Hsc70-interacting protein

ST13 (Hsc70-interacting protein, Hip) is a 369-amino acid cochaperone that stabilizes the ADP-bound state of HSC70, facilitating substrate binding and protein folding through coordinated HSC70 interactions (UniProt: P50502). The protein acts as an oligomeric regulator of HSC70 ATPase activity, supporting proper protein folding in the cytoplasm and potentially contributing to broader cellular proteostasis mechanisms.

ST13 has been associated with Alzheimer's Disease in proteomic studies of post-mortem human brain tissue. Analysis of four subcellular fractions (P2, P3, S2, S3) from AD versus age-matched controls using TMT-labeled tandem mass spectrometry revealed an ambiguous direction of change, with a mean log2 fold-change of 0.0307 across two fractions (Chaparral AD proteomics). This minimal fold-change suggests relatively stable expression levels in AD brain tissue, though protein localization or post-translational modifications may vary across subcellular compartments.

The biological relevance of ST13 to neurodegeneration likely relates to proteostasis dysfunction in AD, where proper protein folding and clearance are compromised. Further investigation into subcellular-fraction-specific changes and potential interaction with amyloid-beta or tau may clarify its role in disease pathogenesis.