Transmembrane signal transduction

Abstract

In biological cells, information from the external environment of the cell is used to make survival related decisions. For these decisions, it is important that signals are accurately transduced from the outside to the inside of the cell. In \textit{Dictyostelium discoideum}, two opposing mechanisms using G-protein coupled receptors are used for this signalling: the precoupling mechanism, where second messenger molecules bind to the receptor before a ligand binds to it, and the collision coupling mechanism, in which the ligand binding comes first. In this paper, we investigated both models by analyzing how accurately they detect ligand bindings when different receptors are able to interact with each other. A similar analysis is done for returning messenger molecules. We found that the influence of receptors upon each other is low if the receptors operate under the same conditions. However, when the conditions are heterogeneous, the influence of receptors on each other is huge. The main reason for this influence is that ligand binding receptors which are more likely to get detected by messenger molecules will receive more of those messengers, because of their high diffusion rate. The effect of returning messenger molecules on the receptor signal was that ligand detection became possible at times where they otherwise would not be able to be detected anymore, given a replace rate which is low compared to the rate of binding and unbinding of a ligand to a receptor.