{"gene":"SAMSN1","run_date":"2026-04-28T20:42:07","timeline":{"discoveries":[{"year":2001,"finding":"HACS1 (SAMSN1) encodes a 441 amino acid adaptor protein containing an SH3 domain (most similar to Crk) and a SAM domain, and is localized predominantly to the cytoplasm as determined by immunostaining and cellular fractionation.","method":"Immunostaining and cellular fractionation; domain analysis","journal":"Oncogene","confidence":"Medium","confidence_rationale":"Tier 2 — direct fractionation experiment with functional domain characterization, single lab","pmids":["11536050"],"is_preprint":false},{"year":2001,"finding":"Nash1 (SAMSN1), which contains a nuclear localization signal (NLS), SAM, and SH3 domain, localizes to the nucleus in mast cells, consistent with its NLS.","method":"Subcellular localization by immunostaining/reporter assay","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2 — direct localization experiment linked to structural feature (NLS), single lab","pmids":["11594764"],"is_preprint":false},{"year":2004,"finding":"HACS1 (SAMSN1) is up-regulated by IL-4 in B cells through a STAT6-dependent mechanism that can also be impaired by inhibitors of PI3K, PKC, and NF-κB; HACS1 associates with tyrosine-phosphorylated proteins after B cell activation and binds in vitro to the inhibitory receptor paired Ig-like receptor B (PirB).","method":"Immunoblot, signaling inhibitor experiments, in vitro binding assay, siRNA knockdown, overexpression","journal":"The Journal of experimental medicine","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal methods (signaling inhibitors, in vitro binding, KD, OE with phenotype), replicated pathway placement","pmids":["15381729"],"is_preprint":false},{"year":2009,"finding":"Hacs1 (SAMSN1) functions as an immunoinhibitory adaptor in B cells; Hacs1-/- mice (with SH3 and SAM domains deleted) show increased global tyrosine phosphorylation including Lyn and Akt kinases, increased BCR-stimulated proliferation, and enhanced humoral responses, placing HACS1 as a negative regulator of BCR signaling.","method":"Genetic knockout mouse model, phosphotyrosine immunoblot, flow cytometry, immunization assays","journal":"FASEB journal","confidence":"High","confidence_rationale":"Tier 2 — clean KO with defined molecular and cellular phenotypes, multiple orthogonal readouts","pmids":["19923443"],"is_preprint":false},{"year":2010,"finding":"SLy2 (SAMSN1) is phosphorylated and directly interacts with 14-3-3 proteins via a phosphorylation site, which retains phosphorylated SLy2 in the cytoplasm to control nucleo-cytoplasmic shuttling. In the nucleus, SLy2 interacts with the SAP30/HDAC1 complex and regulates HDAC1 activity.","method":"Immunoprecipitation, phosphorylation mapping, subcellular fractionation, HDAC activity assay","journal":"The international journal of biochemistry & cell biology","confidence":"High","confidence_rationale":"Tier 1-2 — direct binding assays with functional validation (HDAC activity), identification of phosphorylation site and reader (14-3-3), multiple orthogonal methods","pmids":["20478393"],"is_preprint":false},{"year":2011,"finding":"SLy2 (SAMSN1) induces Rac1-dependent membrane ruffle formation and regulates cell spreading and polarization; the SH3 domain is essential for these effects and directly interacts with the actin nucleation-promoting factor cortactin; SLy2-transgenic B cells are severely defective in cell spreading.","method":"Transgenic mouse overexpression, immunoprecipitation, confocal microscopy, Rac1 inhibition, domain mutagenesis","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 — reciprocal Co-IP, defined domain requirement, in vivo transgenic phenotype, multiple orthogonal methods","pmids":["21296879"],"is_preprint":false},{"year":2014,"finding":"SLy2 (SAMSN1) overexpression attenuates IL-5 receptor α chain expression on B-1 cells, resulting in decreased B-1 cell numbers and decreased differentiation into antibody-secreting cells.","method":"Transgenic mouse model, flow cytometry, ELISA","journal":"European journal of immunology","confidence":"Medium","confidence_rationale":"Tier 2 — transgenic in vivo model with defined molecular mechanism (IL-5Rα), single lab","pmids":["25330943"],"is_preprint":false},{"year":2020,"finding":"The HACS1 (SAMSN1) SH3 domain binds a sequence near the third ITIM (ITIM3) of paired immunoglobulin receptor B (PIRB) with micromolar affinity comparable to SHP2 N-SH2, using an atypical binding mode mapped by NMR chemical shift perturbation; molecular modeling suggests HACS1 SH3 and SHP2 SH2 cannot simultaneously bind PIRB ITIM3.","method":"Surface plasmon resonance, NMR structure determination, chemical shift mapping, molecular modeling","journal":"Communications biology","confidence":"High","confidence_rationale":"Tier 1 — NMR structure with binding site mapping, SPR quantitative affinity measurement, multiple orthogonal biophysical methods","pmids":["33188360"],"is_preprint":false},{"year":2022,"finding":"Macrophage SAMSN1 directly binds to GAB1 to prevent its protein degradation, subsequently enhancing PKA/AMPKα2 activation in a SHP2-dependent manner; this pathway mediates protection against LPS-induced inflammation and acute lung injury.","method":"Macrophage-specific KO and transgenic mice, co-immunoprecipitation, bone marrow transplantation, adoptive transfer, in vitro BMDM assays","journal":"Redox biology","confidence":"High","confidence_rationale":"Tier 2 — direct binding (Co-IP), multiple genetic models (KO + transgenic), in vivo and in vitro mechanistic validation","pmids":["35981417"],"is_preprint":false},{"year":2023,"finding":"Brn4 transcription factor binds to the Samsn1 promoter and upregulates its expression; Samsn1 mediates Brn4-induced inhibition of hippocampal neural stem cell proliferation and promotion of neuronal differentiation.","method":"ChIP, dual luciferase reporter assay, RNA-seq, siRNA knockdown, EdU incorporation, immunofluorescence","journal":"Stem cells international","confidence":"Medium","confidence_rationale":"Tier 2 — ChIP and reporter assay confirm promoter binding; KD with defined cellular phenotype, single lab","pmids":["37091532"],"is_preprint":false},{"year":2025,"finding":"In macrophages, SAMSN1 binds to KEAP1, causing NRF2 to dissociate from the KEAP1-NRF2 complex and translocate into the nucleus, promoting transcription of coinhibitory molecules CD48/CD86/CEACAM1 that bind receptors 2B4/CD152/TIM3 on T cells and induce T-cell exhaustion.","method":"CRISPR/Cas9 KO in RAW264.7, KO mice, flow cytometry, co-immunoprecipitation, primary cell co-culture","journal":"Chinese medical journal","confidence":"Medium","confidence_rationale":"Tier 2 — direct binding (Co-IP of SAMSN1-KEAP1), CRISPR KO with defined molecular and cellular phenotype, single lab","pmids":["40293473"],"is_preprint":false},{"year":2026,"finding":"SAMSN1 functions as an NK cell checkpoint in hepatocellular carcinoma; NK cell-specific deletion of Samsn1 reduces tumor burden and enhances granzyme B production, demonstrating SAMSN1 suppresses NK cell activation, proliferation, and granzyme B production in the tumor microenvironment.","method":"NK cell-specific conditional KO mice (Samsn1f/f-Ncr1Cre+), orthotopic tumor model, scRNA-seq, flow cytometry","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 — cell-type-specific genetic deletion with defined molecular (granzyme B) and in vivo tumor phenotype, rigorous genetic design","pmids":["41565668"],"is_preprint":false}],"current_model":"SAMSN1 is a multi-domain adaptor protein (SH3, SAM, NLS) that functions as an immunoinhibitory scaffold: its SH3 domain binds partners including cortactin (regulating actin dynamics/cell spreading via Rac1), PirB/ITIM3 (competing with SHP2), and GAB1 (stabilizing it to activate PKA/AMPKα2 signaling); its phosphorylation controls nucleo-cytoplasmic shuttling via 14-3-3 binding, while nuclear SAMSN1 interacts with the SAP30/HDAC1 complex to regulate gene expression; in macrophages SAMSN1 also binds KEAP1 to release NRF2 and drive coinhibitory molecule transcription, suppressing T-cell activity, and in NK cells SAMSN1 restrains granzyme B production and anti-tumor cytotoxicity."},"narrative":{"teleology":[{"year":2001,"claim":"Identification of SAMSN1 as an SH3- and SAM-domain adaptor with cell-type-dependent subcellular distribution established the basic architecture and raised the question of how localization is regulated.","evidence":"Immunostaining, cellular fractionation, and domain analysis in B-lineage and mast cells","pmids":["11536050","11594764"],"confidence":"Medium","gaps":["No binding partners identified","Mechanism controlling nuclear vs. cytoplasmic localization unknown","Functional consequence of either localization uncharacterized"]},{"year":2004,"claim":"Demonstrating that SAMSN1 is induced by IL-4/STAT6 in B cells and binds the inhibitory receptor PirB placed it within an immunoinhibitory signaling axis downstream of cytokine and BCR stimulation.","evidence":"Immunoblot, signaling inhibitors, in vitro binding assay in primary B cells","pmids":["15381729"],"confidence":"High","gaps":["In vivo relevance of PirB interaction not tested","Domain mediating PirB interaction not mapped"]},{"year":2009,"claim":"Genetic knockout revealed SAMSN1 as a bona fide negative regulator of BCR signaling, resolving whether it is stimulatory or inhibitory in B cells.","evidence":"Hacs1−/− mice with phosphotyrosine immunoblot, proliferation, and humoral response assays","pmids":["19923443"],"confidence":"High","gaps":["Downstream phosphatase or kinase target not identified","Whether phenotype is cell-intrinsic not fully resolved"]},{"year":2010,"claim":"Discovery that phosphorylation creates a 14-3-3 binding site to retain SAMSN1 in the cytoplasm, while nuclear SAMSN1 engages SAP30/HDAC1, explained how its localization is regulated and linked it to chromatin-level gene control.","evidence":"Phosphorylation mapping, co-immunoprecipitation with 14-3-3 and SAP30/HDAC1, HDAC activity assay","pmids":["20478393"],"confidence":"High","gaps":["Kinase responsible for the regulatory phosphorylation not identified","Target genes controlled via HDAC1 not defined"]},{"year":2011,"claim":"Mapping the SH3 domain–cortactin interaction and its requirement for Rac1-dependent membrane ruffling established a cytoskeletal effector mechanism and explained the B-cell spreading defect in SAMSN1 transgenic mice.","evidence":"Reciprocal co-IP, domain mutagenesis, Rac1 inhibition, transgenic B-cell spreading assays","pmids":["21296879"],"confidence":"High","gaps":["How cortactin engagement activates Rac1 not delineated","Relevance of actin remodeling to immune inhibition unclear"]},{"year":2020,"claim":"NMR structural mapping of the SAMSN1 SH3–PirB ITIM3 interface at atomic resolution, with affinity comparable to SHP2, explained how SAMSN1 could compete with SHP2 for inhibitory receptor engagement.","evidence":"NMR chemical shift perturbation, SPR affinity measurement, molecular modeling","pmids":["33188360"],"confidence":"High","gaps":["Competition with SHP2 not validated in living cells","Functional consequence of displacing SHP2 from PirB not shown"]},{"year":2022,"claim":"In macrophages, SAMSN1 was shown to stabilize GAB1 and activate PKA/AMPKα2 in a SHP2-dependent manner, extending its function beyond lymphocytes to myeloid anti-inflammatory signaling.","evidence":"Macrophage-specific KO and transgenic mice, Co-IP, LPS-induced acute lung injury model","pmids":["35981417"],"confidence":"High","gaps":["Mechanism by which SAMSN1 prevents GAB1 degradation not defined","Whether GAB1 axis operates in lymphocytes unknown"]},{"year":2023,"claim":"Identification of Brn4 as a direct transcriptional activator of Samsn1 that mediates neural stem cell differentiation expanded SAMSN1 function beyond the immune system.","evidence":"ChIP, luciferase reporter, siRNA knockdown, EdU incorporation in hippocampal neural stem cells","pmids":["37091532"],"confidence":"Medium","gaps":["Downstream effector pathway in neural stem cells not mapped","Single-lab finding in one cell model","Whether immune-relevant SAMSN1 partners operate in neural cells unknown"]},{"year":2025,"claim":"SAMSN1 was found to bind KEAP1, releasing NRF2 to drive transcription of coinhibitory molecules (CD48/CD86/CEACAM1) in macrophages, providing a direct mechanism for SAMSN1-mediated T-cell exhaustion.","evidence":"CRISPR KO in RAW264.7, KO mice, Co-IP of SAMSN1–KEAP1, T-cell co-culture","pmids":["40293473"],"confidence":"Medium","gaps":["Single-lab finding not yet independently replicated","Structural basis of SAMSN1–KEAP1 interaction not characterized","Whether this axis operates in other antigen-presenting cells unknown"]},{"year":2026,"claim":"NK cell–specific conditional deletion established SAMSN1 as an NK cell immune checkpoint that suppresses granzyme B and antitumor cytotoxicity, broadening its role from adaptive to innate lymphocyte regulation.","evidence":"Samsn1f/f-Ncr1Cre+ conditional KO, orthotopic HCC model, scRNA-seq, flow cytometry","pmids":["41565668"],"confidence":"High","gaps":["Direct molecular target suppressing granzyme B transcription/translation not identified","Whether therapeutic anti-SAMSN1 strategies are feasible in human NK cells unknown"]},{"year":null,"claim":"The kinase(s) controlling SAMSN1 phosphorylation and 14-3-3 retention, the target genes regulated via SAP30/HDAC1, and whether the KEAP1–NRF2 and GAB1 axes converge in the same cell types remain unresolved.","evidence":"","pmids":[],"confidence":"Low","gaps":["No kinase identified for the regulatory phosphorylation site","HDAC1-dependent target genes not defined","Integration of KEAP1/NRF2 and GAB1/PKA pathways not tested"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[0,3,4,5,8]}],"localization":[{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[0,4]},{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[1,4]}],"pathway":[{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[2,3,5,6,10,11]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[2,3,8]}],"complexes":["SAP30/HDAC1 complex"],"partners":["CORT","PIRB","GAB1","KEAP1","YWHAB","SAP30","HDAC1"],"other_free_text":[]},"mechanistic_narrative":"SAMSN1 is a multi-domain immunoinhibitory adaptor protein that negatively regulates lymphocyte and myeloid cell signaling through diverse protein–protein interactions. Its SH3 domain binds cortactin to control Rac1-dependent actin dynamics and cell spreading, engages the inhibitory receptor PirB/ITIM3 in competition with SHP2, and in macrophages stabilizes GAB1 to activate PKA/AMPKα2 signaling [PMID:21296879, PMID:33188360, PMID:35981417]. Phosphorylation-dependent 14-3-3 binding retains SAMSN1 in the cytoplasm, whereas nuclear SAMSN1 associates with the SAP30/HDAC1 complex to regulate gene expression; in macrophages it also binds KEAP1 to liberate NRF2, driving transcription of coinhibitory molecules that suppress T-cell function [PMID:20478393, PMID:40293473]. Genetic deletion in B cells augments BCR signaling and humoral responses, while NK cell–specific loss enhances granzyme B production and antitumor cytotoxicity, establishing SAMSN1 as a broad immune checkpoint [PMID:19923443, PMID:41565668]."},"prefetch_data":{"uniprot":{"accession":"Q9NSI8","full_name":"SAM domain-containing protein SAMSN-1","aliases":["Hematopoietic adaptor containing SH3 and SAM domains 1","Nash1","SAM domain, SH3 domain and nuclear localization signals protein 1","SH3-SAM adaptor protein"],"length_aa":373,"mass_kda":41.7,"function":"Negative regulator of B-cell activation. Down-regulates cell proliferation (in vitro). Promotes RAC1-dependent membrane ruffle formation and reorganization of the actin cytoskeleton. Regulates cell spreading and cell polarization. Stimulates HDAC1 activity. Regulates LYN activity by modulating its tyrosine phosphorylation (By similarity)","subcellular_location":"Nucleus; Cytoplasm; Cell projection, ruffle","url":"https://www.uniprot.org/uniprotkb/Q9NSI8/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/SAMSN1","classification":"Not Classified","n_dependent_lines":2,"n_total_lines":1208,"dependency_fraction":0.0016556291390728477},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/SAMSN1","total_profiled":1310},"omim":[{"mim_id":"607978","title":"SAM DOMAIN, SH3 DOMAIN, AND NUCLEAR LOCALIZATION SIGNALS 1; SAMSN1","url":"https://www.omim.org/entry/607978"},{"mim_id":"605413","title":"RAB, MEMBER OF RAS ONCOGENE FAMILY-LIKE 2B; RABL2B","url":"https://www.omim.org/entry/605413"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Plasma membrane","reliability":"Approved"},{"location":"Nucleoplasm","reliability":"Additional"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"bone marrow","ntpm":182.2},{"tissue":"lymphoid tissue","ntpm":75.6}],"url":"https://www.proteinatlas.org/search/SAMSN1"},"hgnc":{"alias_symbol":["NASH1","SASH2","SH3D6B","HACS1","SLy2"],"prev_symbol":[]},"alphafold":{"accession":"Q9NSI8","domains":[{"cath_id":"2.30.30.40","chopping":"167-223","consensus_level":"high","plddt":95.0304,"start":167,"end":223},{"cath_id":"1.10.150.50","chopping":"247-310","consensus_level":"high","plddt":87.3311,"start":247,"end":310}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9NSI8","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9NSI8-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9NSI8-F1-predicted_aligned_error_v6.png","plddt_mean":63.34},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=SAMSN1","jax_strain_url":"https://www.jax.org/strain/search?query=SAMSN1"},"sequence":{"accession":"Q9NSI8","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9NSI8.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9NSI8/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9NSI8"}},"corpus_meta":[{"pmid":"11536050","id":"PMC_11536050","title":"HACS1 encodes a novel SH3-SAM adaptor protein differentially expressed in normal and malignant hematopoietic cells.","date":"2001","source":"Oncogene","url":"https://pubmed.ncbi.nlm.nih.gov/11536050","citation_count":57,"is_preprint":false},{"pmid":"15381729","id":"PMC_15381729","title":"The SH3-SAM adaptor HACS1 is up-regulated in B cell activation signaling cascades.","date":"2004","source":"The Journal of experimental medicine","url":"https://pubmed.ncbi.nlm.nih.gov/15381729","citation_count":51,"is_preprint":false},{"pmid":"25117979","id":"PMC_25117979","title":"SAMSN1 is a tumor suppressor gene in multiple myeloma.","date":"2014","source":"Neoplasia (New York, N.Y.)","url":"https://pubmed.ncbi.nlm.nih.gov/25117979","citation_count":43,"is_preprint":false},{"pmid":"35981417","id":"PMC_35981417","title":"Macrophage SAMSN1 protects against sepsis-induced acute lung injury in mice.","date":"2022","source":"Redox biology","url":"https://pubmed.ncbi.nlm.nih.gov/35981417","citation_count":29,"is_preprint":false},{"pmid":"21296879","id":"PMC_21296879","title":"Immunoinhibitory adapter protein Src homology domain 3 lymphocyte protein 2 (SLy2) regulates actin dynamics and B cell spreading.","date":"2011","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/21296879","citation_count":26,"is_preprint":false},{"pmid":"19923443","id":"PMC_19923443","title":"Enhanced adaptive immunity in mice lacking the immunoinhibitory adaptor Hacs1.","date":"2009","source":"FASEB journal : official publication of the Federation of American Societies for Experimental Biology","url":"https://pubmed.ncbi.nlm.nih.gov/19923443","citation_count":24,"is_preprint":false},{"pmid":"11594764","id":"PMC_11594764","title":"Identification of Nash1, a novel protein containing a nuclear localization signal, a sterile alpha motif, and an SH3 domain preferentially expressed in mast cells.","date":"2001","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/11594764","citation_count":18,"is_preprint":false},{"pmid":"25805236","id":"PMC_25805236","title":"Suppression of SAMSN1 Expression is Associated with the Malignant Phenotype of Hepatocellular Carcinoma.","date":"2015","source":"Annals of surgical oncology","url":"https://pubmed.ncbi.nlm.nih.gov/25805236","citation_count":18,"is_preprint":false},{"pmid":"20478393","id":"PMC_20478393","title":"SLy2 targets the nuclear SAP30/HDAC1 complex.","date":"2010","source":"The international journal of biochemistry & cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/20478393","citation_count":15,"is_preprint":false},{"pmid":"32923989","id":"PMC_32923989","title":"Characterization of the role of Samsn1 loss in multiple myeloma development.","date":"2020","source":"FASEB bioAdvances","url":"https://pubmed.ncbi.nlm.nih.gov/32923989","citation_count":8,"is_preprint":false},{"pmid":"25330943","id":"PMC_25330943","title":"SLy2 controls the antibody response to pneumococcal vaccine through an IL-5Rα-dependent mechanism in B-1 cells.","date":"2014","source":"European journal of immunology","url":"https://pubmed.ncbi.nlm.nih.gov/25330943","citation_count":7,"is_preprint":false},{"pmid":"33188360","id":"PMC_33188360","title":"HACS1 signaling adaptor protein recognizes a motif in the paired immunoglobulin receptor B cytoplasmic domain.","date":"2020","source":"Communications biology","url":"https://pubmed.ncbi.nlm.nih.gov/33188360","citation_count":5,"is_preprint":false},{"pmid":"33098380","id":"PMC_33098380","title":"SLy2-deficiency promotes B-1 cell immunity and triggers enhanced production of IgM and IgG2 antibodies against pneumococcal vaccine.","date":"2020","source":"Immunity, inflammation and disease","url":"https://pubmed.ncbi.nlm.nih.gov/33098380","citation_count":5,"is_preprint":false},{"pmid":"40293473","id":"PMC_40293473","title":"SAMSN1 causes sepsis immunosuppression by inducing macrophages to express coinhibitory molecules that cause T-cell exhaustion via KEAP1-NRF2 signaling.","date":"2025","source":"Chinese medical journal","url":"https://pubmed.ncbi.nlm.nih.gov/40293473","citation_count":4,"is_preprint":false},{"pmid":"33592135","id":"PMC_33592135","title":"SLy2-overexpression impairs B-cell development in the bone marrow and the IgG response towards pneumococcal conjugate-vaccine.","date":"2021","source":"Immunity, inflammation and disease","url":"https://pubmed.ncbi.nlm.nih.gov/33592135","citation_count":3,"is_preprint":false},{"pmid":"37786523","id":"PMC_37786523","title":"Suppression of SAMSN1 contributes to neuroprotection in neonatal rats suffering from hypoxic-ischemic encephalopathy injury.","date":"2022","source":"Ibrain","url":"https://pubmed.ncbi.nlm.nih.gov/37786523","citation_count":3,"is_preprint":false},{"pmid":"37091532","id":"PMC_37091532","title":"Lama2 And Samsn1 Mediate the Effects of Brn4 on Hippocampal Neural Stem Cell Proliferation and Differentiation.","date":"2023","source":"Stem cells international","url":"https://pubmed.ncbi.nlm.nih.gov/37091532","citation_count":3,"is_preprint":false},{"pmid":"41565668","id":"PMC_41565668","title":"SAMSN1 restrains NK cell mediated anti-tumor immunity in hepatocellular carcinoma.","date":"2026","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/41565668","citation_count":0,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2024.10.03.24314746","title":"SAMSN1 causes sepsis immunosuppression by inducing macrophages to express coinhibitory molecules that causes T cell exhaustion via KEAP1-NRF2 signaling","date":"2024-10-06","source":"bioRxiv","url":"https://doi.org/10.1101/2024.10.03.24314746","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":11312,"output_tokens":2814,"usd":0.038073},"stage2":{"model":"claude-opus-4-6","input_tokens":6175,"output_tokens":2498,"usd":0.139987},"total_usd":0.17806,"stage1_batch_id":"msgbatch_011rkcQdVV1RaFq9XhcG6df6","stage2_batch_id":"msgbatch_01RzgrJafdF4EWHhj5mNi6dh","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2001,\n      \"finding\": \"HACS1 (SAMSN1) encodes a 441 amino acid adaptor protein containing an SH3 domain (most similar to Crk) and a SAM domain, and is localized predominantly to the cytoplasm as determined by immunostaining and cellular fractionation.\",\n      \"method\": \"Immunostaining and cellular fractionation; domain analysis\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct fractionation experiment with functional domain characterization, single lab\",\n      \"pmids\": [\"11536050\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"Nash1 (SAMSN1), which contains a nuclear localization signal (NLS), SAM, and SH3 domain, localizes to the nucleus in mast cells, consistent with its NLS.\",\n      \"method\": \"Subcellular localization by immunostaining/reporter assay\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct localization experiment linked to structural feature (NLS), single lab\",\n      \"pmids\": [\"11594764\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"HACS1 (SAMSN1) is up-regulated by IL-4 in B cells through a STAT6-dependent mechanism that can also be impaired by inhibitors of PI3K, PKC, and NF-κB; HACS1 associates with tyrosine-phosphorylated proteins after B cell activation and binds in vitro to the inhibitory receptor paired Ig-like receptor B (PirB).\",\n      \"method\": \"Immunoblot, signaling inhibitor experiments, in vitro binding assay, siRNA knockdown, overexpression\",\n      \"journal\": \"The Journal of experimental medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods (signaling inhibitors, in vitro binding, KD, OE with phenotype), replicated pathway placement\",\n      \"pmids\": [\"15381729\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Hacs1 (SAMSN1) functions as an immunoinhibitory adaptor in B cells; Hacs1-/- mice (with SH3 and SAM domains deleted) show increased global tyrosine phosphorylation including Lyn and Akt kinases, increased BCR-stimulated proliferation, and enhanced humoral responses, placing HACS1 as a negative regulator of BCR signaling.\",\n      \"method\": \"Genetic knockout mouse model, phosphotyrosine immunoblot, flow cytometry, immunization assays\",\n      \"journal\": \"FASEB journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — clean KO with defined molecular and cellular phenotypes, multiple orthogonal readouts\",\n      \"pmids\": [\"19923443\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"SLy2 (SAMSN1) is phosphorylated and directly interacts with 14-3-3 proteins via a phosphorylation site, which retains phosphorylated SLy2 in the cytoplasm to control nucleo-cytoplasmic shuttling. In the nucleus, SLy2 interacts with the SAP30/HDAC1 complex and regulates HDAC1 activity.\",\n      \"method\": \"Immunoprecipitation, phosphorylation mapping, subcellular fractionation, HDAC activity assay\",\n      \"journal\": \"The international journal of biochemistry & cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — direct binding assays with functional validation (HDAC activity), identification of phosphorylation site and reader (14-3-3), multiple orthogonal methods\",\n      \"pmids\": [\"20478393\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"SLy2 (SAMSN1) induces Rac1-dependent membrane ruffle formation and regulates cell spreading and polarization; the SH3 domain is essential for these effects and directly interacts with the actin nucleation-promoting factor cortactin; SLy2-transgenic B cells are severely defective in cell spreading.\",\n      \"method\": \"Transgenic mouse overexpression, immunoprecipitation, confocal microscopy, Rac1 inhibition, domain mutagenesis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal Co-IP, defined domain requirement, in vivo transgenic phenotype, multiple orthogonal methods\",\n      \"pmids\": [\"21296879\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"SLy2 (SAMSN1) overexpression attenuates IL-5 receptor α chain expression on B-1 cells, resulting in decreased B-1 cell numbers and decreased differentiation into antibody-secreting cells.\",\n      \"method\": \"Transgenic mouse model, flow cytometry, ELISA\",\n      \"journal\": \"European journal of immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — transgenic in vivo model with defined molecular mechanism (IL-5Rα), single lab\",\n      \"pmids\": [\"25330943\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"The HACS1 (SAMSN1) SH3 domain binds a sequence near the third ITIM (ITIM3) of paired immunoglobulin receptor B (PIRB) with micromolar affinity comparable to SHP2 N-SH2, using an atypical binding mode mapped by NMR chemical shift perturbation; molecular modeling suggests HACS1 SH3 and SHP2 SH2 cannot simultaneously bind PIRB ITIM3.\",\n      \"method\": \"Surface plasmon resonance, NMR structure determination, chemical shift mapping, molecular modeling\",\n      \"journal\": \"Communications biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — NMR structure with binding site mapping, SPR quantitative affinity measurement, multiple orthogonal biophysical methods\",\n      \"pmids\": [\"33188360\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Macrophage SAMSN1 directly binds to GAB1 to prevent its protein degradation, subsequently enhancing PKA/AMPKα2 activation in a SHP2-dependent manner; this pathway mediates protection against LPS-induced inflammation and acute lung injury.\",\n      \"method\": \"Macrophage-specific KO and transgenic mice, co-immunoprecipitation, bone marrow transplantation, adoptive transfer, in vitro BMDM assays\",\n      \"journal\": \"Redox biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — direct binding (Co-IP), multiple genetic models (KO + transgenic), in vivo and in vitro mechanistic validation\",\n      \"pmids\": [\"35981417\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Brn4 transcription factor binds to the Samsn1 promoter and upregulates its expression; Samsn1 mediates Brn4-induced inhibition of hippocampal neural stem cell proliferation and promotion of neuronal differentiation.\",\n      \"method\": \"ChIP, dual luciferase reporter assay, RNA-seq, siRNA knockdown, EdU incorporation, immunofluorescence\",\n      \"journal\": \"Stem cells international\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — ChIP and reporter assay confirm promoter binding; KD with defined cellular phenotype, single lab\",\n      \"pmids\": [\"37091532\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"In macrophages, SAMSN1 binds to KEAP1, causing NRF2 to dissociate from the KEAP1-NRF2 complex and translocate into the nucleus, promoting transcription of coinhibitory molecules CD48/CD86/CEACAM1 that bind receptors 2B4/CD152/TIM3 on T cells and induce T-cell exhaustion.\",\n      \"method\": \"CRISPR/Cas9 KO in RAW264.7, KO mice, flow cytometry, co-immunoprecipitation, primary cell co-culture\",\n      \"journal\": \"Chinese medical journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct binding (Co-IP of SAMSN1-KEAP1), CRISPR KO with defined molecular and cellular phenotype, single lab\",\n      \"pmids\": [\"40293473\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"SAMSN1 functions as an NK cell checkpoint in hepatocellular carcinoma; NK cell-specific deletion of Samsn1 reduces tumor burden and enhances granzyme B production, demonstrating SAMSN1 suppresses NK cell activation, proliferation, and granzyme B production in the tumor microenvironment.\",\n      \"method\": \"NK cell-specific conditional KO mice (Samsn1f/f-Ncr1Cre+), orthotopic tumor model, scRNA-seq, flow cytometry\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — cell-type-specific genetic deletion with defined molecular (granzyme B) and in vivo tumor phenotype, rigorous genetic design\",\n      \"pmids\": [\"41565668\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"SAMSN1 is a multi-domain adaptor protein (SH3, SAM, NLS) that functions as an immunoinhibitory scaffold: its SH3 domain binds partners including cortactin (regulating actin dynamics/cell spreading via Rac1), PirB/ITIM3 (competing with SHP2), and GAB1 (stabilizing it to activate PKA/AMPKα2 signaling); its phosphorylation controls nucleo-cytoplasmic shuttling via 14-3-3 binding, while nuclear SAMSN1 interacts with the SAP30/HDAC1 complex to regulate gene expression; in macrophages SAMSN1 also binds KEAP1 to release NRF2 and drive coinhibitory molecule transcription, suppressing T-cell activity, and in NK cells SAMSN1 restrains granzyme B production and anti-tumor cytotoxicity.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"SAMSN1 is a multi-domain immunoinhibitory adaptor protein that negatively regulates lymphocyte and myeloid cell signaling through diverse protein–protein interactions. Its SH3 domain binds cortactin to control Rac1-dependent actin dynamics and cell spreading, engages the inhibitory receptor PirB/ITIM3 in competition with SHP2, and in macrophages stabilizes GAB1 to activate PKA/AMPKα2 signaling [PMID:21296879, PMID:33188360, PMID:35981417]. Phosphorylation-dependent 14-3-3 binding retains SAMSN1 in the cytoplasm, whereas nuclear SAMSN1 associates with the SAP30/HDAC1 complex to regulate gene expression; in macrophages it also binds KEAP1 to liberate NRF2, driving transcription of coinhibitory molecules that suppress T-cell function [PMID:20478393, PMID:40293473]. Genetic deletion in B cells augments BCR signaling and humoral responses, while NK cell–specific loss enhances granzyme B production and antitumor cytotoxicity, establishing SAMSN1 as a broad immune checkpoint [PMID:19923443, PMID:41565668].\",\n  \"teleology\": [\n    {\n      \"year\": 2001,\n      \"claim\": \"Identification of SAMSN1 as an SH3- and SAM-domain adaptor with cell-type-dependent subcellular distribution established the basic architecture and raised the question of how localization is regulated.\",\n      \"evidence\": \"Immunostaining, cellular fractionation, and domain analysis in B-lineage and mast cells\",\n      \"pmids\": [\"11536050\", \"11594764\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No binding partners identified\", \"Mechanism controlling nuclear vs. cytoplasmic localization unknown\", \"Functional consequence of either localization uncharacterized\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Demonstrating that SAMSN1 is induced by IL-4/STAT6 in B cells and binds the inhibitory receptor PirB placed it within an immunoinhibitory signaling axis downstream of cytokine and BCR stimulation.\",\n      \"evidence\": \"Immunoblot, signaling inhibitors, in vitro binding assay in primary B cells\",\n      \"pmids\": [\"15381729\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vivo relevance of PirB interaction not tested\", \"Domain mediating PirB interaction not mapped\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Genetic knockout revealed SAMSN1 as a bona fide negative regulator of BCR signaling, resolving whether it is stimulatory or inhibitory in B cells.\",\n      \"evidence\": \"Hacs1−/− mice with phosphotyrosine immunoblot, proliferation, and humoral response assays\",\n      \"pmids\": [\"19923443\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Downstream phosphatase or kinase target not identified\", \"Whether phenotype is cell-intrinsic not fully resolved\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Discovery that phosphorylation creates a 14-3-3 binding site to retain SAMSN1 in the cytoplasm, while nuclear SAMSN1 engages SAP30/HDAC1, explained how its localization is regulated and linked it to chromatin-level gene control.\",\n      \"evidence\": \"Phosphorylation mapping, co-immunoprecipitation with 14-3-3 and SAP30/HDAC1, HDAC activity assay\",\n      \"pmids\": [\"20478393\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Kinase responsible for the regulatory phosphorylation not identified\", \"Target genes controlled via HDAC1 not defined\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Mapping the SH3 domain–cortactin interaction and its requirement for Rac1-dependent membrane ruffling established a cytoskeletal effector mechanism and explained the B-cell spreading defect in SAMSN1 transgenic mice.\",\n      \"evidence\": \"Reciprocal co-IP, domain mutagenesis, Rac1 inhibition, transgenic B-cell spreading assays\",\n      \"pmids\": [\"21296879\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How cortactin engagement activates Rac1 not delineated\", \"Relevance of actin remodeling to immune inhibition unclear\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"NMR structural mapping of the SAMSN1 SH3–PirB ITIM3 interface at atomic resolution, with affinity comparable to SHP2, explained how SAMSN1 could compete with SHP2 for inhibitory receptor engagement.\",\n      \"evidence\": \"NMR chemical shift perturbation, SPR affinity measurement, molecular modeling\",\n      \"pmids\": [\"33188360\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Competition with SHP2 not validated in living cells\", \"Functional consequence of displacing SHP2 from PirB not shown\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"In macrophages, SAMSN1 was shown to stabilize GAB1 and activate PKA/AMPKα2 in a SHP2-dependent manner, extending its function beyond lymphocytes to myeloid anti-inflammatory signaling.\",\n      \"evidence\": \"Macrophage-specific KO and transgenic mice, Co-IP, LPS-induced acute lung injury model\",\n      \"pmids\": [\"35981417\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism by which SAMSN1 prevents GAB1 degradation not defined\", \"Whether GAB1 axis operates in lymphocytes unknown\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Identification of Brn4 as a direct transcriptional activator of Samsn1 that mediates neural stem cell differentiation expanded SAMSN1 function beyond the immune system.\",\n      \"evidence\": \"ChIP, luciferase reporter, siRNA knockdown, EdU incorporation in hippocampal neural stem cells\",\n      \"pmids\": [\"37091532\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Downstream effector pathway in neural stem cells not mapped\", \"Single-lab finding in one cell model\", \"Whether immune-relevant SAMSN1 partners operate in neural cells unknown\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"SAMSN1 was found to bind KEAP1, releasing NRF2 to drive transcription of coinhibitory molecules (CD48/CD86/CEACAM1) in macrophages, providing a direct mechanism for SAMSN1-mediated T-cell exhaustion.\",\n      \"evidence\": \"CRISPR KO in RAW264.7, KO mice, Co-IP of SAMSN1–KEAP1, T-cell co-culture\",\n      \"pmids\": [\"40293473\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single-lab finding not yet independently replicated\", \"Structural basis of SAMSN1–KEAP1 interaction not characterized\", \"Whether this axis operates in other antigen-presenting cells unknown\"]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"NK cell–specific conditional deletion established SAMSN1 as an NK cell immune checkpoint that suppresses granzyme B and antitumor cytotoxicity, broadening its role from adaptive to innate lymphocyte regulation.\",\n      \"evidence\": \"Samsn1f/f-Ncr1Cre+ conditional KO, orthotopic HCC model, scRNA-seq, flow cytometry\",\n      \"pmids\": [\"41565668\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct molecular target suppressing granzyme B transcription/translation not identified\", \"Whether therapeutic anti-SAMSN1 strategies are feasible in human NK cells unknown\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The kinase(s) controlling SAMSN1 phosphorylation and 14-3-3 retention, the target genes regulated via SAP30/HDAC1, and whether the KEAP1–NRF2 and GAB1 axes converge in the same cell types remain unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No kinase identified for the regulatory phosphorylation site\", \"HDAC1-dependent target genes not defined\", \"Integration of KEAP1/NRF2 and GAB1/PKA pathways not tested\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [0, 3, 4, 5, 8]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [0, 4]},\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [1, 4]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [2, 3, 5, 6, 10, 11]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [2, 3, 8]}\n    ],\n    \"complexes\": [\n      \"SAP30/HDAC1 complex\"\n    ],\n    \"partners\": [\n      \"CORT\",\n      \"PIRB\",\n      \"GAB1\",\n      \"KEAP1\",\n      \"YWHAB\",\n      \"SAP30\",\n      \"HDAC1\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}