Affinage

GDI1

Rab GDP dissociation inhibitor alpha · UniProt P31150

Length
447 aa
Mass
50.6 kDa
Annotated
2026-06-10
20 papers in source corpus 10 papers cited in narrative 11 extracted findings
Cross-family judge vs UniProt: Affinage preferred faithfulness: 5/5 claims corpus-supported (100%)

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

GDI1 encodes αGDI, a GDP-dissociation inhibitor that controls the membrane cycling of prenylated Rab and Rho-family GTPases by extracting their GDP-bound form from membranes and maintaining a soluble cytosolic pool for recycling back to donor compartments (PMID:9620768, PMID:8157010, PMID:25014207). Conserved from yeast, where Gdi1p slows GDP dissociation from the Rab Sec4p and is required for protein transport through multiple stages of the secretory pathway (PMID:8157010), αGDI selectively recognizes the inactive GDP-bound GTPase: extraction of prenylated Rac1 from membranes is blocked once GEFs (Vav2, Dbl, Tiam1, P-Rex1, TrioN) load it with GTP or once the effector Pak1 binds (PMID:25014207). The directionality of this cycle is set by opposing membrane factors and post-translational control — the prenylated Rab acceptor PRA1 antagonizes αGDI-mediated extraction of Rab3A to favor membrane retention (PMID:10751420), PKCα phosphorylation at Ser96 lowers αGDI affinity for RhoA and thereby licenses RhoA activation, actin stress-fiber formation, and endothelial permeability without affecting Rac1 or Cdc42 (PMID:17636025), and SUMOylation releases sequestered GDP-bound Rab-1 to drive phagosome maturation. In the nervous system, αGDI is essential for synaptic vesicle biogenesis and reserve-pool maintenance, with its loss reducing total vesicle number and disrupting short-term plasticity (PMID:18829665), and acts beyond Rab3A on additional Rab GTPases in vivo (PMID:15078563). Loss-of-function mutations in GDI1 cause X-linked intellectual disability, with the L92P missense mutation reducing RAB3A binding/recycling and a null mutation abolishing function (PMID:9620768).

Mechanistic history

Synthesis pass · year-by-year structured walk · 11 steps
  1. 1994 High

    Established the core biochemical activity by showing the yeast ortholog physically recycles a Rab/Sec4 GTPase from membranes to maintain a soluble pool needed for secretion.

    Evidence GDP dissociation and membrane extraction assays with purified Gdi1p and Sec4p, in vivo conditional depletion, and genetic complementation of sec19-1

    PMID:8157010

    Open questions at the time
    • Did not define which mammalian Rabs are substrates
    • No structural basis for prenyl-dependent recognition
  2. 1998 High

    Linked GDI1 to human disease and to a specific neuronal Rab, showing it is required for RAB3A regulation in vesicular transport.

    Evidence Patient mutation identification plus functional RAB3A binding/recycling assay with the L92P mutant protein and a null allele

    PMID:9620768

    Open questions at the time
    • Did not establish the full repertoire of neuronal Rab substrates
    • Mechanism connecting RAB3A dysregulation to cognitive deficit unresolved
  3. 2000 High

    Identified an antagonist that biases the extraction/retention equilibrium, showing membrane factors counteract αGDI to keep Rabs membrane-bound.

    Evidence In vitro extraction assay with recombinant proteins, fractionation, and binding assays showing PRA1 blocks GDI1 solubilization of Rab3A

    PMID:10751420

    Open questions at the time
    • Stoichiometry and structural interface with αGDI not defined
    • Specificity across other Rabs not tested
  4. 2002 Medium

    Defined the in vivo cognitive consequence of αGDI loss, showing a selective requirement for short-term temporal associations rather than global CNS function.

    Evidence Behavioral battery (fear conditioning, radial maze, social tests) in Gdi1 knockout mice

    PMID:12354782

    Open questions at the time
    • Behavioral readout is indirect for molecular mechanism
    • Did not identify the responsible Rab/cell type
  5. 2004 Medium

    Showed via genetic comparison that αGDI acts on Rabs beyond Rab3A, since the Gdi1 and Rab3a knockout phenotypes diverge.

    Evidence Parallel behavioral battery in Rab3a−/− versus Gdi1−/− mice

    PMID:15078563

    Open questions at the time
    • Did not identify the additional Rab substrates
    • No biochemical mapping of the divergent pathway
  6. 2007 High

    Revealed phosphoregulation as a switch, showing PKCα phosphorylation at Ser96 selectively releases RhoA to permit its activation.

    Evidence S96A/S96D mutagenesis with RhoA activation, MLC phosphorylation, stress-fiber imaging, and endothelial permeability assays

    PMID:17636025

    Open questions at the time
    • Whether this regulation operates in neurons unknown
    • Did not show effect on Rab-family clients
  7. 2008 High

    Connected αGDI activity to synaptic structure, showing loss depletes synaptic vesicles and disrupts recycling and short-term plasticity.

    Evidence Electron microscopy, electrophysiology, and behavior in Gdi1 knockout mice

    PMID:18829665

    Open questions at the time
    • Which Rab cycle defect causes vesicle loss not pinpointed
    • Endosomal recycling step not molecularly defined
  8. 2014 High

    Defined the nucleotide- and effector-state selectivity, showing GDI1 extracts only GDP-bound prenylated Rac1 and is blocked once GEFs or effectors engage it.

    Evidence Liposome reconstitution with purified prenylated Rac1, GEF-stimulated exchange, and Pak1 binding assays

    PMID:25014207

    Open questions at the time
    • In-cell competition between GEFs and GDI1 not quantified
    • Did not test all physiological Rab clients
  9. 2016 Medium

    Placed αGDI-mediated trafficking in a directed-secretion context, showing the ortholog targets specialized membrane to an invasive interface under extracellular control.

    Evidence Genome-wide RNAi screen and live-cell imaging of anchor-cell invadopodia in C. elegans

    PMID:26765257

    Open questions at the time
    • The Rab(s) carrying invadopodial membrane not identified
    • Signal-to-GDI-1 transduction mechanism unknown
  10. 2020 Medium

    Extended αGDI function to non-neuronal cell types, showing astrocytic Gdi1 loss impairs working memory through altered glucose metabolism rescuable by glycolytic inhibition.

    Evidence Inducible astrocyte-specific knockout with FDG uptake imaging, FRET glucose/lactate measurements, proteomics, and 2-DG rescue

    PMID:33309713

    Open questions at the time
    • Trafficking link between αGDI and glycolytic enzymes not mechanistically defined
    • Specific Rab mediating metabolic phenotype unknown
  11. 2025 Medium

    Added SUMOylation as a regulatory input, showing modification at K270 releases sequestered GDP-Rab-1 to drive phagosome maturation and efferocytosis.

    Evidence C. elegans genetics, SUMOylation and mutagenesis at K270, Rab-GTP/GDP state analysis, phagosome and mammalian efferocytosis assays (preprint)

    Open questions at the time
    • Preprint not yet peer-reviewed
    • Mammalian SUMOylation site role validated only in efferocytosis assay
    • Structural effect of K270 SUMOylation on GTPase release undefined

Open questions

Synthesis pass · forward-looking unresolved questions
  • The full in vivo Rab substrate repertoire of αGDI and how phosphorylation versus SUMOylation are integrated to selectively gate specific GTPase cycles remains unresolved.
  • No structural model of substrate selection across modifications
  • Crosstalk between Ser96 phosphorylation and K270 SUMOylation untested
  • Mapping of disease mutations to specific Rab dysregulation incomplete

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0098772 molecular function regulator activity 4 GO:0140313 molecular sequestering activity 3
Localization
GO:0005829 cytosol 3 GO:0005886 plasma membrane 3
Pathway
R-HSA-5653656 Vesicle-mediated transport 3 R-HSA-112316 Neuronal System 2 R-HSA-162582 Signal Transduction 2
Partners
PAK1PRA1RAB1RAB3ARAC1RHOASEC4

Evidence

Reading pass · 11 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
1998 GDI1 encodes αGDI (uGDI), a Rab GDP-dissociation inhibitor; a missense mutation L92P reduces binding and recycling of RAB3A, and a null mutation abolishes function, establishing that GDI1 is required for RAB3A regulation and vesicular transport in neurons. Patient mutation identification, functional binding/recycling assay of L92P mutant protein with RAB3A Nature genetics High 9620768
1994 Yeast Gdi1p (S. cerevisiae ortholog of GDI1/sec19) slows GDP dissociation from Sec4p and releases the GDP-bound form of Sec4p from yeast membranes; depletion of Gdi1p in vivo causes loss of the soluble pool of Sec4p and blocks protein transport at multiple stages of the secretory pathway, consistent with a role in recycling Rab/Sec4 GTPases from target membranes back to vesicular pools. Biochemical GDP dissociation assay with purified Gdi1p and Sec4p; in vivo conditional depletion; membrane extraction assay; complementation analysis (allelic to sec19-1) The EMBO journal High 8157010
2000 PRA1 (prenylated Rab acceptor) inhibits GDI1-mediated extraction of membrane-bound Rab3A; GDI1 binds weakly to PRA1, and addition of PRA1 prevents GDI1 from solubilizing membrane-associated Rab3A, indicating that membrane retention vs. extraction of Rab GTPases is controlled by opposing actions of PRA1 and GDI1. Subcellular fractionation, immunocytochemistry, in vitro extraction assay with recombinant proteins, co-immunoprecipitation/binding assay The Journal of biological chemistry High 10751420
2007 PKCα phosphorylates GDI-1 at Ser96 in the C-terminus, reducing GDI-1 affinity for RhoA and thereby enabling RhoA activation; a phosphodefective S96A mutant retains inhibitory activity toward RhoA and suppresses thrombin-induced actin stress fiber formation and increased endothelial permeability, while a phosphomimetic S96D mutant induces RhoA activity and permeability independently of thrombin. This phosphorylation selectively affects RhoA but not Rac1 or Cdc42. Site-directed mutagenesis (S96A, S96D), overexpression/transduction in endothelial cells, RhoA activation assay, myosin light chain phosphorylation assay, actin stress fiber imaging, endothelial permeability assay, domain deletion analysis Molecular and cellular biology High 17636025
2008 Loss of αGDI (Gdi1 knockout) in mice impairs synaptic vesicle (SV) biogenesis and recycling in the hippocampus: the SV reserve pool is altered and total SV number is reduced by ~50%, associated with defective endosomal-dependent recycling and altered short-term synaptic plasticity. Electron microscopy of synapses, electrophysiology (short-term plasticity), behavioral testing in Gdi1 knockout mice Human molecular genetics High 18829665
2014 GDI1 extracts prenylated Rac1 from liposomes preferentially in the inactive GDP-bound state; this extraction is prevented when Rac1 is activated to GTP-bound state by GEFs (Vav2, Dbl, Tiam1, P-Rex1, TrioN) or when Rac1 is bound by the effector Pak1. Dissociation of Rac1-GDP from GDI1 is strongly correlated with GEF-mediated liposome association and GDP/GTP exchange. Liposome reconstitution with purified prenylated Rac1 from insect cells, GDI1 extraction assay, GEF-stimulated exchange assays, Pak1 binding assay PloS one High 25014207
2002 Deletion of Gdi1 in mice causes selective impairment in tasks requiring short-term temporal associations (short-term memory) and alters social behavior, while sparing spatial memory, emotional behavior, and most other CNS functions, demonstrating that αGDI is specifically required for forebrain functions underlying temporal associations. Gdi1 knockout mouse behavioral battery (fear conditioning, radial maze, social behavior tests) Human molecular genetics Medium 12354782
2004 Rab3a knockout mice show behavioral phenotypes (spatial reversal learning deficits, increased exploration) distinct from Gdi1 knockout mice, indicating that the putative synaptic interaction between αGDI and Rab3a does not solely account for the Gdi1 behavioral phenotype and that αGDI regulates additional Rab GTPases beyond Rab3a in vivo. Genetic epistasis via parallel behavioral battery in Rab3a−/− vs Gdi1−/− mice The European journal of neuroscience Medium 15078563
2016 In C. elegans, gdi-1 (GDI1 ortholog) functions in anchor cells to promote invadopodia formation by mediating membrane trafficking of specialized invadopodial membrane to the invasive membrane interface; loss of gdi-1 redistributes invadopodial membrane to plasma membrane throughout the cell rather than concentrating it at the invasion site. A pro-invasive extracellular signal from vulval cells controls GDI-1 activity and invadopodial membrane trafficking. Genome-wide RNAi screen, live-cell imaging of membrane trafficking in anchor cells, loss-of-function analysis in C. elegans invasion model PLoS genetics Medium 26765257
2020 Gdi1 deletion in astrocytes specifically impairs working memory in mice, associated with increased glucose uptake and altered astrocytic glycolytic enzyme levels; inhibiting glycolysis with 2-deoxy-d-glucose rescues the working memory deficit, establishing an astrocyte-based mechanism for αGDI in cognitive function. Inducible astrocyte-specific Gdi1 knockout mouse, [18F]-FDG uptake imaging in brain slices, FRET-based measurements of glucose/lactate in astrocytes, proteomic analysis, behavioral testing, pharmacological rescue with 2-DG Metabolism: clinical and experimental Medium 33309713
2025 In C. elegans, GEI-17 (SUMO E3 ligase) SUMOylates GDI-1 at K270; SUMOylated GDI-1 releases GDP-bound RAB-1, which is converted to GTP-bound RAB-1 by the GDI displacement factor PRAF-3, enabling RAB-7 translocation from ER to Golgi and phagosome maturation/degradation. Without GDI-1 SUMOylation, GDP-RAB-1 remains sequestered in the cytoplasm, impairing phagosomal degradation. A conserved SUMOylation site in mammalian GDI1 plays a role in efferocytosis regulation. C. elegans genetics, SUMOylation assay, site-directed mutagenesis at K270, Rab-GTP/GDP state analysis, phagosome maturation assay, mammalian efferocytosis assay bioRxivpreprint Medium

Source papers

Stage 0 corpus · 20 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
1998 Mutations in GDI1 are responsible for X-linked non-specific mental retardation. Nature genetics 279 9620768
1994 GDI1 encodes a GDP dissociation inhibitor that plays an essential role in the yeast secretory pathway. The EMBO journal 175 8157010
2002 Deletion of the mental retardation gene Gdi1 impairs associative memory and alters social behavior in mice. Human molecular genetics 88 12354782
2000 PRA1 inhibits the extraction of membrane-bound rab GTPase by GDI1. The Journal of biological chemistry 66 10751420
2007 GDI-1 phosphorylation switch at serine 96 induces RhoA activation and increased endothelial permeability. Molecular and cellular biology 51 17636025
2004 Mice deficient for the synaptic vesicle protein Rab3a show impaired spatial reversal learning and increased explorative activity but none of the behavioral changes shown by mice deficient for the Rab3a regulator Gdi1. The European journal of neuroscience 46 15078563
2008 Cognitive impairment in Gdi1-deficient mice is associated with altered synaptic vesicle pools and short-term synaptic plasticity, and can be corrected by appropriate learning training. Human molecular genetics 44 18829665
2016 A Sensitized Screen for Genes Promoting Invadopodia Function In Vivo: CDC-42 and Rab GDI-1 Direct Distinct Aspects of Invadopodia Formation. PLoS genetics 36 26765257
2020 Inhibiting glycolysis rescues memory impairment in an intellectual disability Gdi1-null mouse. Metabolism: clinical and experimental 17 33309713
1998 Evaluation of two X chromosomal candidate genes for Rett syndrome: glutamate dehydrogenase-2 (GLUD2) and rab GDP-dissociation inhibitor (GDI1). American journal of medical genetics 17 9674910
1994 Evolutionary conservation and genomic organization of XAP-4, an Xq28 located gene coding for a human rab GDP-dissociation inhibitor (GDI). Mammalian genome : official journal of the International Mammalian Genome Society 14 7849400
2014 Liposome reconstitution and modulation of recombinant prenylated human Rac1 by GEFs, GDI1 and Pak1. PloS one 13 25014207
2011 Novel GDI1 mutation in a large family with nonsyndromic X-linked intellectual disability. American journal of medical genetics. Part A 13 22002931
2010 Searching for signaling balance through the identification of genetic interactors of the Rab guanine-nucleotide dissociation inhibitor gdi-1. PloS one 11 20498707
2011 Possible involvement of GDI1 protein, a GDP dissociation inhibitor related to vesicle transport, in an amelioration of zinc toxicity in Saccharomyces cerevisiae. Yeast (Chichester, England) 8 22125264
2017 Exome sequencing identifies a novel mutation of the GDI1 gene in a Chinese non-syndromic X-linked intellectual disability family. Genetics and molecular biology 5 28863211
2001 The GDI1 genes from Kluyveromyces lactis and Pichia pastoris: cloning and functional expression in Saccharomyces cerevisiae. Yeast (Chichester, England) 5 11447595
2024 ECM1-associated miR-1260b promotes osteogenic differentiation by targeting GDI1. Acta histochemica 3 38266317
2023 GDP dissociation inhibitor 1 (GDI1) attenuates β-amyloid-induced neurotoxicity in Alzheimer's diseases. Neuroscience letters 3 38013121
2011 Mutations in GDI1 and X-linked non-specific mental retardation. Annali di igiene : medicina preventiva e di comunita 0 21736009

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