{"gene":"SEMG2","run_date":"2026-04-28T20:42:07","timeline":{"discoveries":[{"year":2005,"finding":"Semenogelin II (SEMG2) binds Zn²⁺ with high affinity (stoichiometry ≥10 mol/mol, average Kd ~5 µM per site) and activates PSA (prostate-specific antigen) that is inhibited by Zn²⁺, establishing SEMG2 as the major Zn²⁺ chelator in semen that regulates PSA proteolytic activity in a self-regulating system.","method":"Radioligand blotting, zinc fluorophore chelator titration, NMR analysis, chromogenic substrate PSA activity assay","journal":"The Biochemical journal","confidence":"High","confidence_rationale":"Tier 1 — multiple orthogonal in vitro biochemical methods in single rigorous study","pmids":["15563730"],"is_preprint":false},{"year":2007,"finding":"SEMG2 forms a ternary complex with PSA (prostate-specific antigen) and protein C inhibitor (PCI) in seminal plasma; Sg-II binding to PSA and PCI is modulated by pH, ionic strength, heparin, dextran sulfate, divalent cations, and particularly Zn²⁺, indicating Sg-II regulates PSA-catalyzed degradation of the semen coagulum.","method":"Biochemical characterization of complex formation, modulation by ions and pH","journal":"Seminars in thrombosis and hemostasis","confidence":"Medium","confidence_rationale":"Tier 2 — mechanistic characterization of ternary complex, single lab","pmids":["17253189"],"is_preprint":false},{"year":2008,"finding":"SEMG2 is sorted into dense-core granules (DCGs) via saturable sorting machinery at the trans-Golgi/trans-Golgi network, with N-terminal (residues 25–41) and C-terminal (residues 334–348) alpha-helical domains acting as sufficient, independent DCG-targeting sorting signals in sympathoadrenal cells.","method":"Chimeric SgII-GFP/SEAP fusion proteins, 3D deconvolution fluorescence microscopy, secretagogue-stimulated release assays, truncation analysis, Golgi-retained mutant","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — reconstitution with mutagenesis/truncation and functional secretion assays","pmids":["18299326"],"is_preprint":false},{"year":2022,"finding":"SgII undergoes pH-dependent polymerization and Ca²⁺-induced liquid-liquid phase separation (LLPS) in vitro and in vivo; Ca²⁺-induced SgII phase droplets recruit bio-lipids mimicking LDCV biogenesis, and SgII knockdown reduces LDCV size and quantal neurotransmitter release, rescued differentially by SgII truncations with varying LLPS capacity.","method":"In vitro phase separation assay, Ca²⁺-induced droplet formation, lipid recruitment reconstitution, SgII knockdown, amperometry for quantal release, LDCV size measurement","journal":"Advanced science (Weinheim, Baden-Wurttemberg, Germany)","confidence":"High","confidence_rationale":"Tier 1 — reconstitution in vitro plus loss-of-function with defined phenotypic readout and rescue","pmids":["35896896"],"is_preprint":false},{"year":1994,"finding":"Transport of SgII via the regulated secretory pathway (immature granule formation and exocytosis) requires ATP, GTP, and cytosolic proteins; it is inhibited by GTPγS, AlF₃, and BFA during granule formation but GTPγS stimulates exocytosis after granule formation. SgII is sorted ~4-fold more efficiently than glycosaminoglycan chains from the TGN, and disruption of organelle pH gradients blocks both constitutive and regulated transport. Lumenal Ca²⁺ is required for prohormone processing but not for SgII sorting into immature granules.","method":"Semi-intact PC12 cell reconstitution assay, [³⁵S]sulfate labeling, pharmacological inhibitors of vesicular transport","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 1 — cell-free reconstitution with multiple pharmacological perturbations","pmids":["7962053"],"is_preprint":false},{"year":1998,"finding":"Homotypic fusion of immature secretory granules (ISGs) containing SgII as substrate with ISGs containing the prohormone convertase PC2 was reconstituted in a cell-free assay; fusion is ISG-specific (not ISG-MSG), temperature-dependent, requires ATP, GTP, and cytosolic proteins including NSF.","method":"Cell-free ISG fusion assay, [³⁵S]sulfate-labeled SgII as substrate, PC2-mediated cleavage product quantification, NSF requirement tested","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 1 — reconstitution assay with mechanistic dissection of requirements","pmids":["9864358"],"is_preprint":false},{"year":1998,"finding":"Posttranslational processing of SgII generates the conserved 66-amino acid peptide EM66 in human adrenal chromaffin cells (both adult medulla and fetal adrenal gland), demonstrated by RIA and HPLC matching recombinant EM66.","method":"Recombinant protein generation, polyclonal antibody development, immunohistochemistry, RIA, HPLC fractionation of adrenal extracts","journal":"The Journal of clinical endocrinology and metabolism","confidence":"Medium","confidence_rationale":"Tier 2 — multiple biochemical methods confirming processing product identity, single lab","pmids":["9709974"],"is_preprint":false},{"year":2008,"finding":"SgII is a key AP-1-regulated gene: NO upregulates SgII mRNA via a CRE in the SgII promoter dependent on c-Jun; dominant-negative c-Jun (TAM67) suppresses SgII expression, impairs neuronal differentiation and sensitizes cells to NO-induced apoptosis; stable SgII re-expression in TAM67 cells restores differentiation and NO resistance; RNAi knockdown of SgII abolishes neuronal differentiation and confers NO sensitivity.","method":"Dominant-negative c-Jun expression, RNAi knockdown, stable transfection rescue, luciferase reporter with CRE mutation, apoptosis assay, neuronal differentiation assay","journal":"Cell death and differentiation","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal loss-of-function and rescue experiments establishing pathway position","pmids":["18239671"],"is_preprint":false},{"year":2011,"finding":"The SgII-derived peptide secretoneurin (SN) stimulates LH release and production in mouse LβT2 gonadotroph cells, activates ERK via PKC and MEK, increases cAMP levels, but does not activate the GnRH receptor, indicating SN signals through PKA/cAMP-ERK pathway independently of GnRH receptor.","method":"Radioimmunoassay, real-time RT-PCR, ERK phosphorylation western blot, pharmacological inhibition (PD-98059, bisindolylmaleimide), cAMP measurement","journal":"American journal of physiology. Endocrinology and metabolism","confidence":"Medium","confidence_rationale":"Tier 2 — multiple pharmacological approaches in a defined cell model, single lab","pmids":["21521715"],"is_preprint":false},{"year":2012,"finding":"SgII expression is induced in failing myocardium by TGF-β and norepinephrine; the SgII-derived fragment secretoneurin reduces myocardial ischemia-reperfusion injury and cardiomyocyte apoptosis by ~30% and rapidly increases ERK1/2 and STAT3 phosphorylation in cardiomyocytes.","method":"Post-MI mouse model, in vitro cardiomyocyte stimulation, ischemia-reperfusion injury assay, apoptosis quantification, western blot for ERK1/2 and STAT3 phosphorylation","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 — functional assay with defined signaling readout, single lab","pmids":["22655045"],"is_preprint":false},{"year":2004,"finding":"GnRH-stimulated secretion of LH is closely correlated with co-secretion of SgII (but not CgA) from LβT2 gonadotroph cells in a regulated, granin-dependent pathway; activin stimulates FSH secretion through a constitutive, granin-independent pathway.","method":"LβT2 cell culture, RIA for LH and FSH, western blot and ELISA for SgII and CgA, GnRH pulse regimes, activin treatment","journal":"Journal of molecular endocrinology","confidence":"Medium","confidence_rationale":"Tier 2 — multiple secretagogue conditions with protein-level measurements, single lab","pmids":["15072552"],"is_preprint":false},{"year":1991,"finding":"By immunoelectron microscopy, SgII localizes exclusively to the matrix of large dense-core vesicles (LDCVs) in hypothalamic neurons; SgII and synaptophysin (a small synaptic vesicle marker) are segregated from each other upon exit from the trans-Golgi network and follow distinct membrane traffic pathways.","method":"Immunoperoxidase and immunogold electron microscopy, double labeling with anti-SgII and anti-synaptophysin","journal":"The journal of histochemistry and cytochemistry","confidence":"High","confidence_rationale":"Tier 1 — immunoelectron microscopy with double labeling establishing subcellular compartmentalization","pmids":["1918927"],"is_preprint":false},{"year":1992,"finding":"SgII and prolactin are co-released in parallel from GH4C1 pituitary cells under basal and stimulated conditions (high K⁺, BAY K8644, 8-bromo-cAMP, phorbol ester, TRH); sulfation of SgII is not essential for normal packaging, processing, or regulated secretion.","method":"[³⁵S]SO₄ and ³⁵S-methionine metabolic labeling, secretagogue stimulation, chlorate inhibition of sulfation, immunoblotting","journal":"Endocrinology","confidence":"Medium","confidence_rationale":"Tier 2 — metabolic labeling with pharmacological inhibition, single lab","pmids":["1597152"],"is_preprint":false},{"year":1992,"finding":"Granulogenesis in GH4C1 cells is preceded by increased expression of SgII (and CgB), their condensation in the Golgi, and their co-aggregation with prolactin in vitro under high Ca²⁺/low pH conditions resembling the trans-Golgi environment, suggesting SgII participates in regulated secretory granule formation.","method":"Hormone treatment (estradiol, insulin, EGF), immunocytochemistry with anti-MG-160 Golgi marker, Northern blot, in vitro aggregation assay under low pH/high Ca²⁺","journal":"Endocrinology","confidence":"Medium","confidence_rationale":"Tier 2 — in vitro aggregation reconstitution plus cellular imaging, single lab","pmids":["1612012"],"is_preprint":false},{"year":2000,"finding":"The human SgII gene promoter contains a TATA box and a CRE (cyclic AMP response element) that confer neuroendocrine cell type-specific expression; SgII promoter activity correlates with CREB levels and overexpression of CREB increases SgII promoter activity up to 8-fold, establishing CREB as a key transcriptional activator of SgII.","method":"Promoter isolation, luciferase reporter transfection assays, CREB overexpression, comparison across neuroblastoma cell lines with varying SgII/CREB levels","journal":"Brain research. Molecular brain research","confidence":"Medium","confidence_rationale":"Tier 2 — reporter assays with overexpression in multiple cell lines, single lab","pmids":["10648883"],"is_preprint":false},{"year":2014,"finding":"Forced expression of SgII in LNCaP prostate cancer cells triggers formation of secretory granule-like structures competent for hormone storage and regulated release, implementing a regulated secretory pathway; androgen deprivation-induced neuroendocrine differentiation is associated with induction of SgII expression and SgII promotes cancer cell proliferation.","method":"SgII forced expression in LNCaP cells, immunocytochemistry for secretory granule markers, regulated secretion assay, proliferation assay, IHC on patient biopsies","journal":"European journal of cancer","confidence":"Medium","confidence_rationale":"Tier 2 — loss/gain of function with defined cellular phenotype, single lab","pmids":["25307750"],"is_preprint":false},{"year":2020,"finding":"SEMG2 (and SEMG1) interact with the glycolytic enzymes pyruvate kinase M2 (PKM2) and lactate dehydrogenase A (LDHA) by pull-down/LC-MS/MS, and their expression increases protein levels and enzymatic activity of both PKM2 and LDHA, as well as mitochondrial membrane potential, glycolysis, respiration, and ROS production in cancer cells.","method":"Pull-down assay followed by LC-MS/MS mass spectrometry, western blot for PKM2/LDHA, enzymatic activity assays, Seahorse metabolic assay, mitochondrial membrane potential measurement","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2 — pulldown with MS identification plus functional enzymatic and metabolic assays, single lab","pmids":["33311447"],"is_preprint":false},{"year":2002,"finding":"SEMG2 transcripts are expressed in multiple non-genital tissues beyond seminal vesicles, including vas deferens, prostate, epididymis, trachea, bronchi, kidney, and testis; immunohistochemistry shows SEMG2 protein in basal cell layers of prostate, trachea and bronchi epithelium (in contrast to luminal cells in seminal vesicle and vas deferens), and in skeletal muscle and scattered CNS cells.","method":"RT-PCR, immunohistochemistry with antibodies recognizing SgI and SgII","journal":"Molecular human reproduction","confidence":"Medium","confidence_rationale":"Tier 2 — direct localization by IHC and RT-PCR across multiple tissues, single study","pmids":["12200457"],"is_preprint":false},{"year":1996,"finding":"The two semenogelin genes (SEMG1 and SEMG2) evolved by duplication of an ~8 kb DNA segment approximately 61 million years ago, likely by recombination between L1 elements; they are separated by 11,616 bp of intergenic DNA containing >40% repetitive sequences.","method":"DNA sequencing of 15.7 kb semenogelin gene locus, comparative sequence analysis","journal":"European journal of biochemistry","confidence":"Medium","confidence_rationale":"Tier 2 — direct genomic sequencing establishing gene locus structure","pmids":["8654389"],"is_preprint":false},{"year":2024,"finding":"SgII is overexpressed in the retina in oxygen-induced retinopathy (OIR); SgII knockdown alleviates pathological retinal neovascularization but has no effect on embryonic physiological vasculature. The SgII-derived peptide secretoneurin (SN) promotes angiogenesis via activation of EGFR, IR, and IGF-1R, followed by PI3K-AKT-mTOR signaling phosphorylation.","method":"OIR mouse model, SgII knockdown, in vitro and in vivo angiogenesis assays, receptor activation assays (EGFR, IR, IGF-1R), PI3K-AKT-mTOR phosphorylation western blot","journal":"Experimental eye research","confidence":"Medium","confidence_rationale":"Tier 2 — loss-of-function in vivo with defined receptor pathway identification, single lab","pmids":["39549871"],"is_preprint":false}],"current_model":"SEMG2 encodes semenogelin II, the predominant structural protein of the semen coagulum, which chelates Zn²⁺ to regulate PSA (KLK3) proteolytic activity and its own liquefaction; in neuroendocrine/endocrine cells the orthologous secretogranin II (SgII) is sorted into dense-core granules via N- and C-terminal alpha-helical targeting domains and undergoes Ca²⁺/pH-dependent liquid-liquid phase separation to determine granule size and quantal neurotransmitter release, is transcriptionally controlled by CREB/AP-1/CRE, co-secreted with LH in a GnRH-regulated pathway, and proteolytically processed to bioactive peptides (secretoneurin, EM66) that signal through ERK/PKA/cAMP, EGFR/IR/IGF-1R–PI3K-AKT-mTOR axes, and interact with glycolytic enzymes PKM2 and LDHA to augment cellular energy metabolism."},"narrative":{"teleology":[{"year":1991,"claim":"Establishing where SgII resides within secretory neurons resolved a fundamental sorting question: SgII localizes exclusively to the matrix of large dense-core vesicles and is segregated from small synaptic vesicle markers at the trans-Golgi network.","evidence":"Immunogold and immunoperoxidase double-labeling electron microscopy in hypothalamic neurons","pmids":["1918927"],"confidence":"High","gaps":["Identity of sorting receptor or aggregation mechanism at TGN unknown","Whether SgII localization differs across neuroendocrine cell types not tested"]},{"year":1994,"claim":"Cell-free reconstitution defined the energy and cofactor requirements for SgII transport through the regulated secretory pathway, showing ATP, GTP, cytosolic proteins, and organelle pH gradients are needed for immature granule formation, while lumenal Ca²⁺ is dispensable for sorting but required for prohormone processing.","evidence":"Semi-intact PC12 cell reconstitution with pharmacological inhibitors (GTPγS, AlF₃, BFA, monensin) and [³⁵S]sulfate-labeled SgII","pmids":["7962053"],"confidence":"High","gaps":["Specific GTPase identity not determined","Whether SgII itself drives granule budding or is a passive cargo unclear"]},{"year":1996,"claim":"Genomic sequencing of the semenogelin locus established that SEMG1 and SEMG2 arose by tandem duplication ~61 Mya mediated by L1 element recombination, providing the evolutionary framework for their overlapping but distinct functions.","evidence":"Sequencing of 15.7 kb genomic locus and comparative sequence analysis","pmids":["8654389"],"confidence":"Medium","gaps":["Selective pressures driving sequence divergence between SEMG1 and SEMG2 not addressed","Functional divergence not experimentally tested"]},{"year":1998,"claim":"Two discoveries in 1998 advanced understanding of SgII processing and granule maturation: homotypic fusion of immature secretory granules containing SgII as substrate was reconstituted and shown to require NSF, and the SgII-derived bioactive peptide EM66 was identified in human adrenal chromaffin cells.","evidence":"Cell-free ISG fusion assay with PC2-mediated SgII cleavage readout; RIA/HPLC characterization of EM66 in adrenal extracts","pmids":["9864358","9709974"],"confidence":"High","gaps":["Biological function of EM66 unknown at this stage","SNARE complex composition for ISG fusion not identified"]},{"year":2000,"claim":"Identification of a functional CRE in the SgII promoter and demonstration that CREB overexpression drives up to 8-fold transcriptional activation established the core transcriptional control mechanism for neuroendocrine SgII expression.","evidence":"Luciferase reporter assays with promoter constructs and CREB overexpression across neuroblastoma lines","pmids":["10648883"],"confidence":"Medium","gaps":["Chromatin context and epigenetic regulation not explored","Whether CREB is sufficient in non-neuroendocrine cells not tested"]},{"year":2002,"claim":"Detection of SEMG2 transcripts and protein in diverse non-genital tissues including trachea, kidney, prostate basal cells, skeletal muscle, and CNS expanded the gene's functional context beyond seminal plasma.","evidence":"RT-PCR and immunohistochemistry across human tissues","pmids":["12200457"],"confidence":"Medium","gaps":["Functional role in non-reproductive tissues unknown","Whether protein in non-genital tissues is full-length or processed not determined"]},{"year":2005,"claim":"Quantitative characterization of SEMG2 as a high-affinity Zn²⁺ chelator (≥10 sites, Kd ~5 µM) that reactivates Zn²⁺-inhibited PSA established the self-regulating proteolytic system governing semen coagulum liquefaction.","evidence":"Radioligand blotting, zinc fluorophore titration, NMR, and chromogenic PSA activity assays","pmids":["15563730"],"confidence":"High","gaps":["In vivo kinetics of Zn²⁺ redistribution during liquefaction not measured","Structural basis of multi-site Zn²⁺ binding not resolved"]},{"year":2007,"claim":"Discovery that SEMG2 forms a ternary complex with PSA and protein C inhibitor modulated by Zn²⁺, pH, and glycosaminoglycans extended the regulatory model to include serpins in semen coagulum dynamics.","evidence":"Biochemical complex formation assays with ionic/pH modulation","pmids":["17253189"],"confidence":"Medium","gaps":["Stoichiometry and affinity of ternary complex not quantified","In vivo relevance of PCI regulation of PSA-SEMG2 axis not validated"]},{"year":2008,"claim":"Two 2008 studies defined sorting signals and transcriptional regulation: N-terminal (25–41) and C-terminal (334–348) α-helical domains are each sufficient for dense-core granule targeting, and AP-1/c-Jun acting through the CRE is required for SgII expression, neuronal differentiation, and NO resistance.","evidence":"Chimeric SgII-GFP truncation analysis with regulated secretion assays; dominant-negative c-Jun, RNAi, and stable rescue experiments","pmids":["18299326","18239671"],"confidence":"High","gaps":["Whether the two sorting signals act cooperatively or redundantly in vivo unresolved","Direct AP-1 ChIP on endogenous SgII promoter not performed"]},{"year":2011,"claim":"Secretoneurin was shown to stimulate LH release via a PKC–MEK–ERK and PKA/cAMP pathway independent of GnRH receptor, establishing it as an autonomous gonadotroph signaling peptide.","evidence":"RIA, ERK phosphorylation, cAMP measurement, and pharmacological inhibition in LβT2 gonadotroph cells","pmids":["21521715"],"confidence":"Medium","gaps":["Secretoneurin receptor identity unknown","Physiological relevance in vivo not demonstrated"]},{"year":2012,"claim":"Secretoneurin was found to reduce myocardial ischemia-reperfusion injury and cardiomyocyte apoptosis by ~30% through rapid ERK1/2 and STAT3 phosphorylation, extending SgII-derived peptide signaling to cardioprotection.","evidence":"Post-MI mouse model, cardiomyocyte stimulation, apoptosis quantification, phosphorylation western blots","pmids":["22655045"],"confidence":"Medium","gaps":["Receptor mediating secretoneurin cardioprotection not identified","Downstream transcriptional targets of ERK/STAT3 not characterized"]},{"year":2020,"claim":"Identification of PKM2 and LDHA as direct SEMG2-binding partners that are functionally activated by SEMG2 expression revealed an unexpected link between semenogelins and glycolytic metabolism in cancer cells.","evidence":"Pull-down/LC-MS/MS, enzymatic activity assays, Seahorse metabolic assays in cancer cells","pmids":["33311447"],"confidence":"Medium","gaps":["Binding interface not mapped","Whether interaction is direct or scaffolded not distinguished","Relevance outside cancer cell context untested"]},{"year":2022,"claim":"Demonstration that SgII undergoes Ca²⁺-induced liquid–liquid phase separation that recruits lipids and determines LDCV size and quantal release provided a biophysical mechanism for how granin aggregation drives granule biogenesis.","evidence":"In vitro LLPS reconstitution, lipid recruitment, SgII knockdown with amperometry and LDCV size measurement, rescue with LLPS-competent truncations","pmids":["35896896"],"confidence":"High","gaps":["Whether other granins cooperate with SgII in LLPS in vivo not resolved","Structural determinants of LLPS capacity beyond truncation not mapped"]},{"year":2024,"claim":"Secretoneurin was shown to promote pathological retinal neovascularization through activation of EGFR, IR, and IGF-1R followed by PI3K–AKT–mTOR signaling, identifying the first receptor-level targets for this peptide.","evidence":"OIR mouse model, SgII knockdown, receptor activation assays, PI3K–AKT–mTOR phosphorylation analysis","pmids":["39549871"],"confidence":"Medium","gaps":["Whether secretoneurin binds these receptors directly or acts via co-receptor/ligand release not determined","Applicability beyond retinal vasculature not tested"]},{"year":null,"claim":"The identity of a specific cell-surface receptor for secretoneurin remains unknown, as does the structural basis for SEMG2 multi-site Zn²⁺ binding and the physiological function of SEMG2 in non-reproductive tissues where it is expressed.","evidence":"","pmids":[],"confidence":"Low","gaps":["No dedicated secretoneurin receptor cloned or identified","No crystal or cryo-EM structure of SEMG2 or SgII available","Functional significance in trachea, kidney, and CNS unexplored"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0008289","term_label":"lipid binding","supporting_discovery_ids":[0,1]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[0,1,16]},{"term_id":"GO:0048018","term_label":"receptor ligand activity","supporting_discovery_ids":[8,9,19]}],"localization":[{"term_id":"GO:0031410","term_label":"cytoplasmic vesicle","supporting_discovery_ids":[2,3,4,5,11]},{"term_id":"GO:0005576","term_label":"extracellular region","supporting_discovery_ids":[0,1,10,12]},{"term_id":"GO:0005794","term_label":"Golgi apparatus","supporting_discovery_ids":[2,4,13]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[8,9,19]},{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[6,0,1]},{"term_id":"R-HSA-5653656","term_label":"Vesicle-mediated transport","supporting_discovery_ids":[2,3,4,5,11]},{"term_id":"R-HSA-1430728","term_label":"Metabolism","supporting_discovery_ids":[16]}],"complexes":["PSA-PCI-SEMG2 ternary complex"],"partners":["KLK3","SERPINA5","PKM","LDHA","NSF","EGFR","IGF1R"],"other_free_text":[]},"mechanistic_narrative":"SEMG2 encodes semenogelin II, the major structural protein of the semen coagulum that chelates Zn²⁺ with high affinity to regulate PSA (KLK3) proteolytic activity and semen liquefaction [PMID:15563730, PMID:17253189]. In neuroendocrine cells, the orthologous protein secretogranin II (SgII) is sorted into large dense-core vesicles via N- and C-terminal α-helical targeting domains and undergoes Ca²⁺/pH-dependent liquid–liquid phase separation that determines granule size and quantal neurotransmitter release [PMID:18299326, PMID:35896896, PMID:1918927]. SgII expression is transcriptionally controlled by CREB and AP-1/c-Jun, is required for neuronal differentiation and survival, and is proteolytically processed to bioactive peptides—secretoneurin and EM66—that activate ERK/PKA/cAMP and EGFR/IR/IGF-1R–PI3K–AKT–mTOR signaling cascades to regulate LH secretion, cardiomyocyte protection, and angiogenesis [PMID:10648883, PMID:18239671, PMID:21521715, PMID:39549871]. SEMG2 also interacts with the glycolytic enzymes PKM2 and LDHA, augmenting their activity and cellular energy metabolism in cancer cells [PMID:33311447]."},"prefetch_data":{"uniprot":{"accession":"Q02383","full_name":"Semenogelin-2","aliases":["Semenogelin II","SGII"],"length_aa":582,"mass_kda":65.4,"function":"Participates in the formation of a gel matrix (sperm coagulum) entrapping the accessory gland secretions and ejaculated spermatozoa","subcellular_location":"Secreted","url":"https://www.uniprot.org/uniprotkb/Q02383/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/SEMG2","classification":"Not Classified","n_dependent_lines":0,"n_total_lines":1208,"dependency_fraction":0.0},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"STX6","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/SEMG2","total_profiled":1310},"omim":[{"mim_id":"609872","title":"WAP 4-DISULFIDE CORE DOMAIN 12; WFDC12","url":"https://www.omim.org/entry/609872"},{"mim_id":"182141","title":"SEMENOGELIN II; SEMG2","url":"https://www.omim.org/entry/182141"},{"mim_id":"182140","title":"SEMENOGELIN I; SEMG1","url":"https://www.omim.org/entry/182140"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Tissue enriched","tissue_distribution":"Detected in some","driving_tissues":[{"tissue":"seminal vesicle","ntpm":9810.7}],"url":"https://www.proteinatlas.org/search/SEMG2"},"hgnc":{"alias_symbol":["SGII"],"prev_symbol":[]},"alphafold":{"accession":"Q02383","domains":[],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q02383","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q02383-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q02383-F1-predicted_aligned_error_v6.png","plddt_mean":30.72},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=SEMG2","jax_strain_url":"https://www.jax.org/strain/search?query=SEMG2"},"sequence":{"accession":"Q02383","fasta_url":"https://rest.uniprot.org/uniprotkb/Q02383.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q02383/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q02383"}},"corpus_meta":[{"pmid":"15531881","id":"PMC_15531881","title":"Rate of molecular evolution of the seminal protein gene SEMG2 correlates with levels of female promiscuity.","date":"2004","source":"Nature genetics","url":"https://pubmed.ncbi.nlm.nih.gov/15531881","citation_count":184,"is_preprint":false},{"pmid":"14635955","id":"PMC_14635955","title":"The differential secretion of FSH and LH: regulation through genes, feedback and packaging.","date":"2003","source":"Reproduction (Cambridge, England). 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science","url":"https://pubmed.ncbi.nlm.nih.gov/36177616","citation_count":0,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2024.10.01.616062","title":"Detecting the body’s reproductive hormonal brake against tissue overgrowth: micrin/SgII-70","date":"2024-10-03","source":"bioRxiv","url":"https://doi.org/10.1101/2024.10.01.616062","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":52670,"output_tokens":4979,"usd":0.116348},"stage2":{"model":"claude-opus-4-6","input_tokens":8583,"output_tokens":3533,"usd":0.19686},"total_usd":0.313208,"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\": 2005,\n      \"finding\": \"Semenogelin II (SEMG2) binds Zn²⁺ with high affinity (stoichiometry ≥10 mol/mol, average Kd ~5 µM per site) and activates PSA (prostate-specific antigen) that is inhibited by Zn²⁺, establishing SEMG2 as the major Zn²⁺ chelator in semen that regulates PSA proteolytic activity in a self-regulating system.\",\n      \"method\": \"Radioligand blotting, zinc fluorophore chelator titration, NMR analysis, chromogenic substrate PSA activity assay\",\n      \"journal\": \"The Biochemical journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — multiple orthogonal in vitro biochemical methods in single rigorous study\",\n      \"pmids\": [\"15563730\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"SEMG2 forms a ternary complex with PSA (prostate-specific antigen) and protein C inhibitor (PCI) in seminal plasma; Sg-II binding to PSA and PCI is modulated by pH, ionic strength, heparin, dextran sulfate, divalent cations, and particularly Zn²⁺, indicating Sg-II regulates PSA-catalyzed degradation of the semen coagulum.\",\n      \"method\": \"Biochemical characterization of complex formation, modulation by ions and pH\",\n      \"journal\": \"Seminars in thrombosis and hemostasis\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — mechanistic characterization of ternary complex, single lab\",\n      \"pmids\": [\"17253189\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"SEMG2 is sorted into dense-core granules (DCGs) via saturable sorting machinery at the trans-Golgi/trans-Golgi network, with N-terminal (residues 25–41) and C-terminal (residues 334–348) alpha-helical domains acting as sufficient, independent DCG-targeting sorting signals in sympathoadrenal cells.\",\n      \"method\": \"Chimeric SgII-GFP/SEAP fusion proteins, 3D deconvolution fluorescence microscopy, secretagogue-stimulated release assays, truncation analysis, Golgi-retained mutant\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — reconstitution with mutagenesis/truncation and functional secretion assays\",\n      \"pmids\": [\"18299326\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"SgII undergoes pH-dependent polymerization and Ca²⁺-induced liquid-liquid phase separation (LLPS) in vitro and in vivo; Ca²⁺-induced SgII phase droplets recruit bio-lipids mimicking LDCV biogenesis, and SgII knockdown reduces LDCV size and quantal neurotransmitter release, rescued differentially by SgII truncations with varying LLPS capacity.\",\n      \"method\": \"In vitro phase separation assay, Ca²⁺-induced droplet formation, lipid recruitment reconstitution, SgII knockdown, amperometry for quantal release, LDCV size measurement\",\n      \"journal\": \"Advanced science (Weinheim, Baden-Wurttemberg, Germany)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — reconstitution in vitro plus loss-of-function with defined phenotypic readout and rescue\",\n      \"pmids\": [\"35896896\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1994,\n      \"finding\": \"Transport of SgII via the regulated secretory pathway (immature granule formation and exocytosis) requires ATP, GTP, and cytosolic proteins; it is inhibited by GTPγS, AlF₃, and BFA during granule formation but GTPγS stimulates exocytosis after granule formation. SgII is sorted ~4-fold more efficiently than glycosaminoglycan chains from the TGN, and disruption of organelle pH gradients blocks both constitutive and regulated transport. Lumenal Ca²⁺ is required for prohormone processing but not for SgII sorting into immature granules.\",\n      \"method\": \"Semi-intact PC12 cell reconstitution assay, [³⁵S]sulfate labeling, pharmacological inhibitors of vesicular transport\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — cell-free reconstitution with multiple pharmacological perturbations\",\n      \"pmids\": [\"7962053\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"Homotypic fusion of immature secretory granules (ISGs) containing SgII as substrate with ISGs containing the prohormone convertase PC2 was reconstituted in a cell-free assay; fusion is ISG-specific (not ISG-MSG), temperature-dependent, requires ATP, GTP, and cytosolic proteins including NSF.\",\n      \"method\": \"Cell-free ISG fusion assay, [³⁵S]sulfate-labeled SgII as substrate, PC2-mediated cleavage product quantification, NSF requirement tested\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — reconstitution assay with mechanistic dissection of requirements\",\n      \"pmids\": [\"9864358\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"Posttranslational processing of SgII generates the conserved 66-amino acid peptide EM66 in human adrenal chromaffin cells (both adult medulla and fetal adrenal gland), demonstrated by RIA and HPLC matching recombinant EM66.\",\n      \"method\": \"Recombinant protein generation, polyclonal antibody development, immunohistochemistry, RIA, HPLC fractionation of adrenal extracts\",\n      \"journal\": \"The Journal of clinical endocrinology and metabolism\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple biochemical methods confirming processing product identity, single lab\",\n      \"pmids\": [\"9709974\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"SgII is a key AP-1-regulated gene: NO upregulates SgII mRNA via a CRE in the SgII promoter dependent on c-Jun; dominant-negative c-Jun (TAM67) suppresses SgII expression, impairs neuronal differentiation and sensitizes cells to NO-induced apoptosis; stable SgII re-expression in TAM67 cells restores differentiation and NO resistance; RNAi knockdown of SgII abolishes neuronal differentiation and confers NO sensitivity.\",\n      \"method\": \"Dominant-negative c-Jun expression, RNAi knockdown, stable transfection rescue, luciferase reporter with CRE mutation, apoptosis assay, neuronal differentiation assay\",\n      \"journal\": \"Cell death and differentiation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal loss-of-function and rescue experiments establishing pathway position\",\n      \"pmids\": [\"18239671\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"The SgII-derived peptide secretoneurin (SN) stimulates LH release and production in mouse LβT2 gonadotroph cells, activates ERK via PKC and MEK, increases cAMP levels, but does not activate the GnRH receptor, indicating SN signals through PKA/cAMP-ERK pathway independently of GnRH receptor.\",\n      \"method\": \"Radioimmunoassay, real-time RT-PCR, ERK phosphorylation western blot, pharmacological inhibition (PD-98059, bisindolylmaleimide), cAMP measurement\",\n      \"journal\": \"American journal of physiology. Endocrinology and metabolism\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple pharmacological approaches in a defined cell model, single lab\",\n      \"pmids\": [\"21521715\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"SgII expression is induced in failing myocardium by TGF-β and norepinephrine; the SgII-derived fragment secretoneurin reduces myocardial ischemia-reperfusion injury and cardiomyocyte apoptosis by ~30% and rapidly increases ERK1/2 and STAT3 phosphorylation in cardiomyocytes.\",\n      \"method\": \"Post-MI mouse model, in vitro cardiomyocyte stimulation, ischemia-reperfusion injury assay, apoptosis quantification, western blot for ERK1/2 and STAT3 phosphorylation\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — functional assay with defined signaling readout, single lab\",\n      \"pmids\": [\"22655045\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"GnRH-stimulated secretion of LH is closely correlated with co-secretion of SgII (but not CgA) from LβT2 gonadotroph cells in a regulated, granin-dependent pathway; activin stimulates FSH secretion through a constitutive, granin-independent pathway.\",\n      \"method\": \"LβT2 cell culture, RIA for LH and FSH, western blot and ELISA for SgII and CgA, GnRH pulse regimes, activin treatment\",\n      \"journal\": \"Journal of molecular endocrinology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple secretagogue conditions with protein-level measurements, single lab\",\n      \"pmids\": [\"15072552\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1991,\n      \"finding\": \"By immunoelectron microscopy, SgII localizes exclusively to the matrix of large dense-core vesicles (LDCVs) in hypothalamic neurons; SgII and synaptophysin (a small synaptic vesicle marker) are segregated from each other upon exit from the trans-Golgi network and follow distinct membrane traffic pathways.\",\n      \"method\": \"Immunoperoxidase and immunogold electron microscopy, double labeling with anti-SgII and anti-synaptophysin\",\n      \"journal\": \"The journal of histochemistry and cytochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — immunoelectron microscopy with double labeling establishing subcellular compartmentalization\",\n      \"pmids\": [\"1918927\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1992,\n      \"finding\": \"SgII and prolactin are co-released in parallel from GH4C1 pituitary cells under basal and stimulated conditions (high K⁺, BAY K8644, 8-bromo-cAMP, phorbol ester, TRH); sulfation of SgII is not essential for normal packaging, processing, or regulated secretion.\",\n      \"method\": \"[³⁵S]SO₄ and ³⁵S-methionine metabolic labeling, secretagogue stimulation, chlorate inhibition of sulfation, immunoblotting\",\n      \"journal\": \"Endocrinology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — metabolic labeling with pharmacological inhibition, single lab\",\n      \"pmids\": [\"1597152\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1992,\n      \"finding\": \"Granulogenesis in GH4C1 cells is preceded by increased expression of SgII (and CgB), their condensation in the Golgi, and their co-aggregation with prolactin in vitro under high Ca²⁺/low pH conditions resembling the trans-Golgi environment, suggesting SgII participates in regulated secretory granule formation.\",\n      \"method\": \"Hormone treatment (estradiol, insulin, EGF), immunocytochemistry with anti-MG-160 Golgi marker, Northern blot, in vitro aggregation assay under low pH/high Ca²⁺\",\n      \"journal\": \"Endocrinology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — in vitro aggregation reconstitution plus cellular imaging, single lab\",\n      \"pmids\": [\"1612012\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"The human SgII gene promoter contains a TATA box and a CRE (cyclic AMP response element) that confer neuroendocrine cell type-specific expression; SgII promoter activity correlates with CREB levels and overexpression of CREB increases SgII promoter activity up to 8-fold, establishing CREB as a key transcriptional activator of SgII.\",\n      \"method\": \"Promoter isolation, luciferase reporter transfection assays, CREB overexpression, comparison across neuroblastoma cell lines with varying SgII/CREB levels\",\n      \"journal\": \"Brain research. Molecular brain research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — reporter assays with overexpression in multiple cell lines, single lab\",\n      \"pmids\": [\"10648883\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Forced expression of SgII in LNCaP prostate cancer cells triggers formation of secretory granule-like structures competent for hormone storage and regulated release, implementing a regulated secretory pathway; androgen deprivation-induced neuroendocrine differentiation is associated with induction of SgII expression and SgII promotes cancer cell proliferation.\",\n      \"method\": \"SgII forced expression in LNCaP cells, immunocytochemistry for secretory granule markers, regulated secretion assay, proliferation assay, IHC on patient biopsies\",\n      \"journal\": \"European journal of cancer\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — loss/gain of function with defined cellular phenotype, single lab\",\n      \"pmids\": [\"25307750\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"SEMG2 (and SEMG1) interact with the glycolytic enzymes pyruvate kinase M2 (PKM2) and lactate dehydrogenase A (LDHA) by pull-down/LC-MS/MS, and their expression increases protein levels and enzymatic activity of both PKM2 and LDHA, as well as mitochondrial membrane potential, glycolysis, respiration, and ROS production in cancer cells.\",\n      \"method\": \"Pull-down assay followed by LC-MS/MS mass spectrometry, western blot for PKM2/LDHA, enzymatic activity assays, Seahorse metabolic assay, mitochondrial membrane potential measurement\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — pulldown with MS identification plus functional enzymatic and metabolic assays, single lab\",\n      \"pmids\": [\"33311447\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"SEMG2 transcripts are expressed in multiple non-genital tissues beyond seminal vesicles, including vas deferens, prostate, epididymis, trachea, bronchi, kidney, and testis; immunohistochemistry shows SEMG2 protein in basal cell layers of prostate, trachea and bronchi epithelium (in contrast to luminal cells in seminal vesicle and vas deferens), and in skeletal muscle and scattered CNS cells.\",\n      \"method\": \"RT-PCR, immunohistochemistry with antibodies recognizing SgI and SgII\",\n      \"journal\": \"Molecular human reproduction\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct localization by IHC and RT-PCR across multiple tissues, single study\",\n      \"pmids\": [\"12200457\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"The two semenogelin genes (SEMG1 and SEMG2) evolved by duplication of an ~8 kb DNA segment approximately 61 million years ago, likely by recombination between L1 elements; they are separated by 11,616 bp of intergenic DNA containing >40% repetitive sequences.\",\n      \"method\": \"DNA sequencing of 15.7 kb semenogelin gene locus, comparative sequence analysis\",\n      \"journal\": \"European journal of biochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct genomic sequencing establishing gene locus structure\",\n      \"pmids\": [\"8654389\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"SgII is overexpressed in the retina in oxygen-induced retinopathy (OIR); SgII knockdown alleviates pathological retinal neovascularization but has no effect on embryonic physiological vasculature. The SgII-derived peptide secretoneurin (SN) promotes angiogenesis via activation of EGFR, IR, and IGF-1R, followed by PI3K-AKT-mTOR signaling phosphorylation.\",\n      \"method\": \"OIR mouse model, SgII knockdown, in vitro and in vivo angiogenesis assays, receptor activation assays (EGFR, IR, IGF-1R), PI3K-AKT-mTOR phosphorylation western blot\",\n      \"journal\": \"Experimental eye research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — loss-of-function in vivo with defined receptor pathway identification, single lab\",\n      \"pmids\": [\"39549871\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"SEMG2 encodes semenogelin II, the predominant structural protein of the semen coagulum, which chelates Zn²⁺ to regulate PSA (KLK3) proteolytic activity and its own liquefaction; in neuroendocrine/endocrine cells the orthologous secretogranin II (SgII) is sorted into dense-core granules via N- and C-terminal alpha-helical targeting domains and undergoes Ca²⁺/pH-dependent liquid-liquid phase separation to determine granule size and quantal neurotransmitter release, is transcriptionally controlled by CREB/AP-1/CRE, co-secreted with LH in a GnRH-regulated pathway, and proteolytically processed to bioactive peptides (secretoneurin, EM66) that signal through ERK/PKA/cAMP, EGFR/IR/IGF-1R–PI3K-AKT-mTOR axes, and interact with glycolytic enzymes PKM2 and LDHA to augment cellular energy metabolism.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"SEMG2 encodes semenogelin II, the major structural protein of the semen coagulum that chelates Zn²⁺ with high affinity to regulate PSA (KLK3) proteolytic activity and semen liquefaction [PMID:15563730, PMID:17253189]. In neuroendocrine cells, the orthologous protein secretogranin II (SgII) is sorted into large dense-core vesicles via N- and C-terminal α-helical targeting domains and undergoes Ca²⁺/pH-dependent liquid–liquid phase separation that determines granule size and quantal neurotransmitter release [PMID:18299326, PMID:35896896, PMID:1918927]. SgII expression is transcriptionally controlled by CREB and AP-1/c-Jun, is required for neuronal differentiation and survival, and is proteolytically processed to bioactive peptides—secretoneurin and EM66—that activate ERK/PKA/cAMP and EGFR/IR/IGF-1R–PI3K–AKT–mTOR signaling cascades to regulate LH secretion, cardiomyocyte protection, and angiogenesis [PMID:10648883, PMID:18239671, PMID:21521715, PMID:39549871]. SEMG2 also interacts with the glycolytic enzymes PKM2 and LDHA, augmenting their activity and cellular energy metabolism in cancer cells [PMID:33311447].\",\n  \"teleology\": [\n    {\n      \"year\": 1991,\n      \"claim\": \"Establishing where SgII resides within secretory neurons resolved a fundamental sorting question: SgII localizes exclusively to the matrix of large dense-core vesicles and is segregated from small synaptic vesicle markers at the trans-Golgi network.\",\n      \"evidence\": \"Immunogold and immunoperoxidase double-labeling electron microscopy in hypothalamic neurons\",\n      \"pmids\": [\"1918927\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Identity of sorting receptor or aggregation mechanism at TGN unknown\", \"Whether SgII localization differs across neuroendocrine cell types not tested\"]\n    },\n    {\n      \"year\": 1994,\n      \"claim\": \"Cell-free reconstitution defined the energy and cofactor requirements for SgII transport through the regulated secretory pathway, showing ATP, GTP, cytosolic proteins, and organelle pH gradients are needed for immature granule formation, while lumenal Ca²⁺ is dispensable for sorting but required for prohormone processing.\",\n      \"evidence\": \"Semi-intact PC12 cell reconstitution with pharmacological inhibitors (GTPγS, AlF₃, BFA, monensin) and [³⁵S]sulfate-labeled SgII\",\n      \"pmids\": [\"7962053\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Specific GTPase identity not determined\", \"Whether SgII itself drives granule budding or is a passive cargo unclear\"]\n    },\n    {\n      \"year\": 1996,\n      \"claim\": \"Genomic sequencing of the semenogelin locus established that SEMG1 and SEMG2 arose by tandem duplication ~61 Mya mediated by L1 element recombination, providing the evolutionary framework for their overlapping but distinct functions.\",\n      \"evidence\": \"Sequencing of 15.7 kb genomic locus and comparative sequence analysis\",\n      \"pmids\": [\"8654389\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Selective pressures driving sequence divergence between SEMG1 and SEMG2 not addressed\", \"Functional divergence not experimentally tested\"]\n    },\n    {\n      \"year\": 1998,\n      \"claim\": \"Two discoveries in 1998 advanced understanding of SgII processing and granule maturation: homotypic fusion of immature secretory granules containing SgII as substrate was reconstituted and shown to require NSF, and the SgII-derived bioactive peptide EM66 was identified in human adrenal chromaffin cells.\",\n      \"evidence\": \"Cell-free ISG fusion assay with PC2-mediated SgII cleavage readout; RIA/HPLC characterization of EM66 in adrenal extracts\",\n      \"pmids\": [\"9864358\", \"9709974\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Biological function of EM66 unknown at this stage\", \"SNARE complex composition for ISG fusion not identified\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"Identification of a functional CRE in the SgII promoter and demonstration that CREB overexpression drives up to 8-fold transcriptional activation established the core transcriptional control mechanism for neuroendocrine SgII expression.\",\n      \"evidence\": \"Luciferase reporter assays with promoter constructs and CREB overexpression across neuroblastoma lines\",\n      \"pmids\": [\"10648883\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Chromatin context and epigenetic regulation not explored\", \"Whether CREB is sufficient in non-neuroendocrine cells not tested\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Detection of SEMG2 transcripts and protein in diverse non-genital tissues including trachea, kidney, prostate basal cells, skeletal muscle, and CNS expanded the gene's functional context beyond seminal plasma.\",\n      \"evidence\": \"RT-PCR and immunohistochemistry across human tissues\",\n      \"pmids\": [\"12200457\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional role in non-reproductive tissues unknown\", \"Whether protein in non-genital tissues is full-length or processed not determined\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Quantitative characterization of SEMG2 as a high-affinity Zn²⁺ chelator (≥10 sites, Kd ~5 µM) that reactivates Zn²⁺-inhibited PSA established the self-regulating proteolytic system governing semen coagulum liquefaction.\",\n      \"evidence\": \"Radioligand blotting, zinc fluorophore titration, NMR, and chromogenic PSA activity assays\",\n      \"pmids\": [\"15563730\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vivo kinetics of Zn²⁺ redistribution during liquefaction not measured\", \"Structural basis of multi-site Zn²⁺ binding not resolved\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Discovery that SEMG2 forms a ternary complex with PSA and protein C inhibitor modulated by Zn²⁺, pH, and glycosaminoglycans extended the regulatory model to include serpins in semen coagulum dynamics.\",\n      \"evidence\": \"Biochemical complex formation assays with ionic/pH modulation\",\n      \"pmids\": [\"17253189\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Stoichiometry and affinity of ternary complex not quantified\", \"In vivo relevance of PCI regulation of PSA-SEMG2 axis not validated\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Two 2008 studies defined sorting signals and transcriptional regulation: N-terminal (25–41) and C-terminal (334–348) α-helical domains are each sufficient for dense-core granule targeting, and AP-1/c-Jun acting through the CRE is required for SgII expression, neuronal differentiation, and NO resistance.\",\n      \"evidence\": \"Chimeric SgII-GFP truncation analysis with regulated secretion assays; dominant-negative c-Jun, RNAi, and stable rescue experiments\",\n      \"pmids\": [\"18299326\", \"18239671\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether the two sorting signals act cooperatively or redundantly in vivo unresolved\", \"Direct AP-1 ChIP on endogenous SgII promoter not performed\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Secretoneurin was shown to stimulate LH release via a PKC–MEK–ERK and PKA/cAMP pathway independent of GnRH receptor, establishing it as an autonomous gonadotroph signaling peptide.\",\n      \"evidence\": \"RIA, ERK phosphorylation, cAMP measurement, and pharmacological inhibition in LβT2 gonadotroph cells\",\n      \"pmids\": [\"21521715\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Secretoneurin receptor identity unknown\", \"Physiological relevance in vivo not demonstrated\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Secretoneurin was found to reduce myocardial ischemia-reperfusion injury and cardiomyocyte apoptosis by ~30% through rapid ERK1/2 and STAT3 phosphorylation, extending SgII-derived peptide signaling to cardioprotection.\",\n      \"evidence\": \"Post-MI mouse model, cardiomyocyte stimulation, apoptosis quantification, phosphorylation western blots\",\n      \"pmids\": [\"22655045\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Receptor mediating secretoneurin cardioprotection not identified\", \"Downstream transcriptional targets of ERK/STAT3 not characterized\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Identification of PKM2 and LDHA as direct SEMG2-binding partners that are functionally activated by SEMG2 expression revealed an unexpected link between semenogelins and glycolytic metabolism in cancer cells.\",\n      \"evidence\": \"Pull-down/LC-MS/MS, enzymatic activity assays, Seahorse metabolic assays in cancer cells\",\n      \"pmids\": [\"33311447\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Binding interface not mapped\", \"Whether interaction is direct or scaffolded not distinguished\", \"Relevance outside cancer cell context untested\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Demonstration that SgII undergoes Ca²⁺-induced liquid–liquid phase separation that recruits lipids and determines LDCV size and quantal release provided a biophysical mechanism for how granin aggregation drives granule biogenesis.\",\n      \"evidence\": \"In vitro LLPS reconstitution, lipid recruitment, SgII knockdown with amperometry and LDCV size measurement, rescue with LLPS-competent truncations\",\n      \"pmids\": [\"35896896\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether other granins cooperate with SgII in LLPS in vivo not resolved\", \"Structural determinants of LLPS capacity beyond truncation not mapped\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Secretoneurin was shown to promote pathological retinal neovascularization through activation of EGFR, IR, and IGF-1R followed by PI3K–AKT–mTOR signaling, identifying the first receptor-level targets for this peptide.\",\n      \"evidence\": \"OIR mouse model, SgII knockdown, receptor activation assays, PI3K–AKT–mTOR phosphorylation analysis\",\n      \"pmids\": [\"39549871\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether secretoneurin binds these receptors directly or acts via co-receptor/ligand release not determined\", \"Applicability beyond retinal vasculature not tested\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The identity of a specific cell-surface receptor for secretoneurin remains unknown, as does the structural basis for SEMG2 multi-site Zn²⁺ binding and the physiological function of SEMG2 in non-reproductive tissues where it is expressed.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No dedicated secretoneurin receptor cloned or identified\", \"No crystal or cryo-EM structure of SEMG2 or SgII available\", \"Functional significance in trachea, kidney, and CNS unexplored\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0008289\", \"supporting_discovery_ids\": [0, 1]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [0, 1, 16]},\n      {\"term_id\": \"GO:0048018\", \"supporting_discovery_ids\": [8, 9, 19]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0031410\", \"supporting_discovery_ids\": [2, 3, 4, 5, 11]},\n      {\"term_id\": \"GO:0005576\", \"supporting_discovery_ids\": [0, 1, 10, 12]},\n      {\"term_id\": \"GO:0005794\", \"supporting_discovery_ids\": [2, 4, 13]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"GO:0005576\", \"supporting_discovery_ids\": []},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [8, 9, 19]},\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [6, 0, 1]},\n      {\"term_id\": \"R-HSA-5653656\", \"supporting_discovery_ids\": [2, 3, 4, 5, 11]},\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [16]}\n    ],\n    \"complexes\": [\n      \"PSA-PCI-SEMG2 ternary complex\"\n    ],\n    \"partners\": [\n      \"KLK3\",\n      \"SERPINA5\",\n      \"PKM\",\n      \"LDHA\",\n      \"NSF\",\n      \"EGFR\",\n      \"IGF1R\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}