Identification of Optimality and Robustness in Dictyostelium External Signal Receptors

Robust optimal performance of ligand and receptor interaction networks in cellular systems is essential in order for organisms to react appropriately to external stimulation. Recent studies have proposed that certain generic structural properties are highly conserved among the many different types of ligand/receptor interaction networks found in nature. In this paper, we show that the ligand/receptor interaction network employed to relay external cAMP signals in aggregating Dictyostelium discoideum cells exhibits such generic structural characteristics. We also show that the network parameters for the ligand bound cell receptors which are distributed on the outer shell of Dictyostelium discoideum cells are highly optimised, in the sense that the response speed is the fastest possible while ensuring that no overshoot occurs for step changes in external signals. Finally, we show that the response of the network to external signals is extremely robust to variations in the relevant kinetic parameters of the network, the cell volume and the number of receptors present on the surface of the cell.