C16orf62

Model summary

A soluble endosomal sorting scaffold that organizes cargo selection and carrier formation within the endomembrane system. By using an N-terminal recognition module and a C-terminal assembly platform, it builds multivalent complexes that bias membrane traffic away from lysosomal fusion and toward recycling and secretory routes. This scaffolding role supports endosomal transport and endocytic recycling and sustains surface delivery pathways that feed back to the plasma membrane, with transient participation in specialized granule systems.

Predicted Gene Ontology terms

1. 01

   I begin with the InterPro architecture.

   The polypeptide carries IPR060266 (VPS35 endosomal protein-sorting factor-like, N-terminal domain, residues 116–389), followed by IPR064019 (VPS35L, C-terminal domain, residues 407–963). These two structured modules are embedded within the broader family signature IPR029705 (VPS35 endosomal protein sorting factor-like, residues 6–962), which spans essentially the entire protein. This bipartite layout—an N-terminal cargo/adaptor-recognition module and a C-terminal assembly/scaffold module—defines a soluble endosomal sorting scaffold rather than a membrane enzyme. The absence of transmembrane segments and the presence of extended interaction surfaces causally enforce a role dominated by multivalent protein binding, aligning with GO:0005515 protein binding as the molecular function.

2. 02

   This scaffold architecture dictates endosomal transport logic.

   The N-terminal domain (IPR060266) typically mediates selective recognition of cargo/adaptor cues and small GTPase-bound coats, while the C-terminal domain (IPR064019) stabilizes higher-order assemblies that nucleate trafficking machines. Such assemblies bias membrane flux toward retrieval and recycling routes emanating from endosomes. This mechanistic bias explains participation in GO:0016197 endosomal transport and specifically in GO:0032456 endocytic recycling, where cargo is returned to the surface or redirected. The same scaffold can couple endosomal sorting to secretory and recycling pathways that feed back to the cell surface, rationalizing inclusion in GO:0006893 Golgi to plasma membrane transport as part of the broader recycling axis that sustains surface delivery.

3. 03

   Cellular placement follows from the soluble scaffold design and endosomal specialization.

   The protein operates on endosome-associated membranes and transient surface-bound assemblies, consistent with GO:0005768 endosome and GO:0005886 plasma membrane. Its soluble nature and endosomal sorting role place it broadly within the endomembrane system, where it can sample cargo-laden endosomes and recycle carriers. The presence in GO:0070820 tertiary granule and GO:0101003 ficolin-1-rich granule membrane suggests participation in specialized secretory granule pathways—likely through shared trafficking hubs that intersect endosomal and granule routes.

4. 04

   Mechanistically, the N-terminal VPS35-like domain captures cargo/adaptor signals and small GTPase-defined platforms, while the C-terminal domain assembles a trafficking core that biases membrane flow away from lysosomal fusion and toward recycling/exocytic itineraries.

   This architecture causes formation of a cytosolic coat-like scaffold that selects cargo and routes carriers. I hypothesize that it partners with other endosomal sorting factors to form a trimeric assembly that senses RAB-family GTPases and ARF-family switches, thereby tuning the balance between endosome-to-lysosome and endosome-to-plasma membrane traffic. Likely interaction partners include other endosomal sorting scaffolds and accessory adaptors that together choreograph cargo capture and vesicle budding.