Affinage

TWF2

Twinfilin-2 · UniProt Q6IBS0

Round 2 corrected
Length
349 aa
Mass
39.5 kDa
Annotated
2026-04-28
52 papers in source corpus 7 papers cited in narrative 7 extracted findings

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

TWF2 (twinfilin-2) is a conserved actin-regulatory protein containing tandem ADF-H domains that caps actin filament barbed ends, binds actin monomers, and interacts with heterodimeric capping protein (CP/CAPZB), with the capacity to uncap CP from barbed ends to modulate actin dynamics and actomyosin contractility (PMID:18837697, PMID:41195540). The TWF2 gene produces two tissue-specific isoforms—Twf2a (non-muscle) and Twf2b (muscle)—through alternative promoter usage, differing in their nucleotide-actin binding preferences (PMID:18837697). In inner ear hair cells, TWF2 concentrates at the tips of row 2 mechanotransducing stereocilia in a mechanotransduction-dependent manner together with CAPZB and BAIAP2L2, contributing to stereocilia dimension control (PMID:28899994, PMID:31902726, PMID:34346063). In renal cell carcinoma, TWF2 directly binds YAP via residue M99 to competitively displace LATS1, preventing YAP ubiquitination and promoting its nuclear translocation, thereby driving tumor invasion and drug resistance (PMID:40948085).

Mechanistic history

Synthesis pass · year-by-year structured walk · 7 steps
  1. 1999 Medium

    Initial identification of TWF2 (then A6rp) as a ubiquitously expressed protein with predicted actin-binding domains established it as a PKCζ-interacting protein subject to phosphorylation by multiple kinases, opening the question of its actin-regulatory function.

    Evidence Yeast two-hybrid screen with PKCζ bait; in vitro kinase assays with recombinant GST-A6rp

    PMID:10406962

    Open questions at the time
    • Phosphorylation was shown only in vitro; physiological relevance of kinase-mediated regulation remains unaddressed
    • No direct demonstration of actin binding in this study
    • Functional consequence of PKCζ interaction not determined
  2. 2009 High

    Biochemical characterization resolved what TWF2 does at the molecular level: it caps filament barbed ends, binds actin monomers and heterodimeric capping protein, and generates two tissue-specific isoforms (Twf2a/Twf2b) with distinct nucleotide-actin preferences via alternative promoters.

    Evidence Recombinant protein barbed-end capping assays, monomer binding affinity measurements, and capping protein co-sedimentation; alternative promoter mapping in mouse

    PMID:18837697

    Open questions at the time
    • Cellular phenotype of TWF2 loss not yet examined
    • Functional significance of isoform-specific nucleotide preferences in vivo unknown
    • No structural information on how TWF2 interacts with capping protein or barbed ends
  3. 2017 High

    Localization studies in inner ear hair cells revealed that TWF2 and CAPZB co-concentrate at stereocilia tips during development, and conditional CAPZB deletion caused stereocilia shortening and loss of auditory/vestibular function, establishing a physiological context for the TWF2–CAPZB partnership.

    Evidence Conditional Capzb knockout (Atoh1-Cre) in mice; ABR and vestibular testing; confocal immunolocalization of TWF2 and CAPZB in cochlear hair cells

    PMID:28899994

    Open questions at the time
    • TWF2 itself was not genetically ablated; its independent contribution to stereocilia maintenance is inferred
    • Mechanism by which TWF2/CAPZB regulate stereocilia dimensions not resolved
  4. 2020 High

    The discovery that mechanotransduction channel activity is required for TWF2 and CAPZB concentration at row 2 stereocilia tips established that sensory activity specifies the molecular identity of transducing stereocilia, positioning TWF2 as a downstream effector of transduction signaling.

    Evidence Tmc1/Tmc2 double-KO and Tmie-KO mice plus pharmacological channel block; immunofluorescence quantification of TWF2 at stereocilia tips

    PMID:31902726

    Open questions at the time
    • Signaling pathway linking channel activity to TWF2 recruitment unknown
    • Whether TWF2 loss alone impairs stereocilia structure or hearing not tested
  5. 2021 High

    Identification of a multi-protein 'row 2 complex' (BAIAP2L2–TWF2–EPS8L2–CAPZB2) at mechanotransducing stereocilia tips, with BAIAP2L2 loss abolishing CAPZB2 tip localization and causing hearing loss, defined TWF2 as a component of a larger actin-regulatory assembly essential for auditory function.

    Evidence Co-immunoprecipitation of BAIAP2L2 with TWF2, EPS8L2, CAPZB2; Baiap2l2 KO mice with ABR, electrophysiology, and immunofluorescence

    PMID:34346063

    Open questions at the time
    • Direct binding stoichiometry and assembly order of the row 2 complex not determined
    • Specific contribution of TWF2 versus other complex members to tip architecture unresolved
  6. 2025 High

    In vivo and in vitro work in C. elegans demonstrated that twinfilin uncaps capping protein from barbed ends—a new biochemical activity—and modulates actomyosin contractility via F-actin regulation, with genetic epistasis confirming functional opposition between twinfilin and capping protein.

    Evidence In vitro barbed-end uncapping assays with recombinant proteins; C. elegans twf-2 and cap-1 double mutants; live imaging and F-actin/phospho-myosin quantification in spermatheca

    PMID:41195540

    Open questions at the time
    • Uncapping activity demonstrated with C. elegans ortholog; confirmation with mammalian TWF2 not yet reported
    • Structural basis for uncapping not resolved
    • Role of spectrin-mediated cortical recruitment in mammalian cells untested
  7. 2025 High

    An unexpected non-cytoskeletal function was uncovered: TWF2 directly binds YAP (residue M99–M225 interface), competitively displacing LATS1 to stabilize YAP and drive its nuclear translocation, promoting renal cell carcinoma invasion and sunitinib resistance—a gain-of-function mechanism targetable by salvianolic acid E.

    Evidence Co-IP and site-directed mutagenesis (M99A); gain/loss-of-function assays; patient-derived xenograft models; pharmacological inhibition of TWF2–YAP interaction

    PMID:40948085

    Open questions at the time
    • Whether YAP regulation by TWF2 is coupled to or independent of its actin-regulatory activities is unknown
    • Generalizability of the TWF2–YAP axis beyond renal cell carcinoma not established
    • Structural basis of the TWF2–YAP interaction beyond mutational mapping not available

Open questions

Synthesis pass · forward-looking unresolved questions
  • Key unresolved questions include the in vivo phenotype of mammalian TWF2 genetic ablation, the structural basis of TWF2's dual activities (barbed-end capping/uncapping versus YAP binding), and whether the actin-regulatory and Hippo-signaling functions of TWF2 are mechanistically linked.
  • No TWF2-specific knockout mouse phenotype reported
  • No crystal or cryo-EM structure of TWF2 in complex with capping protein or YAP
  • Functional interplay between cytoskeletal and signaling roles of TWF2 completely unexplored

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0008092 cytoskeletal protein binding 5 GO:0098772 molecular function regulator activity 2
Localization
GO:0005856 cytoskeleton 4 GO:0005929 cilium 3 GO:0005886 plasma membrane 1
Pathway
R-HSA-9709957 Sensory Perception 3 R-HSA-162582 Signal Transduction 1
Partners
BAIAP2L2CAPZBEPS8L2SPC-1/SPTAN1UNC-70/SPTBN1YAP1
Complex memberships
Row 2 stereocilia tip complex (BAIAP2L2–TWF2–EPS8L2–CAPZB2)

Evidence

Reading pass · 7 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
1999 TWF2 (then called A6-related protein, A6rp) was identified as a human protein with potential actin-binding and ATP-binding sites. It was cloned via yeast two-hybrid interaction screening using the catalytic domain of PKCζ as bait, and the recombinant GST-A6rp fusion protein was shown to be phosphorylated by PKCζ, casein kinase 2, and most effectively by the tyrosine kinase Src in vitro; phosphorylation by other PKC isoforms was minimal. The protein was expressed at mRNA and protein levels in all cells and tissues examined. Yeast two-hybrid cloning; in vitro phosphorylation assays with multiple kinases using GST-fusion protein; immunoblotting European journal of biochemistry Medium 10406962
2009 The mouse Twf2 gene generates two biochemically distinct, tissue-specific twinfilin isoforms (Twf2a and Twf2b) through alternative promoter usage. Twf2a is predominantly expressed in non-muscle tissues; Twf2b is restricted to heart and skeletal muscle. Both isoforms bind actin monomers and heterodimeric capping protein, and both cap actin filament barbed ends. However, the N-terminal ADF-H domain of Twf2b binds ADP-G-actin with ~5-fold higher affinity than ATP-G-actin, whereas the corresponding domain of Twf2a binds both nucleotide forms with equal affinity. Alternative promoter mapping; recombinant protein expression; actin monomer binding assays; capping protein binding assays; barbed-end capping assays; quantitative binding affinity measurements The Biochemical journal High 18837697
2017 TWF2 concentrates at stereocilia tips of inner ear hair cells as development progresses, co-localizing with its binding partner CAPZB (heterodimeric capping protein). Conditional deletion of Capzb in hair cells (Atoh1-Cre) eliminated auditory and vestibular function, with Capzb-null stereocilia initially developing normally but then shortening and losing width; TWF2 distribution mirrored CAPZB throughout development, consistent with a shared role in stereocilia dimension control. Conditional knockout (Atoh1-Cre); auditory brainstem response and vestibular function testing; fluorescence immunolocalization; confocal microscopy; quantification of stereocilia dimensions The Journal of cell biology High 28899994
2020 TWF2 and its partner CAPZB normally concentrate at the tips of row 2 (mechanotransducing) stereocilia in wild-type cochlear hair cells. In transduction mutants (Tmc1/Tmc2 double KO or Tmie KO) or when transduction channels are pharmacologically blocked, TWF2 and CAPZB2 fail to concentrate at row 2 tips, indicating that mechanotransduction activity specifies row 2 tip protein identity and is required for proper TWF2 localization. Genetic knockout mice (Tmc1KO;Tmc2KO; TmieKO); pharmacological transduction block; immunofluorescence imaging of cochlear explants; quantification of protein distribution at stereocilia tips Current biology : CB High 31902726
2021 BAIAP2L2 localizes to the tips of shorter-row (row 2) mechanotransducing stereocilia and physically interacts with TWF2 (as well as EPS8L2 and CAPZB2), forming a 'row 2 complex.' Loss of BAIAP2L2 causes degeneration of mechanotransducing stereocilia, profound hearing loss, and loss of mechanotransduction currents. The stereociliary tip localization of CAPZB2 (TWF2's binding partner) depends on functional BAIAP2L2. Co-immunoprecipitation (BAIAP2L2 binding to TWF2, EPS8L2, CAPZB2, CIB2); Baiap2l2 knockout mice; auditory brainstem response; FM 1-43FX dye uptake; electrophysiology; immunofluorescence Journal of cellular physiology High 34346063
2025 TWF2 promotes renal cell carcinoma invasion, migration, metastasis, and sunitinib resistance by inhibiting Hippo signaling. Mechanistically, TWF2 directly interacts with YAP via binding residues TWF2-M99 and YAP-M225, competitively displacing LATS1 (large tumor suppressor kinase 1) from YAP. This prevents YAP ubiquitination and degradation, leading to YAP stabilization and nuclear translocation. Mutation of M99 in TWF2 abolishes its tumor-promoting activity. The small molecule salvianolic acid E inhibits the TWF2–YAP interaction and synergistically enhances sunitinib efficacy in RCC models. Co-immunoprecipitation; site-directed mutagenesis (M99A); loss-of-function/gain-of-function cell assays; patient-derived xenograft models; small molecule inhibitor (salvianolic acid E) rescue experiments; nuclear fractionation/YAP translocation assays Advanced science (Weinheim, Baden-Wurttemberg, Germany) High 40948085
2025 The sole C. elegans twinfilin ortholog TWF-2 modulates actomyosin contractility in the spermatheca. TWF-2 localizes to the spermathecal cortex through interactions with α-spectrin (SPC-1) and β-spectrin (UNC-70). In vitro, TWF-2 inhibits ADP-actin filament depolymerization, modestly promotes ADP-Pi-actin filament depolymerization, and rapidly displaces capping protein (CAP-1 and CAP-2) from filament barbed ends (uncapping activity). In vivo, simultaneous loss of TWF-2 partially rescues embryonic lethality caused by CAP-1 depletion (genetic epistasis). Loss of the contractility regulator SPV-1 causes hypercontractility with elevated F-actin and phospho-myosin; removing TWF-2 suppresses this hypercontractility by reducing F-actin without affecting myosin phosphorylation. In vitro actin depolymerization/capping assays; C. elegans genetics (double mutants, epistasis); live imaging; immunofluorescence for F-actin and phospho-myosin quantification; Co-immunoprecipitation (spectrin interactions) Development (Cambridge, England) High 41195540

Source papers

Stage 0 corpus · 52 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2012 Insights into RNA biology from an atlas of mammalian mRNA-binding proteins. Cell 1718 22658674
2005 A human protein-protein interaction network: a resource for annotating the proteome. Cell 1704 16169070
2002 Generation and initial analysis of more than 15,000 full-length human and mouse cDNA sequences. Proceedings of the National Academy of Sciences of the United States of America 1479 12477932
2013 Genome-wide association analysis identifies 13 new risk loci for schizophrenia. Nature genetics 1192 23974872
2017 Architecture of the human interactome defines protein communities and disease networks. Nature 1085 28514442
2011 Large-scale genome-wide association analysis of bipolar disorder identifies a new susceptibility locus near ODZ4. Nature genetics 1068 21926972
2015 A human interactome in three quantitative dimensions organized by stoichiometries and abundances. Cell 1015 26496610
2004 Immunoaffinity profiling of tyrosine phosphorylation in cancer cells. Nature biotechnology 916 15592455
2007 Large-scale mapping of human protein-protein interactions by mass spectrometry. Molecular systems biology 733 17353931
2021 Dual proteome-scale networks reveal cell-specific remodeling of the human interactome. Cell 705 33961781
2012 A census of human soluble protein complexes. Cell 689 22939629
2011 Phylogenetic-based propagation of functional annotations within the Gene Ontology consortium. Briefings in bioinformatics 656 21873635
2011 Mapping the NPHP-JBTS-MKS protein network reveals ciliopathy disease genes and pathways. Cell 507 21565611
2004 The status, quality, and expansion of the NIH full-length cDNA project: the Mammalian Gene Collection (MGC). Genome research 438 15489334
2022 OpenCell: Endogenous tagging for the cartography of human cellular organization. Science (New York, N.Y.) 432 35271311
2015 Panorama of ancient metazoan macromolecular complexes. Nature 407 26344197
2021 A proximity-dependent biotinylation map of a human cell. Nature 339 34079125
2012 A high-throughput approach for measuring temporal changes in the interactome. Nature methods 273 22863883
2011 A directed protein interaction network for investigating intracellular signal transduction. Science signaling 258 21900206
2009 Proteomic analysis of human parotid gland exosomes by multidimensional protein identification technology (MudPIT). Journal of proteome research 237 19199708
2011 Toward an understanding of the protein interaction network of the human liver. Molecular systems biology 207 21988832
2020 Interactome analysis reveals that lncRNA HULC promotes aerobic glycolysis through LDHA and PKM2. Nature communications 167 32572027
2009 Gene-centric association signals for lipids and apolipoproteins identified via the HumanCVD BeadChip. American journal of human genetics 164 19913121
2014 E-cadherin interactome complexity and robustness resolved by quantitative proteomics. Science signaling 162 25468996
2019 A protein-interaction network of interferon-stimulated genes extends the innate immune system landscape. Nature immunology 159 30833792
2001 Toward a catalog of human genes and proteins: sequencing and analysis of 500 novel complete protein coding human cDNAs. Genome research 151 11230166
2018 Identification of phagocytosis regulators using magnetic genome-wide CRISPR screens. Nature genetics 146 30397336
2013 Proteomic analysis of podocyte exosome-enriched fraction from normal human urine. Journal of proteomics 126 23376485
2021 Protein interaction landscapes revealed by advanced in vivo cross-linking-mass spectrometry. Proceedings of the National Academy of Sciences of the United States of America 113 34349018
2018 Histone Interaction Landscapes Visualized by Crosslinking Mass Spectrometry in Intact Cell Nuclei. Molecular & cellular proteomics : MCP 101 30021884
2015 A CpG-methylation-based assay to predict survival in clear cell renal cell carcinoma. Nature communications 101 26515236
2020 Mechanotransduction-Dependent Control of Stereocilia Dimensions and Row Identity in Inner Hair Cells. Current biology : CB 59 31902726
2017 Heterodimeric capping protein is required for stereocilia length and width regulation. The Journal of cell biology 45 28899994
2009 Inhibition of monkeypox virus replication by RNA interference. Virology journal 45 19889227
1995 Biomimetic-dye affinity adsorbents for enzyme purification: application to the one-step purification of Candida boidinii formate dehydrogenase. Biotechnology and bioengineering 40 18623487
1992 Identification and expression of rpo19, a vaccinia virus gene encoding a 19-kilodalton DNA-dependent RNA polymerase subunit. Journal of virology 38 1731116
2022 Fludarabine, a Potential DNA-Dependent RNA Polymerase Inhibitor, as a Prospective Drug against Monkeypox Virus: A Computational Approach. Pharmaceuticals (Basel, Switzerland) 36 36145351
2009 Two biochemically distinct and tissue-specific twinfilin isoforms are generated from the mouse Twf2 gene by alternative promoter usage. The Biochemical journal 30 18837697
1995 Biomimetic dye affinity chromatography for the purification of bovine heart lactate dehydrogenase. Journal of chromatography. A 24 8556165
2021 BAIAP2L2 is required for the maintenance of mechanotransducing stereocilia of cochlear hair cells. Journal of cellular physiology 23 34346063
2018 CHAF1B knockdown blocks migration in a hepatocellular carcinoma model. Oncology reports 22 29767268
1986 Corn phosphoglycolate phosphatase: purification and properties. Planta 16 24232028
2021 Comparative Analysis of Skeletal Muscle DNA Methylation and Transcriptome of the Chicken Embryo at Different Developmental Stages. Frontiers in physiology 13 34276416
1999 Cloning, expression and characterization of an A6-related protein. European journal of biochemistry 9 10406962
2022 Oncogenic role of TWF2 in human tumors: A pan-cancer analysis. Open medicine (Warsaw, Poland) 4 36128444
2025 Actin-myosin complex dissociation initiates programmed cell death during cold storage of grass carp muscle. Food research international (Ottawa, Ont.) 2 40597474
2025 TWF2 Drives Tumor Progression and Sunitinib Resistance in Renal Cell Carcinoma through Hippo Signaling Suppression. Advanced science (Weinheim, Baden-Wurttemberg, Germany) 2 40948085
2024 Repurposing FDA approved drugs against monkeypox virus DNA dependent RNA polymerase: virtual screening, normal mode analysis and molecular dynamics simulation studies. Virusdisease 2 39071866
2025 Twinfilin is a potent uncapper of actin capping protein and modulates actomyosin contractility in the C. elegans spermatheca. bioRxiv : the preprint server for biology 0 40667244
2025 Multi-omics analysis reveals dynamic proteomic remodeling and metabonomic dysregulation underlying cytokine release syndrome in CAR-T-treated B-ALL. International immunopharmacology 0 41125014
2025 Development of high-efficiency hybrid strains for cellulolytic enzyme production via interspecific and intergeneric protoplast fusion of Trichoderma and Penicillium species. Enzyme and microbial technology 0 41145031
2025 Twinfilin modulates tissue contractility through uncapping of capping protein in C. elegans. Development (Cambridge, England) 0 41195540