Dataset Information

The pseudophosphatase STYX targets the F-box of FBXW7 and inhibits SCFFBXW7 function.

ABSTRACT: The F-box protein FBXW7 is the substrate-recruiting subunit of an SCF ubiquitin ligase and a major tumor-suppressor protein that is altered in several human malignancies. Loss of function of FBXW7 results in the stabilization of numerous proteins that orchestrate cell proliferation and survival. Little is known about proteins that directly regulate the function of this protein. In the current work, we have mapped the interactome of the enigmatic pseudophosphatase STYX We reasoned that a catalytically inactive phosphatase might have adopted novel mechanisms of action. The STYX interactome contained several F-box proteins, including FBXW7. We show that STYX binds to the F-box domain of FBXW7 and disables its recruitment into the SCF complex. Therefore, STYX acts as a direct inhibitor of FBXW7, affecting the cellular levels of its substrates. Furthermore, we find that levels of STYX and FBXW7 are anti-correlated in breast cancer patients, which affects disease prognosis. We propose the STYX-FBXW7 interaction as a promising drug target for future investigations.

SUBMITTER: Reiterer V

PROVIDER: S-EPMC5286380 | biostudies-literature | 2017 Feb

REPOSITORIES: biostudies-literature

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The pseudophosphatase STYX targets the F-box of FBXW7 and inhibits SCFFBXW7 function.

Reiterer Veronika V Figueras-Puig Cristina C Le Guerroue Francois F Confalonieri Stefano S Vecchi Manuela M Jalapothu Dasaradha D Kanse Sandip M SM Deshaies Raymond J RJ Di Fiore Pier Paolo PP Behrends Christian C Farhan Hesso H

The EMBO journal 20161222 3

The F-box protein FBXW7 is the substrate-recruiting subunit of an SCF ubiquitin ligase and a major tumor-suppressor protein that is altered in several human malignancies. Loss of function of FBXW7 results in the stabilization of numerous proteins that orchestrate cell proliferation and survival. Little is known about proteins that directly regulate the function of this protein. In the current work, we have mapped the interactome of the enigmatic pseudophosphatase STYX We reasoned that a catalyti ...[more]

PMID: 28007894

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Project description:The dual specificity phosphatase (DUSP) family has catalytically inactive members, called pseudophosphatases. They have mutations in their catalytic motifs that render them enzymatically inactive. This study analyzes the significance of two pseudophosphatases, MK-STYX [MAPK (mitogen-activated protein kinase phosphoserine/threonine/tyrosine-binding protein]) and STYX (serine/threonine/tyrosine-interacting protein), throughout their evolution and provides measurements and comparison of their evolutionary conservation. Phylogenetic trees were constructed to show any deviation from various species evolutionary paths. Data was collected on a large set of proteins that have either one of the two domains of MK-STYX, the DUSP domain or the cdc-25 homology (CH2) /rhodanese-like domain. The distance between species pairs for MK-STYX or STYX and Ka/Ks ratio were calculated. In addition, both pseudophosphatases were ranked among a large set of related proteins, including the active homologs of MK-STYX, MKP (MAPK phosphatase)-1 and MKP-3. MK-STYX had one of the highest species-species protein distances and was under weaker purifying selection pressure than most proteins with its domains. In contrast, the protein distances of STYX were lower than 82% of the DUSP-containing proteins and was under one of the strongest purifying selection pressures. However, there was similar selection pressure on the N-terminal sequences of MK-STYX, STYX, MKP-1, and MKP-3. We next perform statistical coupling analysis, a process that reveals interconnected regions within the proteins. We find that while MKP-1,-3, and STYX all have 2 functional units (sectors), MK-STYX only has one, and that MK-STYX is similar to MKP-3 in the evolutionary coupling of the active site and KIM domain. Within those two domains, the mean coupling is also most similar for MK-STYX and MKP-3. This study reveals striking distinctions between the evolutionary patterns of MK-STYX and STYX, suggesting a very specific role for each pseudophosphatase, further highlighting the relevance of these atypical members of DUSP as signaling regulators. Therefore, our study provides computational evidence and evolutionary reasons to further explore the properties of pseudophosphatases, in particular MK-STYX and STYX.

Project description:IntroductionGlioblastoma (GBM) is a highly aggressive and lethal primary brain tumor. Despite limited treatment options, the overall survival of GBM patients has shown minimal improvement over the past two decades. Factors such as delayed cancer diagnosis, tumor heterogeneity, cancer stem cell survival, infiltrative nature of GBM cells, metabolic reprogramming, and development of therapy resistance contribute to treatment failure. To address these challenges, multitargeted therapies are urgently needed for improved GBM treatment outcomes. MicroRNAs (miRNAs) are small non-coding RNAs that regulate gene expression. Dysregulated miRNAs have been identified in GBM, playing roles in tumor initiation, progression, and maintenance. Among these miRNAs, miR-92b (miRNA-92b-3p) has been found to be overexpressed in various cancers, including GBM. However, the specific target genes of miR-92b and its therapeutic potential in GBM remain poorly explored.MethodsSamples encompassed T98G, U87, and A172 human GBM cell lines, GBM tumors from Puerto Rican patients, and murine tumors. In-situ hybridization (ISH) assessed miR-92b expression in patient tumors. Transient and stable transfections modified miR-92b levels in GBM cell lines. Real-time PCR gauged gene expressions. Caspase 3 and Trypan Blue assays evaluated apoptosis and viability. Bioinformatics tools (TargetScanHuman 8.0, miRDB, Diana tools, miRWalk) predicted targets. Luciferase assays and Western Blots validated miRNA-target interactions. A subcutaneous GBM Xenograft mouse model received intraperitoneal NC-OMIs or miR92b-OMIs encapsulated in liposomes, three-times per week for two weeks. Analysis utilized GraphPad Prism 8; statistical significance was assessed using 2-tailed, unpaired Student's t-test and two-way ANOVA as required.ResultsThis study investigated the expression of miR-92b in GBM tumors compared to normal brain tissue samples, revealing a significant upregulation. Inhibition of miR-92b using oligonucleotide microRNA inhibitors (OMIs) suppressed GBM cell growth, migration, and induced apoptosis, while ectopic expression of miR-92b yielded opposite effects. Systemic administration of liposomal-miR92b-OMIs in GBM xenograft mice resulted in reductions in tumor volume and weight. Subsequent experiments identified F-Box and WD Repeat Domain Containing 7 (FBXW7) as a direct target gene of miR-92b in GBM cells.DiscussionFBXW7 acts as a tumor suppressor gene in various cancer types, and analysis of patient data demonstrated that GBM patients with higher FBXW7 mRNA levels had significantly better overall survival compared to those with lower levels. Taken together, our findings suggest that the dysregulated expression of miR-92b in GBM contributes to tumor progression by targeting FBXW7. These results highlight the potential of miR-92b as a therapeutic target for GBM. Further exploration and development of miR-92b-targeted therapies may offer a novel approach to improve treatment outcomes in GBM patients.

Dataset Information

The pseudophosphatase STYX targets the F-box of FBXW7 and inhibits SCFFBXW7 function.

Publications

The pseudophosphatase STYX targets the F-box of FBXW7 and inhibits SCFFBXW7 function.

Similar Datasets

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