VPS37D

Model summary

A cytosolic ESCRT scaffold that assembles and stabilizes ESCRT-I to drive endosomal membrane remodeling. By organizing multivalent protein–protein interactions, it promotes intraluminal vesicle formation and multivesicular body biogenesis, supports autophagic membrane sealing, and enables endosomal and virus-induced budding. It operates as a soluble complex that transiently associates with endosomal membranes and contributes to extracellular vesicle pathways.

Predicted Gene Ontology terms

1. 01

   I begin with the domain architecture.

   The protein contains a single annotated module, IPR009851 (Modifier of rudimentary, Modr domain) spanning residues 22–182. This Modr fold is characteristic of ESCRT-I accessory subunits and creates a curved, helical scaffold that mediates multivalent protein–protein interactions. Its central placement and breadth across the polypeptide indicate that the entire molecule is optimized for assembling and stabilizing larger complexes rather than catalysis. This architecture causally enforces a binding-centric role, aligning with GO:0005515 protein binding as the primary molecular function.

2. 02

   A Modr-driven scaffold is well-suited to nucleate ESCRT-I assembly and to bridge upstream and downstream membrane-remodeling modules.

   By stabilizing ESCRT-I and coupling it to cargo/adaptor pathways, the scaffold drives endosomal membrane budding and intraluminal vesicle biogenesis. This mechanistic role directly produces multivesicular body assembly (GO:0036258). Because ESCRT-mediated scission underlies enveloped virus release, the same assembly logic supports viral budding via host ESCRT complex (GO:0039702). The Modr platform also interfaces with autophagic pathways that utilize ESCRT-dependent membrane sealing and vesicle maturation, accounting for macroautophagy (GO:0016236). Endosomal system organization is an emergent consequence of these membrane-remodeling activities, explaining endosome organization (GO:0007032).

3. 03

   The cellular context follows from the complex it builds and the membranes it services.

   ESCRT-I forms a cytosolic complex that transiently associates with endosomal membranes; thus the protein resides in and functions through the ESCRT I complex (GO:0000813) and at the endosome membrane (GO:0010008). Its role in generating intraluminal vesicles that seed extracellular vesicles rationalizes detection in extracellular exosome fractions (GO:0070062). The experimentally observed cytoplasmic/cytosolic localization is consistent with a soluble ESCRT scaffold that cycles onto endosomes.

4. 04

   Mechanistically, the Modr domain creates a high-affinity hub that recruits and stabilizes ESCRT-I subunits and couples them to upstream ubiquitin-dependent cargo selection and downstream membrane scission.

   I hypothesize that it binds core ESCRT-I components and transiently engages ESCRT-II/III recruiters to choreograph vesicle budding. Likely interaction partners include other ESCRT-I subunits and adaptors that bridge to endosomal cargo and autophagic membranes, collectively enabling MVB biogenesis, autophagosome–endosome fusion, and virus-induced budding.