STX10

STX10 is a trans-Golgi network (TGN)-localized SNARE protein that participates in retrograde membrane trafficking between endosomes and the TGN. It forms a quaternary SNARE complex with STX16, Vti1a, and VAMP3 that operates downstream of Rab9 and the tether GCC185 to mediate mannose 6-phosphate receptor (MPR) retrieval from late endosomes to the TGN; depletion of STX10 causes MPR missorting and hypersecretion of lysosomal enzymes, defining a transport route distinct from the STX6-dependent pathway used for TGN46 and cholera toxin (PMID:18195106). STX10 interacts with the GARP tethering complex via hVps52, linking vesicle docking to SNARE-mediated fusion at the TGN (PMID:15878329), and also co-immunoprecipitates endosomal syntaxin 12/13; its knockdown alters transferrin receptor surface expression, indicating an additional role at the TGN–endosome boundary (PMID:16154903).

1. 1998 Medium

   Cloning of STX10 established it as a new syntaxin-family SNARE localized to intracellular membranes overlapping with TGN markers, placing it in the Golgi/TGN trafficking machinery.

   Evidence Molecular cloning, indirect immunofluorescence co-localization with GS28, brefeldin A sensitivity in human cells

   PMID:9446797

   Open questions at the time

   • No functional assay was performed; localization was inferred from a single Golgi marker and pharmacological perturbation
   • Binding partners and SNARE complex composition unknown
2. 2005 Medium

   Identification of the GARP tethering complex (hVps52/53/54) as a STX10 interactor via hVps52 connected vesicle tethering to SNARE-mediated fusion at the TGN, and simultaneous functional studies showed STX10 is dispensable for shiga toxin retrograde transport but influences transferrin receptor surface levels through interaction with syntaxin 12/13.

   Evidence Co-immunoprecipitation of GARP–STX10; siRNA knockdown with shiga toxin transport and transferrin receptor assays; co-IP of STX10 with syntaxin 12/13

   PMID:15878329 PMID:16154903

   Open questions at the time

   • The specific cargo pathway requiring STX10 was not yet defined
   • SNARE complex partners beyond STX6/STX16 interaction were unresolved
   • Mechanism linking STX10 knockdown to altered transferrin receptor dynamics was not elucidated
3. 2008 High

   Defining the STX10/STX16/Vti1a/VAMP3 quaternary SNARE complex and its requirement for Rab9-dependent MPR retrieval from late endosomes to the TGN resolved which cargo route STX10 operates in and distinguished it from the STX6-dependent early-endosome pathway.

   Evidence siRNA depletion of individual SNAREs, co-immunoprecipitation of the quaternary complex, hexosaminidase secretion and MPR localization assays, cholera toxin/TGN46 transport controls in human cells

   PMID:18195106

   Open questions at the time

   • Structural basis for complex assembly and selectivity over the STX6-containing complex is unknown
   • Mouse and rat cells lack STX10; the compensating SNARE in these species has not been identified
   • Whether the STX10-dependent pathway contributes to pathologies involving lysosomal enzyme missorting has not been tested
4. 2021 Low

   Proximity labeling identified VAPB as a novel STX10-proximal protein, suggesting a potential ER–TGN membrane contact site connection, though functional validation is lacking.

   Evidence BioID proximity labeling with BirA*-Stx10 and mass spectrometry in human cells (tag artifacts noted by authors)

   PMID:34323972

   Open questions at the time

   • No reciprocal validation or functional assay for the STX10–VAPB interaction
   • BirA* tag altered STX10 localization, limiting confidence in interactome data
   • Physiological relevance of a STX10–VAPB link to ER–TGN contact sites is untested

• The structural basis for STX10 selectivity within the TGN SNARE network, the identity of the compensating SNARE in rodents that lack STX10, and the functional significance of the STX10–VAPB proximity remain open questions.
• No crystal or cryo-EM structure of the STX10-containing SNARE complex
• Rodent compensatory mechanism for MPR retrieval without STX10 is uncharacterized
• In vivo relevance of STX10 loss in human tissues or disease models has not been assessed