Affinage

RHOBTB1

Rho-related BTB domain-containing protein 1 · UniProt O94844

Length
696 aa
Mass
79.4 kDa
Annotated
2026-06-10
14 papers in source corpus 9 papers cited in narrative 11 extracted findings
Cross-family judge faithfulness: 6/6 claims corpus-supported (100%)

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

RHOBTB1 is an atypical Rho GTPase that functions principally as a substrate adaptor for the Cullin-3 (CUL3) E3 ubiquitin ligase, coupling targeted protein degradation to the control of vascular smooth muscle tone and actin cytoskeletal dynamics (PMID:30896450, PMID:41926228). It delivers phosphodiesterase 5 (PDE5) to CUL3 for ubiquitination and inhibition, thereby augmenting nitric oxide-driven cGMP signaling and promoting vasodilation (PMID:30896450), and it likewise targets the splicing regulator RbFox2 for CUL3-dependent degradation to maintain actin cytoskeletal integrity and reverse arterial stiffness (PMID:35358093, PMID:41926228). Substrate recruitment is partitioned across the protein: the C-terminal domain mediates PDE5 binding while Pro353 and Ser363 are required for CUL3 association, and the full C-terminal B1B2C region is the minimal degradation-competent module (PMID:37575477). Through its N-terminal Rho domain, RHOBTB1 binds the coiled-coil region of ROCK1/ROCK2 and is itself a ROCK1 phosphorylation substrate, with phosphorylation modulating its CUL3 association — linking it to suppression of cancer cell invasion (PMID:31431478). Beyond degradation, RHOBTB1 maintains Golgi integrity via control of METTL7B expression and localizes to early endosomes where it governs endosomal/lysosomal organization and retrograde cargo trafficking (PMID:28219369, PMID:32354068). Its expression is repressed by miR-31/miR-31a-5p, linking its loss to cardiomyocyte proliferation and to enhanced tumor cell migration and invasion (PMID:29053138, PMID:39673615).

Mechanistic history

Synthesis pass · year-by-year structured walk · 8 steps
  1. 2017 Medium

    Established the first cellular role for RhoBTB1 by linking it to organelle integrity, addressing whether this atypical GTPase has a defined cellular function.

    Evidence RNAi silencing, transcriptome analysis, and Golgi-morphology rescue experiments in breast cancer cells

    PMID:28219369

    Open questions at the time
    • Mechanism by which RhoBTB1 controls METTL7B expression unknown
    • Does not establish direct molecular partners or enzymatic activity
  2. 2017 Medium

    Identified an upstream regulatory mechanism, showing RhoBTB1 is a repressed target of miR-31a-5p that restrains cardiomyocyte proliferation.

    Evidence miRNA arrays, target knockdown phenocopy, and antagomir injection in neonatal rats

    PMID:29053138

    Open questions at the time
    • Downstream effectors mediating proliferation control not defined
    • Direct 3'UTR binding inferred rather than fully dissected here
  3. 2019 High

    Defined RhoBTB1's core molecular function as a CUL3 substrate adaptor for PDE5, explaining how it augments cGMP signaling and vasodilation in vivo.

    Evidence Smooth muscle-specific inducible transgene, reciprocal Co-IP, and functional vasodilation/cGMP assays in two hypertension models

    PMID:30896450

    Open questions at the time
    • Precise domain requirements for PDE5 and CUL3 binding not yet mapped
    • Other substrates beyond PDE5 unknown at this stage
  4. 2019 High

    Connected the Rho domain to ROCK kinases and revealed a feedback loop, showing RhoBTB1 binds ROCK1/2, is phosphorylated by ROCK1, and that this phosphorylation controls its CUL3 association.

    Evidence Co-IP, pulldown, interface mutagenesis, and in vitro kinase assay; Matrigel invasion phenotyping in prostate cancer cells

    PMID:31431478

    Open questions at the time
    • Functional consequence of ROCK binding for ROCK activity not resolved
    • Invasion suppression role (Medium-confidence) lacks in vivo validation
  5. 2020 Medium

    Localized RhoBTB1 to early endosomes and broadened its role to membrane trafficking, showing its dysregulation disrupts endosome/lysosome organization and retrograde cargo delivery.

    Evidence RNAi screen, high-content imaging, and cargo trafficking assays

    PMID:32354068

    Open questions at the time
    • Whether trafficking role is CUL3-dependent unknown
    • Direct trafficking machinery partners not identified
  6. 2022 High

    Demonstrated RhoBTB1 can reverse established arterial stiffness via actin depolymerization, establishing a therapeutically relevant phenotype downstream of its function.

    Evidence Inducible smooth muscle transgene, actin polymerization measurement, cofilin/VASP immunoblotting, in vivo arterial stiffness measurements

    PMID:35358093

    Open questions at the time
    • Direct substrate linking RhoBTB1 to cofilin/VASP changes not yet identified
    • Mechanistic coupling to CUL3 degradation not established in this study
  7. 2023 High

    Mapped the substrate-adaptor architecture and identified additional candidate substrates, defining the minimal degradation module and key CUL3-binding residues.

    Evidence Domain truncation, site-directed mutagenesis (Pro353, Ser363), APEX2 proximity labeling/MS, and Co-IP

    PMID:37575477

    Open questions at the time
    • SETD2 as substrate is Medium-confidence and needs ubiquitination/degradation kinetics
    • Physiological context of SETD2 regulation not defined
  8. 2026 High

    Identified RbFox2 as a CUL3-dependent RhoBTB1 substrate, providing a molecular link from the adaptor function to actin integrity and arterial stiffness.

    Evidence Reciprocal Co-IP, ubiquitination assay, proximity labeling, siRNA, CUL3 deletion, and RbFox2 floxed mouse model

    PMID:41926228

    Open questions at the time
    • How RbFox2 levels translate mechanistically to actin dynamics not fully resolved
    • Interplay between PDE5 and RbFox2 substrate streams unknown

Open questions

Synthesis pass · forward-looking unresolved questions
  • How RhoBTB1's distinct functional arms — CUL3-dependent substrate degradation, ROCK binding/phosphorylation, and endosomal/Golgi trafficking — are integrated and tissue-specifically deployed remains unresolved.
  • No unified model linking trafficking role to CUL3 adaptor function
  • Full substrate repertoire incomplete
  • No structural model of the RhoBTB1-CUL3-substrate complex

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0060090 molecular adaptor activity 3 GO:0140096 catalytic activity, acting on a protein 3 GO:0098772 molecular function regulator activity 2
Localization
GO:0005794 Golgi apparatus 2 GO:0005768 endosome 1
Pathway
R-HSA-392499 Metabolism of proteins 3 R-HSA-162582 Signal Transduction 2 R-HSA-5653656 Vesicle-mediated transport 1
Complex memberships
Cullin-3 (CUL3) E3 ubiquitin ligase

Evidence

Reading pass · 11 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2019 RhoBTB1 acts as a substrate adaptor delivering phosphodiesterase 5 (PDE5) to the Cullin-3 (CUL3) E3 RING ubiquitin ligase complex, leading to PDE5 ubiquitination and inhibition, thereby augmenting cGMP responses to nitric oxide in vascular smooth muscle cells. Genetic complementation (inducible smooth muscle-specific RhoBTB1 transgene), Co-immunoprecipitation, functional vasodilation assays in vivo The Journal of clinical investigation High 30896450
2023 The C-terminal half of RhoBTB1 (B1B2C region, comprising both BTB domains and C-terminal domain) is the minimal region required for PDE5 recruitment and subsequent proteasomal degradation via CUL3; the C-terminal domain is essential for PDE5 binding, and Pro353 and Ser363 are key residues required for CUL3 binding (mutation impairs CUL3 binding and PDE5 degradation without disrupting PDE5 binding). Domain truncation, Co-immunoprecipitation, site-directed mutagenesis, APEX2 proximity labeling/mass spectrometry Function (Oxford, England) High 37575477
2023 SETD2 is a binding partner of RhoBTB1 (validated by Co-IP), and SETD2 levels increase upon proteasome inhibition, Cullin complex inhibition, CUL3 deletion, or RhoBTB1 siRNA knockdown, suggesting SETD2 is a substrate regulated by the RhoBTB1-CUL3 ubiquitin-proteasome axis. APEX2 proximity labeling/mass spectrometry, Co-immunoprecipitation, siRNA knockdown, pharmacological proteasome/Cullin inhibition Function (Oxford, England) Medium 37575477
2022 RhoBTB1 reverses established arterial stiffness by promoting actin depolymerization in vascular smooth muscle; angiotensin II-induced actin polymerization in the aorta is reversed by RhoBTB1 restoration, with consistent changes in levels of cofilin and vasodilator-stimulated phosphoprotein (VASP), two regulators of actin polymerization. Inducible smooth muscle-specific RhoBTB1 transgene, measurement of actin polymerization, immunoblotting for cofilin and VASP, arterial stiffness measurements in vivo JCI insight High 35358093
2026 RhoBTB1 interacts with and promotes CUL3-dependent ubiquitination and proteasomal degradation of RbFox2 in smooth muscle cells; loss of RhoBTB1 (by siRNA or angiotensin II) elevates RbFox2, and RbFox2 regulates actin cytoskeletal integrity and arterial stiffness. Co-immunoprecipitation, proximity labeling/mass spectrometry, siRNA knockdown, CUL3 deletion, RbFox2 floxed mouse model, ubiquitination assay JCI insight High 41926228
2019 RhoBTB1 associates with ROCK1 and ROCK2; the interaction with ROCK1 is mediated by the Rho domain of RhoBTB1 binding to the coiled-coil region of ROCK1 near its kinase domain. Two amino acids in the Rho domain alter RhoBTB1-ROCK1 association. RhoBTB1 is a substrate for ROCK1, and mutation of putative ROCK1 phosphorylation sites on RhoBTB1 reduces its association with Cullin3. Co-immunoprecipitation, pulldown, site-directed mutagenesis, in vitro kinase assay The Biochemical journal High 31431478
2019 RhoBTB1 depletion increases prostate cancer cell invasion and induces elongation in Matrigel, a phenotype similar to that induced by depletion of ROCK1 and ROCK2, suggesting RhoBTB1 suppresses cancer cell invasion through interaction with ROCKs. siRNA knockdown, Matrigel invasion assay, cell morphology imaging The Biochemical journal Medium 31431478
2017 RhoBTB1 regulates the integrity of the Golgi complex through control of METTL7B expression; silencing of either RhoBTB1 or METTL7B leads to Golgi fragmentation, and restoration of RhoBTB1 expression rescues Golgi morphology and inhibits breast cancer cell invasion. Gene silencing (RNAi), transcriptome analysis, Q-PCR, cell imaging (Golgi morphology), rescue experiments BMC cancer Medium 28219369
2020 RhoBTB1 localizes to early endosomal intermediates, and changes in RhoBTB1 levels cause disturbances to Golgi architecture, profound changes to organisation and distribution of endosomes and lysosomes, and defects in delivery of two classes of cargo molecules to downstream compartments, linking RhoBTB1 to endocytosis and retrograde traffic pathways. RNA interference screen, high-content image-based analysis, fluorescence microscopy, cargo trafficking assays Cells Medium 32354068
2017 RhoBTB1 is a target gene of miR-31a-5p; miR-31a-5p promotes postnatal cardiomyocyte proliferation by repressing RhoBTB1, and RhoBTB1 knockdown phenocopies miR-31a-5p overexpression in promoting cardiomyocyte proliferation markers. miRNA arrays, luciferase reporter assay (implied by target validation), immunofluorescence, EdU/Ki-67/PHH3 proliferation assays, antagomir injection in neonatal rats Experimental & molecular medicine Medium 29053138
2024 Exosomal miR-31 from cutaneous squamous cell carcinoma (CSCC) cells directly targets the 3'UTR of RhoBTB1 (validated by dual luciferase reporter assay), suppressing RhoBTB1 expression and enhancing CSCC cell proliferation, migration, and invasion. Dual luciferase reporter assay, immunoblotting, qPCR, MTT assay, Transwell assay, differential ultracentrifugation for exosome isolation Archives of dermatological research Medium 39673615

Source papers

Stage 0 corpus · 14 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2017 The tumor suppressor RhoBTB1 controls Golgi integrity and breast cancer cell invasion through METTL7B. BMC cancer 70 28219369
2012 The tumor suppressor gene RhoBTB1 is a novel target of miR-31 in human colon cancer. International journal of oncology 51 23258531
2017 miR-31a-5p promotes postnatal cardiomyocyte proliferation by targeting RhoBTB1. Experimental & molecular medicine 38 29053138
2019 RhoBTB1 protects against hypertension and arterial stiffness by restraining phosphodiesterase 5 activity. The Journal of clinical investigation 37 30896450
2005 Identification of a candidate tumor suppressor gene RHOBTB1 located at a novel allelic loss region 10q21 in head and neck cancer. Journal of cancer research and clinical oncology 33 16170569
2022 RhoBTB1 reverses established arterial stiffness in angiotensin II-induced hypertension by promoting actin depolymerization. JCI insight 21 35358093
2020 PPARγ and RhoBTB1 in hypertension. Current opinion in nephrology and hypertension 19 31789920
2019 RhoBTB1 interacts with ROCKs and inhibits invasion. The Biochemical journal 13 31431478
2020 RNA Interference Screening Identifies Novel Roles for RhoBTB1 and RhoBTB3 in Membrane Trafficking Events in Mammalian Cells. Cells 7 32354068
2023 Structure and Function of RhoBTB1 Required for Substrate Specificity and Cullin-3 Ubiquitination. Function (Oxford, England) 5 37575477
2025 Machine learning analysis of FOSL2 and RHoBTB1 as central immunological regulators in knee osteoarthritis synovium. The Journal of international medical research 2 40287984
2024 The 2023 Walter B. Cannon Award Lecture: Mechanisms Regulating Vascular Function and Blood Pressure by the PPARγ-RhoBTB1-CUL3 Pathway. Function (Oxford, England) 1 38196837
2024 Cutaneous squamous cell carcinoma-derived exosomal MicroRNA-31 acts as an oncogene by targeting the tumor suppressor RhoBTB1. Archives of dermatological research 1 39673615
2026 Vascular smooth muscle RbFox2 regulates the cytoskeleton and arterial stiffness by a RhoBTB1/Cullin-3 mechanism. JCI insight 0 41926228

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