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Interactions between anti-ErbB2 antibody A21 and the ErbB2 extracellular domain provide a basis for improving A21
Liang Chang1, Changhai Zhou, Man Xu
1Lab of Cellular and Molecular Immunology, School of Life Sciences, University of Science and Technology of China, 230027 Hefei, People's Republic of China.
Abstract:
Anti-ErbB2 antibodies are well researched for the therapy of ErbB2-overexpressing tumors. The therapeutic potential and efficacy of these antibodies are closely related to their affinities to ErbB2. Previously we reported that an anti-ErbB2 antibody A21 targeting a conformational epitope comprising several loops in ErbB2 extracellular subdomain I and II could inhibit the proliferation of ErbB2-overexpressing cancer cells in vitro and in vivo. Here we found that another structureless and non-conserved loop in subdomain I of ErbB2 extracellular domain (ECD) was important for binding to A21, and then the antigen-contact sites on A21 were determined by site-directed mutation. The loop was constructed by molecular modeling, and a new model of A21-ErbB2 complex was generated by docking using the crystal structure of the scfv A21 and the model of ErbB2 ECD with the loop built. Based on the complex model, computational design for A21 affinity improvement was performed to enhance its affinity to ErbB2. Two mutants with about 1.7-fold improvement in affinity were obtained. Our study provided a rational molecular basis for affinity improvement and mechanism investigation of A21.
Insights
Researchers enhanced an anti-ErbB2 antibody (A21) for cancer therapy. By understanding its binding to ErbB2, they improved antibody affinity, offering a new strategy for treating ErbB2-overexpressing tumors.
Area of Science:
- Immunology
- Molecular Biology
- Biochemistry
Background:
- Anti-ErbB2 antibodies are crucial for treating ErbB2-overexpressing cancers.
- Antibody affinity to ErbB2 directly impacts therapeutic efficacy.
- Previous work identified antibody A21 targeting conformational epitopes in ErbB2.
Purpose of the Study:
- To investigate the role of a specific ErbB2 loop in A21 binding.
- To determine antigen-contact sites on A21.
- To computationally design and improve A21's affinity for ErbB2.
Main Methods:
- Site-directed mutagenesis to identify A21 antigen-contact sites.
- Molecular modeling to construct an ErbB2 extracellular domain loop.
- Computational docking to generate an A21-ErbB2 complex model.
- Computational design for affinity enhancement.
Main Results:
- A structureless loop in ErbB2 subdomain I is critical for A21 binding.
- Antigen-contact sites on A21 were identified.
- Two A21 mutants with approximately 1.7-fold increased affinity to ErbB2 were generated.
Conclusions:
- A detailed molecular understanding of A21-ErbB2 interaction was achieved.
- The study provides a rational basis for improving anti-ErbB2 antibody affinity.
- This work facilitates further investigation into A21's therapeutic mechanisms.
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