ST13 (suppression of tumorigenicity 13) encodes Hsp70 interacting protein (Hip), a cochaperone that regulates heat shock protein function. ST13 oligomers bind the ATPase domains of HSC70 molecules in an HSP40-dependent manner, stabilizing the ADP state of HSC70 to maintain high substrate affinity 1. This interaction facilitates protein folding and repair while regulating steroid receptor activity and cellular proliferation 1. During mitochondrial protein import stress, ST13 co-chaperones interact with the mitochondrial targeting signal of precursor proteins, enabling Hsp90-mediated buffering of precursor degradation and preservation of import competence 2. Clinically, ST13 polymorphisms (rs138335 and rs138337) associate with increased asthma exacerbation risk despite inhaled corticosteroid treatment, suggesting genetic variation in glucocorticoid signaling pathways contributes to variable therapeutic response 3. Additionally, ST13 SNP rs138344 shows female-specific association with ischemic stroke risk 4. In chr22 pancreatitis, St13 protects against arachidonic acid pathway dysregulation by stabilizing IRE1α-XBP1s signaling through Sdf2l1 binding 5. ST13 demonstrates tumor-suppressive properties in colorectal cancer models, with knockout exacerbating disease progression 6. These findings highlight ST13's multifaceted roles in protein homeostasis, endocrine signaling, and disease pathophysiology.