VPS51

VPS51 is a structural subunit of the GARP (Golgi-associated retrograde protein) tethering complex, together with Vps52, Vps53, and Vps54, where it mediates retrograde vesicle traffic from the early endosome back to the late Golgi (PMID:12446664). In humans it is shared between the heterotetrameric GARP and EARP complexes (with VPS52, VPS53, and either VPS54 or VPS50), and patient-derived loss-of-function mutations reduce complex assembly, misdistribute the cation-independent mannose 6-phosphate receptor, and cause lysosomal swelling, establishing VPS51 as essential for endosome-to-TGN and endosome-recycling trafficking (PMID:30624672). Mechanistically, an N-terminal helix of VPS51 (residues 18–30 in yeast) docks directly into a conserved groove of the SNARE Tlg1, linking the complex to SNARE-mediated tethering and fusion, although this binding sequence is dispensable for retrograde traffic in vivo (PMID:16420526). Beyond its core trafficking role, VPS51 supports selective autophagy and organelle homeostasis: its loss impairs autophagy-related protein levels and increases mitochondria-lysosome contact sites (PMID:40565173). Biallelic VPS51 mutations cause a severe neurodevelopmental disorder (PMID:30624672).

1. 2002 High

   Established VPS51 as a bona fide subunit of the GARP tethering complex and assigned its core cellular function in endosome-to-Golgi retrograde traffic, defining the protein's primary role.

   Evidence Genetic deletion, biochemical co-purification, and trafficking assays in yeast

   PMID:12446664

   Open questions at the time

   • Did not resolve how VPS51 contributes structurally within the four-subunit complex
   • Mechanism of vesicle tethering at the molecular level not defined
2. 2002 Medium

   Extended VPS51 function beyond retrograde traffic to selective autophagy, showing it cooperates with SNAREs Tlg1/Tlg2 to target cargo to the preautophagosomal structure.

   Evidence vps51Δ deletion, Cvt vesicle morphology analysis, and SNARE epistasis in yeast

   PMID:12446664

   Open questions at the time

   • Single lab; direct biochemical SNARE interaction not shown in this context
   • Whether autophagy role is conserved in mammals not addressed
3. 2006 High

   Provided the structural basis for VPS51's link to the fusion machinery by showing its N-terminal helix binds directly into a groove on the Tlg1 SNARE, while revealing this interaction is dispensable for retrograde traffic.

   Evidence X-ray crystallography of Tlg1–Vps51 peptide complex plus in vivo truncation assays in yeast

   PMID:16420526

   Open questions at the time

   • Functional role of the Tlg1 interaction if not retrograde traffic remains unexplained
   • Single lab; structure limited to a peptide rather than full complex
4. 2011 Medium

   Demonstrated conservation of the VPS51-containing GARP complex in metazoans and tied its loss to lysosomal morphology defects, broadening relevance beyond yeast.

   Evidence Genetic deletion, lysosomal morphology, yeast two-hybrid SNARE binding, and synthetic lethality in C. elegans

   PMID:21613545

   Open questions at the time

   • Direct VPS51-SNARE binding inferred from complex-level Y2H, not VPS51-specific
   • Single lab; mammalian validation pending
5. 2019 High

   Defined the human disease relevance and dual-complex membership of VPS51, showing it is shared between GARP and EARP and that its loss disrupts CI-M6PR distribution and lysosome morphology.

   Evidence Exome sequencing plus patient fibroblast biochemistry, immunofluorescence, and proteasome rescue assays

   PMID:30624672

   Open questions at the time

   • Mechanistic basis of the neurodevelopmental phenotype not resolved at the cellular level
   • How VPS51 partitions between GARP and EARP not quantified
6. 2019 Low

   Confirmed VPS51's essential in vivo trafficking role through an independent homozygous deletion in affected siblings.

   Evidence Whole exome sequencing and clinical genetics in two siblings

   PMID:31207318

   Open questions at the time

   • Genetic identification only, no independent biochemical mechanistic experiments
   • Trafficking consequences inferred rather than directly measured
7. 2025 Medium

   Connected VPS51 dysfunction to impaired autophagy protein homeostasis and altered inter-organelle communication, implicating mitochondria-lysosome contacts in disease pathology.

   Evidence Western blot, mRNA analysis, SWATH-MS proteomics, and live-cell imaging of mitochondria-lysosome contacts in patient fibroblasts

   PMID:40565173

   Open questions at the time

   • Single lab and single missense variant; causal chain from trafficking defect to contact-site increase not established
   • Whether altered contacts drive or follow the trafficking defect unresolved

• How loss of VPS51-dependent retrograde and recycling trafficking mechanistically produces the severe neurodevelopmental phenotype remains unresolved.
• No neuronal model linking trafficking defect to developmental outcome
• Relative contributions of GARP versus EARP dysfunction to disease not separated