Peptidyl-prolyl cis-trans isomerase A

Peptidyl-prolyl cis-trans isomerase A (PPIA) is a 18 kDa protein that catalyzes proline isomerization in peptides and oligoproteins (UniProt: P62937). Beyond its enzymatic function, PPIA exerts pleiotropic cellular effects: it acts as a chemotactic factor via BSG/CD147 receptor signaling, activates pro-inflammatory responses in endothelial cells through NF-κB and MAPK pathways, and regulates protein aggregate clearance by facilitating TARDBP assembly in hnRNP complexes. PPIA also modulates oxidative stress responses and negatively regulates MAP3K5/ASK1-mediated apoptosis.

PPIA is widely expressed and functions in immune and inflammatory contexts. UniProt records no explicit disease associations in its structured database (UniProt: P62937), though its pro-inflammatory and endothelial activation roles suggest potential relevance to vascular and neurovascular conditions.

In Alzheimer's Disease, PPIA shows ambiguous regulation across subcellular fractions in post-mortem AD brain versus age-matched controls (Chaparral AD proteomics). Mean log2 fold-change is 0.39, but direction varies by fraction, precluding a clear assignment of increased or decreased abundance. Further analysis of fraction-specific changes may clarify whether PPIA dysregulation contributes to AD pathophysiology or represents a consequence of neurodegeneration.