DnaJ homolog subfamily A member 4

DNAJA4 (DnaJ homolog subfamily A member 4) is a 44.8 kDa co-chaperone protein belonging to the heat shock protein 40 (Hsp40) family (UniProt: Q8WW22). Members of this family function as molecular chaperones that facilitate protein folding and assist in preventing protein aggregation through their interaction with heat shock protein 70 (Hsp70). The protein is 397 amino acids in length and is expressed in human tissues.

DNAJA4 is involved in cellular stress response pathways and protein homeostasis maintenance. While UniProt records no documented disease associations for this protein, its role in protein quality control suggests relevance to neurodegenerative conditions characterized by proteostatic dysfunction.

DNAJA4 is downregulated in Alzheimer's disease brain tissue. Analysis of post-mortem AD brain compared to age-matched controls using quantitative proteomics (TMT-labeled, data-dependent acquisition across four subcellular fractions) revealed a mean log2 fold-change of −0.69 (Chaparral AD proteomics). This decreased expression may reflect compromised protein quality control capacity in the AD brain, potentially contributing to the accumulation of misfolded proteins characteristic of the disease.