{"gene":"GPSM2","run_date":"2026-06-10T01:55:21","timeline":{"discoveries":[{"year":1996,"finding":"LGN was identified as a novel protein that interacts with the alpha-subunit of the heterotrimeric GTP-binding protein Gαi2, confirmed by yeast two-hybrid screening and in vitro binding assay using recombinant proteins. LGN contains 10 Leu-Gly-Asn repeats, seven N-terminal repeats (~40 aa each) and four C-terminal repeats (~34 aa each).","method":"Yeast two-hybrid screen; in vitro binding assay with recombinant proteins","journal":"Gene","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — yeast two-hybrid plus in vitro binding assay in a single study, two orthogonal methods","pmids":["8973305"],"is_preprint":false},{"year":2000,"finding":"Drosophila Pins (ortholog of LGN/GPSM2) was identified as a binding partner of Inscuteable and a Gα subunit in vivo, localizing to the apical cortex of neuroblasts. In pins mutants, spindle orientation and basal localization of Numb/Miranda were defective, and Inscuteable lost its apical localization during mitosis, establishing Pins as essential for asymmetric cell division.","method":"In vivo co-immunoprecipitation; genetic loss-of-function (pins mutants); immunofluorescence localization","journal":"Current biology : CB","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP in vivo, genetic mutant phenotypes, replicated across multiple experimental approaches in a foundational study","pmids":["10753746"],"is_preprint":false},{"year":2002,"finding":"LGN binds with high affinity to the C-terminal tail of NuMA. A small domain within the C terminus of NuMA stabilizes microtubules in vitro, and LGN blocks this stabilization by steric exclusion, as the MT-binding domain on NuMA overlaps by ten amino acid residues with the LGN-binding domain.","method":"In vitro microtubule stabilization assay; frog egg extracts; in vitro binding assays; domain mapping","journal":"Current biology : CB","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro reconstitution assays with defined domain overlap and functional consequence, multiple orthogonal methods in single study","pmids":["12445386"],"is_preprint":false},{"year":2002,"finding":"LGN localizes to the midbody structure separating daughter cells during the later stages of mitosis in PC12 and COS7 cells, moving from the nucleus to the midbody during cytokinesis. Its subcellular localization is differentially regulated by the cell cycle compared to the closely related AGS3.","method":"Immunocytochemistry; cell fractionation; expression of LGN-specific antisera","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — immunocytochemical localization in multiple cell types, single lab but consistent across conditions","pmids":["11832491"],"is_preprint":false},{"year":2003,"finding":"Mouse PINS (LGN/GPSM2 ortholog) can asymmetrically localize to the apical cortex of Drosophila neuroblasts when ectopically expressed, and can functionally substitute for Drosophila Pins in all aspects of neuroblast asymmetric cell division. The N-terminal TPR domain directly interacts with the asymmetric localization domain of Inscuteable, and the C-terminal GoLoco region directs cortical localization.","method":"Ectopic expression in Drosophila neuroblasts; direct binding assay; genetic rescue experiments","journal":"Journal of cell science","confidence":"High","confidence_rationale":"Tier 2 / Strong — direct binding assay, genetic rescue of null mutant, and localization experiments; demonstrates conservation of function","pmids":["12571286"],"is_preprint":false},{"year":2003,"finding":"In C. elegans, GPR-1 and GPR-2 (homologs of mammalian AGS3/LGN and Drosophila Pins) control spindle position by acting as GDP dissociation inhibitors (GDI) for GOA-1 (Gαo). LIN-5 (NuMA homolog) binds GPR proteins and is required for their cortical association. GPR proteins are enriched at the posterior cortex in a PAR-dependent manner, generating asymmetric pulling forces on spindle poles.","method":"RNAi depletion; GDI fluorescence assay; Co-IP; genetic epistasis","journal":"Current biology : CB","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — biochemical GDI assay, Co-IP, and genetic epistasis in a key model organism study","pmids":["12814548"],"is_preprint":false},{"year":2003,"finding":"LGN exhibits enriched cortical localization during mitosis in certain mammalian cell lines (WISH, PC12, NRK but not COS cells). The Gα-binding C-terminal portion of LGN is sufficient for cortical localization. Cortical localization depends on microfilaments, and overexpression of Gα subunits can redirect LGN to the cortex in COS cells. Interfering with LGN function disrupts cell cycle progression.","method":"Overexpression of LGN domain truncations; immunofluorescence; cytochalasin D treatment; dominant-negative experiments","journal":"Molecular biology of the cell","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — multiple cell lines and domain mapping, single lab, consistent results across conditions","pmids":["12925752"],"is_preprint":false},{"year":2004,"finding":"Mammalian LGN (GPSM2) acts as a conformational switch: in its closed (autoinhibited) state, the N-terminal (TPR) and C-terminal (GoLoco) domains interact intramolecularly. NuMA or Gαi can disrupt this autoinhibitory interaction, allowing LGN to simultaneously bind both proteins and recruit them to the cell cortex. During mitosis, LGN recruits NuMA to the cell cortex; cortical association of LGN requires Gα binding. Overexpression of Gαi or YFP-LGN causes metaphase spindle oscillation.","method":"FRET biosensor; Co-immunoprecipitation; live cell imaging; overexpression","journal":"Cell","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — FRET biosensor directly measures conformational change, reciprocal Co-IP, live imaging; multiple orthogonal methods in one study","pmids":["15537540"],"is_preprint":false},{"year":2005,"finding":"GPSM2 GoLoco motifs 1-4 all function as guanine nucleotide dissociation inhibitors (GDIs) for Gαi1, Gαi2, and Gαi3, but display significantly lower GDI activity and binding affinity for Gαo. Surface plasmon resonance binding assays showed all four GoLoco motifs bind Gαi1 but not Gαs, establishing Gαi subunits as the primary in vivo targets.","method":"Surface plasmon resonance; fluorescence-based nucleotide binding (GDI) assay; recombinant GST-fusion proteins","journal":"Biochimica et biophysica acta","confidence":"High","confidence_rationale":"Tier 1 / Strong — quantitative in vitro biochemical assays with purified proteins, two orthogonal methods (SPR + fluorescence GDI assay)","pmids":["15946753"],"is_preprint":false},{"year":2005,"finding":"In Drosophila neuroblasts, astral microtubules, kinesin Khc-73, and Discs large (Dlg) induce cortical polarization of Pins/Gαi; Dlg/Khc-73 and Dlg/Pins co-immunoprecipitate, suggesting Dlg mediates the link between microtubules and Pins/Gαi cortical polarity. This microtubule/Khc-73/Dlg pathway acts in parallel to the Inscuteable/Par pathway.","method":"Co-immunoprecipitation; live imaging; genetic loss-of-function; immunofluorescence","journal":"Cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — Co-IP, genetic epistasis with multiple mutants, and live imaging; multiple orthogonal approaches","pmids":["16377571"],"is_preprint":false},{"year":2005,"finding":"Mammalian Ric-8A catalytically dissociates Gαi-GDP/LGN/NuMA complexes in vitro, releasing activated Gαi-GTP and concomitantly liberating NuMA from LGN. This establishes a mechanism whereby Ric-8A GEF activity for Gαi regulates the LGN-NuMA interaction during cell division.","method":"In vitro biochemical dissociation assay with purified proteins; fluorescence-based GTPase assay","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro reconstitution with purified proteins demonstrating catalytic mechanism","pmids":["16275912"],"is_preprint":false},{"year":2005,"finding":"LGN is expressed in photoreceptor inner segments and co-localizes with transducin α (Gαt) following its light-dependent translocation. LGN and Gαt co-precipitate from retinal extracts, and the GPR domain of LGN potently inhibits receptor-mediated guanine nucleotide exchange and GTPase activity of transducin, identifying a role for LGN in modulating transducin function in photoreceptors.","method":"Immunostaining; serial tangential sectioning with immunoblot; co-precipitation; in vitro GDI/GTPase inhibition assay","journal":"Molecular and cellular neurosciences","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-precipitation plus functional in vitro assay, single lab","pmids":["15737739"],"is_preprint":false},{"year":2005,"finding":"LGN directly binds Lgl2 (mammalian homolog of Drosophila l(2)gl) with Kd ~56 nM via the C-terminal tail of Lgl2. Endogenous Lgl2 forms a complex with aPKC, Par-6, and LGN, enhanced during metaphase. Overexpression of Lgl2 C-terminal tail mislocalized NuMA and disorganized the mitotic spindle; knockdown of Lgl1/2 caused spindle disorganization and micronuclei formation, mediated through regulation of the LGN-NuMA complex.","method":"Co-immunoprecipitation; in vitro binding with Kd measurement; siRNA knockdown; immunofluorescence","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — quantitative binding assay, reciprocal Co-IP, RNAi knockdown with defined phenotype, multiple orthogonal methods","pmids":["15632202"],"is_preprint":false},{"year":2006,"finding":"Drosophila Pins (LGN ortholog) directly binds and co-immunoprecipitates with the NuMA-related Mushroom body defect (Mud) protein. Pins recruits Mud to the neuroblast apical cortex; in mud mutants, spindle alignment with cortical polarity is lost. This establishes a direct Pins-Mud interaction linking cortical polarity to spindle orientation.","method":"Direct binding assay; co-immunoprecipitation; genetic loss-of-function (mud mutants); immunofluorescence","journal":"Nature cell biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — direct binding assay, reciprocal Co-IP, and genetic loss-of-function with defined phenotype; replicated in companion paper (PMID:16648846)","pmids":["16648843","16648846"],"is_preprint":false},{"year":2006,"finding":"LGN modulates GIRK channel activity in a Gαi/Go-dependent manner: LGN increases basal GIRK current but reduces receptor-activated GIRK currents. This effect is mediated through the N-terminal TPR domain of LGN, which likely releases sequestered endogenous LGN. In hippocampal neurons, LGN hyperpolarizes resting potential through increased basal GIRK activity; LGN RNAi reduces basal GIRK activity.","method":"Electrophysiology (patch-clamp); LGN domain overexpression; lentiviral RNAi in hippocampal neurons","journal":"Neuron","confidence":"High","confidence_rationale":"Tier 2 / Strong — electrophysiological functional assay combined with domain overexpression and RNAi knockdown; multiple orthogonal approaches","pmids":["16701207"],"is_preprint":false},{"year":2006,"finding":"In Drosophila neuroblasts, Loco (a GoLoco protein) and Pins act synergistically as GDIs for Gαi to release free Gβγ, which is required for asymmetric spindle and daughter cell size. Simultaneous removal of Loco and Pins phenocopies Gβ13F or Gγ1 mutants. Loco's RGS domain also accelerates GTPase activity of Gαi, providing a second mode of regulation.","method":"Genetic epistasis (double mutants); in vitro GDI assay; RGS GTPase acceleration assay","journal":"Genes & development","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — biochemical GDI and GTPase assays combined with genetic epistasis in multiple mutant backgrounds","pmids":["15937221"],"is_preprint":false},{"year":2007,"finding":"Drosophila Pins (LGN ortholog) forms a 'closed' autoinhibited state via intramolecular GoLoco-TPR interactions. Gαi binding to GoLoco 1 (GL1) recruits Pins to the apical cortex without opening Pins or recruiting Mud. Gαi and Mud bind cooperatively to GL2/3 and TPR domains respectively, activating the full spindle orientation pathway. These multiple activity states link cortical polarity to spindle orientation.","method":"Biochemical binding assays; genetic epistasis; live imaging; domain mutant analysis","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — multiple orthogonal methods including biochemistry, genetics, and live imaging; defines molecular mechanism with domain precision","pmids":["17726110"],"is_preprint":false},{"year":2007,"finding":"LGN (GPSM2) is required for planar divisions in chick neuroepithelium; it localizes at the cell cortex and spindle poles of neural progenitors. Interfering with LGN function randomizes the division plane, causing one daughter to exit the neuroepithelium prematurely and proliferate aberrantly, without affecting cell fate. This demonstrates LGN controls spindle movements/orientation in vertebrate neural progenitors.","method":"In ovo electroporation (dominant-negative LGN); immunofluorescence; BrdU lineage analysis","journal":"Nature neuroscience","confidence":"High","confidence_rationale":"Tier 2 / Strong — loss-of-function with specific cellular phenotype, localization, replicated by companion paper (PMID:18084280)","pmids":["17934458"],"is_preprint":false},{"year":2007,"finding":"Knockout of LGN (GPSM2) in mouse neuroepithelial cells randomizes the orientation of normally planar cell divisions, causing loss of the apical membrane from some daughter cells and converting them into abnormally localized progenitors, without affecting neuronal production rate. LGN is dispensable for the proliferation vs. differentiation decision but essential for maintaining neuroepithelial self-renewal via planar spindle orientation.","method":"LGN conditional knockout (gene targeting); BrdU/EdU labeling; immunofluorescence; clonal analysis","journal":"Nature cell biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — knockout mouse model with defined cellular phenotype, mechanistic link to apical membrane inheritance","pmids":["18084280"],"is_preprint":false},{"year":2010,"finding":"A nonsense mutation in GPSM2 (early truncation) causes nonsyndromic hearing loss DFNB82 in humans. In mouse inner ear, GPSM2 is localized to apical surfaces of hair cells and supporting cells, most highly expressed during embryonic development, establishing GPSM2 as essential for normal hearing development.","method":"Whole exome sequencing; homozygosity mapping; immunolocalization in mouse inner ear","journal":"American journal of human genetics","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — human genetics identifying causative mutation plus immunolocalization; functional mechanism inferred from localization and known protein function","pmids":["20602914"],"is_preprint":false},{"year":2010,"finding":"During epithelial mitosis, Par3/aPKC excludes LGN (Pins) from the apical cortex by aPKC-mediated phosphorylation of Pins on Ser401, which recruits 14-3-3 protein. 14-3-3 binding inhibits Pins association with Gαi, causing Pins to dissociate from the apical cortex. A Pins S401A mutant mislocalizes over the entire cortex and causes spindle misorientation and multi-lumen cysts.","method":"siRNA knockdown; phosphorylation site mutagenesis (S401A); 14-3-3 binding assay; 3D cyst culture; immunofluorescence","journal":"Current biology : CB","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — phosphosite mutagenesis, binding assay, and functional rescue/phenotypic assay in 3D culture; multiple orthogonal methods","pmids":["20933426"],"is_preprint":false},{"year":2010,"finding":"LGN localizes to the lateral cell cortex (excluded from apical cortex) of dividing MDCK cells. Depleting LGN, preventing cortical localization, or disrupting its interaction with NuMA or Gα proteins causes spindle misorientation and abnormal cystogenesis (multiple lumens). Apical exclusion of LGN is mediated by aPKC. Artificial mistargeting of LGN to the apical membrane rotates the spindle ~90° and disrupts cystogenesis.","method":"siRNA knockdown; dominant-negative constructs; apical membrane targeting of LGN; 3D cyst culture; immunofluorescence","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple loss-of-function approaches, gain-of-function mistargeting, defined morphogenetic phenotype; multiple orthogonal methods","pmids":["20385777"],"is_preprint":false},{"year":2010,"finding":"Ric-8A and Gαi cooperate to recruit LGN (GPSM2), NuMA, and dynein to the cell cortex of mammalian cells during mitosis. Pertussis toxin (blocking Ric-8A-Gαi interaction), Ric-8A knockdown, or Gαi knockdown each impaired cortical localization of LGN, NuMA, and dynein, and disturbed integrin-dependent mitotic spindle orientation. Reduced Ric-8A prolonged mitosis and decreased spindle movements.","method":"siRNA knockdown; pertussis toxin treatment; immunofluorescence; live imaging (GFP-tubulin HeLa cells)","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple independent perturbations (toxin, RNAi) converging on same phenotype, live imaging, multiple orthogonal methods","pmids":["20479129"],"is_preprint":false},{"year":2010,"finding":"GPSM2 (LGN) is phosphorylated on Thr450 by the serine/threonine kinase PBK/TOPK during mitosis. LGN/GPSM2 localizes to the spindle at metaphase and to the midzone/midbody in cytokinesis. Overexpression of the T450A phospho-dead mutant induces aberrant chromosomal segregation and growth suppression of breast cancer cells; siRNA knockdown of GPSM2 causes incomplete cell division.","method":"Western blot (phospho-specific); siRNA knockdown; T450A mutant overexpression; immunocytochemistry; synchronization assays","journal":"Genes, chromosomes & cancer","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — kinase-substrate identification with phosphomimetic mutant phenotype, single lab","pmids":["20589935"],"is_preprint":false},{"year":2011,"finding":"Crystal structures of LGN in complex with NuMA and mInsc (mammalian Inscuteable) reveal that NuMA and mInsc interact with LGN TPR domain through distinct but overlapping interfaces. Structural and biochemical studies demonstrate that NuMA and mInsc binding to LGN are mutually exclusive, with mInsc binding preferentially (higher affinity). This suggests Par3/mInsc/LGN and NuMA/LGN/Gαi complexes play sequential and partially overlapping roles.","method":"X-ray crystallography; isothermal titration calorimetry; competitive binding assays; cell biology (localization studies)","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 1 / Strong — high-resolution crystal structures with functional validation by ITC and competition assays; multiple orthogonal methods","pmids":["21816348"],"is_preprint":false},{"year":2011,"finding":"Crystal structure of Drosophila Pins (LGN ortholog) TPR domain in complex with Inscuteable reveals modular binding interface with three contact modules on Insc running antiparallel to the TPR superhelix. Structure-based mutagenesis defines critical residues. mInsc binds LGN with highest affinity (Kd ~2.4 nM), effectively displacing NuMA and other interactors; mInsc-LGN interaction is required for stabilization of LGN and intracellular localization of mInsc.","method":"X-ray crystallography (2.6 Å); structure-based mutagenesis; isothermal titration calorimetry; cell biology","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1 / Strong — atomic-resolution crystal structure with mutagenesis validation and quantitative binding measurements","pmids":["22074847"],"is_preprint":false},{"year":2011,"finding":"Crystal structure of Drosophila Pins (LGN ortholog) in complex with Inscuteable, combined with in vitro competition assays, demonstrates that Insc competes with NuMA for LGN TPR binding and has higher affinity. Insc can open the LGN conformational switch. The positively charged EPE-motif contact patch on LGN is shared by both Insc and NuMA.","method":"X-ray crystallography; in vitro competition assays; isothermal titration calorimetry","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure plus quantitative in vitro competition assays; replicates findings from companion papers with orthogonal approach","pmids":["22171003"],"is_preprint":false},{"year":2011,"finding":"LGN and NuMA form a lateral belt at the cortex of chick neuroepithelial cells during metaphase. FRAP and live imaging show LGN/NuMA cortical localization is dynamic. The LGN/NuMA/Gαi complex is required for active spindle movements and planar maintenance of the spindle. Lateral restriction of LGN/NuMA is instructive for planar spindle alignment.","method":"3D live imaging; FRAP; immunofluorescence; dominant-negative LGN; siRNA","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — live imaging with FRAP demonstrating dynamics, multiple loss-of-function approaches, defined spindle orientation phenotype","pmids":["21444683"],"is_preprint":false},{"year":2011,"finding":"In Drosophila, Wee B/Canoe directly binds the Pins TPR domain; this interaction recruits Canoe to the cortex and is required for activation of the Pins(TPR)-Mud spindle orientation pathway. Canoe RA domains bind RanGTP, and both Canoe(RA) domains and RanGTP are required to recruit Mud to the cortex and activate spindle orientation.","method":"Direct binding assay; induced cell polarity system; genetic epistasis; immunofluorescence","journal":"The Journal of cell biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct binding assay and genetic epistasis with defined pathway, single lab","pmids":["22024168"],"is_preprint":false},{"year":2012,"finding":"Mutations in GPSM2 (two single-base deletions, one nonsense mutation, one splice-site mutation) cause Chudley-McCullough syndrome (CMS), characterized by sensorineural hearing loss and brain malformations including frontal polymicrogyria, corpus callosum agenesis, and gray matter heterotopia. This links GPSM2 function in mitotic spindle orientation to the etiology of brain malformations and hearing loss.","method":"Homozygosity mapping; whole-exome sequencing; brain imaging of affected individuals","journal":"American journal of human genetics","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — human genetics identifying multiple independent causative mutations; functional mechanism inferred from known GPSM2 biology","pmids":["22578326"],"is_preprint":false},{"year":2012,"finding":"Crystal structures of LGN GoLoco 3 (GL3) and GL4 in complex with Gαi·GDP reveal the structural basis of GoLoco/Gαi interaction. A highly conserved 'double Arg finger' sequence (RΨ(D/E)(D/E)QR) is responsible for GDP binding. Only a few residues C-terminal to the conserved GL sequence are required for Gαi·GDP interaction. LGN C-terminal GL domain binds four Gαi·GDP molecules; all four GL motifs are potent GDIs.","method":"X-ray crystallography; isothermal titration calorimetry; fluorescence-based GDI assay","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — atomic-resolution crystal structures with functional validation; defines GDI mechanism at molecular level","pmids":["22952234"],"is_preprint":false},{"year":2013,"finding":"The crystal structure of a truncated LGN reveals its autoinhibited conformation: two consecutive GoLoco (GL) motifs (GL12 or GL34) form minimal TPR-binding units, with GL34 forming parallel α-helices that bind the concave surface of TPR4-7, preventing LGN from binding other targets. GL motifs bind TPRs by a mode distinct from GL/Gαi·GDP interactions.","method":"X-ray crystallography; binding assays; domain truncation analysis","journal":"Structure (London, England : 1993)","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure revealing distinct binding mode with functional implications; multiple domain constructs tested","pmids":["23665171"],"is_preprint":false},{"year":2013,"finding":"LGN associates with cytoplasmic dynein heavy chain (DYNC1H1) in a Gαi-regulated manner. LGN is required for mitotic cortical localization of dynein, which in turn also modulates cortical LGN accumulation. FRAP analysis shows cortical LGN is dynamic and turns over via astral microtubule- and dynein-dependent transport. Actin filaments counteract dynein-mediated cortical release of Gαi/LGN/NuMA, maintaining cortical retention.","method":"Co-immunoprecipitation; FRAP; siRNA knockdown; cytoskeletal drug treatments; immunofluorescence","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP, FRAP dynamics, and multiple perturbation experiments; several orthogonal methods in one study","pmids":["23389635"],"is_preprint":false},{"year":2013,"finding":"Par1b promotes the apicolateral accumulation of LGN and capture of NuMA-positive astral microtubules in mitotic hepatocytes to orient the mitotic spindle, resulting in asymmetric inheritance of apical plasma membrane domains between daughter cells.","method":"siRNA knockdown; immunofluorescence; live imaging; 3D culture","journal":"PLoS biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional knockdown with spindle orientation and polarity phenotype, single lab","pmids":["24358023"],"is_preprint":false},{"year":2014,"finding":"Direct interaction between Dlg1 and LGN promotes cortical localization of the LGN complex and is required for planar spindle orientation in the chick neuroepithelium and human cells on adhesive micropatterns. Live imaging shows Dlg1 is required for directed spindle movements during metaphase.","method":"Direct binding assay; siRNA knockdown; live imaging; immunofluorescence; dominant-negative experiments","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — direct binding assay, RNAi, live imaging, and defined spindle orientation phenotype; multiple orthogonal methods","pmids":["25202028"],"is_preprint":false},{"year":2014,"finding":"Par3, mInsc, and Gαi3 cooperate to polarize LGN and promote perpendicular (asymmetric) divisions in murine epidermis. Loss of both Gnai3 and mInsc phenocopies loss of LGN (mostly planar divisions), demonstrating that Par3-mInsc and Gαi3 act cooperatively upstream of LGN to control its apical localization and division orientation.","method":"Conditional knockouts; in vivo lentiviral RNAi; immunofluorescence; division angle quantification","journal":"Nature cell biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple in vivo genetic perturbations with epistasis, defined phenotypic readout","pmids":["25016959"],"is_preprint":false},{"year":2014,"finding":"SLK kinase directly activates ERM proteins (ezrin/radixin/moesin) at mitotic entry in mammalian cells. Activated ERMs promote polarized cortical association of LGN and NuMA, which is required for spindle orientation. Impairing ERM activation in apical progenitors of the mouse embryonic neocortex severely disturbs spindle orientation in vivo.","method":"siRNA knockdown; phospho-specific antibodies; micropatterned adhesive substrates; in vivo mouse neocortex experiments; immunofluorescence","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vitro and in vivo loss-of-function with defined LGN/NuMA localization phenotype; multiple orthogonal approaches","pmids":["24958772"],"is_preprint":false},{"year":2015,"finding":"The GoLoco motifs of GPSM2/LGN are essential for hearing. Mice with truncation of the C-terminal GoLoco motifs (LgnΔC) are profoundly deaf, show hair bundle misorientation and severe stereocilia malformations. Gαi and aPKC depend on LGN for proper localization in hair cells. LGN functions as a PCP effector downstream of core PCP proteins; kinocilium positioning is required for LGN/Gαi/aPKC apical localization.","method":"Mouse knockout (targeted GoLoco truncation); auditory brainstem response; scanning EM; immunofluorescence; in vitro translation","journal":"Mammalian genome","confidence":"High","confidence_rationale":"Tier 2 / Strong — defined mouse knockout, functional hearing assay, mechanistic epistasis with Gαi and aPKC localization","pmids":["26662512"],"is_preprint":false},{"year":2016,"finding":"Afadin directly and concomitantly binds both F-actin and LGN. Crystal structure of human Afadin in complex with LGN reveals structural similarity to the LGN-NuMA complex. In mitosis, Afadin is necessary for cortical accumulation of LGN and NuMA above spindle poles in an F-actin-dependent manner. Afadin acts as a molecular hub anchoring the dynein/LGN/NuMA machinery to cortical F-actin.","method":"X-ray crystallography; direct binding assays; siRNA knockdown; 3D cyst culture; immunofluorescence","journal":"Nature structural & molecular biology","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure of complex with functional validation by multiple binding and cell biology assays","pmids":["26751642"],"is_preprint":false},{"year":2016,"finding":"SAPCD2 is a novel LGN-interacting protein that negatively regulates LGN cortical localization, likely by competing with NuMA for LGN binding. Loss of SAPCD2 randomizes spindle orientation in epithelial cells and retinal progenitors in vivo, and triples the number of asymmetric terminal divisions in the developing retina.","method":"Co-immunoprecipitation; siRNA knockdown; in vivo mouse retinal experiments; division angle quantification; immunofluorescence","journal":"Developmental cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — Co-IP, competition binding, in vitro and in vivo loss-of-function with quantitative phenotypic analysis","pmids":["26766442"],"is_preprint":false},{"year":2017,"finding":"E-cadherin functions as an instructive cue for division orientation by directly binding LGN at cell-cell adhesions. LGN adopts a 3D structure similar to cadherin-bound catenins and binds the E-cadherin cytosolic tail. On mitotic entry, NuMA competes LGN from E-cadherin to locally form the LGN/NuMA complex, stabilizing cortical astral microtubule associations at adhesions to orient the spindle.","method":"Direct binding assay; immunofluorescence; siRNA knockdown; competition assay (NuMA vs E-cadherin for LGN)","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 / Strong — direct binding, competition assay, and functional RNAi knockdown with defined division orientation phenotype","pmids":["28045117"],"is_preprint":false},{"year":2017,"finding":"Phosphorylation of VE-cadherin Y658 by Src-family kinases induces dissociation of p120ctn, enabling LGN to bind the VE-cadherin cytoplasmic tail at endothelial cell junctions. LGN binding to phospho-Y658 VE-cadherin is required for multiple endothelial flow responses including inflammatory signaling at disturbed flow and flow-dependent vascular remodeling.","method":"Phosphomimetic and phospho-dead VE-cadherin mutants; Co-IP; siRNA knockdown; in vivo vascular remodeling assays","journal":"Current biology : CB","confidence":"High","confidence_rationale":"Tier 2 / Strong — phosphosite-specific mutants, Co-IP, and in vitro/in vivo functional assays; multiple orthogonal methods","pmids":["28712573"],"is_preprint":false},{"year":2017,"finding":"GPSM2 (Gpsm2) and its partner Gαi3 define an ~200 nm nanodomain at stereocilia tips in auditory and vestibular hair cells. Gpsm2 localization at stereocilia tips requires Gαi3, myosin 15 (Myo15a), and whirlin (Whrn). Loss of Gpsm2 disrupts stereocilia elongation and actin dynamics in growth cones (shown by single-molecule tracking). Absence of Gpsm2 or Gαi3 causes deafness and balance defects.","method":"Mouse knockout; single-molecule tracking (live imaging); STED nanoscopy; auditory/vestibular functional assays; genetic epistasis","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 / Strong — knockout mouse, single-molecule tracking, nanoscopy, genetic epistasis; multiple rigorous orthogonal methods","pmids":["28387217"],"is_preprint":false},{"year":2018,"finding":"Crystal structure of Drosophila LGN (Pins) in complex with the asymmetric domain of Inscuteable reveals a tetrameric arrangement of intertwined molecules. Insc:LGN tetramers form stable cores of Par3-Insc-LGN-GαiGDP complexes that cannot be dissociated by NuMA. In mammary stem cells, Insc bound to LGN:GαiGDP drives asymmetric fate and reverts aberrant symmetric divisions induced by p53 loss, independent of microtubule motor recruitment.","method":"X-ray crystallography; SEC-SAXS; in vitro complex stability assay; mammary stem cell functional assays; RNAi","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure plus SAXS validation in solution, and functional in vivo/in vitro stem cell assays","pmids":["29523789"],"is_preprint":false},{"year":2019,"finding":"GPSM2-GNAI forms a module that confers first-row (tallest stereocilia) identity in the hair bundle. WHRN-GPSM2-GNAI is an extra module recruited to a pre-existing MYO15A-EPS8 complex only in the first (tallest) row. GPSM2 and GNAI are required to stabilize larger amounts of MYO15A-EPS8 in tall-row stereocilia. In GPSM2 or GNAI mutants, bundles retain an embryonic-like generic stereocilia organization. Genetic epistasis demonstrates GPSM2, GNAI, MYO15A, and WHRN operate in series in the same pathway.","method":"Comprehensive genetic epistasis in mouse auditory epithelium; immunofluorescence; time-course protein distribution analysis in multiple mutant backgrounds","journal":"Current biology : CB","confidence":"High","confidence_rationale":"Tier 2 / Strong — comprehensive genetic epistasis across multiple mutants with systematic protein localization analysis; defines pathway order","pmids":["30827920"],"is_preprint":false},{"year":2011,"finding":"In Drosophila, robust spindle alignment by Pins (LGN) is achieved through ultrasensitive activation by Gαi (apparent Hill coefficient 3.1). GoLoco domains GL1 and GL2 act as 'decoys' competing against activation at GL3, generating ultrasensitivity and ensuring Pins-Mud (NuMA) recruitment occurs over a narrow Gαi concentration range. A non-ultrasensitive Pins mutant fails to robustly couple spindle position to cell polarity in neuroblasts.","method":"Reconstituted spindle orientation pathway assay; Hill coefficient analysis; domain mutant neuroblast experiments","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro reconstituted pathway with quantitative dose-response analysis plus in vivo mutant validation","pmids":["21855794"],"is_preprint":false}],"current_model":"GPSM2 (LGN) is a conformational switch protein that, in its autoinhibited state, has intramolecular GoLoco-TPR interactions; binding of Gαi-GDP to its C-terminal GoLoco motifs (where it acts as a GDI) releases autoinhibition and allows the N-terminal TPR domain to simultaneously recruit NuMA and/or mInscuteable, thereby assembling a cortical Gαi/LGN/NuMA complex that captures astral microtubules and orients the mitotic spindle; LGN cortical localization is restricted to lateral/basal domains by aPKC-mediated phosphorylation (Ser401) recruiting 14-3-3 to displace Gαi binding, and is further regulated by Ric-8A (which catalytically releases Gαi-GTP from the complex), dynein-dependent cortical transport, E-cadherin/Afadin/Dlg1-mediated anchoring, and ERM-dependent actin linkage; in the inner ear, GPSM2-GNAI localizes to stereocilia tips in a nanodomain requiring Myo15a and whirlin, where it specifies tallest-row (first-row) stereocilia identity and regulates actin dynamics for elongation."},"narrative":{"mechanistic_narrative":"GPSM2 (LGN/Pins) is a conformational-switch scaffold that couples cell cortical polarity to mitotic spindle orientation during asymmetric and oriented cell division [PMID:10753746, PMID:15537540, PMID:17934458]. Its C-terminal GoLoco motifs act as guanine-nucleotide dissociation inhibitors (GDIs) selective for Gαi-GDP over Gαo/Gαs, binding up to four Gαi·GDP molecules through a conserved double-Arg-finger motif [PMID:15946753, PMID:22952234], while its N-terminal TPR domain recruits the NuMA C-terminus and mInscuteable through distinct but overlapping interfaces [PMID:12445386, PMID:21816348]. In the autoinhibited closed state, the GoLoco motifs fold back onto the TPR concave surface to occlude target binding; Gαi engagement of the GoLoco motifs relieves this intramolecular interaction, permitting simultaneous assembly of a cortical Gαi/LGN/NuMA complex that captures astral microtubules and generates spindle-pulling forces [PMID:15537540, PMID:17726110, PMID:23665171]. NuMA and mInsc bind LGN mutually exclusively, with mInsc binding at highest affinity to displace NuMA and route LGN into Par3/mInsc-based asymmetric-fate complexes, establishing a switch between symmetric/oriented and asymmetric division programs [PMID:21816348, PMID:22074847, PMID:29523789]. Cortical positioning of LGN is spatially restricted by aPKC-mediated Ser401 phosphorylation that recruits 14-3-3 to block Gαi binding [PMID:20933426], and the complex is dynamically tuned by Ric-8A, which catalytically dissociates Gαi-GDP/LGN/NuMA and releases NuMA [PMID:16275912, PMID:20479129], by dynein- and astral-microtubule-dependent cortical turnover counterbalanced by actin [PMID:23389635], and by cortical anchors including Dlg1, Afadin/F-actin, E-cadherin and SLK-activated ERM proteins [PMID:25202028, PMID:26751642, PMID:28045117, PMID:24958772]. Through this machinery LGN governs planar versus perpendicular divisions in neuroepithelium and epidermis, controlling progenitor self-renewal and apical-membrane inheritance [PMID:17934458, PMID:18084280, PMID:25016959]. In the inner ear, a WHRN–GPSM2–GNAI module localizes to a stereocilia-tip nanodomain dependent on MYO15A and whirlin and confers tallest (first-row) stereocilia identity by stabilizing the MYO15A-EPS8 complex and regulating actin elongation [PMID:28387217, PMID:30827920]. Truncating GPSM2 mutations cause nonsyndromic deafness DFNB82 and Chudley-McCullough syndrome, directly linking its spindle-orientation and stereocilia functions to human hearing loss and brain malformation [PMID:20602914, PMID:22578326].","teleology":[{"year":1996,"claim":"Established the founding molecular link by identifying LGN as a Gαi-interacting protein, defining its repeat architecture and pointing to heterotrimeric G-protein regulation as its biochemical context.","evidence":"Yeast two-hybrid screen and in vitro binding with recombinant Gαi2","pmids":["8973305"],"confidence":"Medium","gaps":["No functional consequence of the interaction defined","No distinction between TPR and GoLoco repeat functions"]},{"year":2000,"claim":"Placed the protein in a biological process by showing the Drosophila ortholog Pins is essential for asymmetric cell division, bridging Inscuteable/Gα to spindle orientation in vivo.","evidence":"In vivo Co-IP, pins loss-of-function mutants, and localization in neuroblasts","pmids":["10753746"],"confidence":"High","gaps":["Mechanism of how Pins links polarity to spindle not defined","Mammalian conservation not yet tested"]},{"year":2002,"claim":"Identified NuMA as a high-affinity TPR partner and showed LGN modulates NuMA-dependent microtubule stabilization, providing a direct molecular route from LGN to the spindle.","evidence":"In vitro microtubule stabilization assay, frog egg extracts, and domain mapping","pmids":["12445386"],"confidence":"High","gaps":["Cortical assembly not yet reconstituted","Regulation of LGN-NuMA binding unknown"]},{"year":2003,"claim":"Demonstrated functional conservation and domain division of labor: mammalian PINS rescues fly neuroblast division, with the TPR binding Inscuteable and the GoLoco region directing cortex localization.","evidence":"Ectopic expression and genetic rescue in Drosophila neuroblasts plus direct binding assays","pmids":["12571286","12814548"],"confidence":"High","gaps":["GDI biochemistry quantified only for worm GPR proteins","Mammalian cortical recruitment mechanism not yet shown"]},{"year":2004,"claim":"Defined the central mechanistic principle—LGN is an autoinhibited conformational switch whose opening by Gαi or NuMA enables simultaneous binding and cortical recruitment of partners.","evidence":"FRET biosensor, reciprocal Co-IP, and live-cell imaging in mammalian cells","pmids":["15537540"],"confidence":"High","gaps":["Structural basis of the closed state not resolved","Spatial restriction of cortical LGN not addressed"]},{"year":2005,"claim":"Quantified GoLoco GDI activity and substrate selectivity, establishing Gαi (not Gαo/Gαs) as the physiological target and clarifying the biochemical output of the C-terminus.","evidence":"Surface plasmon resonance and fluorescence GDI assays with recombinant GoLoco motifs","pmids":["15946753","16275912","15937221"],"confidence":"High","gaps":["Stoichiometry and cooperativity among the four motifs not yet resolved","Coupling of GDI activity to switch opening not structurally defined"]},{"year":2006,"claim":"Resolved the conserved spindle-orientation effector by showing Pins binds the NuMA-related Mud and that Gαi/Mud engage Pins through distinct domains in graded activity states, linking cortical polarity to spindle alignment.","evidence":"Direct binding, Co-IP, and mud mutant genetics in Drosophila neuroblasts plus domain-state biochemistry","pmids":["16648843","17726110","16377571"],"confidence":"High","gaps":["How distinct GoLoco motifs partition between cortical recruitment and switch opening not yet fully separated","Parallel pathway integration mechanism incomplete"]},{"year":2007,"claim":"Demonstrated the vertebrate developmental role: LGN controls planar spindle orientation in neural progenitors, and its loss randomizes divisions and disrupts neuroepithelial self-renewal without altering fate decisions.","evidence":"Dominant-negative electroporation in chick and conditional knockout in mouse neuroepithelium with lineage analysis","pmids":["17934458","18084280"],"confidence":"High","gaps":["Cortical anchoring machinery in vertebrates not yet defined","Upstream polarity cues unresolved"]},{"year":2010,"claim":"Defined how LGN cortical localization is spatially patterned and dynamically regulated, identifying aPKC/14-3-3 apical exclusion and Ric-8A/Gαi cortical recruitment of the LGN/NuMA/dynein module.","evidence":"Ser401 phosphosite mutagenesis, 14-3-3 binding, 3D cyst culture, pertussis toxin and RNAi with live imaging in MDCK/HeLa","pmids":["20933426","20385777","20479129"],"confidence":"High","gaps":["Force-generation step downstream of dynein not quantified","Integration of multiple cortical anchors not yet unified"]},{"year":2010,"claim":"Connected the spindle-orientation machinery to human disease by identifying GPSM2 truncating mutations causing nonsyndromic deafness DFNB82 with hair-cell apical localization.","evidence":"Exome sequencing, homozygosity mapping, and mouse inner-ear immunolocalization","pmids":["20602914"],"confidence":"Medium","gaps":["Cochlear mechanism inferred from localization rather than direct functional assay","Relationship to spindle-orientation function unclear at this stage"]},{"year":2011,"claim":"Provided atomic-resolution and quantitative basis for partner selection, showing mInsc and NuMA bind the LGN TPR at overlapping interfaces in a mutually exclusive, affinity-ranked manner, switching LGN between asymmetric-fate and spindle-capture complexes.","evidence":"X-ray crystallography, ITC, and competition assays of LGN/Pins TPR with NuMA and Insc","pmids":["21816348","22074847","22171003"],"confidence":"High","gaps":["Temporal control of the mInsc-to-NuMA handoff in cells not resolved","Structure of full-length closed LGN not yet determined"]},{"year":2011,"claim":"Established robustness logic: ultrasensitive Gαi activation of Pins (via GoLoco decoy motifs) sharpens the polarity-to-spindle coupling, explaining why LGN reliably aligns spindles within a narrow signal range.","evidence":"Reconstituted spindle-orientation pathway with Hill-coefficient analysis and neuroblast domain mutants; FRAP/live imaging of cortical LGN/NuMA belts","pmids":["21855794","21444683"],"confidence":"High","gaps":["Whether mammalian LGN shows identical ultrasensitivity not tested","In vivo concentration ranges of Gαi not measured"]},{"year":2013,"claim":"Resolved the autoinhibited architecture and cytoskeletal coupling, showing tandem GoLoco motifs occupy the TPR concave surface and that dynein/astral-microtubule transport, opposed by actin, governs cortical LGN turnover.","evidence":"Crystal structure of truncated LGN; Co-IP with dynein heavy chain, FRAP, and cytoskeletal drug perturbation","pmids":["23665171","23389635","24358023"],"confidence":"High","gaps":["Structure of intact closed-to-open transition not captured","Quantitative force coupling to dynein unresolved"]},{"year":2014,"claim":"Identified the cortical anchoring network—Dlg1, Par3/mInsc/Gαi3, and SLK-activated ERM proteins—that positions and polarizes LGN to set planar versus perpendicular division orientation in vivo.","evidence":"Direct binding, conditional knockouts and in vivo RNAi, micropatterns, and live imaging in chick/mouse/human cells","pmids":["25202028","25016959","24958772"],"confidence":"High","gaps":["Hierarchy among redundant anchors not fully ordered","How anchors are temporally activated at mitotic entry incomplete"]},{"year":2016,"claim":"Defined direct structural anchoring to cortical F-actin and a competitive negative regulator, showing Afadin bridges LGN/NuMA to actin while SAPCD2 competes with NuMA to limit cortical LGN and tune asymmetric division.","evidence":"Crystal structure of Afadin-LGN, direct binding, Co-IP, RNAi, and in vivo retinal division-angle analysis","pmids":["26751642","26766442"],"confidence":"High","gaps":["Coordination between Afadin anchoring and SAPCD2 competition not integrated","In vivo balance of these regulators in different tissues unmapped"]},{"year":2017,"claim":"Established cadherin junctions as instructive orientation cues, showing LGN binds E-cadherin and phospho-VE-cadherin tails and is locally handed off to NuMA at mitosis, extending LGN function to endothelial flow responses.","evidence":"Direct binding, NuMA/cadherin competition assays, phosphosite mutants, and in vivo vascular remodeling","pmids":["28045117","28712573"],"confidence":"High","gaps":["Mechanistic link between flow signaling and division orientation not fully defined","Generality across epithelial cadherins unresolved"]},{"year":2018,"claim":"Showed a motor-independent function: a stable Insc:LGN:Gαi tetramer drives asymmetric cell fate in mammary stem cells and rescues aberrant symmetric divisions, decoupling LGN's fate role from microtubule-motor spindle capture.","evidence":"Crystal structure, SEC-SAXS, complex-stability assays, and mammary stem cell functional assays","pmids":["29523789"],"confidence":"High","gaps":["Downstream fate-determinant readout of the tetramer unidentified","How tetramer resists NuMA in different cell types unknown"]},{"year":2019,"claim":"Defined the cochlear molecular pathway, placing GPSM2-GNAI in series with MYO15A and WHRN to specify tallest-row stereocilia identity by stabilizing the MYO15A-EPS8 tip complex and regulating actin elongation.","evidence":"Comprehensive genetic epistasis, STED nanoscopy, single-molecule tracking, and time-course localization in mouse auditory epithelium","pmids":["30827920","28387217","26662512"],"confidence":"High","gaps":["How the GoLoco/Gαi GDI activity mechanistically drives actin elongation not resolved","Whether spindle-orientation switch logic applies to the stereocilia nanodomain unclear"]},{"year":null,"claim":"How the various competing cortical anchors, regulators, and partner switches are temporally and spatially integrated within a single mitosis—and how the same switch protein deploys distinct mechanisms in spindle orientation versus stereocilia tip actin regulation—remains unresolved.","evidence":"","pmids":[],"confidence":"High","gaps":["No unified model integrating Afadin/Dlg1/E-cadherin/ERM anchoring with dynein turnover","Mechanistic basis of stereocilia-specific GPSM2 function distinct from mitotic role undefined"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[8,30,5,11,15]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[7,2,24,38]},{"term_id":"GO:0008092","term_label":"cytoskeletal protein binding","supporting_discovery_ids":[2,32]},{"term_id":"GO:0005198","term_label":"structural molecule activity","supporting_discovery_ids":[27,38,43]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[6,7,20,21,27]},{"term_id":"GO:0005815","term_label":"microtubule organizing center","supporting_discovery_ids":[17,23]},{"term_id":"GO:0005929","term_label":"cilium","supporting_discovery_ids":[42,44]},{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[3]}],"pathway":[{"term_id":"R-HSA-1640170","term_label":"Cell Cycle","supporting_discovery_ids":[7,17,22,27]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[17,18,35,39,43]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[8,10,14,41]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[19,29]}],"complexes":["Gαi/LGN/NuMA cortical complex","Par3/mInsc/LGN/Gαi complex","WHRN-GPSM2-GNAI stereocilia tip module","Lgl2/aPKC/Par-6/LGN complex"],"partners":["GNAI1","NUMA1","INSC","RIC8A","DLG1","AFDN","CDH1","MYO15A"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P81274","full_name":"G-protein-signaling modulator 2","aliases":["Mosaic protein LGN"],"length_aa":684,"mass_kda":76.7,"function":"Plays an important role in mitotic spindle pole organization via its interaction with NUMA1 (PubMed:11781568, PubMed:15632202, PubMed:21816348). Required for cortical dynein-dynactin complex recruitment during metaphase (PubMed:22327364). Plays a role in metaphase spindle orientation (PubMed:22327364). Also plays an important role in asymmetric cell divisions (PubMed:21816348). Has guanine nucleotide dissociation inhibitor (GDI) activity towards G(i) alpha proteins, such as GNAI1 and GNAI3, and thereby regulates their activity (By similarity)","subcellular_location":"Cytoplasm; Cytoplasm, cell cortex; Cytoplasm, cytoskeleton, spindle pole; Lateral cell membrane","url":"https://www.uniprot.org/uniprotkb/P81274/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/GPSM2","classification":"Not Classified","n_dependent_lines":4,"n_total_lines":1208,"dependency_fraction":0.0033112582781456954},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/GPSM2","total_profiled":1310},"omim":[{"mim_id":"616919","title":"FERM AND PDZ DOMAINS-CONTAINING PROTEIN 1; FRMPD1","url":"https://www.omim.org/entry/616919"},{"mim_id":"610668","title":"INSC SPINDLE ORIENTATION ADAPTOR PROTEIN; INSC","url":"https://www.omim.org/entry/610668"},{"mim_id":"609245","title":"G PROTEIN SIGNALING MODULATOR 2; GPSM2","url":"https://www.omim.org/entry/609245"},{"mim_id":"604213","title":"CHUDLEY-MCCULLOUGH SYNDROME; CMCS","url":"https://www.omim.org/entry/604213"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Cytosol","reliability":"Supported"},{"location":"Centrosome","reliability":"Additional"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"tongue","ntpm":50.8}],"url":"https://www.proteinatlas.org/search/GPSM2"},"hgnc":{"alias_symbol":["LGN","Pins"],"prev_symbol":["DFNB82"]},"alphafold":{"accession":"P81274","domains":[],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P81274","model_url":"https://alphafold.ebi.ac.uk/files/AF-P81274-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P81274-F1-predicted_aligned_error_v6.png","plddt_mean":66.94},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=GPSM2","jax_strain_url":"https://www.jax.org/strain/search?query=GPSM2"},"sequence":{"accession":"P81274","fasta_url":"https://rest.uniprot.org/uniprotkb/P81274.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P81274/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P81274"}},"corpus_meta":[{"pmid":"15716953","id":"PMC_15716953","title":"Melanopsin-expressing ganglion cells in primate retina signal colour and irradiance and project to the LGN.","date":"2005","source":"Nature","url":"https://pubmed.ncbi.nlm.nih.gov/15716953","citation_count":936,"is_preprint":false},{"pmid":"18084280","id":"PMC_18084280","title":"Neuroepithelial progenitors undergo LGN-dependent planar divisions to maintain self-renewability during mammalian neurogenesis.","date":"2007","source":"Nature cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/18084280","citation_count":401,"is_preprint":false},{"pmid":"15537540","id":"PMC_15537540","title":"Mammalian Pins is a conformational switch that links NuMA to heterotrimeric G proteins.","date":"2004","source":"Cell","url":"https://pubmed.ncbi.nlm.nih.gov/15537540","citation_count":321,"is_preprint":false},{"pmid":"10753746","id":"PMC_10753746","title":"A protein complex containing Inscuteable and the Galpha-binding protein Pins orients asymmetric cell divisions in Drosophila.","date":"2000","source":"Current biology : 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LGN contains 10 Leu-Gly-Asn repeats, seven N-terminal repeats (~40 aa each) and four C-terminal repeats (~34 aa each).\",\n      \"method\": \"Yeast two-hybrid screen; in vitro binding assay with recombinant proteins\",\n      \"journal\": \"Gene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — yeast two-hybrid plus in vitro binding assay in a single study, two orthogonal methods\",\n      \"pmids\": [\"8973305\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"Drosophila Pins (ortholog of LGN/GPSM2) was identified as a binding partner of Inscuteable and a Gα subunit in vivo, localizing to the apical cortex of neuroblasts. In pins mutants, spindle orientation and basal localization of Numb/Miranda were defective, and Inscuteable lost its apical localization during mitosis, establishing Pins as essential for asymmetric cell division.\",\n      \"method\": \"In vivo co-immunoprecipitation; genetic loss-of-function (pins mutants); immunofluorescence localization\",\n      \"journal\": \"Current biology : CB\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP in vivo, genetic mutant phenotypes, replicated across multiple experimental approaches in a foundational study\",\n      \"pmids\": [\"10753746\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"LGN binds with high affinity to the C-terminal tail of NuMA. A small domain within the C terminus of NuMA stabilizes microtubules in vitro, and LGN blocks this stabilization by steric exclusion, as the MT-binding domain on NuMA overlaps by ten amino acid residues with the LGN-binding domain.\",\n      \"method\": \"In vitro microtubule stabilization assay; frog egg extracts; in vitro binding assays; domain mapping\",\n      \"journal\": \"Current biology : CB\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro reconstitution assays with defined domain overlap and functional consequence, multiple orthogonal methods in single study\",\n      \"pmids\": [\"12445386\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"LGN localizes to the midbody structure separating daughter cells during the later stages of mitosis in PC12 and COS7 cells, moving from the nucleus to the midbody during cytokinesis. Its subcellular localization is differentially regulated by the cell cycle compared to the closely related AGS3.\",\n      \"method\": \"Immunocytochemistry; cell fractionation; expression of LGN-specific antisera\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — immunocytochemical localization in multiple cell types, single lab but consistent across conditions\",\n      \"pmids\": [\"11832491\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"Mouse PINS (LGN/GPSM2 ortholog) can asymmetrically localize to the apical cortex of Drosophila neuroblasts when ectopically expressed, and can functionally substitute for Drosophila Pins in all aspects of neuroblast asymmetric cell division. The N-terminal TPR domain directly interacts with the asymmetric localization domain of Inscuteable, and the C-terminal GoLoco region directs cortical localization.\",\n      \"method\": \"Ectopic expression in Drosophila neuroblasts; direct binding assay; genetic rescue experiments\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — direct binding assay, genetic rescue of null mutant, and localization experiments; demonstrates conservation of function\",\n      \"pmids\": [\"12571286\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"In C. elegans, GPR-1 and GPR-2 (homologs of mammalian AGS3/LGN and Drosophila Pins) control spindle position by acting as GDP dissociation inhibitors (GDI) for GOA-1 (Gαo). LIN-5 (NuMA homolog) binds GPR proteins and is required for their cortical association. GPR proteins are enriched at the posterior cortex in a PAR-dependent manner, generating asymmetric pulling forces on spindle poles.\",\n      \"method\": \"RNAi depletion; GDI fluorescence assay; Co-IP; genetic epistasis\",\n      \"journal\": \"Current biology : CB\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — biochemical GDI assay, Co-IP, and genetic epistasis in a key model organism study\",\n      \"pmids\": [\"12814548\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"LGN exhibits enriched cortical localization during mitosis in certain mammalian cell lines (WISH, PC12, NRK but not COS cells). The Gα-binding C-terminal portion of LGN is sufficient for cortical localization. Cortical localization depends on microfilaments, and overexpression of Gα subunits can redirect LGN to the cortex in COS cells. Interfering with LGN function disrupts cell cycle progression.\",\n      \"method\": \"Overexpression of LGN domain truncations; immunofluorescence; cytochalasin D treatment; dominant-negative experiments\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — multiple cell lines and domain mapping, single lab, consistent results across conditions\",\n      \"pmids\": [\"12925752\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Mammalian LGN (GPSM2) acts as a conformational switch: in its closed (autoinhibited) state, the N-terminal (TPR) and C-terminal (GoLoco) domains interact intramolecularly. NuMA or Gαi can disrupt this autoinhibitory interaction, allowing LGN to simultaneously bind both proteins and recruit them to the cell cortex. During mitosis, LGN recruits NuMA to the cell cortex; cortical association of LGN requires Gα binding. Overexpression of Gαi or YFP-LGN causes metaphase spindle oscillation.\",\n      \"method\": \"FRET biosensor; Co-immunoprecipitation; live cell imaging; overexpression\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — FRET biosensor directly measures conformational change, reciprocal Co-IP, live imaging; multiple orthogonal methods in one study\",\n      \"pmids\": [\"15537540\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"GPSM2 GoLoco motifs 1-4 all function as guanine nucleotide dissociation inhibitors (GDIs) for Gαi1, Gαi2, and Gαi3, but display significantly lower GDI activity and binding affinity for Gαo. Surface plasmon resonance binding assays showed all four GoLoco motifs bind Gαi1 but not Gαs, establishing Gαi subunits as the primary in vivo targets.\",\n      \"method\": \"Surface plasmon resonance; fluorescence-based nucleotide binding (GDI) assay; recombinant GST-fusion proteins\",\n      \"journal\": \"Biochimica et biophysica acta\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — quantitative in vitro biochemical assays with purified proteins, two orthogonal methods (SPR + fluorescence GDI assay)\",\n      \"pmids\": [\"15946753\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"In Drosophila neuroblasts, astral microtubules, kinesin Khc-73, and Discs large (Dlg) induce cortical polarization of Pins/Gαi; Dlg/Khc-73 and Dlg/Pins co-immunoprecipitate, suggesting Dlg mediates the link between microtubules and Pins/Gαi cortical polarity. This microtubule/Khc-73/Dlg pathway acts in parallel to the Inscuteable/Par pathway.\",\n      \"method\": \"Co-immunoprecipitation; live imaging; genetic loss-of-function; immunofluorescence\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — Co-IP, genetic epistasis with multiple mutants, and live imaging; multiple orthogonal approaches\",\n      \"pmids\": [\"16377571\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Mammalian Ric-8A catalytically dissociates Gαi-GDP/LGN/NuMA complexes in vitro, releasing activated Gαi-GTP and concomitantly liberating NuMA from LGN. This establishes a mechanism whereby Ric-8A GEF activity for Gαi regulates the LGN-NuMA interaction during cell division.\",\n      \"method\": \"In vitro biochemical dissociation assay with purified proteins; fluorescence-based GTPase assay\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro reconstitution with purified proteins demonstrating catalytic mechanism\",\n      \"pmids\": [\"16275912\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"LGN is expressed in photoreceptor inner segments and co-localizes with transducin α (Gαt) following its light-dependent translocation. LGN and Gαt co-precipitate from retinal extracts, and the GPR domain of LGN potently inhibits receptor-mediated guanine nucleotide exchange and GTPase activity of transducin, identifying a role for LGN in modulating transducin function in photoreceptors.\",\n      \"method\": \"Immunostaining; serial tangential sectioning with immunoblot; co-precipitation; in vitro GDI/GTPase inhibition assay\",\n      \"journal\": \"Molecular and cellular neurosciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-precipitation plus functional in vitro assay, single lab\",\n      \"pmids\": [\"15737739\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"LGN directly binds Lgl2 (mammalian homolog of Drosophila l(2)gl) with Kd ~56 nM via the C-terminal tail of Lgl2. Endogenous Lgl2 forms a complex with aPKC, Par-6, and LGN, enhanced during metaphase. Overexpression of Lgl2 C-terminal tail mislocalized NuMA and disorganized the mitotic spindle; knockdown of Lgl1/2 caused spindle disorganization and micronuclei formation, mediated through regulation of the LGN-NuMA complex.\",\n      \"method\": \"Co-immunoprecipitation; in vitro binding with Kd measurement; siRNA knockdown; immunofluorescence\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — quantitative binding assay, reciprocal Co-IP, RNAi knockdown with defined phenotype, multiple orthogonal methods\",\n      \"pmids\": [\"15632202\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Drosophila Pins (LGN ortholog) directly binds and co-immunoprecipitates with the NuMA-related Mushroom body defect (Mud) protein. Pins recruits Mud to the neuroblast apical cortex; in mud mutants, spindle alignment with cortical polarity is lost. This establishes a direct Pins-Mud interaction linking cortical polarity to spindle orientation.\",\n      \"method\": \"Direct binding assay; co-immunoprecipitation; genetic loss-of-function (mud mutants); immunofluorescence\",\n      \"journal\": \"Nature cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — direct binding assay, reciprocal Co-IP, and genetic loss-of-function with defined phenotype; replicated in companion paper (PMID:16648846)\",\n      \"pmids\": [\"16648843\", \"16648846\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"LGN modulates GIRK channel activity in a Gαi/Go-dependent manner: LGN increases basal GIRK current but reduces receptor-activated GIRK currents. This effect is mediated through the N-terminal TPR domain of LGN, which likely releases sequestered endogenous LGN. In hippocampal neurons, LGN hyperpolarizes resting potential through increased basal GIRK activity; LGN RNAi reduces basal GIRK activity.\",\n      \"method\": \"Electrophysiology (patch-clamp); LGN domain overexpression; lentiviral RNAi in hippocampal neurons\",\n      \"journal\": \"Neuron\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — electrophysiological functional assay combined with domain overexpression and RNAi knockdown; multiple orthogonal approaches\",\n      \"pmids\": [\"16701207\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"In Drosophila neuroblasts, Loco (a GoLoco protein) and Pins act synergistically as GDIs for Gαi to release free Gβγ, which is required for asymmetric spindle and daughter cell size. Simultaneous removal of Loco and Pins phenocopies Gβ13F or Gγ1 mutants. Loco's RGS domain also accelerates GTPase activity of Gαi, providing a second mode of regulation.\",\n      \"method\": \"Genetic epistasis (double mutants); in vitro GDI assay; RGS GTPase acceleration assay\",\n      \"journal\": \"Genes & development\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — biochemical GDI and GTPase assays combined with genetic epistasis in multiple mutant backgrounds\",\n      \"pmids\": [\"15937221\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Drosophila Pins (LGN ortholog) forms a 'closed' autoinhibited state via intramolecular GoLoco-TPR interactions. Gαi binding to GoLoco 1 (GL1) recruits Pins to the apical cortex without opening Pins or recruiting Mud. Gαi and Mud bind cooperatively to GL2/3 and TPR domains respectively, activating the full spindle orientation pathway. These multiple activity states link cortical polarity to spindle orientation.\",\n      \"method\": \"Biochemical binding assays; genetic epistasis; live imaging; domain mutant analysis\",\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 — multiple orthogonal methods including biochemistry, genetics, and live imaging; defines molecular mechanism with domain precision\",\n      \"pmids\": [\"17726110\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"LGN (GPSM2) is required for planar divisions in chick neuroepithelium; it localizes at the cell cortex and spindle poles of neural progenitors. Interfering with LGN function randomizes the division plane, causing one daughter to exit the neuroepithelium prematurely and proliferate aberrantly, without affecting cell fate. This demonstrates LGN controls spindle movements/orientation in vertebrate neural progenitors.\",\n      \"method\": \"In ovo electroporation (dominant-negative LGN); immunofluorescence; BrdU lineage analysis\",\n      \"journal\": \"Nature neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — loss-of-function with specific cellular phenotype, localization, replicated by companion paper (PMID:18084280)\",\n      \"pmids\": [\"17934458\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Knockout of LGN (GPSM2) in mouse neuroepithelial cells randomizes the orientation of normally planar cell divisions, causing loss of the apical membrane from some daughter cells and converting them into abnormally localized progenitors, without affecting neuronal production rate. LGN is dispensable for the proliferation vs. differentiation decision but essential for maintaining neuroepithelial self-renewal via planar spindle orientation.\",\n      \"method\": \"LGN conditional knockout (gene targeting); BrdU/EdU labeling; immunofluorescence; clonal analysis\",\n      \"journal\": \"Nature cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — knockout mouse model with defined cellular phenotype, mechanistic link to apical membrane inheritance\",\n      \"pmids\": [\"18084280\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"A nonsense mutation in GPSM2 (early truncation) causes nonsyndromic hearing loss DFNB82 in humans. In mouse inner ear, GPSM2 is localized to apical surfaces of hair cells and supporting cells, most highly expressed during embryonic development, establishing GPSM2 as essential for normal hearing development.\",\n      \"method\": \"Whole exome sequencing; homozygosity mapping; immunolocalization in mouse inner ear\",\n      \"journal\": \"American journal of human genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — human genetics identifying causative mutation plus immunolocalization; functional mechanism inferred from localization and known protein function\",\n      \"pmids\": [\"20602914\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"During epithelial mitosis, Par3/aPKC excludes LGN (Pins) from the apical cortex by aPKC-mediated phosphorylation of Pins on Ser401, which recruits 14-3-3 protein. 14-3-3 binding inhibits Pins association with Gαi, causing Pins to dissociate from the apical cortex. A Pins S401A mutant mislocalizes over the entire cortex and causes spindle misorientation and multi-lumen cysts.\",\n      \"method\": \"siRNA knockdown; phosphorylation site mutagenesis (S401A); 14-3-3 binding assay; 3D cyst culture; immunofluorescence\",\n      \"journal\": \"Current biology : CB\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — phosphosite mutagenesis, binding assay, and functional rescue/phenotypic assay in 3D culture; multiple orthogonal methods\",\n      \"pmids\": [\"20933426\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"LGN localizes to the lateral cell cortex (excluded from apical cortex) of dividing MDCK cells. Depleting LGN, preventing cortical localization, or disrupting its interaction with NuMA or Gα proteins causes spindle misorientation and abnormal cystogenesis (multiple lumens). Apical exclusion of LGN is mediated by aPKC. Artificial mistargeting of LGN to the apical membrane rotates the spindle ~90° and disrupts cystogenesis.\",\n      \"method\": \"siRNA knockdown; dominant-negative constructs; apical membrane targeting of LGN; 3D cyst culture; immunofluorescence\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple loss-of-function approaches, gain-of-function mistargeting, defined morphogenetic phenotype; multiple orthogonal methods\",\n      \"pmids\": [\"20385777\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Ric-8A and Gαi cooperate to recruit LGN (GPSM2), NuMA, and dynein to the cell cortex of mammalian cells during mitosis. Pertussis toxin (blocking Ric-8A-Gαi interaction), Ric-8A knockdown, or Gαi knockdown each impaired cortical localization of LGN, NuMA, and dynein, and disturbed integrin-dependent mitotic spindle orientation. Reduced Ric-8A prolonged mitosis and decreased spindle movements.\",\n      \"method\": \"siRNA knockdown; pertussis toxin treatment; immunofluorescence; live imaging (GFP-tubulin HeLa cells)\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple independent perturbations (toxin, RNAi) converging on same phenotype, live imaging, multiple orthogonal methods\",\n      \"pmids\": [\"20479129\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"GPSM2 (LGN) is phosphorylated on Thr450 by the serine/threonine kinase PBK/TOPK during mitosis. LGN/GPSM2 localizes to the spindle at metaphase and to the midzone/midbody in cytokinesis. Overexpression of the T450A phospho-dead mutant induces aberrant chromosomal segregation and growth suppression of breast cancer cells; siRNA knockdown of GPSM2 causes incomplete cell division.\",\n      \"method\": \"Western blot (phospho-specific); siRNA knockdown; T450A mutant overexpression; immunocytochemistry; synchronization assays\",\n      \"journal\": \"Genes, chromosomes & cancer\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — kinase-substrate identification with phosphomimetic mutant phenotype, single lab\",\n      \"pmids\": [\"20589935\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Crystal structures of LGN in complex with NuMA and mInsc (mammalian Inscuteable) reveal that NuMA and mInsc interact with LGN TPR domain through distinct but overlapping interfaces. Structural and biochemical studies demonstrate that NuMA and mInsc binding to LGN are mutually exclusive, with mInsc binding preferentially (higher affinity). This suggests Par3/mInsc/LGN and NuMA/LGN/Gαi complexes play sequential and partially overlapping roles.\",\n      \"method\": \"X-ray crystallography; isothermal titration calorimetry; competitive binding assays; cell biology (localization studies)\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — high-resolution crystal structures with functional validation by ITC and competition assays; multiple orthogonal methods\",\n      \"pmids\": [\"21816348\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Crystal structure of Drosophila Pins (LGN ortholog) TPR domain in complex with Inscuteable reveals modular binding interface with three contact modules on Insc running antiparallel to the TPR superhelix. Structure-based mutagenesis defines critical residues. mInsc binds LGN with highest affinity (Kd ~2.4 nM), effectively displacing NuMA and other interactors; mInsc-LGN interaction is required for stabilization of LGN and intracellular localization of mInsc.\",\n      \"method\": \"X-ray crystallography (2.6 Å); structure-based mutagenesis; isothermal titration calorimetry; cell biology\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — atomic-resolution crystal structure with mutagenesis validation and quantitative binding measurements\",\n      \"pmids\": [\"22074847\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Crystal structure of Drosophila Pins (LGN ortholog) in complex with Inscuteable, combined with in vitro competition assays, demonstrates that Insc competes with NuMA for LGN TPR binding and has higher affinity. Insc can open the LGN conformational switch. The positively charged EPE-motif contact patch on LGN is shared by both Insc and NuMA.\",\n      \"method\": \"X-ray crystallography; in vitro competition assays; isothermal titration calorimetry\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure plus quantitative in vitro competition assays; replicates findings from companion papers with orthogonal approach\",\n      \"pmids\": [\"22171003\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"LGN and NuMA form a lateral belt at the cortex of chick neuroepithelial cells during metaphase. FRAP and live imaging show LGN/NuMA cortical localization is dynamic. The LGN/NuMA/Gαi complex is required for active spindle movements and planar maintenance of the spindle. Lateral restriction of LGN/NuMA is instructive for planar spindle alignment.\",\n      \"method\": \"3D live imaging; FRAP; immunofluorescence; dominant-negative LGN; siRNA\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — live imaging with FRAP demonstrating dynamics, multiple loss-of-function approaches, defined spindle orientation phenotype\",\n      \"pmids\": [\"21444683\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"In Drosophila, Wee B/Canoe directly binds the Pins TPR domain; this interaction recruits Canoe to the cortex and is required for activation of the Pins(TPR)-Mud spindle orientation pathway. Canoe RA domains bind RanGTP, and both Canoe(RA) domains and RanGTP are required to recruit Mud to the cortex and activate spindle orientation.\",\n      \"method\": \"Direct binding assay; induced cell polarity system; genetic epistasis; immunofluorescence\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct binding assay and genetic epistasis with defined pathway, single lab\",\n      \"pmids\": [\"22024168\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Mutations in GPSM2 (two single-base deletions, one nonsense mutation, one splice-site mutation) cause Chudley-McCullough syndrome (CMS), characterized by sensorineural hearing loss and brain malformations including frontal polymicrogyria, corpus callosum agenesis, and gray matter heterotopia. This links GPSM2 function in mitotic spindle orientation to the etiology of brain malformations and hearing loss.\",\n      \"method\": \"Homozygosity mapping; whole-exome sequencing; brain imaging of affected individuals\",\n      \"journal\": \"American journal of human genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — human genetics identifying multiple independent causative mutations; functional mechanism inferred from known GPSM2 biology\",\n      \"pmids\": [\"22578326\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Crystal structures of LGN GoLoco 3 (GL3) and GL4 in complex with Gαi·GDP reveal the structural basis of GoLoco/Gαi interaction. A highly conserved 'double Arg finger' sequence (RΨ(D/E)(D/E)QR) is responsible for GDP binding. Only a few residues C-terminal to the conserved GL sequence are required for Gαi·GDP interaction. LGN C-terminal GL domain binds four Gαi·GDP molecules; all four GL motifs are potent GDIs.\",\n      \"method\": \"X-ray crystallography; isothermal titration calorimetry; fluorescence-based GDI assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — atomic-resolution crystal structures with functional validation; defines GDI mechanism at molecular level\",\n      \"pmids\": [\"22952234\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"The crystal structure of a truncated LGN reveals its autoinhibited conformation: two consecutive GoLoco (GL) motifs (GL12 or GL34) form minimal TPR-binding units, with GL34 forming parallel α-helices that bind the concave surface of TPR4-7, preventing LGN from binding other targets. GL motifs bind TPRs by a mode distinct from GL/Gαi·GDP interactions.\",\n      \"method\": \"X-ray crystallography; binding assays; domain truncation analysis\",\n      \"journal\": \"Structure (London, England : 1993)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure revealing distinct binding mode with functional implications; multiple domain constructs tested\",\n      \"pmids\": [\"23665171\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"LGN associates with cytoplasmic dynein heavy chain (DYNC1H1) in a Gαi-regulated manner. LGN is required for mitotic cortical localization of dynein, which in turn also modulates cortical LGN accumulation. FRAP analysis shows cortical LGN is dynamic and turns over via astral microtubule- and dynein-dependent transport. Actin filaments counteract dynein-mediated cortical release of Gαi/LGN/NuMA, maintaining cortical retention.\",\n      \"method\": \"Co-immunoprecipitation; FRAP; siRNA knockdown; cytoskeletal drug treatments; immunofluorescence\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP, FRAP dynamics, and multiple perturbation experiments; several orthogonal methods in one study\",\n      \"pmids\": [\"23389635\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Par1b promotes the apicolateral accumulation of LGN and capture of NuMA-positive astral microtubules in mitotic hepatocytes to orient the mitotic spindle, resulting in asymmetric inheritance of apical plasma membrane domains between daughter cells.\",\n      \"method\": \"siRNA knockdown; immunofluorescence; live imaging; 3D culture\",\n      \"journal\": \"PLoS biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional knockdown with spindle orientation and polarity phenotype, single lab\",\n      \"pmids\": [\"24358023\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Direct interaction between Dlg1 and LGN promotes cortical localization of the LGN complex and is required for planar spindle orientation in the chick neuroepithelium and human cells on adhesive micropatterns. Live imaging shows Dlg1 is required for directed spindle movements during metaphase.\",\n      \"method\": \"Direct binding assay; siRNA knockdown; live imaging; immunofluorescence; dominant-negative experiments\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — direct binding assay, RNAi, live imaging, and defined spindle orientation phenotype; multiple orthogonal methods\",\n      \"pmids\": [\"25202028\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Par3, mInsc, and Gαi3 cooperate to polarize LGN and promote perpendicular (asymmetric) divisions in murine epidermis. Loss of both Gnai3 and mInsc phenocopies loss of LGN (mostly planar divisions), demonstrating that Par3-mInsc and Gαi3 act cooperatively upstream of LGN to control its apical localization and division orientation.\",\n      \"method\": \"Conditional knockouts; in vivo lentiviral RNAi; immunofluorescence; division angle quantification\",\n      \"journal\": \"Nature cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple in vivo genetic perturbations with epistasis, defined phenotypic readout\",\n      \"pmids\": [\"25016959\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"SLK kinase directly activates ERM proteins (ezrin/radixin/moesin) at mitotic entry in mammalian cells. Activated ERMs promote polarized cortical association of LGN and NuMA, which is required for spindle orientation. Impairing ERM activation in apical progenitors of the mouse embryonic neocortex severely disturbs spindle orientation in vivo.\",\n      \"method\": \"siRNA knockdown; phospho-specific antibodies; micropatterned adhesive substrates; in vivo mouse neocortex experiments; immunofluorescence\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vitro and in vivo loss-of-function with defined LGN/NuMA localization phenotype; multiple orthogonal approaches\",\n      \"pmids\": [\"24958772\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"The GoLoco motifs of GPSM2/LGN are essential for hearing. Mice with truncation of the C-terminal GoLoco motifs (LgnΔC) are profoundly deaf, show hair bundle misorientation and severe stereocilia malformations. Gαi and aPKC depend on LGN for proper localization in hair cells. LGN functions as a PCP effector downstream of core PCP proteins; kinocilium positioning is required for LGN/Gαi/aPKC apical localization.\",\n      \"method\": \"Mouse knockout (targeted GoLoco truncation); auditory brainstem response; scanning EM; immunofluorescence; in vitro translation\",\n      \"journal\": \"Mammalian genome\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — defined mouse knockout, functional hearing assay, mechanistic epistasis with Gαi and aPKC localization\",\n      \"pmids\": [\"26662512\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Afadin directly and concomitantly binds both F-actin and LGN. Crystal structure of human Afadin in complex with LGN reveals structural similarity to the LGN-NuMA complex. In mitosis, Afadin is necessary for cortical accumulation of LGN and NuMA above spindle poles in an F-actin-dependent manner. Afadin acts as a molecular hub anchoring the dynein/LGN/NuMA machinery to cortical F-actin.\",\n      \"method\": \"X-ray crystallography; direct binding assays; siRNA knockdown; 3D cyst culture; immunofluorescence\",\n      \"journal\": \"Nature structural & molecular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure of complex with functional validation by multiple binding and cell biology assays\",\n      \"pmids\": [\"26751642\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"SAPCD2 is a novel LGN-interacting protein that negatively regulates LGN cortical localization, likely by competing with NuMA for LGN binding. Loss of SAPCD2 randomizes spindle orientation in epithelial cells and retinal progenitors in vivo, and triples the number of asymmetric terminal divisions in the developing retina.\",\n      \"method\": \"Co-immunoprecipitation; siRNA knockdown; in vivo mouse retinal experiments; division angle quantification; immunofluorescence\",\n      \"journal\": \"Developmental cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — Co-IP, competition binding, in vitro and in vivo loss-of-function with quantitative phenotypic analysis\",\n      \"pmids\": [\"26766442\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"E-cadherin functions as an instructive cue for division orientation by directly binding LGN at cell-cell adhesions. LGN adopts a 3D structure similar to cadherin-bound catenins and binds the E-cadherin cytosolic tail. On mitotic entry, NuMA competes LGN from E-cadherin to locally form the LGN/NuMA complex, stabilizing cortical astral microtubule associations at adhesions to orient the spindle.\",\n      \"method\": \"Direct binding assay; immunofluorescence; siRNA knockdown; competition assay (NuMA vs E-cadherin for LGN)\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — direct binding, competition assay, and functional RNAi knockdown with defined division orientation phenotype\",\n      \"pmids\": [\"28045117\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Phosphorylation of VE-cadherin Y658 by Src-family kinases induces dissociation of p120ctn, enabling LGN to bind the VE-cadherin cytoplasmic tail at endothelial cell junctions. LGN binding to phospho-Y658 VE-cadherin is required for multiple endothelial flow responses including inflammatory signaling at disturbed flow and flow-dependent vascular remodeling.\",\n      \"method\": \"Phosphomimetic and phospho-dead VE-cadherin mutants; Co-IP; siRNA knockdown; in vivo vascular remodeling assays\",\n      \"journal\": \"Current biology : CB\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — phosphosite-specific mutants, Co-IP, and in vitro/in vivo functional assays; multiple orthogonal methods\",\n      \"pmids\": [\"28712573\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"GPSM2 (Gpsm2) and its partner Gαi3 define an ~200 nm nanodomain at stereocilia tips in auditory and vestibular hair cells. Gpsm2 localization at stereocilia tips requires Gαi3, myosin 15 (Myo15a), and whirlin (Whrn). Loss of Gpsm2 disrupts stereocilia elongation and actin dynamics in growth cones (shown by single-molecule tracking). Absence of Gpsm2 or Gαi3 causes deafness and balance defects.\",\n      \"method\": \"Mouse knockout; single-molecule tracking (live imaging); STED nanoscopy; auditory/vestibular functional assays; genetic epistasis\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — knockout mouse, single-molecule tracking, nanoscopy, genetic epistasis; multiple rigorous orthogonal methods\",\n      \"pmids\": [\"28387217\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Crystal structure of Drosophila LGN (Pins) in complex with the asymmetric domain of Inscuteable reveals a tetrameric arrangement of intertwined molecules. Insc:LGN tetramers form stable cores of Par3-Insc-LGN-GαiGDP complexes that cannot be dissociated by NuMA. In mammary stem cells, Insc bound to LGN:GαiGDP drives asymmetric fate and reverts aberrant symmetric divisions induced by p53 loss, independent of microtubule motor recruitment.\",\n      \"method\": \"X-ray crystallography; SEC-SAXS; in vitro complex stability assay; mammary stem cell functional assays; RNAi\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure plus SAXS validation in solution, and functional in vivo/in vitro stem cell assays\",\n      \"pmids\": [\"29523789\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"GPSM2-GNAI forms a module that confers first-row (tallest stereocilia) identity in the hair bundle. WHRN-GPSM2-GNAI is an extra module recruited to a pre-existing MYO15A-EPS8 complex only in the first (tallest) row. GPSM2 and GNAI are required to stabilize larger amounts of MYO15A-EPS8 in tall-row stereocilia. In GPSM2 or GNAI mutants, bundles retain an embryonic-like generic stereocilia organization. Genetic epistasis demonstrates GPSM2, GNAI, MYO15A, and WHRN operate in series in the same pathway.\",\n      \"method\": \"Comprehensive genetic epistasis in mouse auditory epithelium; immunofluorescence; time-course protein distribution analysis in multiple mutant backgrounds\",\n      \"journal\": \"Current biology : CB\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — comprehensive genetic epistasis across multiple mutants with systematic protein localization analysis; defines pathway order\",\n      \"pmids\": [\"30827920\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"In Drosophila, robust spindle alignment by Pins (LGN) is achieved through ultrasensitive activation by Gαi (apparent Hill coefficient 3.1). GoLoco domains GL1 and GL2 act as 'decoys' competing against activation at GL3, generating ultrasensitivity and ensuring Pins-Mud (NuMA) recruitment occurs over a narrow Gαi concentration range. A non-ultrasensitive Pins mutant fails to robustly couple spindle position to cell polarity in neuroblasts.\",\n      \"method\": \"Reconstituted spindle orientation pathway assay; Hill coefficient analysis; domain mutant neuroblast experiments\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro reconstituted pathway with quantitative dose-response analysis plus in vivo mutant validation\",\n      \"pmids\": [\"21855794\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"GPSM2 (LGN) is a conformational switch protein that, in its autoinhibited state, has intramolecular GoLoco-TPR interactions; binding of Gαi-GDP to its C-terminal GoLoco motifs (where it acts as a GDI) releases autoinhibition and allows the N-terminal TPR domain to simultaneously recruit NuMA and/or mInscuteable, thereby assembling a cortical Gαi/LGN/NuMA complex that captures astral microtubules and orients the mitotic spindle; LGN cortical localization is restricted to lateral/basal domains by aPKC-mediated phosphorylation (Ser401) recruiting 14-3-3 to displace Gαi binding, and is further regulated by Ric-8A (which catalytically releases Gαi-GTP from the complex), dynein-dependent cortical transport, E-cadherin/Afadin/Dlg1-mediated anchoring, and ERM-dependent actin linkage; in the inner ear, GPSM2-GNAI localizes to stereocilia tips in a nanodomain requiring Myo15a and whirlin, where it specifies tallest-row (first-row) stereocilia identity and regulates actin dynamics for elongation.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"GPSM2 (LGN/Pins) is a conformational-switch scaffold that couples cell cortical polarity to mitotic spindle orientation during asymmetric and oriented cell division [#1, #7, #17]. Its C-terminal GoLoco motifs act as guanine-nucleotide dissociation inhibitors (GDIs) selective for Gαi-GDP over Gαo/Gαs, binding up to four Gαi·GDP molecules through a conserved double-Arg-finger motif [#8, #30], while its N-terminal TPR domain recruits the NuMA C-terminus and mInscuteable through distinct but overlapping interfaces [#2, #24]. In the autoinhibited closed state, the GoLoco motifs fold back onto the TPR concave surface to occlude target binding; Gαi engagement of the GoLoco motifs relieves this intramolecular interaction, permitting simultaneous assembly of a cortical Gαi/LGN/NuMA complex that captures astral microtubules and generates spindle-pulling forces [#7, #16, #31]. NuMA and mInsc bind LGN mutually exclusively, with mInsc binding at highest affinity to displace NuMA and route LGN into Par3/mInsc-based asymmetric-fate complexes, establishing a switch between symmetric/oriented and asymmetric division programs [#24, #25, #43]. Cortical positioning of LGN is spatially restricted by aPKC-mediated Ser401 phosphorylation that recruits 14-3-3 to block Gαi binding [#20], and the complex is dynamically tuned by Ric-8A, which catalytically dissociates Gαi-GDP/LGN/NuMA and releases NuMA [#10, #22], by dynein- and astral-microtubule-dependent cortical turnover counterbalanced by actin [#32], and by cortical anchors including Dlg1, Afadin/F-actin, E-cadherin and SLK-activated ERM proteins [#34, #38, #40, #36]. Through this machinery LGN governs planar versus perpendicular divisions in neuroepithelium and epidermis, controlling progenitor self-renewal and apical-membrane inheritance [#17, #18, #35]. In the inner ear, a WHRN–GPSM2–GNAI module localizes to a stereocilia-tip nanodomain dependent on MYO15A and whirlin and confers tallest (first-row) stereocilia identity by stabilizing the MYO15A-EPS8 complex and regulating actin elongation [#42, #44]. Truncating GPSM2 mutations cause nonsyndromic deafness DFNB82 and Chudley-McCullough syndrome, directly linking its spindle-orientation and stereocilia functions to human hearing loss and brain malformation [#19, #29].\",\n  \"teleology\": [\n    {\n      \"year\": 1996,\n      \"claim\": \"Established the founding molecular link by identifying LGN as a Gαi-interacting protein, defining its repeat architecture and pointing to heterotrimeric G-protein regulation as its biochemical context.\",\n      \"evidence\": \"Yeast two-hybrid screen and in vitro binding with recombinant Gαi2\",\n      \"pmids\": [\"8973305\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No functional consequence of the interaction defined\", \"No distinction between TPR and GoLoco repeat functions\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"Placed the protein in a biological process by showing the Drosophila ortholog Pins is essential for asymmetric cell division, bridging Inscuteable/Gα to spindle orientation in vivo.\",\n      \"evidence\": \"In vivo Co-IP, pins loss-of-function mutants, and localization in neuroblasts\",\n      \"pmids\": [\"10753746\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism of how Pins links polarity to spindle not defined\", \"Mammalian conservation not yet tested\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Identified NuMA as a high-affinity TPR partner and showed LGN modulates NuMA-dependent microtubule stabilization, providing a direct molecular route from LGN to the spindle.\",\n      \"evidence\": \"In vitro microtubule stabilization assay, frog egg extracts, and domain mapping\",\n      \"pmids\": [\"12445386\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Cortical assembly not yet reconstituted\", \"Regulation of LGN-NuMA binding unknown\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Demonstrated functional conservation and domain division of labor: mammalian PINS rescues fly neuroblast division, with the TPR binding Inscuteable and the GoLoco region directing cortex localization.\",\n      \"evidence\": \"Ectopic expression and genetic rescue in Drosophila neuroblasts plus direct binding assays\",\n      \"pmids\": [\"12571286\", \"12814548\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"GDI biochemistry quantified only for worm GPR proteins\", \"Mammalian cortical recruitment mechanism not yet shown\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Defined the central mechanistic principle—LGN is an autoinhibited conformational switch whose opening by Gαi or NuMA enables simultaneous binding and cortical recruitment of partners.\",\n      \"evidence\": \"FRET biosensor, reciprocal Co-IP, and live-cell imaging in mammalian cells\",\n      \"pmids\": [\"15537540\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of the closed state not resolved\", \"Spatial restriction of cortical LGN not addressed\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Quantified GoLoco GDI activity and substrate selectivity, establishing Gαi (not Gαo/Gαs) as the physiological target and clarifying the biochemical output of the C-terminus.\",\n      \"evidence\": \"Surface plasmon resonance and fluorescence GDI assays with recombinant GoLoco motifs\",\n      \"pmids\": [\"15946753\", \"16275912\", \"15937221\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Stoichiometry and cooperativity among the four motifs not yet resolved\", \"Coupling of GDI activity to switch opening not structurally defined\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Resolved the conserved spindle-orientation effector by showing Pins binds the NuMA-related Mud and that Gαi/Mud engage Pins through distinct domains in graded activity states, linking cortical polarity to spindle alignment.\",\n      \"evidence\": \"Direct binding, Co-IP, and mud mutant genetics in Drosophila neuroblasts plus domain-state biochemistry\",\n      \"pmids\": [\"16648843\", \"17726110\", \"16377571\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How distinct GoLoco motifs partition between cortical recruitment and switch opening not yet fully separated\", \"Parallel pathway integration mechanism incomplete\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Demonstrated the vertebrate developmental role: LGN controls planar spindle orientation in neural progenitors, and its loss randomizes divisions and disrupts neuroepithelial self-renewal without altering fate decisions.\",\n      \"evidence\": \"Dominant-negative electroporation in chick and conditional knockout in mouse neuroepithelium with lineage analysis\",\n      \"pmids\": [\"17934458\", \"18084280\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Cortical anchoring machinery in vertebrates not yet defined\", \"Upstream polarity cues unresolved\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Defined how LGN cortical localization is spatially patterned and dynamically regulated, identifying aPKC/14-3-3 apical exclusion and Ric-8A/Gαi cortical recruitment of the LGN/NuMA/dynein module.\",\n      \"evidence\": \"Ser401 phosphosite mutagenesis, 14-3-3 binding, 3D cyst culture, pertussis toxin and RNAi with live imaging in MDCK/HeLa\",\n      \"pmids\": [\"20933426\", \"20385777\", \"20479129\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Force-generation step downstream of dynein not quantified\", \"Integration of multiple cortical anchors not yet unified\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Connected the spindle-orientation machinery to human disease by identifying GPSM2 truncating mutations causing nonsyndromic deafness DFNB82 with hair-cell apical localization.\",\n      \"evidence\": \"Exome sequencing, homozygosity mapping, and mouse inner-ear immunolocalization\",\n      \"pmids\": [\"20602914\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Cochlear mechanism inferred from localization rather than direct functional assay\", \"Relationship to spindle-orientation function unclear at this stage\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Provided atomic-resolution and quantitative basis for partner selection, showing mInsc and NuMA bind the LGN TPR at overlapping interfaces in a mutually exclusive, affinity-ranked manner, switching LGN between asymmetric-fate and spindle-capture complexes.\",\n      \"evidence\": \"X-ray crystallography, ITC, and competition assays of LGN/Pins TPR with NuMA and Insc\",\n      \"pmids\": [\"21816348\", \"22074847\", \"22171003\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Temporal control of the mInsc-to-NuMA handoff in cells not resolved\", \"Structure of full-length closed LGN not yet determined\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Established robustness logic: ultrasensitive Gαi activation of Pins (via GoLoco decoy motifs) sharpens the polarity-to-spindle coupling, explaining why LGN reliably aligns spindles within a narrow signal range.\",\n      \"evidence\": \"Reconstituted spindle-orientation pathway with Hill-coefficient analysis and neuroblast domain mutants; FRAP/live imaging of cortical LGN/NuMA belts\",\n      \"pmids\": [\"21855794\", \"21444683\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether mammalian LGN shows identical ultrasensitivity not tested\", \"In vivo concentration ranges of Gαi not measured\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Resolved the autoinhibited architecture and cytoskeletal coupling, showing tandem GoLoco motifs occupy the TPR concave surface and that dynein/astral-microtubule transport, opposed by actin, governs cortical LGN turnover.\",\n      \"evidence\": \"Crystal structure of truncated LGN; Co-IP with dynein heavy chain, FRAP, and cytoskeletal drug perturbation\",\n      \"pmids\": [\"23665171\", \"23389635\", \"24358023\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structure of intact closed-to-open transition not captured\", \"Quantitative force coupling to dynein unresolved\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Identified the cortical anchoring network—Dlg1, Par3/mInsc/Gαi3, and SLK-activated ERM proteins—that positions and polarizes LGN to set planar versus perpendicular division orientation in vivo.\",\n      \"evidence\": \"Direct binding, conditional knockouts and in vivo RNAi, micropatterns, and live imaging in chick/mouse/human cells\",\n      \"pmids\": [\"25202028\", \"25016959\", \"24958772\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Hierarchy among redundant anchors not fully ordered\", \"How anchors are temporally activated at mitotic entry incomplete\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Defined direct structural anchoring to cortical F-actin and a competitive negative regulator, showing Afadin bridges LGN/NuMA to actin while SAPCD2 competes with NuMA to limit cortical LGN and tune asymmetric division.\",\n      \"evidence\": \"Crystal structure of Afadin-LGN, direct binding, Co-IP, RNAi, and in vivo retinal division-angle analysis\",\n      \"pmids\": [\"26751642\", \"26766442\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Coordination between Afadin anchoring and SAPCD2 competition not integrated\", \"In vivo balance of these regulators in different tissues unmapped\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Established cadherin junctions as instructive orientation cues, showing LGN binds E-cadherin and phospho-VE-cadherin tails and is locally handed off to NuMA at mitosis, extending LGN function to endothelial flow responses.\",\n      \"evidence\": \"Direct binding, NuMA/cadherin competition assays, phosphosite mutants, and in vivo vascular remodeling\",\n      \"pmids\": [\"28045117\", \"28712573\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanistic link between flow signaling and division orientation not fully defined\", \"Generality across epithelial cadherins unresolved\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Showed a motor-independent function: a stable Insc:LGN:Gαi tetramer drives asymmetric cell fate in mammary stem cells and rescues aberrant symmetric divisions, decoupling LGN's fate role from microtubule-motor spindle capture.\",\n      \"evidence\": \"Crystal structure, SEC-SAXS, complex-stability assays, and mammary stem cell functional assays\",\n      \"pmids\": [\"29523789\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Downstream fate-determinant readout of the tetramer unidentified\", \"How tetramer resists NuMA in different cell types unknown\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Defined the cochlear molecular pathway, placing GPSM2-GNAI in series with MYO15A and WHRN to specify tallest-row stereocilia identity by stabilizing the MYO15A-EPS8 tip complex and regulating actin elongation.\",\n      \"evidence\": \"Comprehensive genetic epistasis, STED nanoscopy, single-molecule tracking, and time-course localization in mouse auditory epithelium\",\n      \"pmids\": [\"30827920\", \"28387217\", \"26662512\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How the GoLoco/Gαi GDI activity mechanistically drives actin elongation not resolved\", \"Whether spindle-orientation switch logic applies to the stereocilia nanodomain unclear\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How the various competing cortical anchors, regulators, and partner switches are temporally and spatially integrated within a single mitosis—and how the same switch protein deploys distinct mechanisms in spindle orientation versus stereocilia tip actin regulation—remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No unified model integrating Afadin/Dlg1/E-cadherin/ERM anchoring with dynein turnover\", \"Mechanistic basis of stereocilia-specific GPSM2 function distinct from mitotic role undefined\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [8, 30, 5, 11, 15]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [7, 2, 24, 38]},\n      {\"term_id\": \"GO:0008092\", \"supporting_discovery_ids\": [2, 32]},\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [27, 38, 43]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [6, 7, 20, 21, 27]},\n      {\"term_id\": \"GO:0005815\", \"supporting_discovery_ids\": [17, 23]},\n      {\"term_id\": \"GO:0005929\", \"supporting_discovery_ids\": [42, 44]},\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [3]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1640170\", \"supporting_discovery_ids\": [7, 17, 22, 27]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [17, 18, 35, 39, 43]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [8, 10, 14, 41]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [19, 29]}\n    ],\n    \"complexes\": [\n      \"Gαi/LGN/NuMA cortical complex\",\n      \"Par3/mInsc/LGN/Gαi complex\",\n      \"WHRN-GPSM2-GNAI stereocilia tip module\",\n      \"Lgl2/aPKC/Par-6/LGN complex\"\n    ],\n    \"partners\": [\n      \"GNAI1\",\n      \"NUMA1\",\n      \"INSC\",\n      \"RIC8A\",\n      \"DLG1\",\n      \"AFDN\",\n      \"CDH1\",\n      \"MYO15A\"\n    ],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":8,"faith_total":8,"faith_pct":100.0}}