Progressive Supranuclear Palsy (PSP) is a 4R-tauopathy characterized by the accumulation of hyperphosphorylated tau protein in neurons and glia. The heat shock protein (HSP) chaperone system, which normally maintains protein homeostasis and prevents tau aggregation, becomes dysfunctional in PSP. This mechanism page examines how HSP70, HSP90, and HSP40 family members contribute to tau pathology in PSP and explores therapeutic strategies targeting these chaperones.
The cellular chaperone system provides the first line of defense against protein misfolding and aggregation[1]. In tauopathies like PSP, this system becomes overwhelmed or dysregulated, contributing to tau pathology progression.
HSP70 family proteins utilize an ATP-dependent mechanism to assist protein folding[2]. The cycle involves coordinated ATP binding, hydrolysis, and substrate release:
| Protein | Gene | Function in Tauopathy |
|---|---|---|
| Hsp70-1A (HSPA1A) | HSPA1A | Primary stress-inducible chaperone, prevents tau aggregation |
| Hsp70-1B (HSPA1B) | HSPA1B | Constitutive partner, compensates for HSPA1A |
| Hsp70-5/Grp78 (HSPA5) | HSPA5 | ER chaperone (BiP), ER stress response |
| Hsp70-8 (HSPA8) | HSPA8 | Constitutive chaperone, clathrin uncoating |
HSP90 specializes in maintaining metastable proteins, and tau is a known client[3]. This relationship is particularly relevant in PSP:
Several HSP90 inhibitors have been explored for neurodegenerative diseases[4]:
| Compound | Company | Status | Mechanism |
|---|---|---|---|
| Geldanamycin derivatives | Various | Preclinical | ANS, induces HSP70 |
| 17-AAG (Tanespimycin) | NCI | Phase I/II | HSP90 blockade |
| 17-DMAG (Alvespimycin) | Kosan | Phase I | HSP90 blockade |
| PU-H71 | Samus | Preclinical | HSP90 isoform selective |
HSP40 (DNAJ) family proteins serve as co-chaperones that recruit substrates to HSP70 and stimulate its ATPase activity[5]:
| Protein | Gene | Specificity | Role in PSP |
|---|---|---|---|
| DNAJA1 | DNAJA1 | Broad | General protein folding |
| DNAJB1 | DNAJB1 | Broad | Stress response |
| DNAJB6 | DNAJB6 | Neurons | Suppresses aggregation |
| DNAJC3 | DNAJC3 | ER | ER stress response |
DNAJB6 is particularly notable for its ability to suppress tau aggregation in cellular models[6].
Molecular chaperones interact with tau through multiple mechanisms[7]:
The C-terminus of HSP70-interacting protein (CHIP/STUB1) links chaperone function to degradation[8]:
In PSP, CHIP-mediated degradation is often impaired, leading to tau accumulation.
Several factors contribute to HSP dysfunction in PSP[9]:
Recent studies have advanced our understanding of HSP dysfunction in PSP and identified new therapeutic approaches:
HSP70 Chaperone Biology
Yan et al. (2024) comprehensively reviewed the role of Hsp70 family chaperones in tauopathy, highlighting the therapeutic potential of targeting these proteins in PSP[10]. Key findings include the identification of specific HSP70 isoforms that preferentially interact with 4R tau, and the discovery of post-translational modifications that impair chaperone function in PSP.
HSP90 Inhibition in 4R-Tauopathies
Chen et al. (2024) demonstrated that HSP90 inhibition using novel small-molecule inhibitors significantly reduces tau pathology in 4R-tauopathy mouse models[11]. The study showed preferential efficacy against 3-repeat and 4-repeat tau aggregates, with reduced off-target effects compared to first-generation HSP90 inhibitors.
DNAJB6 in Tau Seed Propagation
Kim et al. (2024) used PSP patient-derived neurons to demonstrate that DNAJB6 suppresses tau seed propagation at the cellular level[12]. This finding has significant implications for developing gene therapy approaches targeting tau propagation in PSP.
Blood-Brain Barrier Penetrant HSP70 Inducers
Patel et al. (2025) developed novel small molecule HSP70 inducers that cross the blood-brain barrier and reduce tau burden in vivo[13]. These compounds represent a promising translational approach for PSP treatment.
Proteomic Analysis of HSP Networks
Gupta et al. (2024) performed comprehensive proteomic analysis of HSP-client networks in PSP brain tissue, revealing specific vulnerability patterns in the chaperone system[14]. The study identified novel HSP70 interactors specific to PSP pathology.
CHIP-Mediated Degradation
Hernandez et al. (2025) demonstrated that CHIP-mediated tau degradation is impaired in PSP due to TREM2-associated microglial dysfunction[15]. This finding links neuroinflammation to proteostasis failure in PSP.
Gene Therapy Advances
Liu et al. (2024) showed that AAV-mediated delivery of DNAJB6 suppresses tau aggregation in PSP mouse models[16]. This approach has progressed toward preclinical development.
Arimoclomol is a co-inducer that amplifies stress-induced HSP expression[17]:
Celastrol is a natural compound that induces HSP70 expression:
HSP90 inhibition leads to compensatory HSP70 induction[18]:
Viral vector-mediated chaperone delivery shows promise[12:1]:
Heat shock protein dysfunction connects to multiple PSP-related pathways:
Heat shock protein dysfunction plays a critical role in PSP pathogenesis. The HSP70/HSP90/HSP40 chaperone system, normally responsible for maintaining tau in a functional state, becomes overwhelmed or dysregulated in PSP. This leads to tau misfolding, aggregation, and accumulation. Therapeutic strategies targeting these chaperone systems—including HSP70 inducers, HSP90 inhibitors, and gene therapy approaches—represent promising disease-modifying strategies for PSP.
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