Article

Structural basis for the blockage of IL-2 signaling by therapeutic antibody basiliximab.

State Key Laboratory of Molecular Biology, Research Center for Structural Biology, Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, Shanghai, China.
The Journal of Immunology (Impact Factor: 5.52). 02/2010; 184(3):1361-8. DOI: 10.4049/jimmunol.0903178
Source: PubMed

ABSTRACT IL-2 signaling plays a central role in the initiation and activation of immune responses. Correspondingly, blockage of this pathway leads to inhibition of the immune system and would provide some therapeutic benefits. Basiliximab (Simulect), a therapeutic mAb drug with specificity against IL-2R alpha of T cells, was approved by U.S. Food and Drug Administration in 1998. It has been proven to be effective in the suppression of the IL-2 pathway and hence has been widely used to prevent allograft rejection in organ transplantation, especially in kidney transplants. In this study, we report the crystal structure of the basiliximab Fab in complex with the ectodomain of IL-2R alpha at 2.9 A resolution. In the complex structure, the Fab interacts with IL-2R alpha with extensive hydrophobic and hydrophilic interactions, accounting for a high binding affinity of 0.14 nM. The Ag binding site of basiliximab consists of all six CDR loops that form a large binding interface with a central shallow hydrophobic groove surrounded by four hydrophilic patches. The discontinuous epitope is composed of several segments from the D1 domain and a minor segment from the D2 domain that overlap with most of the regions responsible for the interactions with IL-2. Thus, basiliximab binding can completely block the interactions of IL-2 with IL-2R alpha and hence inhibit the activation of the IL-2 signal pathway. The structural results also provide important implications for the development of improved and new IL-2R alpha-targeted mAb drugs.

0 Bookmarks
 · 
100 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Myasthenia gravis is very rare autoimmune disease of neuromuscular junction, which presents as a weakness and increased fatiquability of striated muscles. Formerly, myasthenia was largely constraining disease and often ended by death. Recently, advanced diagnostic methods and variety of therapeutic options allow the full compensation of the disease and the quality of patient life is restored. In this review, the methods used during the myasthenia treatment along with the description of the disease itself were detailed.
    Ceská a Slovenská farmacie: casopis Ceské farmaceutické spolecnosti a Slovenské farmaceutické spolecnosti 04/2011; 60(2):47-53.
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Interleukin-2 (IL)-2 signaling plays a pivotal role in the activation of immune responses, and drugs that block this pathway have been shown to be effective for the immunosuppression in patients with organ transplantation to alleviate/eliminate allograft rejection. The first humanized monoclonal antibody (mAb) daclizumab falls into this category and shows high specificity and affinity against a key component of the IL-2 receptor complex, namely IL-2Rα. To reveal the molecular mechanism of the inhibition of the IL-2 signaling pathway by daclizumab, we determined the crystal structures of the daclizumab Fab in free form and in complex with the IL-2Rα ectodomain at 2.6 and 2.8 Å resolution, respectively. The daclizumab Fab adopts a similar conformation in the presence or absence of the IL-2Rα ectodomain. The antigen-binding site of daclizumab is mainly composed of five complementarity determining regions (CDRs) that form a large positively charged surface depression and two flanking patches that are generally hydrophobic. The conformational epitope consists of several discontinuous segments of the IL-2Rα ectodomain, a large portion of which overlaps with the regions that interact with IL-2, suggesting that the binding of daclizumab to IL-2Rα would prevent the IL-2 binding to IL-2Rα and the subsequent formation of the IL-2/IL-2Rαβγ(c) complex, and therefore block the IL-2 signaling pathway. These results also have implications for the design and development of improved mAb drugs targeting IL-2Rα.
    Cell Research 12/2010; 20(12):1361-71. · 10.53 Impact Factor
  • Transplantation 04/2011; 91(8):e59-61. · 3.78 Impact Factor

Full-text (2 Sources)

View
12 Downloads
Available from
May 29, 2014