RARRES2 Human, His

What is RARRES2 and what are its alternative names in scientific literature?

RARRES2 (Retinoic Acid Receptor Responder Protein 2) is a secreted protein encoded by the RARRES2 gene in humans. It is also known by several other names in scientific literature: Chemerin, RAR-responsive protein TIG2, Tazarotene-induced gene 2 protein, and TIG2. The protein was initially identified as a gene whose expression is upregulated by the synthetic retinoid tazarotene . The various nomenclature reflects its discovery context and functional characteristics across different research areas .

What is the molecular structure of human RARRES2?

Human RARRES2 is a small secreted protein with a calculated molecular weight of approximately 16.9 kDa. The mature protein sequence typically spans from Glu21 to Ser157 of the full gene product. When expressed recombinantly with a histidine tag, the protein generally appears at 14-20 kDa on SDS-PAGE gels . RARRES2 is initially secreted as an inactive precursor called prochemerin, which requires C-terminal cleavage by inflammatory and coagulation serine proteases to become biologically active . This processing is crucial for its chemoattractant properties and receptor binding capabilities.

What tissue distribution pattern does RARRES2 exhibit?

RARRES2 displays a specific tissue distribution pattern with highest expression in:

• Skin (primary expression site)

• White adipose tissue

• Liver

• Lung

• Pancreas

• Spleen

• Reproductive organs (prostate, ovary)

• Gastrointestinal tract (small intestine, colon)

This diverse expression pattern correlates with RARRES2's multiple biological functions across different physiological systems, suggesting its involvement in tissue-specific processes beyond inflammation .

How should recombinant RARRES2-His be reconstituted for maximum stability?

For optimal reconstitution of lyophilized RARRES2-His protein:

• Briefly centrifuge the vial to collect all material at the bottom

• Reconstitute in sterile water to a concentration of 0.1-1.0 mg/mL

• Gently mix by rotating the vial to ensure complete solubilization

• Store reconstituted protein at 4-8°C for short-term use (2-7 days)

• For long-term storage, prepare aliquots and store at -20°C or lower

• Avoid repeated freeze-thaw cycles that may reduce biological activity

Researchers should note that the specific buffer composition (typically 20mM PB, 150mM NaCl, pH 7.4) provides optimal stability. The addition of protectants like trehalose, mannitol, and Tween 80 during manufacturing helps maintain protein integrity during the lyophilization process .

What expression systems are optimal for producing functional recombinant RARRES2?

The most effective expression systems for producing functional human RARRES2 are mammalian cell-based platforms, particularly:

• HEK293 cells: Provide proper post-translational modifications and folding

• Other human cell lines: Ensure proper glycosylation patterns

While bacterial expression systems (E. coli) may yield higher protein quantities, they often lack the necessary post-translational modifications required for full RARRES2 functionality. Mammalian expression systems are preferred when biological activity is crucial for experimental outcomes . The expression conditions should be optimized to produce protein with >95% purity as confirmed by SDS-PAGE analysis.

How does RARRES2 function in inflammatory responses?

RARRES2 plays a central role in inflammatory responses through multiple mechanisms:

• Chemoattraction: Active chemerin functions as a potent chemoattractant by binding to CMKLR1 (ChemR23), a G protein-coupled receptor expressed on macrophages and dendritic cells

• Leukocyte recruitment: Stimulates directed migration of antigen-presenting cells to sites of inflammation

• Activation pathway: RARRES2 is secreted as inactive prochemerin that requires proteolytic cleavage by inflammatory serine proteases to become fully active

• Inflammation resolution: May participate in both pro- and anti-inflammatory processes depending on tissue context and activation state

The complex role of RARRES2 in inflammation makes it a potential target for immunomodulatory therapies targeting chronic inflammatory conditions .

What is the relationship between RARRES2 and cancer pathogenesis?

RARRES2 demonstrates paradoxical relationships with cancer pathogenesis that vary by cancer type:

This dual relationship makes RARRES2 an intriguing target for cancer research, as its expression and activity must be interpreted in a tissue-specific and cancer-specific context .

How can researchers distinguish between active chemerin and prochemerin in experimental systems?

Distinguishing between prochemerin and active chemerin requires specialized methodological approaches:

• Immunological detection:

  • Western blotting with antibodies specific to the C-terminal region can differentiate between cleaved (active) and uncleaved (inactive) forms

  • ELISA kits designed to detect total or active chemerin specifically

• Functional assays:

  • Chemotaxis assays using CMKLR1-expressing cells (active chemerin induces migration while prochemerin does not)

  • Calcium mobilization assays in receptor-expressing cells

• Mass spectrometry:

  • LC-MS/MS analysis of C-terminal peptides to identify specific cleavage sites and activation status

• Activity normalization:

  • Express results as a ratio of active/total chemerin to account for variations in baseline expression

These approaches enable researchers to precisely characterize the activation status of RARRES2 in complex biological samples.

What are the methodological challenges in studying RARRES2's dual role in metabolism and inflammation?

Researchers face several methodological challenges when investigating RARRES2's dual functionality:

• Tissue-specific expression patterns:

  • Require simultaneous sampling from multiple tissues

  • Necessitate specialized techniques for low-abundance detection

• Activation-dependent effects:

  • Active chemerin vs. prochemerin must be distinguished

  • Proteolytic processing varies by physiological context

• Receptor diversity:

  • CMKLR1, GPR1, and CCRL2 all bind chemerin with different affinities

  • Cell-specific receptor expression confounds interpretation

• Species differences:

  • Murine models show significant differences in chemerin biology

  • Cross-species extrapolation requires careful validation

• Integrated analysis requirements:

  • Metabolic and inflammatory parameters must be measured simultaneously

  • Temporal dynamics of activation add complexity to experimental design

Addressing these challenges requires multidisciplinary approaches combining molecular techniques, cellular assays, and computational modeling.

How do RARRES2 genetic polymorphisms influence metabolic disease risk?

RARRES2 genetic variations show complex associations with metabolic diseases:

• Type 2 diabetes association:

  • Specific polymorphisms in the RARRES2 gene have been investigated for association with T2DM risk

  • Results show population-specific effects, with certain variants showing significance in Southern Han Chinese populations

• Genetic models:

  • The rs736118 polymorphism in RARRES2 shows significant association with T2DM in the recessive genetic model

  • The rs974456 genotype shows significance in the dominant genetic model, with correlations to sex, BMI, and triglyceride levels

• Gene-environment interactions:

  • Smoking history and other environmental factors may interact with RARRES2 polymorphisms as independent risk factors for T2DM

  • These interactions complicate genetic association interpretations

Researchers studying RARRES2 genetics should employ multiple genetic models and consider environmental cofactors when designing association studies in metabolic diseases.

What experimental approaches can resolve the paradoxical tissue vs. serum RARRES2 levels in cancer?

The paradoxical relationship between decreased tumor RARRES2 expression and increased serum levels requires specialized experimental approaches:

• Paired sample analysis:

  • Simultaneous collection of matched tumor tissue and serum samples

  • Correlation analysis between tissue mRNA, tissue protein, and serum protein levels

• Xenograft models:

  • Mouse xenograft systems have demonstrated that higher tissue RARRES2 expression correlates with higher serum levels

  • Evidence suggests intrinsic homeostatic mechanisms maintain serum RARRES2 levels

• Source identification:

  • Cell-type specific markers to identify alternative RARRES2 secretion sources

  • Isotope labeling to track protein origin and biodistribution

• Mechanistic studies:

  • Investigation of compensatory upregulation in non-tumor tissues

  • Analysis of clearance rates and protein stability in cancer vs. normal conditions

These methodological approaches can help elucidate the complex relationship between tissue expression and serum levels in cancer biology.

What quality control parameters should be monitored when working with recombinant RARRES2-His?

Critical quality control parameters for recombinant RARRES2-His include:

• Purity assessment:

  • 95% purity by reducing SDS-PAGE is standard for research applications

  • Silver staining for higher sensitivity detection of contaminants

• Endotoxin levels:

  • Should be <1.0 EU per μg protein as determined by LAL method

  • Critical for avoiding confounding inflammatory responses in biological assays

• Molecular weight verification:

  • Expected 16-20 kDa by SDS-PAGE for His-tagged human RARRES2

  • Mass spectrometry confirmation for precise mass determination

• Functional validation:

  • CMKLR1 binding assays

  • Chemotaxis assays using appropriate cell types

• Batch consistency:

  • Lot-to-lot comparisons of activity and physiochemical properties

  • Reference standards testing alongside experimental samples

Implementing these quality control measures ensures experimental reproducibility and valid biological interpretations.

How can researchers optimize storage conditions to maintain RARRES2-His stability and activity?

To maintain optimal stability and activity of RARRES2-His:

• Lyophilized storage:

  • Store at -20°C to -80°C for up to 12 months

  • Protect from moisture and maintain original desiccated conditions

• Reconstituted protein:

  • Store at 4-8°C for short-term use (2-7 days)

  • Prepare small single-use aliquots for long-term storage at -20°C or below

  • Avoid more than 3 freeze-thaw cycles

• Buffer considerations:

  • Addition of carrier proteins (0.1% BSA) may improve stability for dilute solutions

  • Maintain pH between 7.0-7.5

  • Consider adding protease inhibitors for sensitive applications

• Shipping conditions:

  • Transport with ice packs or dry ice depending on duration

  • Validate protein activity after transport for critical applications

Proper storage and handling significantly extend the usable lifetime of recombinant RARRES2 preparations and ensure consistent experimental results.