{"gene":"SYNPO","run_date":"2026-06-10T10:51:54","timeline":{"discoveries":[{"year":2005,"finding":"Synaptopodin exists in three isoforms (Synpo-short, Synpo-long, Synpo-T); all three specifically interact with alpha-actinin and elongate alpha-actinin-induced actin filaments, thereby regulating the actin-bundling activity of alpha-actinin in podocyte foot processes and dendritic spines.","method":"Isoform characterization, co-immunoprecipitation, in vitro actin filament assays, gene silencing in podocytes, synpo-/- mouse model","journal":"The Journal of clinical investigation","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (KO mouse, in vitro actin assays, gene silencing with specific phenotypic rescue), replicated across tissue types","pmids":["15841212"],"is_preprint":false},{"year":2005,"finding":"Synaptopodin associates with both F-actin (via a central SYNPO motif) and alpha-actinin (via the C-terminal domain); the alpha-actinin-binding C-terminal domain is essential for dendritic targeting and postsynaptic accumulation of SYNPO in primary neurons.","method":"Yeast two-hybrid, biochemical co-sedimentation assays, ectopic expression in neuronal and non-neuronal cells, domain-deletion analysis in primary neurons","journal":"Journal of neurochemistry","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — yeast two-hybrid plus biochemical assays plus domain mapping with functional localization readout, single lab but multiple orthogonal methods","pmids":["15659229"],"is_preprint":false},{"year":2006,"finding":"CD2AP physically associates with both Fyn and Synaptopodin (but not Neph1) in podocytes; bigenic heterozygosity of Cd2ap with Synpo (or Fyn) results in spontaneous proteinuria and FSGS-like glomerular damage, demonstrating genetic and functional interaction.","method":"Co-immunoprecipitation, bigenic heterozygous mouse models, proteinuria assays, histopathology","journal":"The Journal of clinical investigation","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP plus epistasis in vivo with defined phenotypic readout; replicated across two genetic combinations","pmids":["16628251"],"is_preprint":false},{"year":2008,"finding":"SYNPO stabilizes activity-dependent increases in dendritic spine volume; overexpression of SYNPO in primary hippocampal neurons caused persistent spine enlargement after NMDA receptor activation, and SYNPO protected F-actin stress fibers from staurosporine-induced disruption in non-neuronal cells.","method":"Overexpression in primary hippocampal cultures, pharmacological NMDA receptor activation, live imaging of spine volume, F-actin protection assay in PtK2 cells","journal":"Molecular and cellular neurosciences","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — overexpression with direct morphological and biochemical readouts, single lab, two orthogonal assays","pmids":["18424168"],"is_preprint":false},{"year":2010,"finding":"Synaptopodin reciprocally co-immunoprecipitates with BKCa (Slo1) channels in mouse glomeruli, podocytes, and HEK293T cells; Synpo interacts with BKCa at C-terminal domains overlapping the actin-binding domain; Synpo coexpression increases steady-state surface expression of BKCa channels (effect on forward trafficking rate), and this effect is blocked by Rho inhibition; sustained actin depolymerization also reduces functional surface BKCa.","method":"Reciprocal co-immunoprecipitation, heterologous expression in HEK293T, stable Synpo knockdown in podocyte cell lines, surface biotinylation, electrophysiology","journal":"American journal of physiology. Renal physiology","confidence":"High","confidence_rationale":"Tier 2 / Moderate — reciprocal Co-IP, stable KD, heterologous expression, and functional channel assays; single lab but multiple orthogonal methods","pmids":["20630939"],"is_preprint":false},{"year":2011,"finding":"In the axon initial segment (AIS), synaptopodin-positive elements associated with the cisternal organelle are present from day 6 in vitro; synpo expression in the AIS is independent of neuronal activity and resistant to detergent extraction, indicating association with scaffolding/cytoskeleton proteins; presence of ankyrin G is required for acquisition and maintenance of the cisternal organelle.","method":"In vitro maturation of hippocampal neurons, immunofluorescence, TTX blockade, detergent extraction, ankyrin G perturbation","journal":"Molecular and cellular neurosciences","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — direct localization experiments with functional perturbations (activity blockade, detergent resistance, ankyrin G dependency); single lab","pmids":["21708259"],"is_preprint":false},{"year":2014,"finding":"STAT3 signaling maintains steady-state SYNPO protein levels in podocytes; inhibition of STAT3 (by Stattic or siRNA knockdown) rapidly decreases Synpo mRNA and protein via cathepsin L-dependent proteolysis; IL-6-driven STAT3 activation increases Synpo; angiotensin II reduces STAT3 signaling and concurrently reduces Synpo protein, prevented by cathepsin L inhibition but not calcineurin blockade.","method":"Small-molecule inhibitor (Stattic), siRNA knockdown, protease inhibitor (E-64), cytokine treatment (IL-6, Ang II), immunoblot, wound migration assay in podocyte cell line","journal":"Molecular pharmacology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple pharmacological and genetic perturbations with defined mechanistic readouts; single lab","pmids":["25425624"],"is_preprint":false},{"year":2017,"finding":"SYNPO is induced transcriptionally and epigenetically by IL-13 in esophageal epithelial cells; SYNPO colocalizes with actin filaments in the basal epithelial layer; SYNPO gene silencing reduces epithelial motility in wound healing, whereas SYNPO overexpression impairs epithelial barrier integrity and reduces esophageal differentiation.","method":"siRNA knockdown, SYNPO overexpression, wound-healing assay, barrier integrity assay, IL-13 treatment, biopsy immunostaining, histone modification analysis","journal":"JCI insight","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal gain- and loss-of-function with specific cellular phenotypic readouts; single lab","pmids":["29046486"],"is_preprint":false},{"year":2019,"finding":"BAG3 facilitates autophagic flux in post-synaptic neurites through physical interaction with SYNPO; loss of either BAG3 or SYNPO impedes autophagosome-lysosome fusion predominantly in the post-synaptic compartment, leading to accumulation of SQSTM1/p62 and phospho-MAPT (Ser262) in autophagosomes at post-synaptic densities.","method":"shRNA knockdown of BAG3 and SYNPO in mature cultured neurons, autophagy flux assays (LC3, SQSTM1, cathepsin L), immunofluorescence co-localization, pharmacological autophagy blockade (bafilomycin, chloroquine)","journal":"Autophagy","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — dual loss-of-function with specific organelle-level and substrate readouts; single lab","pmids":["30744518"],"is_preprint":false},{"year":2019,"finding":"The WW2 domain of KIBRA remains largely disordered when bound to a two-PPXY motif polypeptide of SYNPO; SYNPO binds the tandem WW1-WW2 domain in an antiparallel manner (WW1 domain binds the second PPXY motif of SYNPO); the interaction of disordered WW2 with SYNPO is significantly weaker than SYNPO's interactions with the well-folded WW1 domain.","method":"Isothermal titration calorimetry, circular dichroism, solution NMR chemical shift perturbation analysis, site-directed mutagenesis (I81W)","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — biophysical reconstitution with ITC, CD, and NMR plus mutagenesis; single lab but multiple orthogonal structural/biophysical methods","pmids":["31597702"],"is_preprint":false},{"year":2020,"finding":"Loss of SYNPO in podocytes causes loss of stress fibers, increased number and size of focal adhesions, impaired cell migration, decreased RhoA activity, and increased Rac1 activation; SYNPO-null mice do not develop spontaneous kidney disease but are more susceptible to adriamycin nephropathy.","method":"CRISPR/Cas9 complete gene deletion mouse model, primary cultured podocytes, GTPase activity assays (RhoA, Rac1), adriamycin nephropathy challenge, immunofluorescence, migration assays","journal":"Journal of the American Society of Nephrology : JASN","confidence":"High","confidence_rationale":"Tier 2 / Strong — complete KO with multiple orthogonal mechanistic readouts (GTPase activity, actin morphology, migration, in vivo challenge), single lab rigorous study","pmids":["32938649"],"is_preprint":false},{"year":2020,"finding":"Microbiota-derived butyrate selectively induces SYNPO expression in intestinal epithelial cells via histone deacetylase inhibition; SYNPO localizes to tight junctions and F-actin stress fibers; depletion of SYNPO impairs epithelial barrier function and wound healing; microbiota depletion abrogates colonic SYNPO expression rescued by butyrate repletion; Synpo-deficient mice show exacerbated DSS colitis and increased intestinal permeability.","method":"SYNPO knockdown, butyrate treatment, HDAC inhibitor studies, wound healing assay, barrier integrity assay (TEER), Synpo KO mouse DSS colitis model, immunofluorescence localization, enteroid cultures","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal in vitro and in vivo methods with mechanistic (HDAC) and pathway (tight junction localization) evidence; single lab rigorous study","pmids":["32398370"],"is_preprint":false},{"year":2020,"finding":"Loss-of-function mutations in SYNPO lead to decreased CDC42 activity and reduced podocyte migration rate, both rescued by overexpression of wild-type SYNPO cDNA but not by cDNA representing the patient mutation, identifying SYNPO as a candidate monogenic cause of nephrotic syndrome.","method":"Whole-exome sequencing, podocyte migration assay, CDC42 GTPase activity assay, rescue by wild-type vs. mutant cDNA overexpression","journal":"Kidney international reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional rescue experiment with mutant vs. WT cDNA and GTPase activity measurement; single lab","pmids":["33615071"],"is_preprint":false},{"year":2021,"finding":"Absence of SYNPO in Alport syndrome mice (Col4a5 mutants) accelerates disease progression with more severe proteinuria and glomerulosclerosis; loss of Synpo attenuates the shift of myosin IIA from the podocyte cell body to actin cables near the glomerular basement membrane in areas of foot process effacement.","method":"Double-mutant mouse generation (Synpo × Col4a5), albuminuria measurements, electron microscopy, immunofluorescence for myosin IIA localization","journal":"American journal of physiology. Renal physiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic epistasis in vivo with defined molecular readout (myosin IIA localization); single lab","pmids":["34029143"],"is_preprint":false},{"year":2023,"finding":"KLHL17 modulates the synaptic distribution of SYNPO; SYNPO is embedded in the ER network of dendritic spines (spine apparatus); KLHL17 and SYNPO act in concert such that disruption of the KLHL17–SYNPO association or Klhl17 KO reduces the proportion of dendritic spines containing ER clusters, impairs activity-dependent spine enlargement, alters calcium events at spines, and reduces ERK phosphorylation and c-Fos expression.","method":"Mouse genetic models (Klhl17 haploinsufficiency and KO), super-resolution expansion microscopy, calcium imaging at dendritic spines, ERK phosphorylation assays, c-Fos immunostaining, co-IP to assess KLHL17–SYNPO interaction","journal":"PLoS biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic KO plus haploinsufficiency, super-resolution imaging, calcium imaging, and biochemical readouts in single study with mechanistic rescue experiment","pmids":["37651441"],"is_preprint":false},{"year":2014,"finding":"Laminar shear stress upregulates SYNPO expression in human umbilical vein endothelial cells; siRNA-mediated suppression of SYNPO attenuates wound closure under LSS, while overexpression of SYNPO enhances endothelial wound closure, establishing SYNPO as a key mediator of endothelial wound healing.","method":"Laminar shear stress exposure, mRNA profiling, siRNA knockdown, SYNPO overexpression, endothelial wound healing assay","journal":"FEBS letters","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal gain- and loss-of-function with defined wound-healing phenotype; single lab","pmids":["24561195"],"is_preprint":false},{"year":2025,"finding":"MAGI-2 forms a protein complex with Synaptopodin and α-actinin-4 in podocytes; loss of MAGI-2 in podocytes causes actin bundles to shift toward the basement membrane; co-expression of MAGI-2 with these partners relocates the actin cytoskeleton toward cell-cell contacts.","method":"Podocyte-specific MAGI-2 knockout mice, co-immunoprecipitation to map binding domains, co-expression in cultured podocytes, immunofluorescence for actin localization","journal":"Kidney360","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP with domain mapping plus KO mouse with specific actin localization readout; single lab","pmids":["41182836"],"is_preprint":false},{"year":2026,"finding":"Synaptopodin maintains cerebrovascular homeostasis by positively regulating cdh2 (N-cadherin); synpo mutant zebrafish show elevated cerebrovascular leakage after epinephrine challenge and higher incidence of intracerebral hemorrhage; cdh2 mRNA supplementation rescues the cerebrovascular leakage in synpo mutants.","method":"CRISPR/Cas9 synpo mutant zebrafish, epinephrine challenge assay, transcriptomic profiling of mutant brains, mRNA rescue experiment for cdh2","journal":"Yi chuan = Hereditas","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic KO with in vivo phenotype and specific mRNA rescue identifying downstream effector; single lab, zebrafish model","pmids":["41992887"],"is_preprint":false},{"year":2026,"finding":"In striated and smooth muscle cells, SYNPO localizes to myofibrillar Z-discs, intercalated discs, and partially colocalizes with sarcoplasmic reticulum-associated STIM1; SYNPO binds filamin C (FLNc) via a small region homologous to the FLNc-binding region of SYNPO2, in addition to its known interactions with actin and α-actinin.","method":"Isoform characterization at RNA and protein levels, immunostaining of tissue sections, co-immunoprecipitation/protein interaction studies, transfection of SYNPO isoforms in skeletal myotubes and smooth muscle cells","journal":"Experimental cell research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct localization experiments plus Co-IP identifying new binding partner (FLNc); single lab, multiple muscle cell types","pmids":["41941933"],"is_preprint":false},{"year":2025,"finding":"Synpo KO rats generated by CRISPR-Cas9 lack the Synpo-dependent dendritic spine apparatus and cisternal organelles in the axon initial segment (AIS); inhibitory synapses in the wild-type AIS cluster preferentially near cisternal organelles, a pattern disrupted in KO rats where synapses are more uniformly distributed; LTP is reduced in KO rats.","method":"CRISPR-Cas9 KO rat, 3D electron microscopy reconstruction of dendritic spines and AIS, LTP electrophysiology, synaptic quantification","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic KO with ultrastructural 3D EM and electrophysiology; preprint, single lab","pmids":["41394584"],"is_preprint":true}],"current_model":"Synaptopodin (SYNPO) is a proline-rich actin-associated scaffolding protein that binds F-actin (via a central domain) and alpha-actinin (via its C-terminus) to elongate and stabilize actin filaments in highly dynamic compartments including podocyte foot processes, dendritic spines, and the axon initial segment cisternal organelle; it regulates RhoA/Rac1/CDC42 GTPase balance to control actin dynamics, promotes forward trafficking of BKCa channels to the cell surface in a Rho-dependent manner, cooperates with BAG3 to facilitate autophagosome-lysosome fusion and clearance of phospho-tau at post-synaptic densities, acts with KLHL17 to maintain the spine apparatus ER network for activity-dependent spine enlargement and calcium signaling, interacts with MAGI-2 and alpha-actinin-4 to position actin bundles within podocyte foot processes, binds the KIBRA WW1 domain via PPXY motifs, and in endothelial and epithelial cells promotes wound healing and barrier integrity downstream of laminar shear stress and butyrate/IL-13 signaling respectively."},"narrative":{"mechanistic_narrative":"Synaptopodin (SYNPO) is an actin-associated scaffolding protein that organizes and stabilizes dynamic actin-based compartments in podocytes, neurons, and epithelial/endothelial cells [PMID:15841212, PMID:32938649]. It binds F-actin through a central motif and alpha-actinin through its C-terminal domain, elongating alpha-actinin-induced actin filaments and protecting stress fibers from disruption; the alpha-actinin-binding C-terminus is required for dendritic targeting and postsynaptic accumulation [PMID:15841212, PMID:15659229, PMID:18424168]. In podocytes SYNPO governs actin architecture by shifting the balance of small GTPases—its loss reduces RhoA and CDC42 activity while increasing Rac1, collapsing stress fibers, expanding focal adhesions, and impairing migration [PMID:32938649, PMID:33615071]. It assembles into adhesion and junction complexes with CD2AP, MAGI-2, and alpha-actinin-4 to position actin bundles within foot processes, and SYNPO loss sensitizes the glomerulus to injury in adriamycin and Alport models [PMID:16628251, PMID:41182836, PMID:34029143]; loss-of-function mutations that fail to rescue CDC42 activity and migration implicate SYNPO as a candidate monogenic cause of nephrotic syndrome [PMID:33615071]. In neurons SYNPO is a component of the spine apparatus ER and the axon initial segment cisternal organelle, where it acts with KLHL17 to maintain spine ER clusters that support activity-dependent spine enlargement, calcium signaling, and downstream ERK/c-Fos activation [PMID:37651441, PMID:21708259], and it cooperates with BAG3 to enable post-synaptic autophagosome–lysosome fusion and clearance of p62 and phospho-tau [PMID:30744518]. Beyond the cytoskeleton, SYNPO promotes forward trafficking of BKCa channels to the cell surface in a Rho-dependent manner [PMID:20630939], and its expression is induced by butyrate, IL-13, and laminar shear stress to drive epithelial and endothelial wound healing and barrier integrity [PMID:32398370, PMID:29046486, PMID:24561195]; STAT3 signaling sustains SYNPO protein levels against cathepsin L-dependent proteolysis [PMID:25425624].","teleology":[{"year":2005,"claim":"Established the core biochemical activity of SYNPO: how a proline-rich protein controls actin architecture, by showing it binds alpha-actinin and elongates alpha-actinin-induced actin filaments across podocytes and neurons.","evidence":"Isoform characterization, co-IP, in vitro actin filament assays, and synpo-/- mouse","pmids":["15841212","15659229"],"confidence":"High","gaps":["Did not resolve how the central F-actin motif and C-terminal alpha-actinin site coordinate filament bundling quantitatively","Mechanism linking actin elongation to spine/foot process morphology not yet defined"]},{"year":2006,"claim":"Placed SYNPO in a podocyte adhesion network by demonstrating genetic and physical interaction with CD2AP, showing that combined SYNPO/CD2AP dosage loss causes glomerular disease.","evidence":"Co-IP and bigenic heterozygous mouse models with proteinuria/histopathology readouts","pmids":["16628251"],"confidence":"High","gaps":["Direct molecular contact between SYNPO and CD2AP versus indirect bridging not distinguished","Role of Fyn phosphorylation of SYNPO not addressed"]},{"year":2008,"claim":"Connected SYNPO's actin-stabilizing activity to a functional neuronal output by showing it stabilizes activity-dependent spine enlargement and protects stress fibers.","evidence":"Overexpression in hippocampal neurons with NMDA activation, live spine imaging, and F-actin protection assay","pmids":["18424168"],"confidence":"Medium","gaps":["Based on overexpression rather than endogenous loss-of-function","Did not identify the molecular intermediary linking SYNPO to spine volume persistence"]},{"year":2011,"claim":"Defined the structural context of SYNPO in the axon initial segment, showing its cisternal-organelle association is activity-independent and requires ankyrin G.","evidence":"In vitro neuronal maturation, immunofluorescence, TTX blockade, detergent extraction, and ankyrin G perturbation","pmids":["21708259"],"confidence":"Medium","gaps":["Direct binding partners anchoring SYNPO at the AIS not identified","Functional consequence of the cisternal organelle left open"]},{"year":2014,"claim":"Identified upstream control of SYNPO abundance, showing STAT3 signaling protects SYNPO from cathepsin L proteolysis, and an independent role for SYNPO in endothelial wound healing under shear stress.","evidence":"STAT3 inhibition/knockdown, cytokine and protease-inhibitor treatments, immunoblot; separately laminar shear stress with siRNA/overexpression and wound assays in HUVECs","pmids":["25425624","24561195"],"confidence":"Medium","gaps":["Direct STAT3 transcriptional targeting of SYNPO versus indirect stabilization not separated","Mechanism by which SYNPO drives endothelial migration unresolved"]},{"year":2010,"claim":"Extended SYNPO function beyond cytoskeletal scaffolding to membrane channel trafficking, showing it promotes Rho-dependent surface delivery of BKCa channels.","evidence":"Reciprocal co-IP, heterologous expression, stable knockdown, surface biotinylation, and electrophysiology","pmids":["20630939"],"confidence":"High","gaps":["Whether SYNPO directly chaperones channels or acts indirectly via actin/Rho not resolved","Physiological relevance of BKCa trafficking in intact podocytes not tested"]},{"year":2017,"claim":"Demonstrated cytokine-driven epithelial regulation, with IL-13 inducing SYNPO transcriptionally/epigenetically to control esophageal epithelial motility and barrier/differentiation balance.","evidence":"siRNA, overexpression, wound-healing and barrier assays, IL-13 treatment, and histone modification analysis","pmids":["29046486"],"confidence":"Medium","gaps":["Transcription factors mediating IL-13 induction not identified","Mechanism by which excess SYNPO impairs barrier integrity unclear"]},{"year":2019,"claim":"Resolved two distinct postsynaptic mechanisms: SYNPO partners with BAG3 to drive autophagosome-lysosome fusion clearing phospho-tau, and biophysically defined the SYNPO-KIBRA WW-domain interaction.","evidence":"Dual shRNA knockdown with autophagy flux/substrate readouts; separately ITC, CD, and NMR with mutagenesis on KIBRA WW domains","pmids":["30744518","31597702"],"confidence":"High","gaps":["How SYNPO mechanistically promotes autophagosome-lysosome fusion not defined","Functional consequence of the KIBRA-SYNPO PPXY interaction in cells not established"]},{"year":2020,"claim":"Defined SYNPO as a master regulator of the podocyte GTPase balance and a candidate disease gene, with KO shifting RhoA/Rac1/CDC42 activity and patient mutations failing to rescue CDC42 and migration.","evidence":"CRISPR KO mouse and primary podocytes with GTPase assays, migration assays, adriamycin challenge; whole-exome sequencing with WT-versus-mutant cDNA rescue","pmids":["32938649","33615071"],"confidence":"High","gaps":["How SYNPO couples to GTPase regulators (GEFs/GAPs) not identified","Absence of spontaneous KO phenotype indicates redundancy that is unexplained"]},{"year":2020,"claim":"Established a microbiota-host axis whereby butyrate induces SYNPO via HDAC inhibition to maintain intestinal tight junctions and barrier integrity.","evidence":"Knockdown, butyrate/HDAC-inhibitor studies, TEER and wound assays, enteroids, and Synpo KO mouse DSS colitis","pmids":["32398370"],"confidence":"High","gaps":["Direct HDAC target locus driving SYNPO induction not mapped","Molecular link between SYNPO and tight-junction assembly unresolved"]},{"year":2021,"claim":"Showed SYNPO modulates injury responses by regulating myosin IIA redistribution, with its loss accelerating Alport glomerular disease.","evidence":"Synpo x Col4a5 double-mutant mice with albuminuria, EM, and myosin IIA immunofluorescence","pmids":["34029143"],"confidence":"Medium","gaps":["Direct interaction of SYNPO with myosin IIA versus indirect effect not distinguished","Mechanism of foot process effacement contribution incomplete"]},{"year":2023,"claim":"Defined the spine apparatus ER mechanism, showing KLHL17 acts with SYNPO to maintain spine ER clusters required for activity-dependent enlargement, calcium signaling, and ERK/c-Fos activation.","evidence":"Klhl17 KO and haploinsufficient mice, expansion microscopy, calcium imaging, ERK/c-Fos assays, and co-IP","pmids":["37651441"],"confidence":"High","gaps":["Whether KLHL17 acts as a Cullin3 adaptor toward SYNPO not tested","How spine ER clustering mechanistically gates calcium events unresolved"]},{"year":2025,"claim":"Mapped additional structural and tissue-specific partners, placing SYNPO in a podocyte MAGI-2/alpha-actinin-4 complex and in muscle Z-discs binding filamin C.","evidence":"Podocyte MAGI-2 KO mice with co-IP and actin localization; isoform/localization characterization and co-IP for FLNc in muscle cells","pmids":["41182836","41941933"],"confidence":"Medium","gaps":["Functional consequence of the SYNPO-FLNc interaction in muscle physiology not tested","Hierarchy of SYNPO binding among actin, alpha-actinin, MAGI-2, and FLNc unresolved"]},{"year":2026,"claim":"Extended SYNPO function to cerebrovascular integrity, identifying N-cadherin (cdh2) as a downstream effector whose supplementation rescues vascular leakage in synpo mutants.","evidence":"CRISPR synpo mutant zebrafish, epinephrine challenge, transcriptomics, and cdh2 mRNA rescue","pmids":["41992887"],"confidence":"Medium","gaps":["How SYNPO transcriptionally or post-transcriptionally regulates cdh2 not defined","Cell type mediating the cerebrovascular phenotype not pinpointed"]},{"year":null,"claim":"How SYNPO mechanistically couples actin scaffolding to the small-GTPase switches (RhoA/Rac1/CDC42) and to ER/organelle positioning across its diverse tissue contexts remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No GEF/GAP intermediary linking SYNPO to GTPase regulation identified","No structural model of full-length SYNPO with actin and alpha-actinin","Unifying mechanism across podocyte, neuronal, and epithelial roles not established"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0008092","term_label":"cytoskeletal protein binding","supporting_discovery_ids":[0,1,3,10,18]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[0,2,16,14,9]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[10,12]}],"localization":[{"term_id":"GO:0005856","term_label":"cytoskeleton","supporting_discovery_ids":[0,1,7,11,18]},{"term_id":"GO:0005783","term_label":"endoplasmic reticulum","supporting_discovery_ids":[14,19]},{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[4,11]}],"pathway":[{"term_id":"R-HSA-9612973","term_label":"Autophagy","supporting_discovery_ids":[8]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[10,12,4]},{"term_id":"R-HSA-112316","term_label":"Neuronal System","supporting_discovery_ids":[14,19]}],"complexes":["spine apparatus","axon initial segment cisternal organelle","podocyte MAGI-2/alpha-actinin-4 complex"],"partners":["ACTN4","CD2AP","KCNMA1","BAG3","WWC1","KLHL17","MAGI2","FLNC"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q8N3V7","full_name":"Synaptopodin","aliases":[],"length_aa":929,"mass_kda":99.5,"function":"Actin-associated protein that may play a role in modulating actin-based shape and motility of dendritic spines and renal podocyte foot processes. Seems to be essential for the formation of spine apparatuses in spines of telencephalic neurons, which is involved in synaptic plasticity (By similarity)","subcellular_location":"Cytoplasm, cytoskeleton; Cell junction, tight junction; Perikaryon; Cell projection, dendritic spine; Postsynaptic density; Synapse; Cytoplasm, cytosol","url":"https://www.uniprot.org/uniprotkb/Q8N3V7/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/SYNPO","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":[],"url":"https://opencell.sf.czbiohub.org/search/SYNPO","total_profiled":1310},"omim":[{"mim_id":"621429","title":"SYNAPTOPODIN 2-LIKE PROTEIN; SYNPO2L","url":"https://www.omim.org/entry/621429"},{"mim_id":"616032","title":"FOCAL SEGMENTAL GLOMERULOSCLEROSIS 8; FSGS8","url":"https://www.omim.org/entry/616032"},{"mim_id":"616027","title":"ACTIN-BINDING PROTEIN ANILLIN; ANLN","url":"https://www.omim.org/entry/616027"},{"mim_id":"614612","title":"KN MOTIF- AND ANKYRIN REPEAT DOMAIN-CONTAINING PROTEIN 4; KANK4","url":"https://www.omim.org/entry/614612"},{"mim_id":"614610","title":"KN MOTIF- AND ANKYRIN REPEAT DOMAIN-CONTAINING PROTEIN 2; KANK2","url":"https://www.omim.org/entry/614610"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Plasma membrane","reliability":"Approved"},{"location":"Cytosol","reliability":"Approved"},{"location":"Actin filaments","reliability":"Additional"}],"tissue_specificity":"Group enriched","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"blood vessel","ntpm":357.2},{"tissue":"heart muscle","ntpm":344.8},{"tissue":"skeletal 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characterization, co-immunoprecipitation, in vitro actin filament assays, gene silencing in podocytes, synpo-/- mouse model\",\n      \"journal\": \"The Journal of clinical investigation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (KO mouse, in vitro actin assays, gene silencing with specific phenotypic rescue), replicated across tissue types\",\n      \"pmids\": [\"15841212\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Synaptopodin associates with both F-actin (via a central SYNPO motif) and alpha-actinin (via the C-terminal domain); the alpha-actinin-binding C-terminal domain is essential for dendritic targeting and postsynaptic accumulation of SYNPO in primary neurons.\",\n      \"method\": \"Yeast two-hybrid, biochemical co-sedimentation assays, ectopic expression in neuronal and non-neuronal cells, domain-deletion analysis in primary neurons\",\n      \"journal\": \"Journal of neurochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — yeast two-hybrid plus biochemical assays plus domain mapping with functional localization readout, single lab but multiple orthogonal methods\",\n      \"pmids\": [\"15659229\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"CD2AP physically associates with both Fyn and Synaptopodin (but not Neph1) in podocytes; bigenic heterozygosity of Cd2ap with Synpo (or Fyn) results in spontaneous proteinuria and FSGS-like glomerular damage, demonstrating genetic and functional interaction.\",\n      \"method\": \"Co-immunoprecipitation, bigenic heterozygous mouse models, proteinuria assays, histopathology\",\n      \"journal\": \"The Journal of clinical investigation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP plus epistasis in vivo with defined phenotypic readout; replicated across two genetic combinations\",\n      \"pmids\": [\"16628251\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"SYNPO stabilizes activity-dependent increases in dendritic spine volume; overexpression of SYNPO in primary hippocampal neurons caused persistent spine enlargement after NMDA receptor activation, and SYNPO protected F-actin stress fibers from staurosporine-induced disruption in non-neuronal cells.\",\n      \"method\": \"Overexpression in primary hippocampal cultures, pharmacological NMDA receptor activation, live imaging of spine volume, F-actin protection assay in PtK2 cells\",\n      \"journal\": \"Molecular and cellular neurosciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — overexpression with direct morphological and biochemical readouts, single lab, two orthogonal assays\",\n      \"pmids\": [\"18424168\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Synaptopodin reciprocally co-immunoprecipitates with BKCa (Slo1) channels in mouse glomeruli, podocytes, and HEK293T cells; Synpo interacts with BKCa at C-terminal domains overlapping the actin-binding domain; Synpo coexpression increases steady-state surface expression of BKCa channels (effect on forward trafficking rate), and this effect is blocked by Rho inhibition; sustained actin depolymerization also reduces functional surface BKCa.\",\n      \"method\": \"Reciprocal co-immunoprecipitation, heterologous expression in HEK293T, stable Synpo knockdown in podocyte cell lines, surface biotinylation, electrophysiology\",\n      \"journal\": \"American journal of physiology. Renal physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal Co-IP, stable KD, heterologous expression, and functional channel assays; single lab but multiple orthogonal methods\",\n      \"pmids\": [\"20630939\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"In the axon initial segment (AIS), synaptopodin-positive elements associated with the cisternal organelle are present from day 6 in vitro; synpo expression in the AIS is independent of neuronal activity and resistant to detergent extraction, indicating association with scaffolding/cytoskeleton proteins; presence of ankyrin G is required for acquisition and maintenance of the cisternal organelle.\",\n      \"method\": \"In vitro maturation of hippocampal neurons, immunofluorescence, TTX blockade, detergent extraction, ankyrin G perturbation\",\n      \"journal\": \"Molecular and cellular neurosciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — direct localization experiments with functional perturbations (activity blockade, detergent resistance, ankyrin G dependency); single lab\",\n      \"pmids\": [\"21708259\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"STAT3 signaling maintains steady-state SYNPO protein levels in podocytes; inhibition of STAT3 (by Stattic or siRNA knockdown) rapidly decreases Synpo mRNA and protein via cathepsin L-dependent proteolysis; IL-6-driven STAT3 activation increases Synpo; angiotensin II reduces STAT3 signaling and concurrently reduces Synpo protein, prevented by cathepsin L inhibition but not calcineurin blockade.\",\n      \"method\": \"Small-molecule inhibitor (Stattic), siRNA knockdown, protease inhibitor (E-64), cytokine treatment (IL-6, Ang II), immunoblot, wound migration assay in podocyte cell line\",\n      \"journal\": \"Molecular pharmacology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple pharmacological and genetic perturbations with defined mechanistic readouts; single lab\",\n      \"pmids\": [\"25425624\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"SYNPO is induced transcriptionally and epigenetically by IL-13 in esophageal epithelial cells; SYNPO colocalizes with actin filaments in the basal epithelial layer; SYNPO gene silencing reduces epithelial motility in wound healing, whereas SYNPO overexpression impairs epithelial barrier integrity and reduces esophageal differentiation.\",\n      \"method\": \"siRNA knockdown, SYNPO overexpression, wound-healing assay, barrier integrity assay, IL-13 treatment, biopsy immunostaining, histone modification analysis\",\n      \"journal\": \"JCI insight\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal gain- and loss-of-function with specific cellular phenotypic readouts; single lab\",\n      \"pmids\": [\"29046486\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"BAG3 facilitates autophagic flux in post-synaptic neurites through physical interaction with SYNPO; loss of either BAG3 or SYNPO impedes autophagosome-lysosome fusion predominantly in the post-synaptic compartment, leading to accumulation of SQSTM1/p62 and phospho-MAPT (Ser262) in autophagosomes at post-synaptic densities.\",\n      \"method\": \"shRNA knockdown of BAG3 and SYNPO in mature cultured neurons, autophagy flux assays (LC3, SQSTM1, cathepsin L), immunofluorescence co-localization, pharmacological autophagy blockade (bafilomycin, chloroquine)\",\n      \"journal\": \"Autophagy\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — dual loss-of-function with specific organelle-level and substrate readouts; single lab\",\n      \"pmids\": [\"30744518\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"The WW2 domain of KIBRA remains largely disordered when bound to a two-PPXY motif polypeptide of SYNPO; SYNPO binds the tandem WW1-WW2 domain in an antiparallel manner (WW1 domain binds the second PPXY motif of SYNPO); the interaction of disordered WW2 with SYNPO is significantly weaker than SYNPO's interactions with the well-folded WW1 domain.\",\n      \"method\": \"Isothermal titration calorimetry, circular dichroism, solution NMR chemical shift perturbation analysis, site-directed mutagenesis (I81W)\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — biophysical reconstitution with ITC, CD, and NMR plus mutagenesis; single lab but multiple orthogonal structural/biophysical methods\",\n      \"pmids\": [\"31597702\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Loss of SYNPO in podocytes causes loss of stress fibers, increased number and size of focal adhesions, impaired cell migration, decreased RhoA activity, and increased Rac1 activation; SYNPO-null mice do not develop spontaneous kidney disease but are more susceptible to adriamycin nephropathy.\",\n      \"method\": \"CRISPR/Cas9 complete gene deletion mouse model, primary cultured podocytes, GTPase activity assays (RhoA, Rac1), adriamycin nephropathy challenge, immunofluorescence, migration assays\",\n      \"journal\": \"Journal of the American Society of Nephrology : JASN\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — complete KO with multiple orthogonal mechanistic readouts (GTPase activity, actin morphology, migration, in vivo challenge), single lab rigorous study\",\n      \"pmids\": [\"32938649\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Microbiota-derived butyrate selectively induces SYNPO expression in intestinal epithelial cells via histone deacetylase inhibition; SYNPO localizes to tight junctions and F-actin stress fibers; depletion of SYNPO impairs epithelial barrier function and wound healing; microbiota depletion abrogates colonic SYNPO expression rescued by butyrate repletion; Synpo-deficient mice show exacerbated DSS colitis and increased intestinal permeability.\",\n      \"method\": \"SYNPO knockdown, butyrate treatment, HDAC inhibitor studies, wound healing assay, barrier integrity assay (TEER), Synpo KO mouse DSS colitis model, immunofluorescence localization, enteroid cultures\",\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 in vitro and in vivo methods with mechanistic (HDAC) and pathway (tight junction localization) evidence; single lab rigorous study\",\n      \"pmids\": [\"32398370\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Loss-of-function mutations in SYNPO lead to decreased CDC42 activity and reduced podocyte migration rate, both rescued by overexpression of wild-type SYNPO cDNA but not by cDNA representing the patient mutation, identifying SYNPO as a candidate monogenic cause of nephrotic syndrome.\",\n      \"method\": \"Whole-exome sequencing, podocyte migration assay, CDC42 GTPase activity assay, rescue by wild-type vs. mutant cDNA overexpression\",\n      \"journal\": \"Kidney international reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional rescue experiment with mutant vs. WT cDNA and GTPase activity measurement; single lab\",\n      \"pmids\": [\"33615071\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Absence of SYNPO in Alport syndrome mice (Col4a5 mutants) accelerates disease progression with more severe proteinuria and glomerulosclerosis; loss of Synpo attenuates the shift of myosin IIA from the podocyte cell body to actin cables near the glomerular basement membrane in areas of foot process effacement.\",\n      \"method\": \"Double-mutant mouse generation (Synpo × Col4a5), albuminuria measurements, electron microscopy, immunofluorescence for myosin IIA localization\",\n      \"journal\": \"American journal of physiology. Renal physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic epistasis in vivo with defined molecular readout (myosin IIA localization); single lab\",\n      \"pmids\": [\"34029143\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"KLHL17 modulates the synaptic distribution of SYNPO; SYNPO is embedded in the ER network of dendritic spines (spine apparatus); KLHL17 and SYNPO act in concert such that disruption of the KLHL17–SYNPO association or Klhl17 KO reduces the proportion of dendritic spines containing ER clusters, impairs activity-dependent spine enlargement, alters calcium events at spines, and reduces ERK phosphorylation and c-Fos expression.\",\n      \"method\": \"Mouse genetic models (Klhl17 haploinsufficiency and KO), super-resolution expansion microscopy, calcium imaging at dendritic spines, ERK phosphorylation assays, c-Fos immunostaining, co-IP to assess KLHL17–SYNPO interaction\",\n      \"journal\": \"PLoS biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic KO plus haploinsufficiency, super-resolution imaging, calcium imaging, and biochemical readouts in single study with mechanistic rescue experiment\",\n      \"pmids\": [\"37651441\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Laminar shear stress upregulates SYNPO expression in human umbilical vein endothelial cells; siRNA-mediated suppression of SYNPO attenuates wound closure under LSS, while overexpression of SYNPO enhances endothelial wound closure, establishing SYNPO as a key mediator of endothelial wound healing.\",\n      \"method\": \"Laminar shear stress exposure, mRNA profiling, siRNA knockdown, SYNPO overexpression, endothelial wound healing assay\",\n      \"journal\": \"FEBS letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal gain- and loss-of-function with defined wound-healing phenotype; single lab\",\n      \"pmids\": [\"24561195\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"MAGI-2 forms a protein complex with Synaptopodin and α-actinin-4 in podocytes; loss of MAGI-2 in podocytes causes actin bundles to shift toward the basement membrane; co-expression of MAGI-2 with these partners relocates the actin cytoskeleton toward cell-cell contacts.\",\n      \"method\": \"Podocyte-specific MAGI-2 knockout mice, co-immunoprecipitation to map binding domains, co-expression in cultured podocytes, immunofluorescence for actin localization\",\n      \"journal\": \"Kidney360\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP with domain mapping plus KO mouse with specific actin localization readout; single lab\",\n      \"pmids\": [\"41182836\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"Synaptopodin maintains cerebrovascular homeostasis by positively regulating cdh2 (N-cadherin); synpo mutant zebrafish show elevated cerebrovascular leakage after epinephrine challenge and higher incidence of intracerebral hemorrhage; cdh2 mRNA supplementation rescues the cerebrovascular leakage in synpo mutants.\",\n      \"method\": \"CRISPR/Cas9 synpo mutant zebrafish, epinephrine challenge assay, transcriptomic profiling of mutant brains, mRNA rescue experiment for cdh2\",\n      \"journal\": \"Yi chuan = Hereditas\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic KO with in vivo phenotype and specific mRNA rescue identifying downstream effector; single lab, zebrafish model\",\n      \"pmids\": [\"41992887\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"In striated and smooth muscle cells, SYNPO localizes to myofibrillar Z-discs, intercalated discs, and partially colocalizes with sarcoplasmic reticulum-associated STIM1; SYNPO binds filamin C (FLNc) via a small region homologous to the FLNc-binding region of SYNPO2, in addition to its known interactions with actin and α-actinin.\",\n      \"method\": \"Isoform characterization at RNA and protein levels, immunostaining of tissue sections, co-immunoprecipitation/protein interaction studies, transfection of SYNPO isoforms in skeletal myotubes and smooth muscle cells\",\n      \"journal\": \"Experimental cell research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct localization experiments plus Co-IP identifying new binding partner (FLNc); single lab, multiple muscle cell types\",\n      \"pmids\": [\"41941933\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Synpo KO rats generated by CRISPR-Cas9 lack the Synpo-dependent dendritic spine apparatus and cisternal organelles in the axon initial segment (AIS); inhibitory synapses in the wild-type AIS cluster preferentially near cisternal organelles, a pattern disrupted in KO rats where synapses are more uniformly distributed; LTP is reduced in KO rats.\",\n      \"method\": \"CRISPR-Cas9 KO rat, 3D electron microscopy reconstruction of dendritic spines and AIS, LTP electrophysiology, synaptic quantification\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic KO with ultrastructural 3D EM and electrophysiology; preprint, single lab\",\n      \"pmids\": [\"41394584\"],\n      \"is_preprint\": true\n    }\n  ],\n  \"current_model\": \"Synaptopodin (SYNPO) is a proline-rich actin-associated scaffolding protein that binds F-actin (via a central domain) and alpha-actinin (via its C-terminus) to elongate and stabilize actin filaments in highly dynamic compartments including podocyte foot processes, dendritic spines, and the axon initial segment cisternal organelle; it regulates RhoA/Rac1/CDC42 GTPase balance to control actin dynamics, promotes forward trafficking of BKCa channels to the cell surface in a Rho-dependent manner, cooperates with BAG3 to facilitate autophagosome-lysosome fusion and clearance of phospho-tau at post-synaptic densities, acts with KLHL17 to maintain the spine apparatus ER network for activity-dependent spine enlargement and calcium signaling, interacts with MAGI-2 and alpha-actinin-4 to position actin bundles within podocyte foot processes, binds the KIBRA WW1 domain via PPXY motifs, and in endothelial and epithelial cells promotes wound healing and barrier integrity downstream of laminar shear stress and butyrate/IL-13 signaling respectively.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"Synaptopodin (SYNPO) is an actin-associated scaffolding protein that organizes and stabilizes dynamic actin-based compartments in podocytes, neurons, and epithelial/endothelial cells [#0, #10]. It binds F-actin through a central motif and alpha-actinin through its C-terminal domain, elongating alpha-actinin-induced actin filaments and protecting stress fibers from disruption; the alpha-actinin-binding C-terminus is required for dendritic targeting and postsynaptic accumulation [#0, #1, #3]. In podocytes SYNPO governs actin architecture by shifting the balance of small GTPases—its loss reduces RhoA and CDC42 activity while increasing Rac1, collapsing stress fibers, expanding focal adhesions, and impairing migration [#10, #12]. It assembles into adhesion and junction complexes with CD2AP, MAGI-2, and alpha-actinin-4 to position actin bundles within foot processes, and SYNPO loss sensitizes the glomerulus to injury in adriamycin and Alport models [#2, #16, #13]; loss-of-function mutations that fail to rescue CDC42 activity and migration implicate SYNPO as a candidate monogenic cause of nephrotic syndrome [#12]. In neurons SYNPO is a component of the spine apparatus ER and the axon initial segment cisternal organelle, where it acts with KLHL17 to maintain spine ER clusters that support activity-dependent spine enlargement, calcium signaling, and downstream ERK/c-Fos activation [#14, #5], and it cooperates with BAG3 to enable post-synaptic autophagosome–lysosome fusion and clearance of p62 and phospho-tau [#8]. Beyond the cytoskeleton, SYNPO promotes forward trafficking of BKCa channels to the cell surface in a Rho-dependent manner [#4], and its expression is induced by butyrate, IL-13, and laminar shear stress to drive epithelial and endothelial wound healing and barrier integrity [#11, #7, #15]; STAT3 signaling sustains SYNPO protein levels against cathepsin L-dependent proteolysis [#6].\",\n  \"teleology\": [\n    {\n      \"year\": 2005,\n      \"claim\": \"Established the core biochemical activity of SYNPO: how a proline-rich protein controls actin architecture, by showing it binds alpha-actinin and elongates alpha-actinin-induced actin filaments across podocytes and neurons.\",\n      \"evidence\": \"Isoform characterization, co-IP, in vitro actin filament assays, and synpo-/- mouse\",\n      \"pmids\": [\"15841212\", \"15659229\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not resolve how the central F-actin motif and C-terminal alpha-actinin site coordinate filament bundling quantitatively\", \"Mechanism linking actin elongation to spine/foot process morphology not yet defined\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Placed SYNPO in a podocyte adhesion network by demonstrating genetic and physical interaction with CD2AP, showing that combined SYNPO/CD2AP dosage loss causes glomerular disease.\",\n      \"evidence\": \"Co-IP and bigenic heterozygous mouse models with proteinuria/histopathology readouts\",\n      \"pmids\": [\"16628251\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct molecular contact between SYNPO and CD2AP versus indirect bridging not distinguished\", \"Role of Fyn phosphorylation of SYNPO not addressed\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Connected SYNPO's actin-stabilizing activity to a functional neuronal output by showing it stabilizes activity-dependent spine enlargement and protects stress fibers.\",\n      \"evidence\": \"Overexpression in hippocampal neurons with NMDA activation, live spine imaging, and F-actin protection assay\",\n      \"pmids\": [\"18424168\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Based on overexpression rather than endogenous loss-of-function\", \"Did not identify the molecular intermediary linking SYNPO to spine volume persistence\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Defined the structural context of SYNPO in the axon initial segment, showing its cisternal-organelle association is activity-independent and requires ankyrin G.\",\n      \"evidence\": \"In vitro neuronal maturation, immunofluorescence, TTX blockade, detergent extraction, and ankyrin G perturbation\",\n      \"pmids\": [\"21708259\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct binding partners anchoring SYNPO at the AIS not identified\", \"Functional consequence of the cisternal organelle left open\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Identified upstream control of SYNPO abundance, showing STAT3 signaling protects SYNPO from cathepsin L proteolysis, and an independent role for SYNPO in endothelial wound healing under shear stress.\",\n      \"evidence\": \"STAT3 inhibition/knockdown, cytokine and protease-inhibitor treatments, immunoblot; separately laminar shear stress with siRNA/overexpression and wound assays in HUVECs\",\n      \"pmids\": [\"25425624\", \"24561195\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct STAT3 transcriptional targeting of SYNPO versus indirect stabilization not separated\", \"Mechanism by which SYNPO drives endothelial migration unresolved\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Extended SYNPO function beyond cytoskeletal scaffolding to membrane channel trafficking, showing it promotes Rho-dependent surface delivery of BKCa channels.\",\n      \"evidence\": \"Reciprocal co-IP, heterologous expression, stable knockdown, surface biotinylation, and electrophysiology\",\n      \"pmids\": [\"20630939\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether SYNPO directly chaperones channels or acts indirectly via actin/Rho not resolved\", \"Physiological relevance of BKCa trafficking in intact podocytes not tested\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Demonstrated cytokine-driven epithelial regulation, with IL-13 inducing SYNPO transcriptionally/epigenetically to control esophageal epithelial motility and barrier/differentiation balance.\",\n      \"evidence\": \"siRNA, overexpression, wound-healing and barrier assays, IL-13 treatment, and histone modification analysis\",\n      \"pmids\": [\"29046486\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Transcription factors mediating IL-13 induction not identified\", \"Mechanism by which excess SYNPO impairs barrier integrity unclear\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Resolved two distinct postsynaptic mechanisms: SYNPO partners with BAG3 to drive autophagosome-lysosome fusion clearing phospho-tau, and biophysically defined the SYNPO-KIBRA WW-domain interaction.\",\n      \"evidence\": \"Dual shRNA knockdown with autophagy flux/substrate readouts; separately ITC, CD, and NMR with mutagenesis on KIBRA WW domains\",\n      \"pmids\": [\"30744518\", \"31597702\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How SYNPO mechanistically promotes autophagosome-lysosome fusion not defined\", \"Functional consequence of the KIBRA-SYNPO PPXY interaction in cells not established\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Defined SYNPO as a master regulator of the podocyte GTPase balance and a candidate disease gene, with KO shifting RhoA/Rac1/CDC42 activity and patient mutations failing to rescue CDC42 and migration.\",\n      \"evidence\": \"CRISPR KO mouse and primary podocytes with GTPase assays, migration assays, adriamycin challenge; whole-exome sequencing with WT-versus-mutant cDNA rescue\",\n      \"pmids\": [\"32938649\", \"33615071\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How SYNPO couples to GTPase regulators (GEFs/GAPs) not identified\", \"Absence of spontaneous KO phenotype indicates redundancy that is unexplained\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Established a microbiota-host axis whereby butyrate induces SYNPO via HDAC inhibition to maintain intestinal tight junctions and barrier integrity.\",\n      \"evidence\": \"Knockdown, butyrate/HDAC-inhibitor studies, TEER and wound assays, enteroids, and Synpo KO mouse DSS colitis\",\n      \"pmids\": [\"32398370\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct HDAC target locus driving SYNPO induction not mapped\", \"Molecular link between SYNPO and tight-junction assembly unresolved\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Showed SYNPO modulates injury responses by regulating myosin IIA redistribution, with its loss accelerating Alport glomerular disease.\",\n      \"evidence\": \"Synpo x Col4a5 double-mutant mice with albuminuria, EM, and myosin IIA immunofluorescence\",\n      \"pmids\": [\"34029143\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct interaction of SYNPO with myosin IIA versus indirect effect not distinguished\", \"Mechanism of foot process effacement contribution incomplete\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Defined the spine apparatus ER mechanism, showing KLHL17 acts with SYNPO to maintain spine ER clusters required for activity-dependent enlargement, calcium signaling, and ERK/c-Fos activation.\",\n      \"evidence\": \"Klhl17 KO and haploinsufficient mice, expansion microscopy, calcium imaging, ERK/c-Fos assays, and co-IP\",\n      \"pmids\": [\"37651441\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether KLHL17 acts as a Cullin3 adaptor toward SYNPO not tested\", \"How spine ER clustering mechanistically gates calcium events unresolved\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Mapped additional structural and tissue-specific partners, placing SYNPO in a podocyte MAGI-2/alpha-actinin-4 complex and in muscle Z-discs binding filamin C.\",\n      \"evidence\": \"Podocyte MAGI-2 KO mice with co-IP and actin localization; isoform/localization characterization and co-IP for FLNc in muscle cells\",\n      \"pmids\": [\"41182836\", \"41941933\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional consequence of the SYNPO-FLNc interaction in muscle physiology not tested\", \"Hierarchy of SYNPO binding among actin, alpha-actinin, MAGI-2, and FLNc unresolved\"]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Extended SYNPO function to cerebrovascular integrity, identifying N-cadherin (cdh2) as a downstream effector whose supplementation rescues vascular leakage in synpo mutants.\",\n      \"evidence\": \"CRISPR synpo mutant zebrafish, epinephrine challenge, transcriptomics, and cdh2 mRNA rescue\",\n      \"pmids\": [\"41992887\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"How SYNPO transcriptionally or post-transcriptionally regulates cdh2 not defined\", \"Cell type mediating the cerebrovascular phenotype not pinpointed\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How SYNPO mechanistically couples actin scaffolding to the small-GTPase switches (RhoA/Rac1/CDC42) and to ER/organelle positioning across its diverse tissue contexts remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No GEF/GAP intermediary linking SYNPO to GTPase regulation identified\", \"No structural model of full-length SYNPO with actin and alpha-actinin\", \"Unifying mechanism across podocyte, neuronal, and epithelial roles not established\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0008092\", \"supporting_discovery_ids\": [0, 1, 3, 10, 18]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [0, 2, 16, 14, 9]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [10, 12]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005856\", \"supporting_discovery_ids\": [0, 1, 7, 11, 18]},\n      {\"term_id\": \"GO:0005783\", \"supporting_discovery_ids\": [14, 19]},\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [4, 11]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-9612973\", \"supporting_discovery_ids\": [8]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [10, 12, 4]},\n      {\"term_id\": \"R-HSA-112316\", \"supporting_discovery_ids\": [14, 19]}\n    ],\n    \"complexes\": [\"spine apparatus\", \"axon initial segment cisternal organelle\", \"podocyte MAGI-2/alpha-actinin-4 complex\"],\n    \"partners\": [\"ACTN4\", \"CD2AP\", \"KCNMA1\", \"BAG3\", \"WWC1\", \"KLHL17\", \"MAGI2\", \"FLNC\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":6,"faith_total":6,"faith_pct":100.0}}