Prefoldin subunit 4

Prefoldin subunit 4 (PFDN4) is a 134-amino-acid chaperone protein that facilitates protein folding by binding nascent polypeptide chains and transferring target proteins to the cytosolic chaperonin complex (UniProt: Q9NQP4). It functions to promote proper folding of newly synthesized proteins in the crowded cellular environment where multiple competing pathways exist for nonnative proteins.

PFDN4 is a component of the prefoldin complex, which operates broadly in cytoplasmic protein quality control. No other tissue-specific diseases are annotated in UniProt for this protein.

In Alzheimer's Disease, PFDN4 is downregulated in post-mortem AD brain tissue compared to age-matched controls (mean log2 fold-change: −0.31; Chaparral AD proteomics). This downregulation was detected via TMT-labeled quantitative mass spectrometry across four subcellular fractions, suggesting reduced availability of this chaperone cofactor in AD brain, potentially impairing proteostasis capacity in the disease state.