{"gene":"GDPD5","run_date":"2026-06-10T01:55:21","timeline":{"discoveries":[{"year":2005,"finding":"GDE2 (GDPD5) is a six-transmembrane protein that is necessary and sufficient to drive spinal motor neuron differentiation in vivo; a single amino acid mutation in the extracellular catalytic domain abolishes protein function, demonstrating that glycerophosphodiester metabolism in the extracellular domain is required.","method":"In vivo gain- and loss-of-function experiments in chick and mouse spinal cord; active-site mutagenesis","journal":"Science","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean in vivo KO and overexpression with specific mutagenesis showing catalytic domain requirement; replicated across multiple subsequent studies","pmids":["16195461"],"is_preprint":false},{"year":2008,"finding":"GDPD5 functions as a glycerophosphocholine phosphodiesterase (GPC-PDE) that degrades GPC to glycerol-3-phosphate and choline; recombinant GDPD5 immunoprecipitated from HEK293 cells degrades GPC in vitro, and siRNA knockdown increases cellular GPC levels, while overexpression decreases GPC.","method":"In vitro enzymatic assay with immunoprecipitated recombinant protein; siRNA knockdown; overexpression in IMCD-3 cells","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — in vitro activity assay combined with orthogonal siRNA and overexpression experiments confirming GPC-PDE function","pmids":["18667693"],"is_preprint":false},{"year":2009,"finding":"Peroxiredoxin 1 (Prdx1) interacts with GDE2 and activates it by reducing an intramolecular disulfide bond bridging the intracellular N- and C-terminal domains; GDE2 variants incapable of disulfide bond formation become constitutively active and independent of Prdx1.","method":"Co-immunoprecipitation; disulfide bond mutagenesis; loss-of-function genetics (Prdx1 KO mice); motor neuron differentiation assays","journal":"Cell","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — reciprocal co-IP, mutagenesis of disulfide bond, in vivo KO phenotype, multiple orthogonal methods in one study","pmids":["19766572"],"is_preprint":false},{"year":2011,"finding":"GDE2, expressed in postmitotic motor neurons, induces motor neuron generation through a non-cell-autonomous mechanism: its extracellular glycerophosphodiester phosphodiesterase activity inhibits Notch signaling in adjacent motor neuron progenitors, controlling subtype-specific motor neuron production.","method":"Gde2 knockout mouse analysis; histology; epistasis with Notch pathway","journal":"Neuron","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vivo KO with defined cellular phenotype, pathway placement via Notch epistasis, replicated across multiple studies","pmids":["21943603"],"is_preprint":false},{"year":2013,"finding":"GDE2 cleaves GPI anchors (unlike classical GDPDs which cleave glycerophosphodiesters) and uses this GPI-anchor cleavage activity to release RECK from the membrane; RECK release disinhibits ADAM protease-dependent shedding of Delta-like 1 (Dll1), leading to Notch inactivation and neurogenesis.","method":"GPI-anchor cleavage assay; biochemical fractionation; epistasis with RECK, ADAM proteases, and Dll1-Notch pathway; active-site mutagenesis","journal":"Science","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — novel enzymatic activity (GPI-anchor cleavage) demonstrated biochemically with pathway epistasis and mutagenesis confirming catalytic requirement","pmids":["23329048"],"is_preprint":false},{"year":2013,"finding":"High NaCl and high urea inhibit GDPD5 GPC-PDE activity via at least three post-translational modifications: (i) formation of a disulfide bond between C25 and C571 (promoted by ROS); (ii) dephosphorylation of T587 (constitutively phosphorylated, and dephosphorylation reduces activity); (iii) an additional modification mediated by CDK1. These PTMs collectively increase cellular GPC levels.","method":"Site-directed mutagenesis (C25S/C571S, T587A); CDK1 pharmacological inhibition; antioxidant treatment; in vitro GPC-PDE activity assays; mass spectrometry of PTMs","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro enzymatic assay with mutagenesis of specific residues, pharmacological epistasis, single lab but multiple orthogonal methods","pmids":["23589856"],"is_preprint":false},{"year":2015,"finding":"Prdx4, an ER-resident H2O2-metabolizing enzyme, oxidizes two cysteine residues within the GDE2 enzymatic domain via Prdx4 dimers generated by H2O2 metabolism; this oxidation blocks GDE2 trafficking to the plasma membrane and prevents its neurogenic function.","method":"Prdx4 knockout mouse; biochemical oxidation assays; subcellular fractionation/trafficking assays; motor neuron differentiation readouts; cysteine mutagenesis","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 / Moderate — in vivo KO with defined cellular phenotype, direct biochemical oxidation assay, localization data linked to function, multiple orthogonal methods in one study","pmids":["25943695"],"is_preprint":false},{"year":2010,"finding":"GDP-bound Gαi2 interacts with GDE2 in motor neuron progenitors; disruption of the GDE2/Gαi2 complex in vivo causes motor neuron deficits analogous to Gαi2 ablation, indicating Gαi2 regulates motor neuron differentiation in part through this interaction.","method":"Co-immunoprecipitation; in vivo dominant-negative and knockdown in chick spinal cord; Gαi2 KO mice; motor neuron counting","journal":"Developmental biology","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — co-IP identifying interaction, in vivo disruption of complex with phenotypic readout, single lab","pmids":["20197066"],"is_preprint":false},{"year":2012,"finding":"Gde2 controls the timing of cortical progenitor cell-cycle exit; in Gde2 knockout mice, cortical progenitors fail to exit the cell cycle on time, correlating with elevated Notch signaling, causing deficits in deep-layer neurons and excess superficial-layer neurons.","method":"Gde2 knockout mouse; BrdU birthdating; immunohistochemistry; Notch signaling assays","journal":"Development","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo KO with defined layering phenotype and Notch pathway correlation, single lab","pmids":["22951639"],"is_preprint":false},{"year":2016,"finding":"GDE2 induces neuroblastoma cell differentiation and suppresses cell motility by cleaving (in cis) the GPI-anchored glypican-6 (GPC6) and releasing it from the membrane; a single point mutation in the ectodomain abolishing catalytic activity also abolishes GDE2 differentiation function, and GDE2 alters the Rac-RhoA activity balance.","method":"GPI-anchor cleavage assay; active-site mutagenesis; GPC6 surface-release experiments; Rac/RhoA activity assays; neuroblastoma cell differentiation assays","journal":"Cancer cell","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — biochemical GPI-cleavage assay, mutagenesis, Rho GTPase activity readout, specific substrate identified, single lab with multiple orthogonal methods","pmids":["27693046"],"is_preprint":false},{"year":2017,"finding":"Adult mice lacking GDE2 develop progressive neuronal degeneration; conditional deletion of GDE2 after embryonic neurogenesis still causes degeneration, showing the survival function is distinct from the differentiation function. Unbiased screening identifies impaired processing of GPI-anchored Glypican 4 and 6 as molecular correlates.","method":"Constitutive and conditional (postnatal) Gde2 KO mouse; histology; electrophysiology; behavioral assays; proteomics screen for GPI-anchored substrates","journal":"Molecular neurodegeneration","confidence":"High","confidence_rationale":"Tier 2 / Strong — temporal conditional KO dissecting differentiation vs survival functions, multiple phenotypic readouts, substrate identification, replication of core finding in subsequent studies","pmids":["28103900"],"is_preprint":false},{"year":2020,"finding":"GDE2 expressed in neurons activates canonical Wnt signaling, leading to secretion of soluble factors (including phosphacan) that promote oligodendrocyte maturation; Gde2KO neurons show reduced Wnt signaling and genetic activation of Wnt in Gde2KO neurons rescues oligodendrocyte maturation both in vivo and in vitro.","method":"Global and neuron-specific Gde2 KO mice; conditioned medium experiments; Wnt signaling reporter assays; genetic rescue with constitutively active Wnt components; phosphacan quantification","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 2 / Moderate — cell-type-specific KO, conditioned medium rescue, genetic epistasis with Wnt pathway, multiple orthogonal approaches in single study","pmids":["32375055"],"is_preprint":false},{"year":2020,"finding":"GDE2 expressed in oligodendrocytes cell-autonomously slows the pace of oligodendrocyte maturation; oligodendrocyte-specific Gde2 KO mice show accelerated oligodendrocyte maturation and increased myelination, phenocopied in purified primary oligodendrocyte cultures.","method":"Oligodendrocyte-specific Cre-lox KO (O-Gde2KO); immunohistochemistry for myelin proteins; primary oligodendrocyte cultures","journal":"Developmental dynamics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — cell-type-specific KO with in vivo and in vitro phenotypic concordance, single lab","pmids":["33095500"],"is_preprint":false},{"year":2020,"finding":"GDE2 trafficking is regulated by C-terminal tail sequences that control constitutive endocytosis and recycling; a C-terminal leucine residue in a unique motif is essential for GDE2 internalization, and a truncation mutant with aberrant recycling fails to cleave GPI-anchored GPC6 and is non-functional, whereas a consecutive deletion causing surface retention gains function.","method":"Live-cell imaging; FRAP; C-terminal deletion/truncation mutagenesis; GPC6 cleavage assay; neuronal differentiation assays","journal":"Journal of cell science","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — direct localization by live imaging and FRAP tied to functional GPC6 cleavage assay and differentiation readout, structure-function mutagenesis, single lab with multiple orthogonal methods","pmids":["31932507"],"is_preprint":false},{"year":2021,"finding":"GDE2 stimulates ADAM10 α-secretase cleavage of amyloid precursor protein (APP) by shedding and inactivating the GPI-anchored RECK protein, a known ADAM10 inhibitor; genetic ablation of GDE2 elevates membrane-bound RECK, reduces sAPPα generation, increases Aβ, and causes synaptic protein loss. In Alzheimer's disease tissue, GDE2 is abnormally sequestered intracellularly and membrane RECK is elevated.","method":"Gde2 KO mouse; RECK genetic reduction rescue experiments; APP processing biochemical assays (sAPPα, Aβ measurements); human AD postmortem tissue analysis; synaptic protein quantification","journal":"Science translational medicine","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vivo KO with biochemical substrate (APP processing) readout, genetic rescue by RECK reduction, human tissue validation, multiple orthogonal methods","pmids":["33731436"],"is_preprint":false},{"year":2022,"finding":"In ALS patient post-mortem tissue, total GDE2 protein levels are normal but membrane GDE2 is substantially reduced, with GDE2 aberrantly accumulating in intracellular compartments of motor cortex neurons; haplogenetic reduction of GDE2 exacerbates motor neuron degeneration in SOD1G93A mice; tandem-mass-tag MS reveals reduced GPI-anchored protein release into CSF of ALS patients.","method":"Human ALS postmortem tissue immunohistochemistry and fractionation; SOD1G93A mouse genetic interaction; tandem-mass-tag mass spectrometry of CSF","journal":"Acta neuropathologica communications","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — subcellular fractionation tied to functional implication, in vivo genetic interaction, MS proteomics of CSF, single lab","pmids":["35550203"],"is_preprint":false},{"year":2024,"finding":"GDE2 regulates the number and molecular composition of small extracellular vesicles (sEVs) released from neuronal cell surfaces via its GPI-anchor cleavage activity; proteomic profiling identifies at least two distinct GDE2-dependent sEV populations—one containing GDE2 itself and one harboring CD9 and BSG—enriched in cytoskeletal, actin-remodeling, synaptic, and redox proteins.","method":"Gde2 KO neurons; sEV isolation and quantification; proteomic profiling (mass spectrometry); functional GPI-cleavage activity assays","journal":"Cells","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — KO with proteomics and sEV quantification, multiple EV populations defined, single lab with single study","pmids":["39272985"],"is_preprint":false},{"year":2024,"finding":"PRKDC recruits and binds GDE2; this interaction enhances GNAS protein stability, which activates AKT phosphorylation and confers doxorubicin resistance in osteosarcoma.","method":"CRISPR kinome screen; co-immunoprecipitation; protein stability assays; phospho-AKT measurements; xenograft and organoid rescue experiments","journal":"Cancer research","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — co-IP establishing PRKDC-GDE2 interaction, in vivo xenograft rescue, multiple functional readouts, single lab","pmids":["38900943"],"is_preprint":false},{"year":2025,"finding":"GDE2 regulates hippocampal CA1 synaptic morphology and function; Gde2KO mice show increased dendritic complexity, excess mushroom spines, increased mEPSC frequency, impaired paired-pulse facilitation, and disrupted NMDAR-mediated LTD. Mechanistically, abnormal activation of the PI3K-AKT-GSK3 signaling pathway in Gde2KO hippocampus underlies LTD impairment, and PI3K inhibition restores LTD to WT levels.","method":"Gde2 KO mouse; electrophysiology (mEPSC, PPF, LTD); dendritic morphology analysis; PI3K-AKT-GSK3 pathway biochemistry; pharmacological PI3K inhibition rescue","journal":"eNeuro","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo KO with electrophysiology, pathway biochemistry, and pharmacological rescue, single lab","pmids":["40634123"],"is_preprint":false},{"year":2025,"finding":"GDE2 inhibits excessive neuronal Wnt activation by regulating the surface expression of GPI-anchored Glypican 6 (GPC6); elevated GPC6 surface expression potentiates neuronal Wnt activation, causing nuclear pore complex disruption, altered Ran-dependent nucleocytoplasmic trafficking, and TDP-43 mislocalization; genetic reduction of GPC6 in Gde2KO mice rescues all these defects.","method":"In vivo mouse genetics (Gde2KO, GPC6 genetic reduction rescue); nuclear pore complex integrity assays; Ran-NCT assays; TDP-43 localization immunohistochemistry; Wnt signaling reporters","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo genetic epistasis with multiple cellular readouts, preprint not yet peer-reviewed, single lab","pmids":["bio_10.1101_2025.09.24.678385"],"is_preprint":true}],"current_model":"GDPD5/GDE2 is a six-transmembrane plasma-membrane enzyme with dual substrate specificity—it cleaves GPI-anchored proteins (including RECK and glypicans) and degrades glycerophosphocholine (GPC); its activity is regulated by Prdx1-mediated reduction of an inhibitory intramolecular disulfide bond (C25-C571), by Prdx4-mediated oxidative trapping in the ER, by CDK1-dependent phosphorylation of T587, and by sequence-dependent endocytic trafficking; by releasing RECK from the neuronal surface, GDE2 disinhibits ADAM10/ADAM protease activity to shed Dll1 and suppress Notch signaling, driving neuronal differentiation; postnatally it controls neuronal survival, oligodendrocyte maturation, hippocampal synaptic plasticity (via PI3K-AKT-GSK3), and APP processing (by preventing RECK-mediated ADAM10 inhibition), and its intracellular mislocalization in ALS and Alzheimer's disease impairs these protective GPI-anchor cleavage pathways."},"narrative":{"mechanistic_narrative":"GDPD5 (GDE2) is a six-transmembrane plasma-membrane enzyme that drives neuronal differentiation and maintains neuronal survival through extracellular cleavage of GPI-anchored proteins [PMID:16195461, PMID:23329048, PMID:28103900]. Although originally defined as a glycerophosphocholine phosphodiesterase that degrades GPC to glycerol-3-phosphate and choline [PMID:18667693], its neurogenic activity depends on a distinct GPI-anchor cleavage activity that releases substrates such as RECK and the glypicans GPC4/GPC6 from the cell surface [PMID:23329048, PMID:27693046, PMID:28103900]. By shedding GPI-anchored RECK, GDE2 disinhibits ADAM protease-dependent shedding of Delta-like 1, inactivating Notch signaling to promote subtype-specific motor neuron and cortical neuron production [PMID:21943603, PMID:23329048, PMID:22951639]. GDE2 catalytic activity is gated by redox- and phosphorylation-dependent control: Prdx1 activates the enzyme by reducing an inhibitory intramolecular disulfide bridging its N- and C-terminal domains [PMID:19766572], Prdx4-mediated oxidation of cysteines in the catalytic domain traps GDE2 in the ER and blocks surface trafficking [PMID:25943695], and a C25-C571 disulfide, T587 dephosphorylation, and a CDK1-dependent modification inhibit GPC-PDE activity [PMID:23589856]; C-terminal tail motifs further govern constitutive endocytosis and recycling required for productive substrate cleavage [PMID:31932507]. Postnatally GDE2 controls neuronal survival [PMID:28103900], oligodendrocyte maturation through neuronal Wnt activation and via cell-autonomous action in oligodendrocytes [PMID:32375055, PMID:33095500], hippocampal synaptic plasticity through restraint of PI3K-AKT-GSK3 signaling [PMID:40634123], and amyloid precursor protein processing by relieving RECK-mediated ADAM10 inhibition to favor non-amyloidogenic sAPPα generation [PMID:33731436]. Intracellular mislocalization of GDE2 with retained membrane RECK is observed in Alzheimer's disease tissue, and reduced membrane GDE2 with impaired GPI-anchored protein release occurs in ALS, where GDE2 reduction exacerbates motor neuron degeneration [PMID:33731436, PMID:35550203].","teleology":[{"year":2005,"claim":"Established that GDE2 is a transmembrane protein whose extracellular catalytic activity is necessary and sufficient to drive spinal motor neuron differentiation, defining it as an enzymatic regulator of neurogenesis.","evidence":"In vivo gain- and loss-of-function plus active-site mutagenesis in chick and mouse spinal cord","pmids":["16195461"],"confidence":"High","gaps":["Did not identify the physiological substrate","Mechanism downstream of catalysis unresolved"]},{"year":2008,"claim":"Assigned a defined enzymatic activity by showing GDPD5 is a glycerophosphocholine phosphodiesterase, linking it to choline/phospholipid metabolism.","evidence":"In vitro enzymatic assay on immunoprecipitated protein with siRNA and overexpression in IMCD-3 cells","pmids":["18667693"],"confidence":"High","gaps":["Did not connect GPC-PDE activity to the neuronal differentiation function","Did not test GPI-anchored substrates"]},{"year":2009,"claim":"Revealed redox-based activation, showing Prdx1 reduces an inhibitory intramolecular disulfide to switch GDE2 on, identifying the first regulatory mechanism of the enzyme.","evidence":"Reciprocal co-IP, disulfide-bond mutagenesis, Prdx1 KO mice, and differentiation assays","pmids":["19766572"],"confidence":"High","gaps":["Did not define the catalytic substrate driving differentiation","Upstream control of Prdx1-GDE2 coupling unknown"]},{"year":2010,"claim":"Placed GDE2 in a heterotrimeric G-protein context by identifying GDP-Gαi2 as an interacting partner that regulates motor neuron differentiation.","evidence":"Co-IP and in vivo complex disruption with Gαi2 KO mice and motor neuron counting","pmids":["20197066"],"confidence":"Medium","gaps":["Mechanism by which Gαi2 modulates GDE2 catalysis unclear","Single lab"]},{"year":2013,"claim":"Resolved how GDE2 controls neurogenesis by demonstrating it cleaves GPI anchors to release RECK, disinhibiting ADAM-dependent Dll1 shedding and Notch inactivation — reframing the enzyme as a GPI-anchor protease.","evidence":"GPI-anchor cleavage assays, fractionation, active-site mutagenesis, and epistasis with RECK/ADAM/Dll1-Notch","pmids":["23329048"],"confidence":"High","gaps":["Did not enumerate the full GPI-anchored substrate repertoire","Relationship between GPI-cleavage and GPC-PDE activities unresolved"]},{"year":2013,"claim":"Mapped post-translational control of GPC-PDE activity, identifying a C25-C571 disulfide, T587 phosphorylation, and a CDK1-dependent modification as osmotic stress-responsive regulatory switches.","evidence":"Site-directed mutagenesis, CDK1 inhibition, antioxidant treatment, MS of PTMs, and in vitro activity assays","pmids":["23589856"],"confidence":"High","gaps":["Whether these PTMs also gate GPI-anchor cleavage not tested","Kinase/phosphatase identities for T587 not all defined"]},{"year":2012,"claim":"Extended GDE2 function beyond motor neurons by showing it times cortical progenitor cell-cycle exit via Notch, broadening its developmental role.","evidence":"Gde2 KO mouse with BrdU birthdating, immunohistochemistry, and Notch readouts","pmids":["22951639"],"confidence":"Medium","gaps":["Substrate driving cortical Notch suppression not identified here","Single lab"]},{"year":2015,"claim":"Identified ER-based trafficking control, showing Prdx4 oxidizes GDE2 catalytic cysteines to block its surface delivery and neurogenic function.","evidence":"Prdx4 KO mouse, biochemical oxidation assays, trafficking fractionation, and cysteine mutagenesis","pmids":["25943695"],"confidence":"High","gaps":["How oxidation status is reversed at the membrane unclear","Relationship to Prdx1 activation step not integrated"]},{"year":2016,"claim":"Demonstrated GDE2 acts in cancer by cleaving GPI-anchored glypican-6 to drive neuroblastoma differentiation and shift Rac/RhoA balance, generalizing the GPI-cleavage mechanism to glypican substrates.","evidence":"GPI-cleavage and GPC6 release assays, active-site mutagenesis, Rac/RhoA activity, and differentiation assays","pmids":["27693046"],"confidence":"High","gaps":["Link between glypican release and cytoskeletal GTPase output not fully mechanistic","Single lab"]},{"year":2017,"claim":"Separated developmental from maintenance roles by showing postnatal GDE2 loss causes progressive neuronal degeneration with impaired glypican-4/6 processing as molecular correlates.","evidence":"Constitutive and conditional Gde2 KO mice with histology, electrophysiology, behavior, and GPI-anchored substrate proteomics","pmids":["28103900"],"confidence":"High","gaps":["Causal substrate for survival defect not isolated","Cell-autonomous vs non-autonomous survival mechanism not resolved"]},{"year":2020,"claim":"Connected neuronal GDE2 to glial development, showing it activates neuronal Wnt to secrete factors (including phosphacan) that promote oligodendrocyte maturation.","evidence":"Global and neuron-specific Gde2 KO, conditioned medium, Wnt reporters, and genetic Wnt rescue","pmids":["32375055"],"confidence":"High","gaps":["GPI substrate linking GDE2 catalysis to Wnt activation not defined here","Identity of all secreted pro-maturation factors incomplete"]},{"year":2020,"claim":"Showed a cell-autonomous, opposite-direction role in oligodendrocytes where GDE2 slows maturation, indicating cell-type-specific outputs of the same enzyme.","evidence":"Oligodendrocyte-specific Cre-lox KO with myelin immunohistochemistry and primary cultures","pmids":["33095500"],"confidence":"Medium","gaps":["Substrate in oligodendrocytes not identified","Single lab"]},{"year":2020,"claim":"Defined trafficking determinants, showing C-terminal motifs controlling endocytosis/recycling are required for GPC6 cleavage and function.","evidence":"Live-cell imaging, FRAP, C-terminal mutagenesis, GPC6 cleavage, and differentiation assays","pmids":["31932507"],"confidence":"High","gaps":["Endocytic adaptors recognizing the motif not identified","Single lab"]},{"year":2021,"claim":"Linked GDE2 to Alzheimer's disease by showing it promotes ADAM10 α-secretase APP processing through RECK shedding, with intracellular GDE2 sequestration and elevated membrane RECK in AD tissue.","evidence":"Gde2 KO mouse, RECK genetic reduction rescue, APP processing biochemistry, and human AD postmortem analysis","pmids":["33731436"],"confidence":"High","gaps":["Cause of GDE2 intracellular sequestration in AD unknown","Therapeutic reversibility not addressed"]},{"year":2022,"claim":"Implicated GDE2 mislocalization in ALS, showing reduced membrane GDE2 and impaired GPI-anchored protein release, with GDE2 reduction worsening SOD1G93A degeneration.","evidence":"Human ALS postmortem fractionation/IHC, SOD1G93A genetic interaction, and TMT-MS of CSF","pmids":["35550203"],"confidence":"Medium","gaps":["Mechanism driving membrane loss/intracellular accumulation unknown","Single lab"]},{"year":2024,"claim":"Revealed a context outside neurons in which PRKDC binds GDE2 to stabilize GNAS, activate AKT, and confer doxorubicin resistance in osteosarcoma.","evidence":"CRISPR kinome screen, co-IP, protein stability assays, phospho-AKT, and xenograft/organoid rescue","pmids":["38900943"],"confidence":"Medium","gaps":["Whether GDE2 catalytic activity is required for this role untested","Single lab"]},{"year":2024,"claim":"Showed GDE2 GPI-anchor cleavage shapes neuronal small extracellular vesicle number and composition, extending its surface-remodeling role to EV biology.","evidence":"Gde2 KO neurons with sEV isolation, quantification, and proteomic profiling","pmids":["39272985"],"confidence":"Medium","gaps":["Functional consequences of altered sEV populations not established","Single study"]},{"year":2025,"claim":"Tied GDE2 to nuclear integrity and TDP-43 homeostasis, showing restraint of GPC6-driven neuronal Wnt prevents nuclear pore disruption and TDP-43 mislocalization.","evidence":"In vivo Gde2KO with GPC6 genetic reduction rescue, NPC and Ran-NCT assays, TDP-43 IHC, and Wnt reporters (preprint)","pmids":["bio_10.1101_2025.09.24.678385"],"confidence":"Medium","gaps":["Preprint not yet peer-reviewed","Direct link between Wnt activation and NPC disruption mechanistically incomplete"]},{"year":2025,"claim":"Established a synaptic plasticity role, showing GDE2 restrains PI3K-AKT-GSK3 signaling required for normal hippocampal CA1 morphology and NMDAR-dependent LTD.","evidence":"Gde2 KO mouse electrophysiology, dendritic morphology, pathway biochemistry, and PI3K inhibition rescue","pmids":["40634123"],"confidence":"Medium","gaps":["GPI substrate upstream of PI3K-AKT-GSK3 not identified","Single lab"]},{"year":null,"claim":"How GDE2's dual GPC-phosphodiesterase and GPI-anchor protease activities are coordinated, and what determines its substrate selection and disease-associated intracellular trapping, remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["Structural basis for dual substrate specificity unknown","Cause of GDE2 mislocalization in ALS/AD undefined","Full GPI-anchored substrate repertoire incomplete"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140098","term_label":"catalytic activity, acting on RNA","supporting_discovery_ids":[1,5]},{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[4,9,10]},{"term_id":"GO:0016787","term_label":"hydrolase activity","supporting_discovery_ids":[1,4]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[0,4,13,15]},{"term_id":"GO:0005783","term_label":"endoplasmic reticulum","supporting_discovery_ids":[6]},{"term_id":"GO:0031410","term_label":"cytoplasmic vesicle","supporting_discovery_ids":[13]}],"pathway":[{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[0,3,8,11]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[4,11,18]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[14,15]},{"term_id":"R-HSA-112316","term_label":"Neuronal System","supporting_discovery_ids":[10,18]}],"complexes":[],"partners":["PRDX1","PRDX4","RECK","GPC6","GNAI2","PRKDC","GNAS"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q8WTR4","full_name":"Glycerophosphodiester phosphodiesterase domain-containing protein 5","aliases":["Glycerophosphocholine phosphodiesterase GDPD5","Glycerophosphodiester phosphodiesterase 2","Phosphoinositide phospholipase C GDPD5"],"length_aa":605,"mass_kda":68.6,"function":"Glycerophosphodiester phosphodiesterase that promotes neurite formation and drives spinal motor neuron differentiation (By similarity). Mediates the cleavage of glycosylphosphatidylinositol (GPI) anchor of target proteins: removes the GPI-anchor of RECK, leading to release RECK from the plasma membrane (By similarity). May contribute to the osmotic regulation of cellular glycerophosphocholine (By similarity)","subcellular_location":"Endomembrane system; Cytoplasm, perinuclear region; Cell projection, growth cone","url":"https://www.uniprot.org/uniprotkb/Q8WTR4/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/GDPD5","classification":"Not Classified","n_dependent_lines":7,"n_total_lines":1208,"dependency_fraction":0.005794701986754967},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/GDPD5","total_profiled":1310},"omim":[{"mim_id":"609632","title":"GLYCEROPHOSPHODIESTER PHOSPHODIESTERASE DOMAIN-CONTAINING PROTEIN 5; GDPD5","url":"https://www.omim.org/entry/609632"},{"mim_id":"176763","title":"PEROXIREDOXIN 1; PRDX1","url":"https://www.omim.org/entry/176763"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Golgi apparatus","reliability":"Approved"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"lymphoid tissue","ntpm":112.9},{"tissue":"retina","ntpm":77.5}],"url":"https://www.proteinatlas.org/search/GDPD5"},"hgnc":{"alias_symbol":["PP1665","GDE2"],"prev_symbol":[]},"alphafold":{"accession":"Q8WTR4","domains":[{"cath_id":"-","chopping":"15-216_497-523","consensus_level":"medium","plddt":92.1664,"start":15,"end":523},{"cath_id":"3.20.20.190","chopping":"234-423","consensus_level":"high","plddt":96.2255,"start":234,"end":423}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8WTR4","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q8WTR4-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q8WTR4-F1-predicted_aligned_error_v6.png","plddt_mean":86.25},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=GDPD5","jax_strain_url":"https://www.jax.org/strain/search?query=GDPD5"},"sequence":{"accession":"Q8WTR4","fasta_url":"https://rest.uniprot.org/uniprotkb/Q8WTR4.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q8WTR4/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8WTR4"}},"corpus_meta":[{"pmid":"23329048","id":"PMC_23329048","title":"GDE2 promotes neurogenesis by glycosylphosphatidylinositol-anchor cleavage of RECK.","date":"2013","source":"Science (New York, N.Y.)","url":"https://pubmed.ncbi.nlm.nih.gov/23329048","citation_count":97,"is_preprint":false},{"pmid":"19766572","id":"PMC_19766572","title":"The antioxidant enzyme Prdx1 controls neuronal differentiation by thiol-redox-dependent activation of GDE2.","date":"2009","source":"Cell","url":"https://pubmed.ncbi.nlm.nih.gov/19766572","citation_count":94,"is_preprint":false},{"pmid":"18667693","id":"PMC_18667693","title":"GDPD5 is a glycerophosphocholine phosphodiesterase that osmotically regulates the osmoprotective organic osmolyte GPC.","date":"2008","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/18667693","citation_count":81,"is_preprint":false},{"pmid":"16195461","id":"PMC_16195461","title":"Transmembrane protein GDE2 induces motor neuron differentiation in 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Containing 5 (GDPD5) in gastric cancer cells.","date":"2022","source":"Bioengineered","url":"https://pubmed.ncbi.nlm.nih.gov/35282764","citation_count":5,"is_preprint":false},{"pmid":"38924469","id":"PMC_38924469","title":"KLF7 promotes neuroblastoma differentiation through the GTPase signaling pathway by upregulating neuroblast differentiation-associated protein AHNAKs and glycerophosphodiesterase GDPD5.","date":"2024","source":"The FEBS journal","url":"https://pubmed.ncbi.nlm.nih.gov/38924469","citation_count":5,"is_preprint":false},{"pmid":"20197066","id":"PMC_20197066","title":"GDP-bound Galphai2 regulates spinal motor neuron differentiation through interaction with GDE2.","date":"2010","source":"Developmental biology","url":"https://pubmed.ncbi.nlm.nih.gov/20197066","citation_count":5,"is_preprint":false},{"pmid":"39272985","id":"PMC_39272985","title":"The Six-Transmembrane Enzyme GDE2 Is Required for the Release of Molecularly Distinct Small Extracellular Vesicles from 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neurons","date":"2025-09-25","source":"bioRxiv","url":"https://doi.org/10.1101/2025.09.24.678385","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":19205,"output_tokens":5239,"usd":0.0681,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":13658,"output_tokens":5590,"usd":0.10402,"stage2_stop_reason":"end_turn"},"total_usd":0.17212,"stage1_batch_id":"msgbatch_01DUPACZi7AAWwuZiUjseQF4","stage2_batch_id":"msgbatch_018yt7chE3f48PEFtDwtj6AE","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2005,\n      \"finding\": \"GDE2 (GDPD5) is a six-transmembrane protein that is necessary and sufficient to drive spinal motor neuron differentiation in vivo; a single amino acid mutation in the extracellular catalytic domain abolishes protein function, demonstrating that glycerophosphodiester metabolism in the extracellular domain is required.\",\n      \"method\": \"In vivo gain- and loss-of-function experiments in chick and mouse spinal cord; active-site mutagenesis\",\n      \"journal\": \"Science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean in vivo KO and overexpression with specific mutagenesis showing catalytic domain requirement; replicated across multiple subsequent studies\",\n      \"pmids\": [\"16195461\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"GDPD5 functions as a glycerophosphocholine phosphodiesterase (GPC-PDE) that degrades GPC to glycerol-3-phosphate and choline; recombinant GDPD5 immunoprecipitated from HEK293 cells degrades GPC in vitro, and siRNA knockdown increases cellular GPC levels, while overexpression decreases GPC.\",\n      \"method\": \"In vitro enzymatic assay with immunoprecipitated recombinant protein; siRNA knockdown; overexpression in IMCD-3 cells\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — in vitro activity assay combined with orthogonal siRNA and overexpression experiments confirming GPC-PDE function\",\n      \"pmids\": [\"18667693\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Peroxiredoxin 1 (Prdx1) interacts with GDE2 and activates it by reducing an intramolecular disulfide bond bridging the intracellular N- and C-terminal domains; GDE2 variants incapable of disulfide bond formation become constitutively active and independent of Prdx1.\",\n      \"method\": \"Co-immunoprecipitation; disulfide bond mutagenesis; loss-of-function genetics (Prdx1 KO mice); motor neuron differentiation assays\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — reciprocal co-IP, mutagenesis of disulfide bond, in vivo KO phenotype, multiple orthogonal methods in one study\",\n      \"pmids\": [\"19766572\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"GDE2, expressed in postmitotic motor neurons, induces motor neuron generation through a non-cell-autonomous mechanism: its extracellular glycerophosphodiester phosphodiesterase activity inhibits Notch signaling in adjacent motor neuron progenitors, controlling subtype-specific motor neuron production.\",\n      \"method\": \"Gde2 knockout mouse analysis; histology; epistasis with Notch pathway\",\n      \"journal\": \"Neuron\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vivo KO with defined cellular phenotype, pathway placement via Notch epistasis, replicated across multiple studies\",\n      \"pmids\": [\"21943603\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"GDE2 cleaves GPI anchors (unlike classical GDPDs which cleave glycerophosphodiesters) and uses this GPI-anchor cleavage activity to release RECK from the membrane; RECK release disinhibits ADAM protease-dependent shedding of Delta-like 1 (Dll1), leading to Notch inactivation and neurogenesis.\",\n      \"method\": \"GPI-anchor cleavage assay; biochemical fractionation; epistasis with RECK, ADAM proteases, and Dll1-Notch pathway; active-site mutagenesis\",\n      \"journal\": \"Science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — novel enzymatic activity (GPI-anchor cleavage) demonstrated biochemically with pathway epistasis and mutagenesis confirming catalytic requirement\",\n      \"pmids\": [\"23329048\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"High NaCl and high urea inhibit GDPD5 GPC-PDE activity via at least three post-translational modifications: (i) formation of a disulfide bond between C25 and C571 (promoted by ROS); (ii) dephosphorylation of T587 (constitutively phosphorylated, and dephosphorylation reduces activity); (iii) an additional modification mediated by CDK1. These PTMs collectively increase cellular GPC levels.\",\n      \"method\": \"Site-directed mutagenesis (C25S/C571S, T587A); CDK1 pharmacological inhibition; antioxidant treatment; in vitro GPC-PDE activity assays; mass spectrometry of PTMs\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro enzymatic assay with mutagenesis of specific residues, pharmacological epistasis, single lab but multiple orthogonal methods\",\n      \"pmids\": [\"23589856\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Prdx4, an ER-resident H2O2-metabolizing enzyme, oxidizes two cysteine residues within the GDE2 enzymatic domain via Prdx4 dimers generated by H2O2 metabolism; this oxidation blocks GDE2 trafficking to the plasma membrane and prevents its neurogenic function.\",\n      \"method\": \"Prdx4 knockout mouse; biochemical oxidation assays; subcellular fractionation/trafficking assays; motor neuron differentiation readouts; cysteine mutagenesis\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo KO with defined cellular phenotype, direct biochemical oxidation assay, localization data linked to function, multiple orthogonal methods in one study\",\n      \"pmids\": [\"25943695\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"GDP-bound Gαi2 interacts with GDE2 in motor neuron progenitors; disruption of the GDE2/Gαi2 complex in vivo causes motor neuron deficits analogous to Gαi2 ablation, indicating Gαi2 regulates motor neuron differentiation in part through this interaction.\",\n      \"method\": \"Co-immunoprecipitation; in vivo dominant-negative and knockdown in chick spinal cord; Gαi2 KO mice; motor neuron counting\",\n      \"journal\": \"Developmental biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — co-IP identifying interaction, in vivo disruption of complex with phenotypic readout, single lab\",\n      \"pmids\": [\"20197066\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Gde2 controls the timing of cortical progenitor cell-cycle exit; in Gde2 knockout mice, cortical progenitors fail to exit the cell cycle on time, correlating with elevated Notch signaling, causing deficits in deep-layer neurons and excess superficial-layer neurons.\",\n      \"method\": \"Gde2 knockout mouse; BrdU birthdating; immunohistochemistry; Notch signaling assays\",\n      \"journal\": \"Development\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo KO with defined layering phenotype and Notch pathway correlation, single lab\",\n      \"pmids\": [\"22951639\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"GDE2 induces neuroblastoma cell differentiation and suppresses cell motility by cleaving (in cis) the GPI-anchored glypican-6 (GPC6) and releasing it from the membrane; a single point mutation in the ectodomain abolishing catalytic activity also abolishes GDE2 differentiation function, and GDE2 alters the Rac-RhoA activity balance.\",\n      \"method\": \"GPI-anchor cleavage assay; active-site mutagenesis; GPC6 surface-release experiments; Rac/RhoA activity assays; neuroblastoma cell differentiation assays\",\n      \"journal\": \"Cancer cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — biochemical GPI-cleavage assay, mutagenesis, Rho GTPase activity readout, specific substrate identified, single lab with multiple orthogonal methods\",\n      \"pmids\": [\"27693046\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Adult mice lacking GDE2 develop progressive neuronal degeneration; conditional deletion of GDE2 after embryonic neurogenesis still causes degeneration, showing the survival function is distinct from the differentiation function. Unbiased screening identifies impaired processing of GPI-anchored Glypican 4 and 6 as molecular correlates.\",\n      \"method\": \"Constitutive and conditional (postnatal) Gde2 KO mouse; histology; electrophysiology; behavioral assays; proteomics screen for GPI-anchored substrates\",\n      \"journal\": \"Molecular neurodegeneration\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — temporal conditional KO dissecting differentiation vs survival functions, multiple phenotypic readouts, substrate identification, replication of core finding in subsequent studies\",\n      \"pmids\": [\"28103900\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"GDE2 expressed in neurons activates canonical Wnt signaling, leading to secretion of soluble factors (including phosphacan) that promote oligodendrocyte maturation; Gde2KO neurons show reduced Wnt signaling and genetic activation of Wnt in Gde2KO neurons rescues oligodendrocyte maturation both in vivo and in vitro.\",\n      \"method\": \"Global and neuron-specific Gde2 KO mice; conditioned medium experiments; Wnt signaling reporter assays; genetic rescue with constitutively active Wnt components; phosphacan quantification\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — cell-type-specific KO, conditioned medium rescue, genetic epistasis with Wnt pathway, multiple orthogonal approaches in single study\",\n      \"pmids\": [\"32375055\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"GDE2 expressed in oligodendrocytes cell-autonomously slows the pace of oligodendrocyte maturation; oligodendrocyte-specific Gde2 KO mice show accelerated oligodendrocyte maturation and increased myelination, phenocopied in purified primary oligodendrocyte cultures.\",\n      \"method\": \"Oligodendrocyte-specific Cre-lox KO (O-Gde2KO); immunohistochemistry for myelin proteins; primary oligodendrocyte cultures\",\n      \"journal\": \"Developmental dynamics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — cell-type-specific KO with in vivo and in vitro phenotypic concordance, single lab\",\n      \"pmids\": [\"33095500\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"GDE2 trafficking is regulated by C-terminal tail sequences that control constitutive endocytosis and recycling; a C-terminal leucine residue in a unique motif is essential for GDE2 internalization, and a truncation mutant with aberrant recycling fails to cleave GPI-anchored GPC6 and is non-functional, whereas a consecutive deletion causing surface retention gains function.\",\n      \"method\": \"Live-cell imaging; FRAP; C-terminal deletion/truncation mutagenesis; GPC6 cleavage assay; neuronal differentiation assays\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — direct localization by live imaging and FRAP tied to functional GPC6 cleavage assay and differentiation readout, structure-function mutagenesis, single lab with multiple orthogonal methods\",\n      \"pmids\": [\"31932507\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"GDE2 stimulates ADAM10 α-secretase cleavage of amyloid precursor protein (APP) by shedding and inactivating the GPI-anchored RECK protein, a known ADAM10 inhibitor; genetic ablation of GDE2 elevates membrane-bound RECK, reduces sAPPα generation, increases Aβ, and causes synaptic protein loss. In Alzheimer's disease tissue, GDE2 is abnormally sequestered intracellularly and membrane RECK is elevated.\",\n      \"method\": \"Gde2 KO mouse; RECK genetic reduction rescue experiments; APP processing biochemical assays (sAPPα, Aβ measurements); human AD postmortem tissue analysis; synaptic protein quantification\",\n      \"journal\": \"Science translational medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vivo KO with biochemical substrate (APP processing) readout, genetic rescue by RECK reduction, human tissue validation, multiple orthogonal methods\",\n      \"pmids\": [\"33731436\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"In ALS patient post-mortem tissue, total GDE2 protein levels are normal but membrane GDE2 is substantially reduced, with GDE2 aberrantly accumulating in intracellular compartments of motor cortex neurons; haplogenetic reduction of GDE2 exacerbates motor neuron degeneration in SOD1G93A mice; tandem-mass-tag MS reveals reduced GPI-anchored protein release into CSF of ALS patients.\",\n      \"method\": \"Human ALS postmortem tissue immunohistochemistry and fractionation; SOD1G93A mouse genetic interaction; tandem-mass-tag mass spectrometry of CSF\",\n      \"journal\": \"Acta neuropathologica communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — subcellular fractionation tied to functional implication, in vivo genetic interaction, MS proteomics of CSF, single lab\",\n      \"pmids\": [\"35550203\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"GDE2 regulates the number and molecular composition of small extracellular vesicles (sEVs) released from neuronal cell surfaces via its GPI-anchor cleavage activity; proteomic profiling identifies at least two distinct GDE2-dependent sEV populations—one containing GDE2 itself and one harboring CD9 and BSG—enriched in cytoskeletal, actin-remodeling, synaptic, and redox proteins.\",\n      \"method\": \"Gde2 KO neurons; sEV isolation and quantification; proteomic profiling (mass spectrometry); functional GPI-cleavage activity assays\",\n      \"journal\": \"Cells\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — KO with proteomics and sEV quantification, multiple EV populations defined, single lab with single study\",\n      \"pmids\": [\"39272985\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"PRKDC recruits and binds GDE2; this interaction enhances GNAS protein stability, which activates AKT phosphorylation and confers doxorubicin resistance in osteosarcoma.\",\n      \"method\": \"CRISPR kinome screen; co-immunoprecipitation; protein stability assays; phospho-AKT measurements; xenograft and organoid rescue experiments\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — co-IP establishing PRKDC-GDE2 interaction, in vivo xenograft rescue, multiple functional readouts, single lab\",\n      \"pmids\": [\"38900943\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"GDE2 regulates hippocampal CA1 synaptic morphology and function; Gde2KO mice show increased dendritic complexity, excess mushroom spines, increased mEPSC frequency, impaired paired-pulse facilitation, and disrupted NMDAR-mediated LTD. Mechanistically, abnormal activation of the PI3K-AKT-GSK3 signaling pathway in Gde2KO hippocampus underlies LTD impairment, and PI3K inhibition restores LTD to WT levels.\",\n      \"method\": \"Gde2 KO mouse; electrophysiology (mEPSC, PPF, LTD); dendritic morphology analysis; PI3K-AKT-GSK3 pathway biochemistry; pharmacological PI3K inhibition rescue\",\n      \"journal\": \"eNeuro\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo KO with electrophysiology, pathway biochemistry, and pharmacological rescue, single lab\",\n      \"pmids\": [\"40634123\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"GDE2 inhibits excessive neuronal Wnt activation by regulating the surface expression of GPI-anchored Glypican 6 (GPC6); elevated GPC6 surface expression potentiates neuronal Wnt activation, causing nuclear pore complex disruption, altered Ran-dependent nucleocytoplasmic trafficking, and TDP-43 mislocalization; genetic reduction of GPC6 in Gde2KO mice rescues all these defects.\",\n      \"method\": \"In vivo mouse genetics (Gde2KO, GPC6 genetic reduction rescue); nuclear pore complex integrity assays; Ran-NCT assays; TDP-43 localization immunohistochemistry; Wnt signaling reporters\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo genetic epistasis with multiple cellular readouts, preprint not yet peer-reviewed, single lab\",\n      \"pmids\": [\"bio_10.1101_2025.09.24.678385\"],\n      \"is_preprint\": true\n    }\n  ],\n  \"current_model\": \"GDPD5/GDE2 is a six-transmembrane plasma-membrane enzyme with dual substrate specificity—it cleaves GPI-anchored proteins (including RECK and glypicans) and degrades glycerophosphocholine (GPC); its activity is regulated by Prdx1-mediated reduction of an inhibitory intramolecular disulfide bond (C25-C571), by Prdx4-mediated oxidative trapping in the ER, by CDK1-dependent phosphorylation of T587, and by sequence-dependent endocytic trafficking; by releasing RECK from the neuronal surface, GDE2 disinhibits ADAM10/ADAM protease activity to shed Dll1 and suppress Notch signaling, driving neuronal differentiation; postnatally it controls neuronal survival, oligodendrocyte maturation, hippocampal synaptic plasticity (via PI3K-AKT-GSK3), and APP processing (by preventing RECK-mediated ADAM10 inhibition), and its intracellular mislocalization in ALS and Alzheimer's disease impairs these protective GPI-anchor cleavage pathways.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"GDPD5 (GDE2) is a six-transmembrane plasma-membrane enzyme that drives neuronal differentiation and maintains neuronal survival through extracellular cleavage of GPI-anchored proteins [#0, #4, #10]. Although originally defined as a glycerophosphocholine phosphodiesterase that degrades GPC to glycerol-3-phosphate and choline [#1], its neurogenic activity depends on a distinct GPI-anchor cleavage activity that releases substrates such as RECK and the glypicans GPC4/GPC6 from the cell surface [#4, #9, #10]. By shedding GPI-anchored RECK, GDE2 disinhibits ADAM protease-dependent shedding of Delta-like 1, inactivating Notch signaling to promote subtype-specific motor neuron and cortical neuron production [#3, #4, #8]. GDE2 catalytic activity is gated by redox- and phosphorylation-dependent control: Prdx1 activates the enzyme by reducing an inhibitory intramolecular disulfide bridging its N- and C-terminal domains [#2], Prdx4-mediated oxidation of cysteines in the catalytic domain traps GDE2 in the ER and blocks surface trafficking [#6], and a C25-C571 disulfide, T587 dephosphorylation, and a CDK1-dependent modification inhibit GPC-PDE activity [#5]; C-terminal tail motifs further govern constitutive endocytosis and recycling required for productive substrate cleavage [#13]. Postnatally GDE2 controls neuronal survival [#10], oligodendrocyte maturation through neuronal Wnt activation and via cell-autonomous action in oligodendrocytes [#11, #12], hippocampal synaptic plasticity through restraint of PI3K-AKT-GSK3 signaling [#18], and amyloid precursor protein processing by relieving RECK-mediated ADAM10 inhibition to favor non-amyloidogenic sAPPα generation [#14]. Intracellular mislocalization of GDE2 with retained membrane RECK is observed in Alzheimer's disease tissue, and reduced membrane GDE2 with impaired GPI-anchored protein release occurs in ALS, where GDE2 reduction exacerbates motor neuron degeneration [#14, #15].\",\n  \"teleology\": [\n    {\n      \"year\": 2005,\n      \"claim\": \"Established that GDE2 is a transmembrane protein whose extracellular catalytic activity is necessary and sufficient to drive spinal motor neuron differentiation, defining it as an enzymatic regulator of neurogenesis.\",\n      \"evidence\": \"In vivo gain- and loss-of-function plus active-site mutagenesis in chick and mouse spinal cord\",\n      \"pmids\": [\"16195461\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not identify the physiological substrate\", \"Mechanism downstream of catalysis unresolved\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Assigned a defined enzymatic activity by showing GDPD5 is a glycerophosphocholine phosphodiesterase, linking it to choline/phospholipid metabolism.\",\n      \"evidence\": \"In vitro enzymatic assay on immunoprecipitated protein with siRNA and overexpression in IMCD-3 cells\",\n      \"pmids\": [\"18667693\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not connect GPC-PDE activity to the neuronal differentiation function\", \"Did not test GPI-anchored substrates\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Revealed redox-based activation, showing Prdx1 reduces an inhibitory intramolecular disulfide to switch GDE2 on, identifying the first regulatory mechanism of the enzyme.\",\n      \"evidence\": \"Reciprocal co-IP, disulfide-bond mutagenesis, Prdx1 KO mice, and differentiation assays\",\n      \"pmids\": [\"19766572\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not define the catalytic substrate driving differentiation\", \"Upstream control of Prdx1-GDE2 coupling unknown\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Placed GDE2 in a heterotrimeric G-protein context by identifying GDP-Gαi2 as an interacting partner that regulates motor neuron differentiation.\",\n      \"evidence\": \"Co-IP and in vivo complex disruption with Gαi2 KO mice and motor neuron counting\",\n      \"pmids\": [\"20197066\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism by which Gαi2 modulates GDE2 catalysis unclear\", \"Single lab\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Resolved how GDE2 controls neurogenesis by demonstrating it cleaves GPI anchors to release RECK, disinhibiting ADAM-dependent Dll1 shedding and Notch inactivation — reframing the enzyme as a GPI-anchor protease.\",\n      \"evidence\": \"GPI-anchor cleavage assays, fractionation, active-site mutagenesis, and epistasis with RECK/ADAM/Dll1-Notch\",\n      \"pmids\": [\"23329048\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not enumerate the full GPI-anchored substrate repertoire\", \"Relationship between GPI-cleavage and GPC-PDE activities unresolved\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Mapped post-translational control of GPC-PDE activity, identifying a C25-C571 disulfide, T587 phosphorylation, and a CDK1-dependent modification as osmotic stress-responsive regulatory switches.\",\n      \"evidence\": \"Site-directed mutagenesis, CDK1 inhibition, antioxidant treatment, MS of PTMs, and in vitro activity assays\",\n      \"pmids\": [\"23589856\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether these PTMs also gate GPI-anchor cleavage not tested\", \"Kinase/phosphatase identities for T587 not all defined\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Extended GDE2 function beyond motor neurons by showing it times cortical progenitor cell-cycle exit via Notch, broadening its developmental role.\",\n      \"evidence\": \"Gde2 KO mouse with BrdU birthdating, immunohistochemistry, and Notch readouts\",\n      \"pmids\": [\"22951639\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Substrate driving cortical Notch suppression not identified here\", \"Single lab\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Identified ER-based trafficking control, showing Prdx4 oxidizes GDE2 catalytic cysteines to block its surface delivery and neurogenic function.\",\n      \"evidence\": \"Prdx4 KO mouse, biochemical oxidation assays, trafficking fractionation, and cysteine mutagenesis\",\n      \"pmids\": [\"25943695\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How oxidation status is reversed at the membrane unclear\", \"Relationship to Prdx1 activation step not integrated\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Demonstrated GDE2 acts in cancer by cleaving GPI-anchored glypican-6 to drive neuroblastoma differentiation and shift Rac/RhoA balance, generalizing the GPI-cleavage mechanism to glypican substrates.\",\n      \"evidence\": \"GPI-cleavage and GPC6 release assays, active-site mutagenesis, Rac/RhoA activity, and differentiation assays\",\n      \"pmids\": [\"27693046\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Link between glypican release and cytoskeletal GTPase output not fully mechanistic\", \"Single lab\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Separated developmental from maintenance roles by showing postnatal GDE2 loss causes progressive neuronal degeneration with impaired glypican-4/6 processing as molecular correlates.\",\n      \"evidence\": \"Constitutive and conditional Gde2 KO mice with histology, electrophysiology, behavior, and GPI-anchored substrate proteomics\",\n      \"pmids\": [\"28103900\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Causal substrate for survival defect not isolated\", \"Cell-autonomous vs non-autonomous survival mechanism not resolved\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Connected neuronal GDE2 to glial development, showing it activates neuronal Wnt to secrete factors (including phosphacan) that promote oligodendrocyte maturation.\",\n      \"evidence\": \"Global and neuron-specific Gde2 KO, conditioned medium, Wnt reporters, and genetic Wnt rescue\",\n      \"pmids\": [\"32375055\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"GPI substrate linking GDE2 catalysis to Wnt activation not defined here\", \"Identity of all secreted pro-maturation factors incomplete\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Showed a cell-autonomous, opposite-direction role in oligodendrocytes where GDE2 slows maturation, indicating cell-type-specific outputs of the same enzyme.\",\n      \"evidence\": \"Oligodendrocyte-specific Cre-lox KO with myelin immunohistochemistry and primary cultures\",\n      \"pmids\": [\"33095500\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Substrate in oligodendrocytes not identified\", \"Single lab\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Defined trafficking determinants, showing C-terminal motifs controlling endocytosis/recycling are required for GPC6 cleavage and function.\",\n      \"evidence\": \"Live-cell imaging, FRAP, C-terminal mutagenesis, GPC6 cleavage, and differentiation assays\",\n      \"pmids\": [\"31932507\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Endocytic adaptors recognizing the motif not identified\", \"Single lab\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Linked GDE2 to Alzheimer's disease by showing it promotes ADAM10 α-secretase APP processing through RECK shedding, with intracellular GDE2 sequestration and elevated membrane RECK in AD tissue.\",\n      \"evidence\": \"Gde2 KO mouse, RECK genetic reduction rescue, APP processing biochemistry, and human AD postmortem analysis\",\n      \"pmids\": [\"33731436\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Cause of GDE2 intracellular sequestration in AD unknown\", \"Therapeutic reversibility not addressed\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Implicated GDE2 mislocalization in ALS, showing reduced membrane GDE2 and impaired GPI-anchored protein release, with GDE2 reduction worsening SOD1G93A degeneration.\",\n      \"evidence\": \"Human ALS postmortem fractionation/IHC, SOD1G93A genetic interaction, and TMT-MS of CSF\",\n      \"pmids\": [\"35550203\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism driving membrane loss/intracellular accumulation unknown\", \"Single lab\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Revealed a context outside neurons in which PRKDC binds GDE2 to stabilize GNAS, activate AKT, and confer doxorubicin resistance in osteosarcoma.\",\n      \"evidence\": \"CRISPR kinome screen, co-IP, protein stability assays, phospho-AKT, and xenograft/organoid rescue\",\n      \"pmids\": [\"38900943\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether GDE2 catalytic activity is required for this role untested\", \"Single lab\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Showed GDE2 GPI-anchor cleavage shapes neuronal small extracellular vesicle number and composition, extending its surface-remodeling role to EV biology.\",\n      \"evidence\": \"Gde2 KO neurons with sEV isolation, quantification, and proteomic profiling\",\n      \"pmids\": [\"39272985\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional consequences of altered sEV populations not established\", \"Single study\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Tied GDE2 to nuclear integrity and TDP-43 homeostasis, showing restraint of GPC6-driven neuronal Wnt prevents nuclear pore disruption and TDP-43 mislocalization.\",\n      \"evidence\": \"In vivo Gde2KO with GPC6 genetic reduction rescue, NPC and Ran-NCT assays, TDP-43 IHC, and Wnt reporters (preprint)\",\n      \"pmids\": [\"bio_10.1101_2025.09.24.678385\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Preprint not yet peer-reviewed\", \"Direct link between Wnt activation and NPC disruption mechanistically incomplete\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Established a synaptic plasticity role, showing GDE2 restrains PI3K-AKT-GSK3 signaling required for normal hippocampal CA1 morphology and NMDAR-dependent LTD.\",\n      \"evidence\": \"Gde2 KO mouse electrophysiology, dendritic morphology, pathway biochemistry, and PI3K inhibition rescue\",\n      \"pmids\": [\"40634123\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"GPI substrate upstream of PI3K-AKT-GSK3 not identified\", \"Single lab\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How GDE2's dual GPC-phosphodiesterase and GPI-anchor protease activities are coordinated, and what determines its substrate selection and disease-associated intracellular trapping, remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Structural basis for dual substrate specificity unknown\", \"Cause of GDE2 mislocalization in ALS/AD undefined\", \"Full GPI-anchored substrate repertoire incomplete\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140098\", \"supporting_discovery_ids\": [1, 5]},\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [4, 9, 10]},\n      {\"term_id\": \"GO:0016787\", \"supporting_discovery_ids\": [1, 4]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [0, 4, 13, 15]},\n      {\"term_id\": \"GO:0005783\", \"supporting_discovery_ids\": [6]},\n      {\"term_id\": \"GO:0031410\", \"supporting_discovery_ids\": [13]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [0, 3, 8, 11]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [4, 11, 18]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [14, 15]},\n      {\"term_id\": \"R-HSA-112316\", \"supporting_discovery_ids\": [10, 18]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"PRDX1\", \"PRDX4\", \"RECK\", \"GPC6\", \"GNAI2\", \"PRKDC\", \"GNAS\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":6,"faith_total":6,"faith_pct":100.0}}