{"gene":"GOLIM4","run_date":"2026-04-28T18:06:53","timeline":{"discoveries":[{"year":1997,"finding":"GPP130 (GOLIM4) is a type II integral membrane protein localized to the cis/medial Golgi with an unusually acidic lumenal domain and multiple coiled-coil regions. Overexpression causes accumulation in endocytic vesicles, and chloroquine treatment reversibly redistributes endogenous GPP130 to endocytic vesicles, demonstrating that its Golgi targeting is saturable and pH-sensitive, involving a retrieval mechanism for return to the Golgi.","method":"cDNA sequencing, overexpression, chloroquine treatment with immunofluorescence and electron microscopy, subcellular fractionation","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 2 — foundational study with multiple orthogonal methods, >100 citations, replicated in subsequent work","pmids":["9201717"],"is_preprint":false},{"year":2007,"finding":"GPP130 cycling is regulated at multiple stages: intra-Golgi cycling, trans-Golgi to endosome transport, and endosome-to-Golgi transport. pH perturbation (monensin) most strongly affects the trans-Golgi, the most acidic portion of the Golgi apparatus.","method":"Quantitative fluorescence microscopy with Shiga-like toxin B fragment as trafficking probe, tsO45-GFP as secretory marker, simulations of trafficking kinetics","journal":"Traffic (Copenhagen, Denmark)","confidence":"Medium","confidence_rationale":"Tier 2 — quantitative analysis with multiple probes but single lab","pmids":["17605763"],"is_preprint":false},{"year":2010,"finding":"Extracellular manganese (Mn) induces rapid redistribution of GPP130 from the cis-Golgi to multivesicular bodies via a Rab7-dependent pathway, followed by lysosomal degradation. The lumenal stem domain of GPP130 acts as a Mn sensor and is required and sufficient to confer Mn sensitivity to another cis-Golgi protein. The cytoplasmic domain is dispensable. GPP130 must be targeted to the cis-Golgi for the Mn response to occur.","method":"Immunofluorescence, domain deletion/swap experiments, Rab7 dominant-negative inhibition, live-cell imaging, pulse-chase degradation assays","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal methods including domain swaps and genetic inhibition, replicated across subsequent papers","pmids":["20130081"],"is_preprint":false},{"year":2013,"finding":"GPP130 directly binds the B subunit of Shiga toxin (STx) and STx1 via a seven-residue stretch in its lumenal stem domain adjacent to the transmembrane domain. This interaction is required for retrograde endosome-to-Golgi trafficking of STx/STx1. STx2 B subunit does not bind GPP130, explaining why Mn-induced GPP130 down-regulation fails to block STx2 trafficking.","method":"Pulldown with purified toxin B subunits, mutagenesis of GPP130 stem domain and toxin residues, cell-based Shiga toxin trafficking assays","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 1-2 — in vitro binding with purified proteins combined with mutagenesis and functional trafficking assay","pmids":["23761068"],"is_preprint":false},{"year":2013,"finding":"GPP130 degradation in response to Mn is specific to Mn among transition metals tested (cobalt, copper, iron, nickel, zinc did not induce degradation) and occurs at sub-micromolar extracellular Mn concentrations without detectable increases in intracellular Mn, demonstrating exquisite selectivity of the GPP130 Mn-sensing mechanism in neuronal cells and in vivo in rat brain.","method":"Immunofluorescence quantification in AF5 cells, western blot, in vivo rat subchronic Mn exposure model","journal":"Synapse (New York, N.Y.)","confidence":"Medium","confidence_rationale":"Tier 2 — metal specificity panel with in vivo validation, single lab","pmids":["23280773"],"is_preprint":false},{"year":2017,"finding":"Mn-induced exit of GPP130 from the trans-Golgi network toward lysosomes is mediated by the sorting receptor sortilin, which interacts with the lumenal stem domain of GPP130. Mn causes GPP130 to oligomerize/aggregate in the Golgi, and sortilin sorts these complexes for lysosomal delivery. In contrast, FM-domain-induced lysosomal trafficking of galactosyltransferase was sortilin-independent.","method":"Sortilin knockdown, Co-IP/interaction assays, domain deletion experiments, self-interacting FM domain aggregation system, immunofluorescence","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 2 — reciprocal interaction mapping with domain deletions, genetic knockdown, and mechanistic comparison with control protein","pmids":["28768823"],"is_preprint":false},{"year":2021,"finding":"RBFOX2 binds a GGAA motif in exon-7 of GOLIM4 pre-mRNA and promotes inclusion of exon-7, generating the long isoform GOLIM4-L. GOLIM4-L and RBFOX2 maintain Golgi apparatus organization and influence vesicle-mediated transport. RAB26 interacts with GOLIM4 and mediates its tumorigenic effects in NPC cells.","method":"Transcriptome splicing profiling, RBFOX2 knockdown/overexpression rescue experiments, Co-IP (GOLIM4-RAB26 interaction), luciferase splicing reporter, immunofluorescence of Golgi organization","journal":"Advanced science (Weinheim, Baden-Wurttemberg, Germany)","confidence":"Medium","confidence_rationale":"Tier 2-3 — Co-IP and functional rescue experiments from single lab with multiple methods","pmids":["34180133"],"is_preprint":false},{"year":2025,"finding":"GPP130 is a substrate of proprotein convertases PC7 (PCSK7) and Furin, which cleave/shed GPP130 into a membrane-bound N-terminal product and secreted C-terminal fragments. GPP130 overexpression increases cell proliferation in A549, SKOV3, and HeLa cells, and this proliferative activity is enhanced upon cleavage by PC7 and/or Furin.","method":"Cell-based cleavage assays, overexpression and knockdown, proliferation assays, western blot for cleavage products","journal":"International journal of molecular sciences","confidence":"Medium","confidence_rationale":"Tier 2-3 — cell-based substrate cleavage assays with functional readout, single lab","pmids":["40649939"],"is_preprint":false},{"year":2025,"finding":"Monensin increases Golgi lumenal pH, inducing rapid exocytosis of GOLIM4 from the Golgi. GOLIM4 regulates cell motility and adhesion by modulating post-Golgi trafficking of Talin 1 (TLN1), an essential focal adhesion component. Both GOLIM4 and TLN1 are direct targets of microRNA-200b, which is suppressed during EMT.","method":"Monensin treatment with live-cell imaging, GOLIM4 and TLN1 knockdown, migration assays, microRNA-200b target validation, Golgi pH measurement","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"Medium","confidence_rationale":"Tier 2 — multiple functional assays with mechanistic pathway placement, single lab","pmids":["40632561"],"is_preprint":false},{"year":2024,"finding":"IRE1α regulates GOLIM4 expression via the XBP1s transcription factor downstream of ER stress. GOLIM4 silencing reduces surface expression of MHC class I molecules, growth factor receptors (PDGFRA, IL13RA2), and adhesion/migration proteins (CD44, CD54, NCAM1, ITGB1, CD90) without affecting their mRNA levels, demonstrating that GOLIM4 controls post-transcriptional surface trafficking of these molecules. GOLIM4 silencing impairs glioblastoma cell-cell adhesion and migration.","method":"IRE1 inhibition, XBP1s overexpression, GOLIM4 siRNA knockdown, flow cytometry for surface protein expression, qRT-PCR to exclude transcriptional effects, cell adhesion and migration assays","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 2 — multiple orthogonal methods establishing pathway (IRE1/XBP1s/GOLIM4) with functional surface trafficking readout, preprint","pmids":["bio_10.1101_2024.10.22.619629"],"is_preprint":true},{"year":2021,"finding":"miR-105-3p directly targets the GOLIM4 3'UTR (validated by luciferase reporter assay) and suppresses GOLIM4 expression, promoting breast cancer cell proliferation and metastasis.","method":"Luciferase reporter assay, GOLIM4 silencing rescue experiment, CCK-8, Transwell, TUNEL assays","journal":"BMC cancer","confidence":"Low","confidence_rationale":"Tier 3 — single lab, luciferase target validation with functional rescue but no direct mechanistic insight into GOLIM4 function","pmids":["33722196"],"is_preprint":false}],"current_model":"GOLIM4/GPP130 is a type II cis-Golgi membrane protein whose lumenal stem domain acts as a manganese (Mn) sensor; elevated Mn causes GPP130 oligomerization in the Golgi, which is recognized by the sorting receptor sortilin and diverts GPP130 via a Rab7-dependent pathway to lysosomes for degradation. In its normal cycling role, GPP130 serves as an endosome-to-Golgi retrograde trafficking receptor for Shiga toxin (STx/STx1) by directly binding the toxin B subunit through a seven-residue stretch in its stem domain. GOLIM4 also regulates post-Golgi trafficking of surface proteins including focal adhesion component Talin 1, and its expression is transcriptionally controlled downstream of the IRE1/XBP1s ER stress axis; it can be proteolytically shed by PC7/Furin to generate fragments that promote cell proliferation."},"narrative":{"teleology":[{"year":1997,"claim":"Establishing GOLIM4 as a cis-Golgi resident with a saturable, pH-dependent retrieval mechanism resolved how an integral membrane protein cycles through endocytic compartments yet maintains steady-state Golgi localization.","evidence":"cDNA cloning, overexpression-induced endosome accumulation, chloroquine redistribution assays with immunofluorescence and EM in cultured cells","pmids":["9201717"],"confidence":"High","gaps":["molecular determinants of the retrieval signal unknown","identity of retrieval receptor or coat machinery not determined"]},{"year":2007,"claim":"Quantitative dissection of GPP130 cycling kinetics revealed that its trafficking includes intra-Golgi, trans-Golgi-to-endosome, and endosome-to-Golgi steps, with pH perturbation (monensin) primarily affecting the trans-Golgi stage, clarifying where pH sensitivity operates.","evidence":"quantitative fluorescence microscopy with Shiga-like toxin B and tsO45-GFP probes, kinetic modeling","pmids":["17605763"],"confidence":"Medium","gaps":["molecular basis of pH sensitivity in the lumenal domain not identified","trans-Golgi sorting machinery not determined"]},{"year":2010,"claim":"Identification of the GPP130 lumenal stem domain as a manganese sensor that is necessary and sufficient for Mn-induced redistribution to multivesicular bodies and lysosomal degradation via Rab7 revealed a novel mechanism linking metal ion exposure to selective Golgi protein turnover.","evidence":"domain deletion/swap chimeras, Rab7 dominant-negative, live-cell imaging, pulse-chase degradation in cultured cells","pmids":["20130081"],"confidence":"High","gaps":["structural mechanism of Mn binding/sensing in the stem domain unknown","how Rab7-dependent pathway is engaged not determined"]},{"year":2013,"claim":"Demonstration that GPP130 directly binds STx/STx1 B subunit through a defined seven-residue stretch and is required for retrograde endosome-to-Golgi trafficking of these toxins established GPP130 as a bona fide cargo receptor, while explaining the selective inability of Mn-induced GPP130 depletion to block STx2.","evidence":"pulldowns with purified toxin B subunits, site-directed mutagenesis, cell-based toxin trafficking assays","pmids":["23761068"],"confidence":"High","gaps":["crystal structure of GPP130–STx B complex not available","whether additional endogenous cargoes use this binding site unknown"]},{"year":2013,"claim":"The metal specificity screen showed GPP130 degradation is exquisitely selective for Mn among transition metals and occurs at sub-micromolar concentrations in neuronal cells and in vivo in rat brain, establishing GPP130 as a physiologically relevant Mn indicator.","evidence":"metal panel (Co, Cu, Fe, Ni, Zn vs Mn) in AF5 cells, in vivo subchronic Mn exposure in rats","pmids":["23280773"],"confidence":"Medium","gaps":["direct Mn binding stoichiometry and affinity not measured","whether GPP130 degradation has a protective function in Mn homeostasis unclear"]},{"year":2017,"claim":"Identification of sortilin as the sorting receptor that recognizes Mn-induced GPP130 oligomers in the Golgi and directs them to lysosomes resolved the missing link between Mn sensing and degradative sorting.","evidence":"sortilin knockdown, Co-IP with domain deletions, FM-domain aggregation control, immunofluorescence","pmids":["28768823"],"confidence":"High","gaps":["structural basis for sortilin recognition of GPP130 oligomers unknown","whether oligomerization is directly triggered by Mn binding or indirectly by pH change not resolved"]},{"year":2021,"claim":"Discovery that RBFOX2-regulated alternative splicing of GOLIM4 exon-7 generates a long isoform (GOLIM4-L) important for Golgi integrity, and that GOLIM4 interacts with RAB26 to influence vesicle-mediated transport, expanded the functional repertoire beyond Mn sensing and toxin trafficking.","evidence":"splicing profiling, RBFOX2 knockdown/overexpression, Co-IP of GOLIM4–RAB26, luciferase splicing reporter in NPC cells","pmids":["34180133"],"confidence":"Medium","gaps":["functional difference between GOLIM4-L and short isoform not fully characterized","GOLIM4–RAB26 interaction not validated by reciprocal pull-down or structural methods"]},{"year":2025,"claim":"Establishing that proprotein convertases PC7 and Furin cleave GPP130 to generate secreted C-terminal fragments that enhance cell proliferation revealed a non-canonical signaling output of a Golgi trafficking receptor.","evidence":"cell-based cleavage assays with PC7/Furin overexpression and knockdown, proliferation assays in A549, SKOV3, HeLa cells","pmids":["40649939"],"confidence":"Medium","gaps":["identity of the receptor or pathway through which shed fragments promote proliferation unknown","cleavage sites not mapped at residue level","in vivo relevance not tested"]},{"year":2025,"claim":"Demonstration that GOLIM4 regulates post-Golgi trafficking of Talin 1 and thereby controls cell motility and adhesion, with both genes co-regulated by miR-200b during EMT, placed GOLIM4 in an epithelial-mesenchymal transition circuit beyond its canonical Golgi cycling role.","evidence":"monensin-induced exocytosis, GOLIM4/TLN1 knockdown, migration assays, miR-200b target validation, Golgi pH measurement","pmids":["40632561"],"confidence":"Medium","gaps":["mechanism by which GOLIM4 sorts TLN1 cargo not determined","direct GOLIM4–TLN1 interaction not demonstrated"]},{"year":null,"claim":"Major unresolved questions include the structural basis for manganese sensing in the lumenal stem domain, whether GOLIM4 has additional endogenous retrograde trafficking cargoes beyond Shiga toxin, and the physiological significance of PC7/Furin-generated GOLIM4 fragments in vivo.","evidence":"","pmids":[],"confidence":"Medium","gaps":["no atomic-resolution structure of GOLIM4 lumenal domain or its Mn-bound state","endogenous cargoes for the retrograde trafficking receptor function remain unidentified","in vivo role of shed GOLIM4 fragments untested"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0038024","term_label":"cargo receptor activity","supporting_discovery_ids":[3]},{"term_id":"GO:0140299","term_label":"molecular sensor activity","supporting_discovery_ids":[2,4]}],"localization":[{"term_id":"GO:0005794","term_label":"Golgi apparatus","supporting_discovery_ids":[0,1,2]},{"term_id":"GO:0005768","term_label":"endosome","supporting_discovery_ids":[0,2]},{"term_id":"GO:0005764","term_label":"lysosome","supporting_discovery_ids":[2,5]}],"pathway":[{"term_id":"R-HSA-5653656","term_label":"Vesicle-mediated transport","supporting_discovery_ids":[0,1,3,6]},{"term_id":"R-HSA-9609507","term_label":"Protein localization","supporting_discovery_ids":[3,8]},{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[5,7]}],"complexes":[],"partners":["SORT1","RAB7A","RAB26","PCSK7","FURIN","RBFOX2","TLN1"],"other_free_text":[]},"mechanistic_narrative":"GOLIM4 (GPP130) is a type II cis-Golgi membrane protein that functions as a pH-sensitive trafficking receptor cycling between the Golgi and endosomes, and as a manganese sensor that couples changes in lumenal metal ion concentration to regulated protein degradation. Its lumenal stem domain directly binds the Shiga toxin (STx/STx1) B subunit through a seven-residue stretch and is required for retrograde endosome-to-Golgi transport of the toxin; the same stem domain senses sub-micromolar manganese, triggering GPP130 oligomerization, recognition by the sorting receptor sortilin, and Rab7-dependent delivery to lysosomes [PMID:23761068, PMID:20130081, PMID:28768823]. GOLIM4 also regulates post-Golgi trafficking of surface proteins including Talin 1, MHC class I molecules, and multiple growth factor receptors and adhesion molecules, thereby influencing cell motility, adhesion, and proliferation [PMID:40632561, PMID:40649939]. Its expression is transcriptionally regulated by the IRE1α/XBP1s ER-stress axis, and it can be proteolytically shed by PC7/Furin to generate secreted fragments that enhance cell proliferation [PMID:40649939]."},"prefetch_data":{"uniprot":{"accession":"O00461","full_name":"Golgi integral membrane protein 4","aliases":["Golgi integral membrane protein, cis","GIMPc","Golgi phosphoprotein 4","Golgi-localized phosphoprotein of 130 kDa","Golgi phosphoprotein of 130 kDa"],"length_aa":696,"mass_kda":81.9,"function":"Plays a role in endosome to Golgi protein trafficking; mediates protein transport along the late endosome-bypass pathway from the early endosome to the Golgi","subcellular_location":"Golgi apparatus, Golgi stack membrane; Endosome membrane; Membrane","url":"https://www.uniprot.org/uniprotkb/O00461/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/GOLIM4","classification":"Not Classified","n_dependent_lines":9,"n_total_lines":1208,"dependency_fraction":0.0074503311258278145},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/GOLIM4","total_profiled":1310},"omim":[{"mim_id":"617826","title":"UNC50, INNER NUCLEAR MEMBRANE RNA-BINDING PROTEIN; UNC50","url":"https://www.omim.org/entry/617826"},{"mim_id":"606805","title":"GOLGI INTEGRAL MEMBRANE PROTEIN 4; GOLIM4","url":"https://www.omim.org/entry/606805"},{"mim_id":"604384","title":"ATPase, Ca(2+)-TRANSPORTING, TYPE 2C, MEMBER 1; ATP2C1","url":"https://www.omim.org/entry/604384"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Enhanced","locations":[{"location":"Golgi apparatus","reliability":"Enhanced"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/GOLIM4"},"hgnc":{"alias_symbol":["GPP130","GIMPC","P138"],"prev_symbol":["GOLPH4"]},"alphafold":{"accession":"O00461","domains":[],"viewer_url":"https://alphafold.ebi.ac.uk/entry/O00461","model_url":"https://alphafold.ebi.ac.uk/files/AF-O00461-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-O00461-F1-predicted_aligned_error_v6.png","plddt_mean":67.56},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=GOLIM4","jax_strain_url":"https://www.jax.org/strain/search?query=GOLIM4"},"sequence":{"accession":"O00461","fasta_url":"https://rest.uniprot.org/uniprotkb/O00461.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/O00461/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/O00461"}},"corpus_meta":[{"pmid":"9201717","id":"PMC_9201717","title":"Sequence and overexpression of GPP130/GIMPc: evidence for saturable pH-sensitive targeting of a type II early Golgi membrane protein.","date":"1997","source":"Molecular biology of the cell","url":"https://pubmed.ncbi.nlm.nih.gov/9201717","citation_count":104,"is_preprint":false},{"pmid":"20130081","id":"PMC_20130081","title":"Manganese-induced trafficking and turnover of the cis-Golgi glycoprotein GPP130.","date":"2010","source":"Molecular biology of the cell","url":"https://pubmed.ncbi.nlm.nih.gov/20130081","citation_count":64,"is_preprint":false},{"pmid":"23761068","id":"PMC_23761068","title":"Shiga toxin-binding site for host cell receptor GPP130 reveals unexpected divergence in toxin-trafficking mechanisms.","date":"2013","source":"Molecular biology of the cell","url":"https://pubmed.ncbi.nlm.nih.gov/23761068","citation_count":33,"is_preprint":false},{"pmid":"11526145","id":"PMC_11526145","title":"Antibody responses to recombinant Epstein-Barr virus antigens in nasopharyngeal carcinoma patients: complementary test of ZEBRA protein and early antigens p54 and p138.","date":"2001","source":"Journal of clinical microbiology","url":"https://pubmed.ncbi.nlm.nih.gov/11526145","citation_count":31,"is_preprint":false},{"pmid":"34180133","id":"PMC_34180133","title":"RBFOX2/GOLIM4 Splicing Axis Activates Vesicular Transport Pathway to Promote Nasopharyngeal Carcinogenesis.","date":"2021","source":"Advanced science (Weinheim, Baden-Wurttemberg, Germany)","url":"https://pubmed.ncbi.nlm.nih.gov/34180133","citation_count":25,"is_preprint":false},{"pmid":"33722196","id":"PMC_33722196","title":"MiR-105-3p acts as an oncogene to promote the proliferation and metastasis of breast cancer cells by targeting GOLIM4.","date":"2021","source":"BMC cancer","url":"https://pubmed.ncbi.nlm.nih.gov/33722196","citation_count":21,"is_preprint":false},{"pmid":"17605763","id":"PMC_17605763","title":"Both post-Golgi and intra-Golgi cycling affect the distribution of the Golgi phosphoprotein GPP130.","date":"2007","source":"Traffic (Copenhagen, Denmark)","url":"https://pubmed.ncbi.nlm.nih.gov/17605763","citation_count":17,"is_preprint":false},{"pmid":"23280773","id":"PMC_23280773","title":"Golgi phosphoprotein 4 (GPP130) is a sensitive and selective cellular target of manganese exposure.","date":"2013","source":"Synapse (New York, N.Y.)","url":"https://pubmed.ncbi.nlm.nih.gov/23280773","citation_count":15,"is_preprint":false},{"pmid":"28768823","id":"PMC_28768823","title":"Manganese-induced trafficking and turnover of GPP130 is mediated by sortilin.","date":"2017","source":"Molecular biology of the cell","url":"https://pubmed.ncbi.nlm.nih.gov/28768823","citation_count":13,"is_preprint":false},{"pmid":"8825065","id":"PMC_8825065","title":"Golgi membrane vesicles in HeLa mitotic cells are identified with monoclonal antibody made against Golgi cisternal membrane protein p138.","date":"1995","source":"Cell structure and function","url":"https://pubmed.ncbi.nlm.nih.gov/8825065","citation_count":6,"is_preprint":false},{"pmid":"40519909","id":"PMC_40519909","title":"Small extracellular vesicles from human umbilical cord mesenchymal stem cells delivering miR-202-5p alleviate renal ischemia-reperfusion injury by targeting the GOLIM4/PI3K/AKT axis.","date":"2025","source":"Frontiers in immunology","url":"https://pubmed.ncbi.nlm.nih.gov/40519909","citation_count":3,"is_preprint":false},{"pmid":"12207053","id":"PMC_12207053","title":"Expression of Golgi membrane protein p138 is cell cycle-independent and dissociated from centrosome duplication.","date":"2002","source":"Cell structure and function","url":"https://pubmed.ncbi.nlm.nih.gov/12207053","citation_count":3,"is_preprint":false},{"pmid":"36054164","id":"PMC_36054164","title":"CircRNA RNF10 inhibits tumorigenicity by targeting miR-942-5p/GOLIM4 axis in breast cancer.","date":"2022","source":"Environmental and molecular mutagenesis","url":"https://pubmed.ncbi.nlm.nih.gov/36054164","citation_count":2,"is_preprint":false},{"pmid":"40649939","id":"PMC_40649939","title":"Shedding of GPP130 by PC7 and Furin: Potential Implication in Lung Cancer Progression.","date":"2025","source":"International journal of molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/40649939","citation_count":1,"is_preprint":false},{"pmid":"40632561","id":"PMC_40632561","title":"Monensin suppresses EMT-driven cancer cell motility by inducing Golgi pH-dependent exocytosis of GOLIM4.","date":"2025","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/40632561","citation_count":0,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2024.10.22.619629","title":"IRE1-dependent GOLIM4 expression controls protein secretion to modulate glioblastoma cell adhesion and migration","date":"2024-10-25","source":"bioRxiv","url":"https://doi.org/10.1101/2024.10.22.619629","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":9548,"output_tokens":2981,"usd":0.036679},"stage2":{"model":"claude-opus-4-6","input_tokens":6311,"output_tokens":2529,"usd":0.14217},"total_usd":0.178849,"stage1_batch_id":"msgbatch_01DzrsgVgYngY1hvM3DU1yF2","stage2_batch_id":"msgbatch_01KA9b7iRzKFdhoBUT7vCvSe","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1997,\n      \"finding\": \"GPP130 (GOLIM4) is a type II integral membrane protein localized to the cis/medial Golgi with an unusually acidic lumenal domain and multiple coiled-coil regions. Overexpression causes accumulation in endocytic vesicles, and chloroquine treatment reversibly redistributes endogenous GPP130 to endocytic vesicles, demonstrating that its Golgi targeting is saturable and pH-sensitive, involving a retrieval mechanism for return to the Golgi.\",\n      \"method\": \"cDNA sequencing, overexpression, chloroquine treatment with immunofluorescence and electron microscopy, subcellular fractionation\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — foundational study with multiple orthogonal methods, >100 citations, replicated in subsequent work\",\n      \"pmids\": [\"9201717\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"GPP130 cycling is regulated at multiple stages: intra-Golgi cycling, trans-Golgi to endosome transport, and endosome-to-Golgi transport. pH perturbation (monensin) most strongly affects the trans-Golgi, the most acidic portion of the Golgi apparatus.\",\n      \"method\": \"Quantitative fluorescence microscopy with Shiga-like toxin B fragment as trafficking probe, tsO45-GFP as secretory marker, simulations of trafficking kinetics\",\n      \"journal\": \"Traffic (Copenhagen, Denmark)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — quantitative analysis with multiple probes but single lab\",\n      \"pmids\": [\"17605763\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Extracellular manganese (Mn) induces rapid redistribution of GPP130 from the cis-Golgi to multivesicular bodies via a Rab7-dependent pathway, followed by lysosomal degradation. The lumenal stem domain of GPP130 acts as a Mn sensor and is required and sufficient to confer Mn sensitivity to another cis-Golgi protein. The cytoplasmic domain is dispensable. GPP130 must be targeted to the cis-Golgi for the Mn response to occur.\",\n      \"method\": \"Immunofluorescence, domain deletion/swap experiments, Rab7 dominant-negative inhibition, live-cell imaging, pulse-chase degradation assays\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods including domain swaps and genetic inhibition, replicated across subsequent papers\",\n      \"pmids\": [\"20130081\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"GPP130 directly binds the B subunit of Shiga toxin (STx) and STx1 via a seven-residue stretch in its lumenal stem domain adjacent to the transmembrane domain. This interaction is required for retrograde endosome-to-Golgi trafficking of STx/STx1. STx2 B subunit does not bind GPP130, explaining why Mn-induced GPP130 down-regulation fails to block STx2 trafficking.\",\n      \"method\": \"Pulldown with purified toxin B subunits, mutagenesis of GPP130 stem domain and toxin residues, cell-based Shiga toxin trafficking assays\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — in vitro binding with purified proteins combined with mutagenesis and functional trafficking assay\",\n      \"pmids\": [\"23761068\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"GPP130 degradation in response to Mn is specific to Mn among transition metals tested (cobalt, copper, iron, nickel, zinc did not induce degradation) and occurs at sub-micromolar extracellular Mn concentrations without detectable increases in intracellular Mn, demonstrating exquisite selectivity of the GPP130 Mn-sensing mechanism in neuronal cells and in vivo in rat brain.\",\n      \"method\": \"Immunofluorescence quantification in AF5 cells, western blot, in vivo rat subchronic Mn exposure model\",\n      \"journal\": \"Synapse (New York, N.Y.)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — metal specificity panel with in vivo validation, single lab\",\n      \"pmids\": [\"23280773\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Mn-induced exit of GPP130 from the trans-Golgi network toward lysosomes is mediated by the sorting receptor sortilin, which interacts with the lumenal stem domain of GPP130. Mn causes GPP130 to oligomerize/aggregate in the Golgi, and sortilin sorts these complexes for lysosomal delivery. In contrast, FM-domain-induced lysosomal trafficking of galactosyltransferase was sortilin-independent.\",\n      \"method\": \"Sortilin knockdown, Co-IP/interaction assays, domain deletion experiments, self-interacting FM domain aggregation system, immunofluorescence\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal interaction mapping with domain deletions, genetic knockdown, and mechanistic comparison with control protein\",\n      \"pmids\": [\"28768823\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"RBFOX2 binds a GGAA motif in exon-7 of GOLIM4 pre-mRNA and promotes inclusion of exon-7, generating the long isoform GOLIM4-L. GOLIM4-L and RBFOX2 maintain Golgi apparatus organization and influence vesicle-mediated transport. RAB26 interacts with GOLIM4 and mediates its tumorigenic effects in NPC cells.\",\n      \"method\": \"Transcriptome splicing profiling, RBFOX2 knockdown/overexpression rescue experiments, Co-IP (GOLIM4-RAB26 interaction), luciferase splicing reporter, immunofluorescence of Golgi organization\",\n      \"journal\": \"Advanced science (Weinheim, Baden-Wurttemberg, Germany)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — Co-IP and functional rescue experiments from single lab with multiple methods\",\n      \"pmids\": [\"34180133\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"GPP130 is a substrate of proprotein convertases PC7 (PCSK7) and Furin, which cleave/shed GPP130 into a membrane-bound N-terminal product and secreted C-terminal fragments. GPP130 overexpression increases cell proliferation in A549, SKOV3, and HeLa cells, and this proliferative activity is enhanced upon cleavage by PC7 and/or Furin.\",\n      \"method\": \"Cell-based cleavage assays, overexpression and knockdown, proliferation assays, western blot for cleavage products\",\n      \"journal\": \"International journal of molecular sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — cell-based substrate cleavage assays with functional readout, single lab\",\n      \"pmids\": [\"40649939\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Monensin increases Golgi lumenal pH, inducing rapid exocytosis of GOLIM4 from the Golgi. GOLIM4 regulates cell motility and adhesion by modulating post-Golgi trafficking of Talin 1 (TLN1), an essential focal adhesion component. Both GOLIM4 and TLN1 are direct targets of microRNA-200b, which is suppressed during EMT.\",\n      \"method\": \"Monensin treatment with live-cell imaging, GOLIM4 and TLN1 knockdown, migration assays, microRNA-200b target validation, Golgi pH measurement\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple functional assays with mechanistic pathway placement, single lab\",\n      \"pmids\": [\"40632561\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"IRE1α regulates GOLIM4 expression via the XBP1s transcription factor downstream of ER stress. GOLIM4 silencing reduces surface expression of MHC class I molecules, growth factor receptors (PDGFRA, IL13RA2), and adhesion/migration proteins (CD44, CD54, NCAM1, ITGB1, CD90) without affecting their mRNA levels, demonstrating that GOLIM4 controls post-transcriptional surface trafficking of these molecules. GOLIM4 silencing impairs glioblastoma cell-cell adhesion and migration.\",\n      \"method\": \"IRE1 inhibition, XBP1s overexpression, GOLIM4 siRNA knockdown, flow cytometry for surface protein expression, qRT-PCR to exclude transcriptional effects, cell adhesion and migration assays\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods establishing pathway (IRE1/XBP1s/GOLIM4) with functional surface trafficking readout, preprint\",\n      \"pmids\": [\"bio_10.1101_2024.10.22.619629\"],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"miR-105-3p directly targets the GOLIM4 3'UTR (validated by luciferase reporter assay) and suppresses GOLIM4 expression, promoting breast cancer cell proliferation and metastasis.\",\n      \"method\": \"Luciferase reporter assay, GOLIM4 silencing rescue experiment, CCK-8, Transwell, TUNEL assays\",\n      \"journal\": \"BMC cancer\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — single lab, luciferase target validation with functional rescue but no direct mechanistic insight into GOLIM4 function\",\n      \"pmids\": [\"33722196\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"GOLIM4/GPP130 is a type II cis-Golgi membrane protein whose lumenal stem domain acts as a manganese (Mn) sensor; elevated Mn causes GPP130 oligomerization in the Golgi, which is recognized by the sorting receptor sortilin and diverts GPP130 via a Rab7-dependent pathway to lysosomes for degradation. In its normal cycling role, GPP130 serves as an endosome-to-Golgi retrograde trafficking receptor for Shiga toxin (STx/STx1) by directly binding the toxin B subunit through a seven-residue stretch in its stem domain. GOLIM4 also regulates post-Golgi trafficking of surface proteins including focal adhesion component Talin 1, and its expression is transcriptionally controlled downstream of the IRE1/XBP1s ER stress axis; it can be proteolytically shed by PC7/Furin to generate fragments that promote cell proliferation.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"GOLIM4 (GPP130) is a type II cis-Golgi membrane protein that functions as a pH-sensitive trafficking receptor cycling between the Golgi and endosomes, and as a manganese sensor that couples changes in lumenal metal ion concentration to regulated protein degradation. Its lumenal stem domain directly binds the Shiga toxin (STx/STx1) B subunit through a seven-residue stretch and is required for retrograde endosome-to-Golgi transport of the toxin; the same stem domain senses sub-micromolar manganese, triggering GPP130 oligomerization, recognition by the sorting receptor sortilin, and Rab7-dependent delivery to lysosomes [PMID:23761068, PMID:20130081, PMID:28768823]. GOLIM4 also regulates post-Golgi trafficking of surface proteins including Talin 1, MHC class I molecules, and multiple growth factor receptors and adhesion molecules, thereby influencing cell motility, adhesion, and proliferation [PMID:40632561, PMID:40649939]. Its expression is transcriptionally regulated by the IRE1α/XBP1s ER-stress axis, and it can be proteolytically shed by PC7/Furin to generate secreted fragments that enhance cell proliferation [PMID:40649939].\",\n  \"teleology\": [\n    {\n      \"year\": 1997,\n      \"claim\": \"Establishing GOLIM4 as a cis-Golgi resident with a saturable, pH-dependent retrieval mechanism resolved how an integral membrane protein cycles through endocytic compartments yet maintains steady-state Golgi localization.\",\n      \"evidence\": \"cDNA cloning, overexpression-induced endosome accumulation, chloroquine redistribution assays with immunofluorescence and EM in cultured cells\",\n      \"pmids\": [\"9201717\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"molecular determinants of the retrieval signal unknown\", \"identity of retrieval receptor or coat machinery not determined\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Quantitative dissection of GPP130 cycling kinetics revealed that its trafficking includes intra-Golgi, trans-Golgi-to-endosome, and endosome-to-Golgi steps, with pH perturbation (monensin) primarily affecting the trans-Golgi stage, clarifying where pH sensitivity operates.\",\n      \"evidence\": \"quantitative fluorescence microscopy with Shiga-like toxin B and tsO45-GFP probes, kinetic modeling\",\n      \"pmids\": [\"17605763\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"molecular basis of pH sensitivity in the lumenal domain not identified\", \"trans-Golgi sorting machinery not determined\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Identification of the GPP130 lumenal stem domain as a manganese sensor that is necessary and sufficient for Mn-induced redistribution to multivesicular bodies and lysosomal degradation via Rab7 revealed a novel mechanism linking metal ion exposure to selective Golgi protein turnover.\",\n      \"evidence\": \"domain deletion/swap chimeras, Rab7 dominant-negative, live-cell imaging, pulse-chase degradation in cultured cells\",\n      \"pmids\": [\"20130081\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"structural mechanism of Mn binding/sensing in the stem domain unknown\", \"how Rab7-dependent pathway is engaged not determined\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Demonstration that GPP130 directly binds STx/STx1 B subunit through a defined seven-residue stretch and is required for retrograde endosome-to-Golgi trafficking of these toxins established GPP130 as a bona fide cargo receptor, while explaining the selective inability of Mn-induced GPP130 depletion to block STx2.\",\n      \"evidence\": \"pulldowns with purified toxin B subunits, site-directed mutagenesis, cell-based toxin trafficking assays\",\n      \"pmids\": [\"23761068\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"crystal structure of GPP130–STx B complex not available\", \"whether additional endogenous cargoes use this binding site unknown\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"The metal specificity screen showed GPP130 degradation is exquisitely selective for Mn among transition metals and occurs at sub-micromolar concentrations in neuronal cells and in vivo in rat brain, establishing GPP130 as a physiologically relevant Mn indicator.\",\n      \"evidence\": \"metal panel (Co, Cu, Fe, Ni, Zn vs Mn) in AF5 cells, in vivo subchronic Mn exposure in rats\",\n      \"pmids\": [\"23280773\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"direct Mn binding stoichiometry and affinity not measured\", \"whether GPP130 degradation has a protective function in Mn homeostasis unclear\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Identification of sortilin as the sorting receptor that recognizes Mn-induced GPP130 oligomers in the Golgi and directs them to lysosomes resolved the missing link between Mn sensing and degradative sorting.\",\n      \"evidence\": \"sortilin knockdown, Co-IP with domain deletions, FM-domain aggregation control, immunofluorescence\",\n      \"pmids\": [\"28768823\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"structural basis for sortilin recognition of GPP130 oligomers unknown\", \"whether oligomerization is directly triggered by Mn binding or indirectly by pH change not resolved\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Discovery that RBFOX2-regulated alternative splicing of GOLIM4 exon-7 generates a long isoform (GOLIM4-L) important for Golgi integrity, and that GOLIM4 interacts with RAB26 to influence vesicle-mediated transport, expanded the functional repertoire beyond Mn sensing and toxin trafficking.\",\n      \"evidence\": \"splicing profiling, RBFOX2 knockdown/overexpression, Co-IP of GOLIM4–RAB26, luciferase splicing reporter in NPC cells\",\n      \"pmids\": [\"34180133\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"functional difference between GOLIM4-L and short isoform not fully characterized\", \"GOLIM4–RAB26 interaction not validated by reciprocal pull-down or structural methods\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Establishing that proprotein convertases PC7 and Furin cleave GPP130 to generate secreted C-terminal fragments that enhance cell proliferation revealed a non-canonical signaling output of a Golgi trafficking receptor.\",\n      \"evidence\": \"cell-based cleavage assays with PC7/Furin overexpression and knockdown, proliferation assays in A549, SKOV3, HeLa cells\",\n      \"pmids\": [\"40649939\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"identity of the receptor or pathway through which shed fragments promote proliferation unknown\", \"cleavage sites not mapped at residue level\", \"in vivo relevance not tested\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Demonstration that GOLIM4 regulates post-Golgi trafficking of Talin 1 and thereby controls cell motility and adhesion, with both genes co-regulated by miR-200b during EMT, placed GOLIM4 in an epithelial-mesenchymal transition circuit beyond its canonical Golgi cycling role.\",\n      \"evidence\": \"monensin-induced exocytosis, GOLIM4/TLN1 knockdown, migration assays, miR-200b target validation, Golgi pH measurement\",\n      \"pmids\": [\"40632561\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"mechanism by which GOLIM4 sorts TLN1 cargo not determined\", \"direct GOLIM4–TLN1 interaction not demonstrated\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Major unresolved questions include the structural basis for manganese sensing in the lumenal stem domain, whether GOLIM4 has additional endogenous retrograde trafficking cargoes beyond Shiga toxin, and the physiological significance of PC7/Furin-generated GOLIM4 fragments in vivo.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"no atomic-resolution structure of GOLIM4 lumenal domain or its Mn-bound state\", \"endogenous cargoes for the retrograde trafficking receptor function remain unidentified\", \"in vivo role of shed GOLIM4 fragments untested\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0038024\", \"supporting_discovery_ids\": [3]},\n      {\"term_id\": \"GO:0140299\", \"supporting_discovery_ids\": [2, 4]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005794\", \"supporting_discovery_ids\": [0, 1, 2]},\n      {\"term_id\": \"GO:0005768\", \"supporting_discovery_ids\": [0, 2]},\n      {\"term_id\": \"GO:0005764\", \"supporting_discovery_ids\": [2, 5]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-5653656\", \"supporting_discovery_ids\": [0, 1, 3, 6]},\n      {\"term_id\": \"R-HSA-9609507\", \"supporting_discovery_ids\": [3, 8]},\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [5, 7]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"SORT1\", \"RAB7A\", \"RAB26\", \"PCSK7\", \"FURIN\", \"RBFOX2\", \"TLN1\"],\n    \"other_free_text\": []\n  }\n}\n```"}