{"gene":"RHPN1","run_date":"2026-06-14T21:17:34+00:00","timeline":{"discoveries":[{"year":2002,"finding":"Rhophilin-1 (RHPN1) interacts with both GDP- and GTP-bound RhoA in vitro, indicating a nucleotide-independent binding mode. Unlike Rhophilin-2, overexpression of Rhophilin-1 had no noticeable effect on actin stress fiber organization in HeLa cells.","method":"GST-capture pulldown assay (in vitro), cell overexpression with actin cytoskeleton imaging","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — GST pulldown in vitro with nucleotide-loaded RhoA plus cellular overexpression, single lab, two orthogonal methods","pmids":["12221077"],"is_preprint":false},{"year":2014,"finding":"Rhophilin-1 localizes to the plasma membrane leading edge of primary podocytes and regulates actin cytoskeleton remodeling. Its loss leads to increased phosphorylation of myosin regulatory light chain (via the Rho pathway) and actomyosin hypercontractility, resulting in foot process effacement and glomerular filtration barrier failure. Targeted deletion of RhoA in Rhpn1-null podocytes exacerbated renal injury, placing RHPN1 as a modulator that dampens RhoA-dependent signaling in podocytes.","method":"Knockout mouse model (Rhpn1-/- and RhoA conditional KO), immunofluorescence localization, phospho-myosin regulatory light chain assays, electron microscopy, genetic epistasis (double KO)","journal":"Journal of the American Society of Nephrology : JASN","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vivo KO with defined cellular phenotype, biochemical readout (p-MLC), genetic epistasis with RhoA double KO, multiple orthogonal methods in single rigorous study","pmids":["25071083"],"is_preprint":false},{"year":2009,"finding":"shRNA-mediated knockdown of RhoA and its effector Rhophilin-1 is sufficient to induce sustained KLF2 mRNA expression, establishing RHPN1 as a downstream effector in a RhoA–Rhophilin-1 signaling cascade that suppresses KLF2 transcription.","method":"shRNA knockdown of RhoA and RHPN1 with qRT-PCR readout of KLF2 mRNA in macrophage-like cells","journal":"Infection and immunity","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — shRNA loss-of-function with defined transcriptional phenotype, single lab, single main method","pmids":["19786564"],"is_preprint":false},{"year":2020,"finding":"ROPN1 (Rhophilin-associated tail protein 1) activates RhoA signaling through a physical or functional interaction with RHPN1, leading to enhanced actin stress fiber formation and increased migration and invasion in triple-negative breast cancer cells.","method":"Overexpression and siRNA silencing of ROPN1/RHPN1 in TNBC cell lines, actin stress fiber imaging, RhoA activity assays, in vivo metastasis assays","journal":"FASEB journal : official publication of the Federation of American Societies for Experimental Biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — loss- and gain-of-function with biochemical (RhoA activity) and cell biological (actin) readouts, single lab, multiple orthogonal methods","pmids":["32427399"],"is_preprint":false}],"current_model":"RHPN1 (Rhophilin-1) is a RhoA-binding effector protein that, at the podocyte plasma membrane leading edge, dampens RhoA-dependent myosin regulatory light chain phosphorylation and stress fiber formation to maintain cytoskeletal architecture; it also functions downstream of RhoA to suppress KLF2 transcription in macrophages, and can be activated upstream by ROPN1 to promote actin stress fiber assembly and cell motility in breast cancer cells."},"narrative":{"mechanistic_narrative":"RHPN1 (Rhophilin-1) is a RhoA-binding effector that modulates RhoA-dependent actin cytoskeletal remodeling in a context-dependent manner [PMID:12221077, PMID:25071083]. It binds both GDP- and GTP-bound RhoA in vitro, indicating a nucleotide-independent interaction mode, and unlike Rhophilin-2 its overexpression alone does not reorganize actin stress fibers [PMID:12221077]. In primary podocytes, RHPN1 localizes to the plasma membrane leading edge and dampens RhoA signaling: its loss elevates myosin regulatory light chain phosphorylation and drives actomyosin hypercontractility, foot process effacement, and glomerular filtration barrier failure, with concurrent RhoA deletion worsening injury and establishing RHPN1 as a negative modulator of RhoA-dependent contractility [PMID:25071083]. RHPN1 also acts as a downstream effector in a RhoA–Rhophilin-1 cascade that suppresses KLF2 transcription in macrophage-like cells [PMID:19786564], and in triple-negative breast cancer cells it cooperates with ROPN1 to activate RhoA, promoting stress fiber assembly, migration, and invasion [PMID:32427399]. Beyond these RhoA-coupled roles in cytoskeletal and transcriptional control, no further mechanistic detail has been characterized in the available corpus.","teleology":[{"year":2002,"claim":"Established that Rhophilin-1 is a RhoA-binding protein with a distinct mode and cellular consequence from its paralog, defining its biochemical relationship to RhoA.","evidence":"GST-capture pulldown with nucleotide-loaded RhoA plus overexpression and actin imaging in HeLa cells","pmids":["12221077"],"confidence":"Medium","gaps":["Binding interface and structural basis of nucleotide-independent association not defined","Functional consequence of RhoA binding in vivo not addressed","No physiological cell context examined"]},{"year":2009,"claim":"Placed RHPN1 in a RhoA effector cascade controlling gene expression, showing it acts downstream of RhoA to suppress KLF2 transcription.","evidence":"shRNA knockdown of RhoA and RHPN1 with qRT-PCR readout of KLF2 mRNA in macrophage-like cells","pmids":["19786564"],"confidence":"Medium","gaps":["Molecular link between RHPN1 and KLF2 promoter regulation unknown","Single loss-of-function method without rescue","Direct versus indirect effect not distinguished"]},{"year":2014,"claim":"Defined RHPN1's physiological role as a negative modulator of RhoA-dependent actomyosin contractility required for podocyte architecture and the glomerular filtration barrier.","evidence":"Rhpn1-null and RhoA conditional KO mice with phospho-MLC assays, immunofluorescence localization, electron microscopy, and genetic epistasis","pmids":["25071083"],"confidence":"High","gaps":["Mechanism by which RHPN1 dampens RhoA output at the leading edge not resolved","Whether direct RhoA binding mediates the dampening untested","Generalizability beyond podocytes unclear"]},{"year":2020,"claim":"Revealed a context where RHPN1 promotes rather than dampens RhoA signaling, acting with ROPN1 to drive stress fiber formation and tumor cell invasion.","evidence":"Gain- and loss-of-function of ROPN1/RHPN1 in TNBC lines with RhoA activity assays, actin imaging, and in vivo metastasis assays","pmids":["32427399"],"confidence":"Medium","gaps":["Direct physical interaction between ROPN1 and RHPN1 not biochemically resolved","Basis for opposing RhoA effects across cell types unexplained","Structural mechanism of RhoA activation unknown"]},{"year":null,"claim":"How RHPN1 switches between dampening and activating RhoA-dependent cytoskeletal output across cell types remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No structural model of the RHPN1–RhoA or RHPN1–ROPN1 interface","No identified determinant of context-specific signaling polarity","Mechanistic link to downstream MLC and KLF2 outputs incompletely mapped"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[1]},{"term_id":"GO:0008092","term_label":"cytoskeletal protein binding","supporting_discovery_ids":[0,1]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[1]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[1,3]}],"complexes":[],"partners":["RHOA","ROPN1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q8TCX5","full_name":"Rhophilin-1","aliases":["GTP-Rho-binding protein 1"],"length_aa":670,"mass_kda":73.6,"function":"Has no enzymatic activity. May serve as a target for Rho, and interact with some cytoskeletal component upon Rho binding or relay a Rho signal to other molecules","subcellular_location":"","url":"https://www.uniprot.org/uniprotkb/Q8TCX5/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/RHPN1","classification":"Not Classified","n_dependent_lines":254,"n_total_lines":1208,"dependency_fraction":0.21026490066225165},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/RHPN1","total_profiled":1310},"omim":[{"mim_id":"601031","title":"RHOPHILIN 1; RHPN1","url":"https://www.omim.org/entry/601031"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Nucleoplasm","reliability":"Approved"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"brain","ntpm":16.0},{"tissue":"pituitary gland","ntpm":18.9},{"tissue":"thyroid gland","ntpm":19.4}],"url":"https://www.proteinatlas.org/search/RHPN1"},"hgnc":{"alias_symbol":["KIAA1929","RHPN","ODF5"],"prev_symbol":[]},"alphafold":{"accession":"Q8TCX5","domains":[{"cath_id":"1.25.40.280","chopping":"159-370_398-455","consensus_level":"medium","plddt":90.6819,"start":159,"end":455},{"cath_id":"2.30.42.10","chopping":"499-592","consensus_level":"high","plddt":91.5544,"start":499,"end":592},{"cath_id":"1.20.58","chopping":"31-92","consensus_level":"high","plddt":87.1548,"start":31,"end":92}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8TCX5","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q8TCX5-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q8TCX5-F1-predicted_aligned_error_v6.png","plddt_mean":78.19},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=RHPN1","jax_strain_url":"https://www.jax.org/strain/search?query=RHPN1"},"sequence":{"accession":"Q8TCX5","fasta_url":"https://rest.uniprot.org/uniprotkb/Q8TCX5.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q8TCX5/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8TCX5"}},"corpus_meta":[{"pmid":"12221077","id":"PMC_12221077","title":"The RhoA-binding protein, rhophilin-2, regulates actin cytoskeleton organization.","date":"2002","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/12221077","citation_count":75,"is_preprint":false},{"pmid":"25071083","id":"PMC_25071083","title":"Rhophilin-1 is a key regulator of the podocyte cytoskeleton and is essential for glomerular filtration.","date":"2014","source":"Journal of the American Society of Nephrology : JASN","url":"https://pubmed.ncbi.nlm.nih.gov/25071083","citation_count":28,"is_preprint":false},{"pmid":"19786564","id":"PMC_19786564","title":"Bacterial toxins induce sustained mRNA expression of the silencing transcription factor klf2 via inactivation of RhoA and Rhophilin 1.","date":"2009","source":"Infection and immunity","url":"https://pubmed.ncbi.nlm.nih.gov/19786564","citation_count":20,"is_preprint":false},{"pmid":"31257472","id":"PMC_31257472","title":"Identification of crucial miRNAs and lncRNAs for ossification of ligamentum flavum.","date":"2019","source":"Molecular medicine reports","url":"https://pubmed.ncbi.nlm.nih.gov/31257472","citation_count":10,"is_preprint":false},{"pmid":"32427399","id":"PMC_32427399","title":"Rhophilin-associated tail protein 1 promotes migration and metastasis in triple negative breast cancer via activation of RhoA.","date":"2020","source":"FASEB journal : official publication of the Federation of American Societies for Experimental Biology","url":"https://pubmed.ncbi.nlm.nih.gov/32427399","citation_count":8,"is_preprint":false}],"cost":{"stage1":{"sonnet_model":"claude-sonnet-4-6","sonnet_input_tokens":5209,"sonnet_output_tokens":1161,"sonnet_usd":0.033,"sonnet_elapsed_seconds":20.8,"stage1_stop_reason":"end_turn"},"stage2":{"opus_model":"claude-opus-4-8","opus_input_tokens":7732,"opus_output_tokens":1886,"opus_usd":0.0858,"opus_elapsed_seconds":21.3,"stage2_stop_reason":"end_turn"},"total_usd":0.1188},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2002,\n      \"finding\": \"Rhophilin-1 (RHPN1) interacts with both GDP- and GTP-bound RhoA in vitro, indicating a nucleotide-independent binding mode. Unlike Rhophilin-2, overexpression of Rhophilin-1 had no noticeable effect on actin stress fiber organization in HeLa cells.\",\n      \"method\": \"GST-capture pulldown assay (in vitro), cell overexpression with actin cytoskeleton imaging\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — GST pulldown in vitro with nucleotide-loaded RhoA plus cellular overexpression, single lab, two orthogonal methods\",\n      \"pmids\": [\"12221077\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Rhophilin-1 localizes to the plasma membrane leading edge of primary podocytes and regulates actin cytoskeleton remodeling. Its loss leads to increased phosphorylation of myosin regulatory light chain (via the Rho pathway) and actomyosin hypercontractility, resulting in foot process effacement and glomerular filtration barrier failure. Targeted deletion of RhoA in Rhpn1-null podocytes exacerbated renal injury, placing RHPN1 as a modulator that dampens RhoA-dependent signaling in podocytes.\",\n      \"method\": \"Knockout mouse model (Rhpn1-/- and RhoA conditional KO), immunofluorescence localization, phospho-myosin regulatory light chain assays, electron microscopy, genetic epistasis (double KO)\",\n      \"journal\": \"Journal of the American Society of Nephrology : JASN\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vivo KO with defined cellular phenotype, biochemical readout (p-MLC), genetic epistasis with RhoA double KO, multiple orthogonal methods in single rigorous study\",\n      \"pmids\": [\"25071083\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"shRNA-mediated knockdown of RhoA and its effector Rhophilin-1 is sufficient to induce sustained KLF2 mRNA expression, establishing RHPN1 as a downstream effector in a RhoA–Rhophilin-1 signaling cascade that suppresses KLF2 transcription.\",\n      \"method\": \"shRNA knockdown of RhoA and RHPN1 with qRT-PCR readout of KLF2 mRNA in macrophage-like cells\",\n      \"journal\": \"Infection and immunity\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — shRNA loss-of-function with defined transcriptional phenotype, single lab, single main method\",\n      \"pmids\": [\"19786564\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"ROPN1 (Rhophilin-associated tail protein 1) activates RhoA signaling through a physical or functional interaction with RHPN1, leading to enhanced actin stress fiber formation and increased migration and invasion in triple-negative breast cancer cells.\",\n      \"method\": \"Overexpression and siRNA silencing of ROPN1/RHPN1 in TNBC cell lines, actin stress fiber imaging, RhoA activity assays, in vivo metastasis assays\",\n      \"journal\": \"FASEB journal : official publication of the Federation of American Societies for Experimental Biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — loss- and gain-of-function with biochemical (RhoA activity) and cell biological (actin) readouts, single lab, multiple orthogonal methods\",\n      \"pmids\": [\"32427399\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"RHPN1 (Rhophilin-1) is a RhoA-binding effector protein that, at the podocyte plasma membrane leading edge, dampens RhoA-dependent myosin regulatory light chain phosphorylation and stress fiber formation to maintain cytoskeletal architecture; it also functions downstream of RhoA to suppress KLF2 transcription in macrophages, and can be activated upstream by ROPN1 to promote actin stress fiber assembly and cell motility in breast cancer cells.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"RHPN1 (Rhophilin-1) is a RhoA-binding effector that modulates RhoA-dependent actin cytoskeletal remodeling in a context-dependent manner [#0, #1]. It binds both GDP- and GTP-bound RhoA in vitro, indicating a nucleotide-independent interaction mode, and unlike Rhophilin-2 its overexpression alone does not reorganize actin stress fibers [#0]. In primary podocytes, RHPN1 localizes to the plasma membrane leading edge and dampens RhoA signaling: its loss elevates myosin regulatory light chain phosphorylation and drives actomyosin hypercontractility, foot process effacement, and glomerular filtration barrier failure, with concurrent RhoA deletion worsening injury and establishing RHPN1 as a negative modulator of RhoA-dependent contractility [#1]. RHPN1 also acts as a downstream effector in a RhoA–Rhophilin-1 cascade that suppresses KLF2 transcription in macrophage-like cells [#2], and in triple-negative breast cancer cells it cooperates with ROPN1 to activate RhoA, promoting stress fiber assembly, migration, and invasion [#3]. Beyond these RhoA-coupled roles in cytoskeletal and transcriptional control, no further mechanistic detail has been characterized in the available corpus.\",\n  \"teleology\": [\n    {\n      \"year\": 2002,\n      \"claim\": \"Established that Rhophilin-1 is a RhoA-binding protein with a distinct mode and cellular consequence from its paralog, defining its biochemical relationship to RhoA.\",\n      \"evidence\": \"GST-capture pulldown with nucleotide-loaded RhoA plus overexpression and actin imaging in HeLa cells\",\n      \"pmids\": [\"12221077\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Binding interface and structural basis of nucleotide-independent association not defined\", \"Functional consequence of RhoA binding in vivo not addressed\", \"No physiological cell context examined\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Placed RHPN1 in a RhoA effector cascade controlling gene expression, showing it acts downstream of RhoA to suppress KLF2 transcription.\",\n      \"evidence\": \"shRNA knockdown of RhoA and RHPN1 with qRT-PCR readout of KLF2 mRNA in macrophage-like cells\",\n      \"pmids\": [\"19786564\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular link between RHPN1 and KLF2 promoter regulation unknown\", \"Single loss-of-function method without rescue\", \"Direct versus indirect effect not distinguished\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Defined RHPN1's physiological role as a negative modulator of RhoA-dependent actomyosin contractility required for podocyte architecture and the glomerular filtration barrier.\",\n      \"evidence\": \"Rhpn1-null and RhoA conditional KO mice with phospho-MLC assays, immunofluorescence localization, electron microscopy, and genetic epistasis\",\n      \"pmids\": [\"25071083\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism by which RHPN1 dampens RhoA output at the leading edge not resolved\", \"Whether direct RhoA binding mediates the dampening untested\", \"Generalizability beyond podocytes unclear\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Revealed a context where RHPN1 promotes rather than dampens RhoA signaling, acting with ROPN1 to drive stress fiber formation and tumor cell invasion.\",\n      \"evidence\": \"Gain- and loss-of-function of ROPN1/RHPN1 in TNBC lines with RhoA activity assays, actin imaging, and in vivo metastasis assays\",\n      \"pmids\": [\"32427399\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct physical interaction between ROPN1 and RHPN1 not biochemically resolved\", \"Basis for opposing RhoA effects across cell types unexplained\", \"Structural mechanism of RhoA activation unknown\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How RHPN1 switches between dampening and activating RhoA-dependent cytoskeletal output across cell types remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No structural model of the RHPN1–RhoA or RHPN1–ROPN1 interface\", \"No identified determinant of context-specific signaling polarity\", \"Mechanistic link to downstream MLC and KLF2 outputs incompletely mapped\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [1]},\n      {\"term_id\": \"GO:0008092\", \"supporting_discovery_ids\": [0, 1]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [1]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [1, 3]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"RHOA\", \"ROPN1\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win"}}