Heat shock protein 90 alpha (HSP90AA1) (HSP90AA1)

Heat shock protein 90 alpha (HSP90AA1) is a stress-inducible molecular chaperone that plays a central role in the maturation, folding, and stability of a wide array of client proteins, including kinases, transcription factors, and steroid receptors (UniProt P07900). While its isoform HSP90 beta is constitutively expressed, HSP90 alpha is specifically upregulated in response to cellular stressors such as heat, hypoxia, and oncogenic transformation (NCBI Gene 3320). In the context of cancer, HSP90 alpha is frequently overexpressed and exists in a high-activity state, where it stabilizes mutated or overexpressed oncoproteins like HER2, BCR-ABL, and Akt, thereby promoting tumor cell survival and proliferation (PubMed: 23545567). Therapeutic strategies targeting HSP90 alpha primarily utilize small-molecule inhibitors that compete with ATP for binding to the N-terminal domain, effectively halting the chaperone cycle and marking client proteins for degradation via the ubiquitin-proteasome pathway (PubMed: 27545814). Despite its potential as a master switch for multiple oncogenic pathways, the clinical development of HSP90 inhibitors has been complicated by toxicities such as visual disturbances and liver damage, as well as the induction of a compensatory heat shock response (PubMed: 29123255). Furthermore, HSP90 alpha can be secreted into the extracellular space, where it promotes cell motility and wound healing, adding another layer of complexity to its biological role (PubMed: 25429110). Current research continues to explore isoform-specific inhibitors and C-terminal binders to improve the therapeutic index and overcome the limitations of first-generation pan-HSP90 inhibitors.

Other names

HSP90AHSP90AA1HSPC1HSPCAHSP86Heat shock 90kDa protein 1 alphaStress-induced HSP90

Inhibition of the N-terminal ATP-binding domain, which disrupts the chaperone cycle and leads to the proteasomal degradation of oncogenic client proteins (PubMed: 27545814).