HSPA5 Human
Description
Introduction to HSPA5 (Human)
HSPA5, also known as BiP (Binding Immunoglobulin Protein), GRP78 (78 kDa Glucose-Regulated Protein), or Heat Shock Protein Family A Member 5, is a 78 kDa molecular chaperone localized primarily in the endoplasmic reticulum (ER). It belongs to the HSP70 family and plays a critical role in ER homeostasis, protein folding, and stress response. HSPA5 is ubiquitously expressed in human tissues (Table 1) and is highly upregulated under conditions of ER stress, such as hypoxia, glucose deprivation, or viral infections .
2.2. Mechanism of Action
HSPA5 operates through an ATPase cycle:
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ATP-bound state: SBDα lid opens, allowing substrate release.
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ADP-bound state: SBDα lid closes, trapping substrates for folding or degradation .
Co-chaperones like PDI (Protein Disulfide Isomerase) and J proteins enhance its activity .
3.1. Core Functions in ER Homeostasis
3.2. Expression in Human Tissues
HSPA5 is expressed in all tissues, with notable abundance in:
| Tissue | Expression Level | Source |
|---|---|---|
| Liver | High | |
| Lung | High | |
| Pancreas | High | |
| Kidney | Moderate | |
| Normal vs. Cancer Tissues | Upregulated in 14/31 cancer types (e.g., bladder, pancreatic, lung) . |
4.1. Cancer
HSPA5 is a prognostic marker in multiple cancers:
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Bladder cancer: Promotes proliferation, metastasis, and VEGFA/VEGFR2 pathway activation; linked to poor prognosis .
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Pancreatic adenocarcinoma: Associated with reduced survival in neoadjuvant therapy patients .
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Mechanism: Enhances cell cycle progression (S-phase accumulation), inhibits apoptosis, and regulates ferroptosis .
4.2. COVID-19 and Viral Pathogenesis
HSPA5 acts as a potential co-receptor for SARS-CoV-2:
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Expression: HSPA5 mRNA levels are 253-fold higher than ACE2 in lung cancer tissues, suggesting enhanced viral entry .
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Clinical Impact: Elevated HSPA5 correlates with severe COVID-19 outcomes, particularly in cancer patients .
4.3. Metabolic Disorders
HSPA5 modulates lipid metabolism in nonalcoholic fatty liver disease (NAFLD):
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RNA binding: Interacts with mRNAs involved in lipid synthesis and AMPK signaling, influencing alternative splicing and gene expression .
5.1. Inhibitors and Clinical Relevance
| Target | Therapeutic Strategy | Application |
|---|---|---|
| ER stress modulation | Small-molecule inhibitors (e.g., KIRA6) | Cancer, COVID-19 |
| HSPA5 knockdown | siRNA/shRNA, CRISPR-Cas9 | Preclinical cancer models |
| cs-HSPA5 antibodies | Neutralizing antibodies | Viral entry blockade |
5.2. Emerging Research
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RNA interactions: HSPA5 binds lncRNAs and coding RNAs, regulating splicing and lipid metabolism in NAFLD .
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Senescence: Inhibits cisplatin-induced senescence in ovarian cancer, suggesting a dual role in chemoresistance .
Conservation Across Species
| Species | Conservation Status | Cysteine Residues |
|---|---|---|
| Human | Yes | 2 |
| Mouse | Yes | 2 |
| Rat | Yes | 3 |
| Cow | Yes | 2 |
| Drosophila melanogaster | Yes (Hsc70-3) | N/A |
| Saccharomyces cerevisiae | Yes (SSA1) | N/A |
Product Specs
Q&A
What is the molecular structure and function of human HSPA5?
HSPA5 is a 78 kDa member of the heat shock protein 70 family. The human HSPA5 protein consists of 654 amino acids, including an 18 amino acid signal sequence and a 636 amino acid mature region containing a hydantoinase A region (amino acids 145-245) . The protein contains a C-terminal KDEL motif present on intracellular HSPA5 but absent on secreted forms .
HSPA5 functions include:
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Acting as an ER chaperone for protein folding
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Participating in the unfolded protein response
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Maintaining cellular homeostasis under stress conditions
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When secreted extracellularly, inducing IL-10 production from T cells and interacting with Cripto to block TGF-beta signaling
What detection methods are most reliable for HSPA5 in experimental systems?
Multiple validated methods exist for detecting HSPA5 in research settings:
Western Blot Analysis:
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Human-specific detection: Use MAB4846 at 1 μg/mL with HRP-conjugated Anti-Mouse IgG Secondary Antibody
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Multi-species detection (human/mouse/rat): Use AF4846 at 0.5 μg/mL with HRP-conjugated Anti-Goat IgG Secondary Antibody
Simple Western™ Analysis:
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Human samples: HSPA5 detected at approximately 72-74 kDa using 5-10 μg/mL antibody concentration
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Use 12-230 kDa separation system
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Note: Non-specific interaction with the 230 kDa standard may occur with some antibodies
Immunohistochemistry:
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Effective for subcellular localization in tissue sections, particularly retinal tissues
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Can distinguish between extracellular and intracellular forms of the protein
How does HSPA5 expression vary across normal human tissues?
Expression analysis from multiple databases (GTEx, HPA, FANTOM5) reveals:
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Bone marrow exhibits the highest HSPA5 expression among normal tissues
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HSPA5 shows relatively low RNA tissue specificity across normal tissues
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In single-cell RNA analysis, HSPA5 exhibits limited cell-type specificity
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HSPA5 demonstrates weak cancer specificity in RNA cancer classification analyses
This limited tissue specificity suggests HSPA5 performs crucial functions across diverse cell types, consistent with its role in fundamental cellular processes like protein folding.
What methodological approaches are recommended when investigating HSPA5's role in cancer?
Based on comprehensive pan-cancer analyses, researchers should consider:
Multi-omics Integration Strategy:
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Transcriptomic data: Utilize TCGA datasets to analyze mRNA expression
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Proteomic verification: Incorporate CPTAC data to confirm translational changes
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Differential expression analysis: Compare HSPA5 levels between tumor and normal tissues using tools like TIMER2
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Validation in specific cancer types: Focus on cancers like BRCA, LIHC, and COAD for detailed investigation
Survival Analysis Protocol:
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Determine optimal cutoff values specific to each cancer type
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Generate Kaplan-Meier curves and survival heatmaps
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Analyze multiple survival metrics:
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Use R packages "survminer" and "survival" for statistical analysis
Functional Network Analysis:
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Construct protein-protein interaction networks using STRING
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Identify top 100 HSPA5-correlated genes using GEPIA2
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Perform KEGG pathway and GO enrichment analyses on combined datasets
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Conduct Gene Set Enrichment Analysis (GSEA) comparing high vs. low HSPA5 expression groups
How should researchers design experiments to study HSPA5's relationship with the immune system?
HSPA5 shows significant correlations with immune parameters requiring specific experimental approaches:
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Immune Checkpoint Correlation Studies:
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Comprehensive Immune Infiltration Analysis:
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Validation Experimental Design:
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Select representative cancer types spanning different tissue origins
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Perform immunohistochemistry to visualize HSPA5 and immune cell markers simultaneously
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Conduct flow cytometry analysis of tumor-infiltrating lymphocytes in relation to HSPA5 expression
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What systems genetics approaches can identify modulators of HSPA5 expression?
Research focusing on retinal HSPA5 illustrates effective systems genetic methods applicable across tissues:
Quantitative Trait Locus (QTL) Mapping:
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Utilize genetic reference panels (e.g., BXD family from C57BL/6J × DBA/2J mice)
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Apply stepwise refinement through:
Integration with Phenotypic Data:
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Connect molecular findings with disease-relevant phenotypes
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Incorporate datasets from repositories like GeneNetwork
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Model cellular responses and disease outcomes using high-throughput quantitative data
Validation Methodology:
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Confirm subcellular localization patterns through immunohistochemistry
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Compare expression between healthy and diseased tissues
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Assess functional consequences of candidate gene perturbation
How can researchers effectively study HSPA5's role in the unfolded protein response?
The UPR represents a complex signaling network requiring sophisticated experimental approaches:
Gene Ontology Enrichment Focus Areas:
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Response to ER stress
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Golgi vesicle transport
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Response to topologically incorrect proteins
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ER to Golgi vesicle-mediated transport
Experimental Design Recommendations:
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Analyze HSPA5 interactions with other UPR components:
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Assess protein quality control mechanisms:
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Utilize stress induction protocols:
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Chemical inducers (tunicamycin, thapsigargin)
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Physiological stressors (glucose deprivation, hypoxia)
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Monitor temporal dynamics of HSPA5 response
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What are the optimal antibody handling protocols for HSPA5 detection?
Based on validated antibody data:
Storage and Handling:
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Use a manual defrost freezer and avoid repeated freeze-thaw cycles
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Store for 12 months from receipt at -20 to -70°C as supplied
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After reconstitution, store for 1 month at 2 to 8°C or 6 months at -20 to -70°C under sterile conditions
Western Blot Optimization:
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Use reducing conditions consistently
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Determine optimal antibody dilutions empirically for each application
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Be aware that antibody MAB4846 is human-specific, while AF4846 detects human, mouse, and rat HSPA5
How should variations in HSPA5 detection across experimental platforms be interpreted?
HSPA5 can appear at different molecular weights depending on methodology:
| Detection Method | Observed Molecular Weight | Notes |
|---|---|---|
| Western Blot | 78-80 kDa | Standard reducing conditions |
| Simple Western™ | 72-74 kDa | Capillary-based immunoassay |
| Theoretical | 78 kDa | Based on amino acid sequence |
Researchers should consider that:
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Post-translational modifications may alter migration patterns
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Different detection systems can yield varying apparent molecular weights
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Alternative splicing in the signal sequence (aa 1-10) and multiple single amino acid substitutions can affect observed size
What experimental controls are essential when studying HSPA5 in disease states?
When investigating HSPA5 in pathological conditions:
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Expression Control Panel:
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Subcellular Fractionation Controls:
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Functional Validation Approaches:
How can researchers distinguish between specific HSPA5 functions in complex biological systems?
To delineate HSPA5's multiple roles:
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Domain-Specific Analysis:
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Localization-Based Functional Studies:
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Context-Dependent Protein Interaction Mapping:
Product Science Overview
HSPA5 is a multifunctional protein that primarily resides in the endoplasmic reticulum (ER). It is involved in:
- Protein Folding: HSPA5 assists in the proper folding of nascent proteins and the refolding of misfolded proteins, ensuring they attain their functional conformations.
- Calcium Homeostasis: It helps maintain calcium balance within the ER, which is vital for various cellular functions.
- ER Stress Response: HSPA5 is a key regulator of the unfolded protein response (UPR), a cellular stress response related to the ER. It helps cells cope with the accumulation of misfolded proteins by enhancing the protein-folding capacity of the ER and reducing the load of newly synthesized proteins .
HSPA5 has been implicated in various physiological and pathological processes:
- Embryonic Development: HSPA5 is essential for early embryonic development. It mediates retinoic acid signaling, which is crucial for the formation of pronephros, an early kidney structure in vertebrates .
- Cancer: HSPA5 is often overexpressed in cancer cells, where it supports their survival and proliferation. It has been identified as a potential target for cancer therapy due to its role in protecting cells from stress-induced apoptosis .
- Neurodegenerative Diseases: Dysregulation of HSPA5 has been linked to neurodegenerative diseases such as Alzheimer’s and Parkinson’s, where it may contribute to the accumulation of misfolded proteins .
Recombinant HSPA5 is produced using genetic engineering techniques, where the HSPA5 gene is cloned and expressed in a suitable host system, such as bacteria or yeast. This allows for the production of large quantities of the protein for research and therapeutic purposes.
- Research Applications: Recombinant HSPA5 is used in various research studies to understand its function and role in different cellular processes. It is also used to study the mechanisms of diseases where HSPA5 is implicated.
- Therapeutic Potential: Due to its role in protein folding and stress response, recombinant HSPA5 is being explored for potential therapeutic applications, including the treatment of diseases associated with protein misfolding and ER stress .
