TMED1

TMED1 is a p24-family secretory pathway protein that functions as an adaptor linking ER/Golgi membrane organization to innate immune signalling (PMID:23319592, PMID:32614325). Its GOLD domain mediates self-association, forming salt-dependent homodimers independent of the coiled-coil region, and the crystal structure of this domain defines the residues required for oligomerization (PMID:34634369). Through the same GOLD domain, TMED1 engages the TIR domain of the IL-33 receptor ST2L and is required for optimal IL-33-induced IL-8 and IL-6 production (PMID:23319592). TMED1 also co-assembles with the ER-embedded ubiquitin ligase RNF26 together with TMEM43, ENDOD1, and TMEM33 in an ER-membrane complex that modulates cGAS-STING innate immune signalling (PMID:32614325). Evolutionary conservation of function is indicated in C. elegans, where the γ-subfamily paralogs tmed-1 and tmed-3 are genetically redundant and facilitate basement membrane breakdown during vulval development (PMID:37204056). Beyond these findings, no further mechanistic detail has been characterized in the available corpus.

1. 2013 Medium

   Established that TMED1 is not merely a housekeeping cargo receptor but a specific partner of an immune receptor, defining a role in cytokine signalling.

   Evidence Co-immunoprecipitation with domain deletion/mutation constructs mapping GOLD-TIR contacts, plus loss-of-function cytokine production assays

   PMID:23319592

   Open questions at the time

   • Single lab without reciprocal in vivo validation
   • Stoichiometry and subcellular site of the TMED1-ST2L interaction not resolved
   • Whether TMED1 traffics ST2L or scaffolds downstream signalling is unaddressed
2. 2020 Medium

   Placed TMED1 within a defined multiprotein ER-membrane complex, extending its immune role from IL-33 to the cGAS-STING axis.

   Evidence Comparative MS-based interaction mapping of ER ubiquitin ligases with functional innate immune signalling readouts

   PMID:32614325

   Open questions at the time

   • Single study; direct binary contacts within the RNF26/TMEM43/ENDOD1/TMEM33 complex not dissected
   • Whether TMED1 is a ubiquitination substrate or a structural subunit is unclear
   • Mechanism by which the complex modulates STING is not defined
3. 2021 High

   Provided the structural basis for TMED1 self-association, showing the GOLD domain alone drives salt-dependent homodimerization.

   Evidence X-ray crystallography of the GOLD domain with solution biophysics and molecular dynamics

   PMID:34634369

   Open questions at the time

   • Functional consequence of homodimerization for ST2L binding or complex assembly not tested
   • No full-length structure including the coiled-coil or transmembrane regions
4. 2023 Medium

   Demonstrated conserved developmental function via genetic redundancy, linking γ-subfamily TMEDs to basement membrane remodelling.

   Evidence C. elegans single and double mutant genetic analysis with phenotypic readouts of movement, vulval morphology, and basement membrane dynamics

   PMID:37204056

   Open questions at the time

   • Redundancy masks single-gene contribution; molecular cargo or mechanism not identified
   • Relevance to mammalian TMED1 immune functions not established

• How TMED1's structurally defined homodimerization integrates with its two distinct immune complexes (ST2L and the RNF26 ER complex) and its developmental role remains unresolved.
• No unifying model connecting cargo trafficking, immune signalling, and basement membrane remodelling
• No identified cargo substrate for mammalian TMED1
• Subcellular dynamics during signalling not mapped