{"gene":"SHTN1","run_date":"2026-06-10T07:46:32","timeline":{"discoveries":[{"year":2006,"finding":"Shootin1 (SHTN1) is a novel protein that undergoes anterograde transport to axonal growth cones and diffuses back to the soma; its asymmetric accumulation in a single neurite drives axon specification during neuronal polarization. Shootin1 is required for spatially localized phosphoinositide-3-kinase (PI3K) activity in the nascent axon.","method":"RNA interference (knockdown), overexpression in cultured hippocampal neurons, live-cell imaging of fluctuating accumulation, inhibition of anterograde transport","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (RNAi, OE, transport inhibition, PI3K readout) in a single focused study, independently cited and replicated in subsequent work","pmids":["17030985"],"is_preprint":false},{"year":2008,"finding":"Shootin1 physically interacts with both actin filament retrograde flow and L1-CAM in axonal growth cones, mechanically coupling F-actin flow to the substrate (the 'clutch' mechanism) to promote L1-dependent axon outgrowth. Disrupting either the shootin1–actin or shootin1–L1-CAM interaction inhibits axon elongation.","method":"Co-immunoprecipitation of shootin1 with L1-CAM, speckle microscopy to measure coupling with actin retrograde flow, RNAi knockdown with axon length readout, shootin1 overexpression in cultured rat hippocampal neurons","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP, speckle microscopy coupling assay, and loss-of-function phenotype all in the same study; foundational clutch mechanism replicated by multiple subsequent papers","pmids":["18519736"],"is_preprint":false},{"year":2013,"finding":"The chemoattractant netrin-1 activates Pak1 kinase, which phosphorylates shootin1a in axonal growth cones. This phosphorylation enhances shootin1's interaction with F-actin retrograde flow, thereby increasing F-actin–substrate coupling efficiency, traction force generation, and filopodium extension for axon outgrowth.","method":"In vitro kinase assay (Pak1 phosphorylating shootin1), traction force microscopy, phosphomimetic/phosphodead shootin1 mutants, fluorescence speckle microscopy of actin flow coupling in hippocampal neurons treated with netrin-1","journal":"Current biology : CB","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — in vitro kinase assay plus mutagenesis plus traction force microscopy; mechanism subsequently confirmed and extended by two independent follow-up studies","pmids":["23453953"],"is_preprint":false},{"year":2013,"finding":"Shootin1 interacts with KIF20B, a kinesin family member; this interaction (mapped to a 57-aa KIF20B domain) mediates anterograde transport of shootin1 to the developing axon. Kif20b knockdown reduces shootin1 mobilization to the axon tip and PIP3 accumulation in the growth cone. Shootin1 and KIF20B act in the same genetic pathway for neuronal polarization and multipolar-to-bipolar transition during cortical migration.","method":"Surface plasmon resonance (affinity ~10⁻⁷ M), co-immunoprecipitation in vivo, FRAP analysis of shootin1 mobility after Kif20b knockdown, in vivo migration assay with shRNA, time-lapse imaging of multipolar cells, epistasis by dominant-negative KIF20B fragment","journal":"The Journal of neuroscience : the official journal of the Society for Neuroscience","confidence":"High","confidence_rationale":"Tier 2 / Strong — SPR affinity measurement, reciprocal Co-IP, FRAP, in vivo epistasis, and time-lapse imaging in a single comprehensive study","pmids":["23864681"],"is_preprint":false},{"year":2015,"finding":"Cortactin, an F-actin binding molecule, directly interacts with shootin1 in axonal growth cones. Shootin1 phosphorylation by Pak1 (activated by netrin-1) enhances the shootin1–cortactin interaction, which in turn strengthens the linkage between F-actin retrograde flow and L1-CAM adhesions, increasing traction forces for axon outgrowth.","method":"Co-immunoprecipitation (shootin1–cortactin), phosphomimetic shootin1 mutants, traction force microscopy, F-actin flow coupling assay, RNAi knockdown of cortactin in hippocampal neurons with netrin-1 stimulation","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — Co-IP, mutagenesis, traction force microscopy, and loss-of-function all in one study; consistent with prior Pak1-shootin1 mechanism","pmids":["26261183"],"is_preprint":false},{"year":2016,"finding":"CDKL5 kinase interacts with shootin1 in vivo (co-immunoprecipitation) and both proteins localize at the distal tip of outgrowing axons. CDKL5 silencing reduces shootin1 phosphorylation, suggesting CDKL5 directly or indirectly phosphorylates shootin1. Epistasis experiments show CDKL5-induced supernumerary axon formation is attenuated by shootin1 knockdown, placing them in the same neuronal polarization pathway.","method":"Yeast two-hybrid screening, co-immunoprecipitation in primary hippocampal neurons, immunofluorescence colocalization, RNAi knockdown of CDKL5 with phospho-shootin1 western blot, epistasis by double knockdown","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP + phosphorylation western blot + epistasis in a single lab; whether CDKL5 is a direct kinase for shootin1 is not fully resolved","pmids":["26849555"],"is_preprint":false},{"year":2016,"finding":"A second shootin1 isoform, shootin1b (SHTN1b), generated by alternative splicing, is expressed in peripheral epithelial tissues (lung, liver, intestine, etc.) in addition to brain, where it co-localizes with E-cadherin and cortactin at cell–cell contact sites.","method":"Immunoblot with isoform-specific antibody, immunohistochemistry on mouse tissues, immunofluorescence colocalization with E-cadherin and cortactin","journal":"Cell and tissue research","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — isoform-specific antibody validation across multiple tissues by two orthogonal detection methods; no functional perturbation experiment for shootin1b","pmids":["27177867"],"is_preprint":false},{"year":2018,"finding":"Shootin1 activates the Notch signaling pathway through two opposing ubiquitin ligase interactions: (1) it interacts with LNX1/2 E3 ligases to promote poly-ubiquitination and degradation of Numb (a Notch inhibitor), and (2) it interacts with the Itch E3 ligase to impair poly-ubiquitination of the Notch intracellular domain (NICD), thereby stabilizing it. Both activities converge to activate Notch and modulate neuroblast cell fate in the developing brain.","method":"Co-immunoprecipitation of shootin1 with LNX1/2, Itch, Numb, and NICD; ubiquitination assays; in utero electroporation with shootin1 constructs; analysis of neuroblast fate markers in developing mouse brain","journal":"Cerebral cortex (New York, N.Y. : 1991)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP plus ubiquitination assays plus in vivo cell fate analysis in single lab; mechanistic novelty high but replication absent","pmids":["28981589"],"is_preprint":false},{"year":2020,"finding":"SHTN1 contains a noncanonical WH2 domain and an upstream proline-rich region (PRR) that are sufficient for actin binding. However, shootin1a (SHTN1S) is autoinhibited: an N-terminal coiled-coil domain (CCD) intramolecularly suppresses actin binding. Shootin1b (SHTN1L) relieves this autoinhibition via a C-terminal motif specific to the long isoform, enabling actin interaction. A nuclear localization signal between PRR and WH2 is similarly subject to CCD-dependent autoinhibition.","method":"In vitro actin co-sedimentation assay with SHTN1 deletion and domain mutants, native PAGE, domain mapping of WH2 and PRR, isoform-specific construct expression","journal":"Journal of molecular biology","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — in vitro actin binding assay with mutagenesis, but single lab with no structural validation or in-cell functional rescue","pmids":["32371045"],"is_preprint":false},{"year":2023,"finding":"Protein phosphatase 1 (PP1) dephosphorylates shootin1a in axonal growth cones. PP1 overexpression abolishes the netrin-1-induced asymmetric localization of phosphorylated shootin1a and blocks growth cone turning toward netrin-1. PP1 inhibition reverses the asymmetric phospho-shootin1a gradient, converting netrin-1-induced attraction to repulsion, demonstrating that PP1-mediated dephosphorylation is required to establish the phospho-shootin1a gradient that directs axon guidance.","method":"PP1 overexpression and pharmacological inhibition in hippocampal neurons, immunofluorescence of phospho-shootin1a distribution under netrin-1 gradient, growth cone turning assay","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic (OE) and pharmacological perturbation of PP1 combined with spatially resolved phospho-shootin1a imaging and a functional axon-turning assay; clear mechanistic demonstration","pmids":["37044214"],"is_preprint":false},{"year":2020,"finding":"In zebrafish, overexpression of shootin-1 impairs optic vesicle migration and causes retinotectal pathfinding errors; these phenotypes are rescued by overexpressing PlexinA2, placing shootin-1 downstream of Semaphorin6A/PlexinA2 repulsive guidance signaling.","method":"Zebrafish overexpression of shtn-1 and PlxnA2, microarray screen identifying shtn-1 as transcriptionally repressed by Sema6A/PlxnA2, phenotypic rescue assay","journal":"Developmental dynamics : an official publication of the American Association of Anatomists","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic epistasis (rescue) in an in vivo vertebrate model, but based on gain-of-function overexpression rather than precise loss-of-function","pmids":["32406957"],"is_preprint":false},{"year":2025,"finding":"In an FGFR2::SHTN1 oncogenic fusion protein, the coiled-coil domain II (CCD-II) of shootin1 mediates ligand-independent dimerization of FGFR2, resulting in constitutive kinase activation. Shootin1 inherently forms oligomers through its coiled-coil domains, and within the fusion this property drives receptor dimerization.","method":"Co-immunoprecipitation, native PAGE, AlphaFold/HADDOCK structural modeling, expression of SHTN1 variants in Neuro-2a cells to assess oligomerization","journal":"Turkish journal of biology","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — Co-IP and native PAGE demonstrate oligomerization; structural model supports mechanism but no mutagenesis of dimerization interface nor kinase activity assay; single lab","pmids":["41496852"],"is_preprint":false},{"year":2025,"finding":"Shootin1 and L1-CAM together constitute an integrin-independent 'slippery adhesion-clutch' that transmits weak traction forces (~100-fold weaker than integrin-based forces) from treadmilling actin filaments to the extracellular environment to drive rapid dendritic cell migration. This clutch is polarized and tunable by the chemoattractant CCL19 and the adhesive ligand laminin, mediating chemotaxis. Aberrant shootin1/L1 clutch activity also enhances glioblastoma cell motility.","method":"Traction force microscopy, RNAi knockdown of shootin1 and L1 in dendritic cells and glioblastoma cells, chemotaxis assays, live-cell imaging of actin dynamics","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — traction force microscopy plus loss-of-function in two cell types with chemotaxis readout; preprint, not yet peer-reviewed","pmids":["bio_10.1101_2025.01.13.632873"],"is_preprint":true}],"current_model":"SHTN1 (shootin1) is a clutch-linker molecule that couples F-actin retrograde flow to cell adhesion molecules (principally L1-CAM) at the leading edge of axonal growth cones and migrating cells; its coupling efficiency—and therefore traction force generation—is dynamically tuned by a Pak1-mediated phosphorylation / PP1-mediated dephosphorylation cycle that transduces extracellular guidance signals (netrin-1, CCL19) into directional mechanical forces, with cortactin serving as a direct F-actin bridge to phospho-shootin1, KIF20B as its anterograde transport motor, CDKL5 as an additional upstream kinase, and its intrinsic actin-binding activity regulated by CCD-dependent autoinhibition that is relieved in the shootin1b isoform; shootin1 also modulates neuroblast cell fate by dually controlling LNX1/2 and Itch ubiquitin ligases to activate Notch signaling."},"narrative":{"mechanistic_narrative":"SHTN1 (shootin1) is a clutch-linker protein that converts F-actin retrograde flow into directional traction force at the leading edge of polarizing neurons and migrating cells, thereby driving axon specification, axon guidance, and chemotaxis [PMID:17030985, PMID:18519736, PMID:bio_10.1101_2025.01.13.632873]. Mechanistically, shootin1 mechanically couples actin filament retrograde flow to the cell adhesion molecule L1-CAM, forming an integrin-independent adhesion clutch whose engagement is required for axon outgrowth and for rapid dendritic cell migration; disrupting either the shootin1–actin or shootin1–L1-CAM linkage abolishes force transmission [PMID:18519736, PMID:bio_10.1101_2025.01.13.632873]. Coupling strength is dynamically tuned by phosphorylation: the chemoattractant netrin-1 activates Pak1, which phosphorylates shootin1 to enhance its association with F-actin retrograde flow and with cortactin, an F-actin bridge, increasing traction force and filopodium extension, while PP1-mediated dephosphorylation establishes the asymmetric phospho-shootin1 gradient that orients growth cone turning [PMID:23453953, PMID:26261183, PMID:37044214]. Shootin1 is delivered anterogradely to the axonal growth cone by the kinesin KIF20B, and CDKL5 acts as an additional upstream kinase in the polarization pathway [PMID:23864681, PMID:26849555]. Its actin-binding activity resides in a noncanonical WH2 domain and a proline-rich region that are held under coiled-coil-dependent autoinhibition in shootin1a and relieved in the shootin1b isoform [PMID:32371045]. Beyond cytoskeletal coupling, shootin1 modulates neuroblast fate by dually engaging the LNX1/2 and Itch ubiquitin ligases to activate Notch signaling [PMID:28981589].","teleology":[{"year":2006,"claim":"Established shootin1 as a polarity determinant whose asymmetric accumulation in a single neurite specifies the axon, answering how a symmetric neuron breaks symmetry.","evidence":"RNAi, overexpression, and transport inhibition with live imaging and PI3K readout in cultured hippocampal neurons","pmids":["17030985"],"confidence":"High","gaps":["Molecular link between shootin1 accumulation and localized PI3K activity unresolved","No physical binding partner identified at this stage"]},{"year":2008,"claim":"Defined the core clutch mechanism: shootin1 physically couples F-actin retrograde flow to L1-CAM adhesions to transmit force for axon outgrowth.","evidence":"Co-IP of shootin1 with L1-CAM, speckle microscopy of actin coupling, and RNAi axon-length phenotype in rat hippocampal neurons","pmids":["18519736"],"confidence":"High","gaps":["Did not show how coupling is regulated by guidance cues","No direct measurement of traction force"]},{"year":2013,"claim":"Showed that netrin-1/Pak1 phosphorylation tunes clutch coupling, linking an extracellular guidance signal to mechanical force output.","evidence":"In vitro kinase assay, phosphomimetic/phosphodead mutants, traction force microscopy, and speckle microscopy in hippocampal neurons","pmids":["23453953"],"confidence":"High","gaps":["Phosphorylation sites and their direct effect on actin affinity not fully mapped","Counteracting dephosphorylation not yet identified"]},{"year":2013,"claim":"Identified KIF20B as the anterograde motor delivering shootin1 to the axon, explaining how the polarity cue is spatially positioned.","evidence":"SPR affinity, reciprocal Co-IP, FRAP after Kif20b knockdown, and in vivo cortical migration epistasis","pmids":["23864681"],"confidence":"High","gaps":["How KIF20B cargo loading is regulated unknown","Relationship to diffusive back-flow not detailed"]},{"year":2015,"claim":"Identified cortactin as a direct phospho-dependent F-actin bridge, refining how phosphorylation strengthens the actin linkage.","evidence":"Co-IP, phosphomimetic mutants, traction force microscopy, and cortactin RNAi in netrin-1-stimulated neurons","pmids":["26261183"],"confidence":"High","gaps":["Stoichiometry of the shootin1–cortactin–actin assembly unresolved","Whether cortactin acts in non-neuronal clutches untested"]},{"year":2016,"claim":"Placed CDKL5 as an additional upstream kinase in the shootin1 polarization pathway.","evidence":"Yeast two-hybrid, Co-IP, colocalization, phospho-shootin1 western blot after CDKL5 silencing, and double-knockdown epistasis in hippocampal neurons","pmids":["26849555"],"confidence":"Medium","gaps":["Whether CDKL5 phosphorylates shootin1 directly versus indirectly not resolved","Phosphosite not identified","Single lab"]},{"year":2016,"claim":"Discovered the shootin1b splice isoform expressed in peripheral epithelia, broadening shootin1 function beyond neurons to cell-cell contacts.","evidence":"Isoform-specific immunoblot, immunohistochemistry, and colocalization with E-cadherin and cortactin in mouse tissues","pmids":["27177867"],"confidence":"Medium","gaps":["No functional perturbation of shootin1b performed","Role at epithelial junctions not mechanistically tested"]},{"year":2018,"claim":"Revealed a non-cytoskeletal role: shootin1 activates Notch by dually controlling LNX1/2 and Itch ubiquitin ligases to set neuroblast fate.","evidence":"Co-IP with LNX1/2, Itch, Numb, NICD; ubiquitination assays; in utero electroporation and fate-marker analysis in mouse brain","pmids":["28981589"],"confidence":"Medium","gaps":["How shootin1 simultaneously coordinates two opposing ligases is unclear","Replication absent","Connection to its clutch function unknown"]},{"year":2020,"claim":"Mapped the actin-binding module to a noncanonical WH2/PRR and showed CCD-mediated autoinhibition that differs between isoforms, explaining isoform-specific actin activity.","evidence":"In vitro actin co-sedimentation, native PAGE, and domain/deletion mutagenesis with isoform-specific constructs","pmids":["32371045"],"confidence":"Medium","gaps":["No structural validation of the autoinhibited state","No in-cell functional rescue of the autoinhibition model"]},{"year":2020,"claim":"Placed shootin1 downstream of Sema6A/PlexinA2 repulsive guidance in vivo, extending its role to retinotectal pathfinding.","evidence":"Zebrafish gain-of-function with PlexinA2 rescue and microarray identifying shtn-1 as Sema6A/PlxnA2-repressed","pmids":["32406957"],"confidence":"Medium","gaps":["Based on overexpression rather than loss-of-function","Molecular link from PlexinA2 to shootin1 not defined"]},{"year":2023,"claim":"Identified PP1 as the phosphatase that opposes Pak1, establishing the dephosphorylation arm needed to build the directional phospho-shootin1 gradient for guidance.","evidence":"PP1 overexpression and pharmacological inhibition with spatially resolved phospho-shootin1a imaging and growth cone turning assays","pmids":["37044214"],"confidence":"High","gaps":["PP1 targeting/recruitment to growth cones not defined","How gradient is read out into steering not fully resolved"]},{"year":2025,"claim":"Extended the clutch model to non-neuronal migration, defining an integrin-independent slippery adhesion-clutch tunable by CCL19/laminin and relevant to glioblastoma motility.","evidence":"Traction force microscopy, shootin1/L1 RNAi, and chemotaxis assays in dendritic and glioblastoma cells (preprint)","pmids":["bio_10.1101_2025.01.13.632873"],"confidence":"Medium","gaps":["Preprint, not yet peer-reviewed","Molecular basis of the weak/slippery force regime not detailed"]},{"year":2025,"claim":"Showed shootin1 coiled-coil oligomerization can drive ligand-independent dimerization in an FGFR2::SHTN1 oncogenic fusion, implicating its self-association in disease.","evidence":"Co-IP, native PAGE, and AlphaFold/HADDOCK modeling with SHTN1 variants in Neuro-2a cells","pmids":["41496852"],"confidence":"Medium","gaps":["No mutagenesis of the dimerization interface","No kinase activity assay confirming constitutive activation","Single lab"]},{"year":null,"claim":"How the multiple inputs (Pak1, CDKL5, PP1, KIF20B transport, isoform autoinhibition) are integrated in space and time to set clutch coupling, and how the Notch/ubiquitin-ligase role relates to the cytoskeletal clutch, remain unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No unified quantitative model of phospho-regulation versus transport","Mechanistic crosstalk between clutch function and Notch signaling unknown","Human disease relevance beyond the FGFR2 fusion not established"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0008092","term_label":"cytoskeletal protein binding","supporting_discovery_ids":[1,2,4,8]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[1,4]},{"term_id":"GO:0098631","term_label":"cell adhesion mediator activity","supporting_discovery_ids":[1,12]}],"localization":[{"term_id":"GO:0005856","term_label":"cytoskeleton","supporting_discovery_ids":[1,2]},{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[1,6,12]}],"pathway":[{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[0,1,10]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[2,9,10]},{"term_id":"R-HSA-112316","term_label":"Neuronal System","supporting_discovery_ids":[0,3]}],"complexes":[],"partners":["L1CAM","CTTN","KIF20B","PAK1","CDKL5","LNX1","ITCH","ACTB"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"A0MZ66","full_name":"Shootin-1","aliases":["Shootin1"],"length_aa":631,"mass_kda":71.6,"function":"Involved in the generation of internal asymmetric signals required for neuronal polarization and neurite outgrowth. Mediates netrin-1-induced F-actin-substrate coupling or 'clutch engagement' within the axon growth cone through activation of CDC42, RAC1 and PAK1-dependent signaling pathway, thereby converting the F-actin retrograde flow into traction forces, concomitantly with filopodium extension and axon outgrowth. Plays a role in cytoskeletal organization by regulating the subcellular localization of phosphoinositide 3-kinase (PI3K) activity at the axonal growth cone. Also plays a role in regenerative neurite outgrowth. In the developing cortex, cooperates with KIF20B to promote both the transition from the multipolar to the bipolar stage and the radial migration of cortical neurons from the ventricular zone toward the superficial layer of the neocortex. Involved in the accumulation of phosphatidylinositol 3,4,5-trisphosphate (PIP3) in the growth cone of primary hippocampal neurons","subcellular_location":"Perikaryon; Cell projection, axon; Cell projection, growth cone; Cytoplasm, cytoskeleton; Cell projection, filopodium; Cell projection, lamellipodium","url":"https://www.uniprot.org/uniprotkb/A0MZ66/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/SHTN1","classification":"Not Classified","n_dependent_lines":0,"n_total_lines":1208,"dependency_fraction":0.0},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"FBL","stoichiometry":0.2},{"gene":"PSMC4","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/SHTN1","total_profiled":1310},"omim":[{"mim_id":"611171","title":"SHOOTIN1; SHTN1","url":"https://www.omim.org/entry/611171"},{"mim_id":"608449","title":"POLYPYRIMIDINE TRACT-BINDING PROTEIN 2; PTBP2","url":"https://www.omim.org/entry/608449"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Plasma membrane","reliability":"Approved"},{"location":"Cytosol","reliability":"Approved"},{"location":"Nucleoplasm","reliability":"Additional"},{"location":"Centrosome","reliability":"Additional"},{"location":"Basal body","reliability":"Additional"}],"tissue_specificity":"Tissue enriched","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"brain","ntpm":53.0}],"url":"https://www.proteinatlas.org/search/SHTN1"},"hgnc":{"alias_symbol":["shootin1","shootin-1"],"prev_symbol":["KIAA1598"]},"alphafold":{"accession":"A0MZ66","domains":[],"viewer_url":"https://alphafold.ebi.ac.uk/entry/A0MZ66","model_url":"https://alphafold.ebi.ac.uk/files/AF-A0MZ66-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-A0MZ66-F1-predicted_aligned_error_v6.png","plddt_mean":70.75},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=SHTN1","jax_strain_url":"https://www.jax.org/strain/search?query=SHTN1"},"sequence":{"accession":"A0MZ66","fasta_url":"https://rest.uniprot.org/uniprotkb/A0MZ66.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/A0MZ66/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/A0MZ66"}},"corpus_meta":[{"pmid":"17030985","id":"PMC_17030985","title":"Shootin1: A protein involved in the organization of an asymmetric signal for neuronal polarization.","date":"2006","source":"The Journal of cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/17030985","citation_count":112,"is_preprint":false},{"pmid":"18519736","id":"PMC_18519736","title":"Shootin1 interacts with actin retrograde flow and L1-CAM to promote axon outgrowth.","date":"2008","source":"The Journal of cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/18519736","citation_count":89,"is_preprint":false},{"pmid":"23453953","id":"PMC_23453953","title":"Conversion of a signal into forces for axon outgrowth through Pak1-mediated shootin1 phosphorylation.","date":"2013","source":"Current biology : CB","url":"https://pubmed.ncbi.nlm.nih.gov/23453953","citation_count":81,"is_preprint":false},{"pmid":"26261183","id":"PMC_26261183","title":"Shootin1-cortactin interaction mediates signal-force transduction for axon outgrowth.","date":"2015","source":"The Journal of cell 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motility","date":"2025-01-14","source":"bioRxiv","url":"https://doi.org/10.1101/2025.01.13.632873","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2025.01.21.634055","title":"Modeling Synaptic Maturation from Growth Cone to Synapse in Human Organoids","date":"2025-01-22","source":"bioRxiv","url":"https://doi.org/10.1101/2025.01.21.634055","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":10456,"output_tokens":4015,"usd":0.045796,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":11750,"output_tokens":4142,"usd":0.08115,"stage2_stop_reason":"end_turn"},"total_usd":0.126946,"stage1_batch_id":"msgbatch_013LWZZT6MWaqB9qyTSeQBmU","stage2_batch_id":"msgbatch_0194ZzQaTGNpruoNJBbEMbt3","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2006,\n      \"finding\": \"Shootin1 (SHTN1) is a novel protein that undergoes anterograde transport to axonal growth cones and diffuses back to the soma; its asymmetric accumulation in a single neurite drives axon specification during neuronal polarization. Shootin1 is required for spatially localized phosphoinositide-3-kinase (PI3K) activity in the nascent axon.\",\n      \"method\": \"RNA interference (knockdown), overexpression in cultured hippocampal neurons, live-cell imaging of fluctuating accumulation, inhibition of anterograde transport\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (RNAi, OE, transport inhibition, PI3K readout) in a single focused study, independently cited and replicated in subsequent work\",\n      \"pmids\": [\"17030985\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Shootin1 physically interacts with both actin filament retrograde flow and L1-CAM in axonal growth cones, mechanically coupling F-actin flow to the substrate (the 'clutch' mechanism) to promote L1-dependent axon outgrowth. Disrupting either the shootin1–actin or shootin1–L1-CAM interaction inhibits axon elongation.\",\n      \"method\": \"Co-immunoprecipitation of shootin1 with L1-CAM, speckle microscopy to measure coupling with actin retrograde flow, RNAi knockdown with axon length readout, shootin1 overexpression in cultured rat hippocampal neurons\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP, speckle microscopy coupling assay, and loss-of-function phenotype all in the same study; foundational clutch mechanism replicated by multiple subsequent papers\",\n      \"pmids\": [\"18519736\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"The chemoattractant netrin-1 activates Pak1 kinase, which phosphorylates shootin1a in axonal growth cones. This phosphorylation enhances shootin1's interaction with F-actin retrograde flow, thereby increasing F-actin–substrate coupling efficiency, traction force generation, and filopodium extension for axon outgrowth.\",\n      \"method\": \"In vitro kinase assay (Pak1 phosphorylating shootin1), traction force microscopy, phosphomimetic/phosphodead shootin1 mutants, fluorescence speckle microscopy of actin flow coupling in hippocampal neurons treated with netrin-1\",\n      \"journal\": \"Current biology : CB\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — in vitro kinase assay plus mutagenesis plus traction force microscopy; mechanism subsequently confirmed and extended by two independent follow-up studies\",\n      \"pmids\": [\"23453953\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Shootin1 interacts with KIF20B, a kinesin family member; this interaction (mapped to a 57-aa KIF20B domain) mediates anterograde transport of shootin1 to the developing axon. Kif20b knockdown reduces shootin1 mobilization to the axon tip and PIP3 accumulation in the growth cone. Shootin1 and KIF20B act in the same genetic pathway for neuronal polarization and multipolar-to-bipolar transition during cortical migration.\",\n      \"method\": \"Surface plasmon resonance (affinity ~10⁻⁷ M), co-immunoprecipitation in vivo, FRAP analysis of shootin1 mobility after Kif20b knockdown, in vivo migration assay with shRNA, time-lapse imaging of multipolar cells, epistasis by dominant-negative KIF20B fragment\",\n      \"journal\": \"The Journal of neuroscience : the official journal of the Society for Neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — SPR affinity measurement, reciprocal Co-IP, FRAP, in vivo epistasis, and time-lapse imaging in a single comprehensive study\",\n      \"pmids\": [\"23864681\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Cortactin, an F-actin binding molecule, directly interacts with shootin1 in axonal growth cones. Shootin1 phosphorylation by Pak1 (activated by netrin-1) enhances the shootin1–cortactin interaction, which in turn strengthens the linkage between F-actin retrograde flow and L1-CAM adhesions, increasing traction forces for axon outgrowth.\",\n      \"method\": \"Co-immunoprecipitation (shootin1–cortactin), phosphomimetic shootin1 mutants, traction force microscopy, F-actin flow coupling assay, RNAi knockdown of cortactin in hippocampal neurons with netrin-1 stimulation\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — Co-IP, mutagenesis, traction force microscopy, and loss-of-function all in one study; consistent with prior Pak1-shootin1 mechanism\",\n      \"pmids\": [\"26261183\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"CDKL5 kinase interacts with shootin1 in vivo (co-immunoprecipitation) and both proteins localize at the distal tip of outgrowing axons. CDKL5 silencing reduces shootin1 phosphorylation, suggesting CDKL5 directly or indirectly phosphorylates shootin1. Epistasis experiments show CDKL5-induced supernumerary axon formation is attenuated by shootin1 knockdown, placing them in the same neuronal polarization pathway.\",\n      \"method\": \"Yeast two-hybrid screening, co-immunoprecipitation in primary hippocampal neurons, immunofluorescence colocalization, RNAi knockdown of CDKL5 with phospho-shootin1 western blot, epistasis by double knockdown\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP + phosphorylation western blot + epistasis in a single lab; whether CDKL5 is a direct kinase for shootin1 is not fully resolved\",\n      \"pmids\": [\"26849555\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"A second shootin1 isoform, shootin1b (SHTN1b), generated by alternative splicing, is expressed in peripheral epithelial tissues (lung, liver, intestine, etc.) in addition to brain, where it co-localizes with E-cadherin and cortactin at cell–cell contact sites.\",\n      \"method\": \"Immunoblot with isoform-specific antibody, immunohistochemistry on mouse tissues, immunofluorescence colocalization with E-cadherin and cortactin\",\n      \"journal\": \"Cell and tissue research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — isoform-specific antibody validation across multiple tissues by two orthogonal detection methods; no functional perturbation experiment for shootin1b\",\n      \"pmids\": [\"27177867\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Shootin1 activates the Notch signaling pathway through two opposing ubiquitin ligase interactions: (1) it interacts with LNX1/2 E3 ligases to promote poly-ubiquitination and degradation of Numb (a Notch inhibitor), and (2) it interacts with the Itch E3 ligase to impair poly-ubiquitination of the Notch intracellular domain (NICD), thereby stabilizing it. Both activities converge to activate Notch and modulate neuroblast cell fate in the developing brain.\",\n      \"method\": \"Co-immunoprecipitation of shootin1 with LNX1/2, Itch, Numb, and NICD; ubiquitination assays; in utero electroporation with shootin1 constructs; analysis of neuroblast fate markers in developing mouse brain\",\n      \"journal\": \"Cerebral cortex (New York, N.Y. : 1991)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP plus ubiquitination assays plus in vivo cell fate analysis in single lab; mechanistic novelty high but replication absent\",\n      \"pmids\": [\"28981589\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"SHTN1 contains a noncanonical WH2 domain and an upstream proline-rich region (PRR) that are sufficient for actin binding. However, shootin1a (SHTN1S) is autoinhibited: an N-terminal coiled-coil domain (CCD) intramolecularly suppresses actin binding. Shootin1b (SHTN1L) relieves this autoinhibition via a C-terminal motif specific to the long isoform, enabling actin interaction. A nuclear localization signal between PRR and WH2 is similarly subject to CCD-dependent autoinhibition.\",\n      \"method\": \"In vitro actin co-sedimentation assay with SHTN1 deletion and domain mutants, native PAGE, domain mapping of WH2 and PRR, isoform-specific construct expression\",\n      \"journal\": \"Journal of molecular biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — in vitro actin binding assay with mutagenesis, but single lab with no structural validation or in-cell functional rescue\",\n      \"pmids\": [\"32371045\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Protein phosphatase 1 (PP1) dephosphorylates shootin1a in axonal growth cones. PP1 overexpression abolishes the netrin-1-induced asymmetric localization of phosphorylated shootin1a and blocks growth cone turning toward netrin-1. PP1 inhibition reverses the asymmetric phospho-shootin1a gradient, converting netrin-1-induced attraction to repulsion, demonstrating that PP1-mediated dephosphorylation is required to establish the phospho-shootin1a gradient that directs axon guidance.\",\n      \"method\": \"PP1 overexpression and pharmacological inhibition in hippocampal neurons, immunofluorescence of phospho-shootin1a distribution under netrin-1 gradient, growth cone turning assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic (OE) and pharmacological perturbation of PP1 combined with spatially resolved phospho-shootin1a imaging and a functional axon-turning assay; clear mechanistic demonstration\",\n      \"pmids\": [\"37044214\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"In zebrafish, overexpression of shootin-1 impairs optic vesicle migration and causes retinotectal pathfinding errors; these phenotypes are rescued by overexpressing PlexinA2, placing shootin-1 downstream of Semaphorin6A/PlexinA2 repulsive guidance signaling.\",\n      \"method\": \"Zebrafish overexpression of shtn-1 and PlxnA2, microarray screen identifying shtn-1 as transcriptionally repressed by Sema6A/PlxnA2, phenotypic rescue assay\",\n      \"journal\": \"Developmental dynamics : an official publication of the American Association of Anatomists\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic epistasis (rescue) in an in vivo vertebrate model, but based on gain-of-function overexpression rather than precise loss-of-function\",\n      \"pmids\": [\"32406957\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"In an FGFR2::SHTN1 oncogenic fusion protein, the coiled-coil domain II (CCD-II) of shootin1 mediates ligand-independent dimerization of FGFR2, resulting in constitutive kinase activation. Shootin1 inherently forms oligomers through its coiled-coil domains, and within the fusion this property drives receptor dimerization.\",\n      \"method\": \"Co-immunoprecipitation, native PAGE, AlphaFold/HADDOCK structural modeling, expression of SHTN1 variants in Neuro-2a cells to assess oligomerization\",\n      \"journal\": \"Turkish journal of biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — Co-IP and native PAGE demonstrate oligomerization; structural model supports mechanism but no mutagenesis of dimerization interface nor kinase activity assay; single lab\",\n      \"pmids\": [\"41496852\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Shootin1 and L1-CAM together constitute an integrin-independent 'slippery adhesion-clutch' that transmits weak traction forces (~100-fold weaker than integrin-based forces) from treadmilling actin filaments to the extracellular environment to drive rapid dendritic cell migration. This clutch is polarized and tunable by the chemoattractant CCL19 and the adhesive ligand laminin, mediating chemotaxis. Aberrant shootin1/L1 clutch activity also enhances glioblastoma cell motility.\",\n      \"method\": \"Traction force microscopy, RNAi knockdown of shootin1 and L1 in dendritic cells and glioblastoma cells, chemotaxis assays, live-cell imaging of actin dynamics\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — traction force microscopy plus loss-of-function in two cell types with chemotaxis readout; preprint, not yet peer-reviewed\",\n      \"pmids\": [\"bio_10.1101_2025.01.13.632873\"],\n      \"is_preprint\": true\n    }\n  ],\n  \"current_model\": \"SHTN1 (shootin1) is a clutch-linker molecule that couples F-actin retrograde flow to cell adhesion molecules (principally L1-CAM) at the leading edge of axonal growth cones and migrating cells; its coupling efficiency—and therefore traction force generation—is dynamically tuned by a Pak1-mediated phosphorylation / PP1-mediated dephosphorylation cycle that transduces extracellular guidance signals (netrin-1, CCL19) into directional mechanical forces, with cortactin serving as a direct F-actin bridge to phospho-shootin1, KIF20B as its anterograde transport motor, CDKL5 as an additional upstream kinase, and its intrinsic actin-binding activity regulated by CCD-dependent autoinhibition that is relieved in the shootin1b isoform; shootin1 also modulates neuroblast cell fate by dually controlling LNX1/2 and Itch ubiquitin ligases to activate Notch signaling.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"SHTN1 (shootin1) is a clutch-linker protein that converts F-actin retrograde flow into directional traction force at the leading edge of polarizing neurons and migrating cells, thereby driving axon specification, axon guidance, and chemotaxis [#0, #1, #12]. Mechanistically, shootin1 mechanically couples actin filament retrograde flow to the cell adhesion molecule L1-CAM, forming an integrin-independent adhesion clutch whose engagement is required for axon outgrowth and for rapid dendritic cell migration; disrupting either the shootin1\\u2013actin or shootin1\\u2013L1-CAM linkage abolishes force transmission [#1, #12]. Coupling strength is dynamically tuned by phosphorylation: the chemoattractant netrin-1 activates Pak1, which phosphorylates shootin1 to enhance its association with F-actin retrograde flow and with cortactin, an F-actin bridge, increasing traction force and filopodium extension, while PP1-mediated dephosphorylation establishes the asymmetric phospho-shootin1 gradient that orients growth cone turning [#2, #4, #9]. Shootin1 is delivered anterogradely to the axonal growth cone by the kinesin KIF20B, and CDKL5 acts as an additional upstream kinase in the polarization pathway [#3, #5]. Its actin-binding activity resides in a noncanonical WH2 domain and a proline-rich region that are held under coiled-coil-dependent autoinhibition in shootin1a and relieved in the shootin1b isoform [#8]. Beyond cytoskeletal coupling, shootin1 modulates neuroblast fate by dually engaging the LNX1/2 and Itch ubiquitin ligases to activate Notch signaling [#7].\",\n  \"teleology\": [\n    {\n      \"year\": 2006,\n      \"claim\": \"Established shootin1 as a polarity determinant whose asymmetric accumulation in a single neurite specifies the axon, answering how a symmetric neuron breaks symmetry.\",\n      \"evidence\": \"RNAi, overexpression, and transport inhibition with live imaging and PI3K readout in cultured hippocampal neurons\",\n      \"pmids\": [\"17030985\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular link between shootin1 accumulation and localized PI3K activity unresolved\", \"No physical binding partner identified at this stage\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Defined the core clutch mechanism: shootin1 physically couples F-actin retrograde flow to L1-CAM adhesions to transmit force for axon outgrowth.\",\n      \"evidence\": \"Co-IP of shootin1 with L1-CAM, speckle microscopy of actin coupling, and RNAi axon-length phenotype in rat hippocampal neurons\",\n      \"pmids\": [\"18519736\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not show how coupling is regulated by guidance cues\", \"No direct measurement of traction force\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Showed that netrin-1/Pak1 phosphorylation tunes clutch coupling, linking an extracellular guidance signal to mechanical force output.\",\n      \"evidence\": \"In vitro kinase assay, phosphomimetic/phosphodead mutants, traction force microscopy, and speckle microscopy in hippocampal neurons\",\n      \"pmids\": [\"23453953\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Phosphorylation sites and their direct effect on actin affinity not fully mapped\", \"Counteracting dephosphorylation not yet identified\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Identified KIF20B as the anterograde motor delivering shootin1 to the axon, explaining how the polarity cue is spatially positioned.\",\n      \"evidence\": \"SPR affinity, reciprocal Co-IP, FRAP after Kif20b knockdown, and in vivo cortical migration epistasis\",\n      \"pmids\": [\"23864681\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How KIF20B cargo loading is regulated unknown\", \"Relationship to diffusive back-flow not detailed\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Identified cortactin as a direct phospho-dependent F-actin bridge, refining how phosphorylation strengthens the actin linkage.\",\n      \"evidence\": \"Co-IP, phosphomimetic mutants, traction force microscopy, and cortactin RNAi in netrin-1-stimulated neurons\",\n      \"pmids\": [\"26261183\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Stoichiometry of the shootin1\\u2013cortactin\\u2013actin assembly unresolved\", \"Whether cortactin acts in non-neuronal clutches untested\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Placed CDKL5 as an additional upstream kinase in the shootin1 polarization pathway.\",\n      \"evidence\": \"Yeast two-hybrid, Co-IP, colocalization, phospho-shootin1 western blot after CDKL5 silencing, and double-knockdown epistasis in hippocampal neurons\",\n      \"pmids\": [\"26849555\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether CDKL5 phosphorylates shootin1 directly versus indirectly not resolved\", \"Phosphosite not identified\", \"Single lab\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Discovered the shootin1b splice isoform expressed in peripheral epithelia, broadening shootin1 function beyond neurons to cell-cell contacts.\",\n      \"evidence\": \"Isoform-specific immunoblot, immunohistochemistry, and colocalization with E-cadherin and cortactin in mouse tissues\",\n      \"pmids\": [\"27177867\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No functional perturbation of shootin1b performed\", \"Role at epithelial junctions not mechanistically tested\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Revealed a non-cytoskeletal role: shootin1 activates Notch by dually controlling LNX1/2 and Itch ubiquitin ligases to set neuroblast fate.\",\n      \"evidence\": \"Co-IP with LNX1/2, Itch, Numb, NICD; ubiquitination assays; in utero electroporation and fate-marker analysis in mouse brain\",\n      \"pmids\": [\"28981589\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"How shootin1 simultaneously coordinates two opposing ligases is unclear\", \"Replication absent\", \"Connection to its clutch function unknown\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Mapped the actin-binding module to a noncanonical WH2/PRR and showed CCD-mediated autoinhibition that differs between isoforms, explaining isoform-specific actin activity.\",\n      \"evidence\": \"In vitro actin co-sedimentation, native PAGE, and domain/deletion mutagenesis with isoform-specific constructs\",\n      \"pmids\": [\"32371045\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No structural validation of the autoinhibited state\", \"No in-cell functional rescue of the autoinhibition model\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Placed shootin1 downstream of Sema6A/PlexinA2 repulsive guidance in vivo, extending its role to retinotectal pathfinding.\",\n      \"evidence\": \"Zebrafish gain-of-function with PlexinA2 rescue and microarray identifying shtn-1 as Sema6A/PlxnA2-repressed\",\n      \"pmids\": [\"32406957\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Based on overexpression rather than loss-of-function\", \"Molecular link from PlexinA2 to shootin1 not defined\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Identified PP1 as the phosphatase that opposes Pak1, establishing the dephosphorylation arm needed to build the directional phospho-shootin1 gradient for guidance.\",\n      \"evidence\": \"PP1 overexpression and pharmacological inhibition with spatially resolved phospho-shootin1a imaging and growth cone turning assays\",\n      \"pmids\": [\"37044214\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"PP1 targeting/recruitment to growth cones not defined\", \"How gradient is read out into steering not fully resolved\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Extended the clutch model to non-neuronal migration, defining an integrin-independent slippery adhesion-clutch tunable by CCL19/laminin and relevant to glioblastoma motility.\",\n      \"evidence\": \"Traction force microscopy, shootin1/L1 RNAi, and chemotaxis assays in dendritic and glioblastoma cells (preprint)\",\n      \"pmids\": [\"bio_10.1101_2025.01.13.632873\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Preprint, not yet peer-reviewed\", \"Molecular basis of the weak/slippery force regime not detailed\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Showed shootin1 coiled-coil oligomerization can drive ligand-independent dimerization in an FGFR2::SHTN1 oncogenic fusion, implicating its self-association in disease.\",\n      \"evidence\": \"Co-IP, native PAGE, and AlphaFold/HADDOCK modeling with SHTN1 variants in Neuro-2a cells\",\n      \"pmids\": [\"41496852\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No mutagenesis of the dimerization interface\", \"No kinase activity assay confirming constitutive activation\", \"Single lab\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How the multiple inputs (Pak1, CDKL5, PP1, KIF20B transport, isoform autoinhibition) are integrated in space and time to set clutch coupling, and how the Notch/ubiquitin-ligase role relates to the cytoskeletal clutch, remain unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No unified quantitative model of phospho-regulation versus transport\", \"Mechanistic crosstalk between clutch function and Notch signaling unknown\", \"Human disease relevance beyond the FGFR2 fusion not established\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0003779\", \"supporting_discovery_ids\": [8]},\n      {\"term_id\": \"GO:0008092\", \"supporting_discovery_ids\": [1, 2, 4, 8]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [1, 4]},\n      {\"term_id\": \"GO:0098631\", \"supporting_discovery_ids\": [1, 12]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005856\", \"supporting_discovery_ids\": [1, 2]},\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [1, 6, 12]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [0, 1, 10]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [2, 9, 10]},\n      {\"term_id\": \"R-HSA-112316\", \"supporting_discovery_ids\": [0, 3]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"L1CAM\", \"CTTN\", \"KIF20B\", \"PAK1\", \"CDKL5\", \"LNX1\", \"ITCH\", \"ACTB\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":6,"faith_total":6,"faith_pct":100.0}}