Hsp70 Protein Family
Overview
The Hsp70 (Heat Shock Protein 70 kDa) family represents one of the most conserved and functionally important groups of molecular chaperones in all living organisms. These proteins play critical roles in protein homeostasis, cellular stress responses, and are increasingly recognized as important therapeutic targets in neurodegenerative diseases. Hsp70 family members are essential for preventing protein aggregation, refolding misfolded proteins, and targeting damaged proteins for degradation [1].
<div class="infobox infobox-protein">
<table>
<tr><th colspan="2" style="background:#e8f4f8; text-align:center; font-size:1.1em;">Hsp70 Protein Family</th></tr>
<tr><td><strong>Protein Name</strong></td><td>Heat Shock 70 kDa Proteins (Hsp70)</td></tr>
<tr><td><strong>Gene Symbols</strong></td><td>HSPA1A, HSPA1B, HSPA2, HSPA5, HSPA8, HSPA9, HSPA14</td></tr>
<tr><td><strong>UniProt IDs</strong></td><td>P0DMV8, P0DMV9, P54652, P11021, P11142, P38646, Q8WW36</td></tr>
<tr><td><strong>PDB IDs</strong></td><td>4KCM, 3FZF, 2E88, 4FSY, 5E84</td></tr>
<tr><td><strong>Molecular Weight</strong></td><td>65-71 kDa</td></tr>
<tr><td><strong>Subcellular Localization</strong></td><td>Cytoplasm, ER (BiP/GRP78), mitochondria, nucleus</td></tr>
<tr><td><strong>Protein Family</strong></td><td>Hsp70 family, Hsp70 superfamily</td></tr>
<tr><td><strong>Brain Expression</strong></td><td>Neurons, astrocytes, microglia, oligodendrocytes</td></tr>
<tr><td><strong>Diseases</strong></td><td>[Alzheimer's Disease](/diseases/alzheimers-disease), [Parkinson's Disease](/diseases/parkinsons-disease), [ALS](/diseases/als), [Huntington's Disease](/diseases/huntingtons)</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:#ef9a9a">Amyotrophic Lateral Sclerosis</a></td>
</tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">623 edges</a></td>
</tr>
</table>
</div>
Introduction
The Hsp70 family consists of multiple isoforms with distinct cellular localizations and functions. In the human genome, there are 13 Hsp70 family members, each with specific roles in cellular homeostasis [2]. The most well-studied members include:
- HSPA1A/Hsp70-1: Stress-inducible Hsp70, major heat shock protein
- HSPA1B/Hsp70-2: Highly similar to HSPA1A, co-expressed
- HSPA2/Hsp70-2: Testis-specific, involved in spermatogenesis
- HSPA5/GRP78/BiP: Endoplasmic reticulum resident, essential for ER function
- HSPA8/HSC70: Constitutively expressed, involved in [autophagy](/mechanisms/autophagy-lysosome-pathway)
- HSPA9/GRP75/mtHsp75: Mitochondrial Hsp70, mitochondrial protein import
- HSPA14/LAP: Lysosome-associated Hsp70
Hsp70 proteins are ATP-dependent molecular chaperones that undergo large conformational changes during their functional cycle. They work in concert with co-chaperones from the Hsp40 (DnaJ) family and the Hsp70/Hsp90 organizing protein (HOP) to regulate their activity [3].
Structure
Hsp70 proteins have a characteristic two-domain architecture that enables their chaperone function:
Domain Architecture
| Domain | Residues | Function |
|--------|----------|----------|
| N-terminal ATPase domain | ~1-380 | Binds and hydrolyzes ATP, regulates substrate binding |
| Substrate-binding domain (SBD) | ~400-500 | Binds unfolded polypeptides |
| C-terminal lid | ~500-650 | Covers SBD, completes substrate sequestration |
Structural Features
- ATPase domain: Belongs to the actin-Hsp70 superfamily, undergoes large conformational changes
- Lateral pore: Allows substrate entry into SBD
- Allosteric coupling: ATP hydrolysis in N-domain triggers conformational changes in C-domain
- EEVD motif: C-terminal sequence (EEVD) for co-chaperone binding
- Substrate-binding pocket: Hydrophobic residues recognizeunstructured protein regions
ATP-bound state: Low substrate affinity, open conformation
Substrate binding: Induces ATP hydrolysis
ADP-bound state: High substrate affinity, closed conformation
Nucleotide exchange: ADP release, ATP binding releases substrateCo-chaperone Interactions
- Hsp40 (DnaJ): Delivers substrates, stimulates ATP hydrolysis
- HOP (Hsp70/Hsp90 Organizing Protein): Bridges Hsp70 and Hsp90
- BAG family: Nucleotide exchange factors
- Hsp110: Nucleotide exchange factors, holdases
Normal Function
Core Chaperone Activities
| Function | Description | Mechanism |
|----------|-------------|-----------|
| De novo folding | Assists nascent protein folding | Co-translational substrate binding |
| Refolding | Rescues misfolded proteins | ATP-dependent unfolding/refolding |
| Protein degradation | Targets misfolded proteins to proteasome | Cooperation with CHIP ubiquitin ligase |
| translocation | Imports proteins into ER/mitochondria | Co-translational targeting |
| Disaggregation | Solubilizes protein aggregates | Cooperation with Hsp100/ClpB |
| Quality control | Prevents aggregation | Kinetic partitioning |
Cellular Processes
Stress response: Rapidly induced by heat, oxidative stress, toxins
Protein quality control: Surveys cellular protein homeostasis
Signal transduction: Chaperones signaling proteins
Transcription: Regulates steroid hormone receptors
DNA replication: Involved in replication machinery
[Autophagy](/entities/autophagy): HSC70 (HSPA8) involved in chaperone-mediated autophagyBrain-Specific Functions
In the central nervous system, Hsp70 family members serve specialized functions:
- Synaptic protein maintenance: Chaperones synaptic vesicles and receptors
- Axonal transport: Protects transport proteins
- Myelin maintenance: Supports oligodendrocyte function
- Neuroprotection: Reduces cellular stress
Role in Neurodegenerative Diseases
Hsp70 proteins are central to the pathogenesis of neurodegenerative diseases, which are characterized by protein misfolding and aggregation.
Alzheimer's Disease
Hsp70 family members play complex roles in AD pathogenesis:
- Reduces Aβ toxicity: Hsp70 chaperones Aβ oligomers, reducing their toxicity [4]
- Modulates aggregation: Prevents Aβ fibril formation
- Enhances clearance: Cooperates with [autophagy](/mechanisms/autophagy-lysosome-pathway) for Aβ clearance
- Cell surface Hsp70: Mediates Aβ internalization and degradation
Tau Pathology
- [Tau](/proteins/tau) binding: Directly interacts with hyperphosphorylated tau
- Prevents aggregation: Inhibits tau oligomerization
- Promotes degradation: Targets tau for proteasomal/autophagic clearance
- HSPA8 role: Critical in tau clearance pathways
Synaptic Function
- Synaptic protection: Maintains synaptic protein homeostasis
- Preserves LTP: Hsp70 activity supports [long-term potentiation](/mechanisms/long-term-potentiation)
- Reduces spine loss: Protects [dendritic spines](/mechanisms/dendritic-spines)
Therapeutic Implications
- Hsp70 levels are reduced in AD brain
- Enhancing Hsp70 is protective in animal models
- Hsp70 inducers are in development
Parkinson's Disease
Hsp70 is particularly important in PD due to its role in [alpha-synuclein](/proteins/alpha-synuclein) clearance:
Alpha-Synuclein Handling
- Direct interaction: Binds to [α-synuclein](/proteins/alpha-synuclein) aggregates [5]
- Prevents oligomerization: Inhibits toxic oligomer formation
- Promotes degradation: Targets α-syn for autophagic clearance
- Modulates aggregation: Redirects aggregation pathway
Mitochondrial Protection
- Mitochondrial Hsp75 (HSPA9): Protects dopaminergic [neurons](/entities/neurons)
- Mitophagy: Essential for mitochondrial quality control
- Oxidative stress: Reduces [ROS](/entities/reactive-oxygen-species)-induced damage
LRRK2 Interaction
- LRRK2 chaperone: Hsp70 assists in LRRK2 folding
- Mutant LRRK2: May overwhelm chaperone systems
Amyotrophic Lateral Sclerosis (ALS)
Hsp70 dysfunction contributes to motor neuron degeneration:
- Aggregate clearance: Insufficient to handle mutant protein aggregates
- Mutant SOD1: Hsp70 binds mutant SOD1 aggregates
- [TDP-43](/mechanisms/tdp-43-proteinopathy) pathology: Hsp70 involved in TDP-43 clearance
- Therapeutic target: Enhancing Hsp70 is protective
Huntington's Disease
Hsp70 plays important roles in [huntingtin](/proteins/huntingtin) handling:
- Mutant huntingtin: Hsp70 modulates aggregation
- Transcriptional regulation: Assists mutant HTT function
- Axonal transport: Protects transport machinery
- Synaptic function: Maintains striatal synapse
Frontotemporal Dementia
- Tau clearance: Hsp70 promotes tau degradation
- FUS pathology: Hsp70 handles FUS aggregates
- TDP-43: Involved in TDP-43 clearance
Molecular Mechanisms
Hsp70 operates in sophisticated protein quality control networks:
Substrate recognition: Hydrophobic patch detection
ATP-dependent cycling: Allosteric regulation
Co-chaperone coordination: Hsp40 delivery, nucleotide exchange
Handoff to degradation: CHIP-mediated ubiquitination
Aggregate disassembly: Cooperation with Hsp100Signaling Pathway Interactions
Hsp70 interacts with multiple neuroprotective signaling pathways:
- [NF-κB](/entities/nf-kb) pathway: Hsp70 inhibits NF-κB activation
- JNK pathway: Hsp70 blocks pro-apoptotic JNK signaling
- p53 pathway: Modulates p53 function
- Heat shock factor 1 (HSF1): Hsp70 is HSF1 target, negative feedback
Proteostasis Networks
Hsp70 works with other chaperone systems:
- Hsp90 network: Cooperates in steroid receptor maturation
- Hsp60/Hsp10: Compartment-specific folding
- Proteasome: Directs substrates for degradation
- Autophagy: HSC70 in chaperone-mediated autophagy
Therapeutic Targeting
Hsp70 activation represents a promising therapeutic strategy for neurodegenerative diseases:
Clinical-Stage Approaches
| Approach | Agent | Status | Mechanism |
|----------|-------|--------|-----------|
| Hsp70 inducers | Geldanamycin derivatives | Preclinical | HSF1 activation |
| Hsp90 inhibitors | Geldanamycin, Radicicol | Preclinical | Hsp90 inhibition → Hsp70 induction |
| Small molecule activators | YM-1, others | Research | Direct Hsp70 activation |
| Gene therapy | AAV-Hsp70 | Preclinical | Overexpression |
Hsp90 Inhibitors
Hsp90 inhibitors are particularly promising because they:
- Block Hsp90's anti-apoptotic function
- Release HSF1 to induce Hsp70
- Degrade mutant oncoproteins
- Sensitize cancer cells (dual benefit in some cases)
Co-chaperone Modulation
- BAG inhibitors: Block nucleotide exchange
- Hsp40 agonists: Enhance substrate delivery
- CHIP modulators: Affect ubiquitination rates
Natural Compounds
Several natural compounds induce Hsp70:
- Curcumin: Moderate Hsp70 induction
- Resveratrol: SIRT1-dependent effects
- Celastrol: Potent HSF1 activator
- Ginsenosides: Modest induction
Animal Models
Key experimental models for studying Hsp70:
- Hsp70 knockout mice: Viable but stress-sensitive
- Hsp70 transgenic mice: Protected from neurodegeneration
- HSF1 knockout mice: Compromised stress response
- AD models: Hsp70 overexpression reduces pathology
- PD models: Hsp70 protects dopaminergic neurons
- ALS models: Hsp70 delays disease progression
Biomarker Potential
Hsp70 levels serve as biomarkers:
- Extracellular Hsp70 (eHsp70): Released under stress
- Hsp70 in CSF: Potential neurodegeneration marker
- Autoantibodies: Anti-Hsp70 in some diseases
Genetic Associations
- HSPA1A/HSPA1B polymorphisms: Linked to AD risk
- HSPA8 variants: Associated with PD
- HSPA9 mutations: Cause mitochondrial disease
See Also
- [Heat Shock Response Pathway](/mechanisms/heat-shock-response)
- [Protein Homeostasis Mechanisms](/mechanisms/protein-homeostasis)
- [Autophagy Pathway](/mechanisms/autophagy-lysosome-pathway)
- [Proteasome System](/mechanisms/ubiquitin-proteasome-system)
- [Alzheimer's Disease Mechanisms](/mechanisms/ad-mechanism-index)
- [Parkinson's Disease Mechanisms](/mechanisms/pd-mechanism-index)
- [Amyloid-Beta Protein](/proteins/amyloid-beta)
- [Alpha-Synuclein Protein](/proteins/alpha-synuclein)
- [Tau Protein](/proteins/tau)
- [Hsp90 Protein Family](/proteins/hsp90-protein-family)
- [Hsp40 Protein Family](/proteins/dnaj-proteins)
- [CHIP Protein (STUB1)](/proteins/chip-protein)
External Links
- [UniProt Hsp70 Family](https://www.uniprot.org/uniprotkb/ P0DMV8/entry) - Protein database
- [PDB: Hsp70 Structures](https://www.rcsb.org/search?q=Hsp70) - Structural data
- [AlphaFold: HSPA1A](https://alphafold.ebi.ac.uk/entry/P0DMV8) - Predicted structure
- [Hsp70 Database](http://www.pdbe.csic.es/hsp70/) - Hsp70 resources
References
[Unknown, Broadley SA, Hartl FU. The role of molecular chaperones in protein quality control and human disease. FEBS Letters. 2009;583(11):1766-1775 (2009)](https://doi.org/10.1016/j.febslet.2009.01.021)
[Unknown, Mayer MP, Bukau B. Hsp70 chaperones: Cellular functions and molecular mechanism. Cellular and Molecular Life Sciences. 2005;62(6):670-684 (2005)](https://doi.org/10.1007/s00018-004-4464-6)
[Unknown, Kampinga HH, Craig EA. The Hsp70 chaperone machinery: J proteins as drivers of functional specificity. Nature Reviews Molecular Cell Biology. 2010;11(8):579-592 (2010)](https://doi.org/10.1038/nrm2941)
[Unknown, Evans CG, Wisen S, Gestwicki JE. Heat shock proteins 70 and 90 inhibit early stages of amyloid beta-(1-42) aggregation in vitro. Journal of Biological Chemistry. 2006;281(44):33182-33191 (2006)](https://doi.org/10.1074/jbc.M606192200)
[Unknown, Auluck PK, Chan HY, Trojanowski JQ, Lee VM, Bonini NM. Hsp70 suppresses alpha-synuclein aggregation. Science. 2002;295(5556):865-868 (2002)](https://doi.org/10.1126/science.295.5556.865)
[Kakimura J, Kitabatake M, Kimura K, et al., Hsp70 and Hsp40 attenuate age-related activation of c-Jun N-terminal kinase and p38 MAPK. Aging Cell. 2007;6(6):745-751 (2007)](https://doi.org/10.1111/j.1474-9726.2007.00328.x)
[Unknown, Daugaard M, Rohde M, Jäättelä M. The heat shock protein 70 family: Highly homologous proteins with overlapping and distinct functions. FEBS Letters. 2007;581(19):3702-3710 (2007)](https://doi.org/10.1016/j.febslet.2007.05.039)