EXOC3L1

Model summary

A cytoplasmic scaffold of the exocyst that organizes vesicle tethering and docking during exocytosis. By assembling a stable complex that positions secretory carriers at membrane-proximal cortical sites, it promotes efficient cargo delivery and supports regulated secretion of peptide hormones. Its elongated architecture recruits and stabilizes partner subunits and fusion machinery, concentrating at secretory granules and the cell cortex to drive vesicle capture prior to membrane fusion.

Predicted Gene Ontology terms

1. 01

   I begin with the InterPro architecture.

   The sequence is assigned to IPR010326 (Exocyst complex component EXOC3/Sec6 family) spanning residues 22–722, indicating the entire polypeptide adopts the Sec6/EXOC3 fold characteristic of the exocyst tethering complex. Within this scaffold, the C-terminal region is further specified by IPR042532 (Exocyst complex component EXOC3/Sec6, C-terminal domain homologous superfamily) from residues 551–715. This ordered layout—an extended Sec6-family body capped by a conserved C-terminal module—creates a rigid, elongated scaffold that nucleates multiprotein assemblies rather than catalysis. Such an architecture causes multivalent protein-protein interactions that stabilize large membrane-trafficking machines, directly supporting GO:0005515 protein binding as the molecular function.

2. 02

   A Sec6/EXOC3 scaffold dictates vesicle tethering and docking steps that precede membrane fusion.

   By stabilizing the octameric exocyst and positioning secretory carriers at defined cortical sites, this architecture drives GO:0006887 exocytosis. In endocrine and neuroendocrine contexts, the same tethering logic channels regulated secretion of peptide hormones; thus the scaffolded exocyst pathway causally contributes to GO:0030072 peptide hormone secretion by ensuring efficient delivery of dense-core vesicles to fusion-competent membrane domains.

3. 03

   The cellular context follows from the complex it builds.

   The Sec6-family signature and the terminal assembly domain place the protein within the GO:0000145 exocyst complex. Because exocyst assemblies operate at membrane-proximal cortical zones and at sites of vesicle docking, the protein concentrates at the GO:0005938 cell cortex and associates with GO:0030141 secretory granules during their tethering and maturation. This is consistent with a soluble cytoplasmic pool that is recruited to membrane-adjacent assemblies, matching the observed cytoplasmic localization and explaining dynamic enrichment at exocytic hotspots.

4. 04

   Mechanistically, the Sec6/EXOC3 scaffold forms a load-bearing arm that organizes other exocyst subunits and couples them to small GTPases and vesicle coats.

   I hypothesize that it binds fellow exocyst components to assemble the tether, and transiently engages Rab-family GTPases and SNARE machinery to choreograph vesicle capture and fusion. Likely partners include other exocyst subunits (to build the core octamer), exocyst-targeting GTPases that cue assembly, and vesicle fusion modules that execute the final membrane merger. Together, these interactions route secretory granules and hormone-containing vesicles to precise cortical sites where exocytosis is executed.