ERdj8 is a novel ER membrane protein that localizes to a meshwork-like ER subdomain with PIS and Atg proteins; it governs autophagosome size during formation, with overexpression enlarging autophagosomes (requiring the J and TRX domains) and ablation impairing engulfment of larger targets; the role is conserved in the C. elegans orthologue dnj-8.

UniProt predicts a single-pass type IV ER membrane topology with an N-terminal J domain and a thioredoxin domain; its curated function records that DNAJC16 regulates the size of autophagosomes during formation and that J-domain His-57 and thioredoxin Cys-171/Cys-174 residues are required for the autophagosome-enlargement activity.

Records that DNAJC16's core biological process is established, but the direct molecular function behind that process has not been demonstrated.

Records the current GO curation boundary: no molecular-function annotation should be asserted until the HSP70/co-chaperone or redox activity is experimentally shown.

A focused report found that DNAJC16 has no demonstrated HSP70 co-chaperone or thioredoxin-like redox activity despite the conserved J-domain and TRX-like domain architecture.

The report interprets UniProt's predicted type IV topology as placing DNAJC16's J domain on the cytoplasmic face of the ER and therefore excluding a direct ER-luminal BiP/HSPA5 partnership; this topology conflicts with the sole primary study's ER-luminal wording and remains unresolved.