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this with annotations you find in gene/protein databases, but these can be outdated or inaccurate.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.
Target confirmed: The symbol FBXW12 corresponds to human F-box/WD repeat-containing protein 12, and is explicitly mapped to UniProt Q6X9E4 in an interactome resource table that annotates the protein as an E3 Cullin-RING ligase (CRL) adaptor with F-box and WD-repeat (WD40) domains—consistent with the user-provided UniProt description. (poirson2017mappingtheinteractome pages 23-23, poirson2017mappingtheinteractome media 39749cd6)
Why this matters: F-box proteins are substrate-recognition subunits of SCF-type CRLs (SKP1–CUL1–F-box), and WD40 repeats commonly mediate recognition of phosphorylated degrons in target proteins. This domain logic supports FBXW12 acting as a substrate receptor in ubiquitin-mediated proteolysis (general mechanism summarized in authoritative reviews). (yumimoto2020fboxproteinsand pages 3-5, zeng2025skp1‐cul1‐f‐boxkeymolecular pages 1-3)
Cullin-RING ligases (CRLs) are multi-subunit E3 ubiquitin ligases composed of (i) a Cullin scaffold, (ii) a RING protein (RBX1/RBX2) that recruits E2~ubiquitin, and (iii) an adaptor plus substrate receptor module that determines substrate specificity. (zhang2023advancesinthe pages 1-2)
The SCF complex (SKP1–CUL1–F-box) is a canonical CRL in which the F-box protein binds SKP1 and confers substrate specificity. F-box proteins are commonly classified by their C-terminal substrate-binding domain (e.g., Fbxw = WD40 repeat-containing). (zeng2025skp1‐cul1‐f‐boxkeymolecular pages 1-3, yumimoto2020fboxproteinsand pages 3-5)
Functional implication for FBXW12: As an FBXW-class protein (F-box + WD repeats), FBXW12 is expected to function as a substrate receptor that recruits specific proteins to an SCF/CRL for ubiquitination and proteasome-directed degradation (or other ubiquitin-dependent fates). The primary experimental substrate currently supported for FBXW12 is IL-22 receptor (IL-22R/IL-22RA1). (franz2015thehumanil22 pages 3-5, franz2015thehumanil22 pages 6-8)
A focused mechanistic study in human epithelial systems identified FBXW12 as a previously undescribed SCF-family E3 ligase subunit that destabilizes the human IL-22 receptor (IL-22R) by promoting its ubiquitination and degradation. (franz2015thehumanil22 pages 3-5, franz2015thehumanil22 pages 1-2)
Key mechanistic findings include:
- Physical association with IL-22R: FBXW12 and IL-22R co-immunoprecipitate in cells. (franz2015thehumanil22 pages 3-5)
- Association with SCF machinery: FBXW12 associates with SCF components including SKP1 and CUL1, consistent with being an SCF substrate receptor. (franz2015thehumanil22 pages 3-5)
- Direct ubiquitination capacity in vitro: In a cell-free system, IL-22R ubiquitination is observed when ubiquitin machinery and SCF constituents (including FBXW12) are present. (franz2015thehumanil22 pages 3-5, franz2015thehumanil22 pages 6-8)
Quantitative effect size: IL-22R half-life is reported to be ~6 hours at baseline and is accelerated to ~2 hours with FBXW12 overexpression, supporting a substantial increase in receptor turnover. (franz2015thehumanil22 pages 3-5)
Ubiquitin linkage note: The available excerpts demonstrate ubiquitination and proteasome-directed degradation but do not specify ubiquitin linkage topology (e.g., K48 vs K63). (franz2015thehumanil22 pages 6-8, franz2015thehumanil22 pages 3-5)
IL-22 signaling is classically transduced via JAK/STAT3 in epithelial cells. In the epithelial models used, FBXW12 knockdown increases IL-22R abundance and enhances IL-22 responsiveness:
- Increased STAT3 phosphorylation in response to IL-22 upon FBXW12 depletion. (franz2015thehumanil22 pages 5-6, franz2015thehumanil22 pages 1-2)
- Increased MAPK signaling with enhanced ERK and JNK phosphorylation (more constitutive and inducible activation reported). (franz2015thehumanil22 pages 6-8, franz2015thehumanil22 pages 5-6)
These data position FBXW12 as a negative post-translational regulator of IL-22R abundance and IL-22–dependent epithelial signaling.
Direct subcellular localization mapping of FBXW12 (e.g., nuclear vs cytosolic distribution) was not identified in the retrieved excerpts. However, the mechanism demonstrated—SCF association and receptor ubiquitination leading to degradation—places FBXW12 function within the intracellular ubiquitin–proteasome system and in the context of IL-22R processing/turnover in epithelial cells. (franz2015thehumanil22 pages 3-5, franz2015thehumanil22 pages 6-8)
A 2023 review of Th22/IL-22 in infectious diseases summarizes that FBXW12 degrades IL-22R and restricts lung epithelial proliferation, and further proposes that silencing FBXW12 may be a therapeutic method for infection-induced epithelial damage (review-level claim referencing prior primary research). (zhang2023currentknowledgeof pages 11-12)
A 2024 review on F-box proteins in spermatogenesis reports FBXW12 among F-box genes with highest transcript levels in human testis, suggesting a potential (but as yet mechanistically unresolved) role in male germ cell biology. This is currently expression-based inference, not direct functional proof. (xuan2024theemergingand pages 7-8)
A 2023 mini-review of circRNAs in diabetic nephropathy discusses circ-FBXW12 (a circular RNA derived from the FBXW12 locus) as being overexpressed in diabetic nephropathy model systems; suppressing circ-FBXW12 reduced mesangial cell proliferation, oxidative stress, and extracellular matrix production via a miR-31-5p/LIN28B axis. This evidence concerns circRNA biology, and should not be conflated with the linear FBXW12 protein’s E3-ligase substrate receptor activity. (basudkar2023currentclinicalinsights pages 6-8)
The primary FBXW12–IL-22R study explicitly suggests that therapeutic inhibition of FBXW12 could increase IL-22R abundance and augment IL-22 signaling, potentially bolstering mucosal host defense and infection containment. (franz2015thehumanil22 pages 1-2, franz2015thehumanil22 pages 6-8)
A 2023 infectious disease review reiterates a similar translational concept, proposing FBXW12 silencing as a strategy to mitigate infection-induced epithelial damage (review-level synthesis). (zhang2023currentknowledgeof pages 11-12)
Clinical trial landscape: A ClinicalTrials.gov search using FBXW12/FBXO35/FBW12 terms did not yield relevant FBXW12-targeted interventional trials in the retrieved results. (tool result; no relevant trial context IDs available)
The circRNA diabetic nephropathy review frames circRNAs as potential diagnostic/therapeutic biomarkers and includes circ-FBXW12 among reported DN-associated circRNAs, but this is not yet a validated clinical biomarker implementation for FBXW12. (basudkar2023currentclinicalinsights pages 6-8, basudkar2023currentclinicalinsights pages 1-2)
High-confidence function (direct evidence): FBXW12 is best-supported as an SCF/CRL substrate receptor that promotes ubiquitination and degradation of IL-22R, thereby attenuating IL-22–STAT3/MAPK signaling and acting as an epithelial growth suppressor in cell culture systems. (franz2015thehumanil22 pages 3-5, franz2015thehumanil22 pages 6-8)
Moderate-confidence biological roles (inference): Given its domain architecture (F-box + WD repeats) and SCF paradigm, FBXW12 likely recognizes additional substrates beyond IL-22R, potentially via WD-repeat mediated interactions with phosphorylated motifs; however, additional validated substrates were not identified in the retrieved corpus. (poirson2017mappingtheinteractome media 39749cd6, yumimoto2020fboxproteinsand pages 3-5)
Lower-confidence / hypothesis-generating signals: The testis-enriched transcript observation suggests reproductive roles but currently lacks mechanistic validation. (xuan2024theemergingand pages 7-8)
From primary mechanistic FBXW12 study (2015):
- IL-22R half-life decreased from ~6 h to ~2 h with FBXW12 overexpression. (franz2015thehumanil22 pages 3-5)
- Baseline cell-cycle distribution in control: ~80% G0/G1, ~14% S, ~4% G2/M; proliferation differences significant by ANOVA (p<0.05) at 24 h and 40 h with 5 replicates/group in one reported experiment. (franz2015thehumanil22 pages 6-8)
From 2023 diabetic nephropathy circRNA mini-review (epidemiology):
- In the USA, ~1 in 3 people with diabetes have diabetic nephropathy; globally DN occurs in ~30–40% of patients with diabetes. (basudkar2023currentclinicalinsights pages 1-2)
| Evidence type | Finding | Molecular partners/substrates | Biological context (cell type/tissue/disease) | Key quantitative/statistical data | Publication (with year) | URL/DOI | Citation context ID |
|---|---|---|---|---|---|---|---|
| Primary | Human FBXW12 functions as an SCF-family E3 ligase subunit that binds IL-22R and promotes its ubiquitination and degradation | IL-22R/IL-22RA1; SKP1; CUL1 | Human epithelial cells; Beas-2B and HeLa; mucosal/airway epithelial signaling | IL-22R half-life shortened from ~6 h to ~2 h with FBXW12 overexpression; representative statistics include p<0.05, n=4 in degradation assays | Franz et al. (2015) | https://doi.org/10.1155/2015/912713 | (franz2015thehumanil22 pages 3-5) |
| Primary | FBXW12 knockdown increases IL-22R abundance and enhances downstream IL-22 signaling | IL-22R; STAT3; ERK; JNK | HeLa epithelial cells; IL-22-responsive epithelial signaling | Relative p-STAT3 densitometry values reported as 0, 0.75, 1.5, 2.25 under assay conditions; IL-22 at 60 ng/mL for 60 min in signaling assays | Franz et al. (2015) | https://doi.org/10.1155/2015/912713 | (franz2015thehumanil22 pages 5-6) |
| Primary | FBXW12 behaves as an epithelial growth suppressor; depletion promotes proliferation and cell-cycle progression | FBXW12-linked IL-22R/STAT3/MAPK axis | HeLa epithelial cells | Control cell-cycle distribution approximately 80% G0/G1, 14% S, 4% G2/M; growth differences significant at 24 h and 40 h by ANOVA (p<0.05), 5 replicates/group | Franz et al. (2015) | https://doi.org/10.1155/2015/912713 | (franz2015thehumanil22 pages 6-8) |
| Review | FBXW12 degrades IL-22R and restricts lung epithelial proliferation; silencing FBXW12 is proposed as a therapeutic strategy for infection-induced epithelial damage | IL-22R | Infectious disease / lung epithelium / IL-22 biology | No new quantitative data reported in the review excerpt | Zhang et al. (2023) | https://doi.org/10.3390/pathogens12020176 | (zhang2023currentknowledgeof pages 11-12) |
| Review | FBXW12 is among F-box genes with high transcript levels in human testis, suggesting possible spermatogenesis-related roles, but direct mechanisms remain unresolved | Not specified for FBXW12 in excerpt | Human testis / spermatogenesis / male infertility context | Qualitative expression statement only; no numeric values in excerpt | Xuan et al. (2024) | https://doi.org/10.1186/s13619-024-00196-9 | (xuan2024theemergingand pages 7-8) |
| Bioinformatic/annotation | FBXW12 maps to UniProt Q6X9E4 and is annotated as an E3 CRL adaptor with F-box and WD-repeat domains, supporting classification as an FBXW substrate receptor | F-box domain; WD repeats | Human protein annotation / domain architecture | Length reported as 394 aa in table entry | Poirson et al. (2017) | https://doi.org/10.1111/febs.14193 | (poirson2017mappingtheinteractome pages 23-23, poirson2017mappingtheinteractome media 39749cd6) |
| Review (circRNA, not linear protein) | circ-FBXW12 is overexpressed in diabetic nephropathy models; its knockdown reduces proliferation, oxidative stress, and ECM production via the miR-31-5p/LIN28B axis | circ-FBXW12; miR-31-5p; LIN28B | Human mesangial cells / diabetic nephropathy | Epidemiology in review: ~1 in 3 people with diabetes in the USA have DN; globally DN occurs in 30–40% of patients with diabetes | Basudkar et al. (2023) | https://doi.org/10.1515/dine-2023-0007 | (basudkar2023currentclinicalinsights pages 6-8, basudkar2023currentclinicalinsights pages 1-2) |
Table: This table summarizes direct and indirect evidence relevant to human FBXW12 (UniProt Q6X9E4), emphasizing experimentally supported function, pathway context, domain annotation, and translational implications. It distinguishes evidence on the linear FBXW12 protein from circ-FBXW12 literature to avoid gene-product conflation.
References
(poirson2017mappingtheinteractome pages 23-23): Juline Poirson, Elise Biquand, Marie‐Laure Straub, Patricia Cassonnet, Yves Nominé, Louis Jones, Sylvie van der Werf, Gilles Travé, Katia Zanier, Yves Jacob, Caroline Demeret, and Murielle Masson. Mapping the interactome of hpv e6 and e7 oncoproteins with the ubiquitin‐proteasome system. The FEBS Journal, 284:3171-3201, Oct 2017. URL: https://doi.org/10.1111/febs.14193, doi:10.1111/febs.14193. This article has 74 citations.
(poirson2017mappingtheinteractome media 39749cd6): Juline Poirson, Elise Biquand, Marie‐Laure Straub, Patricia Cassonnet, Yves Nominé, Louis Jones, Sylvie van der Werf, Gilles Travé, Katia Zanier, Yves Jacob, Caroline Demeret, and Murielle Masson. Mapping the interactome of hpv e6 and e7 oncoproteins with the ubiquitin‐proteasome system. The FEBS Journal, 284:3171-3201, Oct 2017. URL: https://doi.org/10.1111/febs.14193, doi:10.1111/febs.14193. This article has 74 citations.
(yumimoto2020fboxproteinsand pages 3-5): Kanae Yumimoto, Yuhei Yamauchi, and Keiichi I. Nakayama. F-box proteins and cancer. Cancers, 12:1249, May 2020. URL: https://doi.org/10.3390/cancers12051249, doi:10.3390/cancers12051249. This article has 70 citations.
(zeng2025skp1‐cul1‐f‐boxkeymolecular pages 1-3): Xiangrong Zeng, Jiaying Cao, Juan Xu, Zihua Zhou, Chen Long, Yanhong Zhou, and Jingqiong Tang. Skp1‐cul1‐f‐box: key molecular targets affecting disease progression. The FASEB Journal, Jan 2025. URL: https://doi.org/10.1096/fj.202402816rr, doi:10.1096/fj.202402816rr. This article has 15 citations.
(zhang2023advancesinthe pages 1-2): Xiaoying Zhang, Yu’e Liu, Tong Zhang, Yuying Tan, Xiangpeng Dai, Yong-Guang Yang, and Xiaoling Zhang. Advances in the potential roles of cullin-ring ligases in regulating autoimmune diseases. Frontiers in Immunology, Mar 2023. URL: https://doi.org/10.3389/fimmu.2023.1125224, doi:10.3389/fimmu.2023.1125224. This article has 14 citations and is from a peer-reviewed journal.
(franz2015thehumanil22 pages 3-5): Joseph Franz, Jacob Jerome, Travis Lear, Qiaoke Gong, and Nathaniel M. Weathington. The human il-22 receptor is regulated through the action of the novel e3 ligase subunit fbxw12, which functions as an epithelial growth suppressor. Journal of Immunology Research, 2015:1-9, Jun 2015. URL: https://doi.org/10.1155/2015/912713, doi:10.1155/2015/912713. This article has 13 citations and is from a peer-reviewed journal.
(franz2015thehumanil22 pages 6-8): Joseph Franz, Jacob Jerome, Travis Lear, Qiaoke Gong, and Nathaniel M. Weathington. The human il-22 receptor is regulated through the action of the novel e3 ligase subunit fbxw12, which functions as an epithelial growth suppressor. Journal of Immunology Research, 2015:1-9, Jun 2015. URL: https://doi.org/10.1155/2015/912713, doi:10.1155/2015/912713. This article has 13 citations and is from a peer-reviewed journal.
(franz2015thehumanil22 pages 1-2): Joseph Franz, Jacob Jerome, Travis Lear, Qiaoke Gong, and Nathaniel M. Weathington. The human il-22 receptor is regulated through the action of the novel e3 ligase subunit fbxw12, which functions as an epithelial growth suppressor. Journal of Immunology Research, 2015:1-9, Jun 2015. URL: https://doi.org/10.1155/2015/912713, doi:10.1155/2015/912713. This article has 13 citations and is from a peer-reviewed journal.
(franz2015thehumanil22 pages 5-6): Joseph Franz, Jacob Jerome, Travis Lear, Qiaoke Gong, and Nathaniel M. Weathington. The human il-22 receptor is regulated through the action of the novel e3 ligase subunit fbxw12, which functions as an epithelial growth suppressor. Journal of Immunology Research, 2015:1-9, Jun 2015. URL: https://doi.org/10.1155/2015/912713, doi:10.1155/2015/912713. This article has 13 citations and is from a peer-reviewed journal.
(zhang2023currentknowledgeof pages 11-12): Kunyu Zhang, Lei Chen, Chenyu Zhu, Meng Zhang, and Chaozhao Liang. Current knowledge of th22 cell and il-22 functions in infectious diseases. Pathogens, 12:176, Jan 2023. URL: https://doi.org/10.3390/pathogens12020176, doi:10.3390/pathogens12020176. This article has 55 citations.
(xuan2024theemergingand pages 7-8): Zhuang Xuan, Jun Ruan, Canquan Zhou, and Zhi-ming Li. The emerging and diverse roles of f-box proteins in spermatogenesis and male infertility. Cell Regeneration, Jun 2024. URL: https://doi.org/10.1186/s13619-024-00196-9, doi:10.1186/s13619-024-00196-9. This article has 5 citations.
(basudkar2023currentclinicalinsights pages 6-8): Vivek Basudkar, Saiprasad Ajgaonkar, Dilip Mehta, and Sujit Nair. Current clinical insights into circrnas and signal transduction in diabetic nephropathy. Diabetic Nephropathy, 3:58-67, Sep 2023. URL: https://doi.org/10.1515/dine-2023-0007, doi:10.1515/dine-2023-0007. This article has 3 citations.
(basudkar2023currentclinicalinsights pages 1-2): Vivek Basudkar, Saiprasad Ajgaonkar, Dilip Mehta, and Sujit Nair. Current clinical insights into circrnas and signal transduction in diabetic nephropathy. Diabetic Nephropathy, 3:58-67, Sep 2023. URL: https://doi.org/10.1515/dine-2023-0007, doi:10.1515/dine-2023-0007. This article has 3 citations.
(zhang2023advancesinthe pages 10-12): Xiaoying Zhang, Yu’e Liu, Tong Zhang, Yuying Tan, Xiangpeng Dai, Yong-Guang Yang, and Xiaoling Zhang. Advances in the potential roles of cullin-ring ligases in regulating autoimmune diseases. Frontiers in Immunology, Mar 2023. URL: https://doi.org/10.3389/fimmu.2023.1125224, doi:10.3389/fimmu.2023.1125224. This article has 14 citations and is from a peer-reviewed journal.