Affinage

VTI1A

Vesicle transport through interaction with t-SNAREs homolog 1A · UniProt Q96AJ9

Length
217 aa
Mass
25.2 kDa
Annotated
2026-04-28
23 papers in source corpus 13 papers cited in narrative 13 extracted findings

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

VTI1A is a Qb-SNARE protein that functions at the trans-Golgi network and endosomes to mediate membrane fusion events essential for secretory cargo sorting, vesicle biogenesis, and specialized trafficking routes. VTI1A assembles into distinct SNARE complexes — including complexes with syntaxin 5/6, and a four-helix complex with VAMP-4, syntaxin 16, and syntaxin 6 — to drive anterograde sorting of synaptic and dense-core vesicle components out of the Golgi, retrograde trafficking into the TGN, and a non-conventional pathway delivering select cargo (e.g., Kv4/KChIP1 channels, GLUT4 vesicles) to the plasma membrane (PMID:9705316, PMID:24902738, PMID:30143604, PMID:36419086, PMID:16131485, PMID:19138172). A brain-specific splice variant (vti1a-β) localizes to synaptic vesicles and defines a vesicle pool that selectively sustains spontaneous neurotransmitter release, a function negatively regulated by synaptotagmin-11 through direct C2A-domain interaction with vti1a (PMID:10908612, PMID:22243751, PMID:34599505). Combined loss of vti1a and the paralog vti1b causes perinatal lethality with severe axon tract defects, progressive neurodegeneration, loss of Golgi outposts in dendrites, and impaired neurite outgrowth coupled to defective Akt and Erk signaling (PMID:21262811, PMID:36419086, PMID:39406055).

Mechanistic history

Synthesis pass · year-by-year structured walk · 11 steps
  1. 1998 High

    Establishing VTI1A as a Golgi-localized SNARE that participates in post-ER trafficking answered whether mammalian Vti1 homologs function in the secretory pathway, demonstrating that VTI1A binds α-SNAP, forms complexes with syntaxin 5 and syntaxin 6, and is required for VSV-G transport through the Golgi.

    Evidence Co-immunoprecipitation, GST-α-SNAP pulldown, and anti-VTI1A antibody microinjection blocking VSV-G trafficking in vivo

    PMID:9705316

    Open questions at the time
    • Precise Golgi sub-compartment(s) where VTI1A acts not resolved
    • Identity of the complete SNARE complex not determined
    • No loss-of-function genetic data
  2. 2000 High

    Discovery of the brain-specific splice variant vti1a-β on synaptic vesicles, forming a novel SNARE complex lacking syntaxin 1/SNAP-25, established that VTI1A participates in synaptic vesicle recycling or biogenesis rather than canonical exocytosis.

    Evidence Subcellular fractionation, immunoisolation of synaptic vesicles, and co-IP with NSF/α-SNAP binding assay in rat brain

    PMID:10908612

    Open questions at the time
    • Identity of the R-SNARE partner in this complex not determined
    • No functional assay for synaptic vesicle recycling performed
  3. 2005 High

    Demonstrating VTI1A on GLUT4 vesicles and its requirement for insulin-stimulated glucose uptake and adiponectin secretion expanded VTI1A's role to regulated exocytic trafficking in non-neuronal cells.

    Evidence Proteomics of GLUT4 vesicles, siRNA knockdown with deoxyglucose uptake and secretion assays in 3T3-L1 adipocytes

    PMID:16131485

    Open questions at the time
    • Mechanism by which insulin reduces VTI1A on GLUT4 vesicles unclear
    • SNARE partners in this trafficking step not identified
  4. 2009 Medium

    Identification of a VTI1A- and VAMP7-dependent non-conventional route delivering Kv4/KChIP1 to the plasma membrane showed that VTI1A mediates cargo-selective trafficking distinct from the canonical secretory pathway.

    Evidence siRNA knockdown of VTI1A or VAMP7 selectively blocking KChIP1-mediated Kv4 surface delivery without affecting VSVG traffic

    PMID:19138172

    Open questions at the time
    • Complete SNARE complex for this route not defined
    • Cargo selectivity mechanism unknown
    • Single lab, not independently replicated
  5. 2011 High

    The perinatal lethal phenotype of vti1a/vti1b double-knockout mice — with massive neurodegeneration and axon tract defects — established that vti1a and vti1b are functionally redundant and collectively essential for neuronal survival and endosomal membrane traffic.

    Evidence Double-knockout mouse model with histological analysis of neuronal loss in DRG and geniculate ganglia

    PMID:21262811

    Open questions at the time
    • Which specific endosomal trafficking step fails was not identified
    • Whether non-neuronal tissues are independently affected is unclear
  6. 2012 High

    Live imaging and electrophysiology revealed that vti1a marks a synaptic vesicle pool selectively maintaining spontaneous neurotransmitter release, with a truncated vti1a augmenting this release, resolving how distinct vesicle pools sustain evoked versus spontaneous transmission.

    Evidence Multicolor live imaging, dominant-negative/truncation expression, and mEPSC recording in cultured neurons

    PMID:22243751

    Open questions at the time
    • Mechanism of autoinhibition by the vti1a N-terminus not resolved
    • Whether vti1a-positive vesicles are a distinct biogenetic population or a recycling state is unknown
  7. 2014 High

    Analysis of vti1a-null chromaffin cells showed that VTI1A functions at the TGN in dense-core vesicle biogenesis — controlling vesicle number, size, and synaptobrevin-2 loading — rather than in the exocytic fusion reaction itself, as rescue required long-term but not short-term re-expression.

    Evidence vti1a-null chromaffin cells with carbon-fiber amperometry, electrophysiology, and timed rescue experiments

    PMID:24902738

    Open questions at the time
    • How VTI1A sorts cargo into nascent DCVs mechanistically is undefined
    • Relationship between DCV biogenesis defect and Ca2+-channel surface reduction not clarified
  8. 2018 High

    Two studies placed VTI1A squarely at the Golgi cargo-sorting step: vti1a/b-deficient neurons accumulated SNAP25 and DCV cargo in the Golgi with impaired axonal delivery, and TGN organization was disrupted with loss of recycling proteins (TGN38, TMEM87A), establishing VTI1A in both anterograde sorting and retrograde TGN maintenance.

    Evidence Vti1a/b-deficient neurons with live-cell imaging, secretion assays, electron microscopy, and quantitative immunofluorescence

    PMID:30143604 PMID:36460703

    Open questions at the time
    • Whether anterograde and retrograde defects stem from the same SNARE complex or distinct complexes is unresolved
    • Sphingolipid homeostasis link not mechanistically connected
  9. 2021 High

    Demonstration that synaptotagmin-11 directly binds vti1a via its C2A domain and that vti1a knockdown reverses the enhanced spontaneous release of Syt11-KO neurons identified the molecular brake on vti1a-positive vesicle fusion, establishing the Syt11–vti1a axis as a regulatory module for spontaneous neurotransmission.

    Evidence GST pulldown, co-IP, affinity purification for direct interaction; genetic epistasis (Syt11-KO + vti1a-KD) with mEPSC recording

    PMID:34599505

    Open questions at the time
    • Whether Syt11 clamps vti1a-SNARE complex assembly or a downstream step is unknown
    • Ca2+-dependence of C2A–vti1a interaction not characterized
  10. 2022 Medium

    Assignment of VTI1A as the Qb-SNARE in a complex with VAMP-4/syntaxin 16/syntaxin 6 required for enlargeosome-mediated neurite outgrowth and Golgi outpost formation in dendrites defined the specific SNARE complex and cellular process downstream of VTI1A in neuronal morphogenesis.

    Evidence Vti1a/b double-KO primary neurons with neurite length measurements, Golgi outpost imaging, and pharmacological stimulation

    PMID:36419086

    Open questions at the time
    • Direct biochemical reconstitution of this four-helix complex not performed
    • How Golgi outpost loss impairs neurite elongation mechanistically is unclear
  11. 2024 Medium

    Connecting vti1a/b deficiency to impaired Akt and Erk signaling during neurite outgrowth placed VTI1A-dependent trafficking upstream of growth-factor signal transduction, broadening its role beyond vesicle biogenesis to signaling pathway regulation.

    Evidence CRISPR/Cas9 double KO in N1E-115 neuroblastoma cells with western blotting for phospho-Akt and phospho-Erk

    PMID:39406055

    Open questions at the time
    • Whether signaling defects are indirect consequences of receptor mis-trafficking is untested
    • Single cell line, not validated in primary neurons

Open questions

Synthesis pass · forward-looking unresolved questions
  • Key unresolved questions include the structural basis of VTI1A SNARE complex selectivity, the mechanism by which VTI1A sorts specific cargo at the TGN, how the autoinhibitory N-terminal domain regulates spontaneous fusion, and whether VTI1A directly controls signaling receptor trafficking to modulate Akt/Erk pathways.
  • No structural model of any VTI1A-containing SNARE complex
  • Cargo recognition mechanism at the TGN unresolved
  • Autoinhibition mechanism of full-length vti1a not defined

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0005198 structural molecule activity 4
Localization
GO:0005794 Golgi apparatus 4 GO:0031410 cytoplasmic vesicle 3 GO:0005768 endosome 2
Pathway
R-HSA-5653656 Vesicle-mediated transport 7 R-HSA-112316 Neuronal System 4 R-HSA-1266738 Developmental Biology 3 R-HSA-9609507 Protein localization 3
Partners
NAPANSFSTX16STX5STX6SYT11VAMP4VAMP7
Complex memberships
Syntaxin 5/syntaxin 6/vti1a SNARE complexVAMP-4/syntaxin 16/syntaxin 6/vti1a SNARE complex

Evidence

Reading pass · 13 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2000 Vti1a-beta (a brain-specific splice variant of Vti1a with a 7-amino-acid insertion) is enriched in small synaptic vesicles and clathrin-coated vesicles, co-purifies with synaptobrevin on immunoisolated synaptic vesicles, and forms a novel SNARE complex in nerve terminals that binds NSF and alpha-SNAP but does not contain syntaxin 1 or SNAP-25, suggesting a role in membrane fusion during recycling or biogenesis of synaptic vesicles rather than exocytosis. Subcellular fractionation, immunoisolation of synaptic vesicles, co-immunoprecipitation, NEM-sensitive factor binding assay The Journal of neuroscience High 10908612
1998 VTI1A (Vti1-rp2) is an integral membrane SNARE enriched in the Golgi that binds alpha-SNAP, co-immunoprecipitates with syntaxin 5 and syntaxin 6, and is required for ER-to-plasma-membrane trafficking of VSV-G protein, arrested specifically at the Golgi when antibodies against VTI1A are microinjected. Co-immunoprecipitation, GST-alpha-SNAP affinity pulldown, antibody microinjection with VSV-G trafficking assay, immunofluorescence microscopy The Journal of biological chemistry High 9705316
2005 Vti1a is a component of insulin-sensitive GLUT4-containing vesicles in 3T3-L1 adipocytes; insulin treatment decreases Vti1a in these membranes, and siRNA-mediated knockdown of Vti1a inhibits both adiponectin secretion and insulin-stimulated glucose uptake, indicating a role in GLUT4 and adiponectin trafficking. Proteomics/mass spectrometry, subcellular fractionation, co-localization, siRNA knockdown, deoxyglucose uptake assay, secretion assay The Journal of biological chemistry High 16131485
2009 Vti1a and VAMP7 define a non-conventional trafficking route to the plasma membrane used by Kv4 potassium channels and KChIP1; KChIP1 vesicles co-localize with Vti1a and VAMP7, and siRNA knockdown of Vti1a (or VAMP7) selectively inhibits Kv4/KChIP1 cell-surface delivery without affecting conventional VSVG or KChIP2-mediated Kv4 traffic. Co-localization imaging, siRNA knockdown, cell-surface trafficking assay The Biochemical journal Medium 19138172
2011 Loss of vti1a in combination with vti1b causes perinatal lethality, major axon tract defects, and progressive neurodegeneration (>95% neuron loss in DRG and geniculate ganglia by E18.5), while single knockouts are viable, indicating that vti1a and vti1b are functionally redundant in supporting endosomal membrane traffic required for neuronal survival. Vti1a/Vti1b double knockout mouse model, histological analysis, organelle morphology examination PNAS High 21262811
2012 Vti1a identifies a synaptic vesicle pool that preferentially recycles under resting conditions and selectively maintains high-frequency spontaneous neurotransmitter release; loss of vti1a function reduces spontaneous (but not evoked) release, and a truncated vti1a augments spontaneous release more than full-length vti1a, suggesting autoinhibitory regulation of vti1a function. Multicolor live imaging, loss-of-function (dominant-negative/truncation expression), electrophysiology (mEPSC recording) Neuron High 22243751
2014 Vti1a localizes near the trans-Golgi network (partially overlapping with syntaxin-6) in chromaffin cells and functions in dense-core vesicle biogenesis; vti1a-null cells have fewer vesicles of reduced size and less synaptobrevin-2 content, and fewer Ca2+-channels at the plasma membrane, impairing exocytosis without altering release kinetics or Ca2+ sensitivity; long-term but not short-term re-expression rescues secretion, confirming an upstream biogenesis role. Vti1a null chromaffin cells, immunofluorescence, carbon-fiber amperometry, electrophysiology, rescue experiments (long-term vs. short-term expression) The EMBO journal High 24902738
2018 Vti1a/b-deficient neurons show severely impaired synaptic vesicle and dense-core vesicle secretion due to defective sorting of secretory cargo and synaptic secretion machinery (e.g., SNAP25) out of the Golgi; delivery of SNAP25 and DCV-cargo into axons is decreased and these molecules accumulate in the Golgi, while retrograde cholera toxin trafficking is compromised, placing Vti1a function at the level of cargo sorting at the Golgi. Vti1a/b-deficient neurons, live-cell imaging, secretion assays, immunofluorescence, electron microscopy Nature communications High 30143604
2018 The VTI1A-TCF4 fusion protein (generated by chromosomal rearrangement) acts as a dominant-negative regulator of Wnt signaling in colon cancer cells; the VTI1A promoter is highly active in colon cells compared to the TCF7L2 promoter, and the transcription factor CDX2 directly activates transcription from the VTI1A promoter. Luciferase reporter assay, overexpression in LS174T cells, CDX2 transcription factor analysis PLoS one Medium 29975781
2021 Synaptotagmin-11 (Syt11) directly interacts with vti1a via its C2A domain and suppresses spontaneous neurotransmitter release by inhibiting vti1a-containing vesicles; knockdown of vti1a reverses the increased spontaneous release phenotype of Syt11-KO neurons, establishing vti1a as the primary downstream effector of Syt11-mediated inhibition. GST pulldown, co-immunoprecipitation, affinity purification, Syt11-KO and vti1a-knockdown neurons, mEPSC electrophysiology Journal of neurochemistry High 34599505
2022 Vti1a (or vti1b) functions as the Qb-SNARE in a four-helix SNARE complex with VAMP-4 (R-SNARE), syntaxin 16 (Qa-SNARE), and syntaxin 6 (Qc-SNARE) required for enlargeosome-mediated neurite outgrowth; double-deficient neurons lack Golgi outposts in dendrites and show significantly shorter neurites that cannot be rescued by neurotrophic factors or enlargeosome-stimulating ROCK inhibitor. Vti1a/Vti1b double-KO primary neurons (hippocampal and cortical), neurite length measurements, Golgi outpost imaging, pharmacological stimulation Neural development Medium 36419086
2022 Vti1a and Vti1b are required for distinct aspects of TGN and cis-/medial Golgi organization; in their absence, cis-/medial Golgi markers are increased while TGN recycling proteins (TGN38, TMEM87A) are decreased, and DCV cargo distribution in the Golgi is lost, consistent with defective retrograde trafficking into the TGN. Vti1a/b-deficient neurons, immunofluorescence quantification, pharmacological perturbation of sphingolipid homeostasis Scientific reports Medium 36460703
2024 Double deficiency of vti1a and vti1b in N1E-115 neuroblastoma cells impairs neurite elongation and disrupts Akt signaling (enlargeosome/ROCK-induced pathway) and Erk signaling (BDNF-induced pathway), placing vti1a/b upstream of these signal transduction cascades during neurite outgrowth. CRISPR/Cas9 double knockout in N1E-115 cells, neurite length measurement, western blotting for Akt and Erk signaling, pharmacological stimulation European journal of cell biology Medium 39406055

Source papers

Stage 0 corpus · 23 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2011 Genomic sequencing of colorectal adenocarcinomas identifies a recurrent VTI1A-TCF7L2 fusion. Nature genetics 246 21892161
2012 Vti1a identifies a vesicle pool that preferentially recycles at rest and maintains spontaneous neurotransmission. Neuron 142 22243751
2000 The SNARE Vti1a-beta is localized to small synaptic vesicles and participates in a novel SNARE complex. The Journal of neuroscience : the official journal of the Society for Neuroscience 80 10908612
2011 Lack of the endosomal SNAREs vti1a and vti1b led to significant impairments in neuronal development. Proceedings of the National Academy of Sciences of the United States of America 55 21262811
1998 A 29-kilodalton Golgi soluble N-ethylmaleimide-sensitive factor attachment protein receptor (Vti1-rp2) implicated in protein trafficking in the secretory pathway. The Journal of biological chemistry 54 9705316
2018 Vti1a/b regulate synaptic vesicle and dense core vesicle secretion via protein sorting at the Golgi. Nature communications 47 30143604
2005 The v-SNARE Vti1a regulates insulin-stimulated glucose transport and Acrp30 secretion in 3T3-L1 adipocytes. The Journal of biological chemistry 43 16131485
2009 A VAMP7/Vti1a SNARE complex distinguishes a non-conventional traffic route to the cell surface used by KChIP1 and Kv4 potassium channels. The Biochemical journal 40 19138172
2014 The SNARE protein vti1a functions in dense-core vesicle biogenesis. The EMBO journal 37 24902738
2017 Cumulative evidence for relationships between multiple variants in the VTI1A and TCF7L2 genes and cancer incidence. International journal of cancer 18 28949031
2020 Vesicle transport through interaction with t-SNAREs 1a (Vti1a)'s roles in neurons. Heliyon 14 32775753
2018 The VTI1A-TCF4 colon cancer fusion protein is a dominant negative regulator of Wnt signaling and is transcriptionally regulated by intestinal homeodomain factor CDX2. PloS one 13 29975781
2022 Primary neurons lacking the SNAREs vti1a and vti1b show altered neuronal development. Neural development 11 36419086
2021 Synaptotagmin-11 inhibits spontaneous neurotransmission through vti1a. Journal of neurochemistry 10 34599505
2022 The Role of Vti1a in Biological Functions and Its Possible Role in Nervous System Disorders. Frontiers in molecular neuroscience 9 35711736
2021 Ablation of Vti1a/1b Triggers Neural Progenitor Pool Depletion and Cortical Layer 5 Malformation in Late-embryonic Mouse Cortex. Neuroscience 8 33774122
2022 Epigenome-Wide Association Study Identified VTI1A DNA Methylation Associated With Accelerometer-Assessed Physical Activity. Medicine and science in sports and exercise 7 35700439
2015 Single nucleotide polymorphisms in VTI1A gene contribute to the susceptibility of Chinese population to non-small cell lung cancer. The International journal of biological markers 7 25744365
2022 Vti1a/b support distinct aspects of TGN and cis-/medial Golgi organization. Scientific reports 4 36460703
2019 Detection of Novel Fusion Transcript VTI1A-CFAP46 in Hepatocellular Carcinoma. Gastrointestinal tumors 4 31602373
2024 The double deficiency of the SNARE proteins vti1a and vti1b affects neurite outgrowth and signaling in N1E-115 neuroblastoma cells. European journal of cell biology 2 39406055
2026 Alterations in bone malformation in the absence of the endosomal SNAREs Vti1a and Vti1b. PloS one 0 41838692
2026 Reduction in Synaptic Vesicle Protein Abundance but Increased Amounts of Nsg2 and Lpcat1 in Cerebral Cortices Without the Endosomal SNARE Proteins Vti1a and Vti1b. Proteomics 0 41859820