PDIA3 (Protein disulfide-isomerase A3) Summary

PDIA3 is a protein disulfide isomerase that catalyzes the formation, isomerization, and reduction or oxidation of disulfide bonds in client proteins, functioning as a chaperone for protein folding in the endoplasmic reticulum (UniProt: P30101). It is a core component of the major histocompatibility complex class I peptide loading complex, where it acts as an essential folding chaperone for TAPBP and assists in the dynamic assembly of MHC I complexes with antigens, thereby playing a crucial role in antigen presentation to cytotoxic T cells (UniProt: P30101).

PDIA3 is widely expressed in tissues with high protein synthesis and secretion demands, particularly in immune cells and antigen-presenting cells. UniProt contains no curated disease associations for PDIA3 in its primary annotation.

In Alzheimer's disease, PDIA3 shows an ambiguous direction of change across subcellular fractions in post-mortem human AD brain compared to age-matched controls (Chaparral AD proteomics). The mean log2 fold-change is 0.409, with differential regulation evident across the two fractions measured in this TMT-labeled, 4-fraction differential proteomics study, suggesting that PDIA3 abundance or localization may be altered in AD pathology in a compartment-dependent manner.