Prefoldin subunit 5

Prefoldin subunit 5 (PFDN5) is a cochaperone protein that facilitates protein folding by binding nascent polypeptide chains and transferring target proteins to the cytosolic chaperonin complex. It also functions as a transcriptional repressor of the MYC oncogene (UniProt: Q99471). The protein is a component of the prefoldin complex, which operates broadly in cellular protein quality control and proteostasis pathways.

PFDN5 is expressed in multiple tissues and participates in general chaperone-mediated protein folding mechanisms. No disease associations are currently annotated in UniProt for this protein.

In Alzheimer's disease, PFDN5 is significantly downregulated in post-mortem AD brain tissue compared to age-matched controls (mean log2 fold-change: −0.32; Chaparral AD proteomics). This finding derives from TMT-labeled quantitative proteomics of four subcellular fractions from human brain samples. The consistent downregulation across the assayed fraction suggests a reduced capacity for protein folding assistance in AD pathology, which may contribute to the proteostatic stress implicated in neurodegeneration.