Recombinant Macaca mulatta (Rhesus macaque) Interleukin-1 receptor accessory protein (IL1RAP)

Basic Properties

The recombinant Rhesus monkey IL1RAP is a well-characterized protein with defined molecular properties. When expressed in human embryonic kidney (HEK293) cells with a His-tag at the C-terminus, the protein spans from Met1 to Glu359, comprising 350 amino acids with a calculated molecular mass of 40.56 kDa . The protein shares significant homology with human IL1RAP, making it valuable for comparative studies of interleukin signaling across primate species.

Protein Architecture

IL1RAP belongs to the interleukin-1 receptor family and features characteristic structural domains:

• An extracellular domain containing immunoglobulin-like regions responsible for ligand interaction

• A transmembrane domain anchoring the protein to the cell membrane

• An intracellular Toll/IL-1R (TIR) domain essential for signal transduction

The protein exists in multiple isoforms resulting from alternative splicing, with both membrane-bound and soluble variants that differ in their C-terminal regions . The ratio of soluble to membrane-bound forms increases notably during acute-phase responses or stress conditions, suggesting a regulatory mechanism for IL-1 signaling .

Production and Purification

Recombinant Rhesus monkey IL1RAP is typically produced in mammalian expression systems to ensure proper folding and post-translational modifications. The protein is commonly expressed with His-tags or other fusion partners to facilitate purification. The production specifications for commercially available recombinant IL1RAP include:

Table 1: Properties of Recombinant Rhesus monkey IL1RAP protein

Role in IL-1 Signaling

IL1RAP serves as a critical co-receptor in the IL-1 signaling pathway. It does not bind to interleukin-1 directly but associates with IL1R1 that has bound IL1B to form a high-affinity receptor complex . This complex formation is necessary for efficient signal transduction and subsequent activation of downstream pathways including NF-kappa-B activation . The signaling cascade involves:

1. Initial binding of IL-1 to IL-1R1

2. Recruitment of IL1RAP to form a heterotrimeric complex

3. Conformational changes in the cytoplasmic TIR domains

4. Recruitment of adapter molecules including TOLLIP, MYD88, and IRAK1/2

5. Activation of downstream kinases and transcription factors

6. Induction of pro-inflammatory gene expression

The protein exhibits remarkable specificity in its co-receptor functions, showing strong interactions with multiple interleukin receptor family members as evidenced by high STRING interaction scores .

Extended Signaling Functions

Beyond the canonical IL-1 pathway, IL1RAP also functions as a co-receptor for IL1RL2 in the IL-36 signaling system . This versatility points to IL1RAP's broader role in coordinating various inflammatory signals. The protein's function extends to multiple signaling networks that collectively regulate inflammation, immune cell activation, and tissue homeostasis.

Protein-Protein Interactions

STRING database analysis reveals the extensive protein interaction network of Macaca mulatta IL1RAP, highlighting its central role in inflammatory signaling cascades. The protein shows particularly strong interactions with multiple components of the interleukin signaling system:

Table 2: Functional interaction partners of IL1RAP with confidence scores

The remarkably high interaction scores with IL1B, IL33, and IL1R1 (all above 0.96) underscore IL1RAP's central role in mediating signals from multiple interleukin family members. The interaction with MYD88 further confirms its involvement in the canonical signaling pathway leading to NF-kappa-B activation.

Role in Immune Regulation

IL1RAP plays a significant role in immune regulation by facilitating IL-1 signaling, which is crucial for initiating and maintaining inflammatory responses . This signaling pathway is essential for:

• Activation of innate immune responses

• Production of pro-inflammatory cytokines

• Recruitment and activation of immune cells

• Amplification of inflammatory cascades

• Regulation of adaptive immune responses

The balance between membrane-bound and soluble IL1RAP forms contributes to the fine-tuning of these immune responses, with soluble forms potentially acting as decoy receptors to dampen excessive inflammation .

Comparative Studies with Human IL1RAP

The high degree of conservation between rhesus and human IL1RAP makes the recombinant Macaca mulatta protein valuable for comparative studies. Researchers can investigate species-specific differences in IL-1 signaling pathways and test the cross-reactivity of therapeutic agents targeting IL1RAP before advancing to human studies. This approach is particularly relevant given the established use of rhesus macaques as models for human inflammatory and autoimmune conditions.

Applications in Drug Discovery

Recombinant Macaca mulatta IL1RAP has significant applications in drug discovery pipelines, particularly for the development of therapeutics targeting the IL-1 signaling pathway. These applications include:

• High-throughput screening of small molecule inhibitors

• Development and testing of therapeutic antibodies

• Structure-based drug design targeting the IL-1 receptor complex

• Validation studies for IL-1 pathway antagonists

Given IL1RAP's abnormal expression in various diseases including cancer and autoimmune disorders, it has emerged as a promising target for therapeutic intervention .

Functional Assays

Several assays can be employed to assess the functional activity of recombinant IL1RAP:

1. Binding Assays: ELISA-based binding assays measuring interaction with IL-1R1 and IL-1β

2. Cell-Based Assays: Reporter cell lines expressing NF-κB response elements

3. Co-Immunoprecipitation: Verification of complex formation with IL-1R1

4. Surface Plasmon Resonance: Quantitative measurement of binding kinetics

Quality Control Parameters

Quality control for recombinant IL1RAP typically includes:

• Purity assessment by SDS-PAGE (>90% purity standard)

• Endotoxin testing using the LAL method (<1.0 EU per μg protein)

• Functional validation through binding assays

• Mass spectrometry verification of protein identity

• SEC-HPLC analysis for aggregation assessment

Evolutionary Conservation

IL1RAP demonstrates significant evolutionary conservation across primate species, reflecting the fundamental importance of IL-1 signaling in mammalian immune systems. The high degree of homology between rhesus macaque and human IL1RAP makes the recombinant protein particularly valuable for translational research.

Cross-Reactivity Studies

Studies of recombinant IL1RAP from different species are important for understanding cross-reactivity of therapeutic agents. Research indicates that recombinant human IL-1α demonstrates potent behavioral effects in rhesus monkeys, suggesting a high degree of cross-species activity in the IL-1 signaling pathway . This cross-reactivity extends to the IL1RAP component of the signaling complex.