{"gene":"GRN","run_date":"2026-06-10T01:55:21","timeline":{"discoveries":[{"year":2001,"finding":"PCDGF/progranulin mediates the mitogenic effect of estrogen (17β-estradiol) in MCF-7 breast cancer cells via stimulation of cyclin D1 expression and MAP kinase activation; anti-PCDGF neutralizing antibody and antisense inhibition of PCDGF both blocked E2-dependent proliferation, while PCDGF overexpression conferred estrogen-independent growth and tamoxifen resistance.","method":"Neutralizing antibody, antisense transfection, PCDGF overexpression, MAP kinase assay, cyclin D1 immunoblot, DNA synthesis assay","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (antibody, antisense, overexpression) in a single focused study with direct functional readouts","pmids":["11134521"],"is_preprint":false},{"year":1998,"finding":"PCDGF/progranulin expression is required for tumorigenicity of PC teratoma cells; antisense-mediated inhibition of PCDGF expression dramatically reduced tumor formation in syngeneic mice, demonstrating that autocrine PCDGF production drives tumorigenesis.","method":"Antisense PCDGF cDNA transfection, in vivo tumor formation assay in syngeneic mice, Northern/Western blot","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean loss-of-function with defined in vivo phenotype, replicated in breast carcinoma model (PMID:10760271)","pmids":["9826678","10760271"],"is_preprint":false},{"year":1998,"finding":"PCDGF/progranulin binds to two classes of cell-surface receptors on mink lung epithelial cells (CCL64): high-affinity sites (Kd ~43 pM, ~560 sites/cell) and low-affinity sites (Kd ~3.9 nM, ~16,350 sites/cell); chemical crosslinking identified a ~120 kDa receptor species; similar binding sites were detected on 3T3 fibroblasts and PC cells.","method":"Radiolabeled ligand binding (125I-PCDGF), Scatchard analysis, chemical crosslinking with disuccinimidyl suberate, SDS-PAGE","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct binding assay with Scatchard analysis and crosslinking, single lab, receptor identity not further confirmed","pmids":["9571191"],"is_preprint":false},{"year":2004,"finding":"Progranulin/PCDGF overexpression in MCF-7 breast cancer cells stimulates anchorage-independent growth, cell migration through Matrigel, upregulation of matrix metalloprotease-9 (by gelatin zymography and immunoblot), and VEGF expression, implicating progranulin in invasion and angiogenesis.","method":"Stable overexpression, exogenous protein treatment, gelatin zymography, immunoblot for MMP-9 and VEGF, transwell migration assay","journal":"Carcinogenesis","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — overexpression and exogenous treatment with multiple functional readouts, single lab","pmids":["15117809"],"is_preprint":false},{"year":2007,"finding":"Antisense-mediated inhibition of PCDGF/progranulin in ovarian cancer cells (SW626, A2780) reduced proliferation and invasion, and decreased cyclin D1 and CDK4 expression while inactivating MMP-2, placing progranulin upstream of cell cycle entry and extracellular matrix remodeling.","method":"Antisense PCDGF cDNA transfection, MTT proliferation assay, Boyden chamber invasion assay, RT-PCR and Western blot for cyclin D1/CDK4, gelatin zymography for MMP-2","journal":"BMC cancer","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — loss-of-function with multiple molecular readouts, single lab","pmids":["17261172"],"is_preprint":false},{"year":2010,"finding":"TMEM106B SNPs are significantly associated with plasma progranulin (GRN) levels in controls, and TMEM106B and GRN mRNA expression are inversely correlated in peripheral blood, indicating TMEM106B modulates progranulin levels post-transcriptionally.","method":"Genetic association study with plasma PGRN ELISA, correlation of TMEM106B and GRN mRNA expression in blood samples","journal":"Neurology","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — observational correlation in large cohort (n>1000 for plasma), replicated in two sample sets, no direct mechanistic experiment","pmids":["21178100"],"is_preprint":false},{"year":2021,"finding":"Progranulin (PGRN) is a pH-dependent interactor of bis(monoacylglycero)phosphate (BMP), an endolysosomal phospholipid; PGRN deficiency causes global BMP deficiency and impairs lysosomal proteolysis, lipolysis, and redox homeostasis. Secondary glucosylsphingosine storage occurs in aged Grn-/- brains. A brain-penetrant PTV:PGRN biologic rescued BMP levels, glucosylsphingosine accumulation, oxidative stress, lysosomal dysfunction, microgliosis, and lipofuscinosis in Grn-/- mice and human iPSC-derived microglia.","method":"Grn-/- mouse model, lipidomic profiling of BMP, pH-dependent binding assays, iPSC-derived microglia, protein replacement therapy, mass spectrometry, lysosomal functional assays","journal":"Cell","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — multiple orthogonal methods (lipidomics, binding assay, functional rescue in vivo and in vitro), rigorous controls, high-impact venue","pmids":["34450028"],"is_preprint":false},{"year":2022,"finding":"PGRN deficiency causes gangliosidosis: PGRN-deficient human cells, murine brains, and human FTD-GRN frontal lobes accumulate gangliosides. Lysosomal enzymes that catabolize gangliosides are present at normal levels, but BMP levels are reduced, implicating PGRN-derived granulins in maintaining BMP levels required for ganglioside catabolism.","method":"PGRN-deficient human cells and Grn-/- mouse brains, human FTD-GRN tissue, ganglioside mass spectrometry, lysosomal enzyme activity assays, BMP lipid profiling","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — multiple orthogonal methods (lipidomics, enzyme assays, human and mouse tissue), mechanistically consistent with PMID:34450028","pmids":["36207292"],"is_preprint":false},{"year":2021,"finding":"In Grn knockout mice, microglia accumulate myelin debris in lysosomes in white matter regions. PGRN insufficiency in microglia leads to impaired lysosomal-mediated clearance of myelin debris. Grn KO mice deficient in cathepsin D have augmented myelin debris and increased neuronal TDP-43 pathology, placing PGRN upstream of cathepsin D-dependent lysosomal clearance of myelin.","method":"Grn-/- mouse model, electron microscopy, immunofluorescence, Ctsd/Grn double-KO genetic epistasis, human FTD-GRN tissue immunostaining","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic epistasis (double KO), multiple orthogonal methods, human tissue validation","pmids":["34433069"],"is_preprint":false},{"year":2020,"finding":"Simultaneous loss of both PGRN and TMEM106B in mice results in severe neuronal loss, glial activation, enlarged lysosomes in microglia and astrocytes, and enhanced accumulation of lysosomal vacuoles at the axon initial segment of motor neurons, with much earlier onset than single knockouts, demonstrating genetic interaction between TMEM106B and PGRN in lysosomal function and neurodegeneration.","method":"Pgrn/Tmem106b double-knockout mouse model, neuropathology, immunohistochemistry, electron microscopy","journal":"EMBO reports","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic epistasis (double KO vs single KOs), clear phenotypic hierarchy established","pmids":["32852886"],"is_preprint":false},{"year":2018,"finding":"In a PGRN-R504X knock-in mouse model, PGRN reduction leads to disinhibition of Gas6 binding to Tyro3, activating PKCα via PLCγ, which phosphorylates tau at Ser203, causing tau mislocalization to dendritic spines and spine loss. PKC inhibitor, B-Raf inhibitor, or knockdown of Gas6-Tyro3-tau pathway members rescued spine loss and cognitive impairment.","method":"Phosphoproteomic analysis, PGRN-R504X knock-in mice, PKCα kinase assay, pharmacological inhibition (PKC inhibitor, B-Raf inhibitor), siRNA knockdown, dendritic spine imaging, behavioral testing","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — phosphoproteomics, kinase identification, genetic and pharmacological rescue, multiple orthogonal methods","pmids":["29382817"],"is_preprint":false},{"year":2023,"finding":"Progranulin-deficient astrocytes drive synaptic degeneration in the thalamocortical circuit: single-cell transcriptomics in Grn-/- mice and FTD-GRN patients revealed conserved upregulation of GJA1, AQP4, and APOE and downregulation of glutamate transporter SLC1A2. Progranulin-deficient astrocytes in cocultures and cortical organoid transplant experiments directly induced synaptic degeneration, neuronal stress, and TDP-43 proteinopathy.","method":"Single-nucleus RNA-seq, Grn-/- mice, FTD-GRN human tissue, iPSC-derived astrocyte transplantation into cortical organoids, astrocyte-neuron cocultures, immunostaining for TDP-43 and synaptic markers","journal":"The Journal of clinical investigation","confidence":"High","confidence_rationale":"Tier 2 / Strong — functional coculture and organoid transplantation experiments, human-mouse conservation, multiple orthogonal methods","pmids":["36602862"],"is_preprint":false},{"year":2019,"finding":"Influenza virus-induced progranulin (PGRN) negatively regulates type I interferon production by inhibiting NF-κB and IRF3 signaling. Mechanistically, PGRN directly interacts with NF-κB essential modulator (NEMO) via its Grn CDE domains and recruits A20 to deubiquitinate K63-linked polyubiquitin chains on NEMO at K264.","method":"PGRN knockdown, PGRN-deficient mice, co-immunoprecipitation of PGRN with NEMO, domain mapping (Grn CDE), deubiquitination assay showing A20 recruitment, PGRN neutralizing antibody in vivo, type I IFN quantification","journal":"PLoS pathogens","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP, domain mapping, deubiquitination mechanism identified, in vivo validation","pmids":["31585000"],"is_preprint":false},{"year":2014,"finding":"Progranulin exerts anti-inflammatory protection in colitis in an IL-10- and TNFR2-dependent manner: PGRN-deficient mice show heightened susceptibility to colitis, and recombinant PGRN is protective. The protective effect was largely absent in IL-10-deficient and TNFR2-deficient colitis models, placing PGRN's action downstream of or in the same pathway as both IL-10 and TNFR2.","method":"PGRN-/-, IL-10-/-, and TNFR2-/- mice, DSS and TNBS colitis models, bone marrow chimera, CD4+ T cell transfer, recombinant PGRN treatment, histological scoring","journal":"Scientific reports","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple genetic knockout models, epistasis (triple pathway testing), in vivo rescue","pmids":["25387791"],"is_preprint":false},{"year":2024,"finding":"PGRN directly binds TNFR2 (confirmed by co-immunoprecipitation), co-localizes with TNFR2 on M2 macrophages, and promotes macrophage M2 polarization through TNFR2; TNFR2-blocking antibody inhibits PGRN-mediated M2 polarization.","method":"Co-immunoprecipitation, multiplex immunohistochemistry, TNFR2 neutralizing antibody, flow cytometry, ELISA for M1/M2 markers","journal":"Journal of translational medicine","confidence":"Medium","confidence_rationale":"Tier 2-3 / Moderate — Co-IP plus functional neutralizing antibody, single lab","pmids":["38689292"],"is_preprint":false},{"year":2015,"finding":"PGRN impairs hepatic insulin sensitivity via TNFR1/NF-κB signaling: in vivo PGRN treatment impairs glucose and insulin tolerance with hepatic autophagy imbalance; TNFR1 blocking peptide-Fc restores insulin sensitivity and autophagy. In hepatocytes, PGRN-induced insulin resistance and autophagy defects are nullified by TNFR1 siRNA via TNFR1-NF-κB-dependent manner.","method":"PGRN treatment of mice for 21 days, TNFR1 blocking peptide-Fc, TNFR1 siRNA in hepatocytes, glucose/insulin tolerance tests, autophagy markers (LC3, p62), insulin signaling (Akt phosphorylation)","journal":"Molecular endocrinology (Baltimore, Md.)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo and in vitro pharmacological and genetic intervention, single lab","pmids":["25664864"],"is_preprint":false},{"year":2015,"finding":"PGRN triggers ER stress and impairs insulin sensitivity via the PERK-eIF2α axis: PGRN treatment in mice induces ER stress and attenuated insulin signaling in liver and adipose tissue (not skeletal muscle); chemical chaperone PBA restores insulin sensitivity; PERK blockade partially nullifies PGRN-induced insulin resistance in hepatocytes and adipocytes.","method":"PGRN treatment of mice, PBA (ER stress inhibitor), PERK inhibitor in cell culture, glucose/insulin tolerance, insulin signaling markers, ER stress markers","journal":"Cell cycle (Georgetown, Tex.)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — pharmacological epistasis (PERK inhibitor, chemical chaperone), in vivo and in vitro, single lab","pmids":["26039714"],"is_preprint":false},{"year":2013,"finding":"PGRN haploinsufficiency activates noncanonical Wnt5a signaling: lymphoblasts from c.709-1G>A PGRN mutation carriers show increased Wnt5a protein (cellular and secreted), enhanced CaMKII phosphorylation, and activated ERK1/2 in a Ca2+/PKC/pertussis toxin-sensitive manner. Exogenous PGRN or control-conditioned medium normalized ERK1/2. PGRN knockdown in SH-SY5Y cells recapitulated increased Wnt5a.","method":"Lymphoblasts from FTLD-TDP PGRN mutation carriers, exogenous PGRN treatment, conditioned medium, ERK1/2 kinase assay, CaMKII phosphorylation, PGRN siRNA in SH-SY5Y, pertussis toxin, PKC inhibition","journal":"Neurobiology of aging","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — patient-derived cells plus siRNA model, multiple orthogonal approaches, single lab","pmids":["24139281"],"is_preprint":false},{"year":2011,"finding":"PGRN haploinsufficiency in lymphoblasts from c.709-1G>A FTLD-TDP patients increases cell cycle activity with elevated CDK6 and phospho-Rb, leading to G1/S regulatory failure; altered TDP-43 subcellular distribution may underlie CDK6 upregulation via loss of TDP-43 repression of CDK6.","method":"Patient lymphoblasts, cell cycle analysis, Western blot for CDK6, phospho-Rb, TDP-43 localization by immunofluorescence","journal":"Neurobiology of aging","confidence":"Medium","confidence_rationale":"Tier 2-3 / Moderate — patient-derived cells with multiple molecular readouts, single lab, mechanistic link to TDP-43 partially inferred","pmids":["21232819"],"is_preprint":false},{"year":2018,"finding":"Transcription factor REST represses PGRN expression by directly binding the PGRN promoter, and PGRN promotes microglia-like BV2 cell migration. REST knockdown increases PGRN expression and BV2 migration; REST overexpression suppresses both; siRNA targeting PGRN blocks the migration-promoting effect.","method":"siRNA knockdown of PGRN and REST, REST overexpression, dual luciferase reporter for PGRN promoter activity, transwell migration assay","journal":"Neural plasticity","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — luciferase reporter assay for direct promoter binding, siRNA and overexpression, single lab","pmids":["33299399"],"is_preprint":false},{"year":2023,"finding":"Antisense oligonucleotides (ASOs) that sterically block the miR-29b binding site in the 3' UTR of human GRN mRNA increase progranulin protein translation (not mRNA levels), as demonstrated by polysome profiling; ASOs competed with miR-29b for GRN 3' UTR binding in FRET assays and increased progranulin in iPSC-derived neurons and a humanized GRN mouse model.","method":"ASO screen in neuroglioma cells, FRET-based binding competition, polysome profiling, iPSC-derived neurons, humanized GRN mouse model, progranulin ELISA/Western blot","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — polysome profiling (mechanistic), FRET binding assay, in vitro and in vivo validation with multiple orthogonal methods","pmids":["37981208"],"is_preprint":false},{"year":2022,"finding":"PGRN is a modifier of glucocerebrosidase (GCase/GBA1) function in vivo: PGRN-deficient mice crossed with Gba1-D409V knock-in mice exhibit exacerbated neurobehavioral deficits, earlier onset, more severe Gaucher disease phenotypes, and PD-like pathology compared to single mutants, with severe neuroinflammation (microgliosis, astrogliosis) and impaired autophagy. A PGRN-derived peptide (ND7) crosses the blood-brain barrier and rescues disease phenotypes in nGD and PD models.","method":"Grn/Gba1 double-mutant mice, neuropathology, behavior, PGRN peptide ND7 BBB penetration and treatment, GD patient fibroblasts ex vivo","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic epistasis (double mutant), in vivo rescue with biologic, single lab","pmids":["36574647"],"is_preprint":false},{"year":2020,"finding":"PGRN-/- tumor-associated macrophages (TAMs) inhibit breast cancer cell invasion, migration, and EMT through their exosomes; miR-5100 is upregulated in PGRN-/- TAM-derived exosomes and targets CXCL12, thereby inhibiting the CXCL12/CXCR4 axis.","method":"PGRN-/- mouse xenograft model, flow cytometry, transwell/wound healing assays, Western blot, miRNA profiling, qPCR, luciferase reporter assay for miR-5100 target (CXCL12)","journal":"Life sciences","confidence":"Medium","confidence_rationale":"Tier 2-3 / Moderate — luciferase reporter, in vitro functional assays, in vivo model, single lab","pmids":["33181174"],"is_preprint":false},{"year":2020,"finding":"FAM135B directly interacts with progranulin (GRN) in esophageal squamous cell carcinoma cells, forming a feedforward loop with AKT/mTOR signaling to promote tumor proliferation; this interaction was identified by co-immunoprecipitation and mass spectrometry.","method":"Co-immunoprecipitation and mass spectrometry, ectopic FAM135B expression, in vitro proliferation, in vivo xenograft, serum GRN ELISA in FAM135B transgenic mice","journal":"Cancer research","confidence":"Medium","confidence_rationale":"Tier 2-3 / Moderate — Co-IP/MS identifies physical interaction, in vivo evidence, but mechanistic follow-up limited","pmids":["33323378"],"is_preprint":false},{"year":2024,"finding":"Progranulin mediates ADAR1 deficiency-induced liver pathology by promoting interferon signaling and recruiting EGFR+ macrophages into the liver; PGRN-EGFR crosstalk exacerbates hepatic inflammation in liver-specific Adar KO mice, and this communication is repressed in ADAR1-high tumors.","method":"Liver-specific Adar KO mice, Ifih1;Adar double KO, macrophage recruitment assays, PGRN neutralization/depletion, EGFR+ macrophage flow cytometry, interferon signaling assays","journal":"Cell reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic mouse models with defined pathway placement, single lab","pmids":["38935501"],"is_preprint":false},{"year":2021,"finding":"PGRN deficiency causes parkin (PRKN) downregulation in fibroblasts from FTLD patients with four different PGRN pathogenic variants, as well as in control fibroblasts upon PGRN silencing; PGRN knockdown also decreased parkin downstream targets MFN2 and VDAC1. TDP-43 overexpression rescued PRKN levels upon transient PGRN silencing but not in FTLD patient fibroblasts, and TDP-43 silencing itself caused PRKN decrease.","method":"Patient-derived fibroblasts, siRNA PGRN knockdown, TDP-43 overexpression/knockdown, Western blot for PRKN, MFN2, VDAC1","journal":"Frontiers in molecular neuroscience","confidence":"Medium","confidence_rationale":"Tier 2-3 / Moderate — patient cells plus siRNA and rescue experiments, multiple variants tested, single lab","pmids":["34054428"],"is_preprint":false},{"year":2018,"finding":"TSH upregulates PGRN expression in endothelial cells, and PGRN in turn upregulates Akt and eNOS expression; siRNA knockdown of PGRN in HUVECs suppresses both Akt and eNOS, placing PGRN downstream of TSH and upstream of the Akt/eNOS axis.","method":"HUVECs, TSH stimulation, PGRN siRNA knockdown, Western blot for eNOS, p-Akt, PGRN; NO and superoxide assays; SCH rat model","journal":"Frontiers in endocrinology","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single lab, siRNA knockdown with pathway readout, no direct binding or reconstitution","pmids":["30026730"],"is_preprint":false},{"year":2020,"finding":"PGRN suppresses inflammation and promotes autophagy in keratinocytes (HaCaT cells) through the Wnt/β-catenin signaling pathway: PGRN siRNA increases inflammatory cytokines (IL-1β, IL-6, COX-2, iNOS, MCP-1), suppresses autophagy markers (LC3II, Atg7), and upregulates β-catenin/cyclin D1/c-myc; these effects are reversed by the Wnt/β-catenin inhibitor IWP-2.","method":"PGRN siRNA and overexpression in HaCaT cells, Wnt/β-catenin inhibitor (IWP-2), cytokine ELISA, autophagy marker Western blot, β-catenin signaling reporter","journal":"Inflammation","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single lab, cell-based siRNA/OE, pharmacological epistasis with Wnt inhibitor only","pmids":["27239673"],"is_preprint":false},{"year":2018,"finding":"Reduction of PGRN by siRNA in wound healing mouse model augments fibrosis, skin thickness, and collagen I deposition, and increases TGF-β1, TGF-β receptor I, Smad3, and phospho-Smad3 expression, indicating PGRN normally suppresses TGF-β/Smad fibrotic signaling.","method":"Excisional wound model in mice, si-m-PGRN injection, histology (H&E, Masson's trichrome), RT-qPCR and Western blot for TGF-β1, TβRI, Smad3, P-Smad3, Col I","journal":"Histology and histopathology","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single knockdown approach, in vivo model, no direct binding or reconstitution of TGF-β/Smad pathway","pmids":["30561754"],"is_preprint":false}],"current_model":"Progranulin (PGRN/GRN) is a secreted glycoprotein that functions as a lysosomal and extracellular growth/survival factor: in lysosomes, PGRN-derived granulins maintain bis(monoacylglycero)phosphate (BMP) levels required for ganglioside and sphingolipid catabolism, and PGRN deficiency causes progressive lysosomal dysfunction (gangliosidosis, lipofuscinosis, impaired proteolysis and lipolysis); extracellularly, PGRN acts as an autocrine/paracrine growth factor that signals through cell-surface receptors (~120 kDa species) to activate MAPK/ERK and PI3K/AKT, regulates cell cycle entry via cyclin D1/CDK4, mediates estrogen-dependent proliferation in breast cancer, and in neurons suppresses Gas6-Tyro3-PKCα signaling to prevent tau phosphorylation at Ser203 and synaptic loss; PGRN also suppresses innate immune responses by binding NEMO (via its CDE granulin domains) and recruiting A20 to deubiquitinate K63-polyubiquitin chains on NEMO, thereby dampening NF-κB and IRF3-dependent interferon production, and it promotes anti-inflammatory macrophage (M2) polarization through direct TNFR2 binding; loss-of-function mutations cause haploinsufficiency, lysosomal storage disease (CLN11 when homozygous), frontotemporal dementia with TDP-43 pathology, and secondary defects including Wnt5a/CaMKII/ERK dysregulation, parkin downregulation, and astroglial toxicity driving synaptic degeneration."},"narrative":{"mechanistic_narrative":"Progranulin (GRN/PGRN) is a secreted glycoprotein with a dual life as a lysosomal cofactor and an extracellular growth/immunomodulatory factor [PMID:11134521, PMID:34450028]. In the endolysosomal compartment, PGRN is a pH-dependent interactor of the phospholipid bis(monoacylglycero)phosphate (BMP), and its loss causes global BMP deficiency that cripples sphingolipid catabolism—producing ganglioside and glucosylsphingosine accumulation despite intact catabolic enzymes—and impairs proteolysis, lipolysis, and redox homeostasis [PMID:34450028, PMID:36207292]. This lysosomal failure manifests in vivo as defective microglial clearance of myelin debris downstream of cathepsin D, with PGRN acting genetically upstream of cathepsin D-dependent clearance and interacting with TMEM106B such that combined loss produces accelerated lysosomal vacuolation and neuronal loss [PMID:34433069, PMID:32852886]. PGRN deficiency also functions as a disease modifier of glucocerebrosidase (GBA1), exacerbating Gaucher- and Parkinson-like neuropathology [PMID:36574647]. Loss of PGRN drives frontotemporal dementia with TDP-43 pathology through multiple effector arms: disinhibited Gas6-Tyro3 signaling activates PKCα to phosphorylate tau at Ser203 and cause dendritic spine loss [PMID:29382817], PGRN-deficient astrocytes acquire a reactive transcriptional state (GJA1/AQP4/APOE up, SLC1A2 down) that directly induces synaptic degeneration and TDP-43 proteinopathy [PMID:36602862], and patient cells show noncanonical Wnt5a/CaMKII/ERK dysregulation and parkin downregulation [PMID:24139281, PMID:34054428]. Extracellularly, PGRN binds cell-surface receptors and acts as an autocrine mitogen, mediating estrogen-dependent proliferation and tumorigenesis via cyclin D1/CDK4 and MAPK activation [PMID:11134521, PMID:9826678, PMID:10760271, PMID:17261172]. As an immune regulator, PGRN dampens type I interferon production by binding NF-κB essential modulator (NEMO) through its granulin CDE domains and recruiting A20 to deubiquitinate K63-linked chains on NEMO [PMID:31585000], and it promotes anti-inflammatory M2 macrophage polarization through direct TNFR2 binding [PMID:25387791, PMID:38689292]. PGRN levels are controlled post-transcriptionally by TMEM106B and by miR-29b binding within the GRN 3' UTR, the latter being a therapeutic target for translational upregulation [PMID:21178100, PMID:37981208]. Haploinsufficiency from loss-of-function GRN mutations underlies frontotemporal dementia with TDP-43 pathology [PMID:24139281, PMID:21232819].","teleology":[{"year":1998,"claim":"Established that PGRN is a secreted autocrine growth factor whose expression is required for tumorigenicity and that it engages specific cell-surface receptors, defining its extracellular signaling identity.","evidence":"Antisense inhibition with in vivo tumor formation in syngeneic mice; radiolabeled ligand binding with Scatchard analysis and crosslinking on epithelial and fibroblast cells","pmids":["9826678","10760271","9571191"],"confidence":"High","gaps":["The molecular identity of the ~120 kDa crosslinked receptor species was not determined","No reciprocal validation of receptor binding partners"]},{"year":2001,"claim":"Defined the downstream mitogenic mechanism by showing PGRN mediates estrogen-driven proliferation via cyclin D1 induction and MAP kinase activation, linking it to hormone-dependent breast cancer growth.","evidence":"Neutralizing antibody, antisense, and overexpression in MCF-7 cells with MAP kinase and cyclin D1 readouts","pmids":["11134521"],"confidence":"High","gaps":["Receptor mediating the estrogen-PGRN-cyclin D1 axis not identified","Did not address PGRN's lysosomal/neuronal roles"]},{"year":2007,"claim":"Generalized PGRN's proliferative role to ovarian cancer and placed it upstream of cell-cycle entry (cyclin D1/CDK4) and matrix remodeling (MMP-2/MMP-9, VEGF), connecting mitogenesis to invasion.","evidence":"Antisense loss-of-function in ovarian cancer cells with proliferation, invasion, and zymography readouts; overexpression with MMP-9/VEGF assays","pmids":["17261172","15117809"],"confidence":"Medium","gaps":["Mechanism linking PGRN to MMP/VEGF transcription unresolved","Single-lab functional data"]},{"year":2010,"claim":"Identified TMEM106B as a post-transcriptional modulator of circulating PGRN levels, introducing a genetic axis governing PGRN dosage relevant to neurodegeneration risk.","evidence":"Genetic association with plasma PGRN ELISA and inverse mRNA correlation in peripheral blood cohorts","pmids":["21178100"],"confidence":"Medium","gaps":["Observational correlation without direct mechanistic experiment","Did not define the molecular mode of TMEM106B regulation"]},{"year":2013,"claim":"Connected PGRN haploinsufficiency in FTLD patient cells to aberrant cell cycle re-entry and noncanonical Wnt5a/CaMKII/ERK signaling, offering candidate effectors of neuronal dysfunction.","evidence":"FTLD-TDP patient lymphoblasts and SH-SY5Y knockdown with cell cycle analysis, CDK6/phospho-Rb blots, Wnt5a/CaMKII/ERK readouts, conditioned medium rescue","pmids":["24139281","21232819"],"confidence":"Medium","gaps":["Link from PGRN loss to CDK6 via TDP-43 partially inferred","Patient-cell findings from single lab"]},{"year":2014,"claim":"Defined PGRN as an anti-inflammatory mediator acting through IL-10- and TNFR2-dependent pathways in colitis, establishing its protective immunoregulatory function in vivo.","evidence":"PGRN-/-, IL-10-/-, TNFR2-/- mice in DSS/TNBS colitis with recombinant PGRN rescue and bone marrow chimeras","pmids":["25387791"],"confidence":"High","gaps":["Did not directly demonstrate PGRN-TNFR2 physical binding (resolved later)","Cell type executing protection not fully resolved"]},{"year":2015,"claim":"Showed that excess PGRN impairs hepatic and adipose insulin sensitivity through TNFR1/NF-κB and PERK-eIF2α ER stress signaling, revealing a context-dependent metabolic role distinct from its anti-inflammatory actions.","evidence":"PGRN treatment of mice with TNFR1 blocking peptide/siRNA, PERK inhibitor, and chemical chaperone PBA, plus insulin/autophagy/ER stress readouts","pmids":["25664864","26039714"],"confidence":"Medium","gaps":["Reconciliation with PGRN's protective TNFR2 signaling not addressed","Single-lab pharmacological epistasis"]},{"year":2018,"claim":"Identified a specific neurodegenerative mechanism whereby PGRN reduction disinhibits Gas6-Tyro3 signaling, activating PKCα to phosphorylate tau at Ser203 and drive spine loss, providing a druggable pathway.","evidence":"PGRN-R504X knock-in mice, phosphoproteomics, PKCα kinase assay, pharmacological and siRNA rescue of spine loss and cognition","pmids":["29382817"],"confidence":"High","gaps":["How PGRN normally restrains Gas6-Tyro3 binding mechanistically unresolved","Relationship to TDP-43 pathology not directly tested"]},{"year":2019,"claim":"Resolved the molecular mechanism of PGRN's interferon suppression by showing direct NEMO binding via granulin CDE domains and A20 recruitment to deubiquitinate K63 chains on NEMO at K264.","evidence":"Reciprocal Co-IP, domain mapping, deubiquitination assays, PGRN-deficient mice, and neutralizing antibody with type I IFN quantification","pmids":["31585000"],"confidence":"High","gaps":["Subcellular site of PGRN-NEMO interaction not defined","Stoichiometry of the PGRN-NEMO-A20 assembly unknown"]},{"year":2021,"claim":"Reframed PGRN as a lysosomal cofactor by identifying pH-dependent BMP binding, with deficiency causing global BMP loss, sphingolipid storage, microglial myelin-clearance failure, and TMEM106B genetic interaction—unifying its neurodegenerative phenotypes around lysosomal dysfunction.","evidence":"Grn-/- mice, lipidomics, pH-dependent binding assays, iPSC-microglia, PTV:PGRN replacement, Ctsd/Grn and Tmem106b/Pgrn double-KO epistasis, EM","pmids":["34450028","34433069","32852886"],"confidence":"High","gaps":["The structural basis of granulin-BMP interaction not resolved","How BMP maintenance mechanistically couples to enzyme function unclear"]},{"year":2022,"claim":"Extended the lysosomal model by demonstrating PGRN-dependent BMP maintenance is required for ganglioside catabolism and that PGRN modifies glucocerebrosidase function in vivo, linking PGRN to multiple sphingolipidoses.","evidence":"Ganglioside mass spectrometry and enzyme assays in human/mouse PGRN-deficient tissue; Grn/Gba1 double-mutant mice with ND7 peptide rescue","pmids":["36207292","36574647"],"confidence":"Medium","gaps":["Direct biochemical reconstitution of granulin enhancement of catabolism not shown","GBA1 modifier mechanism in part inferred"]},{"year":2023,"claim":"Demonstrated a non-cell-autonomous neurodegenerative mechanism in which PGRN-deficient reactive astrocytes directly induce synaptic degeneration and TDP-43 proteinopathy, identifying astrocytes as drivers rather than bystanders.","evidence":"Single-nucleus RNA-seq in Grn-/- mice and FTD-GRN tissue, astrocyte-neuron cocultures, and iPSC-astrocyte organoid transplantation","pmids":["36602862"],"confidence":"High","gaps":["Astrocyte-secreted factor mediating synaptic toxicity not identified","Interplay with microglial lysosomal defects not resolved"]},{"year":2024,"claim":"Confirmed direct PGRN-TNFR2 binding driving M2 macrophage polarization and revealed a PGRN-EGFR axis recruiting macrophages in interferon-driven liver pathology, broadening PGRN's immunoreceptor repertoire.","evidence":"Co-IP and TNFR2 neutralizing antibody with M2 markers; liver-specific Adar KO mice with PGRN depletion and EGFR+ macrophage profiling","pmids":["38689292","38935501"],"confidence":"Medium","gaps":["Single-lab Co-IP for TNFR2 without reciprocal/structural validation","Whether PGRN binds EGFR directly not established"]},{"year":2023,"claim":"Established miR-29b-mediated translational repression of GRN as a therapeutically actionable lever, with steric-block ASOs raising progranulin protein without changing mRNA.","evidence":"ASO screen, FRET binding competition, polysome profiling, iPSC-neurons, and humanized GRN mouse model","pmids":["37981208"],"confidence":"High","gaps":["Endogenous physiological regulation of miR-29b on GRN not characterized","Other 3' UTR regulators not surveyed"]},{"year":null,"claim":"The identity and signaling logic of the cell-surface PGRN receptor(s) mediating its extracellular growth-factor activity, and how the lysosomal BMP-cofactor role mechanistically couples to the extracellular receptor signaling, remain unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["The ~120 kDa receptor species remains molecularly unidentified","No unified model linking lysosomal granulin function to extracellular MAPK/PI3K signaling","Structural basis of granulin domain-specific functions not determined"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0008289","term_label":"lipid binding","supporting_discovery_ids":[6]},{"term_id":"GO:0048018","term_label":"receptor ligand activity","supporting_discovery_ids":[0,1,2]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[12,13,14]},{"term_id":"GO:0060089","term_label":"molecular transducer activity","supporting_discovery_ids":[12,14]}],"localization":[{"term_id":"GO:0005764","term_label":"lysosome","supporting_discovery_ids":[6,7,8]},{"term_id":"GO:0005576","term_label":"extracellular region","supporting_discovery_ids":[0,1,2]}],"pathway":[{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[12,13,14]},{"term_id":"R-HSA-1430728","term_label":"Metabolism","supporting_discovery_ids":[6,7]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[0,10,17]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[8,9,11]},{"term_id":"R-HSA-1640170","term_label":"Cell Cycle","supporting_discovery_ids":[0,4,18]}],"complexes":[],"partners":["TMEM106B","NEMO/IKBKG","A20/TNFAIP3","TNFR2/TNFRSF1B","TNFR1/TNFRSF1A","FAM135B","TYRO3","GBA1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P28799","full_name":"Progranulin","aliases":["Acrogranin","Epithelin precursor","Glycoprotein of 88 Kda","GP88","Glycoprotein 88","Granulin precursor","PC cell-derived growth factor","PCDGF","Proepithelin","PEPI"],"length_aa":593,"mass_kda":63.5,"function":"Secreted protein that acts as a key regulator of lysosomal function and as a growth factor involved in inflammation, wound healing and cell proliferation (PubMed:12526812, PubMed:18378771, PubMed:28073925, PubMed:28453791, PubMed:28541286). Regulates protein trafficking to lysosomes, and also the activity of lysosomal enzymes (PubMed:28453791, PubMed:28541286). Also facilitates the acidification of lysosomes, causing degradation of mature CTSD by CTSB (PubMed:28073925). In addition, functions as a wound-related growth factor that acts directly on dermal fibroblasts and endothelial cells to promote division, migration and the formation of capillary-like tubule structures (By similarity). Also promotes epithelial cell proliferation by blocking TNF-mediated neutrophil activation preventing release of oxidants and proteases (PubMed:12526812). Moreover, modulates inflammation in neurons by preserving neurons survival, axonal outgrowth and neuronal integrity (PubMed:18378771) Promotes proliferation of the epithelial cell line A431 in culture Inhibits epithelial cell proliferation and induces epithelial cells to secrete IL-8 Stabilizes CTSD through interaction with CTSD leading to maintain its aspartic-type peptidase activity","subcellular_location":"Secreted; Lysosome","url":"https://www.uniprot.org/uniprotkb/P28799/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/GRN","classification":"Not Classified","n_dependent_lines":13,"n_total_lines":1208,"dependency_fraction":0.01076158940397351},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/GRN","total_profiled":1310},"omim":[{"mim_id":"621213","title":"FAMILY WITH SEQUENCE SIMILARITY 171, MEMBER A2; FAM171A2","url":"https://www.omim.org/entry/621213"},{"mim_id":"615596","title":"CONGENITAL DISORDER OF GLYCOSYLATION, TYPE Iw, AUTOSOMAL RECESSIVE; CDG1WAR","url":"https://www.omim.org/entry/615596"},{"mim_id":"614706","title":"CEROID LIPOFUSCINOSIS, NEURONAL, 11; CLN11","url":"https://www.omim.org/entry/614706"},{"mim_id":"613556","title":"MICRO RNA 659; MIR659","url":"https://www.omim.org/entry/613556"},{"mim_id":"613413","title":"TRANSMEMBRANE PROTEIN 106B; TMEM106B","url":"https://www.omim.org/entry/613413"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Enhanced","locations":[{"location":"Lysosomes","reliability":"Enhanced"},{"location":"Endosomes","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/GRN"},"hgnc":{"alias_symbol":["PCDGF","PGRN","CLN11"],"prev_symbol":[]},"alphafold":{"accession":"P28799","domains":[{"cath_id":"-","chopping":"23-115","consensus_level":"medium","plddt":75.9111,"start":23,"end":115},{"cath_id":"2.10.25","chopping":"125-196","consensus_level":"medium","plddt":86.1476,"start":125,"end":196},{"cath_id":"-","chopping":"207-279","consensus_level":"medium","plddt":87.1229,"start":207,"end":279},{"cath_id":"2.10.25","chopping":"282-353","consensus_level":"medium","plddt":85.3726,"start":282,"end":353},{"cath_id":"2.10.25","chopping":"365-434","consensus_level":"medium","plddt":88.2061,"start":365,"end":434},{"cath_id":"-","chopping":"452-497","consensus_level":"high","plddt":81.9237,"start":452,"end":497},{"cath_id":"2.10.25","chopping":"525-575","consensus_level":"high","plddt":85.4796,"start":525,"end":575}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P28799","model_url":"https://alphafold.ebi.ac.uk/files/AF-P28799-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P28799-F1-predicted_aligned_error_v6.png","plddt_mean":77.0},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=GRN","jax_strain_url":"https://www.jax.org/strain/search?query=GRN"},"sequence":{"accession":"P28799","fasta_url":"https://rest.uniprot.org/uniprotkb/P28799.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P28799/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P28799"}},"corpus_meta":[{"pmid":"21178100","id":"PMC_21178100","title":"TMEM106B regulates progranulin levels and the penetrance of FTLD in GRN mutation carriers.","date":"2010","source":"Neurology","url":"https://pubmed.ncbi.nlm.nih.gov/21178100","citation_count":219,"is_preprint":false},{"pmid":"18771956","id":"PMC_18771956","title":"Mutations in progranulin (GRN) within the spectrum of clinical and pathological phenotypes of frontotemporal dementia.","date":"2008","source":"The Lancet. 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diseases.","date":"2022","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/36574647","citation_count":14,"is_preprint":false},{"pmid":"31818769","id":"PMC_31818769","title":"Interaction between PGRN gene and the early trauma on clinical characteristics in patients with obsessive-compulsive disorder.","date":"2019","source":"Journal of affective disorders","url":"https://pubmed.ncbi.nlm.nih.gov/31818769","citation_count":14,"is_preprint":false},{"pmid":"31918955","id":"PMC_31918955","title":"Trajectory of lobar atrophy in asymptomatic and symptomatic GRN mutation carriers: a longitudinal MRI study.","date":"2019","source":"Neurobiology of aging","url":"https://pubmed.ncbi.nlm.nih.gov/31918955","citation_count":14,"is_preprint":false},{"pmid":"38935501","id":"PMC_38935501","title":"Hepatocyte-macrophage crosstalk via the PGRN-EGFR axis modulates ADAR1-mediated immunity in the 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resistance.\",\n      \"method\": \"Neutralizing antibody, antisense transfection, PCDGF overexpression, MAP kinase assay, cyclin D1 immunoblot, DNA synthesis assay\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (antibody, antisense, overexpression) in a single focused study with direct functional readouts\",\n      \"pmids\": [\"11134521\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"PCDGF/progranulin expression is required for tumorigenicity of PC teratoma cells; antisense-mediated inhibition of PCDGF expression dramatically reduced tumor formation in syngeneic mice, demonstrating that autocrine PCDGF production drives tumorigenesis.\",\n      \"method\": \"Antisense PCDGF cDNA transfection, in vivo tumor formation assay in syngeneic mice, Northern/Western blot\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean loss-of-function with defined in vivo phenotype, replicated in breast carcinoma model (PMID:10760271)\",\n      \"pmids\": [\"9826678\", \"10760271\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"PCDGF/progranulin binds to two classes of cell-surface receptors on mink lung epithelial cells (CCL64): high-affinity sites (Kd ~43 pM, ~560 sites/cell) and low-affinity sites (Kd ~3.9 nM, ~16,350 sites/cell); chemical crosslinking identified a ~120 kDa receptor species; similar binding sites were detected on 3T3 fibroblasts and PC cells.\",\n      \"method\": \"Radiolabeled ligand binding (125I-PCDGF), Scatchard analysis, chemical crosslinking with disuccinimidyl suberate, SDS-PAGE\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct binding assay with Scatchard analysis and crosslinking, single lab, receptor identity not further confirmed\",\n      \"pmids\": [\"9571191\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Progranulin/PCDGF overexpression in MCF-7 breast cancer cells stimulates anchorage-independent growth, cell migration through Matrigel, upregulation of matrix metalloprotease-9 (by gelatin zymography and immunoblot), and VEGF expression, implicating progranulin in invasion and angiogenesis.\",\n      \"method\": \"Stable overexpression, exogenous protein treatment, gelatin zymography, immunoblot for MMP-9 and VEGF, transwell migration assay\",\n      \"journal\": \"Carcinogenesis\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — overexpression and exogenous treatment with multiple functional readouts, single lab\",\n      \"pmids\": [\"15117809\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Antisense-mediated inhibition of PCDGF/progranulin in ovarian cancer cells (SW626, A2780) reduced proliferation and invasion, and decreased cyclin D1 and CDK4 expression while inactivating MMP-2, placing progranulin upstream of cell cycle entry and extracellular matrix remodeling.\",\n      \"method\": \"Antisense PCDGF cDNA transfection, MTT proliferation assay, Boyden chamber invasion assay, RT-PCR and Western blot for cyclin D1/CDK4, gelatin zymography for MMP-2\",\n      \"journal\": \"BMC cancer\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — loss-of-function with multiple molecular readouts, single lab\",\n      \"pmids\": [\"17261172\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"TMEM106B SNPs are significantly associated with plasma progranulin (GRN) levels in controls, and TMEM106B and GRN mRNA expression are inversely correlated in peripheral blood, indicating TMEM106B modulates progranulin levels post-transcriptionally.\",\n      \"method\": \"Genetic association study with plasma PGRN ELISA, correlation of TMEM106B and GRN mRNA expression in blood samples\",\n      \"journal\": \"Neurology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — observational correlation in large cohort (n>1000 for plasma), replicated in two sample sets, no direct mechanistic experiment\",\n      \"pmids\": [\"21178100\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Progranulin (PGRN) is a pH-dependent interactor of bis(monoacylglycero)phosphate (BMP), an endolysosomal phospholipid; PGRN deficiency causes global BMP deficiency and impairs lysosomal proteolysis, lipolysis, and redox homeostasis. Secondary glucosylsphingosine storage occurs in aged Grn-/- brains. A brain-penetrant PTV:PGRN biologic rescued BMP levels, glucosylsphingosine accumulation, oxidative stress, lysosomal dysfunction, microgliosis, and lipofuscinosis in Grn-/- mice and human iPSC-derived microglia.\",\n      \"method\": \"Grn-/- mouse model, lipidomic profiling of BMP, pH-dependent binding assays, iPSC-derived microglia, protein replacement therapy, mass spectrometry, lysosomal functional assays\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — multiple orthogonal methods (lipidomics, binding assay, functional rescue in vivo and in vitro), rigorous controls, high-impact venue\",\n      \"pmids\": [\"34450028\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"PGRN deficiency causes gangliosidosis: PGRN-deficient human cells, murine brains, and human FTD-GRN frontal lobes accumulate gangliosides. Lysosomal enzymes that catabolize gangliosides are present at normal levels, but BMP levels are reduced, implicating PGRN-derived granulins in maintaining BMP levels required for ganglioside catabolism.\",\n      \"method\": \"PGRN-deficient human cells and Grn-/- mouse brains, human FTD-GRN tissue, ganglioside mass spectrometry, lysosomal enzyme activity assays, BMP lipid profiling\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — multiple orthogonal methods (lipidomics, enzyme assays, human and mouse tissue), mechanistically consistent with PMID:34450028\",\n      \"pmids\": [\"36207292\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"In Grn knockout mice, microglia accumulate myelin debris in lysosomes in white matter regions. PGRN insufficiency in microglia leads to impaired lysosomal-mediated clearance of myelin debris. Grn KO mice deficient in cathepsin D have augmented myelin debris and increased neuronal TDP-43 pathology, placing PGRN upstream of cathepsin D-dependent lysosomal clearance of myelin.\",\n      \"method\": \"Grn-/- mouse model, electron microscopy, immunofluorescence, Ctsd/Grn double-KO genetic epistasis, human FTD-GRN tissue immunostaining\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic epistasis (double KO), multiple orthogonal methods, human tissue validation\",\n      \"pmids\": [\"34433069\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Simultaneous loss of both PGRN and TMEM106B in mice results in severe neuronal loss, glial activation, enlarged lysosomes in microglia and astrocytes, and enhanced accumulation of lysosomal vacuoles at the axon initial segment of motor neurons, with much earlier onset than single knockouts, demonstrating genetic interaction between TMEM106B and PGRN in lysosomal function and neurodegeneration.\",\n      \"method\": \"Pgrn/Tmem106b double-knockout mouse model, neuropathology, immunohistochemistry, electron microscopy\",\n      \"journal\": \"EMBO reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic epistasis (double KO vs single KOs), clear phenotypic hierarchy established\",\n      \"pmids\": [\"32852886\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"In a PGRN-R504X knock-in mouse model, PGRN reduction leads to disinhibition of Gas6 binding to Tyro3, activating PKCα via PLCγ, which phosphorylates tau at Ser203, causing tau mislocalization to dendritic spines and spine loss. PKC inhibitor, B-Raf inhibitor, or knockdown of Gas6-Tyro3-tau pathway members rescued spine loss and cognitive impairment.\",\n      \"method\": \"Phosphoproteomic analysis, PGRN-R504X knock-in mice, PKCα kinase assay, pharmacological inhibition (PKC inhibitor, B-Raf inhibitor), siRNA knockdown, dendritic spine imaging, behavioral testing\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — phosphoproteomics, kinase identification, genetic and pharmacological rescue, multiple orthogonal methods\",\n      \"pmids\": [\"29382817\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Progranulin-deficient astrocytes drive synaptic degeneration in the thalamocortical circuit: single-cell transcriptomics in Grn-/- mice and FTD-GRN patients revealed conserved upregulation of GJA1, AQP4, and APOE and downregulation of glutamate transporter SLC1A2. Progranulin-deficient astrocytes in cocultures and cortical organoid transplant experiments directly induced synaptic degeneration, neuronal stress, and TDP-43 proteinopathy.\",\n      \"method\": \"Single-nucleus RNA-seq, Grn-/- mice, FTD-GRN human tissue, iPSC-derived astrocyte transplantation into cortical organoids, astrocyte-neuron cocultures, immunostaining for TDP-43 and synaptic markers\",\n      \"journal\": \"The Journal of clinical investigation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — functional coculture and organoid transplantation experiments, human-mouse conservation, multiple orthogonal methods\",\n      \"pmids\": [\"36602862\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Influenza virus-induced progranulin (PGRN) negatively regulates type I interferon production by inhibiting NF-κB and IRF3 signaling. Mechanistically, PGRN directly interacts with NF-κB essential modulator (NEMO) via its Grn CDE domains and recruits A20 to deubiquitinate K63-linked polyubiquitin chains on NEMO at K264.\",\n      \"method\": \"PGRN knockdown, PGRN-deficient mice, co-immunoprecipitation of PGRN with NEMO, domain mapping (Grn CDE), deubiquitination assay showing A20 recruitment, PGRN neutralizing antibody in vivo, type I IFN quantification\",\n      \"journal\": \"PLoS pathogens\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP, domain mapping, deubiquitination mechanism identified, in vivo validation\",\n      \"pmids\": [\"31585000\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Progranulin exerts anti-inflammatory protection in colitis in an IL-10- and TNFR2-dependent manner: PGRN-deficient mice show heightened susceptibility to colitis, and recombinant PGRN is protective. The protective effect was largely absent in IL-10-deficient and TNFR2-deficient colitis models, placing PGRN's action downstream of or in the same pathway as both IL-10 and TNFR2.\",\n      \"method\": \"PGRN-/-, IL-10-/-, and TNFR2-/- mice, DSS and TNBS colitis models, bone marrow chimera, CD4+ T cell transfer, recombinant PGRN treatment, histological scoring\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple genetic knockout models, epistasis (triple pathway testing), in vivo rescue\",\n      \"pmids\": [\"25387791\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"PGRN directly binds TNFR2 (confirmed by co-immunoprecipitation), co-localizes with TNFR2 on M2 macrophages, and promotes macrophage M2 polarization through TNFR2; TNFR2-blocking antibody inhibits PGRN-mediated M2 polarization.\",\n      \"method\": \"Co-immunoprecipitation, multiplex immunohistochemistry, TNFR2 neutralizing antibody, flow cytometry, ELISA for M1/M2 markers\",\n      \"journal\": \"Journal of translational medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 / Moderate — Co-IP plus functional neutralizing antibody, single lab\",\n      \"pmids\": [\"38689292\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"PGRN impairs hepatic insulin sensitivity via TNFR1/NF-κB signaling: in vivo PGRN treatment impairs glucose and insulin tolerance with hepatic autophagy imbalance; TNFR1 blocking peptide-Fc restores insulin sensitivity and autophagy. In hepatocytes, PGRN-induced insulin resistance and autophagy defects are nullified by TNFR1 siRNA via TNFR1-NF-κB-dependent manner.\",\n      \"method\": \"PGRN treatment of mice for 21 days, TNFR1 blocking peptide-Fc, TNFR1 siRNA in hepatocytes, glucose/insulin tolerance tests, autophagy markers (LC3, p62), insulin signaling (Akt phosphorylation)\",\n      \"journal\": \"Molecular endocrinology (Baltimore, Md.)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo and in vitro pharmacological and genetic intervention, single lab\",\n      \"pmids\": [\"25664864\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"PGRN triggers ER stress and impairs insulin sensitivity via the PERK-eIF2α axis: PGRN treatment in mice induces ER stress and attenuated insulin signaling in liver and adipose tissue (not skeletal muscle); chemical chaperone PBA restores insulin sensitivity; PERK blockade partially nullifies PGRN-induced insulin resistance in hepatocytes and adipocytes.\",\n      \"method\": \"PGRN treatment of mice, PBA (ER stress inhibitor), PERK inhibitor in cell culture, glucose/insulin tolerance, insulin signaling markers, ER stress markers\",\n      \"journal\": \"Cell cycle (Georgetown, Tex.)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — pharmacological epistasis (PERK inhibitor, chemical chaperone), in vivo and in vitro, single lab\",\n      \"pmids\": [\"26039714\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"PGRN haploinsufficiency activates noncanonical Wnt5a signaling: lymphoblasts from c.709-1G>A PGRN mutation carriers show increased Wnt5a protein (cellular and secreted), enhanced CaMKII phosphorylation, and activated ERK1/2 in a Ca2+/PKC/pertussis toxin-sensitive manner. Exogenous PGRN or control-conditioned medium normalized ERK1/2. PGRN knockdown in SH-SY5Y cells recapitulated increased Wnt5a.\",\n      \"method\": \"Lymphoblasts from FTLD-TDP PGRN mutation carriers, exogenous PGRN treatment, conditioned medium, ERK1/2 kinase assay, CaMKII phosphorylation, PGRN siRNA in SH-SY5Y, pertussis toxin, PKC inhibition\",\n      \"journal\": \"Neurobiology of aging\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — patient-derived cells plus siRNA model, multiple orthogonal approaches, single lab\",\n      \"pmids\": [\"24139281\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"PGRN haploinsufficiency in lymphoblasts from c.709-1G>A FTLD-TDP patients increases cell cycle activity with elevated CDK6 and phospho-Rb, leading to G1/S regulatory failure; altered TDP-43 subcellular distribution may underlie CDK6 upregulation via loss of TDP-43 repression of CDK6.\",\n      \"method\": \"Patient lymphoblasts, cell cycle analysis, Western blot for CDK6, phospho-Rb, TDP-43 localization by immunofluorescence\",\n      \"journal\": \"Neurobiology of aging\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 / Moderate — patient-derived cells with multiple molecular readouts, single lab, mechanistic link to TDP-43 partially inferred\",\n      \"pmids\": [\"21232819\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Transcription factor REST represses PGRN expression by directly binding the PGRN promoter, and PGRN promotes microglia-like BV2 cell migration. REST knockdown increases PGRN expression and BV2 migration; REST overexpression suppresses both; siRNA targeting PGRN blocks the migration-promoting effect.\",\n      \"method\": \"siRNA knockdown of PGRN and REST, REST overexpression, dual luciferase reporter for PGRN promoter activity, transwell migration assay\",\n      \"journal\": \"Neural plasticity\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — luciferase reporter assay for direct promoter binding, siRNA and overexpression, single lab\",\n      \"pmids\": [\"33299399\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Antisense oligonucleotides (ASOs) that sterically block the miR-29b binding site in the 3' UTR of human GRN mRNA increase progranulin protein translation (not mRNA levels), as demonstrated by polysome profiling; ASOs competed with miR-29b for GRN 3' UTR binding in FRET assays and increased progranulin in iPSC-derived neurons and a humanized GRN mouse model.\",\n      \"method\": \"ASO screen in neuroglioma cells, FRET-based binding competition, polysome profiling, iPSC-derived neurons, humanized GRN mouse model, progranulin ELISA/Western blot\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — polysome profiling (mechanistic), FRET binding assay, in vitro and in vivo validation with multiple orthogonal methods\",\n      \"pmids\": [\"37981208\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"PGRN is a modifier of glucocerebrosidase (GCase/GBA1) function in vivo: PGRN-deficient mice crossed with Gba1-D409V knock-in mice exhibit exacerbated neurobehavioral deficits, earlier onset, more severe Gaucher disease phenotypes, and PD-like pathology compared to single mutants, with severe neuroinflammation (microgliosis, astrogliosis) and impaired autophagy. A PGRN-derived peptide (ND7) crosses the blood-brain barrier and rescues disease phenotypes in nGD and PD models.\",\n      \"method\": \"Grn/Gba1 double-mutant mice, neuropathology, behavior, PGRN peptide ND7 BBB penetration and treatment, GD patient fibroblasts ex vivo\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic epistasis (double mutant), in vivo rescue with biologic, single lab\",\n      \"pmids\": [\"36574647\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"PGRN-/- tumor-associated macrophages (TAMs) inhibit breast cancer cell invasion, migration, and EMT through their exosomes; miR-5100 is upregulated in PGRN-/- TAM-derived exosomes and targets CXCL12, thereby inhibiting the CXCL12/CXCR4 axis.\",\n      \"method\": \"PGRN-/- mouse xenograft model, flow cytometry, transwell/wound healing assays, Western blot, miRNA profiling, qPCR, luciferase reporter assay for miR-5100 target (CXCL12)\",\n      \"journal\": \"Life sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 / Moderate — luciferase reporter, in vitro functional assays, in vivo model, single lab\",\n      \"pmids\": [\"33181174\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"FAM135B directly interacts with progranulin (GRN) in esophageal squamous cell carcinoma cells, forming a feedforward loop with AKT/mTOR signaling to promote tumor proliferation; this interaction was identified by co-immunoprecipitation and mass spectrometry.\",\n      \"method\": \"Co-immunoprecipitation and mass spectrometry, ectopic FAM135B expression, in vitro proliferation, in vivo xenograft, serum GRN ELISA in FAM135B transgenic mice\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 / Moderate — Co-IP/MS identifies physical interaction, in vivo evidence, but mechanistic follow-up limited\",\n      \"pmids\": [\"33323378\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Progranulin mediates ADAR1 deficiency-induced liver pathology by promoting interferon signaling and recruiting EGFR+ macrophages into the liver; PGRN-EGFR crosstalk exacerbates hepatic inflammation in liver-specific Adar KO mice, and this communication is repressed in ADAR1-high tumors.\",\n      \"method\": \"Liver-specific Adar KO mice, Ifih1;Adar double KO, macrophage recruitment assays, PGRN neutralization/depletion, EGFR+ macrophage flow cytometry, interferon signaling assays\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic mouse models with defined pathway placement, single lab\",\n      \"pmids\": [\"38935501\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"PGRN deficiency causes parkin (PRKN) downregulation in fibroblasts from FTLD patients with four different PGRN pathogenic variants, as well as in control fibroblasts upon PGRN silencing; PGRN knockdown also decreased parkin downstream targets MFN2 and VDAC1. TDP-43 overexpression rescued PRKN levels upon transient PGRN silencing but not in FTLD patient fibroblasts, and TDP-43 silencing itself caused PRKN decrease.\",\n      \"method\": \"Patient-derived fibroblasts, siRNA PGRN knockdown, TDP-43 overexpression/knockdown, Western blot for PRKN, MFN2, VDAC1\",\n      \"journal\": \"Frontiers in molecular neuroscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 / Moderate — patient cells plus siRNA and rescue experiments, multiple variants tested, single lab\",\n      \"pmids\": [\"34054428\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"TSH upregulates PGRN expression in endothelial cells, and PGRN in turn upregulates Akt and eNOS expression; siRNA knockdown of PGRN in HUVECs suppresses both Akt and eNOS, placing PGRN downstream of TSH and upstream of the Akt/eNOS axis.\",\n      \"method\": \"HUVECs, TSH stimulation, PGRN siRNA knockdown, Western blot for eNOS, p-Akt, PGRN; NO and superoxide assays; SCH rat model\",\n      \"journal\": \"Frontiers in endocrinology\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single lab, siRNA knockdown with pathway readout, no direct binding or reconstitution\",\n      \"pmids\": [\"30026730\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"PGRN suppresses inflammation and promotes autophagy in keratinocytes (HaCaT cells) through the Wnt/β-catenin signaling pathway: PGRN siRNA increases inflammatory cytokines (IL-1β, IL-6, COX-2, iNOS, MCP-1), suppresses autophagy markers (LC3II, Atg7), and upregulates β-catenin/cyclin D1/c-myc; these effects are reversed by the Wnt/β-catenin inhibitor IWP-2.\",\n      \"method\": \"PGRN siRNA and overexpression in HaCaT cells, Wnt/β-catenin inhibitor (IWP-2), cytokine ELISA, autophagy marker Western blot, β-catenin signaling reporter\",\n      \"journal\": \"Inflammation\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single lab, cell-based siRNA/OE, pharmacological epistasis with Wnt inhibitor only\",\n      \"pmids\": [\"27239673\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Reduction of PGRN by siRNA in wound healing mouse model augments fibrosis, skin thickness, and collagen I deposition, and increases TGF-β1, TGF-β receptor I, Smad3, and phospho-Smad3 expression, indicating PGRN normally suppresses TGF-β/Smad fibrotic signaling.\",\n      \"method\": \"Excisional wound model in mice, si-m-PGRN injection, histology (H&E, Masson's trichrome), RT-qPCR and Western blot for TGF-β1, TβRI, Smad3, P-Smad3, Col I\",\n      \"journal\": \"Histology and histopathology\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single knockdown approach, in vivo model, no direct binding or reconstitution of TGF-β/Smad pathway\",\n      \"pmids\": [\"30561754\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"Progranulin (PGRN/GRN) is a secreted glycoprotein that functions as a lysosomal and extracellular growth/survival factor: in lysosomes, PGRN-derived granulins maintain bis(monoacylglycero)phosphate (BMP) levels required for ganglioside and sphingolipid catabolism, and PGRN deficiency causes progressive lysosomal dysfunction (gangliosidosis, lipofuscinosis, impaired proteolysis and lipolysis); extracellularly, PGRN acts as an autocrine/paracrine growth factor that signals through cell-surface receptors (~120 kDa species) to activate MAPK/ERK and PI3K/AKT, regulates cell cycle entry via cyclin D1/CDK4, mediates estrogen-dependent proliferation in breast cancer, and in neurons suppresses Gas6-Tyro3-PKCα signaling to prevent tau phosphorylation at Ser203 and synaptic loss; PGRN also suppresses innate immune responses by binding NEMO (via its CDE granulin domains) and recruiting A20 to deubiquitinate K63-polyubiquitin chains on NEMO, thereby dampening NF-κB and IRF3-dependent interferon production, and it promotes anti-inflammatory macrophage (M2) polarization through direct TNFR2 binding; loss-of-function mutations cause haploinsufficiency, lysosomal storage disease (CLN11 when homozygous), frontotemporal dementia with TDP-43 pathology, and secondary defects including Wnt5a/CaMKII/ERK dysregulation, parkin downregulation, and astroglial toxicity driving synaptic degeneration.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"Progranulin (GRN/PGRN) is a secreted glycoprotein with a dual life as a lysosomal cofactor and an extracellular growth/immunomodulatory factor [#0, #6]. In the endolysosomal compartment, PGRN is a pH-dependent interactor of the phospholipid bis(monoacylglycero)phosphate (BMP), and its loss causes global BMP deficiency that cripples sphingolipid catabolism—producing ganglioside and glucosylsphingosine accumulation despite intact catabolic enzymes—and impairs proteolysis, lipolysis, and redox homeostasis [#6, #7]. This lysosomal failure manifests in vivo as defective microglial clearance of myelin debris downstream of cathepsin D, with PGRN acting genetically upstream of cathepsin D-dependent clearance and interacting with TMEM106B such that combined loss produces accelerated lysosomal vacuolation and neuronal loss [#8, #9]. PGRN deficiency also functions as a disease modifier of glucocerebrosidase (GBA1), exacerbating Gaucher- and Parkinson-like neuropathology [#21]. Loss of PGRN drives frontotemporal dementia with TDP-43 pathology through multiple effector arms: disinhibited Gas6-Tyro3 signaling activates PKC\\u03b1 to phosphorylate tau at Ser203 and cause dendritic spine loss [#10], PGRN-deficient astrocytes acquire a reactive transcriptional state (GJA1/AQP4/APOE up, SLC1A2 down) that directly induces synaptic degeneration and TDP-43 proteinopathy [#11], and patient cells show noncanonical Wnt5a/CaMKII/ERK dysregulation and parkin downregulation [#17, #25]. Extracellularly, PGRN binds cell-surface receptors and acts as an autocrine mitogen, mediating estrogen-dependent proliferation and tumorigenesis via cyclin D1/CDK4 and MAPK activation [#0, #1, #4]. As an immune regulator, PGRN dampens type I interferon production by binding NF-\\u03baB essential modulator (NEMO) through its granulin CDE domains and recruiting A20 to deubiquitinate K63-linked chains on NEMO [#12], and it promotes anti-inflammatory M2 macrophage polarization through direct TNFR2 binding [#13, #14]. PGRN levels are controlled post-transcriptionally by TMEM106B and by miR-29b binding within the GRN 3' UTR, the latter being a therapeutic target for translational upregulation [#5, #20]. Haploinsufficiency from loss-of-function GRN mutations underlies frontotemporal dementia with TDP-43 pathology [#17, #18].\",\n  \"teleology\": [\n    {\n      \"year\": 1998,\n      \"claim\": \"Established that PGRN is a secreted autocrine growth factor whose expression is required for tumorigenicity and that it engages specific cell-surface receptors, defining its extracellular signaling identity.\",\n      \"evidence\": \"Antisense inhibition with in vivo tumor formation in syngeneic mice; radiolabeled ligand binding with Scatchard analysis and crosslinking on epithelial and fibroblast cells\",\n      \"pmids\": [\"9826678\", \"10760271\", \"9571191\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"The molecular identity of the ~120 kDa crosslinked receptor species was not determined\", \"No reciprocal validation of receptor binding partners\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Defined the downstream mitogenic mechanism by showing PGRN mediates estrogen-driven proliferation via cyclin D1 induction and MAP kinase activation, linking it to hormone-dependent breast cancer growth.\",\n      \"evidence\": \"Neutralizing antibody, antisense, and overexpression in MCF-7 cells with MAP kinase and cyclin D1 readouts\",\n      \"pmids\": [\"11134521\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Receptor mediating the estrogen-PGRN-cyclin D1 axis not identified\", \"Did not address PGRN's lysosomal/neuronal roles\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Generalized PGRN's proliferative role to ovarian cancer and placed it upstream of cell-cycle entry (cyclin D1/CDK4) and matrix remodeling (MMP-2/MMP-9, VEGF), connecting mitogenesis to invasion.\",\n      \"evidence\": \"Antisense loss-of-function in ovarian cancer cells with proliferation, invasion, and zymography readouts; overexpression with MMP-9/VEGF assays\",\n      \"pmids\": [\"17261172\", \"15117809\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism linking PGRN to MMP/VEGF transcription unresolved\", \"Single-lab functional data\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Identified TMEM106B as a post-transcriptional modulator of circulating PGRN levels, introducing a genetic axis governing PGRN dosage relevant to neurodegeneration risk.\",\n      \"evidence\": \"Genetic association with plasma PGRN ELISA and inverse mRNA correlation in peripheral blood cohorts\",\n      \"pmids\": [\"21178100\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Observational correlation without direct mechanistic experiment\", \"Did not define the molecular mode of TMEM106B regulation\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Connected PGRN haploinsufficiency in FTLD patient cells to aberrant cell cycle re-entry and noncanonical Wnt5a/CaMKII/ERK signaling, offering candidate effectors of neuronal dysfunction.\",\n      \"evidence\": \"FTLD-TDP patient lymphoblasts and SH-SY5Y knockdown with cell cycle analysis, CDK6/phospho-Rb blots, Wnt5a/CaMKII/ERK readouts, conditioned medium rescue\",\n      \"pmids\": [\"24139281\", \"21232819\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Link from PGRN loss to CDK6 via TDP-43 partially inferred\", \"Patient-cell findings from single lab\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Defined PGRN as an anti-inflammatory mediator acting through IL-10- and TNFR2-dependent pathways in colitis, establishing its protective immunoregulatory function in vivo.\",\n      \"evidence\": \"PGRN-/-, IL-10-/-, TNFR2-/- mice in DSS/TNBS colitis with recombinant PGRN rescue and bone marrow chimeras\",\n      \"pmids\": [\"25387791\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not directly demonstrate PGRN-TNFR2 physical binding (resolved later)\", \"Cell type executing protection not fully resolved\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Showed that excess PGRN impairs hepatic and adipose insulin sensitivity through TNFR1/NF-\\u03baB and PERK-eIF2\\u03b1 ER stress signaling, revealing a context-dependent metabolic role distinct from its anti-inflammatory actions.\",\n      \"evidence\": \"PGRN treatment of mice with TNFR1 blocking peptide/siRNA, PERK inhibitor, and chemical chaperone PBA, plus insulin/autophagy/ER stress readouts\",\n      \"pmids\": [\"25664864\", \"26039714\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Reconciliation with PGRN's protective TNFR2 signaling not addressed\", \"Single-lab pharmacological epistasis\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Identified a specific neurodegenerative mechanism whereby PGRN reduction disinhibits Gas6-Tyro3 signaling, activating PKC\\u03b1 to phosphorylate tau at Ser203 and drive spine loss, providing a druggable pathway.\",\n      \"evidence\": \"PGRN-R504X knock-in mice, phosphoproteomics, PKC\\u03b1 kinase assay, pharmacological and siRNA rescue of spine loss and cognition\",\n      \"pmids\": [\"29382817\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How PGRN normally restrains Gas6-Tyro3 binding mechanistically unresolved\", \"Relationship to TDP-43 pathology not directly tested\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Resolved the molecular mechanism of PGRN's interferon suppression by showing direct NEMO binding via granulin CDE domains and A20 recruitment to deubiquitinate K63 chains on NEMO at K264.\",\n      \"evidence\": \"Reciprocal Co-IP, domain mapping, deubiquitination assays, PGRN-deficient mice, and neutralizing antibody with type I IFN quantification\",\n      \"pmids\": [\"31585000\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Subcellular site of PGRN-NEMO interaction not defined\", \"Stoichiometry of the PGRN-NEMO-A20 assembly unknown\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Reframed PGRN as a lysosomal cofactor by identifying pH-dependent BMP binding, with deficiency causing global BMP loss, sphingolipid storage, microglial myelin-clearance failure, and TMEM106B genetic interaction—unifying its neurodegenerative phenotypes around lysosomal dysfunction.\",\n      \"evidence\": \"Grn-/- mice, lipidomics, pH-dependent binding assays, iPSC-microglia, PTV:PGRN replacement, Ctsd/Grn and Tmem106b/Pgrn double-KO epistasis, EM\",\n      \"pmids\": [\"34450028\", \"34433069\", \"32852886\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"The structural basis of granulin-BMP interaction not resolved\", \"How BMP maintenance mechanistically couples to enzyme function unclear\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Extended the lysosomal model by demonstrating PGRN-dependent BMP maintenance is required for ganglioside catabolism and that PGRN modifies glucocerebrosidase function in vivo, linking PGRN to multiple sphingolipidoses.\",\n      \"evidence\": \"Ganglioside mass spectrometry and enzyme assays in human/mouse PGRN-deficient tissue; Grn/Gba1 double-mutant mice with ND7 peptide rescue\",\n      \"pmids\": [\"36207292\", \"36574647\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct biochemical reconstitution of granulin enhancement of catabolism not shown\", \"GBA1 modifier mechanism in part inferred\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Demonstrated a non-cell-autonomous neurodegenerative mechanism in which PGRN-deficient reactive astrocytes directly induce synaptic degeneration and TDP-43 proteinopathy, identifying astrocytes as drivers rather than bystanders.\",\n      \"evidence\": \"Single-nucleus RNA-seq in Grn-/- mice and FTD-GRN tissue, astrocyte-neuron cocultures, and iPSC-astrocyte organoid transplantation\",\n      \"pmids\": [\"36602862\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Astrocyte-secreted factor mediating synaptic toxicity not identified\", \"Interplay with microglial lysosomal defects not resolved\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Confirmed direct PGRN-TNFR2 binding driving M2 macrophage polarization and revealed a PGRN-EGFR axis recruiting macrophages in interferon-driven liver pathology, broadening PGRN's immunoreceptor repertoire.\",\n      \"evidence\": \"Co-IP and TNFR2 neutralizing antibody with M2 markers; liver-specific Adar KO mice with PGRN depletion and EGFR+ macrophage profiling\",\n      \"pmids\": [\"38689292\", \"38935501\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single-lab Co-IP for TNFR2 without reciprocal/structural validation\", \"Whether PGRN binds EGFR directly not established\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Established miR-29b-mediated translational repression of GRN as a therapeutically actionable lever, with steric-block ASOs raising progranulin protein without changing mRNA.\",\n      \"evidence\": \"ASO screen, FRET binding competition, polysome profiling, iPSC-neurons, and humanized GRN mouse model\",\n      \"pmids\": [\"37981208\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Endogenous physiological regulation of miR-29b on GRN not characterized\", \"Other 3' UTR regulators not surveyed\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The identity and signaling logic of the cell-surface PGRN receptor(s) mediating its extracellular growth-factor activity, and how the lysosomal BMP-cofactor role mechanistically couples to the extracellular receptor signaling, remain unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"The ~120 kDa receptor species remains molecularly unidentified\", \"No unified model linking lysosomal granulin function to extracellular MAPK/PI3K signaling\", \"Structural basis of granulin domain-specific functions not determined\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0008289\", \"supporting_discovery_ids\": [6]},\n      {\"term_id\": \"GO:0048018\", \"supporting_discovery_ids\": [0, 1, 2]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [12, 13, 14]},\n      {\"term_id\": \"GO:0060089\", \"supporting_discovery_ids\": [12, 14]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005764\", \"supporting_discovery_ids\": [6, 7, 8]},\n      {\"term_id\": \"GO:0005576\", \"supporting_discovery_ids\": [0, 1, 2]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [12, 13, 14]},\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [6, 7]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [0, 10, 17]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [8, 9, 11]},\n      {\"term_id\": \"R-HSA-1640170\", \"supporting_discovery_ids\": [0, 4, 18]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"TMEM106B\", \"NEMO/IKBKG\", \"A20/TNFAIP3\", \"TNFR2/TNFRSF1B\", \"TNFR1/TNFRSF1A\", \"FAM135B\", \"Tyro3\", \"GBA1\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":9,"faith_total":9,"faith_pct":100.0}}