Affinage

TBC1D20

TBC1 domain family member 20 · UniProt Q96BZ9

Length
403 aa
Mass
45.9 kDa
Annotated
2026-04-28
11 papers in source corpus 10 papers cited in narrative 12 extracted findings

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

TBC1D20 is a TBC-domain Rab GTPase-activating protein that inactivates Rab1, Rab2, and Rab11 to coordinate ER-to-Golgi vesicle trafficking, lipid droplet homeostasis, autophagosome maturation, and ciliogenesis. As a Rab1/Rab2 GAP, TBC1D20 localizes to the ER and Golgi and controls anterograde secretory transport; its loss causes enlarged Golgi morphology, aberrant lipid droplet formation, impaired autophagic flux, and defective acrosome biogenesis in spermatids (PMID:17901050, PMID:24239381, PMID:27487390). TBC1D20 also functions as a Rab11 GAP whose activity suppresses Rab11-MICAL1–mediated centrosomal F-actin depolymerization, thereby gating vesicle docking and cilia assembly (PMID:39868814). Loss-of-function mutations in TBC1D20 cause Warburg Micro syndrome, characterized by ocular, neurological, and reproductive abnormalities linked to shared lipid droplet and trafficking defects with RAB18 and RAB3GAP1 deficiency (PMID:24239381).

Mechanistic history

Synthesis pass · year-by-year structured walk · 9 steps
  1. 2007 High

    Identification of TBC1D20 as a Rab1 GAP resolved the unknown identity of the GAP controlling ER-to-Golgi transport, establishing TBC1D20's core enzymatic activity and pathway placement.

    Evidence In vitro GTPase activation assay with catalytic-site mutagenesis and VSV-G transport blockade upon overexpression

    PMID:17901050

    Open questions at the time
    • Rab substrate specificity beyond Rab1 not tested
    • endogenous regulation of TBC1D20 activity unknown
    • no in vivo loss-of-function model
  2. 2007 High

    Discovery that HCV NS5A physically co-opts TBC1D20 showed how a virus hijacks host Rab1 regulation for membrane-associated RNA replication, revealing TBC1D20 as a host factor for viral life cycles.

    Evidence Protein interaction studies and siRNA-mediated Rab1 depletion with HCV RNA measurement

    PMID:17901050

    Open questions at the time
    • Structural basis of NS5A–TBC1D20 interaction undetermined
    • whether other viruses exploit TBC1D20 unknown
  3. 2012 High

    Localization of the NS5A–TBC1D20–Rab1 axis to lipid droplets established that TBC1D20 operates at LD-associated membranes, linking its GAP activity to lipid droplet biology and viral replication compartments.

    Evidence Live-cell FRAP imaging, dominant-negative Rab1 expression, and HCV-infected cell immunofluorescence

    PMID:22491470

    Open questions at the time
    • Whether TBC1D20 regulates LDs independently of viral infection not resolved
    • mechanism of TBC1D20 recruitment to LDs unclear
  4. 2013 High

    Genetic identification of TBC1D20 loss-of-function in Warburg Micro syndrome, together with demonstration of Rab2 GAP activity and convergent LD defects with RAB18/RAB3GAP1 loss, placed TBC1D20 in a shared disease pathway controlling lipid droplet and Golgi homeostasis.

    Evidence Positional cloning, in vitro GAP assay for Rab1 and Rab2, LD and Golgi morphology analysis in MEFs and patient fibroblasts

    PMID:24239381

    Open questions at the time
    • Functional relationship between TBC1D20 and RAB18 at the mechanistic level not defined
    • neurological disease mechanism not addressed at the cellular level
  5. 2014 Medium

    Engineered TBC domain disruption confirmed that the catalytic domain is essential for in vivo function, validating that cataract and acrosomal phenotypes require intact GAP activity.

    Evidence Zinc-finger nuclease-mediated in-frame deletion with allelic complementation test and histology in mouse

    PMID:25476608

    Open questions at the time
    • Whether partial TBC domain function is retained not assessed
    • structural consequence of in-frame deletion not resolved
  6. 2016 High

    Demonstration that TBC1D20 controls autophagosome maturation via Rab1B GAP activity expanded its functional repertoire beyond secretory trafficking to autophagy, explaining lens and testicular pathology.

    Evidence TBC1D20-null mouse autophagic flux assays, autophagosome marker colocalization, and multi-tissue histology

    PMID:27487390

    Open questions at the time
    • Molecular mechanism of autophagosome-lysosome fusion regulation by Rab1B unclear
    • whether autophagy defects underlie neurological WARBM phenotypes untested
  7. 2019 Medium

    Linking TBC1D20 deficiency to ER stress-induced apoptosis in Sertoli cells revealed a cell-type-specific consequence of disrupted ER-Golgi morphology, providing a cellular mechanism for the male infertility phenotype.

    Evidence Subcellular fractionation, ER stress marker and caspase-12 western blotting, cell cycle analysis in bs mouse Sertoli cells

    PMID:31633178

    Open questions at the time
    • Whether ER stress is a direct consequence of Rab1 hyperactivation or a secondary effect not distinguished
    • relevance to human Sertoli cells not tested
  8. 2020 Medium

    Identification of blood-testis barrier disruption and junction protein downregulation upon TBC1D20 loss connected its trafficking role to cell polarity and intercellular adhesion in Sertoli cells.

    Evidence Biotin tracer permeability assay, electron microscopy, junction protein immunofluorescence, F-actin staining

    PMID:31994000

    Open questions at the time
    • Whether junction defects are Rab1- or Rab2-dependent not determined
    • in vivo BTB phenotype not confirmed
  9. 2025 High

    Discovery of TBC1D20 as a Rab11 GAP that controls centrosomal F-actin remodeling via the Rab11–MICAL1 axis revealed a previously unknown function in ciliogenesis initiation, explaining cilium-related features of Warburg Micro syndrome.

    Evidence TBC1D20 depletion with Rab11 activity assays, Rab11–MICAL1 co-immunoprecipitation, ciliogenesis assays, F-actin imaging, and MICAL1 monooxygenase functional analysis

    PMID:39868814

    Open questions at the time
    • Whether Rab11 GAP activity is regulated independently of Rab1 GAP activity unknown
    • in vivo ciliogenesis defects in TBC1D20 knockout not yet shown
    • structural basis for dual Rab specificity not resolved

Open questions

Synthesis pass · forward-looking unresolved questions
  • How TBC1D20's dual Rab1 and Rab11 GAP activities are spatiotemporally coordinated, and which specific Rab substrate(s) underlie the neurological manifestations of Warburg Micro syndrome, remain unresolved.
  • No structural model of TBC1D20
  • mechanism of TBC1D20 recruitment to distinct membrane compartments unknown
  • neuronal cell-type-specific functions not characterized

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0003924 GTPase activity 5 GO:0098772 molecular function regulator activity 4
Localization
GO:0005794 Golgi apparatus 2 GO:0005783 endoplasmic reticulum 1 GO:0005811 lipid droplet 1
Pathway
R-HSA-1643685 Disease 3 R-HSA-5653656 Vesicle-mediated transport 3 R-HSA-1852241 Organelle biogenesis and maintenance 1 R-HSA-9612973 Autophagy 1
Partners
MICAL1NS5ARAB1RAB11RAB2

Evidence

Reading pass · 12 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2007 TBC1D20 is a GTPase-activating protein (GAP) for Rab1, stimulating GTP hydrolysis by Rab1; mutation of conserved catalytic residues in the TBC domain abolishes GAP activity; overexpression of TBC1D20 blocks ER-to-Golgi transport of VSV-G protein, placing TBC1D20 in the anterograde ER-to-Golgi trafficking pathway. Biochemical GAP screen, in vitro GTPase activation assay, active-site mutagenesis, VSV-G transport assay The Journal of biological chemistry High 17901050
2007 HCV non-structural protein NS5A physically interacts with TBC1D20, and this interaction is necessary for efficient HCV replication; TBC1D20's Rab1 GAP activity is co-opted by the virus to support membrane-associated RNA replication. Protein interaction studies, Rab1 depletion (siRNA) with HCV RNA level measurement, overexpression of TBC1D20 The Journal of biological chemistry High 17901050
2012 NS5A binds TBC1D20 at lipid droplets (LDs) in an apparently irreversible manner; TBC1D20 and its substrate Rab1 are recruited by NS5A to LDs; the NS5A-TBC1D20 interaction is essential for the HCV viral life cycle, and dominant-negative Rab1 abolishes NS5A localization at viral replication sites and eliminates steady-state LDs. Live-cell fluorescence imaging (FRAP), dominant-negative Rab1 expression, HCV-infected cell immunofluorescence Journal of virology High 22491470
2013 TBC1D20 functions as a GAP for RAB1 and RAB2; loss-of-function results in enlarged Golgi morphology and aberrant lipid droplet (LD) formation in mouse embryonic fibroblasts; human fibroblasts deficient in TBC1D20 exhibit similar aberrant LD formation, linking TBC1D20 to LD metabolism. Positional cloning, functional GAP assay, cell morphology analysis (Golgi, LDs) in MEFs and human fibroblasts American journal of human genetics High 24239381
2013 Human fibroblasts deficient in RAB18 or RAB3GAP1 also exhibit aberrant LD formation, indicating that LD metabolism defects are a common cellular abnormality shared across WARBM-causative gene losses and placing TBC1D20 in the same pathway as RAB18 and RAB3GAP1. Patient-derived fibroblast analysis, lipid droplet morphology assay American journal of human genetics Medium 24239381
2016 TBC1D20, via its RAB1B GAP activity, is a key regulator of autophagosome maturation; loss of TBC1D20 impairs autophagic flux and autophagosome-lysosome fusion in lens fiber cells and testes; TBC1D20-mediated autophagosome maturation is also required for acrosome formation in spermatids. Null mutant mouse analysis, autophagic flux assays, autophagosome marker colocalization, lens and testis histology Autophagy High 27487390
2012 Excessive TBC1D20 activity (overexpression) perturbs early trafficking of HIV-1 envelope protein through the secretory pathway, impairs envelope processing, reduces envelope association with detergent-resistant membranes, and reduces HIV-1 VLP infectivity, demonstrating that TBC1D20/Rab1-mediated ER-to-Golgi trafficking is required for HIV-1 envelope maturation. TBC1D20 overexpression, VLP infectivity assay, detergent-resistant membrane fractionation Retrovirology Medium 22260459
2014 Zinc-finger nuclease-mediated in-frame deletion within the conserved TBC domain of TBC1D20 causes cataracts and disrupted acrosomal development, confirming that TBC domain integrity is required for TBC1D20 function in vivo; compound heterozygote rescue confirms bs and ZFN alleles are allelic. ZFN genome editing, allelic complementation test, histological analysis BMC genetics Medium 25476608
2017 siRNA-mediated knockdown of TBC1D20 increases Rab1 activity in CHO cells, confirming TBC1D20 as a Rab1 GAP in the secretory pathway; combined knockdown of TBC1D20 and CerS2 enhances antibody secretion, indicating TBC1D20 controls ER-to-Golgi vesicle trafficking capacity. siRNA knockdown, Rab1 activity assay, antibody productivity measurement in CHO cells Metabolic engineering Medium 28088541
2019 TBC1D20 deficiency in Sertoli cells causes ER stress-induced apoptosis via caspase-12 activation and G1/S cell cycle arrest; TBC1D20 localizes to the Golgi and ER, and its loss leads to abnormal Golgi-ER structure triggering irreversible ER stress. Subcellular fractionation/immunofluorescence localization, western blotting for ER stress markers and caspase-12, cell cycle analysis, bs mouse Sertoli cell culture Molecular human reproduction Medium 31633178
2020 TBC1D20 loss of function disrupts blood-testis barrier integrity by downregulating tight and adherens junction components (ZO-1, E-cadherin, β-catenin, Claudin 11), inducing F-actin rearrangement, and impairing Sertoli cell maturation (reduced SOX9, WT1; increased vimentin). Biotin tracer BTB integrity assay, electron microscopy, immunofluorescence of junction proteins, F-actin staining in cultured bs Sertoli cells Reproductive sciences Medium 31994000
2025 TBC1D20 is a novel Rab11 GAP; loss of TBC1D20 promotes Rab11 vesicle accumulation and F-actin depolymerization around the centrosome, facilitating ciliogenesis initiation even in cycling cells; mechanistically, TBC1D20 loss enhances Rab11-MICAL1 interaction, activating MICAL1's monooxygenase domain to depolymerize centrosomal F-actin, which in turn promotes vesicle docking and cilia assembly. TBC1D20 depletion, Rab11 activity assays, Co-IP (Rab11-MICAL1), ciliogenesis assays, F-actin imaging, MICAL1 monooxygenase domain functional studies The Journal of cell biology High 39868814

Source papers

Stage 0 corpus · 11 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2013 Loss-of-function mutations in TBC1D20 cause cataracts and male infertility in blind sterile mice and Warburg micro syndrome in humans. American journal of human genetics 107 24239381
2007 TBC1D20 is a Rab1 GTPase-activating protein that mediates hepatitis C virus replication. The Journal of biological chemistry 101 17901050
2016 TBC1D20 mediates autophagy as a key regulator of autophagosome maturation. Autophagy 63 27487390
2012 Role for TBC1D20 and Rab1 in hepatitis C virus replication via interaction with lipid droplet-bound nonstructural protein 5A. Journal of virology 44 22491470
2014 Targeted disruption of Tbc1d20 with zinc-finger nucleases causes cataracts and testicular abnormalities in mice. BMC genetics 19 25476608
2017 Secretory pathway optimization of CHO producer cells by co-engineering of the mitosRNA-1978 target genes CerS2 and Tbc1D20. Metabolic engineering 16 28088541
2012 Human immunodeficiency virus type 1 envelope proteins traffic toward virion assembly sites via a TBC1D20/Rab1-regulated pathway. Retrovirology 16 22260459
2020 TBC1D20 Is Essential for Mouse Blood-Testis Barrier Integrity Through Maintaining the Epithelial Phenotype and Modulating the Maturation of Sertoli Cells. Reproductive sciences (Thousand Oaks, Calif.) 9 31994000
2019 TBC1D20 deficiency induces Sertoli cell apoptosis by triggering irreversible endoplasmic reticulum stress in mice. Molecular human reproduction 9 31633178
2025 TBC1D20 coordinates vesicle transport and actin remodeling to regulate ciliogenesis. The Journal of cell biology 4 39868814
2020 Martsolf syndrome with novel mutation in the TBC1D20 gene in a family from Iran. American journal of medical genetics. Part A 4 32162791