Endoplasmic reticulum resident protein 44

ERP44 (endoplasmic reticulum resident protein 44) is a 406-amino acid protein that mediates thiol-dependent protein retention in the early secretory pathway through formation of mixed disulfides via its conserved CRFS motif (UniProt: Q9BS26). It also inhibits calcium channel activity of ITPR1 and plays a role in controlling oxidative protein folding within the endoplasmic reticulum, with documented functions in retaining ERO1A and ERO1B.

ERP44 is localized to the endoplasmic reticulum, a critical compartment for protein synthesis and quality control. UniProt lists no primary disease associations for this protein, though its role in ER protein folding and calcium signaling suggests potential relevance to neurodegenerative processes.

In Alzheimer's disease, ERP44 shows ambiguous regulation across brain fractions. Human post-mortem AD brain proteomics (TMT-labeled, 4 subcellular fractions) revealed a mean log2 fold-change of −0.0313 relative to age-matched controls (Chaparral AD proteomics), indicating minimal and inconsistent change across fractions. This near-zero fold-change suggests ERP44 is not substantially altered in AD pathology.