Heat Shock 70 kDa Protein 4 (HSPA4)

HSPA4 is a molecular chaperone belonging to the heat shock protein 70 (Hsp70) family (UniProt: P34932). These proteins function as ATP-dependent chaperones that assist in protein folding, unfolding, and disaggregation, playing critical roles in cellular proteostasis and stress response. HSPA4 is a 94 kDa protein expressed across multiple tissues and is involved in the maintenance of protein quality control pathways.

HSPA4 is implicated in neurodegenerative processes given its role in managing misfolded proteins—a hallmark of proteinopathic diseases. Heat shock proteins are increasingly recognized as protective factors in the brain, where their dysfunction can compromise cellular resilience against proteotoxic stress.

In Alzheimer's disease, HSPA4 is downregulated in post-mortem human brain tissue (Chaparral AD proteomics). Quantitative proteomic analysis of AD brain versus age-matched controls showed a mean log2 fold-change of −0.25 across measured subcellular fractions, indicating decreased HSPA4 abundance. This downregulation may reflect impaired proteostatic capacity in AD pathology and potentially contribute to the accumulation of misfolded tau and amyloid-β proteins characteristic of the disease.