Affinage

INTU

Protein inturned · UniProt Q9ULD6

Length
942 aa
Mass
105.6 kDa
Annotated
2026-06-10
36 papers in source corpus 14 papers cited in narrative 14 extracted findings
Cross-family judge vs UniProt: Affinage preferred faithfulness: 7/7 claims corpus-supported (100%)

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

INTU (Inturned) is an essential regulator of primary ciliogenesis and cilia-dependent Hedgehog signal transduction during embryonic development, tissue homeostasis, and injury repair (PMID:20067783, PMID:22935613). It functions as a core subunit of the CPLANE complex together with FUZ and WDPCP, acting downstream of core planar cell polarity but upstream of cilia-dependent Hedgehog patterning (PMID:21761479, PMID:35740972). At the mother centriole/basal body, INTU is required for assembly of the IFT-A intraflagellar transport complex, and it controls the recruitment of the small GTPase RSG1 — together with TTBK2 — to drive axonemal microtubule elongation at the final maturation step of cilia initiation (PMID:28459465, PMID:29038301). Genetically, INTU acts downstream of Smoothened and upstream of Gli2 activation: constitutively active Gli2 restores Hedgehog signaling in INTU-deficient cells, and combined loss of Gli2 and Intu abolishes Hedgehog-dependent morphogenesis (PMID:28459465, PMID:39029571). Loss of Intu disrupts ciliogenesis and Hedgehog output across diverse tissues, including epidermis and hair follicles, skeleton, lung branching morphogenesis, and renal tubule repair, where INTU additionally binds STAT1 at the centriole and promotes its proteasomal degradation (PMID:22935613, PMID:25774014, PMID:29581513, PMID:39029571). Structurally, INTU contains a PDZ-like fold that lacks a canonical PDZ-ligand binding site and does not interact with membranes or Vangl2 (PMID:41797376). Compound heterozygous INTU variants cause human disease through disruption of CPLANE-dependent ciliogenesis (PMID:40968537).

Mechanistic history

Synthesis pass · year-by-year structured walk · 14 steps
  1. 2009 Medium

    Established that the PCP effector module to which Intu belongs operates at the interface of vesicle trafficking and ciliogenesis, before Intu itself was biochemically dissected.

    Evidence Fuz mutant mouse analysis, in vivo mucociliary imaging, and co-IP identifying a Rab-related GTPase partner

    PMID:19767740

    Open questions at the time
    • Focused on Fuz, not direct Intu biochemistry
    • Did not define the molecular trafficking step controlled
  2. 2010 High

    Defined INTU as an essential ciliogenesis regulator and placed it within Hedgehog signal transduction by linking its loss to failed Gli3 processing and reduced Hh target genes.

    Evidence Intu null mouse with cilia immunofluorescence, Hh target qRT-PCR/Western, and GFP-Intu rescue in fibroblasts

    PMID:20067783

    Open questions at the time
    • Molecular mechanism of how INTU promotes ciliogenesis unknown
    • No biochemical activity defined
  3. 2011 Medium

    Positioned Intu and Fuz as non-redundant effectors downstream of core PCP but upstream of cilia-dependent Hh patterning, separating their ciliogenic role from convergent-extension PCP.

    Evidence Intu;Fuz double mutant mouse epistasis and genetic tests with a Vangl2 hypomorph

    PMID:21761479

    Open questions at the time
    • Does not establish a molecular function
    • Single-lab genetic study
  4. 2012 High

    Demonstrated that INTU's role is cell-fate-specific and cilia-dependent rather than tied to epidermal barrier or PCP, by restricting its requirement to follicular keratinocyte differentiation.

    Evidence Conditional epidermal Cre-lox knockout with cilia markers, Hh reporter, and differentiation/barrier assays

    PMID:22935613

    Open questions at the time
    • Does not identify INTU molecular partners in skin
    • Mechanism of cilia loss not resolved biochemically
  5. 2015 High

    Linked a specific conserved C-terminal residue (I813) to ciliogenic activity, showing domain-level structure-function and tissue selectivity (skeletal versus neural tube).

    Evidence I813N hypomorphic knock-in mouse with cilia, skeletal, and Hh-target readouts plus rescue assay in Intu null cells

    PMID:25774014

    Open questions at the time
    • Biochemical consequence of I813N not defined
    • Why neural tube is spared unexplained
  6. 2017 High

    Provided the molecular and epistatic placement of INTU: required for IFT-A complex assembly and acting downstream of Smo but upstream of Gli2 activation.

    Evidence Conditional KO in SmoM2 BCC model, IFT-A assembly assays, and Gli2ΔN epistasis rescue in MEFs

    PMID:28459465

    Open questions at the time
    • Direct biochemical mechanism of IFT-A assembly by INTU not shown
    • How INTU couples to Gli2 regulation unresolved
  7. 2017 High

    Identified a downstream effector arm, showing INTU is required to recruit RSG1 to the mother centriole for axonemal elongation at a final cilia-initiation step.

    Evidence Rsg1 KO mouse, RSG1 centriolar localization dependent on Intu/TTBK2/GTPase activity, and cilia ultrastructure

    PMID:29038301

    Open questions at the time
    • Whether INTU directly binds RSG1 not established
    • Mechanism of RSG1-driven microtubule elongation unknown
  8. 2018 High

    Revealed a non-ciliary biochemical activity: INTU binds STAT1 at the basal body and promotes its proteasomal degradation, protecting cilia length and viability under stress.

    Evidence Co-IP, reciprocal co-localization, proteasome inhibitor assay, and proximal-tubule conditional KO with ischemia-reperfusion phenotype

    PMID:29581513

    Open questions at the time
    • Mechanism by which INTU targets STAT1 for degradation unknown
    • No identified E3 ligase or degron
  9. 2020 Low

    Generated a structural hypothesis that the INTU/FUZ heterodimer carries triplicated Longin domains homologous to Rab effector/GEF complexes, predicting Rab GEF activity in ciliogenesis.

    Evidence Coevolution-based contact prediction and sequence conservation analysis (computational only)

    PMID:31562761

    Open questions at the time
    • No experimental validation of GEF activity
    • Predicted Rab substrate not identified
  10. 2022 Medium

    Consolidated INTU as a stable CPLANE subunit (with FUZ, WDPCP, JBTS17, RSG1) whose dysfunction causes ciliopathies, integrating its IFT-A and signaling roles.

    Evidence Synthesis of genetic and functional studies including IFT-A assembly and mouse models

    PMID:35740972

    Open questions at the time
    • Review-level synthesis, not new primary data
    • Stoichiometry and architecture of CPLANE not resolved here
  11. 2022 Medium

    Extended INTU's tissue role to centrosome-directed cell migration during kidney repair, distinguishing its repair-promoting from fibrosis-modulating effects.

    Evidence Kidney-tubule conditional KO with fibrosis/senescence analysis and scratch-wound assay with centrosome orientation imaging

    PMID:36586478

    Open questions at the time
    • Molecular basis of centrosome orientation defect unclear
    • Relationship to STAT1 degradation arm not tested
  12. 2024 High

    Confirmed the upstream-of-Gli2 placement in a new organ context by showing Intu is required for Hh-driven lung branching morphogenesis.

    Evidence Intu null mouse, lung explant Smo-agonist rescue, Gli2;Intu double-mutant epistasis, and transcriptomics

    PMID:39029571

    Open questions at the time
    • Does not add new biochemical mechanism
    • Cell-type-specific contributions not fully separated
  13. 2025 High

    Resolved the structure of INTU's PDZ-like domain, overturning the assumption of canonical PDZ-ligand or Vangl2 binding and reassigning Vangl2's PDZ interaction to Scribble.

    Evidence Crystal structure of the Intu-PDZ domain plus pulldown/binding assays with membranes and Vangl2

    PMID:41797376

    Open questions at the time
    • The actual binding partner(s) of the INTU PDZ-like fold remain unidentified
    • Functional role of this domain in ciliogenesis not defined
  14. 2025 Medium

    Established INTU as a human disease gene by showing pathogenic compound heterozygous variants disrupt CPLANE-dependent ciliogenesis in patient cells.

    Evidence Patient-derived cell ciliogenesis assays and trio whole-exome sequencing

    PMID:40968537

    Open questions at the time
    • Single case with limited mechanistic depth
    • Genotype-phenotype correlation not generalized

Open questions

Synthesis pass · forward-looking unresolved questions
  • Whether the INTU/FUZ Longin-domain module possesses experimentally validated Rab GEF activity, and which Rab(s) and what binding partner of the PDZ-like fold mediate INTU's ciliogenic and IFT-A assembly functions, remains unresolved.
  • Predicted GEF activity never tested biochemically
  • No identified ligand for the PDZ-like domain
  • Direct molecular mechanism of IFT-A assembly by INTU unknown

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0140096 catalytic activity, acting on a protein 1
Localization
GO:0005815 microtubule organizing center 2 GO:0005929 cilium 2 GO:0005829 cytosol 1
Pathway
R-HSA-1266738 Developmental Biology 3 R-HSA-1852241 Organelle biogenesis and maintenance 3
Complex memberships
CPLANE complex

Evidence

Reading pass · 14 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2010 Mouse Intu null mutants exhibit severe ciliogenesis defects (loss of primary cilia in embryos and cultured fibroblasts), disrupted Gli3 proteolytic processing, and downregulated Hh target genes Gli1 and Ptch1, establishing Intu as an essential regulator of ciliogenesis and Hedgehog signal transduction. A cytoplasmic GFP-Intu fusion protein efficiently rescues ciliogenic defects in Intu mutant cells. Gene-targeted null mutation in mice, immunofluorescence for cilia, qRT-PCR and Western blot for Hh pathway components, rescue with GFP-Intu in cultured fibroblasts Developmental biology High 20067783
2009 Fuz (a PCP effector functionally linked to Intu in the same pathway) is essential for trafficking of cargo to basal bodies and to apical cilia tips, and for exocytosis in secretory cells; a Rab-related small GTPase was identified as a Fuz interaction partner also required for ciliogenesis and secretion, placing the PCP effector module at the interface of vesicle trafficking and ciliogenesis. Fuz mutant mouse analysis, in vivo mucociliary epithelium imaging, bioinformatics, co-immunoprecipitation/interaction with Rab GTPase Nature cell biology Medium 19767740
2011 The ciliogenesis-dependent neural tube patterning functions of Intu and Fuz are non-redundant; genetic removal of both genes does not produce a convergent-extension phenotype, and neither gene shows genetic interaction with the core PCP regulator Vangl2 in convergent extension. Intu and Fuz double mutants show more severe patterning defects without redundancy, positioning these effectors downstream of core PCP but upstream of cilia-dependent Hh patterning. Intu;Fuz double mutant mouse analysis, genetic epistasis with Vangl2 hypomorph, histological and molecular patterning assays Developmental dynamics Medium 21761479
2012 Tissue-specific disruption of Intu in embryonic epidermis causes near-complete loss of primary cilia in epidermal and follicular keratinocytes, suppresses Hedgehog signaling, and arrests hair follicle morphogenesis due to failure of follicular keratinocyte differentiation, without affecting epidermal stratification, barrier function, or planar cell polarity—demonstrating a cell-fate-specific, cilia-dependent role for Intu in skin. Conditional knockout (Cre-lox) in mouse epidermis, immunofluorescence for cilia markers, Hh pathway reporter analysis, histological differentiation assays Cell death and differentiation High 22935613
2015 A hypomorphic Intu allele carrying a conserved hydrophobic-to-asparagine substitution (I813N) near the C-terminus causes moderate cilia loss, skeletal defects (rib defects, delayed endochondral ossification, polydactyly), and reduced Hh signaling, while neural tube patterning and PCP appear normal. The Intu(I813N) protein exhibits compromised ability to restore ciliogenesis in Intu null cells, functionally linking this residue to ciliogenic activity. Gene-targeted hypomorphic knock-in mouse (I813N), cilia quantification, skeletal staining, qRT-PCR for Hh targets, rescue assay in Intu null cultured cells Developmental dynamics High 25774014
2017 INTU is essential for IFT-A (intraflagellar transport A) complex assembly during ciliogenesis. In an oncogenic SmoM2-driven basal cell carcinoma model, Intu disruption prevents BCC formation by suppressing primary cilia formation and Hh signaling. In mouse embryonic fibroblasts, depleting Intu blocks Smo agonist-induced Hh pathway activation, but expression of constitutively active Gli2ΔN restores Hh signaling in Intu-deficient cells, genetically placing INTU upstream of Gli2 activation and downstream of Smo. Conditional knockout in SmoM2 BCC mouse model, shRNA knockdown, cilia quantification, IFT-A complex assembly assays, epistasis with Gli2ΔN in MEFs Oncogene High 28459465
2017 RSG1 (a small GTPase) localizes to the mother centriole in a process that depends on INTU (the CPLANE protein Inturned), tau tubulin kinase 2 (TTBK2), and RSG1's own GTPase activity. Loss of RSG1 impairs axonemal microtubule elongation after ciliary vesicle docking, placing RSG1 as a downstream effector of INTU at a final maturation step of cilia initiation. Rsg1 mouse knockout, immunofluorescence for RSG1 centriolar localization, genetic epistasis with Intu and TTBK2, cilia ultrastructure analysis, Hh pathway readouts The Journal of cell biology High 29038301
2018 INTU physically interacts with STAT1; they co-localize at the centriole/basal body. INTU promotes proteasomal degradation of STAT1. In vitro, INTU expression preserves cilia length and cell viability after stress, effects antagonized by STAT1 overexpression. Kidney-proximal-tubule-specific ablation of Intu aggravates renal ischemia-reperfusion injury and impairs post-injury ciliogenesis. Co-immunoprecipitation, co-localization by immunofluorescence, conditional KO mouse (proximal tubule-specific), proteasome inhibitor assay, cell viability assays Nature communications High 29581513
2020 Computational evolutionary analysis identifies INTU and FUZ as a heterodimeric complex homologous to HerMon (Hermansky-Pudlak syndrome and MON1-CCZ1) complexes, each containing triplicated Longin domains. Based on homology to known Rab effectors/GEFs, the INTU/FUZ complex is predicted to act as a GEF for Rab GTPases involved in ciliogenesis. Coevolution-based contact prediction, sequence conservation analysis (computational/bioinformatic) Bioinformatics Low 31562761
2022 CPLANE complex (composed of INTU, FUZ, and WDPCP, which interact with JBTS17 and RSG1) is required for IFT-A particle assembly and intraflagellar transport; defects in CPLANE components disrupt PCP and Hh signaling, leading to ciliopathies including orofacial-digital syndrome and Bardet-Biedl syndrome. Synthesis/review of genetic and functional studies; functional studies cited include IFT-A assembly assays and mouse genetic models Biomolecules Medium 35740972
2022 Conditional knockout of Intu in kidney tubules delays kidney repair and ameliorates renal fibrosis after ischemia-reperfusion injury. Intu KO kidneys show less senescence but higher cell proliferation and apoptosis during repair. In vitro, Intu knockdown suppresses scratch wound healing in renal tubular cells, accompanied by abnormal centrosome orientation, establishing a role for Intu in centrosome-directed tubular cell migration/repair. Conditional KO mouse (kidney tubule-specific), histological and biochemical analysis of fibrosis and senescence, scratch wound healing assay with centrosome orientation imaging The American journal of pathology Medium 36586478
2024 Loss of Intu severely disrupts growth and branching morphogenesis of mouse embryonic lungs, associated with greatly reduced primary cilia in epithelial and mesenchymal cells and reduced Hh target gene expression (Gli1, Ptch1). Smoothened agonist increases Hh target gene expression and tubulogenesis in wild-type but not Intu mutant lung explants. Removing both Gli2 and Intu completely abolishes lung branching morphogenesis, genetically placing Intu upstream of Gli2-dependent Hh signaling in the lung. Intu null mouse KO, lung explant culture with Smo agonist, Gli2;Intu double mutant epistasis, qRT-PCR/immunofluorescence, transcriptomics Developmental biology High 39029571
2025 The predicted PDZ domain unique to Inturned among TLD proteins does not interact with membranes or with Vangl2. Crystal structure of the Intu-PDZ domain reveals a unique PDZ-like fold lacking a canonical interaction site for PDZ-binding motifs. Vangl2 instead shows a phosphorylation-dependent interaction with a PDZ domain of the apical-basal polarity protein Scribble. Crystal structure determination of Intu-PDZ domain, biochemical binding assays (pulldown/binding experiments with membranes and Vangl2), structural analysis FEBS letters High 41797376
2025 Functional studies in patient-derived cells with compound heterozygous INTU variants demonstrate altered ciliogenesis and/or cilia signaling, confirming that pathogenic INTU variants cause human disease through disruption of CPLANE-dependent ciliogenesis. Patient-derived cell ciliogenesis assays (compound heterozygous INTU variants), trio whole-exome sequencing HGG advances Medium 40968537

Source papers

Stage 0 corpus · 36 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2009 The planar cell polarity effector Fuz is essential for targeted membrane trafficking, ciliogenesis and mouse embryonic development. Nature cell biology 195 19767740
2017 Fifteen years of research on oral-facial-digital syndromes: from 1 to 16 causal genes. Journal of medical genetics 87 28289185
2010 PCP effector gene Inturned is an important regulator of cilia formation and embryonic development in mammals. Developmental biology 85 20067783
2019 Genome-Wide Homozygosity Patterns and Evidence for Selection in a Set of European and Near Eastern Horse Breeds. Genes 45 31261764
2019 Integrated miRNA and mRNA expression profiling identifies novel targets and pathological mechanisms in autoimmune thyroid diseases. EBioMedicine 38 31735554
2017 Single step genome-wide association studies based on genotyping by sequence data reveals novel loci for the litter traits of domestic pigs. Genomics 36 28943389
2011 PCP effector proteins inturned and fuzzy play nonredundant roles in the patterning but not convergent extension of mammalian neural tube. Developmental dynamics : an official publication of the American Association of Anatomists 30 21761479
1980 Hemocyte responses to implanted tissues inDrosophila melanogaster larvae. Wilhelm Roux's archives of developmental biology 30 28305176
2017 The small GTPase RSG1 controls a final step in primary cilia initiation. The Journal of cell biology 29 29038301
2018 The CPLANE protein Intu protects kidneys from ischemia-reperfusion injury by targeting STAT1 for degradation. Nature communications 22 29581513
2018 Chemotherapy-induced peripheral neuropathy: evidence from genome-wide association studies and replication within multiple myeloma patients. BMC cancer 22 30111286
2017 INTU is essential for oncogenic Hh signaling through regulating primary cilia formation in basal cell carcinoma. Oncogene 21 28459465
2012 Planar cell polarity effector gene Intu regulates cell fate-specific differentiation of keratinocytes through the primary cilia. Cell death and differentiation 21 22935613
2015 A hypomorphic allele reveals an important role of inturned in mouse skeletal development. Developmental dynamics : an official publication of the American Association of Anatomists 18 25774014
2022 CPLANE Complex and Ciliopathies. Biomolecules 15 35740972
2020 Hexa-Longin domain scaffolds for inter-Rab signalling. Bioinformatics (Oxford, England) 13 31562761
2022 Multi-Omics Characterization of Early- and Adult-Onset Major Depressive Disorder. Journal of personalized medicine 12 35330412
2022 Identical IFT140 Variants Cause Variable Skeletal Ciliopathy Phenotypes-Challenges for the Accurate Diagnosis. Frontiers in genetics 10 35873489
2022 Estimation of genetic parameters and single-step genome-wide association studies for milk urea nitrogen in Holstein cattle. Journal of dairy science 10 36460511
2018 INTU-related oral-facial-digital syndrome type VI: A confirmatory report. Clinical genetics 10 29451301
2019 A new case of KIAA0753-related variant of Jeune asphyxiating thoracic dystrophy. European journal of medical genetics 7 31816441
2021 Integration of genome-wide association study and expression quantitative trait locus mapping for identification of endometriosis-associated genes. Scientific reports 6 33436679
2021 INTU-related oral-facial-digital syndrome XVII: Clinical spectrum of a rare disorder. American journal of medical genetics. Part A 6 34623732
2024 The CPLANE protein Fuzzy regulates ciliogenesis by suppressing actin polymerization at the base of the primary cilium via p190A RhoGAP. Development (Cambridge, England) 5 38546045
2023 Combined genome-wide association study of 136 quantitative ear morphology traits in multiple populations reveal 8 novel loci. PLoS genetics 5 37459304
2023 Molecular investigation in individuals with orofacial clefts and microphthalmia-anophthalmia-coloboma spectrum. European journal of human genetics : EJHG 5 37932364
2021 Exploring the genomic resources of seven domestic Bactrian camel populations in China through restriction site-associated DNA sequencing. PloS one 4 33914766
2024 CPLANE protein INTU regulates growth and patterning of the mouse lungs through cilia-dependent Hh signaling. Developmental biology 3 39029571
2022 Multifaceted investigation underlies diverse mechanisms contributing to the downregulation of Hedgehog pathway-associated genes INTU and IFT88 in lung adenocarcinoma and uterine corpus endometrial carcinoma. Aging 3 36084949
2022 Deficiency of the Planar Cell Polarity Protein Intu Delays Kidney Repair and Suppresses Renal Fibrosis after Acute Kidney Injury. The American journal of pathology 3 36586478
2023 Gene and pathway based burden analyses in familial lymphoid cancer cases: Rare variants in immune pathway genes. PloS one 2 37379307
2023 Reanalysis of Whole-Exome Sequencing Data of an Infant with Suspected Diagnosis of Jeune Syndrome Revealed a Likely Pathogenic Variant in GRK2: A Newly Associated Gene for Jeune Syndrome Phenotype. Molecular syndromology 2 38585547
2026 The planar cell polarity protein Vangl2 interacts with the PDZ-domains of Scribble but not with a unique PDZ-like domain in Inturned. FEBS letters 0 41797376
2026 Rebuilding the Mucociliary Apparatus in ECRS: TSLP/IL-33 Signaling Synergy and the Residual Molecular Scar of DNASE1L3 Following IL-4/13 Blockade. Cells 0 42193919
2025 Wnt5a regulates the expression of developmental genes in the adult retina following optic nerve crush injury. Histology and histopathology 0 40079114
2025 Bi-allelic INTU variants define a ciliopathy disorder characterized by orofacial, digital, and cardiac anomalies. HGG advances 0 40968537

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