ORM1 Antibody

What is ORM1 and what are its primary biological functions?

ORM1 (Orosomucoid 1, also known as Alpha-1-acid glycoprotein 1 or AGP1) is a plasma protein primarily synthesized and secreted by the liver. It functions as a transport protein in the bloodstream, binding various ligands within its beta-barrel domain. ORM1 also plays significant roles in:

• Binding synthetic drugs and influencing their distribution and bioavailability

• Modulating immune system activity during acute-phase reactions

• Contributing to lipid homeostasis (particularly in yeast homologs)

• Participating in protein quality control mechanisms

The protein has a calculated molecular weight of 24 kDa, though it is often observed at 40-47 kDa in experimental contexts due to extensive post-translational modifications, particularly N-glycosylation .

Where is ORM1 primarily expressed and in which tissue types can it be detected?

This expression pattern makes ORM1 particularly relevant for studies involving liver physiology, cancer biomarkers, and plasma protein interactions .

What are the known post-translational modifications of ORM1 protein?

ORM1 undergoes several significant post-translational modifications that affect its function and molecular weight. Based on UniProt data, these modifications include:

The extensive N-glycosylation causes ORM1 to appear at a higher molecular weight (40-47 kDa) than its calculated size (24 kDa) in experimental assessments. This glycan heterogeneity, particularly at Asn-33, may be functionally significant in different physiological contexts .

What are the recommended applications and dilutions for ORM1 antibody use?

ORM1 antibodies have been validated for multiple experimental applications. Based on technical data for antibody 16439-1-AP, the recommended applications and dilutions are:

It's important to note that optimal dilutions should be determined empirically for each experimental system, as results may be sample-dependent .

What sample types and species reactivity have been validated for ORM1 antibodies?

Commercial ORM1 antibodies have been tested and validated across multiple species and sample types:

How should ORM1 antibodies be stored and handled to maintain optimal activity?

For maximum stability and activity of ORM1 antibodies, follow these storage and handling recommendations:

• Store at -20°C, where antibodies remain stable for one year after shipment

• The provided storage buffer typically contains PBS with 0.02% sodium azide and 50% glycerol at pH 7.3

• Aliquoting is generally unnecessary for standard use cases

• Avoid repeated freeze-thaw cycles which can denature antibody proteins

• Allow the antibody to equilibrate to room temperature before opening the vial

• Brief centrifugation may be necessary if the solution has collected in the cap

These storage conditions ensure retention of specific binding activity and minimize degradation over time .

How can ORM1 antibodies be used to investigate protein-protein interactions in lipid homeostasis pathways?

ORM1 and its homologs (particularly in yeast) play significant roles in lipid homeostasis through protein-protein interactions. For investigating these interactions:

• Co-immunoprecipitation (Co-IP) assays have successfully demonstrated interactions between ORM1 and components of the sphingolipid biosynthesis pathway, including Lcb1 and Lcb2 of serine palmitoyltransferase (SPT).

• Methodology for Co-IP with ORM1:

  • Use TAP-tagged ORM1 constructs for pull-down experiments

  • Include appropriate negative controls (untagged proteins, irrelevant ER membrane proteins like Erg11)

  • Verify interactions through reciprocal pull-downs with tagged partner proteins

  • Use western blotting with specific antibodies to detect interacting partners

• Experimental validation has shown that:

  • HA-Lcb1 co-precipitates with Orm1-TAP and Orm2-TAP

  • HA-Lcb2 is present in Orm2-TAP pull-downs

  • These interactions are specific, as demonstrated by negative controls

This approach provides insights into how ORM1 regulates sphingolipid biosynthesis through direct interaction with metabolic enzymes .

What is the significance of ORM1 as a biomarker in hepatocellular carcinoma (HCC) research?

Recent research has established ORM1 as a potential biomarker with significant implications for HCC research:

• Expression analysis using Gene Expression Omnibus and The Cancer Genome Atlas datasets has shown altered ORM1 expression in HCC tissues compared to non-tumor tissues.

• Immunohistochemistry studies have revealed:

  • Differential ORM1 protein expression between HCC and adjacent non-tumor samples

  • Correlation between ORM1 expression and clinical parameters, including vascular invasion

• Functional studies using siRNA-mediated knockdown of ORM1 in HCC cell lines (HepG2, Huh-7) have demonstrated:

  • Decreased IC50 values for sorafenib after ORM1 knockdown, suggesting a relationship between ORM1 expression and treatment sensitivity

  • Attenuated cell growth following ORM1 knockdown

• Methodology for evaluating ORM1 in HCC samples:

  • IHC using anti-ORM1 antibody (recommended dilution 1:100)

  • Scoring based on staining intensity (0-3 scale) and percentage of positive cells

  • Correlation analysis with clinical parameters

These findings suggest that ORM1 may serve as both a prognostic biomarker and potential therapeutic target in HCC .

How can ORM1 antibodies be used in investigating drug resistance mechanisms?

ORM1 antibodies provide valuable tools for exploring the relationship between ORM1 expression and drug resistance, particularly in cancer research:

• Experimental approach using cell lines:

  • Establish sorafenib-resistant cell lines through long-term treatment (e.g., HepG2 cells with 1μM sorafenib)

  • Use ORM1 antibodies to quantify expression changes in resistant vs. sensitive cells

  • Perform ORM1 knockdown using siRNA and measure changes in drug sensitivity

  • Monitor IC50 values before and after ORM1 modulation

• Significance in research:

  • Studies have shown that ORM1 knockdown in HepG2 and Huh-7 cells significantly decreased IC50 values for sorafenib

  • This suggests ORM1 may contribute to treatment resistance mechanisms

  • ORM1 antibodies enable quantitative assessment of expression changes during resistance development

• Methodological considerations:

  • Western blotting (1:500-1:2000 dilution) for quantitative analysis of ORM1 expression

  • IHC (1:50-1:500 dilution) for spatial distribution analysis in tissue samples

  • Flow cytometry for cell-by-cell analysis of expression levels

This research direction highlights the importance of ORM1 beyond its traditional role as a plasma protein and suggests potential therapeutic strategies targeting ORM1 in resistant cancers .

What are the common issues with antigen retrieval when using ORM1 antibodies for IHC?

Antigen retrieval is a critical step for successful ORM1 detection in IHC. Based on technical recommendations and research protocols:

• Preferred antigen retrieval methods:

  • Primary recommendation: TE buffer at pH 9.0

  • Alternative approach: Citrate buffer at pH 6.0

• Common issues and solutions:

  • Weak or absent staining: Try extending antigen retrieval time or switching from citrate to TE buffer

  • High background: Reduce antibody concentration and optimize blocking steps

  • Non-specific staining: Include appropriate isotype controls to confirm specificity

• Tissue-specific considerations:

  • Liver tissues (where ORM1 is highly expressed) may require shorter antigen retrieval times

  • Tissues with lower expression may benefit from signal amplification systems

  • Formalin fixation time affects retrieval efficiency; adjust protocols accordingly

Optimizing antigen retrieval conditions is particularly important when comparing ORM1 expression across different tissue types or pathological conditions .

How can researchers address the discrepancy between calculated and observed molecular weights of ORM1?

The discrepancy between ORM1's calculated molecular weight (24 kDa) and its observed weight in experimental systems (40-47 kDa) presents a technical challenge. Consider these approaches:

• Understanding the basis of the discrepancy:

  • Extensive N-glycosylation (at positions N33, N56, N72, and N93) contributes significantly to the higher observed weight

  • Other post-translational modifications (phosphorylation at Y109 and Y175, acetylation at K179) may also affect mobility

• Methodological approaches to address this issue:

  • Include deglycosylation controls (PNGase F treatment) to confirm identity

  • Run longer gels with appropriate molecular weight markers spanning 20-50 kDa

  • Include positive control samples with established ORM1 expression

  • Consider gradient gels (4-20%) for better resolution of glycosylated variants

• Interpretation guidelines:

  • Document both calculated and observed weights in research reports

  • Heterogeneous bands between 40-47 kDa likely represent differentially glycosylated forms

  • Very low molecular weight bands may indicate degradation products or alternative splice variants

This technical consideration is essential for accurate western blot interpretation and avoiding false negative results when probing for ORM1 .

What controls should be included when using ORM1 antibodies for co-immunoprecipitation studies?

When designing co-immunoprecipitation (co-IP) experiments with ORM1 antibodies, include these essential controls:

• Negative controls to establish specificity:

  • IgG-Sepharose without tagged ORM1 (demonstrates non-specific binding)

  • Pull-down with an irrelevant ER membrane protein (e.g., Erg11-TAP)

  • Lysates from cells not expressing the tagged protein

• Positive controls to validate the technique:

  • Input sample (pre-IP lysate) to confirm target protein expression

  • Known interacting partners (if established)

  • IP of the tagged protein itself to confirm pull-down efficiency

• Validation through reciprocal co-IP:

  • If ORM1 pulls down protein X, verify that tagged protein X can pull down ORM1

  • This bidirectional validation strengthens evidence for true interactions

• Technical considerations:

  • Standardize lysate concentration (1.0-3.0 mg total protein)

  • Use 0.5-4.0 μg of antibody for optimal pull-down

  • Include detergent controls to distinguish membrane-mediated from direct interactions

These controls are critical for distinguishing true interactions from artifacts, particularly important when studying membrane proteins like ORM1 that exist in complexes .

How is ORM1 being investigated in the context of lipid metabolism regulation?

Current research into ORM1's role in lipid metabolism is advancing through several approaches:

• Genetic studies in yeast models:

  • orm1Δ orm2Δ double deletion strains show impaired growth in the presence of phytosphingosine (PHS)

  • This phenotype can be rescued by overexpression of the long chain base transporter Rsb1

  • These findings suggest ORM proteins regulate sphingolipid homeostasis

• Protein interaction studies:

  • Co-immunoprecipitation experiments have demonstrated physical interactions between ORM proteins and the SPT components Lcb1 and Lcb2

  • These interactions appear to be specific to the sphingolipid synthesis pathway

  • The interactions suggest direct regulatory control of SPT activity by ORM proteins

• Translational research directions:

  • Understanding how mammalian ORM1 interacts with lipid metabolism enzymes

  • Investigating whether ORM1 polymorphisms affect lipid profiles in human populations

  • Exploring therapeutic targeting of ORM1 for lipid disorders

This research area connects ORM1's classical role as a transport protein with emerging functions in metabolic regulation, suggesting new therapeutic targets for lipid disorders .

What methodologies are being developed to study ORM1's role in drug resistance mechanisms?

Emerging methodologies for investigating ORM1's contribution to drug resistance include:

• Cell-based experimental systems:

  • Development of drug-resistant cell lines through incremental exposure (e.g., HepG2 cells with 1μM sorafenib long-term treatment)

  • Comparative analysis of ORM1 expression between parental and resistant lines

  • siRNA-mediated knockdown to assess functional contribution to resistance

• Mechanistic investigations:

  • Analysis of how ORM1 affects drug binding, metabolism, or efflux

  • Investigation of signaling pathway alterations following ORM1 modulation

  • Study of ORM1's interaction with known resistance mediators

• Translational approaches:

  • Correlation of ORM1 expression in patient samples with treatment response

  • Development of ORM1-targeting combination therapies to overcome resistance

  • Use of ORM1 as a biomarker to guide treatment selection

These approaches highlight the transition of ORM1 research from basic protein characterization to application in precision medicine, particularly in cancer therapeutics where drug resistance remains a significant challenge .

How can researchers effectively integrate ORM1 antibody-based techniques with genomic and proteomic approaches?

Modern research increasingly requires integration of antibody-based techniques with -omics approaches:

• Integrated methodological workflow:

  • Start with genomic/transcriptomic analysis to identify ORM1 expression changes

  • Validate at protein level using ORM1 antibodies in western blot (1:500-1:2000)

  • Perform spatial analysis with IHC (1:50-1:500) to localize expression

  • Use co-IP (0.5-4.0 μg antibody) to identify protein interaction networks

• Multi-omics data integration strategies:

  • Correlate ORM1 protein levels with mRNA expression to identify post-transcriptional regulation

  • Map post-translational modifications using mass spectrometry and validate with specific antibodies

  • Connect protein interactions identified via co-IP to pathway analysis from -omics data

• Analytical considerations:

  • Account for glycosylation heterogeneity when comparing protein and transcript levels

  • Consider cell-type specific expression when interpreting bulk -omics data

  • Use network analysis to contextualize ORM1 within broader biological systems

This integrated approach provides a more comprehensive understanding of ORM1 biology than any single technique alone, particularly important when investigating complex phenotypes like drug resistance or disease progression .