Affinage

IFT25

Intraflagellar transport protein 25 homolog · UniProt Q9Y547

Round 2 corrected
Length
144 aa
Mass
16.3 kDa
Annotated
2026-04-28
39 papers in source corpus 11 papers cited in narrative 11 extracted findings

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

IFT25 is a phosphoprotein subunit of the intraflagellar transport complex B (IFT-B) peripheral subcomplex that forms a stable heterodimer with the Rab-like GTPase IFT27 and links to the IFT74–IFT81 dimer, thereby connecting peripheral and core IFT-B modules (PMID:19412537, PMID:26980730, PMID:34888642). Although dispensable for ciliogenesis in somatic cells, IFT25 is specifically required for signal-dependent trafficking of Hedgehog pathway components (Patched-1, Smoothened, Gli2) within cilia and for BBSome export from cilia, and its loss abolishes Hedgehog signaling and causes perinatal lethality in mice (PMID:22595669, PMID:28838966). IFT25 is essential for sperm flagella assembly and male fertility, stabilizing IFT27, IFT20, and IFT81 in the testis and maintaining the 9+2 axonemal architecture and lipid raft organization of sperm (PMID:28430876, PMID:28964737). Disruption of the IFT25–IFT27/IFT74–IFT81 interaction interface by Bardet–Biedl syndrome–associated variants of IFT27 (BBS19) or IFT74 (BBS22) causes defective ciliary membrane protein export, establishing this interaction as a molecular basis for Bardet–Biedl syndrome (PMID:34888642).

Mechanistic history

Synthesis pass · year-by-year structured walk · 8 steps
  1. 2009 High

    Identification of IFT25 as a novel IFT-B component that directly heterodimerizes with IFT27 established the existence of a previously unknown peripheral module of the IFT particle.

    Evidence FLAG-tagged co-immunoprecipitation with IFT-B subunits in mouse cells; in vitro binding, sucrose gradient co-sedimentation, and phosphorylation analysis in Chlamydomonas

    PMID:19253336 PMID:19412537

    Open questions at the time
    • Phosphorylation sites regulating IFT25 incorporation into IFT-B not mapped
    • Kinase responsible for IFT25 phosphorylation unidentified
    • Position of IFT25–IFT27 within the overall IFT-B architecture unknown
  2. 2012 High

    Demonstration that IFT25 is dispensable for ciliary assembly yet essential for Hedgehog signal transduction within cilia resolved why certain IFT-B subunits can be lost without ciliogenesis defects and revealed a cargo-specific IFT function.

    Evidence Ift25 null mice with intact cilia but failed Hedgehog-dependent trafficking of Patched-1, Smoothened, and Gli2

    PMID:22595669

    Open questions at the time
    • Mechanism by which IFT25 selectively facilitates Hedgehog cargo loading is unknown
    • Whether IFT25 directly contacts Hedgehog pathway components or acts indirectly through BBSome is unresolved
  3. 2016 High

    Systematic IFT-B interaction mapping placed the IFT25–IFT27 heterodimer as a defined peripheral module, clarifying the modular architecture of the 16-subunit IFT-B complex.

    Evidence Visible immunoprecipitation (VIP) assay mapping all pairwise IFT-B interactions

    PMID:26980730

    Open questions at the time
    • Atomic-resolution structure of IFT25–IFT27 within IFT-B not determined
    • How peripheral attachment is regulated during IFT cycling unknown
  4. 2017 High

    Parallel studies in Chlamydomonas and mice revealed that IFT25–IFT27 specifically controls BBSome export from cilia and is essential for sperm flagella formation and male fertility, expanding the functional repertoire beyond Hedgehog signaling.

    Evidence Live imaging of BBSome trafficking in IFT25-depleted Chlamydomonas; conditional Ift25 and Ift27 testis KO mice with TEM, immunoblotting, and lipid raft analysis

    PMID:28430876 PMID:28838966 PMID:28964737

    Open questions at the time
    • Molecular basis for IFT25-specific regulation of sperm lipid rafts (independent of IFT27) not defined
    • Whether BBSome export defects directly underlie the Hedgehog trafficking phenotype is untested
  5. 2018 Medium

    Renal phenotyping of Ift25 null mice revealed duplex kidneys and reduced branching morphogenesis without rapid cystogenesis, distinguishing IFT25/IFT27 from canonical IFT genes in kidney development.

    Evidence Ift25 null mouse renal histology at multiple developmental stages

    PMID:29626631

    Open questions at the time
    • Signaling pathway underlying the branching morphogenesis defect not molecularly dissected
    • Whether the kidney phenotype is Hedgehog- or Wnt-dependent is unknown
  6. 2019 High

    Demonstration that IFT25 undergoes bidirectional IFT and interacts with IFT27 within the flagellum of Trypanosoma brucei, where its depletion produces tiny disorganized flagella, established evolutionary conservation and revealed that IFT25 is essential for flagellum construction in protists—unlike in mammalian somatic cilia.

    Evidence BiFC-confirmed interaction during live IFT, RNAi depletion phenotype, electron microscopy in T. brucei

    PMID:30709917

    Open questions at the time
    • Basis for the organism-specific requirement for IFT25 in ciliogenesis (protist vs. mammal) is unexplained
    • Role of IFT25 phosphorylation in trypanosome flagellar assembly not explored
  7. 2022 High

    Mapping of the IFT25–IFT27/IFT74–IFT81 binding interface and functional testing of BBS patient variants proved that disruption of this specific interaction causes Bardet–Biedl syndrome, providing a direct molecular mechanism for disease.

    Evidence Co-immunoprecipitation of wild-type and BBS-variant IFT27 with IFT74–IFT81; IFT27-KO cell rescue assays with patient-derived variants

    PMID:34888642

    Open questions at the time
    • Structural basis of how BBS variants disrupt the interface at atomic resolution not determined
    • No IFT25-specific BBS-causing variant has been reported
  8. 2025 Medium

    Live imaging of endogenous IFT25-GFP in mouse spermatids demonstrated that IFT25 transitions from free diffusion to immobile punctae as spermatogenesis proceeds, revealing a stage-dependent shift in IFT dynamics during flagellogenesis.

    Evidence CRISPR/Cas9 IFT25-GFP knock-in mouse, FRAP, and kymography on isolated germ cells

    PMID:39561113

    Open questions at the time
    • Molecular basis for the transition from mobile to immobile IFT25 is unknown
    • Whether immobile IFT25 punctae represent structural incorporation into flagellar components or sequestered complexes is unresolved

Open questions

Synthesis pass · forward-looking unresolved questions
  • Key unresolved questions include the structural basis of IFT25–IFT27 within the intact IFT-B particle, the mechanism by which IFT25 selectively loads Hedgehog pathway cargo, the identity of IFT25 phosphorylation sites and their regulatory kinases, and why IFT25 is essential for flagellum construction in protists but dispensable for somatic ciliogenesis in mammals.
  • No high-resolution structure of IFT25 within the intact IFT-B particle
  • Mechanism of cargo selectivity for Hedgehog components unresolved
  • IFT25 phospho-regulatory circuit undefined

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0005198 structural molecule activity 4 GO:0060090 molecular adaptor activity 3
Localization
GO:0005929 cilium 6 GO:0005856 cytoskeleton 3
Pathway
R-HSA-1852241 Organelle biogenesis and maintenance 4 R-HSA-5653656 Vesicle-mediated transport 3 R-HSA-1266738 Developmental Biology 2 R-HSA-162582 Signal Transduction 2
Partners
IFT20IFT27IFT74IFT81IFT88
Complex memberships
IFT-B complexIFT25–IFT27 heterodimer

Evidence

Reading pass · 11 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2009 IFT25 (also known as Hspb11) was identified as a novel component of mouse IFT complex B; it localizes to cilia and the peri-basal body region, and co-immunoprecipitates with IFT88 along with other complex B subunits, indicating co-assembly into the IFT-B complex. Database analysis, FLAG-epitope tagging, immunoprecipitation, immunofluorescence localization Cell motility and the cytoskeleton High 19253336
2009 In Chlamydomonas, IFT25 is a phosphoprotein component of IFT complex B that directly binds IFT27 (a Rab-like GTPase) in vitro, co-localizes with IFT27 at the distal basal body/transition zone region, and co-sediments with IFT27 in 16S fractions in flagella. In the cell body, only the phosphorylated form of IFT25 is preferentially incorporated into complex B, suggesting that phosphorylation regulates IFT25 association with the complex. Dephosphorylation assay, in vitro binding assay, sucrose density gradient centrifugation, immunofluorescence co-localization PloS one High 19412537
2012 IFT25 is not required for ciliary assembly in mammals but is essential for Hedgehog signaling within cilia. Cilia lacking IFT25 fail to transport Hedgehog pathway components Patched-1, Smoothened, and Gli2 in a signal-dependent manner and cannot activate the pathway upon stimulation. IFT25 null mice die at birth with multiple Hedgehog signaling dysfunction phenotypes. Ift25 null mouse generation, immunofluorescence of ciliary Hedgehog components, genetic phenotypic analysis Developmental cell High 22595669
2016 IFT25 and IFT27 form a heterodimer that constitutes part of the peripheral subcomplex of IFT-B. Using the visible immunoprecipitation (VIP) assay, IFT25-IFT27 was mapped as a peripheral module of the IFT-B complex, distinct from the core subcomplex. Visible immunoprecipitation (VIP) assay, protein-protein interaction mapping of IFT-B subunits The Journal of biological chemistry High 26980730
2017 IFT25, although dispensable for ciliogenesis in somatic cells, is essential for sperm flagella formation and male fertility in mice. In Ift25 conditional knockout testes, IFT27 protein is absent and IFT20 and IFT81 levels are reduced, indicating IFT25 stabilizes these IFT-B partners in the testis. Sperm show disorganized fibrous sheath, outer dense fibers, and loss of the 9+2 axonemal structure, and sperm lipid rafts are disrupted. Conditional male germ cell-specific knockout, histology, TEM, immunoblotting of IFT proteins, light microscopy/SEM of sperm Biology of reproduction High 28430876
2017 In Chlamydomonas, IFT25 depletion does not affect entry of the BBSome into flagella or flagellar assembly, but impairs BBSome movement out of the flagellum, demonstrating that the IFT25-IFT27 module specifically controls BBSome export from cilia. IFT25 depletion also causes dramatic reduction of IFT27 protein levels. RNAi/amiRNA depletion of IFT25 in Chlamydomonas, live imaging of BBSome trafficking, immunofluorescence Biology open High 28838966
2017 IFT27 (the IFT25 binding partner) is essential for sperm flagella formation and male fertility in mice; conditional knockout of IFT27 in spermatocytes/spermatids reduces IFT25 and IFT81 levels but not IFT20, IFT74, or IFT140, and unlike Ift25 knockout, sperm lipid rafts remain normal — indicating IFT25 has additional roles beyond IFT27 in sperm. Conditional Ift27 knockout (Stra8-iCre), immunoblotting, TEM, SEM, lipid raft analysis Developmental biology High 28964737
2018 IFT25 and IFT27 are required for early kidney development: Ift25 null mice develop duplex kidneys (from defective ureteric bud formation) and show reduced renal branching morphogenesis, but do not develop the rapid cyst growth seen in most IFT gene deletions, distinguishing IFT25/IFT27 from canonical IFT proteins in the kidney. Ift25 null mouse analysis, histology, renal morphological assessment at multiple developmental time points Mechanisms of development Medium 29626631
2019 In Trypanosoma brucei, IFT25 is a bona fide IFT-B component that undergoes typical bidirectional IFT trafficking. IFT25 and IFT27 interact within the flagellum during live IFT (shown by bimolecular fluorescence complementation). IFT25 depletion causes accumulation of IFT-B proteins (but not IFT27 or IFT-A proteins) and produces tiny disorganized flagella, phenocopying IFT27 depletion, establishing IFT25-IFT27 as a specific IFT-B module required for proper IFT and flagellum construction in trypanosomes. RNAi depletion, bimolecular fluorescence complementation (BiFC) in live cells, immunofluorescence, electron microscopy Journal of cell science High 30709917
2022 The IFT25-IFT27 heterodimer directly binds the C-terminal region of the IFT74-IFT81 heterodimer within the IFT-B complex. BBS-causing missense variants of IFT27 (BBS19) are specifically impaired in binding IFT74-IFT81, and the BBS variants of IFT74 (BBS22) delete the IFT25-IFT27-binding region. BBS variants of IFT27 cannot rescue BBS-like ciliary phenotypes (abnormal membrane protein export) in IFT27-KO cells, establishing that impaired IFT25-IFT27/IFT74-IFT81 interaction causes Bardet-Biedl syndrome-associated ciliary defects. Co-immunoprecipitation, IFT27-KO cell rescue assays, analysis of BBS patient variants, ciliary phenotype assays Human molecular genetics High 34888642
2025 IFT25 protein traffics bidirectionally along developing sperm flagella with no preferential directionality, but its mobility changes with developmental stage: from highly mobile unrestricted diffusion in early spermatids, to mobile punctate structures in developing sperm, to immobile punctate structures in mature sperm. IFT25-GFP is highly abundant only in the testis, consistent with endogenous IFT25 expression. CRISPR/Cas9 IFT25-GFP knock-in mouse, FRAP, kymograph analysis, live imaging in isolated germ cells Biology of reproduction Medium 39561113

Source papers

Stage 0 corpus · 39 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2005 Towards a proteome-scale map of the human protein-protein interaction network. Nature 2090 16189514
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
2014 A proteome-scale map of the human interactome network. Cell 977 25416956
2020 A reference map of the human binary protein interactome. Nature 849 32296183
2021 Dual proteome-scale networks reveal cell-specific remodeling of the human interactome. Cell 705 33961781
2011 Phylogenetic-based propagation of functional annotations within the Gene Ontology consortium. Briefings in bioinformatics 656 21873635
1994 Oligo-capping: a simple method to replace the cap structure of eukaryotic mRNAs with oligoribonucleotides. Gene 492 8125298
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
2005 Diversification of transcriptional modulation: large-scale identification and characterization of putative alternative promoters of human genes. Genome research 409 16344560
2007 hORFeome v3.1: a resource of human open reading frames representing over 10,000 human genes. Genomics 222 17207965
2016 An organelle-specific protein landscape identifies novel diseases and molecular mechanisms. Nature communications 211 27173435
2011 Next-generation sequencing to generate interactome datasets. Nature methods 200 21516116
2012 IFT25 links the signal-dependent movement of Hedgehog components to intraflagellar transport. Developmental cell 183 22595669
1994 Isolation of novel and known genes from a human fetal cochlear cDNA library using subtractive hybridization and differential screening. Genomics 163 7829101
2000 Cloning and functional analysis of cDNAs with open reading frames for 300 previously undefined genes expressed in CD34+ hematopoietic stem/progenitor cells. Genome research 161 11042152
2009 Characterization of mouse IFT complex B. Cell motility and the cytoskeleton 129 19253336
2013 Proteomic analysis of podocyte exosome-enriched fraction from normal human urine. Journal of proteomics 126 23376485
2016 Overall Architecture of the Intraflagellar Transport (IFT)-B Complex Containing Cluap1/IFT38 as an Essential Component of the IFT-B Peripheral Subcomplex. The Journal of biological chemistry 100 26980730
2015 Quantitative interaction proteomics of neurodegenerative disease proteins. Cell reports 86 25959826
2015 Systematic proteomics of the VCP-UBXD adaptor network identifies a role for UBXN10 in regulating ciliogenesis. Nature cell biology 81 26389662
2009 Intraflagellar transport (IFT) protein IFT25 is a phosphoprotein component of IFT complex B and physically interacts with IFT27 in Chlamydomonas. PloS one 79 19412537
2017 Intraflagellar transporter protein (IFT27), an IFT25 binding partner, is essential for male fertility and spermiogenesis in mice. Developmental biology 68 28964737
2022 Scalable multiplex co-fractionation/mass spectrometry platform for accelerated protein interactome discovery. Nature communications 65 35831314
2019 Extensive disruption of protein interactions by genetic variants across the allele frequency spectrum in human populations. Nature communications 60 31515488
2017 IFT25, an intraflagellar transporter protein dispensable for ciliogenesis in somatic cells, is essential for sperm flagella formation. Biology of reproduction 58 28430876
2007 Preventing apoptotic cell death by a novel small heat shock protein. European journal of cell biology 43 17275951
2022 Impaired cooperation between IFT74/BBS22-IFT81 and IFT25-IFT27/BBS19 causes Bardet-Biedl syndrome. Human molecular genetics 31 34888642
2015 Small heat shock proteins are induced during multiple sclerosis lesion development in white but not grey matter. Acta neuropathologica communications 29 26694816
2020 SUMOylation of DDX39A Alters Binding and Export of Antiviral Transcripts to Control Innate Immunity. Journal of immunology (Baltimore, Md. : 1950) 27 32393512
2023 TRIM67 drives tumorigenesis in oligodendrogliomas through Rho GTPase-dependent membrane blebbing. Neuro-oncology 25 36215168
2023 O-GlcNAcylation of SPOP promotes carcinogenesis in hepatocellular carcinoma. Oncogene 23 36604567
2017 Chlamydomonas IFT25 is dispensable for flagellar assembly but required to export the BBSome from flagella. Biology open 22 28838966
2015 Association between small heat shock protein B11 and the prognostic value of MGMT promoter methylation in patients with high-grade glioma. Journal of neurosurgery 22 26544773
2018 CRISPR/Cas9-mediated Genomic Editing of Cluap1/IFT38 Reveals a New Role in Actin Arrangement. Molecular & cellular proteomics : MCP 20 29615496
2007 Correlation between the progressive cytoplasmic expression of a novel small heat shock protein (Hsp16.2) and malignancy in brain tumors. BMC cancer 18 18154656
2018 Ift25 is not a cystic kidney disease gene but is required for early steps of kidney development. Mechanisms of development 10 29626631
2019 IFT25 is required for the construction of the trypanosome flagellum. Journal of cell science 9 30709917
2025 Two-directional trafficking of the IFT25 protein in the developing mouse sperm flagella. Biology of reproduction 1 39561113