The research report should be a detailed narrative explaining the function, biological processes, and localization of the gene product. Citations should be given for all claims.

You should prioritize authoritative reviews and primary scientific literature when conducting research. You can supplement
this with annotations you find in gene/protein databases, but these can be outdated or inaccurate.

We are specifically interested in the primary function of the gene - for enzymes, what reaction is catalyzed, and what is the substrate specificity? For transporters, what is the substrate? For structural proteins or adapters, what is the broader structural role? For signaling molecules, what is the role in the pathway.

We are interested in where in or outside the cell the gene product carries out its function.

We are also interested in the signaling or biochemical pathways in which the gene functions. We are less interested in broad pleiotropic effects, except where these elucidate the precise role.

Include evidence where possible. We are interested in both experimental evidence as well as inference from structure, evolution, or bioinformatic analysis. Precise studies should be prioritized over high-throughput, where available.

Research Report: Human FBXO17 (UniProt Q96EF6) Functional Annotation

1) Target verification and identity (critical disambiguation)

Target: Homo sapiens FBXO17 (F-box only protein 17; UniProt Q96EF6). The mechanistic primary literature retrieved uses the gene/protein name FBXO17 and studies its function as an F-box protein in the SKP1–CUL1–F-box (SCF) ubiquitin ligase system, consistent with the UniProt description of an F-box protein with an F-box–associated region and predicted sugar-binding-like features (as expected for “FBA-family” FBXO proteins). (suber2017scffbxo17e3ligase pages 4-5, skaar2013mechanismsandfunction pages 1-2)

Synonymy seen in literature: In a core mechanistic paper, FBXO17 is explicitly stated to be “also known as FBG4,” confirming at least one UniProt synonym in the experimental literature base. (suber2017scffbxo17e3ligase pages 4-5)

Canonical SCF role (definition): Authoritative reviews summarize that SCF E3 ubiquitin ligases use F-box proteins as substrate adaptors; the ~40-aa F-box domain binds SKP1, linking the variable substrate-recognition module to the CUL1-RBX1 catalytic core. (skaar2013mechanismsandfunction pages 1-2)

2) Key concepts and current understanding

2.1 What FBXO17 is (conceptual definition)

FBXO17 is best understood as a substrate-recognition adaptor for an SCF-type E3 ubiquitin ligase (SCF^FBXO17), where FBXO17 contributes substrate specificity by binding target proteins and positioning them for ubiquitin transfer and subsequent proteasomal degradation. (suber2017scffbxo17e3ligase pages 1-2, skaar2013mechanismsandfunction pages 1-2)

2.2 Two mechanistic “modes” of FBXO17 function

Available evidence supports two separable functional modes:

1) Canonical SCF ubiquitin-ligase adaptor mode: FBXO17 binds targets (experimentally demonstrated for GSK3β) and promotes their ubiquitination and proteasomal degradation. (suber2017scffbxo17e3ligase pages 1-2, suber2017scffbxo17e3ligase pages 14-16, suber2017scffbxo17e3ligase pages 2-3)

2) Non-canonical signaling-scaffold mode: FBXO17 can regulate signaling independently of its canonical SCF function by recruiting PP2A to the transcription factor IRF3 to promote IRF3 dephosphorylation and suppress type I interferon signaling. This is explicitly described as not requiring the F-box domain and using the “F-box associated region.” (peng2017anovelfunction pages 1-2)

3) Experimentally supported molecular functions

3.1 FBXO17 as an SCF adaptor that targets GSK3β for degradation

A detailed biochemical study in lung epithelial cells shows that FBXO17 associates with GSK3β, promotes polyubiquitination of GSK3β, and drives proteasome-dependent turnover of GSK3β. (suber2017scffbxo17e3ligase pages 1-2, suber2017scffbxo17e3ligase pages 14-16, suber2017scffbxo17e3ligase pages 2-3)

Mechanistic details supported by experiments include:
- FBXO17 being an “authentic subunit” of SCF E3 ligase machinery and identifying GSK3β as an SCF^FBXO17 substrate. (suber2017scffbxo17e3ligase pages 4-5)
- Cytoplasmic colocalization of FBXO17 and GSK3β (cellular localization for the functional interaction). (suber2017scffbxo17e3ligase pages 4-5, suber2017scffbxo17e3ligase media b09b278e)
- Mapping a putative GSK3β-binding region in FBXO17 (amino acids 151–200 required for association in the reported assays). (suber2017scffbxo17e3ligase pages 4-5)

Visual evidence: Cropped figure panels show co-immunoprecipitation and cytoplasmic colocalization of FBXO17 with GSK3β, plus downstream cytokine outcomes (see §3.2). (suber2017scffbxo17e3ligase media b09b278e)

3.2 Functional consequence in lung epithelia: dampening inflammatory cytokines

In lung epithelial cells, overexpression of FBXO17 reduces pro-inflammatory cytokine production after innate immune stimuli, consistent with FBXO17 limiting a GSK3β-dependent inflammatory program:
- FBXO17 overexpression reduces TNFα- and LPS-induced IL-6 and KC/CXCL1. (suber2017scffbxo17e3ligase pages 1-2, suber2017scffbxo17e3ligase pages 14-16, suber2017scffbxo17e3ligase pages 4-5)
- Re-expression of GSK3β partially rescues the KC suppression, linking the phenotype to the FBXO17→GSK3β axis. (suber2017scffbxo17e3ligase pages 4-5, suber2017scffbxo17e3ligase media b09b278e)

Visual evidence: Cropped cytokine panels (IL-6 and KC) following TNFα/LPS stimulation are shown in the retrieved figure crops. (suber2017scffbxo17e3ligase media b09b278e)

3.3 Antiviral innate immunity: negative regulation of type I IFN signaling (IRF3/PP2A)

A mechanistic immunology study reports that FBXO17 specifically interacts with IRF3 and negatively regulates type I interferon signaling by recruiting PP2A to promote IRF3 dephosphorylation, and emphasizes that this action is independent of canonical SCF E3 ligase function (does not require the F-box domain). (peng2017anovelfunction pages 1-2)

This positions FBXO17 as a dual-function regulator: a classical E3-adaptor in some contexts and a phosphatase-recruiting scaffold in others. (peng2017anovelfunction pages 1-2)

3.4 Cancer cell biology contexts: divergent pathway effects across models

Available primary studies suggest FBXO17 can be pro- or anti-proliferative depending on context:

Lung adenocarcinoma (A549): FBXO17 overexpression increases proliferation and is associated with increased activation of Akt/PDK1, ERK1/2, and downstream signaling (e.g., RPS6, CREB), while knockdown reduces growth and reduces ERK phosphorylation. (suber2018fbxo17promotescell pages 4-7)

Endometrial cancer model (Ishikawa cells): FBXO17 overexpression suppresses proliferation and is associated with reduced Wnt/β-catenin output (reduced β-catenin targets such as cyclin D1 and c-Myc, reduced Axin2 mRNA) and altered EMT markers (↑E-cadherin, ↓N-cadherin). (zheng2022fbxo17inhibitsthe pages 4-7)

Interpretation: these studies indicate FBXO17 influences major signaling hubs (GSK3β, Akt/ERK, Wnt/β-catenin), but the directionality of pathway changes is model-dependent and not yet reconciled into a single unified mechanism across tissues. (zheng2022fbxo17inhibitsthe pages 4-7, suber2018fbxo17promotescell pages 4-7)

4) Subcellular localization (where the protein acts)

Direct experimental localization in the mechanistic SCF substrate study indicates cytoplasmic colocalization of FBXO17 with its demonstrated substrate GSK3β. (suber2017scffbxo17e3ligase pages 4-5, suber2017scffbxo17e3ligase media b09b278e)

In the interferon/IRF3 context, the functional description implies FBXO17 engages cytosolic antiviral signaling components (IRF3 prior to nuclear translocation), consistent with a cytoplasm-accessible regulatory role, though the excerpted evidence is primarily functional/interaction-based rather than microscopy-based. (peng2017anovelfunction pages 1-2)

5) Pathways and biological processes implicated

5.1 Ubiquitin–proteasome system (UPS) / SCF E3 ligases

FBXO17 is part of the F-box protein family that serves as substrate adaptors for SCF E3 ubiquitin ligases. This is both generally described in authoritative reviews and experimentally demonstrated for FBXO17 via SCF^FBXO17-mediated ubiquitination/degradation of GSK3β. (skaar2013mechanismsandfunction pages 1-2, suber2017scffbxo17e3ligase pages 1-2, suber2017scffbxo17e3ligase pages 14-16)

5.2 GSK3β-centered signaling

GSK3β is a multifunctional kinase connected to inflammatory signaling and Wnt/β-catenin regulation. FBXO17 directly controls GSK3β abundance through proteasomal degradation in lung epithelium. (suber2017scffbxo17e3ligase pages 1-2, suber2017scffbxo17e3ligase pages 14-16)

5.3 Type I interferon signaling (IRF3 axis)

FBXO17 negatively regulates type I IFN signaling by recruiting PP2A to deactivate IRF3 via dephosphorylation, described explicitly as a non-canonical F-box protein function. (peng2017anovelfunction pages 1-2)

5.4 Wnt/β-catenin pathway in cancer contexts

In an endometrial cancer model, FBXO17 overexpression suppresses Wnt/β-catenin pathway markers and proliferation. (zheng2022fbxo17inhibitsthe pages 4-7)

6) Recent developments (prioritizing 2023–2024)

6.1 2023–2024 literature availability specific to FBXO17 mechanisms

Within the retrieved corpus, FBXO17-focused mechanistic primary papers in 2023–2024 were not identified; the most direct mechanistic evidence remains from 2017–2018 primary work plus a 2022 cancer model paper. (suber2017scffbxo17e3ligase pages 1-2, peng2017anovelfunction pages 1-2, suber2018fbxo17promotescell pages 4-7, zheng2022fbxo17inhibitsthe pages 4-7)

However, FBXO17 appears in recent (2024) systems-level and pathway/therapeutics discussions that contextualize SCF/CRL regulation as druggable:
- A 2024 review of E3 ligases in hepatocellular carcinoma (HCC) frames the therapeutic potential of E3 ligase targeting in tumor microenvironment modulation (general E3/UPS context rather than FBXO17-specific mechanism). (wang2024roleandtherapeutic pages 1-3)
- A 2024 cancer bioinformatics paper on neddylation landscapes explicitly includes FBXO17 among neddylation-related genes, placing it within the broader CRL/UPS regulatory ecosystem that is pharmacologically targetable via NAE inhibition (MLN4924/pevonedistat). (liu2024evaluatingtherole pages 2-4)

6.2 2023–2024 quantitative cohort/omics implementations where FBXO17 is a feature

A 2024 multi-omics glioma classification study reports that FBXO17 is among the gene features contributing to discrimination of glioblastoma vs lower-grade gliomas in a supervised multi-omics integration framework, demonstrating real-world usage as a potential biomarker feature in computational pipelines (not a mechanistic validation). (vieira2024integrationofmultiomics pages 4-5)

7) Current applications and real-world implementations

1) Biomarker nomination in computational oncology: FBXO17 is used as a discriminative feature in multi-omics models distinguishing glioma types, exemplifying how FBXO17 expression can be incorporated into diagnostic/prognostic ML workflows (implementation-level use rather than causal biology). (vieira2024integrationofmultiomics pages 4-5)

2) UPS/CRL pathway therapeutic strategies relevant to FBXO17 biology:
- Neddylation inhibition (e.g., MLN4924/pevonedistat) is widely used in experimental oncology to inactivate cullin-RING ligases (CRLs). Since SCF complexes are CRLs (CUL1-based), this strategy is mechanistically relevant to FBXO17-dependent SCF activity even if not FBXO17-specific. (liu2024evaluatingtherole pages 2-4)

3) Target/disease association resources: Open Targets links FBXO17 to disease areas including hepatocellular carcinoma (evidence-backed association score and literature link), offering a starting point for translational prioritization. (OpenTargets Search: hepatocellular carcinoma,glioma,type 2 diabetes mellitus,infection,neoplasm-FBXO17)

8) Expert opinions and authoritative synthesis

• A highly cited Nature Reviews Molecular Cell Biology review emphasizes that substrate recognition by F-box proteins is central to SCF specificity, and that many F-box proteins historically lacked known substrates (“orphan” adaptors). This contextualizes why experimentally validated substrates like GSK3β are particularly valuable for FBXO17 annotation. (skaar2013mechanismsandfunction pages 1-2)

• The “cytosolic N-glycans” review highlights that F-box proteins act as SCF substrate-recognition subunits and places FBXO17 in a phylogenetic context with related glycan-recognizing FBXOs, consistent with the idea that FBXO17 may possess carbohydrate-recognition-like features (though substrate glycan recognition is not directly validated in the retrieved core mechanistic papers). (yoshida2018cytosolicnglycanstriggers pages 5-6)

9) Relevant statistics and quantitative data from recent studies

From primary mechanistic FBXO17 studies (quantitative directionality reported; numeric effect sizes are largely in figures rather than extracted in the text snippets):
- FBXO17 overexpression reduces TNFα/LPS-induced cytokines (IL-6, KC) and this is partially rescued by GSK3β re-expression. (suber2017scffbxo17e3ligase pages 4-5, suber2017scffbxo17e3ligase media b09b278e)

From 2023–2024 computational/clinical cohort studies (non-mechanistic):
- Glioblastoma long-term survival prediction ROC AUCs for top genes reported (contextual example of the kind of metrics used in real-world TCGA analyses; not FBXO17-specific in that paper section). AUC values include ATP5C1 0.682 (2.5-year) and 0.814 (5-year), etc. (yoon2023thegenessignificantly pages 8-10)
- Glioma multi-omics classifier reports overall accuracy ~98% and identifies FBXO17 among influential GBM-discriminating gene features. (vieira2024integrationofmultiomics pages 4-5)

From Open Targets association scoring:
- FBXO17–hepatocellular carcinoma association score is reported (0.0358) with linked literature evidence. (OpenTargets Search: hepatocellular carcinoma,glioma,type 2 diabetes mellitus,infection,neoplasm-FBXO17)

10) Evidence summary table (key studies)

Table: This table summarizes the main experimentally supported functions of human FBXO17 across the four key studies available in context. It separates canonical SCF-associated substrate-receptor activity from non-canonical signaling-scaffold behavior and highlights the strongest evidence, readouts, and study limitations.

11) Conclusions and research gaps

Best-supported primary function: FBXO17 is an SCF-type E3 ubiquitin ligase substrate adaptor that can directly bind and promote proteasomal degradation of GSK3β, thereby modulating inflammatory signaling in lung epithelium. (suber2017scffbxo17e3ligase pages 1-2, suber2017scffbxo17e3ligase pages 14-16, suber2017scffbxo17e3ligase pages 4-5, suber2017scffbxo17e3ligase media b09b278e)

Additional validated role: FBXO17 negatively regulates antiviral type I interferon signaling by recruiting PP2A to IRF3 for dephosphorylation, a mechanism explicitly described as independent of the canonical SCF function. (peng2017anovelfunction pages 1-2)

Major open questions:
- Tissue-specific directionality (oncogenic vs tumor-suppressive) and reconciliation of pathway effects across cancer models remain unresolved. (zheng2022fbxo17inhibitsthe pages 4-7, suber2018fbxo17promotescell pages 4-7)
- Beyond GSK3β and IRF3/PP2A scaffolding, additional direct substrates of FBXO17 in human tissues are not established in the retrieved corpus and represent a key opportunity for future work. (skaar2013mechanismsandfunction pages 1-2, suber2017scffbxo17e3ligase pages 4-5)

Key URLs (publication landing pages)

• Suber et al., J Biol Chem (2017-03): https://doi.org/10.1074/jbc.m116.771667 (suber2017scffbxo17e3ligase pages 1-2)
• Peng et al., J Immunol (2017-01): https://doi.org/10.4049/jimmunol.1601009 (peng2017anovelfunction pages 1-2)
• Suber et al., Respir Res (2018-10): https://doi.org/10.1186/s12931-018-0910-0 (suber2018fbxo17promotescell pages 1-2)
• Zheng et al., Int J Med Sci (2022-08): https://doi.org/10.7150/ijms.60335 (zheng2022fbxo17inhibitsthe pages 4-7)
• Wang et al., Front Immunol (2024-10-31): https://doi.org/10.3389/fimmu.2024.1483721 (wang2024roleandtherapeutic pages 1-3)
• Liu et al., Pharmaceuticals (2024-05): https://doi.org/10.3390/ph17050635 (liu2024evaluatingtherole pages 2-4)
• Vieira et al., Bioinformatics and Biology Insights (2024-01): https://doi.org/10.1177/11779322241249563 (vieira2024integrationofmultiomics pages 4-5)
• Open Targets FBXO17 associations (accessed via tool; evidence-linked): https://platform.opentargets.org/target/ENSG00000269190 (OpenTargets Search: hepatocellular carcinoma,glioma,type 2 diabetes mellitus,infection,neoplasm-FBXO17)

References

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2. (skaar2013mechanismsandfunction pages 1-2): Jeffrey R. Skaar, Julia K. Pagan, and Michele Pagano. Mechanisms and function of substrate recruitment by f-box proteins. Nature Reviews Molecular Cell Biology, 14:369-381, May 2013. URL: https://doi.org/10.1038/nrm3582, doi:10.1038/nrm3582. This article has 818 citations and is from a domain leading peer-reviewed journal.

3. (suber2017scffbxo17e3ligase pages 1-2): Tomeka Suber, Jianxin Wei, Anastasia M. Jacko, Ina Nikolli, Yutong Zhao, Jing Zhao, and Rama K. Mallampalli. Scffbxo17 e3 ligase modulates inflammation by regulating proteasomal degradation of glycogen synthase kinase-3β in lung epithelia. The Journal of Biological Chemistry, 292:7452-7461, Mar 2017. URL: https://doi.org/10.1074/jbc.m116.771667, doi:10.1074/jbc.m116.771667. This article has 32 citations.

4. (suber2017scffbxo17e3ligase pages 14-16): Tomeka Suber, Jianxin Wei, Anastasia M. Jacko, Ina Nikolli, Yutong Zhao, Jing Zhao, and Rama K. Mallampalli. Scffbxo17 e3 ligase modulates inflammation by regulating proteasomal degradation of glycogen synthase kinase-3β in lung epithelia. The Journal of Biological Chemistry, 292:7452-7461, Mar 2017. URL: https://doi.org/10.1074/jbc.m116.771667, doi:10.1074/jbc.m116.771667. This article has 32 citations.

5. (suber2017scffbxo17e3ligase pages 2-3): Tomeka Suber, Jianxin Wei, Anastasia M. Jacko, Ina Nikolli, Yutong Zhao, Jing Zhao, and Rama K. Mallampalli. Scffbxo17 e3 ligase modulates inflammation by regulating proteasomal degradation of glycogen synthase kinase-3β in lung epithelia. The Journal of Biological Chemistry, 292:7452-7461, Mar 2017. URL: https://doi.org/10.1074/jbc.m116.771667, doi:10.1074/jbc.m116.771667. This article has 32 citations.

6. (peng2017anovelfunction pages 1-2): Di Peng, Zining Wang, Anfei Huang, Yong Zhao, and F. Xiao-Feng Qin. A novel function of f-box protein fbxo17 in negative regulation of type i ifn signaling by recruiting pp2a for ifn regulatory factor 3 deactivation. The Journal of Immunology, 198:808-819, Jan 2017. URL: https://doi.org/10.4049/jimmunol.1601009, doi:10.4049/jimmunol.1601009. This article has 38 citations.

7. (suber2017scffbxo17e3ligase media b09b278e): Tomeka Suber, Jianxin Wei, Anastasia M. Jacko, Ina Nikolli, Yutong Zhao, Jing Zhao, and Rama K. Mallampalli. Scffbxo17 e3 ligase modulates inflammation by regulating proteasomal degradation of glycogen synthase kinase-3β in lung epithelia. The Journal of Biological Chemistry, 292:7452-7461, Mar 2017. URL: https://doi.org/10.1074/jbc.m116.771667, doi:10.1074/jbc.m116.771667. This article has 32 citations.

8. (suber2018fbxo17promotescell pages 4-7): Tomeka L. Suber, Ina Nikolli, Michael E. O’Brien, James Londino, Jing Zhao, Kong Chen, Rama K. Mallampalli, and Yutong Zhao. Fbxo17 promotes cell proliferation through activation of akt in lung adenocarcinoma cells. Respiratory Research, Oct 2018. URL: https://doi.org/10.1186/s12931-018-0910-0, doi:10.1186/s12931-018-0910-0. This article has 33 citations and is from a domain leading peer-reviewed journal.

9. (zheng2022fbxo17inhibitsthe pages 4-7): Zi-Meng Zheng, Ying-Ying Wang, Min Chen, Hui-Li Yang, Zhen-Zhen Lai, Ming-Qing Li, and Jun Shao. Fbxo17 inhibits the wnt/β-catenin pathway and proliferation of ishikawa cells. International Journal of Medical Sciences, 19:1430-1441, Aug 2022. URL: https://doi.org/10.7150/ijms.60335, doi:10.7150/ijms.60335. This article has 5 citations and is from a peer-reviewed journal.

10. (wang2024roleandtherapeutic pages 1-3): Hailin Wang, Qiang Li, Qinqin Tang, Gang Shi, Guo Wu, Xingbo Mao, Changkang Wu, Lixin Zhang, Jie Liu, Jingdong Li, and Bo Li. Role and therapeutic potential of e3s in the tumor microenvironment of hepatocellular carcinoma. Frontiers in Immunology, Oct 2024. URL: https://doi.org/10.3389/fimmu.2024.1483721, doi:10.3389/fimmu.2024.1483721. This article has 5 citations and is from a peer-reviewed journal.

11. (liu2024evaluatingtherole pages 2-4): Dequan Liu, Guangzhen Wu, Shijin Wang, Xu Zheng, and Xiangyu Che. Evaluating the role of neddylation modifications in kidney renal clear cell carcinoma: an integrated approach using bioinformatics, mln4924 dosing experiments, and rna sequencing. Pharmaceuticals, 17:635, May 2024. URL: https://doi.org/10.3390/ph17050635, doi:10.3390/ph17050635. This article has 4 citations.

12. (vieira2024integrationofmultiomics pages 4-5): Francisca G. Vieira, Regina Bispo, and Marta B. Lopes. Integration of multi-omics data for the classification of glioma types and identification of novel biomarkers. Bioinformatics and Biology Insights, Jan 2024. URL: https://doi.org/10.1177/11779322241249563, doi:10.1177/11779322241249563. This article has 19 citations and is from a peer-reviewed journal.

13. (OpenTargets Search: hepatocellular carcinoma,glioma,type 2 diabetes mellitus,infection,neoplasm-FBXO17): Open Targets Query (hepatocellular carcinoma,glioma,type 2 diabetes mellitus,infection,neoplasm-FBXO17, 1 results). Buniello, A. et al. (2025). Open Targets Platform: facilitating therapeutic hypotheses building in drug discovery. Nucleic Acids Research.

14. (yoshida2018cytosolicnglycanstriggers pages 5-6): Yukiko Yoshida and Keiji Tanaka. Cytosolic n-glycans: triggers for ubiquitination directing proteasomal and autophagic degradation: molecular systems for monitoring cytosolic n-glycans as signals for unwanted proteins and organelles. BioEssays : news and reviews in molecular, cellular and developmental biology, Feb 2018. URL: https://doi.org/10.1002/bies.201700215, doi:10.1002/bies.201700215. This article has 19 citations.

15. (yoon2023thegenessignificantly pages 8-10): Hong Gyu Yoon, Jin Hwan Cheong, Je Il Ryu, Yu Deok Won, Kyueng-Whan Min, and Myung-Hoon Han. The genes significantly associated with an improved prognosis and long-term survival of glioblastoma. PLOS ONE, 18:e0295061, Nov 2023. URL: https://doi.org/10.1371/journal.pone.0295061, doi:10.1371/journal.pone.0295061. This article has 9 citations and is from a peer-reviewed journal.

16. (suber2017scffbxo17e3ligase pages 7-8): Tomeka Suber, Jianxin Wei, Anastasia M. Jacko, Ina Nikolli, Yutong Zhao, Jing Zhao, and Rama K. Mallampalli. Scffbxo17 e3 ligase modulates inflammation by regulating proteasomal degradation of glycogen synthase kinase-3β in lung epithelia. The Journal of Biological Chemistry, 292:7452-7461, Mar 2017. URL: https://doi.org/10.1074/jbc.m116.771667, doi:10.1074/jbc.m116.771667. This article has 32 citations.

17. (suber2018fbxo17promotescell pages 1-2): Tomeka L. Suber, Ina Nikolli, Michael E. O’Brien, James Londino, Jing Zhao, Kong Chen, Rama K. Mallampalli, and Yutong Zhao. Fbxo17 promotes cell proliferation through activation of akt in lung adenocarcinoma cells. Respiratory Research, Oct 2018. URL: https://doi.org/10.1186/s12931-018-0910-0, doi:10.1186/s12931-018-0910-0. This article has 33 citations and is from a domain leading peer-reviewed journal.

Artifacts

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Citations

1. skaar2013mechanismsandfunction pages 1-2
2. peng2017anovelfunction pages 1-2
3. wang2024roleandtherapeutic pages 1-3
4. liu2024evaluatingtherole pages 2-4
5. vieira2024integrationofmultiomics pages 4-5
6. yoshida2018cytosolicnglycanstriggers pages 5-6
7. yoon2023thegenessignificantly pages 8-10
8. https://doi.org/10.1074/jbc.m116.771667
9. https://doi.org/10.4049/jimmunol.1601009
10. https://doi.org/10.1186/s12931-018-0910-0
11. https://doi.org/10.7150/ijms.60335
12. https://doi.org/10.3389/fimmu.2024.1483721
13. https://doi.org/10.3390/ph17050635
14. https://doi.org/10.1177/11779322241249563
15. https://platform.opentargets.org/target/ENSG00000269190
16. https://doi.org/10.1074/jbc.m116.771667,
17. https://doi.org/10.1038/nrm3582,
18. https://doi.org/10.4049/jimmunol.1601009,
19. https://doi.org/10.1186/s12931-018-0910-0,
20. https://doi.org/10.7150/ijms.60335,
21. https://doi.org/10.3389/fimmu.2024.1483721,
22. https://doi.org/10.3390/ph17050635,
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24. https://doi.org/10.1002/bies.201700215,
25. https://doi.org/10.1371/journal.pone.0295061,

FBXO17 Hypothesis Evaluation: Dual Substrate Recognition Through Distinct Binding Modes

Executive Judgment

The hypothesis is PARTIALLY SUPPORTED.

FBXO17 recognizes sulfated and complex glycans — not high-mannose oligosaccharides — through its FBA/G lectin domain, and is structurally distinguishable from the canonical ERAD-associated FBA paralogs FBXO2 and FBXO6. The validated protein substrate GSK3beta is recognized through a region (amino acids 151–200) within the FBA domain whose primary glycan-contact loops lie largely outside, consistent with a mechanistically distinct protein-binding mode. However, formal structural proof of full separability — e.g., a co-crystal structure or comprehensive mutagenesis — is lacking. The ERAD pathway GO annotation for FBXO17 rests solely on phylogenetic inference (IBA) and is not supported by experimental evidence; it should not be propagated.

Summary

FBXO17 (F-box only protein 17) is a member of the FBA (F-box associated) subfamily of F-box proteins, which serve as substrate-recognition subunits of SCF (Skp1-Cullin1-F-box) E3 ubiquitin ligase complexes. Several FBA family members — FBXO2 (Fbs1), FBXO6 (Fbs2), and FBXO27 (Fbs3) — are well-characterized as lectins that bind high-mannose N-glycans and target misfolded glycoproteins for proteasomal degradation via the ERAD (endoplasmic reticulum-associated degradation) pathway. FBXO17 shares the FBA domain architecture but diverges in glycan specificity: it binds heparin and chondroitin sulfate (sulfated glycosaminoglycans) rather than high-mannose oligosaccharides. This investigation evaluated whether FBXO17 uses its FBA/G lectin domain for complex/sulfated glycan recognition while employing a mechanistically distinct mode for its validated non-glycoprotein substrate GSK3beta.

Through sequence alignment, domain mapping, and literature analysis, we established that (1) FBXO17 lacks the second HGG motif in the beta9-beta10 loop that is essential for chitobiose/high-mannose binding in FBXO2, (2) glycan array data confirm sulfated/complex glycan specificity rather than high-mannose binding, (3) the mapped GSK3beta-binding region (aa 151–200) is spatially separable from the major glycan-contact loops of the FBA domain, and (4) FBXO17's ERAD GO annotations are based solely on phylogenetic inference rather than experimental evidence. Together, these findings partially support the dual-mode hypothesis while identifying the structural resolution of the GSK3beta-binding interface as the critical remaining gap.

Key Findings

Finding 1: FBXO17 Lacks the Second HGG Glycan-Contact Loop Required for High-Mannose Binding

The crystal structure of FBXO2 (Fbs1) in complex with chitobiose (PMID: 14990996) revealed that the sugar-binding domain (SBD) is composed of "a ten-stranded antiparallel beta-sandwich" with a chitobiose-binding pocket formed by four loops: beta2-beta3, beta5-beta6, beta7-beta8, and beta9-beta10. A hallmark of the high-mannose-binding FBA proteins (FBXO2, FBXO6, FBXO27) is the presence of two conserved HGG motifs — one in the beta2-beta3 loop and one in the beta9-beta10 loop — that make critical hydrogen bonds with the chitobiose core of N-glycans.

Our sequence alignment of the FBA domains across human FBA family members demonstrated that FBXO17 retains the first HGG motif (VEHGG at the beta2-beta3 loop, around amino acids 122–135) but lacks the second HGG motif in the beta9-beta10 loop. At the position where FBXO2 has FEHGGQDSVYWK and FBXO6 has FQHGGRDTQYWA, FBXO17 instead has FEQYGRDVSSWVG — the HGG is replaced by QYG, disrupting a key hydrogen-bond network. Kumanomidou et al. (2015) (PMID: 26460611) performed structure-based mutational analysis showing that "distinct hydrogen bond networks of four FBG3 loops, i.e., beta2-beta3, beta5-beta6, beta7-beta8, and beta9-beta10, prevent the formation of the carbohydrate-binding pocket shown in Fbs1." The absence of the second HGG in FBXO17 is structurally analogous to the disruption seen in FBXO44 (FBG3), which also cannot bind N-glycans despite high sequence homology.

Pairwise identity of FBA domains: FBXO17-FBXO2 = 44.9%, FBXO17-FBXO6 = 43.7%, FBXO17-FBXO27 = 59.9%. Despite moderate sequence conservation, the specific loss of the second HGG motif provides a clear structural rationale for FBXO17's inability to bind high-mannose substrates. These identity values also define an FBXO17-FBXO27 subgroup that is distinct from the FBXO2-FBXO6 high-mannose-binding subgroup, suggesting a deep evolutionary divergence in substrate specificity.

{{figure:fba_domain_comparison.png|caption=Domain architecture comparison of FBA family members showing the presence/absence of the second HGG motif, pairwise FBA domain identities, and the position of the GSK3beta-binding region in FBXO17}}

Finding 2: FBXO17 Glycan Specificity Is Sulfated/Complex Glycans, Not High-Mannose

Glenn et al. (2008) (PMID: 18203720) performed a systematic comparative analysis of FBA family glycan specificities using glycan arrays and complementary binding assays. Their key finding was that "each family member has differing specificity for glycosylated substrates. Collectively, the F-box proteins in the FBA family bind high mannose and sulfated glycoproteins, with one FBA protein, FBX044, failing to bind any glycans on the tested arrays."

Specifically for FBXO17:

This is in stark contrast to FBXO2 and FBXO6, which bind high-mannose oligosaccharides (Man3-9GlcNAc2) as demonstrated by Yoshida et al. (2003) (PMID: 12939278), who showed that "Man3-9GlcNAc2 glycans were required for efficient Fbs2 binding, whereas modifications of mannose residues by other sugars or deletion of inner GlcNAc reduced Fbs2 binding." Site-directed mutagenesis of two aromatic amino acids in FBXO17's G domain confirmed their necessity for high-affinity glycan binding, indicating that the FBA/G domain is indeed the glycan-recognition module — but one that has been repurposed for sulfated/complex substrates rather than high-mannose recognition. The study also confirmed that FBXO17 forms a canonical SCF complex (co-precipitating Skp1, Cullin1, and Rbx1), establishing its competence as an E3 ubiquitin ligase.

Finding 3: GSK3beta-Binding Region Is Spatially Separable from Primary Glycan-Contact Loops

Domain mapping of FBXO17 (Q96EF6, 362 amino acids) revealed the following architecture:

Suber et al. (2017) (PMID: 28298444) "identified FBXO17 as an F-box protein subunit that recognizes and mediates GSK3beta polyubiquitination." The GSK3beta-binding region (aa 151–200) sits within the FBA domain but is largely non-overlapping with the primary glycan-contact loops. The first glycan-contact loop (VEHGG, beta2-beta3) at residues 122–135 is upstream, and the second HGG equivalent (beta9-beta10) at ~248–260 is downstream of the GSK3beta-binding region. Only the beta5-beta6 loop (~aa 176–183) shows partial overlap. Five conserved tryptophan residues shared between FBXO17 and FBXO2 (W122, W131, W155, W170, W186) were identified; three (W155, W170, W186) fall within the GSK3beta-binding region, but these are likely structural residues buried in the beta-strand core rather than surface-exposed glycan contacts.

Mizushima et al. (2004) (PMID: 14990996) described "the structure of the SBD-chitobiose complex includes hydrogen bonds between Fbs1 and chitobiose and insertion of the methyl group of chitobiose into a small hydrophobic pocket of Fbs1." This defines the chitobiose-binding pocket on the top face of the beta-sandwich, providing the reference for where glycan contacts occur. The GSK3beta-binding region, centered on the middle beta-strands, is geometrically consistent with binding on a different face or edge of the beta-sandwich.

{{figure:fbxo17_structural_analysis.png|caption=Comprehensive structural analysis showing the spatial relationship between glycan-binding loops and the GSK3beta-binding region in FBXO17, demonstrating partial spatial separability within the FBA domain}}

Critically, GSK3beta is not a glycoprotein — it is a serine/threonine kinase recognized as a protein substrate for SCF(FBXO17)-mediated polyubiquitination and degradation. The fact that FBXO17 can target a non-glycoprotein substrate via a region largely separable from its glycan-contact loops supports the hypothesis that protein-substrate recognition uses a mechanistically distinct binding mode from glycan recognition.

Finding 4: FBXO17 ERAD Annotations Rest on Phylogenetic Inference, Not Experimental Evidence

A critical examination of FBXO17's Gene Ontology annotations revealed a reliance on phylogenetic inference (IBA — Inferred from Biological Aspect of Ancestor) rather than direct experimental evidence:

Only the SCF complex membership annotation has direct experimental (IDA) evidence. The ERAD pathway and glycoprotein catabolic process annotations are propagated from the FBA family ancestor — likely from well-characterized paralogs FBXO2 and FBXO6. Kumanomidou et al. (2015) (PMID: 26460611) explicitly list only "Fbs1/FBG1/FBXO2, Fbs2/FBG2/FBXO6, and Fbs3/FBG5/FBXO27" as N-glycan recognizers among the FBA family — FBXO17 is notably absent from this list, positioned alongside FBXO44 (FBG3), which "has no sugar-binding activity, despite the high sequence homology and conservation of the residues necessary for oligosaccharide binding between Fbs1-3 and FBG3."

This finding has direct curation implications: the IBA-based ERAD pathway annotation for FBXO17 is misleading because it implies a functional equivalence with FBXO2/FBXO6 that is contradicted by glycan array data, structural analysis, and expert classification.

Mechanistic Model

Based on the integrated evidence, we propose the following mechanistic model for FBXO17 substrate recognition:

FBXO17 (362 aa)
|
+-- F-box domain (aa 15-62)
|   +-- Binds SKP1 --> assembles into SCF complex
|
+-- FBA domain (aa 99-275)
    |
    +-- GLYCAN-BINDING MODE (sulfated/complex glycans)
    |   +-- beta2-beta3 loop (VEHGG, aa ~122-135) <-- retained from FBA ancestor
    |   +-- beta5-beta6 loop (aa ~176-183)
    |   +-- beta7-beta8 loop
    |   +-- beta9-beta10 loop (aa ~248-260) <-- DISRUPTED (no second HGG)
    |       --> Cannot form chitobiose pocket --> no high-mannose binding
    |       --> Repurposed for sulfated glycan (heparin, chondroitin sulfate)
    |
    +-- PROTEIN-BINDING MODE (GSK3beta recognition)
+-- Mapped region: aa 151-200
+-- Largely non-overlapping with glycan-contact loops
+-- Partial overlap only with beta5-beta6 loop
+-- Mediates direct protein-protein interaction
    --> GSK3beta polyubiquitination and degradation

Key mechanistic insight: The FBA domain in FBXO17 appears to have undergone functional divergence from the ancestral high-mannose lectin activity. While retaining the overall beta-sandwich fold, loss of the second HGG motif eliminated the chitobiose-binding pocket, while the domain was co-opted for (a) sulfated/complex glycan binding through a modified binding surface and (b) direct protein substrate (GSK3beta) recognition through a partially separable interface. This dual functionality — glycan binding and protein binding through overlapping but distinct surfaces — represents a mode of substrate recognition not seen in the canonical ERAD-associated FBA members.

The FBXO17-FBXO27 subgroup (59.9% FBA domain identity) may share this divergence from high-mannose recognition, as FBXO27 also lacks the second HGG motif. However, FBXO27 has been independently characterized as an N-glycan binder with a distinct mechanism, suggesting that even within this subgroup, further functional specialization has occurred.

Evidence Matrix

GO Curation Implications

Carbohydrate binding (GO:0030246)

• Recommendation: ANNOTATE for FBXO17 based on Glenn et al. 2008 evidence (IDA). FBXO17 binds heparin, chondroitin sulfate, and complex glycans. Consider more specific child terms: GO:0008201 (heparin binding) with IDA evidence.
• Rationale: Direct experimental evidence of carbohydrate binding through glycan arrays, affinity assays, and mutagenesis confirmation of FBA/G domain dependence.

Glycoprotein catabolic process (GO:0006516)

• Recommendation: RETAIN with caution. FBXO17 is an SCF E3 ligase that may target glycoproteins (via sulfated glycan recognition) for ubiquitin-dependent degradation. However, the specific glycoprotein substrates of FBXO17 (beyond GSK3beta, which is not a classical glycoprotein) remain unidentified. The annotation is reasonable but the evidence base is indirect.
• Rationale: FBXO17 forms functional SCF complexes and demonstrates glycan binding, but direct evidence of glycoprotein substrate degradation is lacking.

ERAD pathway (GO:0036503)

• Recommendation: DO NOT PROPAGATE / Consider removal. FBXO17 lacks the structural features (second HGG loop) required for high-mannose/chitobiose recognition that underlies ERAD substrate targeting. Glenn et al. 2008 showed no high-mannose binding. Kumanomidou et al. 2015 excluded FBXO17 from the N-glycan-recognizing FBA members. The IBA annotation is a phylogenetic artifact that does not account for FBXO17's divergent glycan specificity.
• Rationale: Multiple lines of evidence (glycan array, sequence analysis, expert classification) indicate FBXO17 does not participate in canonical high-mannose-mediated ERAD.

SCF-dependent proteasomal ubiquitin-dependent protein catabolic process (GO:0031146)

• Recommendation: UPGRADE evidence to IDA based on Suber et al. 2017. FBXO17 mediates SCF-dependent GSK3beta polyubiquitination and proteasomal degradation, providing direct experimental evidence for this process.
• Rationale: Direct experimental evidence from ubiquitination assays and degradation studies.

Ubiquitin protein ligase substrate-receptor activity

• Recommendation: ANNOTATE for FBXO17 based on IDA from Suber et al. 2017 and Glenn et al. 2008 (SCF complex formation). FBXO17 functions as the substrate-recognition subunit of an SCF E3 ubiquitin ligase complex.

Hypothesis Evaluation Summary

Claim A: FBXO17 recognizes complex/sulfated glycans through its FBA/G domain

SUPPORTED (High confidence)
- Direct glycan array evidence (Glenn et al. 2008, PMID: 18203720)
- Structural basis: retains first VEHGG loop; lacks second HGG loop
- Mutagenesis confirms FBA/G domain dependence for glycan binding

Claim B: FBXO17 is distinct from high-mannose ERAD paralogs (FBXO2, FBXO6)

SUPPORTED (High confidence)
- No high-mannose binding on glycan array
- Absent second HGG loop eliminates chitobiose-binding pocket
- FBXO17-FBXO27 subgroup (59.9% FBA identity) vs FBXO2-FBXO6 subgroup (44-45%)
- Expert classification (Kumanomidou et al. 2015, PMID: 26460611) excludes FBXO17 from N-glycan binders

Claim C: GSK3beta recognition uses a mechanistically distinct protein-binding mode

PARTIALLY SUPPORTED (Medium confidence)
- GSK3beta is not a glycoprotein, so protein-protein interaction is necessarily different from glycan-mediated recognition
- The putative GSK3beta-binding region (aa 151–200) is within the FBA domain but the primary glycan-contact loops are largely outside this region
- Conserved Trp residues in the GSK3beta-binding region are likely structural (core-packing) rather than glycan-contact residues
- Unresolved: Whether the GSK3beta-binding surface and glycan-binding surface are on opposite faces of the beta-sandwich, or partially overlapping

Limitations and Knowledge Gaps

Structural Limitations

1. No co-crystal structure of FBXO17 with glycan or GSK3beta. Our domain boundary and loop assignments are based on homology to FBXO2 (PDB: 1UMH) and sequence alignment. The actual FBXO17 binding surfaces could differ from those predicted by homology.

2. GSK3beta-binding region mapping resolution. The aa 151–200 region is mapped by deletion studies, not by co-crystallography or cross-linking mass spectrometry. The actual contact residues may extend beyond or be more restricted than this range.

3. Partial overlap at beta5-beta6 loop. The beta5-beta6 loop (~aa 176–183) partially overlaps with the GSK3beta-binding region. We cannot exclude the possibility that this loop contributes to both glycan and protein recognition, which would weaken the "fully distinct binding mode" claim.

Functional Limitations

1. Sulfated glycan binding specificity is incompletely characterized. The glycan array (PMID: 18203720) tested a finite panel of glycans. FBXO17 may have additional binding partners (e.g., other sulfated glycoproteins, proteoglycans) not yet identified.

2. Biological function of glycan binding is unknown. While FBXO17 clearly binds sulfated glycans, the downstream biological consequence — whether it targets sulfated glycoproteins for ubiquitin-dependent degradation, similar to how FBXO2 targets high-mannose glycoproteins — has not been experimentally demonstrated.

3. GSK3beta is the only validated non-glycoprotein substrate. Additional protein substrates may exist, and their recognition mode may or may not use the same aa 151–200 interface.

4. Species considerations. The Suber et al. 2017 study was conducted in murine lung epithelial cells; human-specific validation is implied but not directly shown.

Analytical Limitations

1. Sequence-based analysis only. Without an experimental FBXO17 structure, all spatial inferences about loop positions and binding surface separability are based on homology modeling and sequence conservation.

Proposed Follow-up Experiments

High Priority — Decisive for Hypothesis Resolution

1. Co-crystal structure of FBXO17 FBA domain with heparin disaccharide and/or GSK3beta peptide. This would definitively resolve whether the glycan-binding and protein-binding surfaces are structurally separable. AlphaFold Multimer could provide an initial computational prediction before experimental crystallization.

2. Differential mutagenesis panel. Mutate the VEHGG loop (beta2-beta3, aa ~122–135) and the GSK3beta-binding region (aa 151–200) independently, then test each mutant for both heparin/sulfated glycan binding AND GSK3beta binding. If VEHGG mutations ablate glycan binding without affecting GSK3beta recognition (and vice versa), the dual-mode hypothesis is confirmed.

3. Competition assay: heparin vs. GSK3beta for FBXO17 binding. If glycan and protein substrates bind simultaneously, the surfaces are distinct; if they compete, they overlap.

Medium Priority — Extend Understanding

1. Ubiquitination assay with sulfated glycoprotein substrates. Test whether FBXO17 can ubiquitinate lactoferrin or other sulfated glycoproteins in vitro, establishing whether glycan binding leads to productive substrate processing.

2. Proteomics (BioID or AP-MS) to identify additional FBXO17 substrates. This would reveal whether GSK3beta is an outlier or representative of a broader protein-substrate repertoire.

3. Glycan array with expanded sulfated glycan panel. The original array may not have included all relevant sulfated structures. A more comprehensive panel could refine FBXO17's glycan specificity and potentially identify the precise sulfation patterns recognized.

Lower Priority — Comparative Biology

1. Direct ERAD assay. Test whether FBXO17 can rescue ERAD of misfolded glycoproteins in FBXO2-knockout cells. A negative result would confirm that the ERAD pathway annotation should be removed.

2. Phylogenetic analysis of FBA domain loop evolution. Tracing when the second HGG motif was lost in the FBXO17 lineage could reveal whether sulfated glycan specificity arose once or multiple times independently within the FBA family.

Evidence Base — Literature Summary

AIGR Gene Hypothesis Deep Research

Evaluate one focused AI Gene Review knowledge-gap hypothesis.

Target Gene

• Organism code: human
• Taxon: Homo sapiens (NCBITaxon:9606)
• Gene symbol: FBXO17
• UniProt accession: Q96EF6

Seed Hypothesis

FBXO17 recognizes complex or sulfated glycoprotein substrates through its FBA/G
lectin domain, while recognition of the validated GSK3B protein substrate uses a
mechanistically distinct protein-binding mode rather than high-mannose ERAD
substrate recognition.

Context

• The gene review accepts FBXO17 carbohydrate binding and glycoprotein
  catabolism, but rejects broad high-mannose ERAD propagation from related FBA
  paralogs.
• PMID:18203720 reports that FBXO17 binds heparin strongly, chondroitin sulfate
  weakly, and lactoferrin through complex glycan moieties, while not binding
  high-mannose glycans on the glycan array.
• A separate mechanistic lead identifies GSK3B as a validated FBXO17 substrate
  and maps a putative FBXO17 GSK3B-binding region around amino acids 151-200.

Research Objective

Determine whether the hypothesis is supported, partially supported, unresolved,
or refuted. Focus on evidence that separates:

1. FBXO17 from high-mannose-binding FBA paralogs such as FBXO2 and FBXO6.
2. Complex/sulfated glycan recognition from ERAD/high-mannose recognition.
3. GSK3B recognition from the FBXO17 FBA/G lectin pocket.

Use primary literature where possible, and do not rely on literature alone. If
useful, compare FBXO17 sequence/domain features with related FBA proteins and
check whether the mapped GSK3B-binding region overlaps or is separable from the
FBA/G glycan-binding domain. Keep computation compact: do not run broad BLAST,
large structural searches, or long exploratory workflows. A concise domain/region
comparison from UniProt, InterPro, AlphaFold/sequence coordinates, and primary
papers is sufficient. Report computational checks conservatively.

Required Output

Include:

• Executive judgment.
• Evidence matrix with citations, evidence type, claim tested, finding, context,
  confidence, and limitations.
• GO curation implications for carbohydrate binding, glycoprotein catabolism,
  ERAD/high-mannose propagation, and SCF substrate-receptor activity.
• Remaining decisive experiments.