{"gene":"CACNG2","run_date":"2026-06-09T22:57:17","timeline":{"discoveries":[{"year":2000,"finding":"Stargazin interacts with AMPA receptor subunits (required for surface membrane delivery) and with synaptic PDZ proteins such as PSD-95 via a C-terminal PDZ-binding domain (required for synaptic targeting). These are two distinct mechanisms: ectodomain–AMPAR interaction for surface delivery, and C-terminal PDZ-binding for synaptic localization.","method":"Co-immunoprecipitation, transfection rescue in stargazer cerebellar granule cells, expression of PDZ-binding domain mutant in hippocampal pyramidal cells","journal":"Nature","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP plus loss-of-function rescue experiments, replicated across labs","pmids":["11140673"],"is_preprint":false},{"year":2002,"finding":"Direct binding of the first two PDZ domains of PSD-95 to stargazin controls the number of synaptic AMPARs. Increasing PSD-95 recruits new AMPARs to synapses without changing total surface AMPARs; stargazin overexpression increases extrasynaptic AMPARs but not synaptic currents when PSD-95 is held constant. Compensatory mutations in both PSD-95 and stargazin confirmed the direct interaction is the determinant of synaptic AMPAR number.","method":"Biolistic transfection in hippocampal slice cultures, compensatory mutagenesis of PSD-95 PDZ domains and stargazin PDZ-binding motif, electrophysiology","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1 / Strong — compensatory mutagenesis with functional readout, multiple orthogonal methods","pmids":["12359873"],"is_preprint":false},{"year":2002,"finding":"PKA phosphorylates stargazin at Thr-321 within the C-terminal PDZ-binding motif, disrupting its interaction with PSD-95 and reducing synaptic AMPAR function. A phosphomimetic T321E mutation abolishes stargazin–PSD-95 co-clustering and downregulates synaptic AMPARs in hippocampal neurons.","method":"In vitro peptide phosphorylation assay, phospho-specific antibodies, yeast two-hybrid, co-immunoprecipitation, COS-7 and hippocampal neuron transfections","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro kinase assay plus mutagenesis plus functional neuron readout, confirmed by two independent labs (PMID 12122038 and 11805122)","pmids":["12122038","11805122"],"is_preprint":false},{"year":2004,"finding":"TARPs (including stargazin) are stable at the plasma membrane while AMPA receptors cycle; upon glutamate binding, AMPA receptors dissociate from stargazin by an allosteric mechanism that does not require ion flux or intracellular second messengers, and this dissociation may participate in glutamate-mediated receptor internalization.","method":"Surface biotinylation, co-immunoprecipitation, glutamate stimulation assays in heterologous cells and neurons","journal":"Science","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal Co-IP plus pharmacological dissection, single lab","pmids":["15001777"],"is_preprint":false},{"year":2005,"finding":"Stargazin's ectodomain controls AMPA receptor channel gating (slows deactivation and desensitization, increases channel opening rate), while its cytoplasmic tail determines receptor trafficking. Disrupting the stargazin ectodomain–AMPAR interaction alters the amplitude and shape of synaptic responses.","method":"Mutagenesis, electrophysiology in Xenopus oocytes and HEK cells, hippocampal slice recording","journal":"Nature","confidence":"High","confidence_rationale":"Tier 1 / Strong — domain-swap and mutagenesis with in vitro and synaptic electrophysiology, multiple orthogonal methods","pmids":["15858532"],"is_preprint":false},{"year":2005,"finding":"Stargazin reduces AMPA receptor desensitization and slows deactivation when co-expressed in Xenopus oocytes or HEK293 cells, acting as a positive allosteric modulator that stabilizes the receptor conformation and accelerates recovery from desensitization.","method":"Electrophysiology in Xenopus oocytes and HEK293 cells, co-expression studies","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 1 / Strong — replicated across multiple labs (PMIDs 15758178, 16093395, 15567474) with in vitro electrophysiology","pmids":["15758178","16093395","15567474"],"is_preprint":false},{"year":2005,"finding":"Stargazin phosphorylation by CaMKII and PKC promotes synaptic AMPAR trafficking (LTP), while dephosphorylation by PP1 (downstream of PP2B) mediates LTD. Stargazin is quantitatively phosphorylated at multiple sites and is required for bidirectional synaptic plasticity at hippocampal synapses.","method":"Phosphorylation assays, mutagenesis, hippocampal slice LTP/LTD electrophysiology, pharmacological manipulation of kinases and phosphatases","journal":"Neuron","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro kinase assays, mutagenesis, and synaptic plasticity readouts, multiple orthogonal approaches","pmids":["15664178"],"is_preprint":false},{"year":2005,"finding":"Stargazin is an auxiliary subunit of native AMPA receptor complexes in the cerebellum; blue native gel electrophoresis identifies two AMPAR populations — one containing stargazin and one lacking it. Other AMPAR-interacting proteins (SAP97, GRIP1, PICK1, NSF, AP2, 4.1N) do not significantly associate with AMPARs on native gels.","method":"Blue native gel electrophoresis of cerebellar extracts, limited proteolysis, co-immunoprecipitation","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1 / Strong — native biochemical complex analysis with proteolysis confirmation, definitive auxiliary subunit identification","pmids":["15630087"],"is_preprint":false},{"year":2005,"finding":"Stargazin promotes biosynthetic transport of AMPA receptors through the ER; its effect is mimicked and occluded by upregulation of ER chaperones (UPR), and UPR induction is detected in cerebellar granule cells lacking stargazin, indicating a role in ER processing.","method":"COS7 cell transfection, dominant-negative dynamin mutant, UPR assays, pharmacological UPR inhibition in stargazin-deficient neurons","journal":"The Journal of neuroscience","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple pharmacological and genetic approaches, single lab","pmids":["15689545"],"is_preprint":false},{"year":2006,"finding":"Stargazin controls AMPA receptor potentiator pharmacology: it makes both flip and flop splice forms of GluR1 sensitive to both cyclothiazide and PEPA, and enhances the effect of AMPAR potentiators on channel deactivation.","method":"Electrophysiology in heterologous cells co-expressing GluR1 splice variants and stargazin, with AMPAR potentiator pharmacology","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution with pharmacology, single lab","pmids":["16785437"],"is_preprint":false},{"year":2006,"finding":"Stargazin interacts functionally with the glutamate-binding domain of GluR1: a Lurcher-equivalent point mutation in the GluR1 ligand-binding domain abolishes stargazin's effects on both trafficking and gating, while a mutation preventing desensitization modulates gating effects but preserves trafficking.","method":"Site-directed mutagenesis of GluR1, co-expression with stargazin in heterologous cells, electrophysiology and surface expression assays","journal":"Neuropharmacology","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — mutagenesis with functional readout, single lab","pmids":["16919685"],"is_preprint":false},{"year":2006,"finding":"Stargazin binds MAGI-2 (a multi-PDZ scaffolding protein) via its C-terminal -TTPV motif through MAGI-2's PDZ1, PDZ3, and PDZ5 domains; this interaction was confirmed by co-immunoprecipitation from mouse cerebral cortex and in vitro binding assays.","method":"Yeast two-hybrid screening, co-immunoprecipitation from mouse brain, in vitro binding assays, HEK-293T transfection","journal":"The Journal of neuroscience","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — yeast two-hybrid plus in vivo Co-IP plus in vitro binding, single lab","pmids":["16870733"],"is_preprint":false},{"year":2007,"finding":"The stargazin–PSD-95 interaction controls AMPA receptor lateral diffusion and synaptic trapping. Disruption of the stargazin–PSD-95 interaction strongly increases AMPAR surface diffusion, preventing AMPAR accumulation at postsynaptic sites. AMPARs and stargazin diffuse as complexes into and out of synapses.","method":"Single quantum dot tracking and FRAP imaging in live hippocampal neurons, dominant-negative stargazin constructs","journal":"Neuron","confidence":"High","confidence_rationale":"Tier 2 / Strong — live single-molecule imaging plus FRAP with loss-of-function, replicated mechanistic conclusion across multiple studies","pmids":["17329211"],"is_preprint":false},{"year":2007,"finding":"Stargazin greatly reduces block of calcium-permeable AMPARs by intracellular polyamines, decreasing CP-AMPAR affinity for cytoplasmic polyamines, enhancing charge transfer after single glutamate applications, and eliminating frequency-dependent facilitation.","method":"Electrophysiology in heterologous cells and cerebellar stellate cells, polyamine block analysis","journal":"Nature neuroscience","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro reconstitution plus native cell confirmation with matched biophysical parameters","pmids":["17873873"],"is_preprint":false},{"year":2004,"finding":"Stargazin interacts with nPIST (a Golgi-enriched PDZ protein) through a novel cytoplasmic domain (residues 243–283). nPIST overexpression enhances and dominant-negative nPIST attenuates AMPAR synaptic clustering, identifying a role for stargazin–nPIST interaction in AMPAR trafficking to the synapse.","method":"Yeast two-hybrid, co-immunoprecipitation from brain, immunohistochemistry, transfection in hippocampal neurons","journal":"The Journal of neuroscience","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — yeast two-hybrid plus in vivo Co-IP plus gain/loss-of-function in neurons, single lab","pmids":["15329396"],"is_preprint":false},{"year":2004,"finding":"Microtubule-associated protein light chain 2 (LC2) directly interacts with the intracellular C-terminal tail of stargazin upstream of the -TTPV sequence, and forms a tripartite complex with stargazin and GluR2 in cerebellar neurons, suggesting a role in pre-synaptic AMPAR trafficking before synaptic anchoring.","method":"Yeast two-hybrid, immunoprecipitation of cerebellar extracts, native stargazin immunopurification","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — yeast two-hybrid plus native Co-IP confirming tripartite complex, single lab","pmids":["15136571"],"is_preprint":false},{"year":2009,"finding":"Stargazin is physiologically S-nitrosylated; S-nitrosylation increases its binding to GluR1 AMPAR subunit and causes increased surface expression of AMPARs. NMDAR stimulation activates nNOS, which increases stargazin nitrosylation and GluR1 binding.","method":"Biotin switch assay for S-nitrosylation, co-immunoprecipitation, surface biotinylation in heterologous cells and primary neurons","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — biotin-switch plus Co-IP plus surface expression, single lab","pmids":["19805317"],"is_preprint":false},{"year":2010,"finding":"CaMKII activation and postsynaptic translocation triggers synaptic trapping of AMPARs via phosphorylation of stargazin and its binding to PDZ domain scaffolds. AMPAR immobilization requires both stargazin phosphorylation and PDZ scaffold binding, but not GluA1 PDZ-binding domain or GluA1-Ser831 phosphorylation.","method":"Single-particle tracking of AMPARs in hippocampal neurons, CaMKII activation/inhibition, phosphomimetic/phospho-null stargazin mutants, short-term plasticity electrophysiology","journal":"Neuron","confidence":"High","confidence_rationale":"Tier 2 / Strong — single-molecule tracking plus mutagenesis plus functional plasticity readout, replicated mechanistic finding","pmids":["20670832"],"is_preprint":false},{"year":2013,"finding":"Stargazin forms ternary complexes with AP-2 and AP-3A adaptor proteins in a phosphorylation-state-dependent manner. Stargazin–AP-2 interaction is required for NMDA-induced AMPAR endocytosis, while stargazin–AP-3A interaction is required for late endosomal/lysosomal trafficking, preventing receptor recycling. Both interactions are necessary for LTD at CA1 synapses.","method":"Co-immunoprecipitation in hippocampal neurons, competitive peptide inhibitors, LTD electrophysiology, receptor trafficking assays","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP plus competitive disruption peptides plus LTD electrophysiology, multiple orthogonal methods","pmids":["24217640"],"is_preprint":false},{"year":2015,"finding":"Desensitized AMPARs bind less stargazin and are less stabilized at the synapse compared to open or closed-resting state receptors. Glutamate-induced AMPAR desensitization increases AMPAR mobility within the synapse, and this mobility-mediated short-term plasticity regulation is abolished when the glutamate-dependent loss in AMPAR–stargazin interaction is prevented.","method":"Single-molecule AMPAR tracking, point mutations and pharmacology to stabilize AMPAR conformational states, synaptic electrophysiology","journal":"Neuron","confidence":"High","confidence_rationale":"Tier 2 / Strong — single-molecule tracking plus pharmacological and genetic stabilization of receptor states, multiple orthogonal methods","pmids":["25661182"],"is_preprint":false},{"year":2015,"finding":"Phosphorylation-induced extension or artificial lengthening of the stargazin cytoplasmic tail enhances its binding to the deeper (farther from membrane) PDZ domains of PSD-95, which have higher affinity for the stargazin PDZ-binding motif, thereby potentiating AMPAR anchoring and synaptic transmission.","method":"Artificial linker insertion, phosphomimetic mutations, single-molecule tracking, synaptic electrophysiology in hippocampal neurons","journal":"Neuron","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — mutagenesis plus artificial linker plus functional readouts, single lab","pmids":["25843401"],"is_preprint":false},{"year":2016,"finding":"Cryo-EM structures of AMPAR–stargazin complexes reveal variable stoichiometry (one or two stargazin molecules per tetrameric AMPAR) and electrostatic interactions between the extracellular domains of AMPAR and stargazin that are conserved across AMPARs and TARPs. The structures support a model where TARPs stabilize the activated state of AMPARs.","method":"Cryo-electron microscopy, structural analysis of AMPAR–STZ complexes","journal":"Science","confidence":"High","confidence_rationale":"Tier 1 / Strong — cryo-EM structure with interface analysis providing direct structural mechanism","pmids":["27365450"],"is_preprint":false},{"year":2016,"finding":"Single-molecule LRET and smFRET show that stargazin is positioned below the AMPAR ligand-binding domain and acts as a scaffold to stabilize or select AMPAR conformational states that favor activation (conformational selection model).","method":"Luminescence resonance energy transfer (LRET), single-molecule FRET (smFRET) in HEK293 cells","journal":"Cell reports","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — structural/biophysical measurements, single lab","pmids":["27705782"],"is_preprint":false},{"year":2017,"finding":"Stargazin primarily interacts with AMPAR via membrane domains M1 and M4 of neighboring AMPAR subunits, initiated/stabilized by the AMPAR C-tail. TARP TM3, TM4, and extracellular loop 2 are also key contributors. Mechanistically, TARP binding destabilizes the channel closed state (two-step action: binding destabilizes closed state, enabling efficient opening; activated state is then stabilized via subsequent interactions).","method":"Systematic domain swaps between stargazin and TARP-insensitive GluK2 kainate receptor, TARP chimeras, electrophysiology in heterologous cells","journal":"Neuron","confidence":"High","confidence_rationale":"Tier 1 / Strong — systematic domain-swap mutagenesis with functional readouts delineating molecular mechanism","pmids":["28238551"],"is_preprint":false},{"year":2017,"finding":"Stargazin and cornichon 3 (CNIH3) share a lipid-exposed transmembrane domain surface on GluA2 (including A793 and C528 residues) for their function, but induce opposing gating effects through this shared surface. Both extracellular and TMD elements contribute independently to gating modulation by stargazin.","method":"TMD mutagenesis of GluA2, detergent stability assays, electrophysiology, cryo-EM structure comparison","journal":"The Journal of physiology","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — mutagenesis with functional readout, single lab","pmids":["28815591"],"is_preprint":false},{"year":2014,"finding":"Stargazin promotes closure of the AMPAR ligand-binding domain (LBD): it rescues gating deficits of LBD-destabilizing mutations, reduces NBQX accessibility, and LRET measurements directly show the LBD is on average more closed in both apo and agonist-bound states in the presence of stargazin.","method":"Mutagenesis of AMPAR LBD, LRET measurements, accessibility assays with NBQX, electrophysiology","journal":"The Journal of general physiology","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — structural biophysical measurements plus mutagenesis, single lab","pmids":["25422502"],"is_preprint":false},{"year":2009,"finding":"Stargazin phosphorylation protects GluR1 from lysosomal degradation and increases dendritic GluR1 levels, but does not increase surface or synaptic GluR1 levels. Stargazin does not protect GluR2 from lysosomal degradation.","method":"Viral expression of AMPAR subunits with/without stargazin in rat hippocampal neurons, lysosomal inhibition, surface biotinylation, electrophysiology","journal":"Nature neuroscience","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple biochemical and electrophysiological approaches, single lab","pmids":["19543281"],"is_preprint":false},{"year":2009,"finding":"Stargazin T321 is phosphorylated by both PKA and MAPKs. PKA phosphorylation of T321 is required for activity-dependent increases in stargazin synaptic clustering, while MAPK phosphorylation of T321 is required for activity-dependent decreases in synaptic clustering, thus controlling bidirectional synaptic plasticity.","method":"Point mutations blocking PKA- or MAPK-specific T321 phosphorylation, activity stimulation in dissociated hippocampal neurons, immunofluorescence clustering assays","journal":"Journal of neurochemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — selective mutagenesis with functional readouts, single lab","pmids":["19968761"],"is_preprint":false},{"year":2003,"finding":"Stargazin action on surface delivery is highly selective for AMPA receptors; surface delivery of kainate receptors is independent of stargazin in cerebellar granule cells and Xenopus oocytes.","method":"Electrophysiology in cerebellar granule cells and Xenopus oocytes, co-expression of kainate receptor subunits with stargazin","journal":"Molecular pharmacology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — two expression systems, clean negative result for kainate receptors, single lab","pmids":["12920207"],"is_preprint":false},{"year":2010,"finding":"Stargazin modulates CaV2.2 (N-type) channels via a Gβγ-dependent mechanism: the cytoplasmic C-terminus of stargazin binds Gβγ in vitro and counteracts Gβγ-induced inhibition of CaV2.2 and Gβγ-mediated GIRK activation. Effects on channel biophysical properties are not through direct modulation of the channel itself.","method":"Co-expression in Xenopus oocytes, Gβγ scavenger proteins, in vitro pull-down of Gβγ by stargazin C-terminus","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vitro binding plus functional oocyte assays, single lab","pmids":["20435886"],"is_preprint":false},{"year":2011,"finding":"Stargazin in cerebellar stellate cells is required for synaptic (but not extrasynaptic) AMPAR trafficking, and for activity-dependent plasticity of synaptic AMPAR rectification at parallel fiber–stellate cell synapses.","method":"Electrophysiology in stargazer mutant mice and wild-type controls, philanthotoxin-433 block, rectification index measurements","journal":"The Journal of neuroscience","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic loss-of-function with defined electrophysiological phenotype in specific cell type, single lab","pmids":["21411637"],"is_preprint":false},{"year":2011,"finding":"Calpain activation cleaves/truncates stargazin in rat brain, producing decreased stargazin immunoreactivity in the neuropil, suggesting calpain-mediated regulation of AMPAR targeting through stargazin truncation.","method":"Calcium treatment of brain sections, calpain inhibitor, immunocytochemistry, Western blot","journal":"Neuroscience","confidence":"Low","confidence_rationale":"Tier 3 / Weak — pharmacological manipulation in tissue sections, single lab, no direct mechanistic follow-up","pmids":["21256931"],"is_preprint":false},{"year":2014,"finding":"Serine racemase (SR) forms a ternary complex with PSD-95 and stargazin; SR binds stargazin C-terminus, which facilitates SR membrane localization and inhibits SR activity. AMPA receptor activation internalizes SR and disrupts stargazin–SR interaction, derepressing SR activity and increasing D-serine production, potentially coupling AMPA and NMDA receptor activities.","method":"Co-immunoprecipitation, enzyme activity assays, subcellular fractionation, AMPAR stimulation in neurons","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP plus enzyme activity plus localization, single lab","pmids":["25164819"],"is_preprint":false},{"year":2004,"finding":"Stargazin links synaptic AMPA and NMDA receptors: synaptic targeting of NMDA receptors in ventral spinal neurons and hippocampal interneurons is dependent on the presence of synaptic AMPARs, with AMPA and NMDA receptors linked by stargazin and a MAGUK protein.","method":"Transfection of NR2A/B into spinal neurons, dominant-negative GluR2 mutants, AMPAR/NMDAR clustering assays","journal":"Neuron","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic/dominant-negative approach with defined clustering readout, single lab","pmids":["15473971"],"is_preprint":false},{"year":2018,"finding":"Stargazin dephosphorylation during homeostatic synaptic downscaling increases stargazin surface mobility and GluA1-AMPAR mobility at synaptic sites. Stargazin dephosphorylation mediates interaction with AP-2 and AP-3A to promote AMPAR endocytosis and lysosomal degradation; disruption of stargazin–AP-3A interaction prevents GluA1 surface decrease during chronic activity elevation.","method":"Single-molecule tracking, competitive peptide inhibitors for AP-2 and AP-3A, surface biotinylation, chronic activity manipulation in cortical neurons","journal":"Frontiers in molecular neuroscience","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — single-molecule tracking plus peptide disruption plus biochemical assays, single lab","pmids":["30271322"],"is_preprint":false},{"year":2019,"finding":"Stargazin (γ-2) slows both channel opening (kop) and closing (kcl) rates of GluA4 homomeric channels by approximately 4-fold and 3-fold, respectively, without appreciable change in channel-opening probability, lengthening the lifetime of open channels and allowing larger charge transfer.","method":"Laser-pulse photolysis technique with rapid glutamate application, single-channel kinetic analysis","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution with defined kinetic measurements, single lab","pmids":["31267004"],"is_preprint":false},{"year":2017,"finding":"Stargazin enhances the AMPAR response to low concentrations of glutamate; at the cerebellar mossy fiber–unipolar brush cell synapse, recovery from AMPAR desensitization during slow EPSCs is mediated by stargazin enabling receptor responses to declining synaptic glutamate levels.","method":"Electrophysiology at identified cerebellar synapses, pharmacological manipulation of AMPAR desensitization and glutamate transporters","journal":"Neuron","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — defined synaptic preparation with pharmacological dissection, single lab","pmids":["28919175"],"is_preprint":false},{"year":2007,"finding":"The C-terminal cytoplasmic tail of stargazin encodes an intrinsic and transferable membrane sorting signal; fusing it to heterologous receptors (GluR1 or GnRH receptor) promotes ER exit and basolateral membrane sorting.","method":"Chimeric receptor constructs, confocal imaging of membrane sorting in transfected cells","journal":"The Journal of biological chemistry","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single-method confocal imaging, single lab, no functional synaptic readout","pmids":["17986442"],"is_preprint":false},{"year":2005,"finding":"Stargazin-mediated trafficking to the plasma membrane and its modulation of AMPAR gating/desensitization are separable functions requiring different AMPAR domains: the cytoplasmic domain is required for trafficking (FRET interaction in ER) but not for desensitization modulation.","method":"FRET between fluorophore-tagged GluR1/GluR2 and stargazin, confocal surface expression imaging, electrophysiology in HEK cells","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — FRET plus electrophysiology, two orthogonal methods, single lab","pmids":["16793768"],"is_preprint":false},{"year":2022,"finding":"The intellectual disability-associated stargazin V143L mutation weakens the AMPAR:stargazin complex interface (predicted by molecular dynamics), and knock-in mice exhibit impaired spine maturation, abnormal synaptic transmission, impaired LTP specifically in basal dendrites of CA1 neurons, and cognitive/social deficits.","method":"Molecular dynamics simulations, knock-in mouse model, dendritic spine imaging, patch-clamp electrophysiology, behavioral testing","journal":"Molecular psychiatry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — knock-in mouse with defined cellular and behavioral phenotype plus computational prediction, single lab","pmids":["35256745"],"is_preprint":false}],"current_model":"Stargazin (CACNG2) is an obligate auxiliary subunit of neuronal AMPA receptors that functions through two separable mechanisms: its extracellular/transmembrane domains (primarily M1/M4 of neighboring AMPAR subunits and TM3/TM4 of stargazin itself) allosterically modulate channel gating by destabilizing the closed state and stabilizing the activated/open state, slowing deactivation and desensitization; while its cytoplasmic tail governs receptor trafficking through direct binding to PSD-95 (trapping diffusing AMPAR–stargazin complexes at the synapse) and to adaptor proteins AP-2 and AP-3A (controlling endocytosis and lysosomal routing). Phosphorylation of stargazin by CaMKII/PKC promotes synaptic AMPAR insertion (LTP), dephosphorylation by PP2B/PP1 promotes removal (LTD), and PKA/MAPK phosphorylation at Thr-321 within the PDZ-binding motif dynamically regulates the stargazin–PSD-95 interaction and bidirectional plasticity; additional post-translational regulation by S-nitrosylation and calpain cleavage further modulates AMPAR surface expression."},"narrative":{"mechanistic_narrative":"Stargazin (CACNG2) is an obligate auxiliary (TARP) subunit of native neuronal AMPA receptor complexes that couples receptor surface delivery, synaptic anchoring, and channel gating into one regulated system [PMID:11140673, PMID:15630087]. It acts through two structurally and functionally separable modules: an extracellular/transmembrane interface that allosterically tunes channel behavior, and a cytoplasmic tail that directs trafficking and synaptic localization [PMID:15858532, PMID:16793768]. Through its membrane-domain contacts with neighboring AMPAR subunits (M1/M4) and its own TM3/TM4 and extracellular loop 2, stargazin destabilizes the closed channel state and stabilizes the activated/open state, slowing deactivation and desensitization, accelerating recovery, and promoting closure of the ligand-binding domain [PMID:15758178, PMID:16093395, PMID:15567474, PMID:28238551, PMID:25422502]; cryo-EM and single-molecule energy-transfer studies place stargazin beneath the AMPAR ligand-binding domain with conserved electrostatic interfaces and variable stoichiometry, supporting a conformational-selection model favoring the activated state [PMID:27365450, PMID:27705782]. It additionally relieves intracellular polyamine block of calcium-permeable AMPARs and shapes responses to declining synaptic glutamate, with these effects selective for AMPA over kainate receptors [PMID:17873873, PMID:28919175, PMID:12920207]. The cytoplasmic tail binds the first two PDZ domains of PSD-95, trapping diffusing AMPAR–stargazin complexes at synapses and setting synaptic AMPAR number; disrupting this interaction increases receptor surface diffusion and prevents postsynaptic accumulation [PMID:12359873, PMID:17329211]. Glutamate binding allosterically dissociates AMPARs from stargazin, and desensitized receptors bind stargazin more weakly and become more mobile, linking receptor conformational state to synaptic stabilization [PMID:15001777, PMID:25661182]. Stargazin phosphorylation controls bidirectional plasticity: CaMKII/PKC phosphorylation and PKA phosphorylation at Thr-321 promote synaptic trapping and AMPAR insertion, while MAPK phosphorylation and PP1/PP2B-mediated dephosphorylation drive removal; phosphorylation extends the tail to engage higher-affinity deep PDZ domains of PSD-95, and PKA phosphorylation of Thr-321 within the PDZ-binding motif disrupts the PSD-95 interaction [PMID:12122038, PMID:11805122, PMID:15664178, PMID:20670832, PMID:25843401, PMID:19968761]. In its dephosphorylated state, stargazin recruits AP-2 and AP-3A adaptors to drive NMDA-induced endocytosis, lysosomal routing, and homeostatic downscaling underlying LTD [PMID:24217640, PMID:30271322]. The intellectual-disability-associated V143L mutation weakens the AMPAR:stargazin interface and produces impaired spine maturation, deficient CA1 LTP, and cognitive/social deficits in knock-in mice [PMID:35256745].","teleology":[{"year":2000,"claim":"Established stargazin as a dual-function AMPAR partner, resolving how a single auxiliary protein could both deliver receptors to the surface and target them to synapses.","evidence":"Co-IP plus transfection rescue in stargazer granule cells and PDZ-binding mutant expression in pyramidal cells","pmids":["11140673"],"confidence":"High","gaps":["Did not define the structural interface of the ectodomain–AMPAR interaction","Did not establish stoichiometry or gating consequences"]},{"year":2002,"claim":"Showed that direct stargazin–PSD-95 PDZ binding quantitatively sets synaptic AMPAR number and that PKA phosphorylation at Thr-321 disrupts this interaction, defining a tunable molecular switch for synaptic strength.","evidence":"Compensatory PDZ/PDZ-motif mutagenesis with electrophysiology, plus in vitro kinase assay, phospho-specific antibodies and neuronal readouts","pmids":["12359873","12122038","11805122"],"confidence":"High","gaps":["Did not resolve the dynamics of complex trapping versus diffusion","Did not identify the upstream signals coupling activity to PKA phosphorylation in vivo"]},{"year":2004,"claim":"Demonstrated that glutamate binding allosterically dissociates AMPARs from a membrane-stable stargazin pool, linking receptor activation to internalization independently of ion flux.","evidence":"Surface biotinylation, Co-IP and glutamate stimulation in heterologous cells and neurons","pmids":["15001777"],"confidence":"Medium","gaps":["Single lab","Did not establish whether dissociation is required for endocytosis in vivo"]},{"year":2005,"claim":"Separated stargazin's two mechanisms anatomically — ectodomain controls gating (slowed deactivation/desensitization) while the cytoplasmic tail controls trafficking — and confirmed it is a native AMPAR complex subunit required for bidirectional plasticity.","evidence":"Domain swaps and mutagenesis with oocyte/HEK and slice electrophysiology, blue native gels of cerebellar complexes, kinase/phosphatase manipulation of LTP/LTD","pmids":["15858532","15758178","16093395","15567474","15664178","15630087"],"confidence":"High","gaps":["Did not provide atomic-resolution view of the gating interface","Did not map all phosphorylation sites to specific plasticity outcomes"]},{"year":2007,"claim":"Established that the stargazin–PSD-95 interaction works by trapping laterally diffusing AMPAR–stargazin complexes and that stargazin relieves polyamine block of calcium-permeable AMPARs, connecting molecular interactions to receptor mobility and biophysics.","evidence":"Single quantum-dot tracking and FRAP with dominant-negative stargazin; polyamine block analysis in heterologous and stellate cells","pmids":["17329211","17873873"],"confidence":"High","gaps":["Did not resolve how phosphorylation state alters trapping kinetics","Polyamine effect mechanism at the structural level undefined"]},{"year":2010,"claim":"Demonstrated that CaMKII activation triggers synaptic AMPAR trapping specifically through stargazin phosphorylation and PDZ scaffold binding, identifying stargazin rather than GluA1 as the phosphorylation substrate for plasticity-driven immobilization.","evidence":"Single-particle tracking with CaMKII manipulation, phosphomimetic/null stargazin mutants, short-term plasticity electrophysiology","pmids":["20670832"],"confidence":"High","gaps":["Did not quantify contribution of individual phospho-sites","Did not address other TARP family members in the same pathway"]},{"year":2013,"claim":"Identified phosphorylation-state-dependent stargazin–AP-2 and stargazin–AP-3A complexes as the machinery for NMDA-induced endocytosis and lysosomal routing, completing the removal arm of plasticity.","evidence":"Co-IP, competitive disruption peptides and LTD electrophysiology in hippocampal neurons","pmids":["24217640"],"confidence":"High","gaps":["Single lab for the dual-adaptor model","Did not resolve the structural basis of phospho-dependent adaptor selectivity"]},{"year":2015,"claim":"Showed that AMPAR conformational state controls stargazin affinity — desensitized receptors bind less stargazin and become more mobile — and that tail lengthening by phosphorylation engages higher-affinity deep PSD-95 PDZ domains, mechanistically coupling gating to anchoring.","evidence":"Single-molecule tracking with conformational-state stabilization; artificial linker insertion and phosphomimetics with synaptic electrophysiology","pmids":["25661182","25843401"],"confidence":"High","gaps":["Deep-PDZ model from a single lab","Did not measure in vivo tail extension dynamics"]},{"year":2016,"claim":"Provided direct structural mechanism: cryo-EM and energy-transfer studies positioned stargazin below the ligand-binding domain with conserved electrostatic interfaces and variable stoichiometry, supporting a conformational-selection model for activated-state stabilization.","evidence":"Cryo-EM of AMPAR–stargazin complexes; LRET/smFRET in HEK293 cells","pmids":["27365450","27705782"],"confidence":"High","gaps":["Functional consequence of one-versus-two stargazin stoichiometry unresolved","Cytoplasmic tail interactions not visualized"]},{"year":2017,"claim":"Delineated the molecular interface as AMPAR M1/M4 contacts initiated by the C-tail plus TARP TM3/TM4 and extracellular loop 2, with a two-step gating mechanism (destabilize closed state, then stabilize activated state).","evidence":"Systematic stargazin/GluK2 domain swaps and TARP chimeras with electrophysiology","pmids":["28238551"],"confidence":"High","gaps":["Did not assign individual residues to each step","Did not address tail-dependent trafficking in the same assay"]},{"year":2022,"claim":"Connected stargazin dysfunction to human disease by showing that the V143L mutation weakens the AMPAR:stargazin interface and causes synaptic, plasticity, and behavioral deficits in knock-in mice.","evidence":"Molecular dynamics, knock-in mouse with spine imaging, patch-clamp electrophysiology and behavioral testing","pmids":["35256745"],"confidence":"Medium","gaps":["Single lab","Causal link from interface weakening to specific behavioral phenotypes not fully dissected"]},{"year":null,"claim":"How the full repertoire of post-translational modifications (phosphorylation, S-nitrosylation, calpain cleavage) is integrated in vivo to set AMPAR surface levels, and how non-AMPAR functions (CaV2.2/Gβγ modulation, serine racemase regulation) contribute physiologically, remains unresolved.","evidence":"","pmids":[],"confidence":"Low","gaps":["S-nitrosylation and calpain regulation rest on single-lab evidence","Non-AMPAR roles (CaV2.2, serine racemase, nPIST, LC2, MAGI-2) not integrated into a unified physiological model"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[5,23,4,13]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[0,1,12,18]},{"term_id":"GO:0005198","term_label":"structural molecule activity","supporting_discovery_ids":[7,21]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[3,0,12]},{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[1,17]},{"term_id":"GO:0005783","term_label":"endoplasmic reticulum","supporting_discovery_ids":[8,38]}],"pathway":[{"term_id":"R-HSA-112316","term_label":"Neuronal System","supporting_discovery_ids":[0,6,17,18]},{"term_id":"R-HSA-9609507","term_label":"Protein localization","supporting_discovery_ids":[0,8,18,34]}],"complexes":["AMPA receptor–TARP complex","AMPAR–stargazin–PSD-95 complex"],"partners":["GRIA1","GRIA2","DLG4","AP2","AP3","MAGI2","GOPC","SRR"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q9Y698","full_name":"Voltage-dependent calcium channel gamma-2 subunit","aliases":["Neuronal voltage-gated calcium channel gamma-2 subunit","Transmembrane AMPAR regulatory protein gamma-2","TARP gamma-2"],"length_aa":323,"mass_kda":36.0,"function":"Regulates the trafficking and gating properties of AMPA-selective glutamate receptors (AMPARs). Promotes their targeting to the cell membrane and synapses and modulates their gating properties by slowing their rates of activation, deactivation and desensitization. Does not show subunit-specific AMPA receptor regulation and regulates all AMPAR subunits. Thought to stabilize the calcium channel in an inactivated (closed) state","subcellular_location":"Membrane; Synapse, synaptosome","url":"https://www.uniprot.org/uniprotkb/Q9Y698/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/CACNG2","classification":"Not Classified","n_dependent_lines":16,"n_total_lines":1208,"dependency_fraction":0.013245033112582781},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/CACNG2","total_profiled":1310},"omim":[{"mim_id":"614256","title":"INTELLECTUAL DEVELOPMENTAL DISORDER, AUTOSOMAL DOMINANT 10; MRD10","url":"https://www.omim.org/entry/614256"},{"mim_id":"613346","title":"SHISA FAMILY, MEMBER 9; SHISA9","url":"https://www.omim.org/entry/613346"},{"mim_id":"609946","title":"DEAFNESS, AUTOSOMAL RECESSIVE 47; DFNB47","url":"https://www.omim.org/entry/609946"},{"mim_id":"606405","title":"CALCIUM CHANNEL, VOLTAGE-DEPENDENT, GAMMA-5 SUBUNIT; CACNG5","url":"https://www.omim.org/entry/606405"},{"mim_id":"606404","title":"CALCIUM CHANNEL, VOLTAGE-DEPENDENT, GAMMA-4 SUBUNIT; CACNG4","url":"https://www.omim.org/entry/606404"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Group enriched","tissue_distribution":"Detected in some","driving_tissues":[{"tissue":"brain","ntpm":10.3},{"tissue":"retina","ntpm":2.6}],"url":"https://www.proteinatlas.org/search/CACNG2"},"hgnc":{"alias_symbol":["stargazin","MGC138502","MGC138504"],"prev_symbol":[]},"alphafold":{"accession":"Q9Y698","domains":[{"cath_id":"1.20.140.150","chopping":"1-40_55-82_92-164_172-207","consensus_level":"medium","plddt":82.5862,"start":1,"end":207}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9Y698","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9Y698-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9Y698-F1-predicted_aligned_error_v6.png","plddt_mean":66.56},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=CACNG2","jax_strain_url":"https://www.jax.org/strain/search?query=CACNG2"},"sequence":{"accession":"Q9Y698","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9Y698.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9Y698/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9Y698"}},"corpus_meta":[{"pmid":"11140673","id":"PMC_11140673","title":"Stargazin 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Hypoxia-Induced Neuronal Apoptosis and Impairs Cell Viability by Targeting FGF9/CACNG2 and Mediating MAPK Pathway in Ischemic Stroke.","date":"2020","source":"Frontiers in neurology","url":"https://pubmed.ncbi.nlm.nih.gov/32587563","citation_count":11,"is_preprint":false},{"pmid":"10643919","id":"PMC_10643919","title":"Genetic localization of the Ca2+ channel gene CACNG2 near SCA10 on chromosome 22q13.","date":"2000","source":"Epilepsia","url":"https://pubmed.ncbi.nlm.nih.gov/10643919","citation_count":10,"is_preprint":false},{"pmid":"23038240","id":"PMC_23038240","title":"Evidence for association of bipolar disorder to haplotypes in the 22q12.3 region near the genes stargazin, IFT27 and parvalbumin.","date":"2012","source":"American journal of medical genetics. 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These are two distinct mechanisms: ectodomain–AMPAR interaction for surface delivery, and C-terminal PDZ-binding for synaptic localization.\",\n      \"method\": \"Co-immunoprecipitation, transfection rescue in stargazer cerebellar granule cells, expression of PDZ-binding domain mutant in hippocampal pyramidal cells\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP plus loss-of-function rescue experiments, replicated across labs\",\n      \"pmids\": [\"11140673\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"Direct binding of the first two PDZ domains of PSD-95 to stargazin controls the number of synaptic AMPARs. Increasing PSD-95 recruits new AMPARs to synapses without changing total surface AMPARs; stargazin overexpression increases extrasynaptic AMPARs but not synaptic currents when PSD-95 is held constant. Compensatory mutations in both PSD-95 and stargazin confirmed the direct interaction is the determinant of synaptic AMPAR number.\",\n      \"method\": \"Biolistic transfection in hippocampal slice cultures, compensatory mutagenesis of PSD-95 PDZ domains and stargazin PDZ-binding motif, electrophysiology\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — compensatory mutagenesis with functional readout, multiple orthogonal methods\",\n      \"pmids\": [\"12359873\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"PKA phosphorylates stargazin at Thr-321 within the C-terminal PDZ-binding motif, disrupting its interaction with PSD-95 and reducing synaptic AMPAR function. A phosphomimetic T321E mutation abolishes stargazin–PSD-95 co-clustering and downregulates synaptic AMPARs in hippocampal neurons.\",\n      \"method\": \"In vitro peptide phosphorylation assay, phospho-specific antibodies, yeast two-hybrid, co-immunoprecipitation, COS-7 and hippocampal neuron transfections\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro kinase assay plus mutagenesis plus functional neuron readout, confirmed by two independent labs (PMID 12122038 and 11805122)\",\n      \"pmids\": [\"12122038\", \"11805122\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"TARPs (including stargazin) are stable at the plasma membrane while AMPA receptors cycle; upon glutamate binding, AMPA receptors dissociate from stargazin by an allosteric mechanism that does not require ion flux or intracellular second messengers, and this dissociation may participate in glutamate-mediated receptor internalization.\",\n      \"method\": \"Surface biotinylation, co-immunoprecipitation, glutamate stimulation assays in heterologous cells and neurons\",\n      \"journal\": \"Science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal Co-IP plus pharmacological dissection, single lab\",\n      \"pmids\": [\"15001777\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Stargazin's ectodomain controls AMPA receptor channel gating (slows deactivation and desensitization, increases channel opening rate), while its cytoplasmic tail determines receptor trafficking. Disrupting the stargazin ectodomain–AMPAR interaction alters the amplitude and shape of synaptic responses.\",\n      \"method\": \"Mutagenesis, electrophysiology in Xenopus oocytes and HEK cells, hippocampal slice recording\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — domain-swap and mutagenesis with in vitro and synaptic electrophysiology, multiple orthogonal methods\",\n      \"pmids\": [\"15858532\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Stargazin reduces AMPA receptor desensitization and slows deactivation when co-expressed in Xenopus oocytes or HEK293 cells, acting as a positive allosteric modulator that stabilizes the receptor conformation and accelerates recovery from desensitization.\",\n      \"method\": \"Electrophysiology in Xenopus oocytes and HEK293 cells, co-expression studies\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — replicated across multiple labs (PMIDs 15758178, 16093395, 15567474) with in vitro electrophysiology\",\n      \"pmids\": [\"15758178\", \"16093395\", \"15567474\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Stargazin phosphorylation by CaMKII and PKC promotes synaptic AMPAR trafficking (LTP), while dephosphorylation by PP1 (downstream of PP2B) mediates LTD. Stargazin is quantitatively phosphorylated at multiple sites and is required for bidirectional synaptic plasticity at hippocampal synapses.\",\n      \"method\": \"Phosphorylation assays, mutagenesis, hippocampal slice LTP/LTD electrophysiology, pharmacological manipulation of kinases and phosphatases\",\n      \"journal\": \"Neuron\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro kinase assays, mutagenesis, and synaptic plasticity readouts, multiple orthogonal approaches\",\n      \"pmids\": [\"15664178\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Stargazin is an auxiliary subunit of native AMPA receptor complexes in the cerebellum; blue native gel electrophoresis identifies two AMPAR populations — one containing stargazin and one lacking it. Other AMPAR-interacting proteins (SAP97, GRIP1, PICK1, NSF, AP2, 4.1N) do not significantly associate with AMPARs on native gels.\",\n      \"method\": \"Blue native gel electrophoresis of cerebellar extracts, limited proteolysis, co-immunoprecipitation\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — native biochemical complex analysis with proteolysis confirmation, definitive auxiliary subunit identification\",\n      \"pmids\": [\"15630087\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Stargazin promotes biosynthetic transport of AMPA receptors through the ER; its effect is mimicked and occluded by upregulation of ER chaperones (UPR), and UPR induction is detected in cerebellar granule cells lacking stargazin, indicating a role in ER processing.\",\n      \"method\": \"COS7 cell transfection, dominant-negative dynamin mutant, UPR assays, pharmacological UPR inhibition in stargazin-deficient neurons\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple pharmacological and genetic approaches, single lab\",\n      \"pmids\": [\"15689545\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Stargazin controls AMPA receptor potentiator pharmacology: it makes both flip and flop splice forms of GluR1 sensitive to both cyclothiazide and PEPA, and enhances the effect of AMPAR potentiators on channel deactivation.\",\n      \"method\": \"Electrophysiology in heterologous cells co-expressing GluR1 splice variants and stargazin, with AMPAR potentiator pharmacology\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstitution with pharmacology, single lab\",\n      \"pmids\": [\"16785437\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Stargazin interacts functionally with the glutamate-binding domain of GluR1: a Lurcher-equivalent point mutation in the GluR1 ligand-binding domain abolishes stargazin's effects on both trafficking and gating, while a mutation preventing desensitization modulates gating effects but preserves trafficking.\",\n      \"method\": \"Site-directed mutagenesis of GluR1, co-expression with stargazin in heterologous cells, electrophysiology and surface expression assays\",\n      \"journal\": \"Neuropharmacology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — mutagenesis with functional readout, single lab\",\n      \"pmids\": [\"16919685\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Stargazin binds MAGI-2 (a multi-PDZ scaffolding protein) via its C-terminal -TTPV motif through MAGI-2's PDZ1, PDZ3, and PDZ5 domains; this interaction was confirmed by co-immunoprecipitation from mouse cerebral cortex and in vitro binding assays.\",\n      \"method\": \"Yeast two-hybrid screening, co-immunoprecipitation from mouse brain, in vitro binding assays, HEK-293T transfection\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — yeast two-hybrid plus in vivo Co-IP plus in vitro binding, single lab\",\n      \"pmids\": [\"16870733\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"The stargazin–PSD-95 interaction controls AMPA receptor lateral diffusion and synaptic trapping. Disruption of the stargazin–PSD-95 interaction strongly increases AMPAR surface diffusion, preventing AMPAR accumulation at postsynaptic sites. AMPARs and stargazin diffuse as complexes into and out of synapses.\",\n      \"method\": \"Single quantum dot tracking and FRAP imaging in live hippocampal neurons, dominant-negative stargazin constructs\",\n      \"journal\": \"Neuron\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — live single-molecule imaging plus FRAP with loss-of-function, replicated mechanistic conclusion across multiple studies\",\n      \"pmids\": [\"17329211\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Stargazin greatly reduces block of calcium-permeable AMPARs by intracellular polyamines, decreasing CP-AMPAR affinity for cytoplasmic polyamines, enhancing charge transfer after single glutamate applications, and eliminating frequency-dependent facilitation.\",\n      \"method\": \"Electrophysiology in heterologous cells and cerebellar stellate cells, polyamine block analysis\",\n      \"journal\": \"Nature neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro reconstitution plus native cell confirmation with matched biophysical parameters\",\n      \"pmids\": [\"17873873\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Stargazin interacts with nPIST (a Golgi-enriched PDZ protein) through a novel cytoplasmic domain (residues 243–283). nPIST overexpression enhances and dominant-negative nPIST attenuates AMPAR synaptic clustering, identifying a role for stargazin–nPIST interaction in AMPAR trafficking to the synapse.\",\n      \"method\": \"Yeast two-hybrid, co-immunoprecipitation from brain, immunohistochemistry, transfection in hippocampal neurons\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — yeast two-hybrid plus in vivo Co-IP plus gain/loss-of-function in neurons, single lab\",\n      \"pmids\": [\"15329396\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Microtubule-associated protein light chain 2 (LC2) directly interacts with the intracellular C-terminal tail of stargazin upstream of the -TTPV sequence, and forms a tripartite complex with stargazin and GluR2 in cerebellar neurons, suggesting a role in pre-synaptic AMPAR trafficking before synaptic anchoring.\",\n      \"method\": \"Yeast two-hybrid, immunoprecipitation of cerebellar extracts, native stargazin immunopurification\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — yeast two-hybrid plus native Co-IP confirming tripartite complex, single lab\",\n      \"pmids\": [\"15136571\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Stargazin is physiologically S-nitrosylated; S-nitrosylation increases its binding to GluR1 AMPAR subunit and causes increased surface expression of AMPARs. NMDAR stimulation activates nNOS, which increases stargazin nitrosylation and GluR1 binding.\",\n      \"method\": \"Biotin switch assay for S-nitrosylation, co-immunoprecipitation, surface biotinylation in heterologous cells and primary neurons\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — biotin-switch plus Co-IP plus surface expression, single lab\",\n      \"pmids\": [\"19805317\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"CaMKII activation and postsynaptic translocation triggers synaptic trapping of AMPARs via phosphorylation of stargazin and its binding to PDZ domain scaffolds. AMPAR immobilization requires both stargazin phosphorylation and PDZ scaffold binding, but not GluA1 PDZ-binding domain or GluA1-Ser831 phosphorylation.\",\n      \"method\": \"Single-particle tracking of AMPARs in hippocampal neurons, CaMKII activation/inhibition, phosphomimetic/phospho-null stargazin mutants, short-term plasticity electrophysiology\",\n      \"journal\": \"Neuron\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — single-molecule tracking plus mutagenesis plus functional plasticity readout, replicated mechanistic finding\",\n      \"pmids\": [\"20670832\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Stargazin forms ternary complexes with AP-2 and AP-3A adaptor proteins in a phosphorylation-state-dependent manner. Stargazin–AP-2 interaction is required for NMDA-induced AMPAR endocytosis, while stargazin–AP-3A interaction is required for late endosomal/lysosomal trafficking, preventing receptor recycling. Both interactions are necessary for LTD at CA1 synapses.\",\n      \"method\": \"Co-immunoprecipitation in hippocampal neurons, competitive peptide inhibitors, LTD electrophysiology, receptor trafficking assays\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP plus competitive disruption peptides plus LTD electrophysiology, multiple orthogonal methods\",\n      \"pmids\": [\"24217640\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Desensitized AMPARs bind less stargazin and are less stabilized at the synapse compared to open or closed-resting state receptors. Glutamate-induced AMPAR desensitization increases AMPAR mobility within the synapse, and this mobility-mediated short-term plasticity regulation is abolished when the glutamate-dependent loss in AMPAR–stargazin interaction is prevented.\",\n      \"method\": \"Single-molecule AMPAR tracking, point mutations and pharmacology to stabilize AMPAR conformational states, synaptic electrophysiology\",\n      \"journal\": \"Neuron\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — single-molecule tracking plus pharmacological and genetic stabilization of receptor states, multiple orthogonal methods\",\n      \"pmids\": [\"25661182\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Phosphorylation-induced extension or artificial lengthening of the stargazin cytoplasmic tail enhances its binding to the deeper (farther from membrane) PDZ domains of PSD-95, which have higher affinity for the stargazin PDZ-binding motif, thereby potentiating AMPAR anchoring and synaptic transmission.\",\n      \"method\": \"Artificial linker insertion, phosphomimetic mutations, single-molecule tracking, synaptic electrophysiology in hippocampal neurons\",\n      \"journal\": \"Neuron\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — mutagenesis plus artificial linker plus functional readouts, single lab\",\n      \"pmids\": [\"25843401\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Cryo-EM structures of AMPAR–stargazin complexes reveal variable stoichiometry (one or two stargazin molecules per tetrameric AMPAR) and electrostatic interactions between the extracellular domains of AMPAR and stargazin that are conserved across AMPARs and TARPs. The structures support a model where TARPs stabilize the activated state of AMPARs.\",\n      \"method\": \"Cryo-electron microscopy, structural analysis of AMPAR–STZ complexes\",\n      \"journal\": \"Science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — cryo-EM structure with interface analysis providing direct structural mechanism\",\n      \"pmids\": [\"27365450\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Single-molecule LRET and smFRET show that stargazin is positioned below the AMPAR ligand-binding domain and acts as a scaffold to stabilize or select AMPAR conformational states that favor activation (conformational selection model).\",\n      \"method\": \"Luminescence resonance energy transfer (LRET), single-molecule FRET (smFRET) in HEK293 cells\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — structural/biophysical measurements, single lab\",\n      \"pmids\": [\"27705782\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Stargazin primarily interacts with AMPAR via membrane domains M1 and M4 of neighboring AMPAR subunits, initiated/stabilized by the AMPAR C-tail. TARP TM3, TM4, and extracellular loop 2 are also key contributors. Mechanistically, TARP binding destabilizes the channel closed state (two-step action: binding destabilizes closed state, enabling efficient opening; activated state is then stabilized via subsequent interactions).\",\n      \"method\": \"Systematic domain swaps between stargazin and TARP-insensitive GluK2 kainate receptor, TARP chimeras, electrophysiology in heterologous cells\",\n      \"journal\": \"Neuron\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — systematic domain-swap mutagenesis with functional readouts delineating molecular mechanism\",\n      \"pmids\": [\"28238551\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Stargazin and cornichon 3 (CNIH3) share a lipid-exposed transmembrane domain surface on GluA2 (including A793 and C528 residues) for their function, but induce opposing gating effects through this shared surface. Both extracellular and TMD elements contribute independently to gating modulation by stargazin.\",\n      \"method\": \"TMD mutagenesis of GluA2, detergent stability assays, electrophysiology, cryo-EM structure comparison\",\n      \"journal\": \"The Journal of physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — mutagenesis with functional readout, single lab\",\n      \"pmids\": [\"28815591\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Stargazin promotes closure of the AMPAR ligand-binding domain (LBD): it rescues gating deficits of LBD-destabilizing mutations, reduces NBQX accessibility, and LRET measurements directly show the LBD is on average more closed in both apo and agonist-bound states in the presence of stargazin.\",\n      \"method\": \"Mutagenesis of AMPAR LBD, LRET measurements, accessibility assays with NBQX, electrophysiology\",\n      \"journal\": \"The Journal of general physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — structural biophysical measurements plus mutagenesis, single lab\",\n      \"pmids\": [\"25422502\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Stargazin phosphorylation protects GluR1 from lysosomal degradation and increases dendritic GluR1 levels, but does not increase surface or synaptic GluR1 levels. Stargazin does not protect GluR2 from lysosomal degradation.\",\n      \"method\": \"Viral expression of AMPAR subunits with/without stargazin in rat hippocampal neurons, lysosomal inhibition, surface biotinylation, electrophysiology\",\n      \"journal\": \"Nature neuroscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple biochemical and electrophysiological approaches, single lab\",\n      \"pmids\": [\"19543281\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Stargazin T321 is phosphorylated by both PKA and MAPKs. PKA phosphorylation of T321 is required for activity-dependent increases in stargazin synaptic clustering, while MAPK phosphorylation of T321 is required for activity-dependent decreases in synaptic clustering, thus controlling bidirectional synaptic plasticity.\",\n      \"method\": \"Point mutations blocking PKA- or MAPK-specific T321 phosphorylation, activity stimulation in dissociated hippocampal neurons, immunofluorescence clustering assays\",\n      \"journal\": \"Journal of neurochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — selective mutagenesis with functional readouts, single lab\",\n      \"pmids\": [\"19968761\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"Stargazin action on surface delivery is highly selective for AMPA receptors; surface delivery of kainate receptors is independent of stargazin in cerebellar granule cells and Xenopus oocytes.\",\n      \"method\": \"Electrophysiology in cerebellar granule cells and Xenopus oocytes, co-expression of kainate receptor subunits with stargazin\",\n      \"journal\": \"Molecular pharmacology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — two expression systems, clean negative result for kainate receptors, single lab\",\n      \"pmids\": [\"12920207\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Stargazin modulates CaV2.2 (N-type) channels via a Gβγ-dependent mechanism: the cytoplasmic C-terminus of stargazin binds Gβγ in vitro and counteracts Gβγ-induced inhibition of CaV2.2 and Gβγ-mediated GIRK activation. Effects on channel biophysical properties are not through direct modulation of the channel itself.\",\n      \"method\": \"Co-expression in Xenopus oocytes, Gβγ scavenger proteins, in vitro pull-down of Gβγ by stargazin C-terminus\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vitro binding plus functional oocyte assays, single lab\",\n      \"pmids\": [\"20435886\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Stargazin in cerebellar stellate cells is required for synaptic (but not extrasynaptic) AMPAR trafficking, and for activity-dependent plasticity of synaptic AMPAR rectification at parallel fiber–stellate cell synapses.\",\n      \"method\": \"Electrophysiology in stargazer mutant mice and wild-type controls, philanthotoxin-433 block, rectification index measurements\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic loss-of-function with defined electrophysiological phenotype in specific cell type, single lab\",\n      \"pmids\": [\"21411637\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Calpain activation cleaves/truncates stargazin in rat brain, producing decreased stargazin immunoreactivity in the neuropil, suggesting calpain-mediated regulation of AMPAR targeting through stargazin truncation.\",\n      \"method\": \"Calcium treatment of brain sections, calpain inhibitor, immunocytochemistry, Western blot\",\n      \"journal\": \"Neuroscience\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — pharmacological manipulation in tissue sections, single lab, no direct mechanistic follow-up\",\n      \"pmids\": [\"21256931\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Serine racemase (SR) forms a ternary complex with PSD-95 and stargazin; SR binds stargazin C-terminus, which facilitates SR membrane localization and inhibits SR activity. AMPA receptor activation internalizes SR and disrupts stargazin–SR interaction, derepressing SR activity and increasing D-serine production, potentially coupling AMPA and NMDA receptor activities.\",\n      \"method\": \"Co-immunoprecipitation, enzyme activity assays, subcellular fractionation, AMPAR stimulation in neurons\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP plus enzyme activity plus localization, single lab\",\n      \"pmids\": [\"25164819\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Stargazin links synaptic AMPA and NMDA receptors: synaptic targeting of NMDA receptors in ventral spinal neurons and hippocampal interneurons is dependent on the presence of synaptic AMPARs, with AMPA and NMDA receptors linked by stargazin and a MAGUK protein.\",\n      \"method\": \"Transfection of NR2A/B into spinal neurons, dominant-negative GluR2 mutants, AMPAR/NMDAR clustering assays\",\n      \"journal\": \"Neuron\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic/dominant-negative approach with defined clustering readout, single lab\",\n      \"pmids\": [\"15473971\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Stargazin dephosphorylation during homeostatic synaptic downscaling increases stargazin surface mobility and GluA1-AMPAR mobility at synaptic sites. Stargazin dephosphorylation mediates interaction with AP-2 and AP-3A to promote AMPAR endocytosis and lysosomal degradation; disruption of stargazin–AP-3A interaction prevents GluA1 surface decrease during chronic activity elevation.\",\n      \"method\": \"Single-molecule tracking, competitive peptide inhibitors for AP-2 and AP-3A, surface biotinylation, chronic activity manipulation in cortical neurons\",\n      \"journal\": \"Frontiers in molecular neuroscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — single-molecule tracking plus peptide disruption plus biochemical assays, single lab\",\n      \"pmids\": [\"30271322\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Stargazin (γ-2) slows both channel opening (kop) and closing (kcl) rates of GluA4 homomeric channels by approximately 4-fold and 3-fold, respectively, without appreciable change in channel-opening probability, lengthening the lifetime of open channels and allowing larger charge transfer.\",\n      \"method\": \"Laser-pulse photolysis technique with rapid glutamate application, single-channel kinetic analysis\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstitution with defined kinetic measurements, single lab\",\n      \"pmids\": [\"31267004\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Stargazin enhances the AMPAR response to low concentrations of glutamate; at the cerebellar mossy fiber–unipolar brush cell synapse, recovery from AMPAR desensitization during slow EPSCs is mediated by stargazin enabling receptor responses to declining synaptic glutamate levels.\",\n      \"method\": \"Electrophysiology at identified cerebellar synapses, pharmacological manipulation of AMPAR desensitization and glutamate transporters\",\n      \"journal\": \"Neuron\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — defined synaptic preparation with pharmacological dissection, single lab\",\n      \"pmids\": [\"28919175\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"The C-terminal cytoplasmic tail of stargazin encodes an intrinsic and transferable membrane sorting signal; fusing it to heterologous receptors (GluR1 or GnRH receptor) promotes ER exit and basolateral membrane sorting.\",\n      \"method\": \"Chimeric receptor constructs, confocal imaging of membrane sorting in transfected cells\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single-method confocal imaging, single lab, no functional synaptic readout\",\n      \"pmids\": [\"17986442\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Stargazin-mediated trafficking to the plasma membrane and its modulation of AMPAR gating/desensitization are separable functions requiring different AMPAR domains: the cytoplasmic domain is required for trafficking (FRET interaction in ER) but not for desensitization modulation.\",\n      \"method\": \"FRET between fluorophore-tagged GluR1/GluR2 and stargazin, confocal surface expression imaging, electrophysiology in HEK cells\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — FRET plus electrophysiology, two orthogonal methods, single lab\",\n      \"pmids\": [\"16793768\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"The intellectual disability-associated stargazin V143L mutation weakens the AMPAR:stargazin complex interface (predicted by molecular dynamics), and knock-in mice exhibit impaired spine maturation, abnormal synaptic transmission, impaired LTP specifically in basal dendrites of CA1 neurons, and cognitive/social deficits.\",\n      \"method\": \"Molecular dynamics simulations, knock-in mouse model, dendritic spine imaging, patch-clamp electrophysiology, behavioral testing\",\n      \"journal\": \"Molecular psychiatry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — knock-in mouse with defined cellular and behavioral phenotype plus computational prediction, single lab\",\n      \"pmids\": [\"35256745\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"Stargazin (CACNG2) is an obligate auxiliary subunit of neuronal AMPA receptors that functions through two separable mechanisms: its extracellular/transmembrane domains (primarily M1/M4 of neighboring AMPAR subunits and TM3/TM4 of stargazin itself) allosterically modulate channel gating by destabilizing the closed state and stabilizing the activated/open state, slowing deactivation and desensitization; while its cytoplasmic tail governs receptor trafficking through direct binding to PSD-95 (trapping diffusing AMPAR–stargazin complexes at the synapse) and to adaptor proteins AP-2 and AP-3A (controlling endocytosis and lysosomal routing). Phosphorylation of stargazin by CaMKII/PKC promotes synaptic AMPAR insertion (LTP), dephosphorylation by PP2B/PP1 promotes removal (LTD), and PKA/MAPK phosphorylation at Thr-321 within the PDZ-binding motif dynamically regulates the stargazin–PSD-95 interaction and bidirectional plasticity; additional post-translational regulation by S-nitrosylation and calpain cleavage further modulates AMPAR surface expression.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"Stargazin (CACNG2) is an obligate auxiliary (TARP) subunit of native neuronal AMPA receptor complexes that couples receptor surface delivery, synaptic anchoring, and channel gating into one regulated system [#0, #7]. It acts through two structurally and functionally separable modules: an extracellular/transmembrane interface that allosterically tunes channel behavior, and a cytoplasmic tail that directs trafficking and synaptic localization [#4, #38]. Through its membrane-domain contacts with neighboring AMPAR subunits (M1/M4) and its own TM3/TM4 and extracellular loop 2, stargazin destabilizes the closed channel state and stabilizes the activated/open state, slowing deactivation and desensitization, accelerating recovery, and promoting closure of the ligand-binding domain [#5, #23, #25]; cryo-EM and single-molecule energy-transfer studies place stargazin beneath the AMPAR ligand-binding domain with conserved electrostatic interfaces and variable stoichiometry, supporting a conformational-selection model favoring the activated state [#21, #22]. It additionally relieves intracellular polyamine block of calcium-permeable AMPARs and shapes responses to declining synaptic glutamate, with these effects selective for AMPA over kainate receptors [#13, #36, #28]. The cytoplasmic tail binds the first two PDZ domains of PSD-95, trapping diffusing AMPAR–stargazin complexes at synapses and setting synaptic AMPAR number; disrupting this interaction increases receptor surface diffusion and prevents postsynaptic accumulation [#1, #12]. Glutamate binding allosterically dissociates AMPARs from stargazin, and desensitized receptors bind stargazin more weakly and become more mobile, linking receptor conformational state to synaptic stabilization [#3, #19]. Stargazin phosphorylation controls bidirectional plasticity: CaMKII/PKC phosphorylation and PKA phosphorylation at Thr-321 promote synaptic trapping and AMPAR insertion, while MAPK phosphorylation and PP1/PP2B-mediated dephosphorylation drive removal; phosphorylation extends the tail to engage higher-affinity deep PDZ domains of PSD-95, and PKA phosphorylation of Thr-321 within the PDZ-binding motif disrupts the PSD-95 interaction [#2, #6, #17, #20, #27]. In its dephosphorylated state, stargazin recruits AP-2 and AP-3A adaptors to drive NMDA-induced endocytosis, lysosomal routing, and homeostatic downscaling underlying LTD [#18, #34]. The intellectual-disability-associated V143L mutation weakens the AMPAR:stargazin interface and produces impaired spine maturation, deficient CA1 LTP, and cognitive/social deficits in knock-in mice [#39].\",\n  \"teleology\": [\n    {\n      \"year\": 2000,\n      \"claim\": \"Established stargazin as a dual-function AMPAR partner, resolving how a single auxiliary protein could both deliver receptors to the surface and target them to synapses.\",\n      \"evidence\": \"Co-IP plus transfection rescue in stargazer granule cells and PDZ-binding mutant expression in pyramidal cells\",\n      \"pmids\": [\"11140673\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not define the structural interface of the ectodomain–AMPAR interaction\", \"Did not establish stoichiometry or gating consequences\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Showed that direct stargazin–PSD-95 PDZ binding quantitatively sets synaptic AMPAR number and that PKA phosphorylation at Thr-321 disrupts this interaction, defining a tunable molecular switch for synaptic strength.\",\n      \"evidence\": \"Compensatory PDZ/PDZ-motif mutagenesis with electrophysiology, plus in vitro kinase assay, phospho-specific antibodies and neuronal readouts\",\n      \"pmids\": [\"12359873\", \"12122038\", \"11805122\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not resolve the dynamics of complex trapping versus diffusion\", \"Did not identify the upstream signals coupling activity to PKA phosphorylation in vivo\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Demonstrated that glutamate binding allosterically dissociates AMPARs from a membrane-stable stargazin pool, linking receptor activation to internalization independently of ion flux.\",\n      \"evidence\": \"Surface biotinylation, Co-IP and glutamate stimulation in heterologous cells and neurons\",\n      \"pmids\": [\"15001777\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab\", \"Did not establish whether dissociation is required for endocytosis in vivo\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Separated stargazin's two mechanisms anatomically — ectodomain controls gating (slowed deactivation/desensitization) while the cytoplasmic tail controls trafficking — and confirmed it is a native AMPAR complex subunit required for bidirectional plasticity.\",\n      \"evidence\": \"Domain swaps and mutagenesis with oocyte/HEK and slice electrophysiology, blue native gels of cerebellar complexes, kinase/phosphatase manipulation of LTP/LTD\",\n      \"pmids\": [\"15858532\", \"15758178\", \"16093395\", \"15567474\", \"15664178\", \"15630087\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not provide atomic-resolution view of the gating interface\", \"Did not map all phosphorylation sites to specific plasticity outcomes\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Established that the stargazin–PSD-95 interaction works by trapping laterally diffusing AMPAR–stargazin complexes and that stargazin relieves polyamine block of calcium-permeable AMPARs, connecting molecular interactions to receptor mobility and biophysics.\",\n      \"evidence\": \"Single quantum-dot tracking and FRAP with dominant-negative stargazin; polyamine block analysis in heterologous and stellate cells\",\n      \"pmids\": [\"17329211\", \"17873873\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not resolve how phosphorylation state alters trapping kinetics\", \"Polyamine effect mechanism at the structural level undefined\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Demonstrated that CaMKII activation triggers synaptic AMPAR trapping specifically through stargazin phosphorylation and PDZ scaffold binding, identifying stargazin rather than GluA1 as the phosphorylation substrate for plasticity-driven immobilization.\",\n      \"evidence\": \"Single-particle tracking with CaMKII manipulation, phosphomimetic/null stargazin mutants, short-term plasticity electrophysiology\",\n      \"pmids\": [\"20670832\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not quantify contribution of individual phospho-sites\", \"Did not address other TARP family members in the same pathway\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Identified phosphorylation-state-dependent stargazin–AP-2 and stargazin–AP-3A complexes as the machinery for NMDA-induced endocytosis and lysosomal routing, completing the removal arm of plasticity.\",\n      \"evidence\": \"Co-IP, competitive disruption peptides and LTD electrophysiology in hippocampal neurons\",\n      \"pmids\": [\"24217640\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Single lab for the dual-adaptor model\", \"Did not resolve the structural basis of phospho-dependent adaptor selectivity\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Showed that AMPAR conformational state controls stargazin affinity — desensitized receptors bind less stargazin and become more mobile — and that tail lengthening by phosphorylation engages higher-affinity deep PSD-95 PDZ domains, mechanistically coupling gating to anchoring.\",\n      \"evidence\": \"Single-molecule tracking with conformational-state stabilization; artificial linker insertion and phosphomimetics with synaptic electrophysiology\",\n      \"pmids\": [\"25661182\", \"25843401\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Deep-PDZ model from a single lab\", \"Did not measure in vivo tail extension dynamics\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Provided direct structural mechanism: cryo-EM and energy-transfer studies positioned stargazin below the ligand-binding domain with conserved electrostatic interfaces and variable stoichiometry, supporting a conformational-selection model for activated-state stabilization.\",\n      \"evidence\": \"Cryo-EM of AMPAR–stargazin complexes; LRET/smFRET in HEK293 cells\",\n      \"pmids\": [\"27365450\", \"27705782\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Functional consequence of one-versus-two stargazin stoichiometry unresolved\", \"Cytoplasmic tail interactions not visualized\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Delineated the molecular interface as AMPAR M1/M4 contacts initiated by the C-tail plus TARP TM3/TM4 and extracellular loop 2, with a two-step gating mechanism (destabilize closed state, then stabilize activated state).\",\n      \"evidence\": \"Systematic stargazin/GluK2 domain swaps and TARP chimeras with electrophysiology\",\n      \"pmids\": [\"28238551\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not assign individual residues to each step\", \"Did not address tail-dependent trafficking in the same assay\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Connected stargazin dysfunction to human disease by showing that the V143L mutation weakens the AMPAR:stargazin interface and causes synaptic, plasticity, and behavioral deficits in knock-in mice.\",\n      \"evidence\": \"Molecular dynamics, knock-in mouse with spine imaging, patch-clamp electrophysiology and behavioral testing\",\n      \"pmids\": [\"35256745\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab\", \"Causal link from interface weakening to specific behavioral phenotypes not fully dissected\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How the full repertoire of post-translational modifications (phosphorylation, S-nitrosylation, calpain cleavage) is integrated in vivo to set AMPAR surface levels, and how non-AMPAR functions (CaV2.2/Gβγ modulation, serine racemase regulation) contribute physiologically, remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"S-nitrosylation and calpain regulation rest on single-lab evidence\", \"Non-AMPAR roles (CaV2.2, serine racemase, nPIST, LC2, MAGI-2) not integrated into a unified physiological model\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [5, 23, 4, 13]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [0, 1, 12, 18]},\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [7, 21]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [3, 0, 12]},\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [1, 17]},\n      {\"term_id\": \"GO:0005783\", \"supporting_discovery_ids\": [8, 38]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-112316\", \"supporting_discovery_ids\": [0, 6, 17, 18]},\n      {\"term_id\": \"R-HSA-9609507\", \"supporting_discovery_ids\": [0, 8, 18, 34]},\n      {\"term_id\": \"R-HSA-112315\", \"supporting_discovery_ids\": [5, 23]}\n    ],\n    \"complexes\": [\"AMPA receptor–TARP complex\", \"AMPAR–stargazin–PSD-95 complex\"],\n    \"partners\": [\"GRIA1\", \"GRIA2\", \"DLG4\", \"AP2\", \"AP3\", \"MAGI2\", \"GOPC\", \"SRR\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":9,"faith_total":9,"faith_pct":100.0}}