{"gene":"PACSIN3","run_date":"2026-06-10T05:19:53","timeline":{"discoveries":[{"year":2003,"finding":"PACSIN3 binds the cytoplasmic domain of ADAM12/meltrin alpha via a proline-rich region (residues 829-840) of ADAM12, as demonstrated by yeast two-hybrid screening, GST pull-down, co-immunoprecipitation, and co-localization. PACSIN3 overexpression enhanced TPA-induced proHB-EGF shedding, and siRNA knockdown of PACSIN3 attenuated proHB-EGF shedding induced by TPA and angiotensin II, establishing PACSIN3 as an up-regulator of ADAM12-mediated ectodomain shedding.","method":"Yeast two-hybrid, GST pull-down, co-immunoprecipitation, co-localization, overexpression and siRNA knockdown with functional shedding assay","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (Y2H, GST pulldown, reciprocal Co-IP, co-localization, siRNA KD, OE) in a single study with defined functional readout","pmids":["12952982"],"is_preprint":false},{"year":2007,"finding":"PACSIN3 overexpression in 3T3-L1 adipocytes elevated glucose uptake by specifically increasing GLUT1 plasma membrane localization (shown by subcellular fractionation and photoaffinity labeling), without affecting GLUT4 distribution, establishing a role for PACSIN3 in GLUT1 trafficking.","method":"Overexpression in 3T3-L1 adipocytes, subcellular fractionation, photoaffinity labeling, glucose uptake assay","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — two orthogonal methods (fractionation + photoaffinity labeling) with functional glucose uptake readout, single lab","pmids":["17320047"],"is_preprint":false},{"year":2007,"finding":"PACSIN3 was identified as a FasL-interacting protein in Schwann cells via proteomics, placing it among endocytosis/trafficking regulators that control FasL surface expression in the nervous system.","method":"Proteomics/co-immunoprecipitation screen","journal":"FEBS letters","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single proteomics screen, no functional follow-up for PACSIN3 specifically","pmids":["17761170"],"is_preprint":false},{"year":2009,"finding":"Zebrafish Pacsin3 (ortholog) is required for notochord formation: morpholino knockdown caused failure of axial mesodermal cell polarization, migration, and differentiation, resulting in stunted body axis. Rescue by Drosophila Syndapin required an intact membrane-inserting prong on the EFC domain and high-affinity phosphoinositide binding, defining structural requirements for its membrane-active scaffolding function in endocytosis-coupled cell migration.","method":"Morpholino knockdown in zebrafish, ectopic expression rescue, structural analysis of Drosophila Syndapin EFC domain, biochemical phosphoinositide binding assays","journal":"PloS one","confidence":"High","confidence_rationale":"Tier 2 / Strong — combined structural, biochemical, and reverse-genetic approaches with defined rescue requirements across orthologous proteins","pmids":["19997509"],"is_preprint":false},{"year":2013,"finding":"PACSIN3 binds the N-terminal tail of TRPV4 and abrogates TRPV4 activation by cell swelling and heat. PACSIN3 lacking the F-BAR domain interacted with TRPV4 without affecting channel activation or tail rearrangement, indicating the F-BAR domain is necessary for the inhibitory effect. PACSIN3 binding restricts PIP2 access to TRPV4, as evidenced by increased proximity of TRPV4 tails (FRET) upon PACSIN3 coexpression, similar to PIP2 depletion.","method":"Co-expression in heterologous systems, FRET analysis of TRPV4 tail proximity, domain-deletion constructs, electrophysiology","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (FRET, functional channel recordings, domain-deletion analysis) with mechanistic interpretation, replicated across cell types","pmids":["23690576"],"is_preprint":false},{"year":2018,"finding":"NMR structure of the PACSIN3 SH3 domain in complex with the TRPV4 N-terminal proline-rich region (PRR) showed the PRR binds as a class I polyproline II (PPII) helix with a conserved cis-proline breaking the PPII conformation. SH3 domain binding rigidifies both the PRR and the adjacent PIP2 binding site. Binding affinities of TRPV4 N-terminus for PACSIN1, 2, and 3 SH3 domains and PIP2 were determined, revealing a hierarchical interaction network where PACSIN/Syndapin binding influences the PIP2 binding site but not vice versa.","method":"NMR structure determination, binding affinity measurements (ITC/NMR), mutagenesis","journal":"Structure (London, England : 1993)","confidence":"High","confidence_rationale":"Tier 1 / Strong — NMR structure with functional validation, affinity measurements, and mechanistic dissection of the PIP2/PACSIN interaction hierarchy in a single rigorous study","pmids":["30244966"],"is_preprint":false},{"year":2021,"finding":"PACSIN3 positions the mechanosensitive Piezo1 channel at the intercellular bridge (ICB) during cytokinesis. Genetic inhibition of Pacsin3 caused mislocation of Rab11-FIP3 endosomes, ALIX, and ESCRT-III components, leading to defective abscission and multinucleation, placing PACSIN3 upstream of Piezo1-dependent endosome trafficking in cytokinetic abscission.","method":"Genetic inhibition (knockdown), live-cell imaging of ICB, immunofluorescence localization of Piezo1/endosomal markers, functional abscission assay (multinucleation readout)","journal":"Science advances","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic inhibition with defined localization and functional readouts, single lab","pmids":["34714681"],"is_preprint":false},{"year":2019,"finding":"IL-6 downregulates Pacsin3 protein post-transcriptionally (not transcriptionally) in differentiating primary rat skeletal myoblasts; this effect was not seen with IGF-I, suggesting cytokine-specific post-transcriptional regulation involving miR-154-3p and miR-338-3p.","method":"miRNA microarray, qRT-PCR, Western blot in primary skeletal muscle cells treated with IL-6 or IGF-I","journal":"Cell and tissue research","confidence":"Low","confidence_rationale":"Tier 3 / Weak — Western blot with cytokine treatment, no direct demonstration of miRNA-mediated repression of PACSIN3 mRNA","pmids":["31820147"],"is_preprint":false},{"year":2022,"finding":"PACSIN3 is required for caveolar biogenesis in muscle tissue, creating membrane reservoirs that control muscle function; its loss is linked to muscular disorders.","method":"Review summarizing in vivo genetic/loss-of-function studies in mouse muscle","journal":"Acta physiologica (Oxford, England)","confidence":"Low","confidence_rationale":"Tier 3 / Weak — review article summarizing published findings; no primary experimental data from this paper itself","pmids":["34990060"],"is_preprint":false}],"current_model":"PACSIN3 is an F-BAR/SH3 domain scaffold protein that (1) binds the TRPV4 channel N-terminal proline-rich region through its SH3 domain (NMR-defined class I PPII helix interaction), rigidifying the adjacent PIP2 binding site and thereby restricting PIP2 access to inhibit TRPV4 activation by mechanical and thermal stimuli; (2) interacts with ADAM12 cytoplasmic tail via SH3–proline-rich region contact to up-regulate proHB-EGF ectodomain shedding; (3) promotes GLUT1 plasma membrane localization to increase glucose uptake in adipocytes; (4) positions Piezo1 at the intercellular bridge to control endosome trafficking during cytokinetic abscission; and (5) is required for notochord formation in zebrafish through its membrane-tubulating EFC domain and phosphoinositide-binding activity."},"narrative":{"mechanistic_narrative":"PACSIN3 is a membrane-active F-BAR/SH3 scaffold protein that couples its membrane-tubulating and phosphoinositide-binding activities to the regulation of plasma membrane channels, receptors, and trafficking compartments [PMID:19997509, PMID:23690576]. Through its SH3 domain it engages proline-rich cytoplasmic regions of partner proteins: it binds the N-terminal proline-rich region of the TRPV4 channel as a class I polyproline II helix and rigidifies the adjacent PIP2 binding site, an interaction that, together with the F-BAR domain, restricts PIP2 access and inhibits TRPV4 activation by cell swelling and heat [PMID:23690576, PMID:30244966]. By an analogous SH3–proline-rich contact it binds the ADAM12 cytoplasmic tail and up-regulates ADAM12-mediated proHB-EGF ectodomain shedding [PMID:12952982]. PACSIN3 also directs membrane trafficking: it promotes GLUT1 plasma membrane localization to increase glucose uptake in adipocytes [PMID:17320047] and positions the mechanosensitive Piezo1 channel at the intercellular bridge to control Rab11-FIP3 endosome and ESCRT-III delivery during cytokinetic abscission [PMID:34714681]. Its scaffolding role requires an intact membrane-inserting EFC/F-BAR prong and high-affinity phosphoinositide binding, which are needed for axial mesoderm cell polarization and notochord formation in zebrafish [PMID:19997509].","teleology":[{"year":2003,"claim":"Established PACSIN3 as a cytoplasmic adaptor for the metalloprotease ADAM12 and a positive regulator of ectodomain shedding, defining its first molecular partner and functional output.","evidence":"Yeast two-hybrid, GST pull-down, reciprocal Co-IP, co-localization, and overexpression/siRNA shedding assays mapping binding to ADAM12 residues 829-840","pmids":["12952982"],"confidence":"High","gaps":["Did not resolve which PACSIN3 domain mediates ADAM12 binding","Mechanism by which PACSIN3 enhances shedding (trafficking vs. activation) not defined"]},{"year":2007,"claim":"Extended PACSIN3 function to glucose transporter trafficking, showing it selectively routes GLUT1 to the plasma membrane.","evidence":"Overexpression in 3T3-L1 adipocytes with subcellular fractionation, photoaffinity labeling, and glucose uptake assays","pmids":["17320047"],"confidence":"Medium","gaps":["Direct physical interaction with GLUT1 not demonstrated","Single lab, overexpression-based; loss-of-function effect untested","No GLUT4 effect, leaving the basis for cargo selectivity unexplained"]},{"year":2007,"claim":"Identified PACSIN3 in a FasL interactome in Schwann cells, hinting at a broader role in surface receptor trafficking in the nervous system.","evidence":"Proteomics/co-immunoprecipitation screen","pmids":["17761170"],"confidence":"Low","gaps":["Single proteomics screen with no PACSIN3-specific functional follow-up","Direct binding and physiological relevance unconfirmed"]},{"year":2009,"claim":"Defined the structural requirements for PACSIN3's membrane-active scaffolding in vivo, linking EFC/F-BAR membrane insertion and phosphoinositide binding to morphogenetic cell migration.","evidence":"Morpholino knockdown in zebrafish with cross-species rescue by Drosophila Syndapin EFC mutants and biochemical phosphoinositide binding assays","pmids":["19997509"],"confidence":"High","gaps":["Molecular cargo or partners driving notochord cell migration not identified","Endocytic step coupled to migration not directly visualized"]},{"year":2013,"claim":"Revealed PACSIN3 as a negative regulator of TRPV4, showing it inhibits mechanical and thermal channel activation in an F-BAR-dependent manner by limiting PIP2 access.","evidence":"Heterologous co-expression, FRET of TRPV4 tail proximity, F-BAR deletion constructs, and electrophysiology","pmids":["23690576"],"confidence":"High","gaps":["How the F-BAR domain mechanically restricts PIP2 access was not structurally resolved","Physiological context of TRPV4 inhibition in tissue not addressed"]},{"year":2018,"claim":"Provided atomic-resolution mechanism for the PACSIN3–TRPV4 interaction and established a hierarchical SH3/PIP2 binding network at the TRPV4 N-terminus.","evidence":"NMR structure of PACSIN3 SH3–TRPV4 PRR complex with ITC/NMR affinity measurements and mutagenesis","pmids":["30244966"],"confidence":"High","gaps":["Full-length channel/PACSIN3 architecture not determined","Functional consequence of the cis-proline conformational switch on gating not tested directly"]},{"year":2019,"claim":"Implicated cytokine signaling in controlling PACSIN3 abundance, showing IL-6 represses PACSIN3 protein post-transcriptionally during myoblast differentiation.","evidence":"miRNA microarray, qRT-PCR, and Western blot in IL-6- or IGF-I-treated primary rat skeletal myoblasts","pmids":["31820147"],"confidence":"Low","gaps":["No direct demonstration that miR-154-3p/miR-338-3p repress PACSIN3 mRNA","Functional consequence of PACSIN3 loss in myogenesis not tested here"]},{"year":2021,"claim":"Placed PACSIN3 upstream of Piezo1-dependent endosome trafficking in cytokinesis, connecting it to the membrane scission machinery of abscission.","evidence":"Genetic knockdown with live-cell imaging of the intercellular bridge, immunolocalization of Piezo1/Rab11-FIP3/ALIX/ESCRT-III, and multinucleation readout","pmids":["34714681"],"confidence":"Medium","gaps":["Direct PACSIN3–Piezo1 interaction not biochemically demonstrated","Single lab; mechanism of endosome mispositioning not resolved at molecular detail"]},{"year":null,"claim":"Whether the diverse PACSIN3 functions (channel regulation, cargo trafficking, caveolar biogenesis, cytokinesis) reflect one unified membrane-remodeling activity or distinct context-specific roles remains unresolved.","evidence":"","pmids":[],"confidence":"Low","gaps":["No unified structural/functional model linking F-BAR membrane tubulation to its various cargo outputs","Endogenous tissue-specific partner inventory incomplete","Direct disease-causing mutations not defined in primary data"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[0,4,6]},{"term_id":"GO:0008289","term_label":"lipid binding","supporting_discovery_ids":[3,5]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[0,4]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[1,4]},{"term_id":"GO:0005768","term_label":"endosome","supporting_discovery_ids":[6]}],"pathway":[{"term_id":"R-HSA-9609507","term_label":"Protein localization","supporting_discovery_ids":[1,6]},{"term_id":"R-HSA-1640170","term_label":"Cell Cycle","supporting_discovery_ids":[6]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[3]}],"complexes":[],"partners":["TRPV4","ADAM12","GLUT1","PIEZO1","FASL"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q9UKS6","full_name":"Protein kinase C and casein kinase substrate in neurons protein 3","aliases":["SH3 domain-containing protein 6511"],"length_aa":424,"mass_kda":48.5,"function":"Plays a role in endocytosis and regulates internalization of plasma membrane proteins. Overexpression impairs internalization of SLC2A1/GLUT1 and TRPV4 and increases the levels of SLC2A1/GLUT1 and TRPV4 at the cell membrane. Inhibits the TRPV4 calcium channel activity (By similarity)","subcellular_location":"Cytoplasm; Cell membrane","url":"https://www.uniprot.org/uniprotkb/Q9UKS6/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/PACSIN3","classification":"Not Classified","n_dependent_lines":19,"n_total_lines":1208,"dependency_fraction":0.015728476821192054},"opencell":{"profiled":true,"resolved_as":"","ensg_id":"ENSG00000165912","cell_line_id":"CID000663","localizations":[{"compartment":"membrane","grade":3},{"compartment":"cell_contact","grade":2},{"compartment":"cytoplasmic","grade":1}],"interactors":[{"gene":"COBL","stoichiometry":4.0},{"gene":"CCDC22","stoichiometry":0.2},{"gene":"CCDC93","stoichiometry":0.2},{"gene":"COMMD4","stoichiometry":0.2},{"gene":"PACSIN2","stoichiometry":0.2},{"gene":"PATL1","stoichiometry":0.2},{"gene":"RAI14","stoichiometry":0.2},{"gene":"TRIOBP","stoichiometry":0.2},{"gene":"COBLL1","stoichiometry":0.2},{"gene":"MPRIP","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/target/CID000663","total_profiled":1310},"omim":[{"mim_id":"621343","title":"CONGENITAL MYOPATHY 27; CMYO27","url":"https://www.omim.org/entry/621343"},{"mim_id":"606513","title":"PROTEIN KINASE C AND CASEIN KINASE SUBSTRATE IN NEURONS 3; PACSIN3","url":"https://www.omim.org/entry/606513"},{"mim_id":"606512","title":"PROTEIN KINASE C AND CASEIN KINASE SUBSTRATE IN NEURONS 1; PACSIN1","url":"https://www.omim.org/entry/606512"},{"mim_id":"143100","title":"HUNTINGTON DISEASE; HD","url":"https://www.omim.org/entry/143100"},{"mim_id":"138140","title":"SOLUTE CARRIER FAMILY 2 (FACILITATED GLUCOSE TRANSPORTER), MEMBER 1; SLC2A1","url":"https://www.omim.org/entry/138140"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Cytosol","reliability":"Supported"},{"location":"Plasma membrane","reliability":"Additional"}],"tissue_specificity":"Group enriched","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"heart muscle","ntpm":155.2},{"tissue":"skeletal muscle","ntpm":450.8},{"tissue":"tongue","ntpm":260.7}],"url":"https://www.proteinatlas.org/search/PACSIN3"},"hgnc":{"alias_symbol":["SDPIII"],"prev_symbol":[]},"alphafold":{"accession":"Q9UKS6","domains":[{"cath_id":"1.20.1270.60","chopping":"16-290","consensus_level":"medium","plddt":97.1747,"start":16,"end":290},{"cath_id":"2.30.30.40","chopping":"365-420","consensus_level":"high","plddt":89.8054,"start":365,"end":420}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9UKS6","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9UKS6-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9UKS6-F1-predicted_aligned_error_v6.png","plddt_mean":86.06},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=PACSIN3","jax_strain_url":"https://www.jax.org/strain/search?query=PACSIN3"},"sequence":{"accession":"Q9UKS6","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9UKS6.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9UKS6/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9UKS6"}},"corpus_meta":[{"pmid":"23690576","id":"PMC_23690576","title":"Phosphatidylinositol-4,5-biphosphate-dependent rearrangement of TRPV4 cytosolic tails enables channel activation by physiological stimuli.","date":"2013","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/23690576","citation_count":123,"is_preprint":false},{"pmid":"12952982","id":"PMC_12952982","title":"PACSIN3 binds ADAM12/meltrin alpha and up-regulates ectodomain shedding of heparin-binding epidermal growth factor-like growth factor.","date":"2003","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/12952982","citation_count":74,"is_preprint":false},{"pmid":"19997509","id":"PMC_19997509","title":"Structural requirements for PACSIN/Syndapin operation during zebrafish embryonic notochord development.","date":"2009","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/19997509","citation_count":39,"is_preprint":false},{"pmid":"34990060","id":"PMC_34990060","title":"PACSIN proteins in vivo: Roles in development and physiology.","date":"2022","source":"Acta physiologica (Oxford, England)","url":"https://pubmed.ncbi.nlm.nih.gov/34990060","citation_count":34,"is_preprint":false},{"pmid":"30244966","id":"PMC_30244966","title":"Structural Basis of TRPV4 N Terminus Interaction with Syndapin/PACSIN1-3 and PIP2.","date":"2018","source":"Structure (London, England : 1993)","url":"https://pubmed.ncbi.nlm.nih.gov/30244966","citation_count":34,"is_preprint":false},{"pmid":"18179684","id":"PMC_18179684","title":"Identification and transcript analysis of a novel wallaby (Macropus eugenii) basal-like breast cancer cell line.","date":"2008","source":"Molecular cancer","url":"https://pubmed.ncbi.nlm.nih.gov/18179684","citation_count":29,"is_preprint":false},{"pmid":"34714681","id":"PMC_34714681","title":"The mechanosensitive Piezo1 channel controls endosome trafficking for an efficient cytokinetic abscission.","date":"2021","source":"Science advances","url":"https://pubmed.ncbi.nlm.nih.gov/34714681","citation_count":25,"is_preprint":false},{"pmid":"31041394","id":"PMC_31041394","title":"Homozygous TRPV4 mutation causes congenital distal spinal muscular atrophy and arthrogryposis.","date":"2019","source":"Neurology. 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PACSIN3 overexpression enhanced TPA-induced proHB-EGF shedding, and siRNA knockdown of PACSIN3 attenuated proHB-EGF shedding induced by TPA and angiotensin II, establishing PACSIN3 as an up-regulator of ADAM12-mediated ectodomain shedding.\",\n      \"method\": \"Yeast two-hybrid, GST pull-down, co-immunoprecipitation, co-localization, overexpression and siRNA knockdown with functional shedding assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (Y2H, GST pulldown, reciprocal Co-IP, co-localization, siRNA KD, OE) in a single study with defined functional readout\",\n      \"pmids\": [\"12952982\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"PACSIN3 overexpression in 3T3-L1 adipocytes elevated glucose uptake by specifically increasing GLUT1 plasma membrane localization (shown by subcellular fractionation and photoaffinity labeling), without affecting GLUT4 distribution, establishing a role for PACSIN3 in GLUT1 trafficking.\",\n      \"method\": \"Overexpression in 3T3-L1 adipocytes, subcellular fractionation, photoaffinity labeling, glucose uptake assay\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — two orthogonal methods (fractionation + photoaffinity labeling) with functional glucose uptake readout, single lab\",\n      \"pmids\": [\"17320047\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"PACSIN3 was identified as a FasL-interacting protein in Schwann cells via proteomics, placing it among endocytosis/trafficking regulators that control FasL surface expression in the nervous system.\",\n      \"method\": \"Proteomics/co-immunoprecipitation screen\",\n      \"journal\": \"FEBS letters\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single proteomics screen, no functional follow-up for PACSIN3 specifically\",\n      \"pmids\": [\"17761170\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Zebrafish Pacsin3 (ortholog) is required for notochord formation: morpholino knockdown caused failure of axial mesodermal cell polarization, migration, and differentiation, resulting in stunted body axis. Rescue by Drosophila Syndapin required an intact membrane-inserting prong on the EFC domain and high-affinity phosphoinositide binding, defining structural requirements for its membrane-active scaffolding function in endocytosis-coupled cell migration.\",\n      \"method\": \"Morpholino knockdown in zebrafish, ectopic expression rescue, structural analysis of Drosophila Syndapin EFC domain, biochemical phosphoinositide binding assays\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — combined structural, biochemical, and reverse-genetic approaches with defined rescue requirements across orthologous proteins\",\n      \"pmids\": [\"19997509\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"PACSIN3 binds the N-terminal tail of TRPV4 and abrogates TRPV4 activation by cell swelling and heat. PACSIN3 lacking the F-BAR domain interacted with TRPV4 without affecting channel activation or tail rearrangement, indicating the F-BAR domain is necessary for the inhibitory effect. PACSIN3 binding restricts PIP2 access to TRPV4, as evidenced by increased proximity of TRPV4 tails (FRET) upon PACSIN3 coexpression, similar to PIP2 depletion.\",\n      \"method\": \"Co-expression in heterologous systems, FRET analysis of TRPV4 tail proximity, domain-deletion constructs, electrophysiology\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (FRET, functional channel recordings, domain-deletion analysis) with mechanistic interpretation, replicated across cell types\",\n      \"pmids\": [\"23690576\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"NMR structure of the PACSIN3 SH3 domain in complex with the TRPV4 N-terminal proline-rich region (PRR) showed the PRR binds as a class I polyproline II (PPII) helix with a conserved cis-proline breaking the PPII conformation. SH3 domain binding rigidifies both the PRR and the adjacent PIP2 binding site. Binding affinities of TRPV4 N-terminus for PACSIN1, 2, and 3 SH3 domains and PIP2 were determined, revealing a hierarchical interaction network where PACSIN/Syndapin binding influences the PIP2 binding site but not vice versa.\",\n      \"method\": \"NMR structure determination, binding affinity measurements (ITC/NMR), mutagenesis\",\n      \"journal\": \"Structure (London, England : 1993)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — NMR structure with functional validation, affinity measurements, and mechanistic dissection of the PIP2/PACSIN interaction hierarchy in a single rigorous study\",\n      \"pmids\": [\"30244966\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"PACSIN3 positions the mechanosensitive Piezo1 channel at the intercellular bridge (ICB) during cytokinesis. Genetic inhibition of Pacsin3 caused mislocation of Rab11-FIP3 endosomes, ALIX, and ESCRT-III components, leading to defective abscission and multinucleation, placing PACSIN3 upstream of Piezo1-dependent endosome trafficking in cytokinetic abscission.\",\n      \"method\": \"Genetic inhibition (knockdown), live-cell imaging of ICB, immunofluorescence localization of Piezo1/endosomal markers, functional abscission assay (multinucleation readout)\",\n      \"journal\": \"Science advances\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic inhibition with defined localization and functional readouts, single lab\",\n      \"pmids\": [\"34714681\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"IL-6 downregulates Pacsin3 protein post-transcriptionally (not transcriptionally) in differentiating primary rat skeletal myoblasts; this effect was not seen with IGF-I, suggesting cytokine-specific post-transcriptional regulation involving miR-154-3p and miR-338-3p.\",\n      \"method\": \"miRNA microarray, qRT-PCR, Western blot in primary skeletal muscle cells treated with IL-6 or IGF-I\",\n      \"journal\": \"Cell and tissue research\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — Western blot with cytokine treatment, no direct demonstration of miRNA-mediated repression of PACSIN3 mRNA\",\n      \"pmids\": [\"31820147\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"PACSIN3 is required for caveolar biogenesis in muscle tissue, creating membrane reservoirs that control muscle function; its loss is linked to muscular disorders.\",\n      \"method\": \"Review summarizing in vivo genetic/loss-of-function studies in mouse muscle\",\n      \"journal\": \"Acta physiologica (Oxford, England)\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — review article summarizing published findings; no primary experimental data from this paper itself\",\n      \"pmids\": [\"34990060\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"PACSIN3 is an F-BAR/SH3 domain scaffold protein that (1) binds the TRPV4 channel N-terminal proline-rich region through its SH3 domain (NMR-defined class I PPII helix interaction), rigidifying the adjacent PIP2 binding site and thereby restricting PIP2 access to inhibit TRPV4 activation by mechanical and thermal stimuli; (2) interacts with ADAM12 cytoplasmic tail via SH3–proline-rich region contact to up-regulate proHB-EGF ectodomain shedding; (3) promotes GLUT1 plasma membrane localization to increase glucose uptake in adipocytes; (4) positions Piezo1 at the intercellular bridge to control endosome trafficking during cytokinetic abscission; and (5) is required for notochord formation in zebrafish through its membrane-tubulating EFC domain and phosphoinositide-binding activity.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"PACSIN3 is a membrane-active F-BAR/SH3 scaffold protein that couples its membrane-tubulating and phosphoinositide-binding activities to the regulation of plasma membrane channels, receptors, and trafficking compartments [#3, #4]. Through its SH3 domain it engages proline-rich cytoplasmic regions of partner proteins: it binds the N-terminal proline-rich region of the TRPV4 channel as a class I polyproline II helix and rigidifies the adjacent PIP2 binding site, an interaction that, together with the F-BAR domain, restricts PIP2 access and inhibits TRPV4 activation by cell swelling and heat [#4, #5]. By an analogous SH3\\u2013proline-rich contact it binds the ADAM12 cytoplasmic tail and up-regulates ADAM12-mediated proHB-EGF ectodomain shedding [#0]. PACSIN3 also directs membrane trafficking: it promotes GLUT1 plasma membrane localization to increase glucose uptake in adipocytes [#1] and positions the mechanosensitive Piezo1 channel at the intercellular bridge to control Rab11-FIP3 endosome and ESCRT-III delivery during cytokinetic abscission [#6]. Its scaffolding role requires an intact membrane-inserting EFC/F-BAR prong and high-affinity phosphoinositide binding, which are needed for axial mesoderm cell polarization and notochord formation in zebrafish [#3].\",\n  \"teleology\": [\n    {\n      \"year\": 2003,\n      \"claim\": \"Established PACSIN3 as a cytoplasmic adaptor for the metalloprotease ADAM12 and a positive regulator of ectodomain shedding, defining its first molecular partner and functional output.\",\n      \"evidence\": \"Yeast two-hybrid, GST pull-down, reciprocal Co-IP, co-localization, and overexpression/siRNA shedding assays mapping binding to ADAM12 residues 829-840\",\n      \"pmids\": [\"12952982\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not resolve which PACSIN3 domain mediates ADAM12 binding\", \"Mechanism by which PACSIN3 enhances shedding (trafficking vs. activation) not defined\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Extended PACSIN3 function to glucose transporter trafficking, showing it selectively routes GLUT1 to the plasma membrane.\",\n      \"evidence\": \"Overexpression in 3T3-L1 adipocytes with subcellular fractionation, photoaffinity labeling, and glucose uptake assays\",\n      \"pmids\": [\"17320047\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct physical interaction with GLUT1 not demonstrated\", \"Single lab, overexpression-based; loss-of-function effect untested\", \"No GLUT4 effect, leaving the basis for cargo selectivity unexplained\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Identified PACSIN3 in a FasL interactome in Schwann cells, hinting at a broader role in surface receptor trafficking in the nervous system.\",\n      \"evidence\": \"Proteomics/co-immunoprecipitation screen\",\n      \"pmids\": [\"17761170\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Single proteomics screen with no PACSIN3-specific functional follow-up\", \"Direct binding and physiological relevance unconfirmed\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Defined the structural requirements for PACSIN3's membrane-active scaffolding in vivo, linking EFC/F-BAR membrane insertion and phosphoinositide binding to morphogenetic cell migration.\",\n      \"evidence\": \"Morpholino knockdown in zebrafish with cross-species rescue by Drosophila Syndapin EFC mutants and biochemical phosphoinositide binding assays\",\n      \"pmids\": [\"19997509\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular cargo or partners driving notochord cell migration not identified\", \"Endocytic step coupled to migration not directly visualized\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Revealed PACSIN3 as a negative regulator of TRPV4, showing it inhibits mechanical and thermal channel activation in an F-BAR-dependent manner by limiting PIP2 access.\",\n      \"evidence\": \"Heterologous co-expression, FRET of TRPV4 tail proximity, F-BAR deletion constructs, and electrophysiology\",\n      \"pmids\": [\"23690576\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How the F-BAR domain mechanically restricts PIP2 access was not structurally resolved\", \"Physiological context of TRPV4 inhibition in tissue not addressed\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Provided atomic-resolution mechanism for the PACSIN3\\u2013TRPV4 interaction and established a hierarchical SH3/PIP2 binding network at the TRPV4 N-terminus.\",\n      \"evidence\": \"NMR structure of PACSIN3 SH3\\u2013TRPV4 PRR complex with ITC/NMR affinity measurements and mutagenesis\",\n      \"pmids\": [\"30244966\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Full-length channel/PACSIN3 architecture not determined\", \"Functional consequence of the cis-proline conformational switch on gating not tested directly\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Implicated cytokine signaling in controlling PACSIN3 abundance, showing IL-6 represses PACSIN3 protein post-transcriptionally during myoblast differentiation.\",\n      \"evidence\": \"miRNA microarray, qRT-PCR, and Western blot in IL-6- or IGF-I-treated primary rat skeletal myoblasts\",\n      \"pmids\": [\"31820147\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No direct demonstration that miR-154-3p/miR-338-3p repress PACSIN3 mRNA\", \"Functional consequence of PACSIN3 loss in myogenesis not tested here\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Placed PACSIN3 upstream of Piezo1-dependent endosome trafficking in cytokinesis, connecting it to the membrane scission machinery of abscission.\",\n      \"evidence\": \"Genetic knockdown with live-cell imaging of the intercellular bridge, immunolocalization of Piezo1/Rab11-FIP3/ALIX/ESCRT-III, and multinucleation readout\",\n      \"pmids\": [\"34714681\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct PACSIN3\\u2013Piezo1 interaction not biochemically demonstrated\", \"Single lab; mechanism of endosome mispositioning not resolved at molecular detail\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Whether the diverse PACSIN3 functions (channel regulation, cargo trafficking, caveolar biogenesis, cytokinesis) reflect one unified membrane-remodeling activity or distinct context-specific roles remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No unified structural/functional model linking F-BAR membrane tubulation to its various cargo outputs\", \"Endogenous tissue-specific partner inventory incomplete\", \"Direct disease-causing mutations not defined in primary data\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [0, 4, 6]},\n      {\"term_id\": \"GO:0008289\", \"supporting_discovery_ids\": [3, 5]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [0, 4]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [1, 4]},\n      {\"term_id\": \"GO:0005768\", \"supporting_discovery_ids\": [6]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-9609507\", \"supporting_discovery_ids\": [1, 6]},\n      {\"term_id\": \"R-HSA-1640170\", \"supporting_discovery_ids\": [6]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [3]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"TRPV4\", \"ADAM12\", \"GLUT1\", \"Piezo1\", \"FasL\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":5,"faith_total":5,"faith_pct":100.0}}