GOSR1

GOSR1 (GS28) is a cis-Golgi integral membrane Qb-SNARE that functions as a core component of the SNARE machinery driving vesicular transport through the secretory pathway (PMID:8638159). It assembles into compositionally distinct SNARE complexes with syntaxin 5 as the central partner: a syntaxin 5/GS28/Ykt6/Bet1 complex acting in a late stage of ER-to-Golgi transport (PMID:11323436), and a syntaxin 5/GS28/Ykt6/GS15 complex operating in intra-Golgi (medial cisternae) transport and in retrograde transport from early/recycling endosomes to the trans-Golgi network (PMID:12388752, PMID:15215310). The conserved SNARE motif is essential for fusion activity, and its t-SNARE function is so well preserved that human GOSR1 rescues rhodopsin trafficking and retinal degeneration in Drosophila gos28 mutants (PMID:25261468). GS28–syntaxin 5 complexes are dynamically cycled by the ATP-hydrolysis-dependent action of NSF and alpha-SNAP, which dissociate assembled complexes (PMID:9325254), while a distinct ATPase-independent NSF activity promotes binding of GATE-16 to GS28 to shield it from premature engagement with syntaxin 5 during Golgi reassembly (PMID:12070132). GS28 levels and trafficking are further regulated by extraction into COPI-coated vesicles to control inter-cisternal connectivity (PMID:23387339) and by ORP7, which destabilizes GS28 through GATE-16 sequestration and proteasomal degradation (PMID:21669198). Beyond membrane traffic, GS28 also associates with MDM2 and p53 to inhibit p53 ubiquitination and enhance DNA-damage-induced apoptosis (PMID:22397410).

1. 1996 High

   Established the existence and identity of GS28 as a dedicated Golgi SNARE, answering whether a distinct integral membrane protein mediates the docking/fusion step of ER-to-Golgi transport.

   Evidence cDNA cloning and in vitro ER-Golgi transport assay with biochemical co-immunoprecipitation of a Golgi SNARE complex

   PMID:8638159

   Open questions at the time

   • Did not resolve the full subunit composition of the functional fusion complex
   • No structural model of the SNARE bundle
2. 1997 High

   Showed how GS28-containing complexes are recycled, defining the enzymatic logic of complex disassembly.

   Evidence Co-IP from Golgi extracts with ATP-hydrolysis inhibition and immobilized alpha-SNAP binding assays

   PMID:9325254

   Open questions at the time

   • Did not establish the kinetics or in vivo regulation of disassembly
   • Did not identify which assembled complex is the physiological NSF substrate
3. 2001 High

   Defined a specific four-SNARE complex (syntaxin 5/GS28/Ykt6/Bet1) for late ER-to-Golgi transport, identifying GS28's cognate partners at this step.

   Evidence Reciprocal co-immunoprecipitation plus in vitro transport assay with Ykt6 antibody inhibition

   PMID:11323436

   Open questions at the time

   • Did not distinguish which SNARE provides t- versus v-SNARE roles structurally
   • Stoichiometry of the complex not determined
4. 2002 High

   Identified a distinct GS28 complex (with GS15) for intra-Golgi transport and linked it to COPI traffic, showing GS28 operates in compositionally separate complexes at different transport steps.

   Evidence Co-IP, immuno-EM, siRNA knockdown and dominant-negative GS15 mutants

   PMID:12388752

   Open questions at the time

   • Mechanism of complex switching between Bet1- and GS15-containing forms unknown
   • Did not define how COPI selects this complex
5. 2002 High

   Revealed a regulatory checkpoint protecting GS28 from premature t-SNARE pairing, distinguishing two separable NSF activities during Golgi reassembly.

   Evidence Cell-free Golgi cisternae assembly assay with NSF comatose mutant and biochemical GATE-16 binding assays

   PMID:12070132

   Open questions at the time

   • How GATE-16 release is timed to permit fusion not resolved
   • Structural basis of GATE-16/GS28 interaction unknown
6. 2004 High

   Extended the GS15-containing complex to a new transport route, showing the same four-SNARE assembly drives endosome-to-TGN retrograde transport.

   Evidence In vitro STxB retrograde transport assay with SNARE-specific antibodies plus siRNA knockdown in HeLa cells

   PMID:15215310

   Open questions at the time

   • Did not identify the upstream tethering factors directing this complex to the retrograde route
   • Regulation distinguishing anterograde versus retrograde use of the same complex unclear
7. 2009 Medium

   Tested the physiological requirement for GS28 in a whole organism, revealing functional redundancy with Ykt6 in intra-Golgi transport and development.

   Evidence C. elegans deletion mutants, synthetic-lethal RNAi screen and epistasis analysis

   PMID:19624756

   Open questions at the time

   • Molecular basis of GS28/Ykt6 redundancy not biochemically defined
   • Mammalian relevance of the redundancy not tested
8. 2011 Medium

   Identified a post-translational control of GS28 abundance, linking oxysterol/ORP7 signaling to GATE-16 sequestration and proteasomal turnover of GS28.

   Evidence Yeast two-hybrid, BiFC, truncation mapping, siRNA/overexpression and proteasome inhibitor experiments

   PMID:21669198

   Open questions at the time

   • E3 ligase mediating GS28 degradation not identified
   • Single lab; physiological context of oxysterol regulation untested
9. 2011 Low

   Proposed a non-trafficking protective role for GS28 against oxidative necroptotic death via p38 MAPK suppression.

   Evidence siRNA knockdown with p38 inhibitor and necrostatin-1 in glutathione-depleted SK-N-SH cells

   PMID:21860593

   Open questions at the time

   • No direct binding or biochemical link between GS28 and the RIP1/p38/ROS axis
   • Indirect pathway placement; single lab, not independently confirmed
10. 2012 Medium

    Uncovered a moonlighting role for GS28 in the DNA-damage response, showing it stabilizes p53 by blocking MDM2-mediated ubiquitination.

    Evidence Co-IP, shRNA knockdown, ubiquitination assay and p53-null rescue after cisplatin treatment

    PMID:22397410

    Open questions at the time

    • Whether the GS28-MDM2-p53 interaction is direct or Golgi-localized unclear
    • Single lab; structural basis of the trimeric complex unknown
11. 2013 Medium

    Linked GS28 sorting into COPI vesicles to Golgi architecture, showing its extraction from cisternae regulates inter-cisternal connectivity during intra-Golgi transport.

    Evidence Subcellular fractionation, in vitro intra-Golgi transport with vesicle re-addition, EM morphometry and auxin-inducible degron depletion of εCOP

    PMID:23387339

    Open questions at the time

    • Sorting signal that directs GS28 into COPI vesicles not defined
    • Single lab reconstitution
12. 2014 High

    Demonstrated in vivo conservation of GS28 t-SNARE function and the dispensability of its transmembrane domain for fusion via cross-species rescue.

    Evidence Drosophila gos28 loss-of-function mutants, SNARE-motif mutagenesis and transgenic rescue with human GOSR1

    PMID:25261468

    Open questions at the time

    • Did not test human GOSR1 in mammalian loss-of-function context
    • Did not resolve how transmembrane-anchorless GS28 supports fusion mechanistically

• How GS28's membrane-trafficking roles mechanistically intersect with its apoptotic and stress-protective functions, and whether the latter are direct, remains unresolved.
• No structural model of any GS28-containing complex
• Direct versus indirect basis of the MDM2-p53 and p38 connections unestablished
• No human disease link characterized in the corpus