{"gene":"RAP2B","run_date":"2026-06-10T06:43:36","timeline":{"discoveries":[{"year":1990,"finding":"RAP2B encodes a ~22 kDa GTP-binding protein expressed in human platelets; bacterially expressed RAP2B specifically binds GTP on blots, and unlike RAP1A/RAP1B it is not phosphorylated by the catalytic subunit of cAMP-dependent protein kinase.","method":"cDNA cloning, bacterial expression, GTP-blotting, in vitro kinase assay","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro biochemical assays with purified recombinant protein and direct kinase assay; foundational characterization replicated in subsequent papers","pmids":["2118648"],"is_preprint":false},{"year":1990,"finding":"Purified recombinant RAP2B binds both GTP and GDP in a Mg2+-dependent fashion, with higher relative affinity for GTP than GDP; a polyclonal antiserum against recombinant RAP2B recognizes a ~21 kDa protein in platelet membrane fractions and immunoprecipitates RAP2B complexed with GTP or GDP.","method":"In vitro GTP/GDP binding assay, immunoprecipitation, Western blot","journal":"Biochemical and biophysical research communications","confidence":"High","confidence_rationale":"Tier 1 / Strong — direct in vitro nucleotide binding with purified protein; consistent with and replicated by the founding PNAS paper","pmids":["2118346"],"is_preprint":false},{"year":1992,"finding":"A partially purified protein from bovine brain membranes stimulates the GTPase activity of RAP2B (a RAP2B-GAP); this GAP activity is immunologically distinct from RAP1-GAP and RAS-GAP, yet shows limited stimulatory activity toward RAP1, indicating it is a distinct GAP for the RAP2 subfamily.","method":"Partial protein purification from bovine brain membranes, GTPase activity assay, immunoblotting with specific antibodies","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — direct enzymatic assay with partially purified material, single lab, protein not fully characterized","pmids":["1472043"],"is_preprint":false},{"year":1993,"finding":"RAP2B translocates from the Triton X-100-soluble fraction to the cytoskeleton upon platelet aggregation induced by thrombin, thromboxane analogue, or thapsigargin; translocation depends on platelet aggregation and requires fibrinogen binding to glycoprotein IIb-IIIa.","method":"Subcellular fractionation (Triton X-100 lysis, differential centrifugation), Western blot with specific antiserum","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Strong — direct fractionation experiment with multiple agonists and pharmacological inhibitors; replicated in subsequent studies","pmids":["8356055"],"is_preprint":false},{"year":1993,"finding":"Microinjection of RAP2B protein or mRNA into Xenopus oocytes induces rearrangement of pigment granules ('mottling'); this effect requires membrane association via post-translational processing of the C-terminal CAAX motif, as a Cys→Ser mutation in the CAAX box prevents membrane association and mottling. The effect is blocked by the cytoskeletal reagent phalloidin.","method":"Xenopus oocyte microinjection, site-directed mutagenesis, membrane fractionation","journal":"The Biochemical journal","confidence":"High","confidence_rationale":"Tier 1 / Moderate — reconstitution in intact cells with mutagenesis validation and pharmacological controls; single lab but multiple orthogonal approaches","pmids":["7684898"],"is_preprint":false},{"year":1994,"finding":"Translocation of RAP2B to the platelet cytoskeleton requires agonist-induced actin polymerization and is dependent on glycoprotein IIb-IIIa (the fibrinogen receptor); platelets from Glanzmann thrombasthenia patients lacking GPIIb-IIIa fail to incorporate RAP2B into the cytoskeleton. RAP2B and GPIIb-IIIa co-translocate to the cytoskeleton during aggregation.","method":"Platelet fractionation, blocking antibodies against GPIIb-IIIa, use of Glanzmann thrombasthenia patient platelets, Western blot","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic (patient cells) and antibody-blocking evidence combined; replicated from prior fractionation study","pmids":["8183895"],"is_preprint":false},{"year":1999,"finding":"von Willebrand factor (vWF) stimulation of human platelets induces rapid translocation of RAP2B to the cytoskeleton via a pathway requiring GPIb, FcγRII receptor-mediated tyrosine phosphorylation, and the kinase pp72(syk); translocation is blocked by genistein (tyrosine kinase inhibitor), cAMP-elevating agents, and anti-FcγRII antibody.","method":"Platelet fractionation, blocking antibodies (anti-GPIb, anti-FcγRII, RGDS peptide), pharmacological inhibitors (genistein, cytochalasin D, cAMP agents), Western blot, identification of substrates (syk, PLCγ2, SHIP)","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple blocking strategies, receptor-specific antibodies, and substrate identification in primary human cells","pmids":["10224142"],"is_preprint":false},{"year":2002,"finding":"RAP2B mediates stimulation of phospholipase C-epsilon (PLC-ε) downstream of the M3 muscarinic acetylcholine receptor; this occurs via a cAMP/Epac1 pathway: M3 mAChR activates adenylyl cyclase, raises cAMP, activates Epac1 (a Rap GEF), which loads GTP onto RAP2B, which then stimulates PLC-ε to increase [Ca2+]i. Dominant-negative RAP2B (but not dominant-negative Rac1, Ras, RalA, Rap1A, or Rap2A) suppresses M3-mediated PLC stimulation.","method":"Overexpression/dominant-negative constructs, adenylyl cyclase inhibitor (dd-Ado), clostridial toxin inactivation of Ras-related GTPases, GTP-loading assay for RAP2B, PLC activity assay, Ca2+ measurement in HEK-293 cells","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal tools (dominant-negatives, pharmacological inhibitors, GTP-loading assay) in one study with specificity controls comparing multiple GTPases","pmids":["11877431"],"is_preprint":false},{"year":2004,"finding":"EGF receptor activates RAP2B via c-Src-dependent tyrosine phosphorylation of RasGRP3 (a Ca2+/diacylglycerol-regulated GEF); activated RAP2B then binds directly to PLC-ε and drives its translocation to the plasma membrane, leading to PLC/Ca2+ signaling. GTP loading of RAP2B by EGF requires intracellular Ca2+ and lipase-active PLC-γ1 (upstream), but not PLC-ε.","method":"Dominant-negative RAP2B expression, clostridial toxin treatment, GTP-loading pull-down assay, co-immunoprecipitation of RAP2B with PLC-ε, confocal imaging of PLC-ε translocation, c-Src inhibition, intracellular Ca2+ chelation, in HEK-293 cells","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — direct binding of RAP2B to PLC-ε by Co-IP, translocation by imaging, GTP-loading, and multiple mechanistic interventions in one rigorous study","pmids":["15143162"],"is_preprint":false},{"year":2004,"finding":"In human platelets, thrombin (via G-protein-coupled receptors) and convulxin (via GPVI/tyrosine kinase pathway) both induce rapid GTP loading of RAP2B. Thrombin-induced RAP2B activation is partially dependent on secreted ADP acting through the Gi-coupled P2Y12 receptor and fully dependent on PI3-kinase activity. Convulxin-induced activation requires PKC and is PI3K-independent. Both are regulated by intracellular Ca2+. cAMP-elevating agents do not activate RAP2B.","method":"GTP-loading assay (pull-down with RAP2B-binding domain), pharmacological inhibitors (PI3K inhibitor, PKC inhibitor, ADP scavenger, Ca2+ chelator), P2Y12 antagonist, in primary human platelets","journal":"Journal of thrombosis and haemostasis","confidence":"High","confidence_rationale":"Tier 2 / Strong — direct GTP-loading assays in primary cells with multiple specific pharmacological interventions dissecting upstream pathway","pmids":["15613030"],"is_preprint":false},{"year":2008,"finding":"RAP2B (but not RAP1B) constitutively associates with lipid rafts in human platelets; this association is mediated by palmitoylation at Cys176 and Cys177 (but not at the CAAX motif). Disruption of lipid raft association by cholesterol depletion impairs agonist-induced RAP2B activation and inhibits platelet aggregation.","method":"Lipid raft isolation (detergent-resistant membrane fractionation), [3H]palmitate metabolic labeling, site-directed mutagenesis (C176S, C177S, CAAX deletion) in transfected HEK293T cells and primary platelets, cholesterol depletion, GTP-loading assay, platelet aggregation assay","journal":"Cellular signalling","confidence":"High","confidence_rationale":"Tier 1 / Moderate — mutagenesis, metabolic labeling, and functional assays in one study with two cell systems; single lab but multiple orthogonal methods","pmids":["18582561"],"is_preprint":false},{"year":2013,"finding":"RAP2B is a direct transcriptional target of p53 that mediates a pro-survival function after DNA damage; p53 binds the RAP2B promoter upon DNA damage and activates its transcription. siRNA knockdown of RAP2B sensitizes cells to DNA damage-induced apoptosis in a p53-dependent manner.","method":"Integrative genomic analysis, chromatin immunoprecipitation (p53 binding to RAP2B promoter), siRNA knockdown, apoptosis assays, anchorage-independent growth assay","journal":"Cell cycle (Georgetown, Tex.)","confidence":"High","confidence_rationale":"Tier 2 / Moderate — ChIP for direct promoter binding plus functional siRNA knockdown with p53-dependency controls; single lab with two orthogonal methods","pmids":["23535297"],"is_preprint":false},{"year":2015,"finding":"RAP2B promotes breast cancer cell proliferation, migration, and invasion by elevating intracellular calcium levels and promoting ERK1/2 phosphorylation; calcium chelator BAPTA/AM and MEK inhibitor U0126 reverse RAP2B-induced ERK1/2 phosphorylation, placing RAP2B upstream of a Ca2+/ERK1/2 axis.","method":"siRNA knockdown and overexpression, CCK-8 proliferation assay, transwell assay, flow cytometry (calcium measurement), Western blot (ERK1/2 phosphorylation), pharmacological inhibitors (BAPTA/AM, U0126)","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple assays with pharmacological pathway dissection; single lab but two orthogonal functional readouts","pmids":["26201295"],"is_preprint":false},{"year":2015,"finding":"RAP2B inhibits cell spreading by disrupting actin dynamics in a CAAX-dependent manner; expression of RAP2B is induced by nocodazole in a p53-dependent manner, and a C180A CAAX mutant of RAP2B does not inhibit cell spreading, demonstrating that membrane targeting is required for cytoskeletal effects.","method":"Western blot, immunofluorescence, overexpression and knockdown, site-directed mutagenesis (C180A), nocodazole treatment","journal":"Journal of cancer research and clinical oncology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — mutagenesis combined with imaging and knockdown; single lab with two orthogonal approaches","pmids":["25762091"],"is_preprint":false},{"year":2017,"finding":"p53 upregulates the RAP2B–PLC-ε–IP3–Ca2+ pathway and thereby inhibits starvation-induced autophagy; p53 induction increases intracellular IP3 and Ca2+ levels and decreases LC3 levels through RAP2B, establishing RAP2B as a mediator of p53-dependent autophagy inhibition.","method":"Microarray-based target identification, overexpression/knockdown, measurement of IP3, Ca2+, and LC3 levels by Western blot and biochemical assays","journal":"Oncotarget","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct measurement of IP3, Ca2+, and autophagy markers downstream of RAP2B; single lab, two orthogonal readouts","pmids":["29029384"],"is_preprint":false},{"year":2016,"finding":"RAP2B promotes prostate cancer cell migration and invasion via FAK-dependent signaling; elevated RAP2B increases FAK phosphorylation, and FAK-specific inhibitor PF-573228 abolishes RAP2B-induced FAK phosphorylation and the resulting migration/invasion phenotype.","method":"siRNA knockdown and overexpression, CCK-8, transwell assay, Western blot (p-FAK), pharmacological inhibitor (PF-573228), xenograft in vivo","journal":"Medical oncology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — pathway placement via specific FAK inhibitor rescue; single lab with functional and in vivo validation","pmids":["27154636"],"is_preprint":false},{"year":2019,"finding":"RAP2B knockdown in glioma cells reduces expression levels of NF-κB, MMP-2, and MMP-9, and inhibits cell adhesion, proliferation, migration, and invasion, placing RAP2B upstream of the NF-κB pathway in glioma.","method":"siRNA knockdown, Western blot (NF-κB, MMP-2, MMP-9), CCK-8, wound healing, transwell invasion assay","journal":"Journal of neuro-oncology","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — knockdown with defined molecular readouts; single lab, single method per pathway node","pmids":["30997639"],"is_preprint":false},{"year":2017,"finding":"RAP2B promotes renal cell carcinoma angiogenesis in vitro and in vivo via activation of the PI3K/AKT signaling pathway, leading to upregulation of VEGF; this was demonstrated by ELISA measurement of VEGF, HUVEC growth, and tube formation assays with RAP2B knockdown/overexpression.","method":"siRNA knockdown and overexpression, Western blot, qPCR, ELISA (VEGF), HUVEC growth assay, endothelial tube formation assay, in vivo tumor model","journal":"Tumour biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple functional angiogenesis assays with pathway marker measurement; single lab","pmids":["28691643"],"is_preprint":false},{"year":2019,"finding":"Active RAP2B (wild-type) inhibits development of the Coxiella burnetii replicative vacuole (CRV) and impairs both homotypic (phagosome–CRV) and heterotypic (endosome/lysosome–CRV) fusion events; this effect is dependent on RAP2B GTPase activity (inactive ΔAAX mutant has no effect). RAP2B overexpression markedly decreases the v-SNARE Vamp7 levels, suggesting a mechanism involving SNARE downregulation.","method":"Transient overexpression of wild-type vs. inactive RAP2B mutant, fluorescence microscopy of vacuole size, fusion assays, Western blot (Vamp7)","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — WT vs. inactive mutant comparison with mechanistic readout (SNARE levels and fusion events); single lab, multiple assays","pmids":["30763357"],"is_preprint":false},{"year":2024,"finding":"RAP2B is S-palmitoylated at Cys176 and Cys177 at the C-terminus, which is required for its plasma membrane localization; ABHD17a is identified as the depalmitoylating enzyme for RAP2B, and its PI3K-mediated phosphorylation by EGFR/PI3K signaling regulates ABHD17a activity and thus RAP2B palmitoylation. Mutation of C176/C177 or a blocking peptide targeting these sites causes cytosolic relocation of RAP2B and suppresses CRC cell migration/invasion and metastasis.","method":"Site-directed mutagenesis (C176/C177), palmitoylation assays, Co-IP identifying ABHD17a, pharmacological inhibition of PI3K, blocking peptide, xenograft metastasis model","journal":"Cell death & disease","confidence":"High","confidence_rationale":"Tier 1 / Moderate — mutagenesis, identification of depalmitoylase, upstream kinase regulation, and in vivo functional validation in one study; single lab but multiple orthogonal methods","pmids":["39277583"],"is_preprint":false},{"year":2025,"finding":"Intestine-specific knockout of RAP2B suppresses CRC initiation and progression in vivo; mechanistically, RAP2B interacts with plectin and enhances plectin expression, which inhibits plectin-mediated F-actin assembly, leading to cytoskeletal remodeling that promotes tumorigenesis and metastasis.","method":"Intestine-specific knockout mouse model, co-immunoprecipitation (RAP2B–plectin interaction), Western blot (plectin, F-actin markers), in vivo tumor growth and metastasis assays, human CRC tissue correlation","journal":"Cell death & disease","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic knockout in vivo combined with Co-IP for direct binding partner and mechanistic cytoskeletal readout; single lab but multiple orthogonal approaches","pmids":["40223002"],"is_preprint":false},{"year":2009,"finding":"RAP2B overexpression in Rat1 fibroblasts induces oncogenic transformation foci and activates the NF-κB pathway more than 3-fold as measured by reporter gene assay.","method":"Stable transfection in Rat1 cells, colony/focus formation assay, NF-κB reporter gene assay","journal":"Zhongguo fei ai za zhi (Chinese journal of lung cancer)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct functional transformation assay plus reporter assay for pathway activation; single lab, two orthogonal readouts","pmids":["20719111"],"is_preprint":false},{"year":2025,"finding":"RAP2B overexpression activates the PI3K/AKT signaling pathway and confers resistance to cetuximab in colorectal cancer cells; RAP2B knockdown inhibits PI3K/AKT signaling, reduces cell proliferation, enhances apoptosis, and restores cetuximab sensitivity both in vitro and in vivo.","method":"Knockdown and overexpression, Western blot (PI3K/AKT pathway markers), cell proliferation, apoptosis assays, xenograft in vivo","journal":"Biological procedures online","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — bidirectional manipulation with pathway readout and in vivo confirmation; single lab","pmids":["41094393"],"is_preprint":false}],"current_model":"RAP2B is a Ras-family small GTPase that cycles between GDP-bound (inactive) and GTP-bound (active) states; it is post-translationally processed at its C-terminal CAAX motif and further palmitoylated at Cys176/Cys177 (with ABHD17a as the depalmitoylase and EGFR/PI3K regulating this cycle), which controls its plasma membrane and lipid-raft targeting. Active RAP2B is loaded with GTP downstream of multiple receptors — GPCRs, receptor tyrosine kinases (EGFR via c-Src/RasGRP3), and GPVI — and directly binds and translocates PLC-ε to the plasma membrane, stimulating IP3/Ca2+ signaling; it also translocates to the platelet cytoskeleton in a GPIIb-IIIa- and actin-polymerization-dependent manner during aggregation. As a direct transcriptional target of p53, RAP2B counteracts DNA-damage-induced apoptosis, inhibits autophagy via the PLCε–IP3–Ca2+ axis, and regulates cytoskeletal dynamics by interacting with plectin to suppress F-actin assembly; in multiple cancer contexts it drives proliferation, migration, and invasion through ERK1/2, PI3K/AKT, FAK, and NF-κB signaling pathways."},"narrative":{"mechanistic_narrative":"RAP2B is a Ras-family small GTPase, originally characterized in human platelets, that cycles between GDP- and GTP-bound states and binds guanine nucleotides in a Mg2+-dependent manner with preference for GTP [PMID:2118648, PMID:2118346]. Its membrane targeting depends on two layers of C-terminal processing: CAAX-motif prenylation, which is required for membrane association and downstream cellular effects [PMID:7684898, PMID:25762091], and S-palmitoylation at Cys176/Cys177, which directs RAP2B to lipid rafts and the plasma membrane; this palmitoylation cycle is controlled by the depalmitoylase ABHD17a under EGFR/PI3K regulation [PMID:18582561, PMID:39277583]. RAP2B is loaded with GTP downstream of diverse receptors — GPCRs via a cAMP/Epac1 route from the M3 muscarinic receptor, the EGF receptor via c-Src-dependent phosphorylation of the GEF RasGRP3, and platelet receptors (GPCRs/P2Y12, GPVI, and the GPIb–FcγRII–Syk axis) [PMID:11877431, PMID:15143162, PMID:15613030, PMID:10224142]. A central effector function is direct binding to phospholipase C-ε and driving its translocation to the plasma membrane, thereby stimulating IP3/Ca2+ signaling [PMID:15143162]. During platelet aggregation RAP2B translocates to the cytoskeleton in a manner dependent on actin polymerization and fibrinogen binding to glycoprotein IIb-IIIa [PMID:8356055, PMID:8183895]. RAP2B is a direct transcriptional target of p53 that promotes survival after DNA damage and suppresses starvation-induced autophagy through the PLC-ε–IP3–Ca2+ axis [PMID:23535297, PMID:29029384]. In multiple cancers RAP2B drives proliferation, migration, invasion, and angiogenesis through Ca2+/ERK1/2, PI3K/AKT (including VEGF induction and cetuximab resistance), FAK, and NF-κB signaling [PMID:26201295, PMID:28691643, PMID:27154636, PMID:30997639, PMID:41094393], and it remodels the cytoskeleton by interacting with plectin to modulate F-actin assembly [PMID:40223002].","teleology":[{"year":1990,"claim":"Established that RAP2B is a genuine GTP-binding protein distinct from the related RAP1 proteins, defining it as a candidate signaling GTPase in platelets.","evidence":"cDNA cloning, bacterial expression, GTP-blotting and kinase assay; in vitro GTP/GDP binding and immunoprecipitation from platelet membranes","pmids":["2118648","2118346"],"confidence":"High","gaps":["No physiological GEF or receptor input identified at this stage","Cellular function unknown"]},{"year":1992,"claim":"Identified a RAP2-subfamily-specific GAP, addressing how RAP2B is switched off and distinguishing its regulation from RAP1/RAS.","evidence":"Partial protein purification from bovine brain membranes with GTPase assays and antibody discrimination","pmids":["1472043"],"confidence":"Medium","gaps":["GAP protein not molecularly identified or cloned","Single lab, partially purified material"]},{"year":1993,"claim":"Linked RAP2B to cytoskeletal dynamics by showing it translocates to the cytoskeleton on platelet activation and induces cytoskeleton-dependent rearrangements requiring CAAX processing.","evidence":"Platelet subcellular fractionation with multiple agonists; Xenopus oocyte microinjection with CAAX mutagenesis and phalloidin block","pmids":["8356055","7684898"],"confidence":"High","gaps":["Molecular effectors of cytoskeletal effect not identified","Direct cytoskeletal binding partner unknown"]},{"year":1994,"claim":"Defined the receptor requirement for cytoskeletal translocation, showing it depends on GPIIb-IIIa and actin polymerization, using genetic (Glanzmann) evidence.","evidence":"Platelet fractionation with blocking antibodies and Glanzmann thrombasthenia patient platelets","pmids":["8183895"],"confidence":"High","gaps":["Mechanistic link between GPIIb-IIIa engagement and RAP2B recruitment unresolved"]},{"year":1999,"claim":"Mapped a distinct receptor pathway (vWF/GPIb–FcγRII–Syk) driving RAP2B cytoskeletal translocation, broadening the upstream signaling inputs.","evidence":"Platelet fractionation with receptor-blocking antibodies, tyrosine kinase inhibitors, and substrate identification","pmids":["10224142"],"confidence":"High","gaps":["Direct GEF connecting Syk signaling to RAP2B not identified"]},{"year":2002,"claim":"Identified PLC-ε as a RAP2B effector and an Epac1/cAMP route for its activation, establishing RAP2B as a specific transducer to Ca2+ signaling downstream of GPCRs.","evidence":"Dominant-negative and toxin tools, GTP-loading and PLC/Ca2+ assays in HEK-293 cells with multi-GTPase specificity controls","pmids":["11877431"],"confidence":"High","gaps":["Direct RAP2B–PLC-ε binding not yet demonstrated at this stage"]},{"year":2004,"claim":"Demonstrated direct RAP2B–PLC-ε binding and PLC-ε translocation, and placed RAP2B downstream of EGFR via c-Src/RasGRP3, providing the core effector mechanism.","evidence":"Co-IP, confocal translocation imaging, GTP-loading, dominant-negative and c-Src inhibition in HEK-293; GTP-loading assays in platelets dissecting thrombin vs convulxin inputs","pmids":["15143162","15613030"],"confidence":"High","gaps":["Structural basis of RAP2B–PLC-ε interaction unknown","GEF identity in platelet pathways not resolved"]},{"year":2008,"claim":"Showed that palmitoylation at Cys176/Cys177 targets RAP2B to lipid rafts and is required for its agonist-induced activation, defining a membrane-microdomain control point.","evidence":"Detergent-resistant membrane fractionation, [3H]palmitate labeling, mutagenesis, cholesterol depletion, and aggregation assays in platelets and HEK293T","pmids":["18582561"],"confidence":"High","gaps":["Enzymes controlling the palmitoylation cycle not yet identified"]},{"year":2013,"claim":"Placed RAP2B in the p53 network as a direct transcriptional target mediating survival after DNA damage, connecting it to tumor-relevant signaling.","evidence":"ChIP for p53 binding to the RAP2B promoter plus siRNA knockdown and apoptosis assays with p53-dependency controls","pmids":["23535297"],"confidence":"High","gaps":["Downstream survival effectors of RAP2B in this context not defined"]},{"year":2017,"claim":"Connected the p53–RAP2B axis to autophagy, showing RAP2B mediates p53-dependent autophagy inhibition through PLC-ε–IP3–Ca2+.","evidence":"Microarray target identification, overexpression/knockdown, and measurement of IP3, Ca2+, and LC3","pmids":["29029384"],"confidence":"Medium","gaps":["Single lab","Link to canonical autophagy machinery beyond LC3 not detailed"]},{"year":2019,"claim":"Extended RAP2B function to membrane trafficking, showing active RAP2B impairs Coxiella vacuole biogenesis and reduces the v-SNARE Vamp7.","evidence":"WT vs inactive ΔAAX mutant overexpression, vacuole imaging, fusion assays, and Vamp7 immunoblot","pmids":["30763357"],"confidence":"Medium","gaps":["Mechanism linking RAP2B to Vamp7 levels unclear","Physiological (non-infection) trafficking role untested"]},{"year":2024,"claim":"Resolved the regulated palmitoylation cycle, identifying ABHD17a as the RAP2B depalmitoylase under EGFR/PI3K control and showing membrane targeting drives metastasis.","evidence":"Mutagenesis, palmitoylation assays, Co-IP of ABHD17a, PI3K inhibition, blocking peptide, and xenograft metastasis model","pmids":["39277583"],"confidence":"High","gaps":["Palmitoyl-acyltransferase that adds the modification not identified"]},{"year":2025,"claim":"Provided in vivo genetic proof that RAP2B drives colorectal tumorigenesis and identified plectin as a binding partner mediating its cytoskeletal effects, while reinforcing PI3K/AKT-dependent therapy resistance.","evidence":"Intestine-specific knockout mice, Co-IP of RAP2B–plectin, F-actin readouts, metastasis assays; bidirectional manipulation with PI3K/AKT readout and cetuximab-resistance xenografts","pmids":["40223002","41094393"],"confidence":"High","gaps":["How RAP2B nucleotide state controls plectin binding/F-actin is undefined","Relation between plectin axis and PLC-ε/Ca2+ signaling unresolved"]},{"year":null,"claim":"The integrated upstream GEF network and the structural/nucleotide-state logic coupling RAP2B to its distinct effectors (PLC-ε, plectin, SNARE machinery) across cell types remain unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No unified model of which GEF acts in which receptor context","No structural data on effector selection","Tissue-specific GAP regulation uncharacterized"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0003924","term_label":"GTPase activity","supporting_discovery_ids":[0,1,2,18]},{"term_id":"GO:0060089","term_label":"molecular transducer activity","supporting_discovery_ids":[7,8,9]},{"term_id":"GO:0008092","term_label":"cytoskeletal protein binding","supporting_discovery_ids":[20]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[8,10,19]},{"term_id":"GO:0005856","term_label":"cytoskeleton","supporting_discovery_ids":[3,5]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[19]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[7,8,12,17]},{"term_id":"R-HSA-109582","term_label":"Hemostasis","supporting_discovery_ids":[3,5,6,9]},{"term_id":"R-HSA-9612973","term_label":"Autophagy","supporting_discovery_ids":[14]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[12,15,16,17,22]}],"complexes":[],"partners":["PLCE1","RASGRP3","ABHD17A","PLEC","ITGB3"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P61225","full_name":"Ras-related protein Rap-2b","aliases":[],"length_aa":183,"mass_kda":20.5,"function":"Small GTP-binding protein which cycles between a GDP-bound inactive and a GTP-bound active form. Involved in EGFR and CHRM3 signaling pathways through stimulation of PLCE1. May play a role in cytoskeletal rearrangements and regulate cell spreading through activation of the effector TNIK. May regulate membrane vesiculation in red blood cells","subcellular_location":"Recycling endosome membrane","url":"https://www.uniprot.org/uniprotkb/P61225/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/RAP2B","classification":"Not Classified","n_dependent_lines":5,"n_total_lines":1208,"dependency_fraction":0.0041390728476821195},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/RAP2B","total_profiled":1310},"omim":[{"mim_id":"611418","title":"SMALL G PROTEIN SIGNALING MODULATOR 2; SGSM2","url":"https://www.omim.org/entry/611418"},{"mim_id":"611417","title":"SMALL G PROTEIN SIGNALING MODULATOR 1; SGSM1","url":"https://www.omim.org/entry/611417"},{"mim_id":"610440","title":"SMALL G PROTEIN SIGNALING MODULATOR 3; SGSM3","url":"https://www.omim.org/entry/610440"},{"mim_id":"609530","title":"RAP GUANINE NUCLEOTIDE EXCHANGE FACTOR 2; RAPGEF2","url":"https://www.omim.org/entry/609530"},{"mim_id":"608414","title":"PHOSPHOLIPASE C, EPSILON-1; PLCE1","url":"https://www.omim.org/entry/608414"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in many","driving_tissues":[],"url":"https://www.proteinatlas.org/search/RAP2B"},"hgnc":{"alias_symbol":[],"prev_symbol":[]},"alphafold":{"accession":"P61225","domains":[{"cath_id":"3.40.50.300","chopping":"1-167","consensus_level":"high","plddt":95.6579,"start":1,"end":167}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P61225","model_url":"https://alphafold.ebi.ac.uk/files/AF-P61225-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P61225-F1-predicted_aligned_error_v6.png","plddt_mean":90.62},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=RAP2B","jax_strain_url":"https://www.jax.org/strain/search?query=RAP2B"},"sequence":{"accession":"P61225","fasta_url":"https://rest.uniprot.org/uniprotkb/P61225.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P61225/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P61225"}},"corpus_meta":[{"pmid":"26201295","id":"PMC_26201295","title":"Rap2B promotes proliferation, migration, and 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\"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro biochemical assays with purified recombinant protein and direct kinase assay; foundational characterization replicated in subsequent papers\",\n      \"pmids\": [\"2118648\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1990,\n      \"finding\": \"Purified recombinant RAP2B binds both GTP and GDP in a Mg2+-dependent fashion, with higher relative affinity for GTP than GDP; a polyclonal antiserum against recombinant RAP2B recognizes a ~21 kDa protein in platelet membrane fractions and immunoprecipitates RAP2B complexed with GTP or GDP.\",\n      \"method\": \"In vitro GTP/GDP binding assay, immunoprecipitation, Western blot\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — direct in vitro nucleotide binding with purified protein; consistent with and replicated by the founding PNAS paper\",\n      \"pmids\": [\"2118346\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1992,\n      \"finding\": \"A partially purified protein from bovine brain membranes stimulates the GTPase activity of RAP2B (a RAP2B-GAP); this GAP activity is immunologically distinct from RAP1-GAP and RAS-GAP, yet shows limited stimulatory activity toward RAP1, indicating it is a distinct GAP for the RAP2 subfamily.\",\n      \"method\": \"Partial protein purification from bovine brain membranes, GTPase activity assay, immunoblotting with specific antibodies\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — direct enzymatic assay with partially purified material, single lab, protein not fully characterized\",\n      \"pmids\": [\"1472043\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1993,\n      \"finding\": \"RAP2B translocates from the Triton X-100-soluble fraction to the cytoskeleton upon platelet aggregation induced by thrombin, thromboxane analogue, or thapsigargin; translocation depends on platelet aggregation and requires fibrinogen binding to glycoprotein IIb-IIIa.\",\n      \"method\": \"Subcellular fractionation (Triton X-100 lysis, differential centrifugation), Western blot with specific antiserum\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — direct fractionation experiment with multiple agonists and pharmacological inhibitors; replicated in subsequent studies\",\n      \"pmids\": [\"8356055\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1993,\n      \"finding\": \"Microinjection of RAP2B protein or mRNA into Xenopus oocytes induces rearrangement of pigment granules ('mottling'); this effect requires membrane association via post-translational processing of the C-terminal CAAX motif, as a Cys→Ser mutation in the CAAX box prevents membrane association and mottling. The effect is blocked by the cytoskeletal reagent phalloidin.\",\n      \"method\": \"Xenopus oocyte microinjection, site-directed mutagenesis, membrane fractionation\",\n      \"journal\": \"The Biochemical journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — reconstitution in intact cells with mutagenesis validation and pharmacological controls; single lab but multiple orthogonal approaches\",\n      \"pmids\": [\"7684898\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1994,\n      \"finding\": \"Translocation of RAP2B to the platelet cytoskeleton requires agonist-induced actin polymerization and is dependent on glycoprotein IIb-IIIa (the fibrinogen receptor); platelets from Glanzmann thrombasthenia patients lacking GPIIb-IIIa fail to incorporate RAP2B into the cytoskeleton. RAP2B and GPIIb-IIIa co-translocate to the cytoskeleton during aggregation.\",\n      \"method\": \"Platelet fractionation, blocking antibodies against GPIIb-IIIa, use of Glanzmann thrombasthenia patient platelets, Western blot\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic (patient cells) and antibody-blocking evidence combined; replicated from prior fractionation study\",\n      \"pmids\": [\"8183895\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"von Willebrand factor (vWF) stimulation of human platelets induces rapid translocation of RAP2B to the cytoskeleton via a pathway requiring GPIb, FcγRII receptor-mediated tyrosine phosphorylation, and the kinase pp72(syk); translocation is blocked by genistein (tyrosine kinase inhibitor), cAMP-elevating agents, and anti-FcγRII antibody.\",\n      \"method\": \"Platelet fractionation, blocking antibodies (anti-GPIb, anti-FcγRII, RGDS peptide), pharmacological inhibitors (genistein, cytochalasin D, cAMP agents), Western blot, identification of substrates (syk, PLCγ2, SHIP)\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple blocking strategies, receptor-specific antibodies, and substrate identification in primary human cells\",\n      \"pmids\": [\"10224142\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"RAP2B mediates stimulation of phospholipase C-epsilon (PLC-ε) downstream of the M3 muscarinic acetylcholine receptor; this occurs via a cAMP/Epac1 pathway: M3 mAChR activates adenylyl cyclase, raises cAMP, activates Epac1 (a Rap GEF), which loads GTP onto RAP2B, which then stimulates PLC-ε to increase [Ca2+]i. Dominant-negative RAP2B (but not dominant-negative Rac1, Ras, RalA, Rap1A, or Rap2A) suppresses M3-mediated PLC stimulation.\",\n      \"method\": \"Overexpression/dominant-negative constructs, adenylyl cyclase inhibitor (dd-Ado), clostridial toxin inactivation of Ras-related GTPases, GTP-loading assay for RAP2B, PLC activity assay, Ca2+ measurement in HEK-293 cells\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal tools (dominant-negatives, pharmacological inhibitors, GTP-loading assay) in one study with specificity controls comparing multiple GTPases\",\n      \"pmids\": [\"11877431\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"EGF receptor activates RAP2B via c-Src-dependent tyrosine phosphorylation of RasGRP3 (a Ca2+/diacylglycerol-regulated GEF); activated RAP2B then binds directly to PLC-ε and drives its translocation to the plasma membrane, leading to PLC/Ca2+ signaling. GTP loading of RAP2B by EGF requires intracellular Ca2+ and lipase-active PLC-γ1 (upstream), but not PLC-ε.\",\n      \"method\": \"Dominant-negative RAP2B expression, clostridial toxin treatment, GTP-loading pull-down assay, co-immunoprecipitation of RAP2B with PLC-ε, confocal imaging of PLC-ε translocation, c-Src inhibition, intracellular Ca2+ chelation, in HEK-293 cells\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — direct binding of RAP2B to PLC-ε by Co-IP, translocation by imaging, GTP-loading, and multiple mechanistic interventions in one rigorous study\",\n      \"pmids\": [\"15143162\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"In human platelets, thrombin (via G-protein-coupled receptors) and convulxin (via GPVI/tyrosine kinase pathway) both induce rapid GTP loading of RAP2B. Thrombin-induced RAP2B activation is partially dependent on secreted ADP acting through the Gi-coupled P2Y12 receptor and fully dependent on PI3-kinase activity. Convulxin-induced activation requires PKC and is PI3K-independent. Both are regulated by intracellular Ca2+. cAMP-elevating agents do not activate RAP2B.\",\n      \"method\": \"GTP-loading assay (pull-down with RAP2B-binding domain), pharmacological inhibitors (PI3K inhibitor, PKC inhibitor, ADP scavenger, Ca2+ chelator), P2Y12 antagonist, in primary human platelets\",\n      \"journal\": \"Journal of thrombosis and haemostasis\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — direct GTP-loading assays in primary cells with multiple specific pharmacological interventions dissecting upstream pathway\",\n      \"pmids\": [\"15613030\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"RAP2B (but not RAP1B) constitutively associates with lipid rafts in human platelets; this association is mediated by palmitoylation at Cys176 and Cys177 (but not at the CAAX motif). Disruption of lipid raft association by cholesterol depletion impairs agonist-induced RAP2B activation and inhibits platelet aggregation.\",\n      \"method\": \"Lipid raft isolation (detergent-resistant membrane fractionation), [3H]palmitate metabolic labeling, site-directed mutagenesis (C176S, C177S, CAAX deletion) in transfected HEK293T cells and primary platelets, cholesterol depletion, GTP-loading assay, platelet aggregation assay\",\n      \"journal\": \"Cellular signalling\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — mutagenesis, metabolic labeling, and functional assays in one study with two cell systems; single lab but multiple orthogonal methods\",\n      \"pmids\": [\"18582561\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"RAP2B is a direct transcriptional target of p53 that mediates a pro-survival function after DNA damage; p53 binds the RAP2B promoter upon DNA damage and activates its transcription. siRNA knockdown of RAP2B sensitizes cells to DNA damage-induced apoptosis in a p53-dependent manner.\",\n      \"method\": \"Integrative genomic analysis, chromatin immunoprecipitation (p53 binding to RAP2B promoter), siRNA knockdown, apoptosis assays, anchorage-independent growth assay\",\n      \"journal\": \"Cell cycle (Georgetown, Tex.)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP for direct promoter binding plus functional siRNA knockdown with p53-dependency controls; single lab with two orthogonal methods\",\n      \"pmids\": [\"23535297\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"RAP2B promotes breast cancer cell proliferation, migration, and invasion by elevating intracellular calcium levels and promoting ERK1/2 phosphorylation; calcium chelator BAPTA/AM and MEK inhibitor U0126 reverse RAP2B-induced ERK1/2 phosphorylation, placing RAP2B upstream of a Ca2+/ERK1/2 axis.\",\n      \"method\": \"siRNA knockdown and overexpression, CCK-8 proliferation assay, transwell assay, flow cytometry (calcium measurement), Western blot (ERK1/2 phosphorylation), pharmacological inhibitors (BAPTA/AM, U0126)\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple assays with pharmacological pathway dissection; single lab but two orthogonal functional readouts\",\n      \"pmids\": [\"26201295\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"RAP2B inhibits cell spreading by disrupting actin dynamics in a CAAX-dependent manner; expression of RAP2B is induced by nocodazole in a p53-dependent manner, and a C180A CAAX mutant of RAP2B does not inhibit cell spreading, demonstrating that membrane targeting is required for cytoskeletal effects.\",\n      \"method\": \"Western blot, immunofluorescence, overexpression and knockdown, site-directed mutagenesis (C180A), nocodazole treatment\",\n      \"journal\": \"Journal of cancer research and clinical oncology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — mutagenesis combined with imaging and knockdown; single lab with two orthogonal approaches\",\n      \"pmids\": [\"25762091\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"p53 upregulates the RAP2B–PLC-ε–IP3–Ca2+ pathway and thereby inhibits starvation-induced autophagy; p53 induction increases intracellular IP3 and Ca2+ levels and decreases LC3 levels through RAP2B, establishing RAP2B as a mediator of p53-dependent autophagy inhibition.\",\n      \"method\": \"Microarray-based target identification, overexpression/knockdown, measurement of IP3, Ca2+, and LC3 levels by Western blot and biochemical assays\",\n      \"journal\": \"Oncotarget\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct measurement of IP3, Ca2+, and autophagy markers downstream of RAP2B; single lab, two orthogonal readouts\",\n      \"pmids\": [\"29029384\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"RAP2B promotes prostate cancer cell migration and invasion via FAK-dependent signaling; elevated RAP2B increases FAK phosphorylation, and FAK-specific inhibitor PF-573228 abolishes RAP2B-induced FAK phosphorylation and the resulting migration/invasion phenotype.\",\n      \"method\": \"siRNA knockdown and overexpression, CCK-8, transwell assay, Western blot (p-FAK), pharmacological inhibitor (PF-573228), xenograft in vivo\",\n      \"journal\": \"Medical oncology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — pathway placement via specific FAK inhibitor rescue; single lab with functional and in vivo validation\",\n      \"pmids\": [\"27154636\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"RAP2B knockdown in glioma cells reduces expression levels of NF-κB, MMP-2, and MMP-9, and inhibits cell adhesion, proliferation, migration, and invasion, placing RAP2B upstream of the NF-κB pathway in glioma.\",\n      \"method\": \"siRNA knockdown, Western blot (NF-κB, MMP-2, MMP-9), CCK-8, wound healing, transwell invasion assay\",\n      \"journal\": \"Journal of neuro-oncology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — knockdown with defined molecular readouts; single lab, single method per pathway node\",\n      \"pmids\": [\"30997639\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"RAP2B promotes renal cell carcinoma angiogenesis in vitro and in vivo via activation of the PI3K/AKT signaling pathway, leading to upregulation of VEGF; this was demonstrated by ELISA measurement of VEGF, HUVEC growth, and tube formation assays with RAP2B knockdown/overexpression.\",\n      \"method\": \"siRNA knockdown and overexpression, Western blot, qPCR, ELISA (VEGF), HUVEC growth assay, endothelial tube formation assay, in vivo tumor model\",\n      \"journal\": \"Tumour biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple functional angiogenesis assays with pathway marker measurement; single lab\",\n      \"pmids\": [\"28691643\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Active RAP2B (wild-type) inhibits development of the Coxiella burnetii replicative vacuole (CRV) and impairs both homotypic (phagosome–CRV) and heterotypic (endosome/lysosome–CRV) fusion events; this effect is dependent on RAP2B GTPase activity (inactive ΔAAX mutant has no effect). RAP2B overexpression markedly decreases the v-SNARE Vamp7 levels, suggesting a mechanism involving SNARE downregulation.\",\n      \"method\": \"Transient overexpression of wild-type vs. inactive RAP2B mutant, fluorescence microscopy of vacuole size, fusion assays, Western blot (Vamp7)\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — WT vs. inactive mutant comparison with mechanistic readout (SNARE levels and fusion events); single lab, multiple assays\",\n      \"pmids\": [\"30763357\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"RAP2B is S-palmitoylated at Cys176 and Cys177 at the C-terminus, which is required for its plasma membrane localization; ABHD17a is identified as the depalmitoylating enzyme for RAP2B, and its PI3K-mediated phosphorylation by EGFR/PI3K signaling regulates ABHD17a activity and thus RAP2B palmitoylation. Mutation of C176/C177 or a blocking peptide targeting these sites causes cytosolic relocation of RAP2B and suppresses CRC cell migration/invasion and metastasis.\",\n      \"method\": \"Site-directed mutagenesis (C176/C177), palmitoylation assays, Co-IP identifying ABHD17a, pharmacological inhibition of PI3K, blocking peptide, xenograft metastasis model\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — mutagenesis, identification of depalmitoylase, upstream kinase regulation, and in vivo functional validation in one study; single lab but multiple orthogonal methods\",\n      \"pmids\": [\"39277583\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Intestine-specific knockout of RAP2B suppresses CRC initiation and progression in vivo; mechanistically, RAP2B interacts with plectin and enhances plectin expression, which inhibits plectin-mediated F-actin assembly, leading to cytoskeletal remodeling that promotes tumorigenesis and metastasis.\",\n      \"method\": \"Intestine-specific knockout mouse model, co-immunoprecipitation (RAP2B–plectin interaction), Western blot (plectin, F-actin markers), in vivo tumor growth and metastasis assays, human CRC tissue correlation\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic knockout in vivo combined with Co-IP for direct binding partner and mechanistic cytoskeletal readout; single lab but multiple orthogonal approaches\",\n      \"pmids\": [\"40223002\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"RAP2B overexpression in Rat1 fibroblasts induces oncogenic transformation foci and activates the NF-κB pathway more than 3-fold as measured by reporter gene assay.\",\n      \"method\": \"Stable transfection in Rat1 cells, colony/focus formation assay, NF-κB reporter gene assay\",\n      \"journal\": \"Zhongguo fei ai za zhi (Chinese journal of lung cancer)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct functional transformation assay plus reporter assay for pathway activation; single lab, two orthogonal readouts\",\n      \"pmids\": [\"20719111\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"RAP2B overexpression activates the PI3K/AKT signaling pathway and confers resistance to cetuximab in colorectal cancer cells; RAP2B knockdown inhibits PI3K/AKT signaling, reduces cell proliferation, enhances apoptosis, and restores cetuximab sensitivity both in vitro and in vivo.\",\n      \"method\": \"Knockdown and overexpression, Western blot (PI3K/AKT pathway markers), cell proliferation, apoptosis assays, xenograft in vivo\",\n      \"journal\": \"Biological procedures online\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — bidirectional manipulation with pathway readout and in vivo confirmation; single lab\",\n      \"pmids\": [\"41094393\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"RAP2B is a Ras-family small GTPase that cycles between GDP-bound (inactive) and GTP-bound (active) states; it is post-translationally processed at its C-terminal CAAX motif and further palmitoylated at Cys176/Cys177 (with ABHD17a as the depalmitoylase and EGFR/PI3K regulating this cycle), which controls its plasma membrane and lipid-raft targeting. Active RAP2B is loaded with GTP downstream of multiple receptors — GPCRs, receptor tyrosine kinases (EGFR via c-Src/RasGRP3), and GPVI — and directly binds and translocates PLC-ε to the plasma membrane, stimulating IP3/Ca2+ signaling; it also translocates to the platelet cytoskeleton in a GPIIb-IIIa- and actin-polymerization-dependent manner during aggregation. As a direct transcriptional target of p53, RAP2B counteracts DNA-damage-induced apoptosis, inhibits autophagy via the PLCε–IP3–Ca2+ axis, and regulates cytoskeletal dynamics by interacting with plectin to suppress F-actin assembly; in multiple cancer contexts it drives proliferation, migration, and invasion through ERK1/2, PI3K/AKT, FAK, and NF-κB signaling pathways.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"RAP2B is a Ras-family small GTPase, originally characterized in human platelets, that cycles between GDP- and GTP-bound states and binds guanine nucleotides in a Mg2+-dependent manner with preference for GTP [#0, #1]. Its membrane targeting depends on two layers of C-terminal processing: CAAX-motif prenylation, which is required for membrane association and downstream cellular effects [#4, #13], and S-palmitoylation at Cys176/Cys177, which directs RAP2B to lipid rafts and the plasma membrane; this palmitoylation cycle is controlled by the depalmitoylase ABHD17a under EGFR/PI3K regulation [#10, #19]. RAP2B is loaded with GTP downstream of diverse receptors — GPCRs via a cAMP/Epac1 route from the M3 muscarinic receptor, the EGF receptor via c-Src-dependent phosphorylation of the GEF RasGRP3, and platelet receptors (GPCRs/P2Y12, GPVI, and the GPIb–FcγRII–Syk axis) [#7, #8, #9, #6]. A central effector function is direct binding to phospholipase C-ε and driving its translocation to the plasma membrane, thereby stimulating IP3/Ca2+ signaling [#8]. During platelet aggregation RAP2B translocates to the cytoskeleton in a manner dependent on actin polymerization and fibrinogen binding to glycoprotein IIb-IIIa [#3, #5]. RAP2B is a direct transcriptional target of p53 that promotes survival after DNA damage and suppresses starvation-induced autophagy through the PLC-ε–IP3–Ca2+ axis [#11, #14]. In multiple cancers RAP2B drives proliferation, migration, invasion, and angiogenesis through Ca2+/ERK1/2, PI3K/AKT (including VEGF induction and cetuximab resistance), FAK, and NF-κB signaling [#12, #17, #15, #16, #22], and it remodels the cytoskeleton by interacting with plectin to modulate F-actin assembly [#20].\",\n  \"teleology\": [\n    {\n      \"year\": 1990,\n      \"claim\": \"Established that RAP2B is a genuine GTP-binding protein distinct from the related RAP1 proteins, defining it as a candidate signaling GTPase in platelets.\",\n      \"evidence\": \"cDNA cloning, bacterial expression, GTP-blotting and kinase assay; in vitro GTP/GDP binding and immunoprecipitation from platelet membranes\",\n      \"pmids\": [\"2118648\", \"2118346\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No physiological GEF or receptor input identified at this stage\", \"Cellular function unknown\"]\n    },\n    {\n      \"year\": 1992,\n      \"claim\": \"Identified a RAP2-subfamily-specific GAP, addressing how RAP2B is switched off and distinguishing its regulation from RAP1/RAS.\",\n      \"evidence\": \"Partial protein purification from bovine brain membranes with GTPase assays and antibody discrimination\",\n      \"pmids\": [\"1472043\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"GAP protein not molecularly identified or cloned\", \"Single lab, partially purified material\"]\n    },\n    {\n      \"year\": 1993,\n      \"claim\": \"Linked RAP2B to cytoskeletal dynamics by showing it translocates to the cytoskeleton on platelet activation and induces cytoskeleton-dependent rearrangements requiring CAAX processing.\",\n      \"evidence\": \"Platelet subcellular fractionation with multiple agonists; Xenopus oocyte microinjection with CAAX mutagenesis and phalloidin block\",\n      \"pmids\": [\"8356055\", \"7684898\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular effectors of cytoskeletal effect not identified\", \"Direct cytoskeletal binding partner unknown\"]\n    },\n    {\n      \"year\": 1994,\n      \"claim\": \"Defined the receptor requirement for cytoskeletal translocation, showing it depends on GPIIb-IIIa and actin polymerization, using genetic (Glanzmann) evidence.\",\n      \"evidence\": \"Platelet fractionation with blocking antibodies and Glanzmann thrombasthenia patient platelets\",\n      \"pmids\": [\"8183895\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanistic link between GPIIb-IIIa engagement and RAP2B recruitment unresolved\"]\n    },\n    {\n      \"year\": 1999,\n      \"claim\": \"Mapped a distinct receptor pathway (vWF/GPIb–FcγRII–Syk) driving RAP2B cytoskeletal translocation, broadening the upstream signaling inputs.\",\n      \"evidence\": \"Platelet fractionation with receptor-blocking antibodies, tyrosine kinase inhibitors, and substrate identification\",\n      \"pmids\": [\"10224142\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct GEF connecting Syk signaling to RAP2B not identified\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Identified PLC-ε as a RAP2B effector and an Epac1/cAMP route for its activation, establishing RAP2B as a specific transducer to Ca2+ signaling downstream of GPCRs.\",\n      \"evidence\": \"Dominant-negative and toxin tools, GTP-loading and PLC/Ca2+ assays in HEK-293 cells with multi-GTPase specificity controls\",\n      \"pmids\": [\"11877431\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct RAP2B–PLC-ε binding not yet demonstrated at this stage\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Demonstrated direct RAP2B–PLC-ε binding and PLC-ε translocation, and placed RAP2B downstream of EGFR via c-Src/RasGRP3, providing the core effector mechanism.\",\n      \"evidence\": \"Co-IP, confocal translocation imaging, GTP-loading, dominant-negative and c-Src inhibition in HEK-293; GTP-loading assays in platelets dissecting thrombin vs convulxin inputs\",\n      \"pmids\": [\"15143162\", \"15613030\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of RAP2B–PLC-ε interaction unknown\", \"GEF identity in platelet pathways not resolved\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Showed that palmitoylation at Cys176/Cys177 targets RAP2B to lipid rafts and is required for its agonist-induced activation, defining a membrane-microdomain control point.\",\n      \"evidence\": \"Detergent-resistant membrane fractionation, [3H]palmitate labeling, mutagenesis, cholesterol depletion, and aggregation assays in platelets and HEK293T\",\n      \"pmids\": [\"18582561\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Enzymes controlling the palmitoylation cycle not yet identified\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Placed RAP2B in the p53 network as a direct transcriptional target mediating survival after DNA damage, connecting it to tumor-relevant signaling.\",\n      \"evidence\": \"ChIP for p53 binding to the RAP2B promoter plus siRNA knockdown and apoptosis assays with p53-dependency controls\",\n      \"pmids\": [\"23535297\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Downstream survival effectors of RAP2B in this context not defined\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Connected the p53–RAP2B axis to autophagy, showing RAP2B mediates p53-dependent autophagy inhibition through PLC-ε–IP3–Ca2+.\",\n      \"evidence\": \"Microarray target identification, overexpression/knockdown, and measurement of IP3, Ca2+, and LC3\",\n      \"pmids\": [\"29029384\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab\", \"Link to canonical autophagy machinery beyond LC3 not detailed\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Extended RAP2B function to membrane trafficking, showing active RAP2B impairs Coxiella vacuole biogenesis and reduces the v-SNARE Vamp7.\",\n      \"evidence\": \"WT vs inactive ΔAAX mutant overexpression, vacuole imaging, fusion assays, and Vamp7 immunoblot\",\n      \"pmids\": [\"30763357\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism linking RAP2B to Vamp7 levels unclear\", \"Physiological (non-infection) trafficking role untested\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Resolved the regulated palmitoylation cycle, identifying ABHD17a as the RAP2B depalmitoylase under EGFR/PI3K control and showing membrane targeting drives metastasis.\",\n      \"evidence\": \"Mutagenesis, palmitoylation assays, Co-IP of ABHD17a, PI3K inhibition, blocking peptide, and xenograft metastasis model\",\n      \"pmids\": [\"39277583\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Palmitoyl-acyltransferase that adds the modification not identified\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Provided in vivo genetic proof that RAP2B drives colorectal tumorigenesis and identified plectin as a binding partner mediating its cytoskeletal effects, while reinforcing PI3K/AKT-dependent therapy resistance.\",\n      \"evidence\": \"Intestine-specific knockout mice, Co-IP of RAP2B–plectin, F-actin readouts, metastasis assays; bidirectional manipulation with PI3K/AKT readout and cetuximab-resistance xenografts\",\n      \"pmids\": [\"40223002\", \"41094393\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How RAP2B nucleotide state controls plectin binding/F-actin is undefined\", \"Relation between plectin axis and PLC-ε/Ca2+ signaling unresolved\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The integrated upstream GEF network and the structural/nucleotide-state logic coupling RAP2B to its distinct effectors (PLC-ε, plectin, SNARE machinery) across cell types remain unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No unified model of which GEF acts in which receptor context\", \"No structural data on effector selection\", \"Tissue-specific GAP regulation uncharacterized\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0003924\", \"supporting_discovery_ids\": [0, 1, 2, 18]},\n      {\"term_id\": \"GO:0060089\", \"supporting_discovery_ids\": [7, 8, 9]},\n      {\"term_id\": \"GO:0008092\", \"supporting_discovery_ids\": [20]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [8, 10, 19]},\n      {\"term_id\": \"GO:0005856\", \"supporting_discovery_ids\": [3, 5]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [19]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [7, 8, 12, 17]},\n      {\"term_id\": \"R-HSA-109582\", \"supporting_discovery_ids\": [3, 5, 6, 9]},\n      {\"term_id\": \"R-HSA-9612973\", \"supporting_discovery_ids\": [14]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [12, 15, 16, 17, 22]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"PLCE1\", \"RASGRP3\", \"ABHD17A\", \"PLEC\", \"ITGB3\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":7,"faith_total":7,"faith_pct":100.0}}