HSP70 (Heat Shock Protein 70 / HSPA1A)

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HSP70 (Heat Shock Protein 70 / HSPA1A)

<table class="infobox infobox-protein">
<tr>
<th class="infobox-header" colspan="2">HSP70 (Heat Shock Protein 70 / HSPA1A)</th>
</tr>
<tr>
<td class="label">Gene</td>
<td>[HSPA1A](/entities/hspa1a)</td>
</tr>
<tr>
<td class="label">UniProt</td>
<td><a href="https://www.uniprot.org/uniprot/P0DMV8" target="_blank">P0DMV8</a></td>
</tr>
<tr>
<td class="label">PDB Structures</td>
<td><a href="https://www.rcsb.org/structure/4B9Q" target="_blank">4B9Q</a>, <a href="https://www.rcsb.org/structure/5NRO" target="_blank">5NRO</a>, <a href="https://www.rcsb.org/structure/2KHO" target="_blank">2KHO</a></td>
</tr>
<tr>
<td class="label">Molecular Weight</td>
<td>70 kDa</td>
</tr>
<tr>
<td class="label">Localization</td>
<td>Cytoplasm, nucleus (stress-induced)</td>
</tr>
<tr>
<td class="label">Protein Family</td>
<td>Heat shock protein 70 family (HSP70 superfamily)</td>
</tr>
<tr>
<td class="label">Diseases</td>
<td>[Alzheimer's Disease](/diseases/alzheimers), [Parkinson's Disease](/diseases/parkinsons-disease), [Huntington's Disease](/mechanisms/huntington-pathway), [ALS](/diseases/als), [FTD](/diseases/ftd)</td>
</tr>
<tr>
<td class="label">Associated Diseases</td>
<td><a href="/wiki/als" style="color:#ef9a9a">ALS</a>, <a href="/wiki/aging" style="color:#ef9a9a">Aging</a>, <a href="/wiki/als" style="color:#ef9a9a">Als</a>, <a href="/wiki/alzheimer" style="color:#ef9a9a">Alzheimer</a>, <a href="/wiki/amyotrophic-lateral-sclerosis" style="color:#e

...

HSP70 (Heat Shock Protein 70 / HSPA1A)

Pathway Diagram

Mermaid diagram (expand to render)

Introduction

Hsp70 (Heat Shock Protein 70 Hspa1A) is an important component in the neurobiology of neurodegenerative diseases. This page provides detailed information about its structure, function, and role in disease processes.

Overview

Heat Shock Protein 70 (HSP70) is a 70 kDa ATP-dependent molecular chaperone and a central node of the cellular proteostasis network. The human HSP70 family comprises at least 13 members, with HSPA1A (the major inducible form, also called HSP72 or HSP70-1) and HSPA8 (the constitutive form, also called HSC70 or HSP73) being the most relevant to neurodegeneration. HSPA1A is encoded by the HSPA1A gene on chromosome 6p21.33, within the major histocompatibility complex (MHC) class III region ([Saxena et al., 2025](https://doi.org/10.1002/nep3.68)).

HSP70 proteins are among the most highly conserved proteins across all domains of life and perform essential functions in protein folding, disaggregation, translocation, and degradation. In the context of neurodegeneration, HSP70 directly opposes the fundamental disease mechanism of [protein-aggregation](/mechanisms/protein-aggregation) — it binds to misfolded tau]/proteins/tau, [alpha-synuclein/proteins/[alpha-synuclein), [tdp-43](/proteins/tdp-43), [huntingtin](/proteins/huntingtin), and [sod1-protein](/proteins/sod1-protein) to prevent their aggregation, disaggregate existing fibrils, and facilitate clearance via the [ubiquitin-proteasome-system](/mechanisms/ubiquitin-proteasome-system) and [autophagy](/mechanisms/autophagy-lysosome-neurodegeneration) ([Kampinga & Bhatt, 2016](https://doi.org/10.1038/nrn.2016.31); [Bohush et al., 2019](https://doi.org/10.3390/ijms20205232)).

The decline of the heat shock response (HSR) with aging — and the consequent failure of HSP70-mediated proteostasis — is increasingly recognized as a convergent mechanism underlying aging-associated neurodegeneration. Conversely, pharmacological induction of HSP70 expression represents one of the most promising therapeutic strategies against protein misfolding diseases ([Kalmar & Greensmith, 2023](https://doi.org/10.3389/fnmol.2023.1230436)).

Structure and Mechanism

Domain Architecture

HSP70 proteins share a conserved three-domain architecture (~640 amino acids):

N-terminal Nucleotide-Binding Domain (NBD) (~40 kDa, residues 1–385):

ATPase domain with two lobes (I and II) forming a deep nucleotide-binding cleft
ATP hydrolysis drives the conformational cycle that powers substrate binding and release
Structurally homologous to actin and hexokinase

Substrate-Binding Domain (SBD) (~15 kDa, residues 393–507):

β-sandwich subdomain (SBDβ) containing the substrate-binding cleft
Recognizes hydrophobic peptide segments of 5–7 residues enriched in leucine, isoleucine, valine, and phenylalanine
Exposed in non-native proteins but buried in properly folded structures

C-terminal α-Helical Lid (~10 kDa, residues 508–641):

Five α-helices that act as a "lid" over the substrate-binding cleft
Open in the ATP-bound state (fast substrate on/off) → Closed in the ADP-bound state (tight substrate binding)
Contains the EEVD motif at the extreme C-terminus that mediates co-chaperone interactions (e.g., with Hop/STIP1 and [hsp90](/proteins/hsp90)

Allosteric Chaperone Cycle

The HSP70 chaperone cycle is driven by ATP hydrolysis and regulated by co-chaperones:

Substrate delivery: J-domain proteins (JDPs, e.g., DNAJB1, DNAJA1) capture misfolded substrates and deliver them to the open, ATP-bound form of HSP70

Substrate trapping: JDP binding stimulates ATP hydrolysis → ADP-bound HSP70 closes the lid, trapping the substrate

Substrate processing: Nucleotide exchange factors (NEFs), particularly HSP110 (HSPH1) family members, catalyze ADP→ATP exchange

Substrate release: ATP binding reopens the lid, releasing the substrate for refolding, or directing it to degradation via the [ubiquitin-proteasome-system](/mechanisms/ubiquitin-proteasome-system) (aided by co-chaperone CHIP/STUB1)

HSP70 vs. HSC70 (HSPA1A vs. HSPA8)

| Feature | HSPA1A (HSP70/HSP72) | HSPA8 (HSC70/HSP73) |
|---|---|---|
| Expression | Stress-inducible (heat, oxidative, proteotoxic) | Constitutive, abundant in [neurons](/entities/neurons) |
| Brain abundance | Low basal, highly upregulated by stress | High basal (~1% of total brain protein) |
| [tau-protein](/proteins/tau) affinity | Higher affinity for [tau](/proteins/tau) | Lower affinity but more abundant |
| Key role | Emergency proteostasis response | Housekeeping protein quality control |

In aging and neurodegeneration, HSF1 (heat shock factor 1) — the master transcription factor controlling HSPA1A induction — becomes impaired, leading to an inadequate heat shock response and failure to upregulate HSP70 when most needed ([Kalmar & Greensmith, 2023](https://doi.org/10.3389/fnmol.2023.1230436)).

Normal Function

Protein Folding and Quality Control

HSP70 is the central hub of the protein quality control network:

De novo folding: Assists co-translational and post-translational folding of ~15–20% of all newly synthesized proteins
Refolding: Rescues stress-denatured proteins to their native state
Disaggregation: Working with HSP110 and JDPs, the HSP70 disaggregation machinery can extract monomers from amyloid fibrils
Triage decision: Directs irreversibly misfolded proteins to proteasomal or autophagic degradation via CHIP E3 ubiquitin ligase
Membrane translocation: Facilitates protein import into [mitochondrial-dynamics](/entities/mitochondrial-dynamics) and the endoplasmic reticulum

Neuroprotective Functions

In [neurons](/entities/neurons), HSP70 provides multiple layers of protection:

Inhibits [apoptosis](/entities/apoptosis) by blocking caspase-9 activation at the apoptosome (prevents Apaf-1 oligomerization)
Suppresses [necroptosis](/mechanisms/necroptosis) and [pyroptosis](/mechanisms/pyroptosis) pathways
Reduces [oxidative-stress](/mechanisms/oxidative-stress) by stabilizing antioxidant enzymes
Maintains synaptic protein homeostasis

Role in Disease

Alzheimer's Disease

HSP70 directly counters the two hallmark pathologies of AD:

[Tau](/proteins/tau): The HSP70/HSP90 multichaperone complex buffers pathological tau]/proteins/tau through extensive intermolecular contacts that depend on tau's aggregation-prone repeat region ([Nachman et al., 2022](https://doi.org/10.1038/s41467-022-31396-z)). HSP70 facilitates:

Tau binding to [microtubules](/entities/microtubules) — preventing its release and subsequent aggregation
Degradation of hyperphosphorylated tau via CHIP-mediated ubiquitination
The HSPA1A isoform has higher affinity for tau than the constitutive HSPA8 ([Thompson et al., 2012](https://doi.org/10.1021/pr300498q))

[amyloid-beta](/proteins/amyloid-beta): HSP70 interacts with [Amyloid-Beta](/proteins/amyloid-beta) oligomers and modulates their aggregation:

Reduces [amyloid-beta](/proteins/amyloid-beta)-induced synaptic toxicity by binding prefibrillar intermediates
Cooperates with [clusterin](/proteins/clusterin) in extracellular protein quality control

Parkinson's Disease

HSP70 is a critical suppressor of [alpha-synuclein](/proteins/alpha-synuclein) pathology:

Fibril disaggregation: The HSC70/DnaJB1/Apg2 disaggregation machinery can completely reverse α-synuclein fibril aggregation, extracting monomer units directly from fibril ends ([Gao et al., 2021](https://doi.org/10.1038/s41467-021-25966-w))
Oligomer blockade: HSP70 directly blocks α-synuclein oligomerization via a noncanonical interaction site in its C-terminal domain ([Aprile et al., 2017](https://doi.org/10.1126/sciadv.1700568))
In vivo protection: Overexpression of HSP70 in α-synuclein transgenic mice significantly reduces high-molecular-weight and detergent-insoluble α ([Klucken et al., 2004](https://doi.org/10.1523/JNEUROSCI.5305-03.2004))

However, the disaggregation process can paradoxically generate spreading-competent toxic α-synuclein species — small oligomeric fragments released during HSP110-mediated disaggregation can serve as seeds for prion-like propagation ([Tittelmeier et al., 2020](https://doi.org/10.1038/s41380-020-0771-9)). This dual nature complicates therapeutic strategies.

ALS and FTD

HSP70 plays a protective role against [tdp-43-proteinopathy](/mechanisms/tdp-43-proteinopathy):

HSP70 co-phase separates with [tdp-43](/proteins/tdp-43) in [liquid-liquid-phase-separation](/mechanisms/liquid-liquid-phase-separation) condensates, maintaining them in a dynamic, liquid-like state and preventing pathological amyloid aggregation ([Gu et al., 2021](https://doi.org/10.1016/j.jmb.2021.167054))
HSP70 binds to the highly aggregation-prone transient α-helix of [tdp-43](/proteins/tdp-43) via its nucleotide-binding domain
HSPA1A and co-chaperone DNAJB2a promote clearance of [tdp-43](/proteins/tdp-43) aggregates upon HSF1 activation
In [sod1-protein](/proteins/sod1-protein)-ALS models, HSP70 overexpression delays disease onset and extends survival

Huntington's Disease

HSP70 suppresses polyglutamine aggregation by binding to expanded polyQ tracts in [huntingtin](/proteins/huntingtin)
Works cooperatively with HSP40 (DNAJB1) to maintain solubility of mutant [huntingtin](/proteins/huntingtin)
HSP70 upregulation reduces inclusion body formation and improves neuronal survival in HD models

Therapeutic Targeting

HSP70 Inducers (HSF1 Activators)

Pharmacological activation of the heat shock response to upregulate HSP70 expression:

| Compound | Mechanism | Status |
|---|---|---|
| Arimoclomol | HSF1 co-activator; amplifies the natural HSR | Phase 2/3 in ALS (SOD1); failed primary endpoint but subgroup benefits observed |
| 17-AAG / BIIB021 | [hsp90](/proteins/hsp90) inhibitor → compensatory HSP70 induction via HSF1 | Preclinical/Phase 1 in neurodegeneration |
| Geranylgeranylacetone (GGA) | HSF1 activator; oral bioavailable | Preclinical in AD and PD models |
| Celastrol | Natural product HSF1 activator | Preclinical; reduces α-synuclein and tau aggregation |
| BGP-15 | Co-inducer of HSP70; hydroximic acid derivative | Phase 2 for insulin resistance; preclinical for neuroprotection |

Direct HSP70 Modulators

YM-01 and JG-98: Allosteric modulators of HSP70 that shift the chaperone toward pro-degradation mode, enhancing clearance of tau via CHIP-mediated ubiquitination
MKT-077: Rhodacyanine dye that binds the NBD and promotes tau degradation; analog JG-48 has improved pharmacokinetic properties
SW02: HSP70 activator that enhances chaperone-mediated [autophagy](/entities/autophagy) of α-synuclein

Gene Therapy

AAV-mediated overexpression of HSPA1A or HSP110 in preclinical models provides neuroprotection
Challenges include achieving sufficient expression levels in target brain regions and the narrow therapeutic window between protective disaggregation and release of toxic species

Background

The study of Hsp70 (Heat Shock Protein 70 Hspa1A) has evolved significantly over the past decades. Research in this area has revealed important insights into the underlying mechanisms of neurodegeneration and continues to drive therapeutic development.

Historical context and key discoveries in this field have shaped our current understanding and will continue to guide future research directions.

References

Brain Atlas Resources

Allen Human Brain Atlas: [HSP70 expression search](https://human.brain-map.org/microarray/search/show?search_term=HSP70)
Allen Mouse Brain Atlas: [HSP70 search](https://mouse.brain-map.org/search/index.html?query=HSP70)
Allen Cell Type Atlas: [Transcriptomic cell type reference](https://portal.brain-map.org/atlases-and-data/rnaseq)
BrainSpan Developmental Transcriptome: [HSP70 developmental expression](https://www.brainspan.org/rnaseq/search/index.html?search_term=HSP70)

External Links

[HSP70 Family - Cell Signaling](https://www.cellsignal.com/contents/science-bucket/hsp70-family)
[HSP70 - UniProt](https://www.uniprot.org/uniprot/P0DMV8)
[Chaperone Therapy - NCT](https://clinicaltrials.gov/search?term=chaperone+neurodegeneration)

From the [SciDEX Exchange](/exchange) — scored by multi-agent debate

[Proteostasis Enhancement via APOE Chaperone Targeting](/hypothesis/h-5d943bfc) — <span style="color:#81c784;font-weight:600">0.70</span> · Target: HSPA1A

Pathway Diagram

The following diagram shows the key molecular relationships involving HSP70 (Heat Shock Protein 70 / HSPA1A) discovered through SciDEX knowledge graph analysis:

Mermaid diagram (expand to render)

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HSP70 (Heat Shock Protein 70 / HSPA1A)

HSP70 (Heat Shock Protein 70 / HSPA1A)

HSP70 (Heat Shock Protein 70 / HSPA1A)

HSP70 (Heat Shock Protein 70 / HSPA1A)

Pathway Diagram

Introduction

Overview

Structure and Mechanism

Domain Architecture

Allosteric Chaperone Cycle

HSP70 vs. HSC70 (HSPA1A vs. HSPA8)

Normal Function

Protein Folding and Quality Control

Neuroprotective Functions

Role in Disease

Alzheimer's Disease

Parkinson's Disease

ALS and FTD

Huntington's Disease

Therapeutic Targeting

HSP70 Inducers (HSF1 Activators)

Direct HSP70 Modulators

Gene Therapy

Background

References

Brain Atlas Resources

See Also

External Links

Related Hypotheses

Pathway Diagram