IL23R Human

What is the molecular structure of human IL23R and how does it function in cell signaling?

Human IL23R is a type I transmembrane protein consisting of 629 amino acids with distinct domains: a 23-amino acid signal peptide, a 330-amino acid extracellular domain, a 23-amino acid transmembrane domain, and a 253-amino acid cytoplasmic region . The functional IL-23 receptor complex consists of two subunits: the IL-12 receptor beta 1 subunit (IL-12 Rβ1) and the IL-23-specific receptor subunit (IL-23R) .

Structurally, IL23R contains an N-terminal immunoglobulin-like domain and two cytokine receptor domains in its extracellular portion. Unlike IL-12 Rβ2, IL23R lacks the three extracellular membrane-proximal fibronectin-type III domains. The receptor features a WQPWS sequence in the transmembrane-proximal cytokine receptor domain that resembles the cytokine receptor signature WSXWS motif .

The cytoplasmic region contains three potential Src homology 2 domain-binding sites and two potential STAT-binding sites. When IL-23 (a heterodimeric cytokine composed of p19 and p40 subunits) binds to the receptor complex, it initiates signal transduction primarily through Jak2, Tyk2, and several STAT proteins (STAT1, STAT3, STAT4, and STAT5) . This signaling cascade ultimately promotes inflammation and coordinates immune responses to pathogens.

Which cell types express IL23R and how does expression vary in healthy versus disease states?

IL23R is primarily expressed on several immune cell types including T cells (particularly Th17 cells), natural killer (NK) cells, monocytes, and dendritic cells . Human Th17 cells have been identified with a CCR2+CCR5- phenotype that expresses IL23R . Research has demonstrated that human IL23R mRNA is expressed in human Th1 and Th0 clones, NK cell lines, and at lower levels in EBV-transformed B cells and activated peripheral blood mononuclear cells (PBMCs) .

In disease states, the expression pattern can significantly change. Current research gaps include comprehensive assessment of IL23R expression patterns across various cell types and tissues in both healthy and inflamed states . Key questions researchers are investigating include how IL23R expression changes at various timepoints and in different tissue types across immune-mediated inflammatory diseases (IMIDs), and whether IL23R is coexpressed with other molecules of interest that may explain differences between currently available therapies .

Methodologically, techniques such as single-cell RNA sequencing, flow cytometry, and spatial transcriptomics are being employed to create temporal and spatial maps of IL23R expression in different tissues, which is essential for understanding disease mechanisms and developing targeted therapies.

How should researchers properly store and reconstitute IL23R antibodies for experimental use?

For optimal results when working with IL23R antibodies, researchers should follow specific storage and handling protocols. Commercial antibodies such as Human IL-23R Antibody (AF1400) should be stored in a manual defrost freezer, avoiding repeated freeze-thaw cycles that can compromise antibody integrity .

Storage duration recommendations include:

• 12 months from date of receipt at -20 to -70°C as supplied

• 1 month at 2 to 8°C under sterile conditions after reconstitution

• 6 months at -20 to -70°C under sterile conditions after reconstitution

For reconstitution, researchers should use reconstitution calculators provided by manufacturers to determine proper diluent volumes. Optimal antibody dilutions should be determined for each specific application and experimental setup through titration experiments. Technical protocols for applications such as flow cytometry, immunohistochemistry, or Western blotting are typically available from antibody manufacturers .

Which IL23R genetic variants have been linked to autoimmune and inflammatory conditions, and what are their functional consequences?

Several IL23R genetic variants have been associated with autoimmune and inflammatory diseases. Most notably, the R381Q (Arg381Gln) variant appears to be protective against inflammatory conditions such as ankylosing spondylitis . This variant alters a single amino acid in the IL-23 receptor, replacing arginine with glutamine at position 381 .

Functional studies have revealed that the R381Q variant results in reduced STAT3 phosphorylation when cells expressing this variant are stimulated with IL-23, consequently leading to diminished production of pro-inflammatory cytokines and reduced Th17 effector functions . This mechanistic insight explains the protective effect of this variant in inflammatory diseases.

Other IL23R variations appear to increase the risk of developing ankylosing spondylitis, although the specific functional consequences of these risk-associated variants are still being investigated . Researchers examining IL23R variations should employ genetic sequencing, functional assays measuring STAT3/STAT4 phosphorylation, and cytokine production assays to characterize the impact of specific variants.

How does the IL23R R381Q protective variant modify signaling pathways and immune functions?

The R381Q (Arg381Gln) variant of IL23R has been extensively studied as a protective variant against inflammatory diseases. Mechanistically, this variant results in a loss of function, as cells expressing R381Q show reduced levels of phosphorylated STAT3 upon IL-23 stimulation . This reduced STAT3 activation subsequently leads to decreased production of pro-inflammatory cytokines and diminished Th17 cell effector functions .

To investigate STAT activation by IL23R variants experimentally, researchers can co-transfect IL23Rα (wild-type or variant) and IL12Rβ1 into cell lines such as HeLa cells, followed by IL-23 stimulation. Western blotting with antibodies against phosphorylated STAT3 (pSTAT3) or STAT4 (pSTAT4) can then be used to assess pathway activation . Typically, a 1/1000 dilution for pSTAT4 antibodies and a 1/5000 dilution for total STAT4 antibodies are recommended for Western blotting .

The downstream effects of reduced STAT3 activation include decreased expression of IL-17 family cytokines and other Th17-associated molecules, which explains the protective effect against inflammatory conditions where Th17 responses play a pathogenic role.

What approaches should be used to identify novel IL23R variants with potential clinical significance?

To identify novel IL23R variants with potential clinical significance, researchers should employ a comprehensive approach combining genomic analysis with functional validation:

• Genomic analysis:

  • Whole-genome or targeted sequencing of IL23R in diverse patient populations

  • Genome-wide association studies (GWAS) to identify IL23R locus associations

  • Exome sequencing focusing on the IL23R coding regions

• Bioinformatic prediction:

  • Use of algorithms to predict functional consequences of identified variants

  • Conservation analysis across species to identify evolutionarily constrained regions

  • Structural modeling to understand how variants might affect protein function

• Functional validation:

  • Cell-based reporter assays to measure IL-23-dependent STAT activation

  • T-cell differentiation assays to assess impact on Th17 development

  • Cytokine production measurement following IL-23 stimulation

• Clinical correlation:

  • Case-control studies comparing variant frequencies between patients and healthy controls

  • Phenotype-genotype correlation analyses

  • Response to IL-23 pathway-targeted therapies based on genotype

Recent genome-wide studies have identified allelic variants in the HLA-C upstream region that may interact with IL23R signaling, highlighting the need to examine genetic variants beyond the IL23R gene itself . Multiomics approaches combining genomics, transcriptomics, and proteomics data provide more comprehensive insights into how genetic variants influence disease risk through IL23R signaling pathways.

What are the optimal techniques for detecting and quantifying IL23R expression in different tissue and cell types?

Researchers investigating IL23R expression should consider multiple complementary techniques:

• Transcriptional analysis:

  • Quantitative real-time PCR (RT-qPCR) - Gold standard for mRNA quantification with high sensitivity

  • RNA sequencing (RNA-seq) - Provides comprehensive transcriptome analysis

  • Single-cell RNA sequencing - Reveals cell-specific expression patterns within heterogeneous samples

  • Spatial transcriptomics - Maps IL23R expression within tissue architecture

• Protein detection:

  • Flow cytometry - Quantifies IL23R expression at single-cell resolution; useful for immune cell populations

  • Immunohistochemistry/Immunofluorescence - Visualizes IL23R localization in tissue sections

  • Western blotting - Quantifies total IL23R protein levels

  • Mass spectrometry - Provides unbiased proteomic analysis including post-translational modifications

Recent advances in multiomics approaches combine these techniques to provide a more comprehensive view of IL23R expression. For example, single-cell transcriptomics coupled with surface protein detection can identify specific IL23R-expressing cell subsets in complex tissues .

When designing experiments, researchers should consider tissue-specific expression patterns and disease context. For instance, using CCR2 and CCR5 as additional markers can help identify human Th17 cells that express IL23R . Optimal dilutions for antibodies should be determined empirically for each application, with manufacturers typically providing starting recommendations .

How can researchers effectively model IL23R signaling in vitro and what are the key considerations?

Modeling IL23R signaling in vitro requires careful experimental design to recapitulate physiologically relevant conditions:

• Cell systems:

  • Primary human cells (PBMCs, isolated T cells, NK cells) - Provide physiologically relevant context

  • Cell lines transfected with IL23R and IL12Rβ1 - Allow controlled mechanistic studies

  • Induced pluripotent stem cell (iPSC)-derived immune cells - Enable disease-specific modeling

• Signaling readouts:

  • STAT3/STAT4 phosphorylation - Direct measurement of receptor activation

  • Reporter gene assays - Quantitative measurement of pathway activity

  • Transcriptional profiling - Comprehensive analysis of downstream effects

  • Cytokine production - Functional outcome of signaling

For examining STAT activation specifically, co-transfection of IL23Rα and IL12Rβ1 into cell lines followed by IL-23 stimulation is an established approach. Western blotting can then be performed using antibodies against phosphorylated STAT3 or STAT4 to assess pathway activation .

Key considerations include:

• The need for both IL23R and IL12Rβ1 subunits for functional signaling

• Concentration and timing of IL-23 stimulation

• Potential differences between human and mouse IL23R signaling (66% amino acid sequence identity)

• The importance of using human cells or tissues to ensure relevance to human disease

• Cell type-specific differences in signaling outcomes

What experimental approaches can distinguish IL23R-specific effects from other IL-12 family receptor signaling pathways?

Distinguishing IL23R-specific effects from other IL-12 family receptor signaling pathways requires strategic experimental approaches:

• Receptor-specific tools:

  • IL23R-specific monoclonal antibodies that do not cross-react with IL-12Rβ2

  • siRNA or CRISPR-mediated selective knockout of IL23R

  • IL-23p19-specific neutralizing antibodies (targeting the unique subunit of IL-23)

  • Recombinant expression of IL23R with mutations in specific signaling domains

• Comparative analysis:

  • Parallel stimulation with IL-23 versus IL-12 to compare signaling outputs

  • Analysis of cell types expressing IL23R but not IL-12Rβ2

  • Temporal analysis of signaling kinetics, which may differ between pathways

• Downstream signaling discrimination:

  • Although both IL-23 and IL-12 activate JAK-STAT pathways, IL-23 preferentially activates STAT3, while IL-12 primarily activates STAT4

  • Specific transcriptional profiles can be identified that distinguish IL-23 versus IL-12 signaling

• Genetic approaches:

  • Using cells from individuals with IL23R variants (like R381Q) that specifically impact IL-23 but not IL-12 signaling

  • Selective reconstitution of IL23R-deficient cells with wild-type or mutant receptors

Understanding structural differences between IL23R and IL-12Rβ2, such as IL23R lacking the three extracellular membrane-proximal fibronectin-type III domains present on IL-12Rβ2 , can inform the design of specific inhibitors or experimental tools.

How does IL23R signaling contribute to the pathogenesis of different inflammatory and autoimmune diseases?

IL23R signaling plays distinct roles in various inflammatory and autoimmune diseases:

• Psoriasis and psoriatic arthritis:

  • IL-23/IL-23R signaling promotes differentiation and maintenance of pathogenic Th17 cells

  • These cells produce IL-17A, IL-17F, IL-22 and other inflammatory mediators that drive keratinocyte hyperproliferation and joint inflammation

  • IL-23 blockade is highly effective in these conditions, confirming the central role of this pathway

• Inflammatory bowel diseases (IBD):

  • IL23R variants are associated with altered risk of Crohn's disease

  • IL-23 signaling influences intestinal Th17 responses and tissue-resident memory T cells

  • Interaction between gut microbiota and IL-23 signaling appears crucial in disease pathogenesis

• Ankylosing spondylitis:

  • Several IL23R polymorphisms influence disease risk

  • IL-23 signaling promotes inflammation at the entheses (tendon-bone attachments)

  • The protective R381Q variant reduces risk through decreased STAT3 activation

The specific contribution of IL23R signaling may vary across diseases due to:

• Tissue-specific microenvironments influencing IL-23 production

• Different cellular targets of IL-23 in various tissues

• Interaction with other inflammatory pathways

• Genetic background of affected individuals

Understanding these disease-specific mechanisms requires integrated analysis of genetic, transcriptomic, and functional data from patient samples .

What is known about the relationship between IL23R expression and cellular senescence in age-related pathologies?

Recent research has identified IL23R as a senescence-linked circulating and tissue biomarker, suggesting a previously unrecognized role in age-related pathologies . Studies in mice have demonstrated that IL23R levels increase with age and can be reversed by senotherapeutic interventions that target senescent cells .

Key findings include:

• IL23R plasma levels increase with age in both mice and humans

• Senolytic drugs (venetoclax, navitoclax, fisetin, luteolin) and transgenic senescent cell clearance reversed age-dependent increases in plasma IL23R in mice

• Changes in circulating IL23R correspond to expression differences in tissues, particularly in the kidney

These discoveries suggest IL23R may serve as:

• A biomarker of systemic senescent cell burden

• A potential mediator of senescence-associated interorgan signal transduction

• A translational biomarker for monitoring responses to senotherapeutic interventions

Research methodologies to study this relationship include:

• Comparison of IL23R levels in young versus aged tissues

• Analysis of IL23R expression in senescent cells identified by p16 or other senescence markers

• Examination of IL23R changes following senolytic treatment

• Correlation of IL23R levels with other markers of biological aging

This emerging area represents an important intersection between immune signaling and fundamental aging mechanisms, with potential implications for age-related inflammatory conditions.

What are the current gaps in understanding the tissue-specific roles of IL23R in different disease states?

Despite significant advances, several critical gaps remain in understanding tissue-specific roles of IL23R in different disease states:

• Cell type specificity:

  • Comprehensive identification of IL23R-expressing cells in different tissues remains incomplete

  • The role of IL23R on non-immune cells requires further investigation

  • Single-cell and spatial transcriptomics approaches are needed to map IL23R expression at high resolution

• Signaling nuances:

  • Whether IL23R signaling differs among cell types or tissues with functional consequences for disease pathogenesis

  • How signaling patterns change during disease progression

  • The specific roles of STAT3 versus STAT4 signaling downstream of IL23R in different contexts

• Regulatory mechanisms:

  • The role of IL23R signaling in regulatory T cells versus effector T cells

  • How tissue-specific microbiota influence IL23R expression and signaling

  • Epigenetic regulation of IL23R expression in different tissues

• Therapeutic implications:

  • Molecular basis for inadequate response to IL-23 inhibition in some cases

  • Identification of biomarkers that predict response to IL-23 pathway-targeted therapies

  • Potential for tissue-specific targeting of the IL-23 pathway

Researchers are encouraged to employ multiomics approaches to address these gaps, including comprehensive studies to identify the spectrum of IL23R-expressing cells and provide insights into the role of IL-23 in driving immune-mediated inflammatory diseases .

How do different therapeutic approaches targeting the IL-23 pathway compare in efficacy and mechanism of action?

Therapeutic approaches targeting the IL-23 pathway can be categorized based on their molecular targets and mechanisms:

• IL-23p19 subunit-specific antibodies:

  • Selectively target the unique p19 subunit of IL-23 without affecting IL-12

  • Examples include guselkumab, risankizumab, and tildrakizumab

  • Highly effective in psoriasis and being evaluated in other inflammatory conditions

  • Provide more selective inhibition than earlier-generation therapies

• IL-12/23 p40 subunit antibodies:

  • Target the shared p40 subunit, inhibiting both IL-12 and IL-23

  • Example: ustekinumab

  • Effective in psoriasis, psoriatic arthritis, and Crohn's disease

  • Broader mechanism potentially impacts both Th1 (via IL-12) and Th17 (via IL-23) responses

• IL-23 receptor antagonists:

  • Directly block receptor binding

  • Currently in preclinical/early clinical development

  • Potential for selective blockade of IL-23 signaling

• Downstream pathway inhibitors:

  • JAK inhibitors can affect IL-23 signaling among other cytokine pathways

  • Less selective but may address multiple inflammatory pathways simultaneously

Comparative efficacy considerations:

• Direct IL-23 inhibition may have broader utility than targeting downstream effectors like IL-17 due to the functional redundancy of IL-17 family cytokines

• Not all inflammatory diseases in which IL-17A or IL-17F are pathogenic drivers are necessarily IL-23-dependent (e.g., hidradenitis suppurativa)

• Understanding the effect of IL-23 on diverse T-cell targets in patients is crucial for predicting therapeutic responses

What techniques can researchers use to assess IL23R expression and function as potential biomarkers for therapeutic response?

Researchers can employ several techniques to assess IL23R as a potential biomarker for therapeutic response:

• Genetic biomarkers:

  • Genotyping of IL23R variants (e.g., R381Q) that may predict response

  • Next-generation sequencing to identify novel variants

  • Analysis of epigenetic modifications of the IL23R gene

• Protein expression biomarkers:

  • Flow cytometry to quantify IL23R surface expression on immune cell subsets

  • Mass cytometry (CyTOF) for high-dimensional phenotyping of IL23R+ cells

  • Immunohistochemistry to assess tissue expression patterns

  • ELISA or Luminex assays for soluble IL23R in serum/plasma

• Functional biomarkers:

  • Ex vivo IL-23 stimulation assays measuring STAT3 phosphorylation

  • Analysis of IL-17 and other downstream cytokine production

  • Gene expression profiling of IL-23 responsive genes

• Multiomics approaches:

  • Integration of transcriptomic, proteomic, and metabolomic data

  • Single-cell RNA sequencing before and after therapy to identify responsive cell populations

  • Spatial transcriptomics to map tissue-specific changes in IL23R pathway activity

When developing IL23R-based biomarkers, researchers should consider:

• Analysis of biomarker profiles between inadequate responders and responders to predict clinical outcomes

• Investigating how IL23R expression changes over time during disease progression and treatment

• Determining whether IL23R is coexpressed with other molecules that may influence therapeutic response

• Examining the role of tissue-resident memory T cells (TRM) as these may be particularly affected by IL-23 targeting and influence durability of response

What are the key considerations for developing next-generation therapeutics targeting the IL-23/IL-23R pathway?

Development of next-generation therapeutics targeting the IL-23/IL-23R pathway should address several key considerations:

• Target specificity and selectivity:

  • Selective targeting of specific IL23R domains or signaling components

  • Development of bispecific antibodies targeting IL23R and complementary pathways

  • Small molecule inhibitors of IL23R signaling with improved tissue penetration

• Precision medicine approaches:

  • Stratification of patients based on IL23R variants or expression patterns

  • Companion diagnostics to identify likely responders

  • Combination therapies tailored to individual disease mechanisms

• Tissue targeting strategies:

  • Local delivery systems for tissue-specific IL-23 inhibition

  • Targeting tissue-resident IL23R-expressing cells

  • Understanding the effect of IL-23p19 targeting on tissue-resident memory T cells (TRM)

• Research priorities for advancing therapeutic development:

  • Identifying trends in how the IL-23/IL-17 axis functions in different cell types or tissues

  • Determining whether the impact of this pathway changes over disease progression

  • Understanding post-translational modifications of downstream effector molecules associated with IL-23 signaling

  • Investigating how the tissue microbiome influences IL-23 pathway activity

• Addressing durability of response:

  • Examining the effect of targeting IL-23p19 on TRM cells and the ratio of TRM/Treg cells across immune-mediated inflammatory diseases

  • Understanding mechanisms of secondary non-response

  • Developing biomarkers for long-term efficacy prediction

These considerations emphasize the need for continued basic and translational research to refine our understanding of IL-23 biology while advancing clinical applications of IL-23 pathway-targeted therapies.