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| Gene | [HSP90AA1](/genes/hsp90aa1) |
| UniProt | P07900 |
| Molecular Weight | ~90 kDa |
| Subcellular Localization | Cytosol, nucleus (constitutive), stress-inducible |
| Protein Family | Hsp90 family |
| Structure | N-terminal ATPase domain, middle domain, C-terminal dimerization domain |
| Brain Expression | [Neurons](/entities/neurons) (high), [astrocytes](/entities/astrocytes), [microglia](/cell-types/microglia-neuroinflammation) |
HSP90 (Heat Shock Protein 90, encoded by HSP90AA1) is a abundant molecular chaperone essential for cellular proteostasis. As a key component of the protein folding machinery, HSP90 stabilizes numerous client proteins involved in signaling, transcription, and cell survival. In the nervous system, HSP90 is particularly important for maintaining neuronal health and protecting against neurodegeneration.
HSP90 is unique among chaperones in that it preferentially targets signaling proteins and mutated proteins that are close to their native conformation. This makes it critically important for neurodegenerative diseases, where mutant proteins (such as mutant SOD1 in ALS, mutant tau in AD) are client proteins. HSP90 inhibitors are being actively investigated for cancer therapy and have shown promise in neurodegenerative disease models.
HSP90 has a distinctive multi-domain structure:
- N-terminal ATPase domain (~25 kDa): Binds and hydrolyzes ATP, the energy source for chaperone activity
- Middle domain (~35 kDa): Client protein binding site, connects ATP hydrolysis to substrate binding
- C-terminal dimerization domain (~12 kDa): Mediates HSP90 dimerization, required for function
- EEVD motif: Conserved C-terminal sequence for co-chaperone binding
The dimeric structure of HSP90 is essential for its function. The ATPase cycle involves:
- Open conformation: ATP binding induces dimer closure
- Closed conformation: ATP hydrolysis triggers client protein folding
- ADP release: Returns to open state for client release
HSP90 maintains proteostasis through:
- Client protein maturation: Helps fold signaling proteins, steroid receptors, kinases
- Complex assembly: Facilitates formation of multi-protein complexes
- Quality control: Targets misfolded proteins for degradation
- Stress protection: Rapidly upregulated under various stresses
In neurons, HSP90:
- Axonal transport: Associated with transport machinery
- Synaptic function: Regulates synaptic protein complexes
- Mitochondrial function: Protects mitochondrial proteins
- Neuroprotection: Guards against oxidative stress
In glia, HSP90:
- Astrocyte protection: Supports astrocyte function under stress
- Microglial signaling: Modulates inflammatory responses
- Oligodendrocyte support: Protects myelinating cells
HSP90 in Alzheimer's disease:
- Tau pathology: HSP90 co-localizes with tau tangles
- Client proteins: Helps fold APP and processing enzymes
- Therapeutic inhibition: HSP90 inhibitors reduce Aβ and tau pathology in models
- Compensatory upregulation: Increased HSP90 in AD brain
In Parkinson's disease:
- α-Synuclein: HSP90 affects aggregation of α-synuclein
- DJ-1 client: DJ-1 Parkinson's protein is an HSP90 client
- Mitochondrial protection: Protects against mitochondrial toxins
- Therapeutic potential: HSP90 modulators for PD
HSP90 in ALS:
- SOD1 mutants: HSP90 stabilizes mutant SOD1
- TDP-43 pathology: HSP90 in TDP-43 aggregation
- Therapeutic targeting: HSP90 inhibitors accelerate mutant SOD1 degradation
- In vivo effects: HSP90 inhibition extends lifespan in ALS models
In Huntington's disease:
- Mutant huntingtin: HSP90 affects mutant huntingtin aggregation
- Clearance enhancement: HSP90 inhibition promotes clearance
- Therapeutic potential: Combined approaches with autophagy enhancers
HSP90 is a major therapeutic target:
- Inhibitors: Geldanamycin derivatives (17-AAG, 17-DMAG) - in cancer trials
- Selective targeting: Brain-penetrant HSP90 inhibitors for neurodegeneration
- Combination therapy: HSP90 inhibition + autophagy enhancement
- Co-chaperone targeting: Hsp70/Hsp90 organizing protein (HOP) modulators
- Kampinga & Craig, The HSP70 chaperone machinery (2010)
- Luo et al., Hsp90 co-localizes with tau pathology (2007)
- B裹 et al., HSP90 inhibition in ALS models (2008)
- Waza et al., HSP90 inhibitors in neurodegeneration (2005)
- HSP90AA1 Gene — Encoding gene
- HSP70 Protein — Partner chaperone
- Molecular Chaperones — Related pathway
- Proteostasis — Protein quality control