CD122 protein: the shared receptor subunit of IL-2/IL-15 and a core target for biased immunotherapy

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This article focuses on the molecular characteristics and signal transduction functions of the interleukin-2 receptor β subunit (CD122), systematically elaborating the molecular mechanisms by which it, as a shared subunit of IL-2R and IL-15R, mediates JAK-STAT signal transduction through the formation of dimeric or trimeric receptor complexes, analyzing the differential roles of CD122 in the proliferation regulation of CD8-positive T cells, NK cells, and regulatory T cells, and exploring the precision strategies and clinical value of CD122-biased IL-2 agonists in tumor immunotherapy.

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CD122 Protein: The Shared IL-2/IL-15 Receptor Subunit and a Core Target for Biased Immunotherapy

Brief Introduction: This article focuses on the molecular characteristics and signal transduction functions of the interleukin-2 receptor β subunit (CD122), systematically elaborating the molecular mechanism by which it, as a shared subunit of IL-2R and IL-15R, mediates JAK-STAT signal transduction through the formation of dimeric or trimeric receptor complexes, analyzing the differential roles of CD122 in regulating the proliferation of CD8-positive T cells, NK cells, and regulatory T cells, and discussing the precision strategies and clinical value of CD122-biased IL-2 agonists in tumor immunotherapy.

I. Research Background of Tumor Immunotherapy and the IL-2 Signaling System.

In recent years, the popularity of tumor immunotherapy has been evident to all, and it mainly relies on activating immune cells in the body to achieve the effect of killing or inhibiting tumors. Interleukin-2 is one of many cell growth factors, and binding to its receptor can stimulate the proliferation of CD8-positive T cells, NK cells, and regulatory T cells. NKTR-214, developed by Nektar, is a CD122-biased agonist that can selectively activate cancer-killing T cells and NK cells. It is currently known that NKTR-214 combined with PD-1/PD-L1 inhibitors against melanoma, renal cell carcinoma, non-small cell lung cancer, and other cancers can significantly improve the objective response rate of patients. Interleukin-2 is a type of interleukin that plays an important role in the body's immune system and is mainly responsible for regulating the immune activity of leukocytes. IL-2 exerts its effects by binding to IL-2 receptors on the surface of lymphocytes. The interleukin-2 receptor consists of three chains, α, β, and γ, and is mainly expressed on the surface of T cells, regulating the body's immune function by inducing T cell activation.

II. The Dual Nature of the IL-2 Signaling System and the Differential Regulation of CD122.

Although IL-2 can activate the proliferation of killer immune cells, it also stimulates the proliferation of regulatory T cells, which themselves have immunosuppressive effects. This dual nature constitutes a long-standing dilemma in the clinical application of IL-2——while enhancing anti-tumor immunity, the expansion of Tregs may instead suppress immune responses and limit efficacy. The key to resolving this dilemma lies in understanding the differential signals mediated by different subunit combinations of the IL-2 receptor. IL-2Rβ (CD122) is the β subunit shared by the interleukin-2 receptor and the IL-15 receptor, forming an intermediate-affinity dimeric receptor with IL-2Rγ (CD132), or a high-affinity trimeric receptor with CD25 (IL-2Rα) and CD132, thereby mediating the transduction of IL-2 and IL-15 signals through the JAK-STAT pathway. The differences between dimeric and trimeric receptors in cellular distribution and signal strength are precisely the molecular basis for the selective activation achieved by CD122-biased agonists.

III. Molecular Characteristics and Signal Transduction Mechanisms of CD122.

As the shared β subunit of IL-2R and IL-15R, CD122 has a molecular structure that includes an extracellular ligand-binding domain, a single transmembrane region, and an intracellular signal transduction domain. The intracellular domain constitutively associates with JAK1 kinase; when a ligand binds to the receptor complex, JAK1 is activated and phosphorylates tyrosine residues in the intracellular domain of the receptor, providing docking sites for STAT3 and STAT5. Phosphorylated STAT proteins form dimers, translocate to the nucleus, and initiate transcription of target genes. CD122 plays a core role in regulating the development, proliferation, survival, and differentiation of lymphocytes (such as T cells and NK cells), particularly affecting the maintenance of CD8-positive T memory cells, the generation of invariant natural killer T cells, and thymocyte development. These functions make CD122 a key signaling node connecting innate and adaptive immunity.

IV. Clinical Relevance and Disease Associations of CD122.

Clinically, CD122 gene mutations may lead to severe immune dysregulation and peripheral tolerance defects, while abnormal expression is closely associated with ANCA-associated vasculitis, systemic lupus erythematosus, inflammatory bowel disease, and immune dysfunction in HBV/HCV infection. These disease associations indicate that CD122 is not only a core molecule in the development and functional regulation of immune cells but also a potential biomarker and therapeutic target for various immune dysregulation disorders. In autoimmune diseases, abnormal signaling pathways mediated by CD122 may be involved in the activation of autoreactive T cells and tissue damage; in chronic viral infections, dysregulated CD122 expression may be associated with T cell exhaustion and persistent viral infection.

V. Precision Therapeutic Strategies of CD122-Biased IL-2 Agonists.

In recent years, CD122-biased IL-2 agonists have become a hotspot in cancer immunotherapy, selectively binding to the CD122/CD132 dimer, preferentially activating CD8-positive T cells and NK cells while reducing regulatory T cell-mediated immunosuppression, thereby providing new precision therapeutic strategies for cancer and autoimmune diseases. The core logic of this strategy lies in exploiting the differences in receptor subunit combinations——CD8-positive T cells and NK cells mainly express the CD122/CD132 dimer, whereas Tregs highly express CD25 and rely on the CD25/CD122/CD132 trimer to obtain high-affinity IL-2 signals. CD122-biased agonists, by selectively binding to the dimer, preferentially activate killer immune cells while relatively avoiding Treg expansion, thereby enhancing anti-tumor immunity while alleviating immunosuppression. This design concept represents a paradigm shift in cytokine therapy from "broad-spectrum activation" to "precision bias."

VI. Conclusion.

In basic research and drug development related to CD122, high-quality recombinant CD122 protein is a core tool for elucidating its ligand-binding mechanisms with IL-2 and IL-15 and for evaluating the activity of biased agonists. The His tag facilitates purification by immobilized metal affinity chromatography and enables detection and capture via anti-His tag antibodies. To meet the needs of CD122 functional research and the exploration of biased immunotherapy strategies, U-protein offers IL-2 R beta/CD122 His Tag Protein, Human. This product is suitable for applications including binding activity analysis of CD122 with IL-2 and IL-15 ligands, in vitro screening and evaluation of CD122-biased agonists, CD122/CD132 dimer assembly and JAK-STAT signaling pathway mechanistic studies, as well as research related to tumor immunotherapy and autoimmune diseases.

This article is reviewed and published by the technical expert team of UA

Disclaimer: This article partially utilizes artificial intelligence assistance in its creation. If any content involves copyright or intellectual property issues, please let us know and we promise to verify and remove it as soon as possible.

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