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this with annotations you find in gene/protein databases, but these can be outdated or inaccurate.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.
RHOJ is correctly identified as a human gene, corresponding to ENSG00000126785 and named ras homolog family member J. The literature also uses RhoJ, TCL, TC10-like, TC10βL, and occasionally RhoT. However, one element of the supplied UniProt-derived annotation needs correction: RHOJ is consistently classified as a Rho-family, Cdc42-subfamily small GTPase—not a Rab-family GTPase. Its P-loop NTPase, Ras-like small-GTPase, and Rho-family domains are fully consistent with RHOJ; the “Rab family” assignment is most likely an automated annotation error. No same-symbol organism mismatch was found. Open Targets independently maps human RHOJ to ENSG00000126785. (OpenTargets Search: -RHOJ, barlow2019buildingbloodvessels—one pages 7-9, uemura2021rhogtpasesin pages 1-2)
RhoJ’s primary function is to act as a membrane-associated guanine-nucleotide molecular switch. It cycles between signaling-competent GTP-bound and inactive or differently interacting GDP-bound states, thereby coordinating receptor trafficking, focal-adhesion turnover, actin organization, contractility, and directional endothelial migration. Its best-resolved physiological role is in vascular endothelial cells, particularly angiogenic endothelium. The strongest mechanistic model places RhoJ at the intersection of attractive VEGF-A signaling and repulsive semaphorin-3E/PlexinD1 signaling. (uemura2021rhogtpasesin pages 1-2, kaur2011rhojtclregulatesendothelial pages 2-2, fukushima2020rhojintegratesattractive pages 10-13)
| Annotation aspect | Best-supported conclusion | Principal evidence/model | Confidence / limitations |
|---|---|---|---|
| Identity and family | Human RHOJ (ENSG00000126785; aliases TCL, TC10-like) is a Rho-family small GTPase of the Cdc42 subfamily, not a Rab-family protein. The supplied P-loop NTPase, Ras-like small-GTPase, and Rho-family domains support this identity; “Rab family” is likely an automated annotation error. | Human endothelial-expression studies, Rho-GTPase reviews, and Open Targets nomenclature independently identify RHOJ as a Rho/Cdc42-subfamily protein. (OpenTargets Search: -RHOJ, barlow2019buildingbloodvessels—one pages 7-9, uemura2021rhogtpasesin pages 1-2, kaur2011rhojtclregulatesendothelial pages 2-2) | High. No symbol or organism mismatch was found. The accession may represent an Ensembl-derived isoform rather than the canonical reviewed entry, but it maps to human RHOJ. |
| Catalytic molecular-switch function | RhoJ binds GDP or GTP and intrinsically catalyzes GTP + H₂O → GDP + Pi (EC 3.6.5.2). GTP-bound RhoJ is the signaling-competent state; guanine nucleotides—not proteins—are its substrates. Active RhoJ binds CRIB-domain proteins such as PAK, WASP, and N-WASP and interacts with PlexinD1. | Biochemical classification and interaction studies of RhoJ/Cdc42-subfamily GTPases. (uemura2021rhogtpasesin pages 1-2, leszczynska2011signallingandfunction pages 34-38, uemura2021rhogtpasesin pages 4-7) | High for molecular-switch chemistry and CRIB binding; moderate for the complete physiological effector map. RHOJ-specific kinetic constants and a definitive GEF/GAP/GDI set remain insufficiently characterized. |
| Subcellular localization | RhoJ functions on intracellular membrane-associated structures and at adhesion sites: endogenous protein has been observed at punctate focal adhesions, while tagged protein also occurs at the plasma membrane, intracellular vesicles, and early/sorting endosomes. Strong overexpression can produce additional endosomal or lysosomal localization. | Colocalization with vinculin, talin, and phospho-FAK-Y397 in endothelial cells; trafficking studies using tagged RhoJ. (kaur2011rhojtclregulatesendothelial pages 2-2, leszczynska2011signallingandfunction pages 34-38, leszczynska2011signallingandfunction pages 134-138) | High for focal adhesions; moderate for vesicular compartments because some observations depend on expression level. Membrane association is consistent with the C-terminal CAAX motif typical of Rho GTPases. |
| Endothelial cytoskeletal role | RhoJ promotes endothelial migration and tube formation while regulating focal-adhesion turnover, actomyosin contractility, stress fibers, and extracellular-matrix remodeling. Knockdown generally increases focal adhesions and contractile structures and impairs motility or tubulogenesis; activated RhoJ produces the reciprocal phenotype. | RHOJ siRNA, dominant-active RhoJ, Matrigel and organotypic tube assays, wound migration, collagen contraction, and focal-adhesion imaging in HUVEC and related endothelial models. (barlow2019buildingbloodvessels—one pages 7-9, kaur2011rhojtclregulatesendothelial pages 2-2, leszczynska2011signallingandfunction pages 129-134, leszczynska2011signallingandfunction pages 134-138) | High for cultured endothelial cells; moderate-to-high for in-vivo vascular morphogenesis. Results can vary with endothelial source, cell density, and migration state. |
| VEGF-A–PlexinD1–Sema3E pathway | RhoJ integrates attractive VEGF-A and repulsive Sema3E cues. In VEGF signaling it supports a VEGFR2–PlexinD1–neuropilin-1 complex, limits degradation of internalized VEGFR2, and prolongs PLCγ, ERK, and AKT signaling. Sema3E releases RhoJ from PlexinD1, promotes cytoskeletal contraction and actin depolymerization, and facilitates VEGFR2-Y1214 and p38 signaling that redirects migration. | Receptor-complex, trafficking, signaling, migration, endothelial-knockout, developmental-retina, and oxygen-induced-retinopathy experiments. (uemura2021rhogtpasesin pages 1-2, uemura2021rhogtpasesin pages 4-7, fukushima2020rhojintegratesattractive pages 10-13) | High for pathway architecture in experimental endothelial systems. Earlier reports disagreed on whether VEGF activates or inactivates RhoJ, likely reflecting timing and context; the nucleotide-state cycle remains more nuanced than a simple on/off response. |
| Cancer and therapy resistance | RHOJ can act in both tumor vasculature and tumor cells. Preclinical evidence links it to tumor angiogenesis and, in melanoma or EMT-like tumor states, tolerance of replication stress and genotoxic therapy through DNA-damage responses and formin-dependent nuclear-actin polymerization. RhoJ loss increased DNA damage, apoptosis, and treatment sensitivity in experimental models. | Endothelial knockout and tumor-vessel studies, melanoma genetic deletion, chemotherapy experiments, and integrated disease-target evidence. Melanoma deletion studies reported reduced tumor growth (p < 0.0001) and lung metastasis (p = 0.003), although metastasis was confounded by lower primary-tumor burden. (OpenTargets Search: -RHOJ, uemura2021rhogtpasesin pages 12-13) | Moderate. Mechanistic evidence is preclinical and tumor-context dependent; human causal genetics and prospective biomarker validation are lacking. |
| Translational status | Proposed applications include disrupting RhoJ–PlexinD1 signaling, sensitizing cancer cells to DNA-damaging therapy, inhibiting pathological retinal or tumor angiogenesis, and using anti-RhoJ antibody-functionalized radiosensitizing nanoparticles. No approved RHOJ-selective therapy or relevant RHOJ clinical trial was identified. | Preclinical retinal and tumor models, nanoparticle-targeting studies, and Open Targets assessment. Open Targets gives neoplasm an overall RHOJ association score of approximately 0.135, driven mainly by literature and animal-model evidence rather than human genetics. (OpenTargets Search: -RHOJ, uemura2021rhogtpasesin pages 12-13, fukushima2020rhojintegratesattractive pages 10-13) | Low-to-moderate translational maturity. RHOJ is a plausible but unvalidated therapeutic target; selectivity against related Cdc42-subfamily GTPases, endothelial safety, delivery, and clinical target engagement remain unresolved. |
Table: Evidence-based functional annotation of human RHOJ, including the family correction, molecular mechanism, localization, endothelial pathways, cancer evidence, and translational maturity. The table distinguishes well-supported conclusions from unresolved or exclusively preclinical findings.
The target is human RHOJ, not a similarly named gene from another organism. RHOJ is enriched in endothelial cells and was historically called TCL or TC10-like because of its close relationship to the Cdc42 branch of the Rho family. Reviews and primary endothelial studies consistently place it in the classical Cdc42 subfamily of Rho GTPases. (barlow2019buildingbloodvessels—one pages 7-9, uemura2021rhogtpasesin pages 1-2, leszczynska2011signallingandfunction pages 34-38)
The supplied domain annotations—P-loop NTPase, small-GTPase nucleotide-binding, Ras-like small-GTPase, and Rho-family small-GTPase—agree with this identification. By contrast, classification as “Rab family” conflicts with both phylogenetic assignment and experimentally established Rho/Cdc42-like biology. This discrepancy should therefore be corrected rather than propagated into downstream annotation.
The accession G3V4H1 appears to be an Ensembl-derived human RHOJ protein record rather than the principal manually reviewed representation. This does not invalidate the gene assignment, but isoform-specific sequence details should be checked against the current canonical human RHOJ entry before designing reagents such as antibodies, CRISPR guides, or structural constructs.
RhoJ is a small guanosine-triphosphate hydrolase, EC 3.6.5.2. Its intrinsic reaction is:
GTP + H₂O → GDP + inorganic phosphate (Pi).
Accordingly, its chemical substrate is GTP, with GDP as the nucleotide product; RhoJ is not a kinase and does not use another protein as a catalytic substrate. Like other Rho-family switches, GDP–GTP exchange changes switch-region conformation and consequently alters effector binding. GTP-bound RhoJ binds CRIB-domain proteins, including reported interactions with PAK-family kinases, WASP, and N-WASP. Other reported partners include CIP4, Par6, p50RhoGAP, PAK1B, and PAK4, although the physiological importance of several of these interactions remains less firmly demonstrated than the endothelial PlexinD1 pathway. (uemura2021rhogtpasesin pages 1-2, leszczynska2011signallingandfunction pages 34-38, uemura2021rhogtpasesin pages 4-7)
A notable biochemical feature reported for RhoJ is relatively rapid spontaneous GDP-to-GTP exchange. Nevertheless, RHOJ-specific kinetic constants and a definitive set of physiologically dominant guanine-nucleotide exchange factors, GTPase-activating proteins, and GDIs remain incompletely characterized. ERG is an established transcriptional promoter of endothelial RHOJ expression, while VEGF/ARHGEF15-related nucleotide-state regulation appears context- and time-dependent. Earlier reports disagreed over whether VEGF acutely activates or inactivates RhoJ, cautioning against a simplistic linear activation model. (barlow2019buildingbloodvessels—one pages 7-9, uemura2021rhogtpasesin pages 12-13)
RHOJ is endothelial enriched, rather than absolutely endothelial exclusive. Human tissue studies detected vascular expression in heart, adrenal gland, lymph node, skeletal muscle, pancreas, placenta, liver, and lung, and in vessels associated with some cancers. Placental pericytes and aortic smooth-muscle cells expressed substantially lower levels than endothelial cells. Expression in embryonic mouse trunk and intersomitic vessels supports a conserved role in developing vasculature. Some non-endothelial tumor cells can also express RHOJ, particularly in mesenchymal or therapy-resistant states. (kaur2011rhojtclregulatesendothelial pages 2-2, leszczynska2011signallingandfunction pages 34-38)
RhoJ acts on the cytoplasmic face of membranes and at cytoskeleton–membrane interfaces. Endogenous endothelial RhoJ has been localized to punctate focal adhesions, colocalizing with vinculin, talin, and phospho-FAK-Y397. Tagged RhoJ has additionally been observed at the dorsal plasma membrane, intracellular vesicles, and early/sorting endosomes. High transient overexpression can broaden apparent localization to endosomes and lysosomes, so these latter observations require caution. (kaur2011rhojtclregulatesendothelial pages 2-2, leszczynska2011signallingandfunction pages 34-38, leszczynska2011signallingandfunction pages 134-138)
This distribution is functionally coherent with RhoJ’s roles in adhesion turnover and membrane trafficking. Rho-family proteins generally associate with membranes through C-terminal CAAX-directed lipid modification. RhoJ has been implicated in trafficking of transferrin receptor, podocalyxin, and α5β1 integrin, although endothelial knockdown produced only a small, statistically non-significant delay in transferrin release and did not measurably change VEGFR2 surface abundance in one study. Thus, RhoJ’s trafficking effects are likely selective for particular cargo and cellular states rather than reflecting a global endocytic defect. (uemura2021rhogtpasesin pages 1-2, leszczynska2011signallingandfunction pages 129-134, fukushima2020rhojintegratesattractive pages 10-13)
RhoJ regulates a connected set of endothelial behaviors:
In HUVECs, RHOJ silencing impaired migration and tubulogenesis and generally increased focal adhesions, stress fibers, myosin signaling, and ROCK-associated contractility. Constitutively active RhoJ promoted migration and excessive sprouting while reducing focal adhesions and contractile structures. These effects were most evident in sparse or actively migrating cells and less consistent in intact confluent monolayers, indicating that RhoJ function depends on cellular state and geometry. (barlow2019buildingbloodvessels—one pages 7-9, kaur2011rhojtclregulatesendothelial pages 2-2, leszczynska2011signallingandfunction pages 129-134, leszczynska2011signallingandfunction pages 134-138)
RhoJ is functionally coupled to, but distinct from, Cdc42, Rac1, and RhoA. RHOJ knockdown did not simply alter their expression. Instead, evidence indicates that RhoJ competes with Cdc42 for shared CRIB-domain effectors and restrains RhoA–ROCK-associated contractility while supporting Rac1/Cdc42-type protrusive and morphogenetic behavior. The GIT–PIX complex has also been implicated in RhoJ-dependent focal-adhesion disassembly. (barlow2019buildingbloodvessels—one pages 7-9, uemura2021rhogtpasesin pages 4-7, uemura2021rhogtpasesin pages 12-13)
The most precise contemporary model is that RhoJ integrates attractive VEGF-A and repulsive Sema3E cues through PlexinD1.
Following VEGF-A stimulation, RhoJ supports assembly of a VEGFR2–PlexinD1–neuropilin-1 holoreceptor complex. This complex protects internalized VEGFR2 from degradation and prolongs downstream PLCγ, ERK, and AKT signaling, thereby maintaining forward endothelial migration. After conversion toward the GDP-bound state, RhoJ shifts its association from PlexinD1 toward VEGFR2, contributing to eventual signal termination. (uemura2021rhogtpasesin pages 1-2, fukushima2020rhojintegratesattractive pages 10-13)
GTP-bound RhoJ associates with the intracellular domain of PlexinD1. Sema3E stimulation releases RhoJ, allowing it to compete with Cdc42 for shared effectors and drive actin depolymerization, filopodial retraction, and contraction. PlexinD1-associated RhoJ also facilitates Sema3E-induced PlexinD1–VEGFR2 association, VEGFR2 transphosphorylation at Y1214, and p38 MAPK activation, producing reverse or repulsive migration. (uemura2021rhogtpasesin pages 1-2, uemura2021rhogtpasesin pages 4-7, fukushima2020rhojintegratesattractive pages 10-13)
This model explains how one small GTPase can regulate apparently opposing behaviors: its biological output depends on nucleotide state, binding partner, receptor complex, intracellular position, and stimulus timing rather than merely on total expression.
Endothelial RhoJ is required for efficient vascular morphogenesis but is not simply a universal vessel-maintenance factor. Genetic deficiency delays developmental vascular growth and disrupts directional positioning of endothelial cells. In oxygen-induced retinopathy, endothelial RhoJ deletion suppresses aberrant neovascularization, supporting a relatively greater requirement in actively angiogenic or pathological endothelium than in established quiescent vessels. (uemura2021rhogtpasesin pages 1-2, fukushima2020rhojintegratesattractive pages 10-13)
These data underpin expert proposals that RhoJ may be useful for treating retinal neovascular disease. However, this remains a preclinical concept. The same pathway can also support physiological revascularization after ischemia, so inhibition could potentially suppress desirable repair as well as pathological vessel growth. Therapeutic design would therefore require disease- and tissue-selective delivery or transient pathway modulation.
RHOJ can contribute to cancer through two distinguishable compartments.
RhoJ is enriched in angiogenic tumor vessels and supports endothelial migration, tube formation, matrix remodeling, and vessel maintenance. RhoJ-deficient mice show reduced tumor vascular density and tumor growth, giving rise to the proposal that RhoJ may offer greater vascular selectivity than broadly inhibiting ubiquitous Rho-family proteins. (OpenTargets Search: -RHOJ, uemura2021rhogtpasesin pages 12-13)
In melanoma and EMT-like tumor-cell states, RHOJ supports tolerance to replication stress and DNA-damaging chemotherapy. Mechanistic evidence links RhoJ to activation of dormant replication origins, continued DNA synthesis following cisplatin/5-fluorouracil exposure, DNA-damage repair, and formin-dependent nuclear-actin polymerization. RhoJ depletion increases γ-H2AX, apoptosis, and chemotherapy sensitivity. In cited melanoma models, deletion significantly inhibited tumor growth (p < 0.0001) and reduced lung metastasis (p = 0.003), although the metastasis result was partly confounded by lower primary-tumor burden. Rhoj-knockout tumors reportedly remained stable during three weeks of cisplatin/5-FU treatment. (OpenTargets Search: -RHOJ)
These findings suggest a potentially valuable dual action—simultaneously weakening tumor cells and their vasculature—but causal human evidence remains limited. Open Targets gives the RHOJ–neoplasm association an overall score of approximately 0.135; the signal is driven largely by literature and animal models, with no corresponding human genetic-association evidence in that entry. Database links to preeclampsia, endometriosis, liver disease, and myasthenia gravis should be treated as hypothesis-generating associations, not established RHOJ functions. (OpenTargets Search: -RHOJ)
The core mechanistic advances still derive primarily from 2011–2021 work; genuinely RHOJ-focused publications in 2023–2024 were sparse in the retrieved literature. A January 2024 medicinal-chemistry review discussed emerging pyrimidine-based CDC42/RHOJ inhibitor classes, indicating active interest in chemical modulation, but the available evidence did not establish a clinically validated, RHOJ-selective molecule.
Present implementations are therefore experimental rather than clinical:
No approved RHOJ-selective medicine, validated clinical biomarker implementation, or relevant RHOJ-directed clinical trial was identified. Accordingly, phrases such as “therapeutic target” should currently be understood as preclinical target rationale, not evidence of clinical utility.
The strongest annotation is that RhoJ is an endothelial-enriched spatiotemporal regulator of receptor trafficking and cytoskeletal organization, rather than a conventional downstream enzyme with a narrow protein substrate. Its distinctive contribution is to coordinate extracellular guidance information with adhesion turnover and receptor lifetime, allowing endothelial cells to choose direction while migrating through heterogeneous VEGF and semaphorin fields. (uemura2021rhogtpasesin pages 1-2, fukushima2020rhojintegratesattractive pages 10-13)
Evidence is strongest for cultured human endothelial phenotypes and genetically manipulated mouse vascular models. Confidence is moderate for individual effector assignments beyond PlexinD1 and CRIB-domain proteins, and lower for human disease causality or therapeutic efficacy. Important unresolved questions include RHOJ-specific nucleotide-cycle kinetics, its dominant physiological GEFs/GAPs/GDIs, isoform-specific behavior, quantitative compartment-resolved activity in living human tissues, and whether direct inhibition can achieve useful selectivity over Cdc42 and RHOQ without impairing normal vascular repair.
References
(OpenTargets Search: -RHOJ): Open Targets Query (-RHOJ, 5 results). Buniello, A. et al. (2025). Open Targets Platform: facilitating therapeutic hypotheses building in drug discovery. Nucleic Acids Research.
(barlow2019buildingbloodvessels—one pages 7-9): Haley Rose Barlow and Ondine Cleaver. Building blood vessels—one rho gtpase at a time. Cells, 8:545, Jun 2019. URL: https://doi.org/10.3390/cells8060545, doi:10.3390/cells8060545. This article has 44 citations.
(uemura2021rhogtpasesin pages 1-2): Akiyoshi Uemura and Yoko Fukushima. Rho gtpases in retinal vascular diseases. International Journal of Molecular Sciences, 22:3684, Apr 2021. URL: https://doi.org/10.3390/ijms22073684, doi:10.3390/ijms22073684. This article has 25 citations.
(kaur2011rhojtclregulatesendothelial pages 2-2): Sukhbir Kaur, Katarzyna Leszczynska, Sabu Abraham, Margherita Scarcia, Sabina Hiltbrunner, Christopher J. Marshall, Georgia Mavria, Roy Bicknell, and Victoria L. Heath. Rhoj/tcl regulates endothelial motility and tube formation and modulates actomyosin contractility and focal adhesion numbers. Arteriosclerosis, Thrombosis, and Vascular Biology, 31:657-664, Mar 2011. URL: https://doi.org/10.1161/atvbaha.110.216341, doi:10.1161/atvbaha.110.216341. This article has 94 citations and is from a domain leading peer-reviewed journal.
(fukushima2020rhojintegratesattractive pages 10-13): Yoko Fukushima, Koichi Nishiyama, Hiroshi Kataoka, Marcus Fruttiger, Shigetomo Fukuhara, Kohji Nishida, Naoki Mochizuki, Hiroki Kurihara, Shin‐Ichi Nishikawa, and Akiyoshi Uemura. Rhoj integrates attractive and repulsive cues in directional migration of endothelial cells. The EMBO Journal, Apr 2020. URL: https://doi.org/10.15252/embj.2019102930, doi:10.15252/embj.2019102930. This article has 37 citations.
(leszczynska2011signallingandfunction pages 34-38): K Leszczynska. Signalling and function of the small rho gtpase rhoj in endothelial cells. Unknown journal, 2011.
(uemura2021rhogtpasesin pages 4-7): Akiyoshi Uemura and Yoko Fukushima. Rho gtpases in retinal vascular diseases. International Journal of Molecular Sciences, 22:3684, Apr 2021. URL: https://doi.org/10.3390/ijms22073684, doi:10.3390/ijms22073684. This article has 25 citations.
(leszczynska2011signallingandfunction pages 134-138): K Leszczynska. Signalling and function of the small rho gtpase rhoj in endothelial cells. Unknown journal, 2011.
(leszczynska2011signallingandfunction pages 129-134): K Leszczynska. Signalling and function of the small rho gtpase rhoj in endothelial cells. Unknown journal, 2011.
(uemura2021rhogtpasesin pages 12-13): Akiyoshi Uemura and Yoko Fukushima. Rho gtpases in retinal vascular diseases. International Journal of Molecular Sciences, 22:3684, Apr 2021. URL: https://doi.org/10.3390/ijms22073684, doi:10.3390/ijms22073684. This article has 25 citations.