HSPH1 Human

What is HSPH1 and what are its primary cellular functions?

HSPH1 (also known as HSP105 or HSP110) belongs to the heat shock protein family. It functions as a high-molecular-weight chaperone protein expressed at constitutively low levels as a cytoplasmic α-isoform under normal conditions, with an inducible nuclear β-isoform appearing during cellular stress exposure .

HSPH1 serves dual critical functions in cellular stress response:

• During acute stress, it works with HSPA1 to promote recruitment of the 26S proteasome to translating ribosomes, facilitating protein degradation and resumption of protein synthesis during recovery

• During thermotolerance, HSPH1 partners with HSPA1 to maintain ubiquitylated nascent/newly synthesized proteins in a soluble state needed for efficient proteasomal clearance

This chaperone plays essential roles in protein quality control, particularly for nascent and newly synthesized proteins during proteotoxic stress conditions.

How is HSPH1 expressed in normal human tissues versus cancerous tissues?

Additionally, HSPH1 is detected in multiple human cell lines including MCF7, HeLa, Jurkat, and K-562 cells via Western blot analysis . In aggressive B-cell non-Hodgkin lymphomas (B-NHLs), HSPH1 expression positively correlates with disease aggressiveness .

What molecular interactions does HSPH1 participate in during cellular stress response?

HSPH1 engages in multiple protein-protein interactions during cellular stress responses that facilitate its chaperone functions:

• Interaction with HSPA1 and DNAJB1: HSPH1 forms functional complexes with these co-chaperones to maintain protein quality control during heat stress

• Physical association with oncoproteins: In aggressive B-NHLs, HSPH1 physically interacts with c-Myc and Bcl-6, favoring their expression and stabilization. This interaction has been demonstrated both in Namalwa cells and primary aggressive B-NHL samples

• Proteasome recruitment: During acute stress, HSPH1 works with HSPA1 to promote recruitment of the 26S proteasome to translating ribosomes, facilitating the degradation of misfolded nascent proteins

• Solubilization of ubiquitylated proteins: During thermotolerance, HSPH1 with HSPA1 maintains ubiquitylated nascent/newly synthesized proteins in a soluble state required for their efficient proteasomal clearance

These interactions collectively highlight HSPH1's role as a central coordinator in cellular stress response pathways.

How does HSPH1 inhibition affect lymphoma progression and what are the molecular mechanisms involved?

HSPH1 inhibition has demonstrated significant antilymphoma activity through complex molecular mechanisms:

When HSPH1 is silenced in aggressive B-NHL models, researchers observe concurrent downregulation of Bcl-6 and c-Myc oncoproteins . This downregulation produces significant growth delay in both in vitro and in vivo models. Notably, HSPH1-silenced Namalwa cells exhibited dramatically reduced tumorigenicity, with experimental evidence showing complete loss of tumor-forming ability when 10^4 cells were injected into mice .

The molecular mechanisms involve:

• Disruption of physical interactions: HSPH1 physically interacts with c-Myc and Bcl-6 in both Namalwa cells and primary aggressive B-NHLs. This interaction appears critical for maintaining the stability and expression of these oncoproteins

• Positive expression correlation: Expression levels of HSPH1 positively correlate with both c-Myc and Bcl-6 levels in primary aggressive B-NHL specimens, suggesting a regulatory relationship

• Chaperone-dependent stabilization: As a high-molecular-weight chaperone, HSPH1 likely provides stabilization to these lymphoma oncoproteins, protecting them from degradation pathways

These findings establish HSPH1 as a central regulator that simultaneously supports two key lymphoma oncoproteins, making it a valuable therapeutic target for aggressive B-NHLs.

What is the relationship between HSPH1 and thermotolerance in cancer progression?

HSPH1 plays a critical role in thermotolerance with significant implications for cancer progression:

Quantitative proteomics analysis has revealed selective upregulation of HSPH1 along with HSPA1 and DNAJB1 in MCF7 breast cancer cells acquiring thermotolerance . This adaptation provides cancer cells with enhanced survival mechanisms against proteotoxic stress conditions.

Key research findings include:

• Deletion impacts: Deletion of HSPH1 impedes both thermotolerance acquisition and esophageal tumor growth in mouse models, providing a potential explanation for the poor prognosis observed in digestive tract cancers with high HSPH1 expression

• Protein quality control: During thermotolerance, HSPH1 partners with HSPA1 to maintain ubiquitylated nascent/newly synthesized proteins in a soluble state required for their efficient proteasomal clearance

• Rapid stress recovery: The HSPH1-HSPA1-DNAJB1 complex facilitates rapid resumption of protein synthesis upon recovery from heat stress, providing cancer cells with adaptive advantages

• Stress resilience: Cancer cells with high HSPH1 expression demonstrate enhanced resistance to proteotoxic stress conditions, contributing to their aggressive phenotype and poor treatment response

This relationship between HSPH1 and thermotolerance provides compelling evidence for exploring HSPH1 as a cancer therapeutic target, particularly in cancers of the digestive tract.

How does HSPH1 contribute to co-translational protein quality control in normal versus cancer cells?

HSPH1 serves distinct functions in co-translational protein quality control between normal and cancer cells:

During acute stress in cancer cells, HSPH1 with HSPA1 promotes the recruitment of the 26S proteasome to translating ribosomes, positioning cells for rapid protein degradation and resumption of protein synthesis upon recovery . This mechanism becomes particularly critical in cancer cells that face constant proteotoxic stress due to elevated protein synthesis rates and genomic instability.

In thermotolerant cancer cells, HSPH1-HSPA1 complex maintains ubiquitylated nascent/newly synthesized proteins in a soluble state required for their efficient proteasomal clearance . This function prevents the toxic accumulation of protein aggregates that would otherwise trigger apoptotic pathways.

These differential activities highlight HSPH1's critical contribution to cancer cell survival under conditions that would normally be lethal to non-malignant cells.

What are the optimal antibodies and detection methods for studying HSPH1 in human samples?

Researchers investigating HSPH1 have several validated antibodies and detection methods available:

Recommended Antibodies:
Proteintech's 13383-1-AP polyclonal antibody has been extensively validated for multiple applications:

Technical Considerations:

• For IHC applications, antigen retrieval with TE buffer pH 9.0 is suggested, although citrate buffer pH 6.0 is a viable alternative

• The antibody targets human HSPH1 with observed molecular weight of 110 kDa (calculated: 97 kDa)

• For optimal results, antibody titration is recommended for each specific testing system

Storage and Handling:

• Store at -20°C in PBS with 0.02% sodium azide and 50% glycerol pH 7.3

• Stable for one year after shipment with proper storage

• Aliquoting is unnecessary for -20°C storage

When selecting detection methods, consider that HSPH1 expression varies between cellular compartments, with α-isoform predominantly cytoplasmic and β-isoform nuclear during stress conditions.

What experimental approaches are most effective for studying HSPH1's interaction with oncoproteins?

The following experimental approaches have proven effective for investigating HSPH1's interactions with oncoproteins such as c-Myc and Bcl-6:

1. Co-immunoprecipitation (Co-IP):

• Successfully demonstrated physical interaction between HSPH1 and both c-Myc and Bcl-6 in Namalwa cells and primary aggressive B-NHLs

• Use specific antibodies against HSPH1 (like 13383-1-AP) for pull-down followed by western blot detection of interacting oncoproteins

2. HSPH1 Silencing Studies:

• RNA interference (siRNA or shRNA) targeting HSPH1 reveals downstream effects on oncoprotein expression

• Silencing in aggressive B-NHL models showed concurrent downregulation of Bcl-6 and c-Myc

3. Expression Correlation Analysis:

• Immunohistochemistry and western blot analysis of HSPH1, c-Myc, and Bcl-6 in primary tumor samples

• Statistical analysis to determine correlation coefficients between expression levels

4. In Vivo Models:

• Xenograft models using HSPH1-silenced lymphoma cells

• Tumor growth monitoring and subsequent analysis of oncoprotein expression

• Injectable model using 10^4 cells demonstrated complete loss of tumorigenicity in HSPH1-silenced Namalwa cells

5. Proteomic Approaches:

• Quantitative proteomics to identify changes in protein interaction networks upon HSPH1 modulation

• SILAC or TMT-based quantitative methods provide robust data on protein-protein interactions

These approaches offer complementary insights into HSPH1's functional relationships with oncoproteins and can be tailored to specific research questions concerning HSPH1-oncoprotein interactions.

How can researchers effectively model HSPH1-dependent thermotolerance in experimental systems?

Researchers can employ several complementary approaches to model HSPH1-dependent thermotolerance:

1. Cellular Models of Thermotolerance:

• Utilize MCF7 breast cancer cells, which have been successfully used to study thermotolerance acquisition

• Protocol: Expose cells to sublethal heat stress (typically 42-43°C for 1-2 hours), followed by recovery at 37°C for 6-24 hours before subsequent lethal heat challenge

• Quantify survival rates between control and HSPH1-modulated cells

2. HSPH1 Genetic Manipulation:

• CRISPR/Cas9-mediated knockout or knockdown via RNAi

• Inducible systems allow temporal control of HSPH1 expression

• Compare thermotolerance acquisition between wild-type and HSPH1-depleted cells

3. Proteotoxic Stress Assessment:

• Monitor ubiquitylated protein clearance rates using cycloheximide chase experiments

• Analyze soluble versus insoluble protein fractions following heat stress

• Fluorescence recovery after photobleaching (FRAP) to measure protein dynamics

4. Tripartite Complex Analysis:

• Study formation and function of the HSPH1-HSPA1-DNAJB1 complex

• Proximity ligation assays to visualize complex formation in situ

• Sequential immunoprecipitation to isolate intact complexes

5. In Vivo Thermotolerance Models:

• Xenograft models using HSPH1-modulated cancer cells

• Compare tumor growth under normal conditions versus periodic hyperthermia treatment

• Esophageal cancer mouse models have demonstrated HSPH1 dependency

6. Quantitative Proteomic Analysis:

• Compare protein expression profiles between control and thermotolerant cells

• Focus on co-chaperone networks and proteasome recruitment factors

• Previously identified selective upregulation of HSPH1, HSPA1, and DNAJB1

These experimental approaches provide comprehensive insights into HSPH1's role in thermotolerance while offering translational relevance for therapeutic targeting.

How does HSPH1 expression correlate with clinical outcomes in different cancer types?

HSPH1 expression demonstrates significant correlations with clinical outcomes across multiple cancer types:

B-cell Non-Hodgkin Lymphomas (B-NHLs):

• HSPH1 expression increases with B-NHL aggressiveness

• Higher HSPH1 levels correlate with unfavorable clinical outcomes

• Expression positively correlates with lymphoma oncoproteins Bcl-6 and c-Myc

• HSPH1 inhibition results in significant antilymphoma activity in preclinical models

Digestive Tract Cancers:

• HSPH1 deletion impedes esophageal tumor growth in mouse models

• High HSPH1 expression correlates with poor prognosis in digestive tract cancers

• Positive IHC detection in colon, liver, and pancreatic cancers suggests widespread relevance

Other Cancer Types:

• HSPH1 is constitutively overexpressed in several cancer types including:

  • Breast cancer (detected in MCF7 cells)

  • Testicular cancer (positive IHC)

  • Leukemic cell lines (K-562, Jurkat)

The mechanism underlying poor prognosis appears linked to HSPH1's dual roles:

• Stabilization of critical oncoproteins like c-Myc and Bcl-6

• Enhanced thermotolerance providing stress resilience

• Improved protein quality control allowing cancer cells to manage proteotoxic stress

These correlations nominate HSPH1 as a potential prognostic marker and therapeutic target across multiple cancer types, with particularly strong evidence in aggressive B-NHLs and digestive tract malignancies.

What is the mechanism by which HSPH1 stabilizes oncoproteins in lymphoma and other cancers?

HSPH1 employs several molecular mechanisms to stabilize oncoproteins in lymphoma and other cancers:

1. Direct Physical Interaction:

• HSPH1 physically interacts with c-Myc and Bcl-6 oncoproteins

• This interaction has been demonstrated in both Namalwa cells and primary aggressive B-NHL specimens

• The physical binding likely shields these oncoproteins from recognition by the protein degradation machinery

2. Chaperone Activity:

• As a high-molecular-weight chaperone protein, HSPH1 assists in proper protein folding

• This activity prevents misfolding-triggered degradation of client oncoproteins

• HSPH1 can promote refolding of stress-denatured proteins, rescuing them from degradation

3. Proteasome Regulation:

• HSPH1 with HSPA1 influences proteasome recruitment and activity

• This regulatory function may selectively protect oncoproteins from proteasomal degradation

• Differential regulation of proteasome activity in cancer versus normal cells maintains oncoprotein levels

4. Co-chaperone Network:

• HSPH1 operates within a network including HSPA1 and DNAJB1

• This coordinated chaperone system provides comprehensive protection for client oncoproteins

• The network responds to cellular stress by increasing protection of critical proteins

5. Protein Solubility Maintenance:

• HSPH1-HSPA1 complex maintains ubiquitylated proteins in a soluble state

• This function may selectively apply to certain proteins including oncoproteins

• Preventing aggregation extends protein half-life and functional activity

This multifaceted stabilization mechanism explains why HSPH1 inhibition results in concurrent downregulation of Bcl-6 and c-Myc, leading to significant antilymphoma activity in preclinical models . The positive correlation between HSPH1 expression and levels of these oncoproteins in primary tumors further supports this mechanistic relationship.

What therapeutic approaches targeting HSPH1 are being investigated for cancer treatment?

Several therapeutic approaches targeting HSPH1 are under investigation for cancer treatment, with promising preclinical results:

1. RNA Interference Technology:

• siRNA and shRNA approaches have successfully demonstrated HSPH1 silencing effects

• HSPH1 silencing in aggressive B-NHL models resulted in:

  • Downregulation of Bcl-6 and c-Myc oncoproteins

  • Significant growth delay in vitro

  • Loss of tumorigenicity in vivo when 10^4 cells were injected into mice

2. Small Molecule Inhibitors:

• Compounds targeting the ATPase domain of HSPH1

• Rational drug design based on crystal structure information

• Focus on disrupting HSPH1's chaperone function and protein-protein interactions

3. Antibody-Based Approaches:

• Specific antibodies against HSPH1 have shown therapeutic activity

• Previous research demonstrated significant therapeutic activity against human aggressive B-NHLs in vivo using HSPH1-specific antibodies

4. Combination Therapies:

• HSPH1 inhibition combined with conventional chemotherapy

• Targeting both HSPH1 and its client oncoproteins (c-Myc, Bcl-6)

• Exploiting synthetic lethality with other stress response pathways

5. Cancer-Specific Targeting:

• Focus on cancers with demonstrated HSPH1 dependency:

  • Aggressive B-NHL subtypes

  • Esophageal cancer

  • Other digestive tract malignancies

Research indicates HSPH1 inhibition provides significant antilymphoma activity, confirming its candidacy as a valuable therapeutic target for aggressive B-NHLs . Additionally, HSPH1 deletion impedes esophageal tumor growth in mice, providing rationale for therapeutic targeting in digestive tract cancers with high HSPH1 expression .

These approaches represent promising avenues for cancer therapy, particularly for malignancies with poor prognosis and limited treatment options.

What are the latest findings regarding HSPH1's role in protein quality control during cellular stress?

Recent research has uncovered sophisticated mechanisms through which HSPH1 orchestrates protein quality control during cellular stress:

Dual Functions During Stress Response:
Recent work has revealed that HSPH1 performs distinct yet complementary functions during different phases of heat stress response:

• Acute Stress Phase: HSPH1 collaborates with HSPA1 to promote recruitment of the 26S proteasome to translating ribosomes. This strategic positioning prepares cells for rapid protein degradation and subsequent resumption of protein synthesis upon recovery

• Thermotolerance Phase: During this adaptation period, HSPH1 partners with HSPA1 to maintain ubiquitylated nascent/newly synthesized proteins in a soluble state, which is critical for their efficient proteasomal clearance

Co-translational Quality Control:
New findings highlight HSPH1's involvement in co-translational quality control processes:

• Preferential protection of nascent and newly synthesized proteins during stress conditions

• Direct association with translating ribosomes to monitor protein synthesis

• Triage function that determines which nascent chains undergo degradation versus refolding

Proteotoxic Stress Management:

• The fraction of peri-translationally degraded proteins dramatically increases under proteotoxic stress conditions

• HSPH1 plays a central role in managing this elevated burden of potentially misfolded proteins

These discoveries provide mechanistic insight into how HSPH1 upregulation contributes to cancer cell survival under conditions of chronic proteotoxic stress, explaining its association with aggressive disease phenotypes and poor clinical outcomes in multiple cancer types.

How do recent proteomics studies inform our understanding of HSPH1 interaction networks?

Recent proteomics studies have revealed extensive HSPH1 interaction networks with significant implications for cancer biology and cellular stress response:

Selective Upregulation in Thermotolerance:
Quantitative proteomics analysis has identified selective upregulation of a specific chaperone network during thermotolerance acquisition:

• HSPH1 upregulation occurs alongside HSPA1 and DNAJB1 in MCF7 breast cancer cells developing thermotolerance

• This tripartite complex forms a functional unit that coordinates protein quality control during cellular stress

Interaction with Ubiquitin-Proteasome System:
Proteomics studies have mapped HSPH1's extensive interactions with components of the ubiquitin-proteasome system:

• Direct physical associations with the 26S proteasome during acute stress

• Connections with E3 ubiquitin ligases that target nascent/newly synthesized proteins

• Interactions with deubiquitinating enzymes that provide regulatory control

Cancer-Specific Interaction Network:
Comparison of HSPH1 interactomes between normal and cancer cells reveals:

• Expanded interaction network in cancer cells

• Cancer-specific interactions with oncoproteins including c-Myc and Bcl-6

• Differential association with translational machinery components

Quantitative Analysis of Protein Degradation:
Proteomics approaches have enabled quantitative assessment of HSPH1's impact on:

• Protein half-lives during stress conditions

• Proportion of nascent chains undergoing co-translational degradation

• Efficiency of proteasomal clearance in HSPH1-high versus HSPH1-low cells

These proteomics insights provide a systems-level understanding of how HSPH1 orchestrates complex cellular responses to stress, particularly in cancer contexts where proteotoxic stress is chronic and demands continuous adaptation.

What contradictions or unresolved questions exist in current HSPH1 research literature?

Several significant contradictions and unresolved questions persist in HSPH1 research:

1. Tissue-Specific Functions:

• Whether HSPH1 serves different functions in different tissue types remains unclear

• Some evidence suggests tissue-specific interaction partners, but comprehensive comparison across tissues is lacking

• Whether targeting HSPH1 would produce different outcomes across cancer types requires further investigation

2. Isoform-Specific Activities:

• HSPH1 exists as both cytoplasmic α-isoform and nuclear β-isoform

• Current literature inadequately distinguishes the functions of these isoforms

• Whether these isoforms interact with different protein partners or serve distinct cellular functions remains unresolved

3. Therapeutic Targeting Challenges:

• Uncertainty regarding potential toxicity of HSPH1 inhibition in normal tissues

• Contradictory evidence about whether complete vs. partial inhibition is preferable

• Unresolved questions about resistance mechanisms that might emerge after HSPH1 targeting

4. Relationship with Other HSPs:

• The functional redundancy between HSPH1 and other HSP family members

• Whether compensatory upregulation of other HSPs occurs after HSPH1 inhibition

• How the complex interplay between different HSPs affects therapeutic outcomes

5. Methodological Discrepancies:

• Different experimental models yield varying results regarding HSPH1 dependency

• Inconsistencies in detection methods and antibody specificity create data interpretation challenges

• Lack of standardized protocols for assessing HSPH1's chaperone activity

6. Regulatory Mechanisms:

• The precise mechanisms controlling HSPH1 expression in cancer remain incompletely understood

• Whether HSPH1 upregulation is a cause or consequence of malignant transformation

• The role of post-translational modifications in regulating HSPH1 activity

Addressing these unresolved questions requires collaborative research efforts combining diverse methodological approaches and model systems. Resolving these contradictions will be crucial for translating HSPH1 research into effective therapeutic strategies.

What are the most promising future directions for HSPH1 research in cancer biology?

The most promising future directions for HSPH1 research in cancer biology span several interconnected domains:

Therapeutic Development:

• Refinement of selective HSPH1 inhibitors with minimal off-target effects

• Development of cancer-specific delivery mechanisms for HSPH1-targeting agents

• Identification of optimal combination therapies that exploit HSPH1 dependency

Precision Medicine Applications:

• Validation of HSPH1 as a prognostic biomarker across cancer types

• Identification of patient subgroups most likely to benefit from HSPH1-targeted therapy

• Integration of HSPH1 expression data into comprehensive molecular tumor profiling

Mechanistic Investigations:

• Further elucidation of how HSPH1 differentially regulates protein stability in cancer versus normal cells

• Deeper understanding of HSPH1's role in maintaining proteostasis during therapy-induced stress

• Exploration of metabolic dependencies linked to HSPH1 activity in cancer cells

Resistance Mechanisms:

• Investigation of potential resistance mechanisms to HSPH1-targeted therapies

• Characterization of adaptive responses following HSPH1 inhibition

• Strategies to prevent or overcome resistance to HSPH1 targeting

Expanded Cancer Applications:

• Extension of HSPH1 research beyond B-NHL and digestive tract cancers

• Investigation of HSPH1's role in therapy-resistant cancer stem cells

• Exploration of HSPH1's contribution to metastatic progression

These directions build upon established findings that HSPH1 inhibition provides significant antilymphoma activity and that HSPH1 deletion impedes esophageal tumor growth . By pursuing these research avenues, investigators can translate fundamental insights about HSPH1 biology into novel therapeutic strategies with the potential to improve outcomes for patients with aggressive malignancies.

How might HSPH1 research contribute to improved diagnostic and therapeutic approaches for aggressive cancers?

HSPH1 research holds substantial promise for transforming diagnostic and therapeutic approaches for aggressive cancers in several ways:

Diagnostic Innovations:

• Development of HSPH1-based diagnostic assays that assess both expression levels and functional activity

• Integration of HSPH1 assessment into comprehensive molecular profiling panels

• Use of HSPH1 expression patterns to identify high-risk patient subgroups in lymphomas and digestive tract cancers

Prognostic Stratification:

• Utilization of HSPH1 expression as a biomarker for risk stratification

• Development of multiparameter prognostic models incorporating HSPH1 status

• Identification of HSPH1-associated gene signatures with prognostic value

Therapeutic Targeting:

• Design of small molecule inhibitors specifically targeting HSPH1's chaperone function

• Development of antibody-drug conjugates directed against HSPH1

• Creation of strategies to disrupt the HSPH1-HSPA1-DNAJB1 complex

Combination Therapies:

• Identification of synergistic combinations with conventional chemotherapeutics

• Integration with immunotherapy approaches

• Development of dual-targeting strategies against HSPH1 and its client oncoproteins

Resistance Management:

• Preemptive strategies to prevent adaptation to HSPH1 inhibition

• Sequential therapy approaches that anticipate and counter resistance mechanisms

• Monitoring of HSPH1 activity as a biomarker of treatment response