Amplifying signals by putting incorrect ligand molecules in the system

Yan-Ru Chen^1*, Hsuan-Yi Chen^1,2

¹Department of Physics, National Central University, Taoyuan city, Taiwan
²Institute of Physics, Academic Sinica, Taipei city, Taiwan

* Presenter:Yan-Ru Chen, email:rubby860729@gmail.com

Detecting and responding to the environment change is necessary for cells or bacterium to live. However, the environment is usually noisy, so how to sense and respond accurately is important. First, the sensory system should respond to the specific ligands instead of the incorrect ones. Also, it should response quickly after detecting the environment change. Finally, it should be sensitive enough so that it can detect weak signals. In this study, we propose a model of a small sensory system that is able to meet the above three goals. Our system is a lattice of receptors. The state of a receptor is specified by its ligand occupancy and activation level. Two neighboring receptors are coupled such that they tend to be in the same ligand occupancy state. This system is distinctly different from the celebrated MWC model or other generalizations which emphasize the coupling of the receptor activities. On the other hand, it is somewhat related to the T cell receptors whose binding state coupling may result from membrane-mediated interactions. We show that in this model, the presence of incorrect ligand molecules do not lead to incorrect signaling thanks to the kinetic proofreading mechanism often found in biological systems. On the other hand, the presence of a correct ligand leads to a prolonged bound-state receptor that can induce the binding of the incorrect ligand molecules in the environment. This gives a significant amplifying effect on the response of the system to a weak signal. This new mechanism may be related to immune response in many organisms, and it also has potential applications in the microscopic molecular detection technologies.

Keywords: cell signaling, kinetic proofreading, chemoreceptor, non-equilibrium statistical mechanics, biological physics