity through noncanonical ubiquitination. Our results indicate that dysfunction of Fbx8 expression may contribute to the invasiveness of some breast cancer cells.

SUBMITTER: Yano H

PROVIDER: S-EPMC2262996 | biostudies-literature | 2008 Mar

REPOSITORIES: biostudies-literature

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Fbx8 makes Arf6 refractory to function via ubiquitination.

Yano Hajime H Kobayashi Itaru I Onodera Yasuhito Y Luton Frédéric F Franco Michel M Mazaki Yuichi Y Hashimoto Shigeru S Iwai Kazuhiro K Ronai Ze'ev Z Sabe Hisataka H

Molecular biology of the cell 20071219 3

The small GTP-binding protein Arf6 regulates membrane remodeling at cell peripheries and plays crucial roles in higher orders of cellular functions including tumor invasion. Here we show that Fbx8, an F-box protein bearing the Sec7 domain, mediates ubiquitination of Arf6. This ubiquitination did not appear to be linked to immediate proteasomal degradation of Arf6, whereas Fbx8 knockdown caused hyperactivation of Arf6. Expression of Fbx8 protein was substantially lost in several breast tumor cell ...[more]

PMID: 18094045

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Project description:BackgroundColorectal cancer (CRC) is characterized by its aggressiveness and high fatality rate. Long noncoding RNAs (lncRNAs) as molecular scaffolding in CRC have received little attention.MethodsThe TCGA database was used to find putative anti-oncogenic lncRNAs in CRC. The effect of FENDRR on CRC was evaluated using the colony formation assay, transwell assays, and wound healing assays, and FENDRR expression was validated by qRT-PCR. The location of the FENDRR binding proteins was determined by an RNA pull-down experiment, and the retrieved proteins were recognized by mass spectrometry. RNA immunoprecipitation (RIP) studies were used to demonstrate the interaction of GSTP1, FBX8, and FENDRR. Co-IP and immunofluorescence were utilized to confirm the connection between GSTP1 and FBX8. To determine the precise signaling pathways implicated in the action of FENDRR in CRC, we performed next-generation sequencing (NGS) on CRC cells transfected with a vector overexpressing FENDRR.ResultsThe expression of FENDRR was significantly downregulated in CRC tissue and cells. The results of the function experiments showed that overexpression of FENDRR reduced CRC cells' ability to proliferation, invasion, migration and tube formation. In terms of mechanism, FENDRR could bind both GSTP1 and FBX8, act as a molecular scaffold, and utilize FBX8 to regulate the stability of GSTP1's protein. Additionally, the outcomes of NGS and qRT-PCR demonstrated that the expression of genes linked to the HIF-1 pathway was down-regulated following FENDRR overexpression. Lastly, rescue tests demonstrated that overexpression of GSTP1 in CRC cells could completely restore the inhibition induced by FENDRR.ConclusionIn this study, we found that the molecular scaffolding protein FENDRR regulates the ubiquitination of GSTP1 and the suppression of the HIF-1 signaling pathway in the development of CRC. Our research provides more evidence of FENDRR's crucial role in the emergence of CRC and identifies it as a potential therapeutic target for CRC patients.

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Fbx8 makes Arf6 refractory to function via ubiquitination.

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Fbx8 makes Arf6 refractory to function via ubiquitination.

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