ANXA1 Human

What is ANXA1 and what are its basic molecular properties?

ANXA1 is a protein encoded by the ANXA1 gene in humans. It has an amino acid length of 346 and an expected molecular mass of 38.7 kDa. It may also be known as ANX1, LPC1, annexin I (lipocortin I), and annexin-1. ANXA1 belongs to the annexin superfamily of calcium-dependent phospholipid-binding proteins .

What are the primary functions of ANXA1 in human physiology?

ANXA1 is involved in multiple critical biological functions including anti-inflammatory responses, apoptosis regulation, and cell cycle modulation. It is expressed in most cell types and functions extracellularly as an anti-inflammatory pro-resolving protein. It exerts protective effects against several diseases, including viral infections, various cancers (breast, pancreatic, glioblastoma), and has been implicated in metabolic regulation .

How is ANXA1 distributed across human tissues?

ANXA1 is widely expressed in most cell types. In resting conditions, cells contain high levels of ANXA1 in the cytoplasm. Upon cell activation, ANXA1 is mobilized to the cell surface and secreted. Research shows variable expression levels across tissues, with particularly notable expression patterns in immune cells and adipose tissue. Recent studies indicate elevated levels in subcutaneous adipose tissue of individuals with obesity .

What are the most reliable methods for detecting ANXA1 expression in human samples?

Multiple methodologies can reliably detect ANXA1:

• ELISA: Effective for quantifying ANXA1 in plasma or serum samples. This approach has been successfully used to measure ANXA1 levels in patients with malignant and benign breast tumors .

• Western Blot: Standard technique for protein detection in tissue samples. For ANXA1, this has been particularly useful in comparing expression levels between different tissue types (e.g., subcutaneous vs. visceral adipose tissue) .

• Immunohistochemistry: Valuable for visualizing ANXA1 localization in tissue sections. Various validated antibodies targeting human ANXA1 are available across multiple suppliers .

What experimental models are most appropriate for studying ANXA1 function?

Several experimental approaches have proven valuable:

• Genetic modification models: ANXA1 knockout or tissue-specific deletion models provide insights into physiological roles. Whole-body or adipocyte-specific ANXA1 deletion has been used to study metabolic effects .

• Pharmacological modulation:

  • Ac2-26 is an ANXA1-like peptide used as an agonist

  • Boc1 is an ANXA1 antagonist that competitively binds to the FPR2 receptor

• Cell culture systems: Human cell lines with varied ANXA1 expression are valuable for mechanistic studies.

How can researchers effectively measure ANXA1-mediated effects on cellular processes?

Multiple methodological approaches have been validated:

• Treg suppression assays: For measuring ANXA1's impact on immune regulation, suppressive assays have demonstrated that ANXA1 enhances the inhibitory function of Treg cells .

• Metabolic assessments: Indirect calorimetry measuring oxygen consumption (VO2), carbon dioxide production (VCO2), and energy expenditure provides insights into ANXA1's role in metabolism .

• RNA sequencing: This approach has identified downstream targets of ANXA1 signaling, such as changes in granzyme A mRNA expression in Treg cells following ANXA1 blockade .

How is ANXA1 involved in cancer progression and what methodologies best study this relationship?

ANXA1 has complex roles in cancer biology that can be studied through:

• Survival analysis: Research has shown that high ANXA1 expression is associated with poorer survival in breast cancer patients, particularly those with triple-negative breast cancer (TNBC) .

• Tumor microenvironment evaluation: ANXA1 enhances Treg cell function, potentially contributing to immunosuppression in the tumor environment. Methodologies include flow cytometry analysis of tumor-infiltrating lymphocytes and functional assays of isolated Treg cells .

• In vivo tumor models: Animal experiments using ANXA1 antagonists (e.g., Boc1) have demonstrated reduced tumor size and downregulated Treg cell function, providing a methodological framework for therapeutic studies .

• Single-cell analysis: Single-cell RNA sequencing approaches have been employed to understand ANXA1 expression patterns across different cell types within tumors, particularly in gliomas .

What is the evidence for ANXA1's role in obesity and metabolic disorders?

Several methodological approaches have revealed ANXA1's importance in metabolism:

• Discordant twin studies: Analysis of monozygotic co-twins discordant for BMI has shown significantly increased ANXA1 mRNA levels in subcutaneous adipose tissue of twins with higher BMI .

• Metabolic phenotyping: Studies in high-fat diet (HFD) models show that ANXA1 knockout mice exhibit:

  • Increased body weight and fat mass

  • Decreased oxygen consumption and energy expenditure

  • Elevated basal blood glucose and insulin levels

  • Marked glucose intolerance and insulin resistance

• Tissue-specific expression analysis: Comparing ANXA1 levels across adipose depots reveals depot-specific regulation, with particularly notable changes in subcutaneous adipose tissue during obesity development .

How does ANXA1 interact with its receptor and what methodologies can characterize this interaction?

ANXA1 signals through a seven-membrane-spanning G-protein-coupled receptor known as formyl peptide receptor 2 (FPR2, also known as ALXR in humans) . Research methodologies to study this interaction include:

• Competitive binding assays: Using labeled ANXA1 peptides and receptor antagonists like Boc1 to characterize binding kinetics.

• Signaling pathway analysis: Evaluating downstream effects through phosphorylation studies and gene expression analysis.

• Structural biology approaches: Investigating the physical interaction between ANXA1 and its receptor through crystallography or molecular modeling.

What are the critical post-translational modifications of ANXA1 and how do they affect function?

ANXA1 undergoes several post-translational modifications that regulate its localization and activity. Key research methodologies include:

• Mass spectrometry: To identify specific modifications (phosphorylation, acetylation, etc.).

• Site-directed mutagenesis: Creating modified versions of ANXA1 to assess functional consequences of specific modifications.

• Subcellular localization studies: Tracking modified ANXA1 to determine how modifications affect translocation from cytoplasm to cell surface.

How can ANXA1 be targeted therapeutically and what methods assess intervention efficacy?

Several approaches show promise:

• FPR2 antagonism: Boc1 and similar compounds have shown efficacy in preclinical models, reducing tumor size and Treg cell function in breast cancer models .

• Recombinant ANXA1: Treatment with recombinant human ANXA1 has been reported to reduce body weight in mice fed high-fat diets, suggesting metabolic applications .

• Efficacy assessment methodologies:

  • Tumor volume measurements in cancer models

  • Metabolic parameter monitoring in obesity models

  • Inflammatory marker quantification in inflammatory conditions

  • Treg functional assays for immunomodulatory applications

How can ANXA1 expression or activity serve as a biomarker in clinical research?

ANXA1 has biomarker potential in multiple contexts:

• Cancer prognosis: High ANXA1 expression correlates with poor survival in breast cancer patients, particularly those with TNBC .

• Obesity classification: ANXA1 levels are significantly elevated in adipose tissue of both metabolically healthy and unhealthy obese individuals compared to lean controls .

• Methodological considerations:

  • Standardized ELISA protocols for plasma/serum quantification

  • Validated immunohistochemistry scoring systems for tissue samples

  • qPCR normalization strategies for expression analysis