hace1 Antibody

What is HACE1 and why is it important in research?

HACE1 (HECT domain and ankyrin repeat containing, E3 ubiquitin protein ligase 1) is a tumor suppressor that inhibits the growth, invasive capacity, and metastasis of cancer cells . It functions as an E3 ubiquitin-protein ligase involved in Golgi membrane fusion and regulation of small GTPases . HACE1 has a tumor-suppressor function dependent on its E3 ligase activity and controls cell cycle progression during cell stress through degradation of cyclin D1 . Research on HACE1 is important because its inactivation has been reported in multiple tumor types, including Wilms' tumor, non-Hodgkin's lymphoma, and lung cancer . Interestingly, recent research has revealed contrasting roles in certain cancers like melanoma, where it can display pro-tumoral properties .

What applications are HACE1 antibodies typically used for?

HACE1 antibodies are commonly used in several laboratory applications:

These applications allow researchers to detect HACE1 protein expression in various cell types and tissues, enabling studies on its role in cancer biology and cellular processes .

What cell lines and tissues show positive reactivity with HACE1 antibodies?

Based on validation data, HACE1 antibodies have shown positive reactivity in:

• Cell lines: HEK-293 cells and HeLa cells show positive Western blot detection

• Tissues: Human heart tissue shows positive immunohistochemical staining

• Tested reactivity: Primarily human samples, though cited reactivity includes both human and mouse samples

When conducting immunohistochemistry on human tissues, researchers should note that antigen retrieval with TE buffer (pH 9.0) is suggested, although citrate buffer (pH 6.0) may also be used as an alternative .

What is the molecular structure and weight of HACE1 protein?

HACE1 protein has the following characteristics:

• Full structure: Contains six N-terminal ankyrin repeats responsible for protein-protein interactions and a C-terminal HECT domain responsible for its E3 ligase activity

• Calculated molecular weight: 909 amino acids, 102 kDa

• Observed molecular weight: Typically observed at 78 kDa in protein assays

• Gene ID (NCBI): 57531

• UniProt ID: Q8IYU2

The discrepancy between calculated and observed molecular weights (102 kDa vs. 78 kDa) is important to note when interpreting Western blot results .

How does HACE1's role differ between cancer types?

HACE1 exhibits context-dependent roles across different cancer types:

• Tumor suppressor role: In Wilms' tumor, HACE1 was first identified as a tumor suppressor based on its location at a translocation breakpoint and loss of expression compared to normal kidney tissue . HACE1-knockout mice develop multi-organ, late-onset cancers, further supporting its tumor suppressor function . Its expression is lost in several neoplasms including Wilms' tumors and colorectal cancer .

• Pro-tumoral role in melanoma: Contrary to its tumor suppressor function in other cancers, HACE1 promotes melanoma cell migration and adhesion in vitro and is required for mouse lung colonization by melanoma cells in vivo . Transcriptomic analysis of HACE1-depleted melanoma cells revealed inhibition of ITGAV and ITGB1 as well as changes in other genes involved in cell migration . HACE1 promoted K27 ubiquitination of fibronectin and regulated its secretion, affecting integrin expression and melanoma cell adhesion and migration .

This dual role highlights the complex function of HACE1 in different cellular contexts and suggests that targeting HACE1 for cancer therapy may require a cancer-type specific approach .

What mechanisms underlie HACE1's regulation of HIF1α during hypoxia?

HACE1 regulates HIF1α (hypoxia-inducible factor 1 alpha) through the following mechanisms:

• HACE1 blocks the accumulation of HIF1α during cellular hypoxia through decreased protein stability

• This property is dependent on HACE1's E3 ligase activity and loss of Ras-related C3 botulinum toxin substrate 1 (RAC1), an established target of HACE1-mediated ubiquitination and degradation

• In vivo studies showed that genetic deletion of Rac1 reversed the increased HIF1α expression observed in Hace1-/- mice in murine KRas G12D-driven lung tumors

• An inverse relationship was observed between HACE1 and HIF1α levels in tumors compared to patient-matched normal kidney tissues

This HACE1-RAC1-HIF1α axis represents a previously unrecognized function for the HACE1 tumor suppressor in regulating how cells respond to hypoxic stress .

How does HACE1 regulate cell adhesion and migration in melanoma?

HACE1 promotes melanoma cell adhesion and migration through a novel molecular cascade:

• HACE1 promotes K27 ubiquitination of fibronectin and regulates its secretion

• Secreted fibronectin regulates ITGAV and ITGB1 expression, as well as melanoma cell adhesion and migration

• HACE1 silencing severely impairs melanoma cell adhesion as measured by classical adhesion assays and xCELLigence adhesion assays

• Melanoma cells overexpressing HACE1 display increased adhesion ability

• In vivo studies showed that HACE1 silencing significantly reduced lung colonization by melanoma cells after tail vein injection in mice

• Transcriptomic analysis confirmed that HACE1 silencing alters cell migration processes, likely through inhibition of ITGAV and ITGB1 expression

This regulatory pathway reveals HACE1 as an important regulator of melanoma cell invasive properties, displaying pro-tumoral functions in this context .

What is the relationship between HACE1 and RAC1?

HACE1 specifically binds to GTP-bound RAC1, mediating its ubiquitination and subsequent degradation . This interaction has several functional consequences:

• HACE1 controls the degradation of GTP-bound RAC1, as demonstrated in melanoma cells

• This regulation plays a role in host defense against pathogens

• The HACE1-RAC1 interaction is critical for HACE1's regulation of HIF1α during hypoxia, as genetic deletion of Rac1 reversed the increased HIF1α expression observed in Hace1-/- mice

• siRNA against RAC1 induces a decrease in both RAC1 expression and migration in melanoma cells, similar to the effects observed with HACE1 silencing

This relationship highlights RAC1 as a key downstream effector of HACE1's various cellular functions .

What are the optimal conditions for using HACE1 antibodies in Western blotting?

For optimal Western blotting with HACE1 antibodies, researchers should follow these methodological guidelines:

When troubleshooting, note that the calculated molecular weight of HACE1 is 102 kDa, but it is typically observed at 78 kDa in protein assays . Different antibody clones may have varying specificity and sensitivity, so validation in your specific system is recommended.

How can HACE1 function be effectively knocked down for functional studies?

Based on research methodologies in the literature, effective HACE1 knockdown can be achieved through:

• siRNA transfection: Multiple studies have successfully used siRNA to silence HACE1 expression in various cell lines including 501MEL, A375, and patient-derived melanoma cells (C-13.08)

• Validation of knockdown: Western blot analysis should be performed to confirm reduction in HACE1 protein levels

• Functional assays: Following knockdown, migration assays (such as wound healing or Transwell), adhesion assays (classical or xCELLigence-based), and gene expression analysis (RT-qPCR or RNA-seq) can be performed to assess functional consequences

• In vivo validation: For studies requiring in vivo validation, HACE1-silenced cells can be labeled with fluorescent dyes and injected into mouse models to monitor processes such as lung colonization

For rescue experiments, transfection with plasmids encoding HACE1 can be used to overexpress the protein and confirm the specificity of knockdown phenotypes .

What protocols are recommended for immunohistochemical detection of HACE1?

For successful immunohistochemical detection of HACE1 in tissue samples:

Researchers should optimize the protocol for their specific tissue of interest, as antigen accessibility may vary between different tissue types. For formalin-fixed paraffin-embedded (FFPE) tissues, thorough deparaffinization and appropriate antigen retrieval are critical for successful staining .

How can researchers measure HACE1 E3 ligase activity in experimental settings?

To assess HACE1's E3 ligase activity, which is critical for its tumor suppressor function, researchers can employ the following methodologies:

• Ubiquitination assays: In vitro or cell-based ubiquitination assays using purified components (E1, E2, HACE1, substrate protein, and ubiquitin) can directly measure HACE1's ability to transfer ubiquitin to target proteins

• RAC1 degradation: Since RAC1 is an established target of HACE1-mediated ubiquitination, measuring RAC1 protein levels or specifically GTP-bound RAC1 levels can serve as a readout for HACE1 activity

• Fibronectin ubiquitination: In melanoma contexts, measuring K27 ubiquitination of fibronectin can be used as a specific readout of HACE1 activity

• Mutational analysis: Comparing wild-type HACE1 with catalytically inactive mutants (mutations in the HECT domain) can help establish which cellular functions depend on its E3 ligase activity

For all these approaches, appropriate controls should include HACE1 knockdown or knockout cells, as well as rescue experiments with wild-type vs. catalytically inactive HACE1 .

How should researchers interpret discrepancies between calculated and observed molecular weights of HACE1?

The calculated molecular weight of HACE1 is 102 kDa (909 amino acids), but it is typically observed at 78 kDa in Western blot analyses . Researchers should consider the following when interpreting this discrepancy:

• Post-translational modifications: These can affect protein migration in SDS-PAGE

• Protein degradation: Partial degradation during sample preparation may result in lower molecular weight bands

• Protein isoforms: Alternative splicing may generate different HACE1 isoforms

• Antibody specificity: Different antibodies may recognize different epitopes or isoforms of HACE1

To address these discrepancies, researchers should:

• Use positive controls with known HACE1 expression

• Consider running HACE1-overexpressing lysates alongside experimental samples

• Validate with multiple antibodies targeting different epitopes of HACE1

• Include HACE1 knockdown samples as negative controls

What factors might explain contradictory findings regarding HACE1's role in different cancer types?

The contrasting roles of HACE1 as a tumor suppressor in many cancers versus its pro-tumoral properties in melanoma might be explained by:

Researchers investigating HACE1's role should carefully consider:

• Cell type-specific functions and interactors

• Comprehensive analysis of downstream pathways

• In vivo validation of in vitro findings

• Integration of genomic, transcriptomic, and proteomic data

How can researchers resolve antibody cross-reactivity issues when studying HACE1?

When encountering potential cross-reactivity issues with HACE1 antibodies:

• Validate with genetic models: Use HACE1 knockdown or knockout cells as negative controls to confirm antibody specificity

• Multiple antibodies: Employ different antibodies targeting distinct epitopes of HACE1

• Blocking peptides: Use blocking peptides (the immunogen used to generate the antibody) to confirm specific binding

• Pre-absorption controls: Pre-absorb the antibody with recombinant HACE1 protein before staining

• Species validation: Ensure the antibody is validated for the species being studied (human vs. mouse)

What are emerging areas for HACE1 antibody applications in cancer research?

Emerging applications for HACE1 antibodies in cancer research include:

• Biomarker development: Given the differential expression of HACE1 across cancer types, HACE1 antibodies may be valuable for developing diagnostic or prognostic biomarkers

• Personalized medicine approaches: Assessing HACE1 expression in patient samples may help stratify patients for specific therapeutic approaches

• Monitoring treatment response: Changes in HACE1 expression or localization may serve as indicators of treatment response

• Therapeutic target validation: HACE1 antibodies can help validate the protein as a therapeutic target, particularly in contexts like melanoma where it exhibits pro-tumoral properties

• Combination with hypoxia markers: Given HACE1's role in regulating HIF1α, combining HACE1 staining with hypoxia markers may provide insights into tumor microenvironment

These applications highlight the importance of high-quality, well-validated HACE1 antibodies for advancing cancer research and potential clinical applications.