12th European Conference on Mathematical and Theoretical Biology - ECMTB 2022, Heidelberg (Germany). 19-23 September 2022
Summary:
While B-cell receptors (BCRs) interact with their cognate antigen (Ag) in the context of a membrane-membrane interaction, and therefore in 2D conditions, their soluble counterpart, antibodies (Abs), in-teract with antigens in 3D conditions. Due to this difference in dimensionality, the effective kinetic rate and affinity constants of Ab-Ag interactions have been widely described with multiple techniques, partic-ularly the Surface-Plasmon Resonance, while BCR-Ag constants have only been measured for a couple of Abs[1]. Traditionally it has been implicitly assumed that Ab-Ag interactions are a good proxy for BCR-Ag interactions. Moreover, the translational on and off kinetic rates scale similarly to each other from 2D to 3D conditions[2]. However, whether the corresponding rotational on and off kinetic rates also scale similarly to each other from 2D to 3D conditions it is presently unknown.
Here we performed a detailed analysis of BCR and Ab rotational rates in 2D and 3D conditions using the theory of stochastic narrow escape and first passage processes[3], and combined analytical calculations with Brownian simulations. Our results show that the effective on and off kinetic rates of the Ig rotational diffusion process strongly depend on the physical conditions of the interactions (free antibodies and antigens vs BCRs and membrane-anchored antigens) and on the flexibility and angle span between Fab arms of different Ig isotypes. This implies that, contrary to the traditional implicit assumption, the kinetics of BCR-Ag interactions cannot be inferred, in general, from those of Ab-Ag interactions.
Spanish layman's summary:
Los anticuerpos son receptores de célula B secretados. Los primeros se encuentran en disolución y los segundos en la membrana celular. Mediante simulaciones de Monte-Carlo y matemática de procesos de primer paso investigamos como afecta esta diferencia a sus cinéticas efectivas de unión a antígeno.
English layman's summary:
Antibodies are secreted B-cell receptors. The former are in solution, while the latter are on the cell membrane. Through Monte-Carlo simulation and first passage processes’ mathematics, we study how this difference affects their effective kinetic in the antigen binding process.
Keywords: B-cell receptors, theoretical biology, stochastic processes
Publication date: 2022-09-19.
Citation:
M. García-Sánchez, M. Castro, J. Faro, The rotational diffusion of B-cell receptor vs antibody paratopes differentially affects their antigen binding kinetics, 12th European Conference on Mathematical and Theoretical Biology - ECMTB 2022, Heidelberg (Germany). 19-23 September 2022.
