RUFY3

RUFY3 is a RUN/FYVE domain adapter protein that couples small-GTPase signaling to membrane trafficking and actin-based cytoskeletal remodeling, governing both endo-lysosomal positioning and neuronal morphogenesis (PMID:35314681, PMID:29089386). As an Arl8b effector, it bridges Arl8b to the JIP4-dynein-dynactin retrograde motor to control late endosome/lysosome positioning and size (PMID:35314681); a FYVE-domain-bearing isoform binds endosomal PI3P and drives perinuclear endo-lysosome clustering in activated macrophages, where it shapes migration, MHC II antigen presentation, interferon-γ responses, and restriction of intracellular Salmonella (PMID:37463962). RUFY3 also acts as a noncanonical guanine-nucleotide exchange factor for Rab5, partnering with HPIP at focal adhesions and endosomes to promote focal adhesion disassembly, FAK activation, β1-integrin trafficking, and cell migration (PMID:37797694). In neurons, RUFY3 restricts surplus axon formation in a PI3K-dependent manner (PMID:17439943) and, recruited via M6A glycoprotein to lipid raft domains, assembles a ternary complex with Rap2 that activates the Rac-GEF Tiam2/STEF to direct axon growth and polarity (PMID:29089386); it further organizes growth-cone actin through interactions with Fascin and Drebrin (PMID:24720729). RUFY3 is required for caspase-3-mediated axon degeneration, with dephosphorylation at S34 permitting degeneration even when caspase-3 is active (PMID:31221560). In cancer, RUFY3 promotes migration, invasion, and EMT, interacting with PAK1 to build F-actin-rich protrusions (PMID:25766321) and acting through FOXK1 (PMID:28623323), while its expression is transcriptionally driven by HOXD9 (PMID:31547840).

1. 2007 Medium

   Established the first cellular role for RUFY3 by showing it constrains axon number, defining it as a regulator of neuronal polarity rather than an uncharacterized RUN-domain protein.

   Evidence Overexpression and RNAi in cultured hippocampal neurons with PI3K-inhibitor epistasis

   PMID:17439943

   Open questions at the time

   • No molecular partner identified at this stage
   • Mechanistic link to PI3K not biochemically defined
2. 2014 Medium

   Connected RUFY3's polarity function to actin organization by identifying physical interactions with Fascin and Drebrin in growth cones.

   Evidence Co-IP and colocalization plus shRNA/overexpression in mouse hippocampal neurons

   PMID:24720729

   Open questions at the time

   • Direct vs indirect binding not resolved
   • Single lab, two orthogonal methods
3. 2015 Medium

   Extended RUFY3's actin-remodeling role to tumor invasion by linking it to PAK1-driven protrusion formation.

   Evidence Co-IP, PAK1 inhibitor, KD/OE and invasion assays in gastric cancer cells

   PMID:25766321

   Open questions at the time

   • Whether PAK1 acts upstream or downstream not fully separated
   • No structural basis for interaction
4. 2017 High

   Placed RUFY3 in a defined neuronal signaling pathway, showing it scaffolds Rap2 and activates Tiam2/STEF at lipid rafts to drive axon growth.

   Evidence Rufy3-KO mice, detergent-resistant membrane fractionation, Co-IP and polarity assays

   PMID:29089386

   Open questions at the time

   • Direct GEF activation mechanism of Tiam2/STEF not reconstituted
   • Role of M6A recruitment in other cell types untested
5. 2017 Medium

   Defined a pro-metastatic axis in which RUFY3 acts through transcription factor FOXK1 to drive EMT.

   Evidence Co-IP, FOXK1 siRNA epistasis, EMT markers and orthotopic implantation in colorectal cancer

   PMID:28623323

   Open questions at the time

   • How a trafficking adapter regulates a transcription factor unclear
   • Direct vs indirect interaction not resolved
6. 2017 Low

   Positioned RUFY3 as a downstream effector of TGF-β1 in EMT regulation.

   Evidence TGF-β1 dose-response and siRNA with EMT/invasion readouts in colorectal cancer cells

   PMID:28089833

   Open questions at the time

   • No direct binding or pathway reconstitution
   • Single method per claim, single lab
7. 2019 Medium

   Identified an upstream transcriptional driver of RUFY3 by showing HOXD9 binds the RUFY3 promoter to activate its expression in gastric cancer.

   Evidence ChIP, luciferase reporter and siRNA epistasis with tumor growth assays

   PMID:31547840

   Open questions at the time

   • Other transcriptional inputs not mapped
   • Single lab
8. 2019 High

   Revealed a degeneration-specific function: RUFY3 is required for caspase-3-mediated axon degeneration, with S34 dephosphorylation as the permissive switch.

   Evidence Mass spec, Rufy3 genetic deletion, phosphosite analysis, in vitro and in vivo sensory axon degeneration

   PMID:31221560

   Open questions at the time

   • Kinase/phosphatase controlling S34 not identified
   • Downstream effectors of dephosphorylated RUFY3 unknown
9. 2021 Low

   Linked RUFY3 to NF-κB-mediated EMT in hepatocellular carcinoma growth and metastasis.

   Evidence siRNA, NF-κB activity assay, EMT markers and xenograft/metastasis models

   PMID:34510031

   Open questions at the time

   • No direct RUFY3-NF-κB interaction demonstrated
   • Mechanism inferred from pathway inhibitors
10. 2022 High

    Defined RUFY3's core trafficking mechanism by establishing it as an Arl8b effector that recruits the JIP4-dynein-dynactin retrograde motor to position lysosomes.

    Evidence Reciprocal Co-IP, knockdown, live-cell imaging, colocalization and PIKFYVE-rescue of lysosome size

    PMID:35314681

    Open questions at the time

    • Stoichiometry of the Arl8b-RUFY3-JIP4 complex unresolved
    • How motor handoff is regulated unknown
11. 2022 Medium

    Extended RUFY3-Rap signaling to injury repair, showing Rufy3 raises Rap1-GTP and activates downstream Rho/Fascin and MEK/ERK pathways for axon repair and synaptic plasticity.

    Evidence Co-IP, Rap1-GTP pull-down, lentiviral OE/KD in a subarachnoid hemorrhage rat model with pathway western blots

    PMID:35461284

    Open questions at the time

    • Whether RUFY3 directly catalyzes Rap1 loading not tested
    • In vivo pathway dependencies inferred from western blot
12. 2023 High

    Resolved isoform-specific specialization, showing a FYVE-bearing immune isoform binds PI3P to position endo-lysosomes and control macrophage immune functions and Salmonella restriction.

    Evidence Isoform characterization, PI3P-binding, phagocyte-specific conditional KO, and in vivo infection models

    PMID:37463962

    Open questions at the time

    • Functional division between isoforms in non-immune cells unclear
    • How PI3P binding integrates with Arl8b effector role not defined
13. 2023 Medium

    Assigned a catalytic activity to RUFY3, identifying it (with HPIP) as a noncanonical Rab5 GEF driving focal adhesion turnover and integrin trafficking.

    Evidence Rab5 GEF activity assay, coiled-coil deletion mutants, Co-IP, focal adhesion and integrin trafficking assays

    PMID:37797694

    Open questions at the time

    • Structural basis of noncanonical GEF activity not solved
    • Single lab
14. 2025 Low

    Tied RUFY3 to cell-death control in cancer by linking a RUFY3-MAP4-CDK1 interaction to suppression of PANoptosis.

    Evidence Co-IP and siRNA with xenograft tumor models in colorectal cancer

    PMID:40879686

    Open questions at the time

    • Single Co-IP without reciprocal validation
    • Mechanism downstream of the complex not established

• How RUFY3's distinct activities — Arl8b/PI3P-dependent lysosome positioning, noncanonical Rab5/Rap GEF function, and S34-regulated degeneration control — are coordinated within a single protein, and which are isoform- or context-specific, remains unresolved.
• No unified structural model connecting RUN, FYVE and coiled-coil domain functions
• Phosphoregulation linking trafficking and degeneration roles unmapped
• Direct GEF mechanism for Rab5/Rap not structurally resolved