{"gene":"FHOD1","run_date":"2026-06-09T23:54:43","timeline":{"discoveries":[{"year":2001,"finding":"FHOD1 (FHOS) interacts with the polybasic domain of Rac1 C-terminus in a guanine nucleotide-independent manner but does not bind RhoA, Cdc42Hs, Rac2, or Rac3. Intramolecular autoinhibitory interactions between the C-terminus of FHOS and an N-terminal region partially overlapping the Rac1 interaction domain were identified. Truncation mutants lacking either the N- or C-terminal autoregulatory domains stimulated transcription from the SRE reporter, indicating these regions suppress activity.","method":"Yeast two-hybrid, co-immunoprecipitation, reporter gene assay, immunofluorescence","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal binding assays and functional reporter assays in single lab with multiple orthogonal methods","pmids":["11590143"],"is_preprint":false},{"year":2003,"finding":"A constitutively active form of FHOD1 associates with F-actin and induces thick actin stress fibers in NIH3T3 cells via FH1 and FH2 domains. These cytoskeletal effects require the Rho-ROCK cascade (acting downstream of Rho) but Rac1 (not Rho or Cdc42) binds FHOD1 in cells and recruits it to actin filaments and lamellipodia/membrane ruffles. Activated FHOD1 also interferes with lamellipodia formation.","method":"Co-immunoprecipitation, dominant-negative GTPase expression, pharmacological inhibitors (C3, Y-27632), immunofluorescence, SRE-reporter assay","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods in single lab establishing GTPase specificity and pathway placement","pmids":["12857739"],"is_preprint":false},{"year":2003,"finding":"Fhos (FHOD1) in its active form induces actin stress fibers. The protein normally exists in a closed inactive form via intramolecular interaction between the N-terminal region and the C-terminal DAD. Both FH1 and FH2 domains are required for stress fiber induction, but the N-terminal region mediates F-actin binding required for targeting to stress fibers. Fhos forms a homotypic complex via direct FH2 domain self-association in cells.","method":"In vitro F-actin binding assay, co-immunoprecipitation, deletion mutant analysis, immunofluorescence","journal":"Journal of cell science","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vitro binding combined with cell-based domain mapping, single lab","pmids":["14576350"],"is_preprint":false},{"year":2003,"finding":"Full-length FHOD1 co-localizes with filamentous actin at cell peripheries and enhances cell migration to collagen and fibronectin. The FH1 and FH2 domains are required for stress fiber formation. A C-terminal truncation (ΔC, 1-1010) lacking the autoinhibitory domain induces prominent stress fibers sensitive to dominant-negative Rac, C3 transferase, and Y-27632, placing FHOD1 downstream of Rac and Rho-ROCK.","method":"Stable overexpression, migration assays (Boyden chamber/transwell), immunofluorescence, pharmacological inhibition","journal":"Journal of cell science","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple functional assays with domain dissection, single lab","pmids":["12665555"],"is_preprint":false},{"year":2004,"finding":"FHOD1 is a direct binding partner and phosphorylation substrate of cyclic GMP-dependent protein kinase I (PKGI) in vascular smooth muscle cells. The FHOD1 C-terminus (aa 964-1165) binds full-length PKGIα, and this interaction is decreased 3- to 5-fold by the PKG activator 8Br-cGMP. PKGI directly phosphorylates FHOD1 at Ser-1131 in vitro and in intact cells.","method":"Yeast two-hybrid, GST pull-down, in vitro kinase assay, intact cell phosphorylation assay, site-directed mutagenesis of peptides","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro kinase assay with mutagenesis identifying specific phosphorylation site, complemented by pull-down and intact cell studies","pmids":["15051728"],"is_preprint":false},{"year":2004,"finding":"FHOD1 binds the cytoplasmic domain of the EBV receptor CD21 through its C-terminus. EBV binding to CD21 stimulates plasma membrane aggregation, redistribution, and co-localization of FHOD1 with CD21. FHOD1 (FHOS) localizes to the cytoplasm and accumulates with actin in membrane protrusions when expressed in cells.","method":"Co-immunoprecipitation, co-localization by confocal microscopy, EBV stimulation assay","journal":"Journal of cell science","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — co-IP and co-localization showing ligand-stimulated interaction, single lab, two methods","pmids":["15138285"],"is_preprint":false},{"year":2004,"finding":"FHOD1 interacts with WISH-B (isoform of WASP-interacting SH3-domain protein/diaphanous-interacting protein), cyclophilin B, and PRKCBP1 via its FH1 domain. WISH-B altered the solubility of FHOD1 in vitro, and a WISH-B truncation mutant (aa 1-227) disrupted FHOD1-induced stress fibers without affecting FHOD1-mediated SRF-dependent gene transcription. Stabilization of F-actin prevented FHOD1-dependent SRF promoter activation in high serum.","method":"Yeast two-hybrid screen, in vitro binding/solubility assay, immunofluorescence, reporter gene assay","journal":"Journal of cellular biochemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — yeast two-hybrid combined with in vitro and cell-based functional assays, single lab","pmids":["15095401"],"is_preprint":false},{"year":2005,"finding":"Active FHOD1 coordinates actin stress fibers with microtubules, causing parallel alignment of microtubules and cell elongation. FH1 and FH2 domains are both strictly required for these cytoskeletal effects. Formation of FHOD1-actin fibers is a prerequisite for microtubule polarization, but sustained cell elongation requires both filament systems simultaneously. These effects depend on Rho-ROCK cascade activity but not Rac or Cdc42.","method":"Expression of constitutively active FHOD1 deletion mutants, pharmacological depolymerization of actin (cytochalasin D) or microtubules (nocodazole), dominant-negative GTPase expression, immunofluorescence","journal":"Experimental cell research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal perturbations with defined readouts, single lab","pmids":["15878344"],"is_preprint":false},{"year":2005,"finding":"FHOD1 contains a C-terminal 60-amino acid DAD that recognizes an N-terminal FH3 domain to establish autoinhibition. The FH3 domain of FHOD1 does not overlap with the Rac1-binding domain. The DAD contains one functional hydrophobic autoregulatory motif and a basic cluster; simultaneous mutation of both efficiently releases autoinhibition, inducing stress fibers and SRE transcription. NMR analysis shows the FHOD1 DAD is intrinsically unstructured with a tendency for helical conformation at the hydrophobic motif.","method":"In vitro binding assay, site-directed mutagenesis, NMR spectroscopy, size exclusion chromatography, cell-based reporter assay and immunofluorescence","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — NMR structure combined with in vitro binding and mutagenesis defining autoinhibitory mechanism, multiple orthogonal methods","pmids":["16361249"],"is_preprint":false},{"year":2005,"finding":"FHOD1 oligomerizes via a coiled-coil motif C-terminal to the core FH2 domain. Deletion of this coiled-coil motif abrogates FHOD1-induced actin stress fibers and SRE transcriptional activation, but does not disrupt physical or functional interaction with Rac1, indicating oligomerization is separately required for cytoskeletal and transcriptional activities.","method":"Yeast two-hybrid, co-immunoprecipitation, co-localization, deletion mutant cell-based assays","journal":"FEBS letters","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal interaction assays combined with functional domain dissection, single lab","pmids":["15642356"],"is_preprint":false},{"year":2005,"finding":"Src kinase activity is required for FHOD1 distribution to lamellipodia and for FHOD1-induced SRE and skeletal actin promoter gene expression, but Src inhibition does not affect constitutively active FHOD1-induced stress fiber formation. Additionally, Src activity is necessary to maintain FHOD1 mRNA levels.","method":"Pharmacological Src inhibition, dominant-negative constructs, reporter gene assay, immunofluorescence","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple functional readouts with pharmacological and genetic inhibition, single lab","pmids":["16169515"],"is_preprint":false},{"year":2005,"finding":"FHOD1 co-precipitates with components of the ERK MAP kinase pathway (but not p38 or JNK) and co-localizes with Raf-1 at lamellipodia and MEK at stress fibers. FHOD1-induced SRE gene expression is dependent on ERK MAP kinase activation, whereas FHOD1-induced stress fiber formation and skeletal actin promoter transcription are ERK-independent.","method":"Co-immunoprecipitation, immunofluorescence co-localization, pharmacological MEK inhibition, reporter gene assay","journal":"Biochemical and biophysical research communications","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single lab, co-IP without reciprocal validation, partial mechanistic follow-up","pmids":["16112087"],"is_preprint":false},{"year":2006,"finding":"Caspase-3 cleaves FHOD1 at the SVPD(616) site during apoptosis. The N-terminal cleavage product is distributed diffusely in cytoplasm and nucleoplasm, while the C-terminal cleavage product localizes almost exclusively to the nucleus with nucleolar enrichment and inhibits RNA polymerase I transcription (blocks BrUTP incorporation in run-on transcription assay).","method":"Caspase cleavage assay, site identification by mutagenesis, confocal microscopy, run-on transcription assay with BrUTP","journal":"Apoptosis","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — cleavage site identified with functional consequence demonstrated by run-on assay, single lab, multiple methods","pmids":["17013756"],"is_preprint":false},{"year":2008,"finding":"ROCK phosphorylates FHOD1 at C-terminal residues Ser1131, Ser1137, and Thr1141, fully disrupting autoinhibitory intramolecular interaction between the N- and C-terminal regions, culminating in stress fiber formation. In vascular endothelial cells, thrombin (via G protein-coupled receptor→Rho→ROCK) elicits FHOD1 phosphorylation and stress fiber formation in a ROCK-dependent manner; FHOD1 depletion by RNAi impairs thrombin-induced stress fiber formation.","method":"In vitro kinase assay, site-directed mutagenesis, intramolecular interaction assay, RNAi knockdown, thrombin stimulation, immunoblot with phospho-specific antibodies","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro kinase assay with site-directed mutagenesis identifying three phosphorylation sites, validated in cells with RNAi and ligand stimulation","pmids":["18239683"],"is_preprint":false},{"year":2008,"finding":"FHOD1 physically associates with ROCK1 via the N-terminal part of its FH2 domain binding the central domain of ROCK1. FHOD1 is an efficient ROCK1 phosphorylation substrate. Co-expression of FHOD1 and ROCK1 generates nonapoptotic plasma membrane blebs to which FHOD1 is recruited. Blebbing depends on F-actin integrity, the Rho-ROCK cascade, and Src activity. Efficient association of FHOD1 with ROCK1 and recruitment to blebs requires Src activity.","method":"Co-immunoprecipitation, domain mapping, in vitro kinase assay, RNAi knockdown, cell morphology assays in 2D and 3D matrices","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — in vitro kinase assay, reciprocal domain-mapping co-IP, and RNAi with defined cellular phenotype in single rigorous study","pmids":["18694941"],"is_preprint":false},{"year":2008,"finding":"Crystal structure of the N-terminal domains of FHOD1 (GBD and FH3) was determined. The FHOD1 GBD has a ubiquitin superfold (distinct from mDia1's GBD), and is recruited by Rac and Ras GTPases in cells and required for FHOD1-mediated actin remodeling. The FH3 domain is composed of five armadillo repeats. Mutation of one residue in the predicted DAD-interaction surface of FH3 efficiently activates FHOD1 in cells.","method":"X-ray crystallography, GTPase binding assays, site-directed mutagenesis, cell-based actin remodeling assay","journal":"Structure","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure combined with mutagenesis and functional cell validation in single study","pmids":["18786395"],"is_preprint":false},{"year":2011,"finding":"FHOD1 is a direct target of miR-200c. Knockdown of FHOD1 decreased expression and transcriptional activity of serum response factor (SRF) by interfering with translocation of the SRF coactivator MRTF-A, leading to downregulation of myosin light chain 2 (MLC2) expression and phosphorylation, impairing stress fiber formation and contractility.","method":"miR-200c modulation, siRNA knockdown, MRTF-A localization assay, SRF reporter assay, immunoblot for MLC2","journal":"Molecular and cellular biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods placing FHOD1 in MRTF-A/SRF/MLC2 pathway, single lab","pmids":["22144583"],"is_preprint":false},{"year":2013,"finding":"FHOD1 is recruited to integrin clusters in an early step of adhesion formation, resulting in actin assembly. FHOD1 knockdown impairs cell spreading, coordinated force application, and adhesion maturation. Targeting of FHOD1 to integrin sites depends on direct interaction with Src family kinases and is upstream of activation by Rho kinase.","method":"siRNA knockdown, spreading assays on lipid bilayers and solid substrates, high-resolution force-sensing pillar arrays, co-immunoprecipitation with Src family kinases","journal":"Developmental cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal interaction data with functional force-sensing assay and multiple substrate conditions, clearly placing FHOD1 in Src→integrin→ROCK pathway","pmids":["24331927"],"is_preprint":false},{"year":2013,"finding":"The formin FHOD1 and small GTPase Rac1 cooperate to promote vaccinia virus actin tail formation. FHOD1 depletion decreased CEV actin tail number and elongation rate. FHOD1 recruitment to actin tails requires its GTPase-binding domain and FH2 domain. Rac1 is activated at the membrane surrounding actin tails; Rac1 depletion or dominant-negative Rac1 phenocopies FHOD1 depletion and prevents FHOD1 recruitment. FHOD1 overexpression rescues actin tail defects from dominant-negative Rac1, placing FHOD1 downstream of Rac1.","method":"siRNA knockdown, dominant-negative Rac1 expression, FHOD1 domain truncation/rescue experiments, live imaging of actin tails","journal":"The Journal of cell biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — epistasis established by rescue experiments, multiple methods, single lab","pmids":["24062339"],"is_preprint":false},{"year":2013,"finding":"Aurora-B kinase phosphorylates FHOD1; phosphomutant FHOD1 is impaired in post-mitotic assembly of oriented actin cables required for daughter cell spreading after cell division. APC/C(Cdh1) restricts a cell-cortex-associated pool of active Aurora-B in space and time, and Aurora-B retention at the cortex in early G1 depends on FHOD1.","method":"APC/C(Cdh1) manipulation, phospho-site identification in FHOD1, phosphomutant expression, immunofluorescence of actin cables and Aurora-B localization","journal":"Journal of cell science","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — phospho-site identification with phosphomutant functional assay and epistasis, single lab","pmids":["23613471"],"is_preprint":false},{"year":2014,"finding":"FHOD1 directly interacts with nesprin-2 giant (N2G), an outer nuclear membrane component. Silencing FHOD1 or expressing binding-domain fragments disrupts nuclear movement and centrosome orientation in polarizing fibroblasts. FHOD1 silencing does not affect formation or rearward flow of dorsal actin cables, but N2G-FHOD1 interaction provides a second attachment point to actin cables essential for TAN line formation and nuclear translocation.","method":"Co-immunoprecipitation, siRNA knockdown, dominant-negative fragment expression, live-cell imaging of nuclear movement, centrosome orientation assay","journal":"Nature cell biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal interaction data, rescue experiments, live imaging with defined mechanistic model, published in high-impact journal with rigorous controls","pmids":["24880667"],"is_preprint":false},{"year":2014,"finding":"FHOD1 controls stress fiber organization by differentially regulating two precursor populations: it inhibits dorsal fiber growth (which requires parallel long actin filament polymerization) while stimulating transverse arc formation (from fusion of short antiparallel filaments). The GBD and FH3 domains mediate stress fiber association and co-localization with myosin. FHOD1 lacking GBD/FH3 retains full capacity to stimulate arc and ventral stress fiber formation.","method":"siRNA knockdown, FHOD1 domain mutant expression, live-cell imaging, immunofluorescence for stress fiber subtypes and myosin","journal":"Journal of cell science","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple domain mutants and live imaging distinguishing mechanistic roles, single lab","pmids":["24481812"],"is_preprint":false},{"year":2014,"finding":"FHOD1 is localized at intercalated discs and costameres in adult and neonatal cardiomyocytes, co-localizing with cadherin, plakoglobin, and connexin43 at the intercalated disc. N-terminal domain mediates subcellular targeting; constructs lacking this domain show aberrant localization.","method":"Confocal immunofluorescence, subcellular fractionation, immunoblot of isolated intercalated discs, expression of deletion constructs in neonatal cardiomyocytes","journal":"Anatomical record","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — fractionation combined with deletion construct targeting assay, single lab","pmids":["25125170"],"is_preprint":false},{"year":2017,"finding":"FHOD1 acts downstream of the LINC complex (lamin/nesprin-1) to mediate mechanosensing in muscle cell precursors. Pathogenic LMNA or SYNE-1 mutations cause excess contractile stress fibers, increased focal adhesions, and higher traction forces, all rescued by FHOD1 depletion or inactivation. ROCK inhibition prevents cytoskeletal defects, and FHOD1 is a ROCK-dependent effector placing it in the lamin/nesprin-1→ROCK→FHOD1 axis.","method":"Traction force microscopy, siRNA knockdown, ROCK inhibitor (Y-27632), patient-derived LMNA/SYNE-1 mutant cell lines, immunofluorescence","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — traction force microscopy with RNAi rescue, multiple inhibitors, single lab","pmids":["28455503"],"is_preprint":false},{"year":2019,"finding":"Active FHOD1 (C-terminal truncation) is recruited to all three types of actin stress fibers and is more incorporated with myosin II than α-actinin. Active FHOD1 emerges from the cell periphery and moves centripetally with transverse arcs. FHOD1 knockdown causes defective actomyosin bundle maturation with longer non-contractile dorsal stress fibers and slower actin centripetal flow, resulting in abnormal cell spreading and migration.","method":"FHOD1 truncation/active mutant expression, siRNA knockdown, live TIRF/confocal imaging of actin and myosin dynamics, FRAP for turnover measurements","journal":"The Biochemical journal","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — live imaging and FRAP with functional knockdown assays, single lab","pmids":["31657439"],"is_preprint":false},{"year":2021,"finding":"Crystal structures of FHOD1 bound to nesprin-2G and nesprin-1G spectrin repeats (SRs) reveal that the presumed GBD of FHOD1 is actually a spectrin repeat-binding enhancer for the neighboring FH3 domain. SR binding by FHOD1 is likely not regulated by the DAD helix. Nesprin-1G also contains one FHOD1-binding SR, indicating overlapping functions of nesprins in actin-bundle recruitment for nuclear movement.","method":"X-ray crystallography, binding assays","journal":"Structure","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure of FHOD1-nesprin complex redefining domain function with in vitro binding validation","pmids":["33472039"],"is_preprint":false},{"year":2023,"finding":"FHOD1 knockdown enhances ferroptosis sensitivity in glioma cells via upregulation of methylated HSPB1 (a negative regulator of ferroptosis). Overexpression of HSPB1 reverses FHOD1 knockdown-mediated ferroptosis, placing HSPB1 downstream of FHOD1 in ferroptosis regulation.","method":"siRNA knockdown, HSPB1 overexpression rescue, ferroptosis sensitivity assays, proteomics","journal":"CNS neuroscience & therapeutics","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single lab, mechanistic pathway placement based on rescue assay without direct biochemical interaction demonstrated","pmids":["37211949"],"is_preprint":false},{"year":2023,"finding":"Activated FHOD1 promotes actin filament assembly and hypertrophy in vascular smooth muscle cells in response to Ang-II, and mediates hypertensive tunica media thickening in vivo. Activated FHOD1 or its C-terminal DAD domain upregulates RNF213 via stabilization of RNF213 protein (independent of G-actin/F-actin ratio, transcription, or translation), which in turn promotes collagen-1α/collagen-3α synthesis.","method":"In vivo hypertensive rat models, siRNA/overexpression in VSMCs, proteomics, collagen synthesis assays, FHOD1 phosphorylation analysis","journal":"Journal of molecular and cellular cardiology","confidence":"Low","confidence_rationale":"Tier 3 / Weak — novel pathway identified by proteomics/rescue but mechanistic detail of RNF213 stabilization not biochemically resolved, single lab","pmids":["37482037"],"is_preprint":false},{"year":2024,"finding":"PRMT7 methylates arginine residues (R1130/R1132 in FHOD1 DAD domain equivalent positions) in the diaphanous autoinhibitory domain of FHOD family proteins in vitro. If the adjacent serine (corresponding to Ser-1131 in FHOD1) is first phosphorylated by ROCK1, PRMT7 cannot subsequently methylate the neighboring arginines, indicating that phosphorylation and methylation at the DAD are mutually antagonistic PTMs.","method":"In vitro methylation assay with recombinant PRMT7, in vitro ROCK1 kinase assay, site-directed mutagenesis","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution with mutagenesis, but primarily characterized for FHOD3 with extension to FHOD1 family; single lab","pmids":["39368550"],"is_preprint":false},{"year":2025,"finding":"An in silico structural model (AlphaFold3) of the FHOD1 autoinhibitory complex (DID-DAD) indicates that an extended polybasic region unique to the FHOD subfamily stabilizes autoinhibitory interactions. Site-directed mutagenesis of polybasic region residues experimentally validates this prediction and confirms its role in autoinhibition and its disruption upon phosphorylation-dependent activation.","method":"AlphaFold3 structural modeling, site-directed mutagenesis, cell-based actin remodeling assay","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — computational model validated by mutagenesis defining unique structural mechanism, but single lab and no experimental structure","pmids":["41448430"],"is_preprint":false},{"year":2025,"finding":"In 3D breast acini, FHOD1 is required for nuclear positioning and lumen formation downstream of nesprin-2G and SUN proteins. FHOD1 depletion disrupts a dynamic basal actin spot linking the nucleus to plasma membrane β1-integrin through the LINC complex and inhibits lumen formation.","method":"siRNA knockdown, 3D acini culture, live-cell imaging, nesprin-2 degron system, confocal microscopy","journal":"bioRxiv","confidence":"Low","confidence_rationale":"Tier 2 / Weak — preprint, single lab, functional localization with defined phenotype but not yet peer-reviewed","pmids":[],"is_preprint":true}],"current_model":"FHOD1 is a diaphanous-related formin that is normally held in a closed, autoinhibited conformation via intramolecular FH3–DAD interaction; it is activated principally by ROCK-mediated phosphorylation at C-terminal residues (Ser1131, Ser1137, Thr1141) downstream of Rho/G-protein-coupled receptor signaling (e.g., thrombin), but also by Src-dependent targeting to integrin clusters upstream of ROCK; once active, its FH1 and FH2 domains nucleate and bundle actin filaments, promoting transverse arc formation and ventral stress fiber maturation, driving cell migration, spreading, and force generation; at the nucleus, FHOD1 interacts directly with nesprin-2G spectrin repeats via its FH3 domain to form TAN lines that couple the nucleus to moving dorsal actin cables for nuclear positioning; FHOD1 additionally serves as a substrate for PKGIα (phosphorylated at Ser1131, weakening their interaction in response to cGMP) and for Aurora-B kinase (coordinating post-mitotic actin cable assembly), and its DAD-region arginines can be methylated by PRMT7 in a manner mutually antagonistic with ROCK phosphorylation."},"narrative":{"mechanistic_narrative":"FHOD1 is a diaphanous-related formin that nucleates and organizes actin filaments to drive stress fiber maturation, cell spreading, migration, force generation, and nuclear positioning [PMID:12665555, PMID:24331927, PMID:31657439]. In its resting state the protein is held in a closed, autoinhibited conformation through an intramolecular interaction between the N-terminal FH3/DID region and a C-terminal DAD; the DAD is intrinsically unstructured with a hydrophobic autoregulatory motif and a basic cluster, and an extended polybasic region unique to the FHOD subfamily stabilizes this autoinhibited complex [PMID:14576350, PMID:16361249, PMID:41448430]. Activation is principally driven by ROCK, which phosphorylates Ser1131, Ser1137, and Thr1141 to disrupt the autoinhibitory interaction downstream of Rho/GPCR signaling such as thrombin stimulation [PMID:18239683]; FHOD1 binds ROCK1 directly through its FH2 domain and is targeted to integrin clusters by Src family kinases upstream of ROCK during adhesion formation [PMID:18694941, PMID:24331927]. Once relieved of autoinhibition, the FH1 and FH2 domains drive formation of thick actin stress fibers, biasing precursor populations toward transverse arc and ventral stress fiber maturation while restraining dorsal fiber elongation, and coordinating actomyosin bundle maturation with centripetal flow [PMID:12857739, PMID:24481812, PMID:31657439]. At the nucleus, FHOD1 binds nesprin-2 giant (and nesprin-1G) spectrin repeats to provide a second attachment point that couples the nucleus to moving dorsal actin cables, forming TAN lines required for nuclear movement and centrosome orientation; structural work redefined the presumed GTPase-binding domain as a spectrin-repeat-binding enhancer for the adjacent FH3 domain [PMID:24880667, PMID:33472039]. FHOD1 activity is further tuned by additional post-translational modifications: PKGIα phosphorylates Ser1131 in response to cGMP to weaken its own interaction with FHOD1, Aurora-B phosphorylation coordinates post-mitotic actin cable assembly, and PRMT7 methylation of DAD arginines is mutually antagonistic with ROCK phosphorylation [PMID:15051728, PMID:23613471, PMID:39368550]. Beyond the cytoskeleton, FHOD1 also feeds into MRTF-A/SRF-dependent transcription [PMID:22144583].","teleology":[{"year":2001,"claim":"Established that FHOD1 binds a specific GTPase and is held inactive by intramolecular autoregulation, framing it as a switchable cytoskeletal effector rather than a constitutive one.","evidence":"Yeast two-hybrid, co-IP, and SRE reporter assays mapping Rac1 binding and N-/C-terminal autoinhibitory regions","pmids":["11590143"],"confidence":"Medium","gaps":["GTPase specificity (Rac vs Rho) for downstream cytoskeletal effects unresolved","molecular basis of the intramolecular contact not defined","no actin-nucleation activity demonstrated"]},{"year":2003,"claim":"Showed that relieved FHOD1 nucleates actin stress fibers via FH1/FH2 and operates downstream of the Rho-ROCK cascade, placing it in a defined signaling-to-cytoskeleton pathway and linking it to cell migration.","evidence":"Constitutively active/truncation mutants, dominant-negative GTPases, C3/Y-27632 inhibitors, F-actin binding, and migration assays in NIH3T3 cells","pmids":["12857739","14576350","12665555"],"confidence":"Medium","gaps":["how Rac binding relates to Rho-ROCK activation mechanistically unclear","no direct biochemical actin assembly kinetics","physiological activating stimulus not identified"]},{"year":2004,"claim":"Identified FHOD1 as a direct PKGI substrate and a partner of additional receptors and adaptors, broadening the input signals and protein context that regulate it.","evidence":"Y2H, GST pull-down, in vitro kinase assay defining Ser1131, plus co-IP/co-localization with CD21 and FH1-domain partners (WISH-B, cyclophilin B, PRKCBP1)","pmids":["15051728","15138285","15095401"],"confidence":"Medium","gaps":["functional consequence of Ser1131 phosphorylation on actin activity at the time unresolved","physiological relevance of CD21 binding limited to EBV context","FH1-partner functions only partially characterized"]},{"year":2005,"claim":"Defined the structural and oligomeric basis of FHOD1 autoinhibition and activation, and linked Src and ERK signaling to distinct FHOD1 outputs (transcription vs stress fibers).","evidence":"NMR of the DAD, in vitro DAD-FH3 binding/mutagenesis, coiled-coil deletion, Src/MEK inhibition with reporter assays, microtubule co-organization assays","pmids":["16361249","15642356","16169515","16112087","15878344"],"confidence":"Medium","gaps":["DAD-FH3 release trigger in cells not yet mapped to a kinase","ERK pathway link is a single-lab co-IP without reciprocal validation","separation of transcriptional vs cytoskeletal mechanisms incomplete"]},{"year":2006,"claim":"Revealed a caspase-3-dependent processing of FHOD1 generating a nuclear/nucleolar C-terminal fragment that represses RNA polymerase I, extending FHOD1 function into apoptotic nuclear regulation.","evidence":"Caspase cleavage assay with site mutagenesis, confocal localization, and BrUTP run-on transcription assay","pmids":["17013756"],"confidence":"Medium","gaps":["physiological role of the nuclear fragment in apoptosis unclear","mechanism of Pol I repression not defined","relationship to cytoskeletal function unknown"]},{"year":2008,"claim":"Identified ROCK as the principal activating kinase, mapping three phosphosites that disrupt autoinhibition, and provided the N-terminal crystal structure redefining the GBD and FH3 architecture.","evidence":"In vitro kinase assay with site-directed mutagenesis (Ser1131/Ser1137/Thr1141), thrombin stimulation, RNAi, reciprocal ROCK1 domain-mapping co-IP, and X-ray crystallography of GBD/FH3","pmids":["18239683","18694941","18786395"],"confidence":"High","gaps":["how Src targeting and ROCK activation are coordinated spatially not fully resolved","structure of the full autoinhibited complex absent","in vivo significance of bleb formation unclear"]},{"year":2011,"claim":"Placed FHOD1 within the MRTF-A/SRF transcriptional circuit, showing it feeds back on contractile gene expression and is itself regulated by miR-200c.","evidence":"miR-200c modulation, siRNA, MRTF-A localization, SRF reporter, and MLC2 immunoblotting","pmids":["22144583"],"confidence":"Medium","gaps":["direct vs actin-dynamics-mediated effect on MRTF-A not separated","single-lab pathway placement","in vivo relevance not established"]},{"year":2013,"claim":"Established FHOD1 as a Src-recruited early effector at integrin adhesions controlling force generation, and extended its roles to pathogen actin tails and post-mitotic actin assembly via Aurora-B.","evidence":"Force-sensing pillar arrays with siRNA and Src co-IP, vaccinia actin-tail epistasis/rescue with Rac1, and Aurora-B phosphomutant assays with APC/C(Cdh1) manipulation","pmids":["24331927","24062339","23613471"],"confidence":"High","gaps":["Aurora-B phosphosite functional integration with ROCK sites unresolved","molecular link between Src targeting and ROCK activation incompletely defined","Rac1-dependent recruitment mechanism not biochemically detailed"]},{"year":2014,"claim":"Defined FHOD1's direct role in nuclear positioning through nesprin-2G binding and clarified its differential control of stress fiber subtypes, while localizing it to cardiomyocyte junctions.","evidence":"Co-IP and live imaging of TAN lines/nuclear movement, domain-mutant stress fiber analyses, and intercalated disc fractionation/localization in cardiomyocytes","pmids":["24880667","24481812","25125170"],"confidence":"High","gaps":["how FHOD1 simultaneously bundles actin and binds nesprin not structurally resolved here","regulation of FHOD1 at the nuclear envelope unclear","functional role at intercalated discs not tested"]},{"year":2017,"claim":"Positioned FHOD1 as the ROCK-dependent effector downstream of the LINC complex in mechanosensing, linking laminopathy mutations to excess contractility through FHOD1.","evidence":"Traction force microscopy with patient-derived LMNA/SYNE-1 mutant cells, siRNA rescue, and ROCK inhibition","pmids":["28455503"],"confidence":"Medium","gaps":["direct molecular link between LINC complex and ROCK activation not defined","single-lab study","tissue-level disease relevance not established"]},{"year":2021,"claim":"Structurally redefined the FHOD1 'GBD' as a spectrin-repeat-binding enhancer for FH3, explaining nesprin engagement and the overlapping roles of nesprin-1G and nesprin-2G in actin-cable recruitment.","evidence":"X-ray crystallography of FHOD1-nesprin spectrin-repeat complexes with binding assays","pmids":["33472039"],"confidence":"High","gaps":["whether spectrin-repeat binding and actin bundling are simultaneous unresolved","regulation of nesprin binding in cells not addressed","relation to GTPase binding reported earlier requires reconciliation"]},{"year":2024,"claim":"Demonstrated a PTM crosstalk code at the DAD: PRMT7 methylation of arginines is mutually exclusive with ROCK phosphorylation of the adjacent serine, adding a regulatory layer to FHOD1 activation.","evidence":"In vitro PRMT7 methylation and ROCK1 kinase assays with site-directed mutagenesis","pmids":["39368550"],"confidence":"Medium","gaps":["primarily characterized for FHOD3 with extension to FHOD1","cellular consequence of methylation not shown","no demonstration of dynamic switching in vivo"]},{"year":2025,"claim":"Refined the structural model of FHOD1 autoinhibition, identifying a subfamily-unique polybasic region that stabilizes the DID-DAD complex and is disrupted upon phosphorylation-dependent activation.","evidence":"AlphaFold3 modeling validated by site-directed mutagenesis and cell-based actin remodeling assays","pmids":["41448430"],"confidence":"Medium","gaps":["no experimental structure of the autoinhibited complex","single-lab computational model","quantitative contribution of polybasic region to activation kinetics unknown"]},{"year":null,"claim":"How the multiple inputs (Src targeting, ROCK/PKGI/Aurora-B phosphorylation, PRMT7 methylation, GTPase 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Intramolecular autoinhibitory interactions between the C-terminus of FHOS and an N-terminal region partially overlapping the Rac1 interaction domain were identified. Truncation mutants lacking either the N- or C-terminal autoregulatory domains stimulated transcription from the SRE reporter, indicating these regions suppress activity.\",\n      \"method\": \"Yeast two-hybrid, co-immunoprecipitation, reporter gene assay, immunofluorescence\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal binding assays and functional reporter assays in single lab with multiple orthogonal methods\",\n      \"pmids\": [\"11590143\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"A constitutively active form of FHOD1 associates with F-actin and induces thick actin stress fibers in NIH3T3 cells via FH1 and FH2 domains. These cytoskeletal effects require the Rho-ROCK cascade (acting downstream of Rho) but Rac1 (not Rho or Cdc42) binds FHOD1 in cells and recruits it to actin filaments and lamellipodia/membrane ruffles. Activated FHOD1 also interferes with lamellipodia formation.\",\n      \"method\": \"Co-immunoprecipitation, dominant-negative GTPase expression, pharmacological inhibitors (C3, Y-27632), immunofluorescence, SRE-reporter assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods in single lab establishing GTPase specificity and pathway placement\",\n      \"pmids\": [\"12857739\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"Fhos (FHOD1) in its active form induces actin stress fibers. The protein normally exists in a closed inactive form via intramolecular interaction between the N-terminal region and the C-terminal DAD. Both FH1 and FH2 domains are required for stress fiber induction, but the N-terminal region mediates F-actin binding required for targeting to stress fibers. Fhos forms a homotypic complex via direct FH2 domain self-association in cells.\",\n      \"method\": \"In vitro F-actin binding assay, co-immunoprecipitation, deletion mutant analysis, immunofluorescence\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vitro binding combined with cell-based domain mapping, single lab\",\n      \"pmids\": [\"14576350\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"Full-length FHOD1 co-localizes with filamentous actin at cell peripheries and enhances cell migration to collagen and fibronectin. The FH1 and FH2 domains are required for stress fiber formation. A C-terminal truncation (ΔC, 1-1010) lacking the autoinhibitory domain induces prominent stress fibers sensitive to dominant-negative Rac, C3 transferase, and Y-27632, placing FHOD1 downstream of Rac and Rho-ROCK.\",\n      \"method\": \"Stable overexpression, migration assays (Boyden chamber/transwell), immunofluorescence, pharmacological inhibition\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple functional assays with domain dissection, single lab\",\n      \"pmids\": [\"12665555\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"FHOD1 is a direct binding partner and phosphorylation substrate of cyclic GMP-dependent protein kinase I (PKGI) in vascular smooth muscle cells. The FHOD1 C-terminus (aa 964-1165) binds full-length PKGIα, and this interaction is decreased 3- to 5-fold by the PKG activator 8Br-cGMP. PKGI directly phosphorylates FHOD1 at Ser-1131 in vitro and in intact cells.\",\n      \"method\": \"Yeast two-hybrid, GST pull-down, in vitro kinase assay, intact cell phosphorylation assay, site-directed mutagenesis of peptides\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro kinase assay with mutagenesis identifying specific phosphorylation site, complemented by pull-down and intact cell studies\",\n      \"pmids\": [\"15051728\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"FHOD1 binds the cytoplasmic domain of the EBV receptor CD21 through its C-terminus. EBV binding to CD21 stimulates plasma membrane aggregation, redistribution, and co-localization of FHOD1 with CD21. FHOD1 (FHOS) localizes to the cytoplasm and accumulates with actin in membrane protrusions when expressed in cells.\",\n      \"method\": \"Co-immunoprecipitation, co-localization by confocal microscopy, EBV stimulation assay\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — co-IP and co-localization showing ligand-stimulated interaction, single lab, two methods\",\n      \"pmids\": [\"15138285\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"FHOD1 interacts with WISH-B (isoform of WASP-interacting SH3-domain protein/diaphanous-interacting protein), cyclophilin B, and PRKCBP1 via its FH1 domain. WISH-B altered the solubility of FHOD1 in vitro, and a WISH-B truncation mutant (aa 1-227) disrupted FHOD1-induced stress fibers without affecting FHOD1-mediated SRF-dependent gene transcription. Stabilization of F-actin prevented FHOD1-dependent SRF promoter activation in high serum.\",\n      \"method\": \"Yeast two-hybrid screen, in vitro binding/solubility assay, immunofluorescence, reporter gene assay\",\n      \"journal\": \"Journal of cellular biochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — yeast two-hybrid combined with in vitro and cell-based functional assays, single lab\",\n      \"pmids\": [\"15095401\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Active FHOD1 coordinates actin stress fibers with microtubules, causing parallel alignment of microtubules and cell elongation. FH1 and FH2 domains are both strictly required for these cytoskeletal effects. Formation of FHOD1-actin fibers is a prerequisite for microtubule polarization, but sustained cell elongation requires both filament systems simultaneously. These effects depend on Rho-ROCK cascade activity but not Rac or Cdc42.\",\n      \"method\": \"Expression of constitutively active FHOD1 deletion mutants, pharmacological depolymerization of actin (cytochalasin D) or microtubules (nocodazole), dominant-negative GTPase expression, immunofluorescence\",\n      \"journal\": \"Experimental cell research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal perturbations with defined readouts, single lab\",\n      \"pmids\": [\"15878344\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"FHOD1 contains a C-terminal 60-amino acid DAD that recognizes an N-terminal FH3 domain to establish autoinhibition. The FH3 domain of FHOD1 does not overlap with the Rac1-binding domain. The DAD contains one functional hydrophobic autoregulatory motif and a basic cluster; simultaneous mutation of both efficiently releases autoinhibition, inducing stress fibers and SRE transcription. NMR analysis shows the FHOD1 DAD is intrinsically unstructured with a tendency for helical conformation at the hydrophobic motif.\",\n      \"method\": \"In vitro binding assay, site-directed mutagenesis, NMR spectroscopy, size exclusion chromatography, cell-based reporter assay and immunofluorescence\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — NMR structure combined with in vitro binding and mutagenesis defining autoinhibitory mechanism, multiple orthogonal methods\",\n      \"pmids\": [\"16361249\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"FHOD1 oligomerizes via a coiled-coil motif C-terminal to the core FH2 domain. Deletion of this coiled-coil motif abrogates FHOD1-induced actin stress fibers and SRE transcriptional activation, but does not disrupt physical or functional interaction with Rac1, indicating oligomerization is separately required for cytoskeletal and transcriptional activities.\",\n      \"method\": \"Yeast two-hybrid, co-immunoprecipitation, co-localization, deletion mutant cell-based assays\",\n      \"journal\": \"FEBS letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal interaction assays combined with functional domain dissection, single lab\",\n      \"pmids\": [\"15642356\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Src kinase activity is required for FHOD1 distribution to lamellipodia and for FHOD1-induced SRE and skeletal actin promoter gene expression, but Src inhibition does not affect constitutively active FHOD1-induced stress fiber formation. Additionally, Src activity is necessary to maintain FHOD1 mRNA levels.\",\n      \"method\": \"Pharmacological Src inhibition, dominant-negative constructs, reporter gene assay, immunofluorescence\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple functional readouts with pharmacological and genetic inhibition, single lab\",\n      \"pmids\": [\"16169515\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"FHOD1 co-precipitates with components of the ERK MAP kinase pathway (but not p38 or JNK) and co-localizes with Raf-1 at lamellipodia and MEK at stress fibers. FHOD1-induced SRE gene expression is dependent on ERK MAP kinase activation, whereas FHOD1-induced stress fiber formation and skeletal actin promoter transcription are ERK-independent.\",\n      \"method\": \"Co-immunoprecipitation, immunofluorescence co-localization, pharmacological MEK inhibition, reporter gene assay\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single lab, co-IP without reciprocal validation, partial mechanistic follow-up\",\n      \"pmids\": [\"16112087\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Caspase-3 cleaves FHOD1 at the SVPD(616) site during apoptosis. The N-terminal cleavage product is distributed diffusely in cytoplasm and nucleoplasm, while the C-terminal cleavage product localizes almost exclusively to the nucleus with nucleolar enrichment and inhibits RNA polymerase I transcription (blocks BrUTP incorporation in run-on transcription assay).\",\n      \"method\": \"Caspase cleavage assay, site identification by mutagenesis, confocal microscopy, run-on transcription assay with BrUTP\",\n      \"journal\": \"Apoptosis\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — cleavage site identified with functional consequence demonstrated by run-on assay, single lab, multiple methods\",\n      \"pmids\": [\"17013756\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"ROCK phosphorylates FHOD1 at C-terminal residues Ser1131, Ser1137, and Thr1141, fully disrupting autoinhibitory intramolecular interaction between the N- and C-terminal regions, culminating in stress fiber formation. In vascular endothelial cells, thrombin (via G protein-coupled receptor→Rho→ROCK) elicits FHOD1 phosphorylation and stress fiber formation in a ROCK-dependent manner; FHOD1 depletion by RNAi impairs thrombin-induced stress fiber formation.\",\n      \"method\": \"In vitro kinase assay, site-directed mutagenesis, intramolecular interaction assay, RNAi knockdown, thrombin stimulation, immunoblot with phospho-specific antibodies\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro kinase assay with site-directed mutagenesis identifying three phosphorylation sites, validated in cells with RNAi and ligand stimulation\",\n      \"pmids\": [\"18239683\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"FHOD1 physically associates with ROCK1 via the N-terminal part of its FH2 domain binding the central domain of ROCK1. FHOD1 is an efficient ROCK1 phosphorylation substrate. Co-expression of FHOD1 and ROCK1 generates nonapoptotic plasma membrane blebs to which FHOD1 is recruited. Blebbing depends on F-actin integrity, the Rho-ROCK cascade, and Src activity. Efficient association of FHOD1 with ROCK1 and recruitment to blebs requires Src activity.\",\n      \"method\": \"Co-immunoprecipitation, domain mapping, in vitro kinase assay, RNAi knockdown, cell morphology assays in 2D and 3D matrices\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — in vitro kinase assay, reciprocal domain-mapping co-IP, and RNAi with defined cellular phenotype in single rigorous study\",\n      \"pmids\": [\"18694941\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Crystal structure of the N-terminal domains of FHOD1 (GBD and FH3) was determined. The FHOD1 GBD has a ubiquitin superfold (distinct from mDia1's GBD), and is recruited by Rac and Ras GTPases in cells and required for FHOD1-mediated actin remodeling. The FH3 domain is composed of five armadillo repeats. Mutation of one residue in the predicted DAD-interaction surface of FH3 efficiently activates FHOD1 in cells.\",\n      \"method\": \"X-ray crystallography, GTPase binding assays, site-directed mutagenesis, cell-based actin remodeling assay\",\n      \"journal\": \"Structure\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure combined with mutagenesis and functional cell validation in single study\",\n      \"pmids\": [\"18786395\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"FHOD1 is a direct target of miR-200c. Knockdown of FHOD1 decreased expression and transcriptional activity of serum response factor (SRF) by interfering with translocation of the SRF coactivator MRTF-A, leading to downregulation of myosin light chain 2 (MLC2) expression and phosphorylation, impairing stress fiber formation and contractility.\",\n      \"method\": \"miR-200c modulation, siRNA knockdown, MRTF-A localization assay, SRF reporter assay, immunoblot for MLC2\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods placing FHOD1 in MRTF-A/SRF/MLC2 pathway, single lab\",\n      \"pmids\": [\"22144583\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"FHOD1 is recruited to integrin clusters in an early step of adhesion formation, resulting in actin assembly. FHOD1 knockdown impairs cell spreading, coordinated force application, and adhesion maturation. Targeting of FHOD1 to integrin sites depends on direct interaction with Src family kinases and is upstream of activation by Rho kinase.\",\n      \"method\": \"siRNA knockdown, spreading assays on lipid bilayers and solid substrates, high-resolution force-sensing pillar arrays, co-immunoprecipitation with Src family kinases\",\n      \"journal\": \"Developmental cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal interaction data with functional force-sensing assay and multiple substrate conditions, clearly placing FHOD1 in Src→integrin→ROCK pathway\",\n      \"pmids\": [\"24331927\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"The formin FHOD1 and small GTPase Rac1 cooperate to promote vaccinia virus actin tail formation. FHOD1 depletion decreased CEV actin tail number and elongation rate. FHOD1 recruitment to actin tails requires its GTPase-binding domain and FH2 domain. Rac1 is activated at the membrane surrounding actin tails; Rac1 depletion or dominant-negative Rac1 phenocopies FHOD1 depletion and prevents FHOD1 recruitment. FHOD1 overexpression rescues actin tail defects from dominant-negative Rac1, placing FHOD1 downstream of Rac1.\",\n      \"method\": \"siRNA knockdown, dominant-negative Rac1 expression, FHOD1 domain truncation/rescue experiments, live imaging of actin tails\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — epistasis established by rescue experiments, multiple methods, single lab\",\n      \"pmids\": [\"24062339\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Aurora-B kinase phosphorylates FHOD1; phosphomutant FHOD1 is impaired in post-mitotic assembly of oriented actin cables required for daughter cell spreading after cell division. APC/C(Cdh1) restricts a cell-cortex-associated pool of active Aurora-B in space and time, and Aurora-B retention at the cortex in early G1 depends on FHOD1.\",\n      \"method\": \"APC/C(Cdh1) manipulation, phospho-site identification in FHOD1, phosphomutant expression, immunofluorescence of actin cables and Aurora-B localization\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — phospho-site identification with phosphomutant functional assay and epistasis, single lab\",\n      \"pmids\": [\"23613471\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"FHOD1 directly interacts with nesprin-2 giant (N2G), an outer nuclear membrane component. Silencing FHOD1 or expressing binding-domain fragments disrupts nuclear movement and centrosome orientation in polarizing fibroblasts. FHOD1 silencing does not affect formation or rearward flow of dorsal actin cables, but N2G-FHOD1 interaction provides a second attachment point to actin cables essential for TAN line formation and nuclear translocation.\",\n      \"method\": \"Co-immunoprecipitation, siRNA knockdown, dominant-negative fragment expression, live-cell imaging of nuclear movement, centrosome orientation assay\",\n      \"journal\": \"Nature cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal interaction data, rescue experiments, live imaging with defined mechanistic model, published in high-impact journal with rigorous controls\",\n      \"pmids\": [\"24880667\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"FHOD1 controls stress fiber organization by differentially regulating two precursor populations: it inhibits dorsal fiber growth (which requires parallel long actin filament polymerization) while stimulating transverse arc formation (from fusion of short antiparallel filaments). The GBD and FH3 domains mediate stress fiber association and co-localization with myosin. FHOD1 lacking GBD/FH3 retains full capacity to stimulate arc and ventral stress fiber formation.\",\n      \"method\": \"siRNA knockdown, FHOD1 domain mutant expression, live-cell imaging, immunofluorescence for stress fiber subtypes and myosin\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple domain mutants and live imaging distinguishing mechanistic roles, single lab\",\n      \"pmids\": [\"24481812\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"FHOD1 is localized at intercalated discs and costameres in adult and neonatal cardiomyocytes, co-localizing with cadherin, plakoglobin, and connexin43 at the intercalated disc. N-terminal domain mediates subcellular targeting; constructs lacking this domain show aberrant localization.\",\n      \"method\": \"Confocal immunofluorescence, subcellular fractionation, immunoblot of isolated intercalated discs, expression of deletion constructs in neonatal cardiomyocytes\",\n      \"journal\": \"Anatomical record\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — fractionation combined with deletion construct targeting assay, single lab\",\n      \"pmids\": [\"25125170\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"FHOD1 acts downstream of the LINC complex (lamin/nesprin-1) to mediate mechanosensing in muscle cell precursors. Pathogenic LMNA or SYNE-1 mutations cause excess contractile stress fibers, increased focal adhesions, and higher traction forces, all rescued by FHOD1 depletion or inactivation. ROCK inhibition prevents cytoskeletal defects, and FHOD1 is a ROCK-dependent effector placing it in the lamin/nesprin-1→ROCK→FHOD1 axis.\",\n      \"method\": \"Traction force microscopy, siRNA knockdown, ROCK inhibitor (Y-27632), patient-derived LMNA/SYNE-1 mutant cell lines, immunofluorescence\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — traction force microscopy with RNAi rescue, multiple inhibitors, single lab\",\n      \"pmids\": [\"28455503\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Active FHOD1 (C-terminal truncation) is recruited to all three types of actin stress fibers and is more incorporated with myosin II than α-actinin. Active FHOD1 emerges from the cell periphery and moves centripetally with transverse arcs. FHOD1 knockdown causes defective actomyosin bundle maturation with longer non-contractile dorsal stress fibers and slower actin centripetal flow, resulting in abnormal cell spreading and migration.\",\n      \"method\": \"FHOD1 truncation/active mutant expression, siRNA knockdown, live TIRF/confocal imaging of actin and myosin dynamics, FRAP for turnover measurements\",\n      \"journal\": \"The Biochemical journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — live imaging and FRAP with functional knockdown assays, single lab\",\n      \"pmids\": [\"31657439\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Crystal structures of FHOD1 bound to nesprin-2G and nesprin-1G spectrin repeats (SRs) reveal that the presumed GBD of FHOD1 is actually a spectrin repeat-binding enhancer for the neighboring FH3 domain. SR binding by FHOD1 is likely not regulated by the DAD helix. Nesprin-1G also contains one FHOD1-binding SR, indicating overlapping functions of nesprins in actin-bundle recruitment for nuclear movement.\",\n      \"method\": \"X-ray crystallography, binding assays\",\n      \"journal\": \"Structure\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure of FHOD1-nesprin complex redefining domain function with in vitro binding validation\",\n      \"pmids\": [\"33472039\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"FHOD1 knockdown enhances ferroptosis sensitivity in glioma cells via upregulation of methylated HSPB1 (a negative regulator of ferroptosis). Overexpression of HSPB1 reverses FHOD1 knockdown-mediated ferroptosis, placing HSPB1 downstream of FHOD1 in ferroptosis regulation.\",\n      \"method\": \"siRNA knockdown, HSPB1 overexpression rescue, ferroptosis sensitivity assays, proteomics\",\n      \"journal\": \"CNS neuroscience & therapeutics\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single lab, mechanistic pathway placement based on rescue assay without direct biochemical interaction demonstrated\",\n      \"pmids\": [\"37211949\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Activated FHOD1 promotes actin filament assembly and hypertrophy in vascular smooth muscle cells in response to Ang-II, and mediates hypertensive tunica media thickening in vivo. Activated FHOD1 or its C-terminal DAD domain upregulates RNF213 via stabilization of RNF213 protein (independent of G-actin/F-actin ratio, transcription, or translation), which in turn promotes collagen-1α/collagen-3α synthesis.\",\n      \"method\": \"In vivo hypertensive rat models, siRNA/overexpression in VSMCs, proteomics, collagen synthesis assays, FHOD1 phosphorylation analysis\",\n      \"journal\": \"Journal of molecular and cellular cardiology\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — novel pathway identified by proteomics/rescue but mechanistic detail of RNF213 stabilization not biochemically resolved, single lab\",\n      \"pmids\": [\"37482037\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"PRMT7 methylates arginine residues (R1130/R1132 in FHOD1 DAD domain equivalent positions) in the diaphanous autoinhibitory domain of FHOD family proteins in vitro. If the adjacent serine (corresponding to Ser-1131 in FHOD1) is first phosphorylated by ROCK1, PRMT7 cannot subsequently methylate the neighboring arginines, indicating that phosphorylation and methylation at the DAD are mutually antagonistic PTMs.\",\n      \"method\": \"In vitro methylation assay with recombinant PRMT7, in vitro ROCK1 kinase assay, site-directed mutagenesis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstitution with mutagenesis, but primarily characterized for FHOD3 with extension to FHOD1 family; single lab\",\n      \"pmids\": [\"39368550\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"An in silico structural model (AlphaFold3) of the FHOD1 autoinhibitory complex (DID-DAD) indicates that an extended polybasic region unique to the FHOD subfamily stabilizes autoinhibitory interactions. Site-directed mutagenesis of polybasic region residues experimentally validates this prediction and confirms its role in autoinhibition and its disruption upon phosphorylation-dependent activation.\",\n      \"method\": \"AlphaFold3 structural modeling, site-directed mutagenesis, cell-based actin remodeling assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — computational model validated by mutagenesis defining unique structural mechanism, but single lab and no experimental structure\",\n      \"pmids\": [\"41448430\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"In 3D breast acini, FHOD1 is required for nuclear positioning and lumen formation downstream of nesprin-2G and SUN proteins. FHOD1 depletion disrupts a dynamic basal actin spot linking the nucleus to plasma membrane β1-integrin through the LINC complex and inhibits lumen formation.\",\n      \"method\": \"siRNA knockdown, 3D acini culture, live-cell imaging, nesprin-2 degron system, confocal microscopy\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 2 / Weak — preprint, single lab, functional localization with defined phenotype but not yet peer-reviewed\",\n      \"pmids\": [],\n      \"is_preprint\": true\n    }\n  ],\n  \"current_model\": \"FHOD1 is a diaphanous-related formin that is normally held in a closed, autoinhibited conformation via intramolecular FH3–DAD interaction; it is activated principally by ROCK-mediated phosphorylation at C-terminal residues (Ser1131, Ser1137, Thr1141) downstream of Rho/G-protein-coupled receptor signaling (e.g., thrombin), but also by Src-dependent targeting to integrin clusters upstream of ROCK; once active, its FH1 and FH2 domains nucleate and bundle actin filaments, promoting transverse arc formation and ventral stress fiber maturation, driving cell migration, spreading, and force generation; at the nucleus, FHOD1 interacts directly with nesprin-2G spectrin repeats via its FH3 domain to form TAN lines that couple the nucleus to moving dorsal actin cables for nuclear positioning; FHOD1 additionally serves as a substrate for PKGIα (phosphorylated at Ser1131, weakening their interaction in response to cGMP) and for Aurora-B kinase (coordinating post-mitotic actin cable assembly), and its DAD-region arginines can be methylated by PRMT7 in a manner mutually antagonistic with ROCK phosphorylation.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"FHOD1 is a diaphanous-related formin that nucleates and organizes actin filaments to drive stress fiber maturation, cell spreading, migration, force generation, and nuclear positioning [#3, #17, #24]. In its resting state the protein is held in a closed, autoinhibited conformation through an intramolecular interaction between the N-terminal FH3/DID region and a C-terminal DAD; the DAD is intrinsically unstructured with a hydrophobic autoregulatory motif and a basic cluster, and an extended polybasic region unique to the FHOD subfamily stabilizes this autoinhibited complex [#2, #8, #29]. Activation is principally driven by ROCK, which phosphorylates Ser1131, Ser1137, and Thr1141 to disrupt the autoinhibitory interaction downstream of Rho/GPCR signaling such as thrombin stimulation [#13]; FHOD1 binds ROCK1 directly through its FH2 domain and is targeted to integrin clusters by Src family kinases upstream of ROCK during adhesion formation [#14, #17]. Once relieved of autoinhibition, the FH1 and FH2 domains drive formation of thick actin stress fibers, biasing precursor populations toward transverse arc and ventral stress fiber maturation while restraining dorsal fiber elongation, and coordinating actomyosin bundle maturation with centripetal flow [#1, #21, #24]. At the nucleus, FHOD1 binds nesprin-2 giant (and nesprin-1G) spectrin repeats to provide a second attachment point that couples the nucleus to moving dorsal actin cables, forming TAN lines required for nuclear movement and centrosome orientation; structural work redefined the presumed GTPase-binding domain as a spectrin-repeat-binding enhancer for the adjacent FH3 domain [#20, #25]. FHOD1 activity is further tuned by additional post-translational modifications: PKGI\\u03b1 phosphorylates Ser1131 in response to cGMP to weaken its own interaction with FHOD1, Aurora-B phosphorylation coordinates post-mitotic actin cable assembly, and PRMT7 methylation of DAD arginines is mutually antagonistic with ROCK phosphorylation [#4, #19, #28]. Beyond the cytoskeleton, FHOD1 also feeds into MRTF-A/SRF-dependent transcription [#16].\",\n  \"teleology\": [\n    {\n      \"year\": 2001,\n      \"claim\": \"Established that FHOD1 binds a specific GTPase and is held inactive by intramolecular autoregulation, framing it as a switchable cytoskeletal effector rather than a constitutive one.\",\n      \"evidence\": \"Yeast two-hybrid, co-IP, and SRE reporter assays mapping Rac1 binding and N-/C-terminal autoinhibitory regions\",\n      \"pmids\": [\"11590143\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"GTPase specificity (Rac vs Rho) for downstream cytoskeletal effects unresolved\", \"molecular basis of the intramolecular contact not defined\", \"no actin-nucleation activity demonstrated\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Showed that relieved FHOD1 nucleates actin stress fibers via FH1/FH2 and operates downstream of the Rho-ROCK cascade, placing it in a defined signaling-to-cytoskeleton pathway and linking it to cell migration.\",\n      \"evidence\": \"Constitutively active/truncation mutants, dominant-negative GTPases, C3/Y-27632 inhibitors, F-actin binding, and migration assays in NIH3T3 cells\",\n      \"pmids\": [\"12857739\", \"14576350\", \"12665555\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"how Rac binding relates to Rho-ROCK activation mechanistically unclear\", \"no direct biochemical actin assembly kinetics\", \"physiological activating stimulus not identified\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Identified FHOD1 as a direct PKGI substrate and a partner of additional receptors and adaptors, broadening the input signals and protein context that regulate it.\",\n      \"evidence\": \"Y2H, GST pull-down, in vitro kinase assay defining Ser1131, plus co-IP/co-localization with CD21 and FH1-domain partners (WISH-B, cyclophilin B, PRKCBP1)\",\n      \"pmids\": [\"15051728\", \"15138285\", \"15095401\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"functional consequence of Ser1131 phosphorylation on actin activity at the time unresolved\", \"physiological relevance of CD21 binding limited to EBV context\", \"FH1-partner functions only partially characterized\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Defined the structural and oligomeric basis of FHOD1 autoinhibition and activation, and linked Src and ERK signaling to distinct FHOD1 outputs (transcription vs stress fibers).\",\n      \"evidence\": \"NMR of the DAD, in vitro DAD-FH3 binding/mutagenesis, coiled-coil deletion, Src/MEK inhibition with reporter assays, microtubule co-organization assays\",\n      \"pmids\": [\"16361249\", \"15642356\", \"16169515\", \"16112087\", \"15878344\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"DAD-FH3 release trigger in cells not yet mapped to a kinase\", \"ERK pathway link is a single-lab co-IP without reciprocal validation\", \"separation of transcriptional vs cytoskeletal mechanisms incomplete\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Revealed a caspase-3-dependent processing of FHOD1 generating a nuclear/nucleolar C-terminal fragment that represses RNA polymerase I, extending FHOD1 function into apoptotic nuclear regulation.\",\n      \"evidence\": \"Caspase cleavage assay with site mutagenesis, confocal localization, and BrUTP run-on transcription assay\",\n      \"pmids\": [\"17013756\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"physiological role of the nuclear fragment in apoptosis unclear\", \"mechanism of Pol I repression not defined\", \"relationship to cytoskeletal function unknown\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Identified ROCK as the principal activating kinase, mapping three phosphosites that disrupt autoinhibition, and provided the N-terminal crystal structure redefining the GBD and FH3 architecture.\",\n      \"evidence\": \"In vitro kinase assay with site-directed mutagenesis (Ser1131/Ser1137/Thr1141), thrombin stimulation, RNAi, reciprocal ROCK1 domain-mapping co-IP, and X-ray crystallography of GBD/FH3\",\n      \"pmids\": [\"18239683\", \"18694941\", \"18786395\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"how Src targeting and ROCK activation are coordinated spatially not fully resolved\", \"structure of the full autoinhibited complex absent\", \"in vivo significance of bleb formation unclear\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Placed FHOD1 within the MRTF-A/SRF transcriptional circuit, showing it feeds back on contractile gene expression and is itself regulated by miR-200c.\",\n      \"evidence\": \"miR-200c modulation, siRNA, MRTF-A localization, SRF reporter, and MLC2 immunoblotting\",\n      \"pmids\": [\"22144583\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"direct vs actin-dynamics-mediated effect on MRTF-A not separated\", \"single-lab pathway placement\", \"in vivo relevance not established\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Established FHOD1 as a Src-recruited early effector at integrin adhesions controlling force generation, and extended its roles to pathogen actin tails and post-mitotic actin assembly via Aurora-B.\",\n      \"evidence\": \"Force-sensing pillar arrays with siRNA and Src co-IP, vaccinia actin-tail epistasis/rescue with Rac1, and Aurora-B phosphomutant assays with APC/C(Cdh1) manipulation\",\n      \"pmids\": [\"24331927\", \"24062339\", \"23613471\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Aurora-B phosphosite functional integration with ROCK sites unresolved\", \"molecular link between Src targeting and ROCK activation incompletely defined\", \"Rac1-dependent recruitment mechanism not biochemically detailed\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Defined FHOD1's direct role in nuclear positioning through nesprin-2G binding and clarified its differential control of stress fiber subtypes, while localizing it to cardiomyocyte junctions.\",\n      \"evidence\": \"Co-IP and live imaging of TAN lines/nuclear movement, domain-mutant stress fiber analyses, and intercalated disc fractionation/localization in cardiomyocytes\",\n      \"pmids\": [\"24880667\", \"24481812\", \"25125170\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"how FHOD1 simultaneously bundles actin and binds nesprin not structurally resolved here\", \"regulation of FHOD1 at the nuclear envelope unclear\", \"functional role at intercalated discs not tested\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Positioned FHOD1 as the ROCK-dependent effector downstream of the LINC complex in mechanosensing, linking laminopathy mutations to excess contractility through FHOD1.\",\n      \"evidence\": \"Traction force microscopy with patient-derived LMNA/SYNE-1 mutant cells, siRNA rescue, and ROCK inhibition\",\n      \"pmids\": [\"28455503\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"direct molecular link between LINC complex and ROCK activation not defined\", \"single-lab study\", \"tissue-level disease relevance not established\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Structurally redefined the FHOD1 'GBD' as a spectrin-repeat-binding enhancer for FH3, explaining nesprin engagement and the overlapping roles of nesprin-1G and nesprin-2G in actin-cable recruitment.\",\n      \"evidence\": \"X-ray crystallography of FHOD1-nesprin spectrin-repeat complexes with binding assays\",\n      \"pmids\": [\"33472039\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"whether spectrin-repeat binding and actin bundling are simultaneous unresolved\", \"regulation of nesprin binding in cells not addressed\", \"relation to GTPase binding reported earlier requires reconciliation\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Demonstrated a PTM crosstalk code at the DAD: PRMT7 methylation of arginines is mutually exclusive with ROCK phosphorylation of the adjacent serine, adding a regulatory layer to FHOD1 activation.\",\n      \"evidence\": \"In vitro PRMT7 methylation and ROCK1 kinase assays with site-directed mutagenesis\",\n      \"pmids\": [\"39368550\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"primarily characterized for FHOD3 with extension to FHOD1\", \"cellular consequence of methylation not shown\", \"no demonstration of dynamic switching in vivo\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Refined the structural model of FHOD1 autoinhibition, identifying a subfamily-unique polybasic region that stabilizes the DID-DAD complex and is disrupted upon phosphorylation-dependent activation.\",\n      \"evidence\": \"AlphaFold3 modeling validated by site-directed mutagenesis and cell-based actin remodeling assays\",\n      \"pmids\": [\"41448430\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"no experimental structure of the autoinhibited complex\", \"single-lab computational model\", \"quantitative contribution of polybasic region to activation kinetics unknown\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How the multiple inputs (Src targeting, ROCK/PKGI/Aurora-B phosphorylation, PRMT7 methylation, GTPase binding) are integrated to set FHOD1 activity in space and time, and the in vivo significance of its proposed roles in ferroptosis and hypertensive remodeling, remain unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"no unified structural model of the full-length autoinhibited-to-active transition\", \"ferroptosis (HSPB1) and RNF213/hypertension links rest on low-confidence rescue assays without direct biochemistry\", \"no integrated quantitative model of competing PTMs\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0008092\", \"supporting_discovery_ids\": [2, 3, 21, 24]},\n      {\"term_id\": \"GO:0140110\", \"supporting_discovery_ids\": [16]},\n      {\"term_id\": \"GO:0060089\", \"supporting_discovery_ids\": [23, 17]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005856\", \"supporting_discovery_ids\": [1, 21, 24]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [5]},\n      {\"term_id\": \"GO:0005635\", \"supporting_discovery_ids\": [20, 25]},\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [17, 14]},\n      {\"term_id\": \"GO:0005730\", \"supporting_discovery_ids\": [12]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [13, 17]},\n      {\"term_id\": \"R-HSA-74160\", \"supporting_discovery_ids\": [16]},\n      {\"term_id\": \"R-HSA-1640170\", \"supporting_discovery_ids\": [19]},\n      {\"term_id\": \"R-HSA-9609507\", \"supporting_discovery_ids\": [20]}\n    ],\n    \"complexes\": [\"LINC complex (nesprin/SUN)\", \"TAN lines\"],\n    \"partners\": [\"ROCK1\", \"Rac1\", \"PRKG1\", \"SYNE2\", \"SYNE1\", \"SRC\", \"PRMT7\", \"AURKB\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":7,"faith_total":7,"faith_pct":100.0}}